|
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@@ -356,8 +356,8 @@ The <code> <span class='ectt-1000'>cleanup_module()</span>
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</code> function is supposed to undo whatever
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<code> <span class='ectt-1000'>init_module()</span>
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</code> did, so the module can be unloaded safely.
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-</p><!-- l. 272 --><p class='indent'> Lastly, every kernel module needs to include <span class='obeylines-h'><span class='verb'><span class='ectt-1000'>linux/module.h</span></span></span>. We
|
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-needed to include <span class='obeylines-h'><span class='verb'><span class='ectt-1000'>linux/kernel.h</span></span></span> only for the macro expansion for the
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+</p><!-- l. 272 --><p class='indent'> Lastly, every kernel module needs to include <span class='obeylines-h'><span class='verb'><span class='ectt-1000'><linux/module.h></span></span></span>. We
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+needed to include <span class='obeylines-h'><span class='verb'><span class='ectt-1000'><linux/kernel.h></span></span></span> only for the macro expansion for the
|
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<code> <span class='ectt-1000'>pr_alert()</span>
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</code> log level, which you’ll learn about in Section <a href='#x1-120992'>2<!-- tex4ht:ref: sec:printk --></a>.
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</p><!-- l. 276 --><p class='indent'>
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@@ -927,10 +927,12 @@ terms “entry function” and “exit function”, but if I slip and simply ref
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<h4 class='subsectionHead' id='functions-available-to-modules'><span class='titlemark'>0.5.2 </span> <a id='x1-210000.5.2'></a>Functions available to modules</h4>
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<!-- l. 575 --><p class='noindent'>Programmers use functions they do not define all the time. A prime example of this
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is <code> <span class='ectt-1000'>printf()</span>
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-</code>. You use these library functions which are provided by the standard C library, libc.
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-The definitions for these functions do not actually enter your program until the
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-linking stage, which insures that the code (for printf() for example) is available, and
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-fixes the call instruction to point to that code.
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+</code>. You use these library functions which are provided by the standard C
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+library, libc. The definitions for these functions do not actually enter
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+your program until the linking stage, which insures that the code (for
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+<code> <span class='ectt-1000'>printf()</span>
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+</code> for example) is available, and fixes the call instruction to point to that
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+code.
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</p><!-- l. 580 --><p class='indent'> Kernel modules are different here, too. In the hello world
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example, you might have noticed that we used a function,
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<code> <span class='ectt-1000'>pr_info()</span>
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@@ -940,43 +942,51 @@ get resolved upon <code> <span class='ectt-1000'>insmod</span>
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external functions you can use are the ones provided by the kernel. If you’re
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curious about what symbols have been exported by your kernel, take a look at
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<span class='obeylines-h'><span class='verb'><span class='ectt-1000'>/proc/kallsyms</span></span></span>.
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-</p><!-- l. 585 --><p class='indent'> One point to keep in mind is the difference between library functions
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-and system calls. Library functions are higher level, run completely in user
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-space and provide a more convenient interface for the programmer to the
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-functions that do the real work — system calls. System calls run in kernel
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-mode on the user’s behalf and are provided by the kernel itself. The library
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-function printf() may look like a very general printing function, but all it
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-really does is format the data into strings and write the string data using
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-the low-level system call write(), which then sends the data to standard
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-output.
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-</p><!-- l. 589 --><p class='indent'> Would you like to see what system calls are made by printf()? It is easy! Compile
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-the following program:
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+</p><!-- l. 585 --><p class='indent'> One point to keep in mind is the difference between library functions and system
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+calls. Library functions are higher level, run completely in user space and
|
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+provide a more convenient interface for the programmer to the functions
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+that do the real work — system calls. System calls run in kernel mode on
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+the user’s behalf and are provided by the kernel itself. The library function
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+<code> <span class='ectt-1000'>printf()</span>
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+</code> may look like a very general printing function, but all it really does is format the
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+data into strings and write the string data using the low-level system call
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+<code> <span class='ectt-1000'>write()</span>
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+</code>, which then sends the data to standard output.
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+</p><!-- l. 589 --><p class='indent'> Would you like to see what system calls are made by
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+<code> <span class='ectt-1000'>printf()</span>
|
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+</code>? It is easy! Compile the following program:
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</p><!-- l. 1 --><p class='indent'>
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</p>
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- <pre class='fancyvrb' id='fancyvrb30'><a id='x1-21012r1'></a><span class='ecrm-0500'>1</span><span id='textcolor258'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor259'><span class='ectt-0800'><stdio.h></span></span>
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-<a id='x1-21014r2'></a><span class='ecrm-0500'>2</span>
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-<a id='x1-21016r3'></a><span class='ecrm-0500'>3</span><span id='textcolor260'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> main(</span><span id='textcolor261'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
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-<a id='x1-21018r4'></a><span class='ecrm-0500'>4</span><span class='ectt-0800'>{</span>
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-<a id='x1-21020r5'></a><span class='ecrm-0500'>5</span><span class='ectt-0800'> printf(</span><span id='textcolor262'><span class='ectt-0800'>"hello"</span></span><span class='ectt-0800'>);</span>
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-<a id='x1-21022r6'></a><span class='ecrm-0500'>6</span><span class='ectt-0800'> </span><span id='textcolor263'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> 0;</span>
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-<a id='x1-21024r7'></a><span class='ecrm-0500'>7</span><span class='ectt-0800'>}</span></pre>
|
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-<!-- l. 603 --><p class='indent'> with <code> <span class='ectt-1000'>gcc -Wall -o hello hello.c</span>
|
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-</code>. Run the exectable with <code> <span class='ectt-1000'>strace ./hello</span>
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-</code>. Are you impressed? Every line you see corresponds to a system call. <a href='https://strace.io/'>strace</a> is a
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|
|
|
|
|
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+ <pre class='fancyvrb' id='fancyvrb30'><a id='x1-21016r1'></a><span class='ecrm-0500'>1</span><span id='textcolor258'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor259'><span class='ectt-0800'><stdio.h></span></span>
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+<a id='x1-21018r2'></a><span class='ecrm-0500'>2</span>
|
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+<a id='x1-21020r3'></a><span class='ecrm-0500'>3</span><span id='textcolor260'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> main(</span><span id='textcolor261'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
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+<a id='x1-21022r4'></a><span class='ecrm-0500'>4</span><span class='ectt-0800'>{</span>
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+<a id='x1-21024r5'></a><span class='ecrm-0500'>5</span><span class='ectt-0800'> printf(</span><span id='textcolor262'><span class='ectt-0800'>"hello"</span></span><span class='ectt-0800'>);</span>
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|
+<a id='x1-21026r6'></a><span class='ecrm-0500'>6</span><span class='ectt-0800'> </span><span id='textcolor263'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> 0;</span>
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+<a id='x1-21028r7'></a><span class='ecrm-0500'>7</span><span class='ectt-0800'>}</span></pre>
|
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+<!-- l. 603 --><p class='indent'> with <code> <span class='ectt-1000'>gcc -Wall -o hello hello.c</span>
|
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+</code>. Run the exectable with <code> <span class='ectt-1000'>strace ./hello</span>
|
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|
+</code>. Are you impressed? Every line you see corresponds to a system call. <a href='https://strace.io/'>strace</a> is a
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handy program that gives you details about what system calls a program is
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making, including which call is made, what its arguments are and what it
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returns. It is an invaluable tool for figuring out things like what files a program
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|
is trying to access. Towards the end, you will see a line which looks like
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<code> <span class='ectt-1000'>write(1, </span><span id='textcolor264'><span class='ectt-1000'>"hello"</span></span><span class='ectt-1000'>, 5hello)</span>
|
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-</code>. There it is. The face behind the printf() mask. You may not be familiar with write,
|
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-since most people use library functions for file I/O (like fopen, fputs, fclose). If that
|
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-is the case, try looking at man 2 write. The 2nd man section is devoted
|
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-to system calls (like kill() and read()). The 3rd man section is devoted to
|
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|
-library calls, which you would probably be more familiar with (like cosh() and
|
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|
-random()).
|
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|
+</code>. There it is. The face behind the <code> <span class='ectt-1000'>printf()</span>
|
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|
+</code> mask. You may not be familiar with write, since most people use library functions for file
|
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+I/O (like <code> <span class='ectt-1000'>fopen</span>
|
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|
+</code>, <code> <span class='ectt-1000'>fputs</span>
|
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+</code>, <code> <span class='ectt-1000'>fclose</span>
|
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|
+</code>). If that is the case, try looking at man 2 write. The 2nd man section is devoted to system
|
|
|
+calls (like <code> <span class='ectt-1000'>kill()</span>
|
|
|
+</code> and <code> <span class='ectt-1000'>read()</span>
|
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+</code>). The 3rd man section is devoted to library calls, which you would probably be more familiar
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|
|
+with (like <code> <span class='ectt-1000'>cosh()</span>
|
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|
+</code> and <code> <span class='ectt-1000'>random()</span>
|
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|
+</code>).
|
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|
</p><!-- l. 617 --><p class='indent'> You can even write modules to replace the kernel’s system calls, which we will do
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|
shortly. Crackers often make use of this sort of thing for backdoors or trojans, but
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you can write your own modules to do more benign things, like have the kernel
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@@ -999,6 +1009,9 @@ mode”.
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|
</p><!-- l. 630 --><p class='indent'> Recall the discussion about library functions vs system calls. Typically, you use a
|
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|
library function in user mode. The library function calls one or more system calls,
|
|
|
and these system calls execute on the library function’s behalf, but do so in
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+
|
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|
+
|
|
|
+
|
|
|
supervisor mode since they are part of the kernel itself. Once the system call
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completes its task, it returns and execution gets transfered back to user
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|
mode.
|
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|
@@ -1007,9 +1020,6 @@ mode.
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|
<h4 class='subsectionHead' id='name-space'><span class='titlemark'>0.5.4 </span> <a id='x1-230000.5.4'></a>Name Space</h4>
|
|
|
<!-- l. 637 --><p class='noindent'>When you write a small C program, you use variables which are convenient and make
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|
sense to the reader. If, on the other hand, you are writing routines which will be part
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|
-
|
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|
-
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|
-
|
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|
of a bigger problem, any global variables you have are part of a community of other
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peoples’ global variables; some of the variable names can clash. When a program has
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lots of global variables which aren’t meaningful enough to be distinguished, you get
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@@ -1043,6 +1053,9 @@ whatever it needs to be. Since the memory space for any two processes do not
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overlap, every process that can access a memory address, say 0xbffff978, would
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be accessing a different location in real physical memory! The processes
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|
would be accessing an index named 0xbffff978 which points to some kind of
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|
+
|
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|
+
|
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|
+
|
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|
offset into the region of memory set aside for that particular process. For
|
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the most part, a process like our Hello, World program can’t access the
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space of another process, although there are ways which we will talk about
|
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@@ -1053,9 +1066,6 @@ semi-autonomous object), it shares the kernel’s codespace rather than having i
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|
Therefore, if your module segfaults, the kernel segfaults. And if you start writing
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|
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over data because of an off-by-one error, then you’re trampling on kernel
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data (or code). This is even worse than it sounds, so try your best to be
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-
|
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|
-
|
|
|
-
|
|
|
careful.
|
|
|
</p><!-- l. 666 --><p class='indent'> By the way, I would like to point out that the above discussion is true for any
|
|
|
operating system which uses a monolithic kernel. This is not quite the same thing as
|
|
|
@@ -1345,9 +1355,9 @@ is by looking at the 3rd field of <span class='obeylines-h'><span class='verb'><
|
|
|
<code> <span class='ectt-1000'>cleanup_module</span>
|
|
|
</code> because the check will be performed for you by the system call
|
|
|
<code> <span class='ectt-1000'>sys_delete_module</span>
|
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|
-</code>, defined in <span class='obeylines-h'><span class='verb'><span class='ectt-1000'>linux/module.c</span></span></span>. You should not use this counter directly, but there are
|
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-functions defined in <span class='obeylines-h'><span class='verb'><span class='ectt-1000'>linux/module.h</span></span></span> which let you increase, decrease and display
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-this counter:
|
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|
+</code>, defined in <span class='obeylines-h'><span class='verb'><span class='ectt-1000'>include/linux/syscalls.h</span></span></span>. You should not use this counter directly,
|
|
|
+but there are functions defined in <span class='obeylines-h'><span class='verb'><span class='ectt-1000'>include/linux/module.h</span></span></span> which let you increase,
|
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|
+decrease and display this counter:
|
|
|
</p>
|
|
|
<ul class='itemize1'>
|
|
|
<li class='itemize'><code> <span class='ectt-1000'>try_module_get(THIS_MODULE)</span>
|
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|
@@ -2001,36 +2011,47 @@ yourself.
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|
|
<!-- l. 1024 --><p class='noindent'>As we have seen, writing a /proc file may be quite “complex”.
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|
So to help people writting /proc file, there is an API named
|
|
|
<code> <span class='ectt-1000'>seq_file</span>
|
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|
-</code> that helps formating a <span class='obeylines-h'><span class='verb'><span class='ectt-1000'>/proc</span></span></span> file for output. It is based on sequence,
|
|
|
-which is composed of 3 functions: start(), next(), and stop(). The
|
|
|
-<code> <span class='ectt-1000'>seq_file</span>
|
|
|
+</code> that helps formating a <span class='obeylines-h'><span class='verb'><span class='ectt-1000'>/proc</span></span></span> file for output. It is based on sequence, which is composed of
|
|
|
+3 functions: <code> <span class='ectt-1000'>start()</span>
|
|
|
+</code>, <code> <span class='ectt-1000'>next()</span>
|
|
|
+</code>, and <code> <span class='ectt-1000'>stop()</span>
|
|
|
+</code>. The <code> <span class='ectt-1000'>seq_file</span>
|
|
|
</code> API starts a sequence when a user read the /proc file.
|
|
|
-</p><!-- l. 1029 --><p class='indent'> A sequence begins with the call of the function start(). If the return is a non
|
|
|
-NULL value, the function next() is called. This function is an iterator, the goal is to
|
|
|
-go through all the data. Each time next() is called, the function show() is also called.
|
|
|
-It writes data values in the buffer read by the user. The function next() is called until
|
|
|
-it returns NULL. The sequence ends when next() returns NULL, then the function
|
|
|
-stop() is called.
|
|
|
+</p><!-- l. 1029 --><p class='indent'> A sequence begins with the call of the function
|
|
|
+<code> <span class='ectt-1000'>start()</span>
|
|
|
+</code>. If the return is a non NULL value, the function
|
|
|
+<code> <span class='ectt-1000'>next()</span>
|
|
|
+</code> is called. This function is an iterator, the goal is to go through all the data. Each
|
|
|
|
|
|
|
|
|
|
|
|
-</p><!-- l. 1037 --><p class='indent'> BE CAREFUL: when a sequence is finished, another one starts. That means that
|
|
|
-at the end of function stop(), the function start() is called again. This loop finishes
|
|
|
-when the function start() returns NULL. You can see a scheme of this in the
|
|
|
-Figure <a href='#ignorespaces-how-seqfile-works'>1<!-- tex4ht:ref: img:seqfile --></a>.
|
|
|
+time <code> <span class='ectt-1000'>next()</span>
|
|
|
+</code> is called, the function <code> <span class='ectt-1000'>show()</span>
|
|
|
+</code> is also called. It writes data values in the buffer read by the user. The function
|
|
|
+<code> <span class='ectt-1000'>next()</span>
|
|
|
+</code> is called until it returns NULL. The sequence ends when
|
|
|
+<code> <span class='ectt-1000'>next()</span>
|
|
|
+</code> returns NULL, then the function <code> <span class='ectt-1000'>stop()</span>
|
|
|
+</code> is called.
|
|
|
+</p><!-- l. 1037 --><p class='indent'> BE CAREFUL: when a sequence is finished, another one starts. That means that at the end
|
|
|
+of function <code> <span class='ectt-1000'>stop()</span>
|
|
|
+</code>, the function <code> <span class='ectt-1000'>start()</span>
|
|
|
+</code> is called again. This loop finishes when the function
|
|
|
+<code> <span class='ectt-1000'>start()</span>
|
|
|
+</code> returns NULL. You can see a scheme of this in the Figure <a href='#ignorespaces-how-seqfile-works'>1<!-- tex4ht:ref: img:seqfile --></a>.
|
|
|
</p>
|
|
|
<figure class='figure' id='ignorespaces-how-seqfile-works'>
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
-<a id='x1-37003r1'></a>
|
|
|
+<a id='x1-37016r1'></a>
|
|
|
|
|
|
|
|
|
|
|
|
<!-- l. 1044 --><p class='noindent'><img alt='srYrsNNYtaeenetoooertusetupstrxr((ntn))( tis)istrr teeaNreNatUaUtmLtLmeLmLen?e?ntntt ' src='lkmpg-for-ht1x.svg' />
|
|
|
</p>
|
|
|
-<figcaption class='caption'><span class='id'>Figure 1:</span><span class='content'>How seq_file works</span></figcaption><!-- tex4ht:label?: x1-37003r1 -->
|
|
|
+<figcaption class='caption'><span class='id'>Figure 1:</span><span class='content'>How seq_file works</span></figcaption><!-- tex4ht:label?: x1-37016r1 -->
|
|
|
|
|
|
|
|
|
|
|
|
@@ -2042,123 +2063,123 @@ Figure <a href='#ignorespaces-how-seqfile-works'>1<!-- tex4ht:ref: img:seqfile
|
|
|
</code>, and some others. But nothing to write in the /proc file. Of course, you can still use
|
|
|
the same way as in the previous example.
|
|
|
</p>
|
|
|
- <pre class='fancyvrb' id='fancyvrb40'><a id='x1-37009r1'></a><span class='ecrm-0500'>1</span><span id='textcolor803'><span class='ectt-0800'>/*</span></span>
|
|
|
-<a id='x1-37011r2'></a><span class='ecrm-0500'>2</span><span id='textcolor804'><span class='ectt-0800'> * procfs4.c - create a "file" in /proc</span></span>
|
|
|
-<a id='x1-37013r3'></a><span class='ecrm-0500'>3</span><span id='textcolor805'><span class='ectt-0800'> * This program uses the seq_file library to manage the /proc file.</span></span>
|
|
|
-<a id='x1-37015r4'></a><span class='ecrm-0500'>4</span><span id='textcolor806'><span class='ectt-0800'> */</span></span>
|
|
|
-<a id='x1-37017r5'></a><span class='ecrm-0500'>5</span>
|
|
|
-<a id='x1-37019r6'></a><span class='ecrm-0500'>6</span><span id='textcolor807'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor808'><span class='ectt-0800'><linux/kernel.h> /* We are doing kernel work */</span></span>
|
|
|
-<a id='x1-37021r7'></a><span class='ecrm-0500'>7</span><span id='textcolor809'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor810'><span class='ectt-0800'><linux/module.h> /* Specifically, a module */</span></span>
|
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-<a id='x1-37023r8'></a><span class='ecrm-0500'>8</span><span id='textcolor811'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor812'><span class='ectt-0800'><linux/proc_fs.h> /* Necessary because we use proc fs */</span></span>
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-<a id='x1-37025r9'></a><span class='ecrm-0500'>9</span><span id='textcolor813'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor814'><span class='ectt-0800'><linux/seq_file.h> /* for seq_file */</span></span>
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-<a id='x1-37027r10'></a><span class='ecrm-0500'>10</span><span id='textcolor815'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor816'><span class='ectt-0800'><linux/version.h></span></span>
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-<a id='x1-37029r11'></a><span class='ecrm-0500'>11</span>
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-<a id='x1-37031r12'></a><span class='ecrm-0500'>12</span><span id='textcolor817'><span class='ectt-0800'>#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 6, 0)</span></span>
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-<a id='x1-37033r13'></a><span class='ecrm-0500'>13</span><span id='textcolor818'><span class='ectt-0800'>#define HAVE_PROC_OPS</span></span>
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-<a id='x1-37035r14'></a><span class='ecrm-0500'>14</span><span id='textcolor819'><span class='ectt-0800'>#endif</span></span>
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-<a id='x1-37037r15'></a><span class='ecrm-0500'>15</span>
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-<a id='x1-37039r16'></a><span class='ecrm-0500'>16</span><span id='textcolor820'><span class='ectt-0800'>#define PROC_NAME "iter"</span></span>
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-<a id='x1-37041r17'></a><span class='ecrm-0500'>17</span>
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-<a id='x1-37043r18'></a><span class='ecrm-0500'>18</span><span id='textcolor821'><span class='ectt-0800'>/* This function is called at the beginning of a sequence.</span></span>
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-<a id='x1-37045r19'></a><span class='ecrm-0500'>19</span><span id='textcolor822'><span class='ectt-0800'> * ie, when:</span></span>
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-<a id='x1-37047r20'></a><span class='ecrm-0500'>20</span><span id='textcolor823'><span class='ectt-0800'> * - the /proc file is read (first time)</span></span>
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-<a id='x1-37049r21'></a><span class='ecrm-0500'>21</span><span id='textcolor824'><span class='ectt-0800'> * - after the function stop (end of sequence)</span></span>
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-<a id='x1-37051r22'></a><span class='ecrm-0500'>22</span><span id='textcolor825'><span class='ectt-0800'> */</span></span>
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-<a id='x1-37053r23'></a><span class='ecrm-0500'>23</span><span id='textcolor826'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor827'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> *my_seq_start(</span><span id='textcolor828'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> seq_file *s, loff_t *pos)</span>
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-<a id='x1-37055r24'></a><span class='ecrm-0500'>24</span><span class='ectt-0800'>{</span>
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-<a id='x1-37057r25'></a><span class='ecrm-0500'>25</span><span class='ectt-0800'> </span><span id='textcolor829'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor830'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor831'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> counter = 0;</span>
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-<a id='x1-37059r26'></a><span class='ecrm-0500'>26</span>
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-<a id='x1-37061r27'></a><span class='ecrm-0500'>27</span><span class='ectt-0800'> </span><span id='textcolor832'><span class='ectt-0800'>/* beginning a new sequence? */</span></span>
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-<a id='x1-37063r28'></a><span class='ecrm-0500'>28</span><span class='ectt-0800'> </span><span id='textcolor833'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (*pos == 0) {</span>
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-<a id='x1-37065r29'></a><span class='ecrm-0500'>29</span><span class='ectt-0800'> </span><span id='textcolor834'><span class='ectt-0800'>/* yes => return a non null value to begin the sequence */</span></span>
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-<a id='x1-37067r30'></a><span class='ecrm-0500'>30</span><span class='ectt-0800'> </span><span id='textcolor835'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> &counter;</span>
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-<a id='x1-37069r31'></a><span class='ecrm-0500'>31</span><span class='ectt-0800'> }</span>
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-<a id='x1-37071r32'></a><span class='ecrm-0500'>32</span><span class='ectt-0800'> </span><span id='textcolor836'><span class='ectt-0800'>/* no => it is the end of the sequence, return end to stop reading */</span></span>
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-<a id='x1-37073r33'></a><span class='ecrm-0500'>33</span><span class='ectt-0800'> *pos = 0;</span>
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-<a id='x1-37075r34'></a><span class='ecrm-0500'>34</span><span class='ectt-0800'> </span><span id='textcolor837'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> NULL;</span>
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-<a id='x1-37077r35'></a><span class='ecrm-0500'>35</span><span class='ectt-0800'>}</span>
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-<a id='x1-37079r36'></a><span class='ecrm-0500'>36</span>
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-<a id='x1-37081r37'></a><span class='ecrm-0500'>37</span><span id='textcolor838'><span class='ectt-0800'>/* This function is called after the beginning of a sequence.</span></span>
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-<a id='x1-37083r38'></a><span class='ecrm-0500'>38</span><span id='textcolor839'><span class='ectt-0800'> * It is called untill the return is NULL (this ends the sequence).</span></span>
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-<a id='x1-37085r39'></a><span class='ecrm-0500'>39</span><span id='textcolor840'><span class='ectt-0800'> */</span></span>
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-<a id='x1-37087r40'></a><span class='ecrm-0500'>40</span><span id='textcolor841'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor842'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> *my_seq_next(</span><span id='textcolor843'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> seq_file *s, </span><span id='textcolor844'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> *v, loff_t *pos)</span>
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-<a id='x1-37089r41'></a><span class='ecrm-0500'>41</span><span class='ectt-0800'>{</span>
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-<a id='x1-37091r42'></a><span class='ecrm-0500'>42</span><span class='ectt-0800'> </span><span id='textcolor845'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor846'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> *tmp_v = (</span><span id='textcolor847'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor848'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> *) v;</span>
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-<a id='x1-37093r43'></a><span class='ecrm-0500'>43</span><span class='ectt-0800'> (*tmp_v)++;</span>
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-<a id='x1-37095r44'></a><span class='ecrm-0500'>44</span><span class='ectt-0800'> (*pos)++;</span>
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-<a id='x1-37097r45'></a><span class='ecrm-0500'>45</span><span class='ectt-0800'> </span><span id='textcolor849'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> NULL;</span>
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-<a id='x1-37099r46'></a><span class='ecrm-0500'>46</span><span class='ectt-0800'>}</span>
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-<a id='x1-37101r47'></a><span class='ecrm-0500'>47</span>
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-<a id='x1-37103r48'></a><span class='ecrm-0500'>48</span><span id='textcolor850'><span class='ectt-0800'>/* This function is called at the end of a sequence. */</span></span>
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-<a id='x1-37105r49'></a><span class='ecrm-0500'>49</span><span id='textcolor851'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor852'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> my_seq_stop(</span><span id='textcolor853'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> seq_file *s, </span><span id='textcolor854'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> *v)</span>
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-<a id='x1-37107r50'></a><span class='ecrm-0500'>50</span><span class='ectt-0800'>{</span>
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-<a id='x1-37109r51'></a><span class='ecrm-0500'>51</span><span class='ectt-0800'> </span><span id='textcolor855'><span class='ectt-0800'>/* nothing to do, we use a static value in start() */</span></span>
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-<a id='x1-37111r52'></a><span class='ecrm-0500'>52</span><span class='ectt-0800'>}</span>
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-<a id='x1-37113r53'></a><span class='ecrm-0500'>53</span>
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-<a id='x1-37115r54'></a><span class='ecrm-0500'>54</span><span id='textcolor856'><span class='ectt-0800'>/* This function is called for each "step" of a sequence. */</span></span>
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-<a id='x1-37117r55'></a><span class='ecrm-0500'>55</span><span id='textcolor857'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor858'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> my_seq_show(</span><span id='textcolor859'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> seq_file *s, </span><span id='textcolor860'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> *v)</span>
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-<a id='x1-37119r56'></a><span class='ecrm-0500'>56</span><span class='ectt-0800'>{</span>
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-<a id='x1-37121r57'></a><span class='ecrm-0500'>57</span><span class='ectt-0800'> loff_t *spos = (loff_t *) v;</span>
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-<a id='x1-37123r58'></a><span class='ecrm-0500'>58</span>
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-<a id='x1-37125r59'></a><span class='ecrm-0500'>59</span><span class='ectt-0800'> seq_printf(s, </span><span id='textcolor861'><span class='ectt-0800'>"%Ld</span></span><span id='textcolor862'><span class='ectt-0800'>\n</span></span><span id='textcolor863'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, *spos);</span>
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-<a id='x1-37127r60'></a><span class='ecrm-0500'>60</span><span class='ectt-0800'> </span><span id='textcolor864'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> 0;</span>
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-<a id='x1-37129r61'></a><span class='ecrm-0500'>61</span><span class='ectt-0800'>}</span>
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-<a id='x1-37131r62'></a><span class='ecrm-0500'>62</span>
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-<a id='x1-37133r63'></a><span class='ecrm-0500'>63</span><span id='textcolor865'><span class='ectt-0800'>/* This structure gather "function" to manage the sequence */</span></span>
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-<a id='x1-37135r64'></a><span class='ecrm-0500'>64</span><span id='textcolor866'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor867'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> seq_operations my_seq_ops = {</span>
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-<a id='x1-37137r65'></a><span class='ecrm-0500'>65</span><span class='ectt-0800'> .start = my_seq_start,</span>
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-<a id='x1-37139r66'></a><span class='ecrm-0500'>66</span><span class='ectt-0800'> .next = my_seq_next,</span>
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-<a id='x1-37141r67'></a><span class='ecrm-0500'>67</span><span class='ectt-0800'> .stop = my_seq_stop,</span>
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-<a id='x1-37143r68'></a><span class='ecrm-0500'>68</span><span class='ectt-0800'> .show = my_seq_show,</span>
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-<a id='x1-37145r69'></a><span class='ecrm-0500'>69</span><span class='ectt-0800'>};</span>
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-<a id='x1-37147r70'></a><span class='ecrm-0500'>70</span>
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-<a id='x1-37149r71'></a><span class='ecrm-0500'>71</span><span id='textcolor868'><span class='ectt-0800'>/* This function is called when the /proc file is open. */</span></span>
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-<a id='x1-37151r72'></a><span class='ecrm-0500'>72</span><span id='textcolor869'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor870'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> my_open(</span><span id='textcolor871'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> inode *inode, </span><span id='textcolor872'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file *file)</span>
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-<a id='x1-37153r73'></a><span class='ecrm-0500'>73</span><span class='ectt-0800'>{</span>
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-<a id='x1-37155r74'></a><span class='ecrm-0500'>74</span><span class='ectt-0800'> </span><span id='textcolor873'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> seq_open(file, &my_seq_ops);</span>
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-<a id='x1-37157r75'></a><span class='ecrm-0500'>75</span><span class='ectt-0800'>};</span>
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-<a id='x1-37159r76'></a><span class='ecrm-0500'>76</span>
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-<a id='x1-37161r77'></a><span class='ecrm-0500'>77</span><span id='textcolor874'><span class='ectt-0800'>/* This structure gather "function" that manage the /proc file */</span></span>
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-<a id='x1-37163r78'></a><span class='ecrm-0500'>78</span><span id='textcolor875'><span class='ectt-0800'>#ifdef HAVE_PROC_OPS</span></span>
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-<a id='x1-37165r79'></a><span class='ecrm-0500'>79</span><span id='textcolor876'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor877'><span class='ectt-0800'>const</span></span><span class='ectt-0800'> </span><span id='textcolor878'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> proc_ops my_file_ops = {</span>
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-<a id='x1-37167r80'></a><span class='ecrm-0500'>80</span><span class='ectt-0800'> .proc_open = my_open,</span>
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-<a id='x1-37169r81'></a><span class='ecrm-0500'>81</span><span class='ectt-0800'> .proc_read = seq_read,</span>
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-<a id='x1-37171r82'></a><span class='ecrm-0500'>82</span><span class='ectt-0800'> .proc_lseek = seq_lseek,</span>
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-<a id='x1-37173r83'></a><span class='ecrm-0500'>83</span><span class='ectt-0800'> .proc_release = seq_release,</span>
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-<a id='x1-37175r84'></a><span class='ecrm-0500'>84</span><span class='ectt-0800'>};</span>
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-<a id='x1-37177r85'></a><span class='ecrm-0500'>85</span><span id='textcolor879'><span class='ectt-0800'>#else</span></span>
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-<a id='x1-37179r86'></a><span class='ecrm-0500'>86</span><span id='textcolor880'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor881'><span class='ectt-0800'>const</span></span><span class='ectt-0800'> </span><span id='textcolor882'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file_operations my_file_ops = {</span>
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-<a id='x1-37181r87'></a><span class='ecrm-0500'>87</span><span class='ectt-0800'> .open = my_open,</span>
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-<a id='x1-37183r88'></a><span class='ecrm-0500'>88</span><span class='ectt-0800'> .read = seq_read,</span>
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-<a id='x1-37185r89'></a><span class='ecrm-0500'>89</span><span class='ectt-0800'> .llseek = seq_lseek,</span>
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-<a id='x1-37187r90'></a><span class='ecrm-0500'>90</span><span class='ectt-0800'> .release = seq_release,</span>
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-<a id='x1-37189r91'></a><span class='ecrm-0500'>91</span><span class='ectt-0800'>};</span>
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-<a id='x1-37191r92'></a><span class='ecrm-0500'>92</span><span id='textcolor883'><span class='ectt-0800'>#endif</span></span>
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-<a id='x1-37193r93'></a><span class='ecrm-0500'>93</span>
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-<a id='x1-37195r94'></a><span class='ecrm-0500'>94</span><span id='textcolor884'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor885'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> __init procfs4_init(</span><span id='textcolor886'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
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-<a id='x1-37197r95'></a><span class='ecrm-0500'>95</span><span class='ectt-0800'>{</span>
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|
-<a id='x1-37199r96'></a><span class='ecrm-0500'>96</span><span class='ectt-0800'> </span><span id='textcolor887'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> proc_dir_entry *entry;</span>
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-<a id='x1-37201r97'></a><span class='ecrm-0500'>97</span>
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|
-<a id='x1-37203r98'></a><span class='ecrm-0500'>98</span><span class='ectt-0800'> entry = proc_create(PROC_NAME, 0, NULL, &my_file_ops);</span>
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-<a id='x1-37205r99'></a><span class='ecrm-0500'>99</span><span class='ectt-0800'> </span><span id='textcolor888'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (entry == NULL) {</span>
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-<a id='x1-37207r100'></a><span class='ecrm-0500'>100</span><span class='ectt-0800'> remove_proc_entry(PROC_NAME, NULL);</span>
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|
-<a id='x1-37209r101'></a><span class='ecrm-0500'>101</span><span class='ectt-0800'> pr_debug(</span><span id='textcolor889'><span class='ectt-0800'>"Error: Could not initialize /proc/%s</span></span><span id='textcolor890'><span class='ectt-0800'>\n</span></span><span id='textcolor891'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, PROC_NAME);</span>
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-<a id='x1-37211r102'></a><span class='ecrm-0500'>102</span><span class='ectt-0800'> </span><span id='textcolor892'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> -ENOMEM;</span>
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-<a id='x1-37213r103'></a><span class='ecrm-0500'>103</span><span class='ectt-0800'> }</span>
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|
-<a id='x1-37215r104'></a><span class='ecrm-0500'>104</span>
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|
-<a id='x1-37217r105'></a><span class='ecrm-0500'>105</span><span class='ectt-0800'> </span><span id='textcolor893'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> 0;</span>
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-<a id='x1-37219r106'></a><span class='ecrm-0500'>106</span><span class='ectt-0800'>}</span>
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|
-<a id='x1-37221r107'></a><span class='ecrm-0500'>107</span>
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|
-<a id='x1-37223r108'></a><span class='ecrm-0500'>108</span><span id='textcolor894'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor895'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> __exit procfs4_exit(</span><span id='textcolor896'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
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-<a id='x1-37225r109'></a><span class='ecrm-0500'>109</span><span class='ectt-0800'>{</span>
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|
-<a id='x1-37227r110'></a><span class='ecrm-0500'>110</span><span class='ectt-0800'> remove_proc_entry(PROC_NAME, NULL);</span>
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-<a id='x1-37229r111'></a><span class='ecrm-0500'>111</span><span class='ectt-0800'> pr_debug(</span><span id='textcolor897'><span class='ectt-0800'>"/proc/%s removed</span></span><span id='textcolor898'><span class='ectt-0800'>\n</span></span><span id='textcolor899'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, PROC_NAME);</span>
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-<a id='x1-37231r112'></a><span class='ecrm-0500'>112</span><span class='ectt-0800'>}</span>
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-<a id='x1-37233r113'></a><span class='ecrm-0500'>113</span>
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-<a id='x1-37235r114'></a><span class='ecrm-0500'>114</span><span class='ectt-0800'>module_init(procfs4_init);</span>
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-<a id='x1-37237r115'></a><span class='ecrm-0500'>115</span><span class='ectt-0800'>module_exit(procfs4_exit);</span>
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-<a id='x1-37239r116'></a><span class='ecrm-0500'>116</span>
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-<a id='x1-37241r117'></a><span class='ecrm-0500'>117</span><span class='ectt-0800'>MODULE_LICENSE(</span><span id='textcolor900'><span class='ectt-0800'>"GPL"</span></span><span class='ectt-0800'>);</span></pre>
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+ <pre class='fancyvrb' id='fancyvrb40'><a id='x1-37022r1'></a><span class='ecrm-0500'>1</span><span id='textcolor803'><span class='ectt-0800'>/*</span></span>
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+<a id='x1-37024r2'></a><span class='ecrm-0500'>2</span><span id='textcolor804'><span class='ectt-0800'> * procfs4.c - create a "file" in /proc</span></span>
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+<a id='x1-37026r3'></a><span class='ecrm-0500'>3</span><span id='textcolor805'><span class='ectt-0800'> * This program uses the seq_file library to manage the /proc file.</span></span>
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+<a id='x1-37028r4'></a><span class='ecrm-0500'>4</span><span id='textcolor806'><span class='ectt-0800'> */</span></span>
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+<a id='x1-37030r5'></a><span class='ecrm-0500'>5</span>
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+<a id='x1-37032r6'></a><span class='ecrm-0500'>6</span><span id='textcolor807'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor808'><span class='ectt-0800'><linux/kernel.h> /* We are doing kernel work */</span></span>
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+<a id='x1-37034r7'></a><span class='ecrm-0500'>7</span><span id='textcolor809'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor810'><span class='ectt-0800'><linux/module.h> /* Specifically, a module */</span></span>
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+<a id='x1-37036r8'></a><span class='ecrm-0500'>8</span><span id='textcolor811'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor812'><span class='ectt-0800'><linux/proc_fs.h> /* Necessary because we use proc fs */</span></span>
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+<a id='x1-37038r9'></a><span class='ecrm-0500'>9</span><span id='textcolor813'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor814'><span class='ectt-0800'><linux/seq_file.h> /* for seq_file */</span></span>
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+<a id='x1-37040r10'></a><span class='ecrm-0500'>10</span><span id='textcolor815'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor816'><span class='ectt-0800'><linux/version.h></span></span>
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+<a id='x1-37042r11'></a><span class='ecrm-0500'>11</span>
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+<a id='x1-37044r12'></a><span class='ecrm-0500'>12</span><span id='textcolor817'><span class='ectt-0800'>#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 6, 0)</span></span>
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+<a id='x1-37046r13'></a><span class='ecrm-0500'>13</span><span id='textcolor818'><span class='ectt-0800'>#define HAVE_PROC_OPS</span></span>
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+<a id='x1-37048r14'></a><span class='ecrm-0500'>14</span><span id='textcolor819'><span class='ectt-0800'>#endif</span></span>
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+<a id='x1-37050r15'></a><span class='ecrm-0500'>15</span>
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+<a id='x1-37052r16'></a><span class='ecrm-0500'>16</span><span id='textcolor820'><span class='ectt-0800'>#define PROC_NAME "iter"</span></span>
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+<a id='x1-37054r17'></a><span class='ecrm-0500'>17</span>
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+<a id='x1-37056r18'></a><span class='ecrm-0500'>18</span><span id='textcolor821'><span class='ectt-0800'>/* This function is called at the beginning of a sequence.</span></span>
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+<a id='x1-37058r19'></a><span class='ecrm-0500'>19</span><span id='textcolor822'><span class='ectt-0800'> * ie, when:</span></span>
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+<a id='x1-37060r20'></a><span class='ecrm-0500'>20</span><span id='textcolor823'><span class='ectt-0800'> * - the /proc file is read (first time)</span></span>
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+<a id='x1-37062r21'></a><span class='ecrm-0500'>21</span><span id='textcolor824'><span class='ectt-0800'> * - after the function stop (end of sequence)</span></span>
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+<a id='x1-37064r22'></a><span class='ecrm-0500'>22</span><span id='textcolor825'><span class='ectt-0800'> */</span></span>
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+<a id='x1-37066r23'></a><span class='ecrm-0500'>23</span><span id='textcolor826'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor827'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> *my_seq_start(</span><span id='textcolor828'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> seq_file *s, loff_t *pos)</span>
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+<a id='x1-37068r24'></a><span class='ecrm-0500'>24</span><span class='ectt-0800'>{</span>
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+<a id='x1-37070r25'></a><span class='ecrm-0500'>25</span><span class='ectt-0800'> </span><span id='textcolor829'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor830'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor831'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> counter = 0;</span>
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+<a id='x1-37072r26'></a><span class='ecrm-0500'>26</span>
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+<a id='x1-37074r27'></a><span class='ecrm-0500'>27</span><span class='ectt-0800'> </span><span id='textcolor832'><span class='ectt-0800'>/* beginning a new sequence? */</span></span>
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+<a id='x1-37076r28'></a><span class='ecrm-0500'>28</span><span class='ectt-0800'> </span><span id='textcolor833'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (*pos == 0) {</span>
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+<a id='x1-37078r29'></a><span class='ecrm-0500'>29</span><span class='ectt-0800'> </span><span id='textcolor834'><span class='ectt-0800'>/* yes => return a non null value to begin the sequence */</span></span>
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+<a id='x1-37080r30'></a><span class='ecrm-0500'>30</span><span class='ectt-0800'> </span><span id='textcolor835'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> &counter;</span>
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+<a id='x1-37082r31'></a><span class='ecrm-0500'>31</span><span class='ectt-0800'> }</span>
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+<a id='x1-37084r32'></a><span class='ecrm-0500'>32</span><span class='ectt-0800'> </span><span id='textcolor836'><span class='ectt-0800'>/* no => it is the end of the sequence, return end to stop reading */</span></span>
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+<a id='x1-37086r33'></a><span class='ecrm-0500'>33</span><span class='ectt-0800'> *pos = 0;</span>
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+<a id='x1-37088r34'></a><span class='ecrm-0500'>34</span><span class='ectt-0800'> </span><span id='textcolor837'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> NULL;</span>
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+<a id='x1-37090r35'></a><span class='ecrm-0500'>35</span><span class='ectt-0800'>}</span>
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+<a id='x1-37092r36'></a><span class='ecrm-0500'>36</span>
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+<a id='x1-37094r37'></a><span class='ecrm-0500'>37</span><span id='textcolor838'><span class='ectt-0800'>/* This function is called after the beginning of a sequence.</span></span>
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+<a id='x1-37096r38'></a><span class='ecrm-0500'>38</span><span id='textcolor839'><span class='ectt-0800'> * It is called untill the return is NULL (this ends the sequence).</span></span>
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+<a id='x1-37098r39'></a><span class='ecrm-0500'>39</span><span id='textcolor840'><span class='ectt-0800'> */</span></span>
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+<a id='x1-37100r40'></a><span class='ecrm-0500'>40</span><span id='textcolor841'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor842'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> *my_seq_next(</span><span id='textcolor843'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> seq_file *s, </span><span id='textcolor844'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> *v, loff_t *pos)</span>
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+<a id='x1-37102r41'></a><span class='ecrm-0500'>41</span><span class='ectt-0800'>{</span>
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+<a id='x1-37104r42'></a><span class='ecrm-0500'>42</span><span class='ectt-0800'> </span><span id='textcolor845'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor846'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> *tmp_v = (</span><span id='textcolor847'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor848'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> *) v;</span>
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+<a id='x1-37106r43'></a><span class='ecrm-0500'>43</span><span class='ectt-0800'> (*tmp_v)++;</span>
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+<a id='x1-37108r44'></a><span class='ecrm-0500'>44</span><span class='ectt-0800'> (*pos)++;</span>
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+<a id='x1-37110r45'></a><span class='ecrm-0500'>45</span><span class='ectt-0800'> </span><span id='textcolor849'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> NULL;</span>
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+<a id='x1-37112r46'></a><span class='ecrm-0500'>46</span><span class='ectt-0800'>}</span>
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+<a id='x1-37114r47'></a><span class='ecrm-0500'>47</span>
|
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+<a id='x1-37116r48'></a><span class='ecrm-0500'>48</span><span id='textcolor850'><span class='ectt-0800'>/* This function is called at the end of a sequence. */</span></span>
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+<a id='x1-37118r49'></a><span class='ecrm-0500'>49</span><span id='textcolor851'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor852'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> my_seq_stop(</span><span id='textcolor853'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> seq_file *s, </span><span id='textcolor854'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> *v)</span>
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+<a id='x1-37120r50'></a><span class='ecrm-0500'>50</span><span class='ectt-0800'>{</span>
|
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|
+<a id='x1-37122r51'></a><span class='ecrm-0500'>51</span><span class='ectt-0800'> </span><span id='textcolor855'><span class='ectt-0800'>/* nothing to do, we use a static value in start() */</span></span>
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+<a id='x1-37124r52'></a><span class='ecrm-0500'>52</span><span class='ectt-0800'>}</span>
|
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|
+<a id='x1-37126r53'></a><span class='ecrm-0500'>53</span>
|
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|
+<a id='x1-37128r54'></a><span class='ecrm-0500'>54</span><span id='textcolor856'><span class='ectt-0800'>/* This function is called for each "step" of a sequence. */</span></span>
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+<a id='x1-37130r55'></a><span class='ecrm-0500'>55</span><span id='textcolor857'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor858'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> my_seq_show(</span><span id='textcolor859'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> seq_file *s, </span><span id='textcolor860'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> *v)</span>
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+<a id='x1-37132r56'></a><span class='ecrm-0500'>56</span><span class='ectt-0800'>{</span>
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+<a id='x1-37134r57'></a><span class='ecrm-0500'>57</span><span class='ectt-0800'> loff_t *spos = (loff_t *) v;</span>
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+<a id='x1-37136r58'></a><span class='ecrm-0500'>58</span>
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|
+<a id='x1-37138r59'></a><span class='ecrm-0500'>59</span><span class='ectt-0800'> seq_printf(s, </span><span id='textcolor861'><span class='ectt-0800'>"%Ld</span></span><span id='textcolor862'><span class='ectt-0800'>\n</span></span><span id='textcolor863'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, *spos);</span>
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|
+<a id='x1-37140r60'></a><span class='ecrm-0500'>60</span><span class='ectt-0800'> </span><span id='textcolor864'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> 0;</span>
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+<a id='x1-37142r61'></a><span class='ecrm-0500'>61</span><span class='ectt-0800'>}</span>
|
|
|
+<a id='x1-37144r62'></a><span class='ecrm-0500'>62</span>
|
|
|
+<a id='x1-37146r63'></a><span class='ecrm-0500'>63</span><span id='textcolor865'><span class='ectt-0800'>/* This structure gather "function" to manage the sequence */</span></span>
|
|
|
+<a id='x1-37148r64'></a><span class='ecrm-0500'>64</span><span id='textcolor866'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor867'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> seq_operations my_seq_ops = {</span>
|
|
|
+<a id='x1-37150r65'></a><span class='ecrm-0500'>65</span><span class='ectt-0800'> .start = my_seq_start,</span>
|
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|
+<a id='x1-37152r66'></a><span class='ecrm-0500'>66</span><span class='ectt-0800'> .next = my_seq_next,</span>
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|
+<a id='x1-37154r67'></a><span class='ecrm-0500'>67</span><span class='ectt-0800'> .stop = my_seq_stop,</span>
|
|
|
+<a id='x1-37156r68'></a><span class='ecrm-0500'>68</span><span class='ectt-0800'> .show = my_seq_show,</span>
|
|
|
+<a id='x1-37158r69'></a><span class='ecrm-0500'>69</span><span class='ectt-0800'>};</span>
|
|
|
+<a id='x1-37160r70'></a><span class='ecrm-0500'>70</span>
|
|
|
+<a id='x1-37162r71'></a><span class='ecrm-0500'>71</span><span id='textcolor868'><span class='ectt-0800'>/* This function is called when the /proc file is open. */</span></span>
|
|
|
+<a id='x1-37164r72'></a><span class='ecrm-0500'>72</span><span id='textcolor869'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor870'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> my_open(</span><span id='textcolor871'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> inode *inode, </span><span id='textcolor872'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file *file)</span>
|
|
|
+<a id='x1-37166r73'></a><span class='ecrm-0500'>73</span><span class='ectt-0800'>{</span>
|
|
|
+<a id='x1-37168r74'></a><span class='ecrm-0500'>74</span><span class='ectt-0800'> </span><span id='textcolor873'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> seq_open(file, &my_seq_ops);</span>
|
|
|
+<a id='x1-37170r75'></a><span class='ecrm-0500'>75</span><span class='ectt-0800'>};</span>
|
|
|
+<a id='x1-37172r76'></a><span class='ecrm-0500'>76</span>
|
|
|
+<a id='x1-37174r77'></a><span class='ecrm-0500'>77</span><span id='textcolor874'><span class='ectt-0800'>/* This structure gather "function" that manage the /proc file */</span></span>
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|
|
+<a id='x1-37176r78'></a><span class='ecrm-0500'>78</span><span id='textcolor875'><span class='ectt-0800'>#ifdef HAVE_PROC_OPS</span></span>
|
|
|
+<a id='x1-37178r79'></a><span class='ecrm-0500'>79</span><span id='textcolor876'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor877'><span class='ectt-0800'>const</span></span><span class='ectt-0800'> </span><span id='textcolor878'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> proc_ops my_file_ops = {</span>
|
|
|
+<a id='x1-37180r80'></a><span class='ecrm-0500'>80</span><span class='ectt-0800'> .proc_open = my_open,</span>
|
|
|
+<a id='x1-37182r81'></a><span class='ecrm-0500'>81</span><span class='ectt-0800'> .proc_read = seq_read,</span>
|
|
|
+<a id='x1-37184r82'></a><span class='ecrm-0500'>82</span><span class='ectt-0800'> .proc_lseek = seq_lseek,</span>
|
|
|
+<a id='x1-37186r83'></a><span class='ecrm-0500'>83</span><span class='ectt-0800'> .proc_release = seq_release,</span>
|
|
|
+<a id='x1-37188r84'></a><span class='ecrm-0500'>84</span><span class='ectt-0800'>};</span>
|
|
|
+<a id='x1-37190r85'></a><span class='ecrm-0500'>85</span><span id='textcolor879'><span class='ectt-0800'>#else</span></span>
|
|
|
+<a id='x1-37192r86'></a><span class='ecrm-0500'>86</span><span id='textcolor880'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor881'><span class='ectt-0800'>const</span></span><span class='ectt-0800'> </span><span id='textcolor882'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> file_operations my_file_ops = {</span>
|
|
|
+<a id='x1-37194r87'></a><span class='ecrm-0500'>87</span><span class='ectt-0800'> .open = my_open,</span>
|
|
|
+<a id='x1-37196r88'></a><span class='ecrm-0500'>88</span><span class='ectt-0800'> .read = seq_read,</span>
|
|
|
+<a id='x1-37198r89'></a><span class='ecrm-0500'>89</span><span class='ectt-0800'> .llseek = seq_lseek,</span>
|
|
|
+<a id='x1-37200r90'></a><span class='ecrm-0500'>90</span><span class='ectt-0800'> .release = seq_release,</span>
|
|
|
+<a id='x1-37202r91'></a><span class='ecrm-0500'>91</span><span class='ectt-0800'>};</span>
|
|
|
+<a id='x1-37204r92'></a><span class='ecrm-0500'>92</span><span id='textcolor883'><span class='ectt-0800'>#endif</span></span>
|
|
|
+<a id='x1-37206r93'></a><span class='ecrm-0500'>93</span>
|
|
|
+<a id='x1-37208r94'></a><span class='ecrm-0500'>94</span><span id='textcolor884'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor885'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> __init procfs4_init(</span><span id='textcolor886'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
|
|
|
+<a id='x1-37210r95'></a><span class='ecrm-0500'>95</span><span class='ectt-0800'>{</span>
|
|
|
+<a id='x1-37212r96'></a><span class='ecrm-0500'>96</span><span class='ectt-0800'> </span><span id='textcolor887'><span class='ectt-0800'>struct</span></span><span class='ectt-0800'> proc_dir_entry *entry;</span>
|
|
|
+<a id='x1-37214r97'></a><span class='ecrm-0500'>97</span>
|
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+<a id='x1-37216r98'></a><span class='ecrm-0500'>98</span><span class='ectt-0800'> entry = proc_create(PROC_NAME, 0, NULL, &my_file_ops);</span>
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+<a id='x1-37218r99'></a><span class='ecrm-0500'>99</span><span class='ectt-0800'> </span><span id='textcolor888'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (entry == NULL) {</span>
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+<a id='x1-37220r100'></a><span class='ecrm-0500'>100</span><span class='ectt-0800'> remove_proc_entry(PROC_NAME, NULL);</span>
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+<a id='x1-37222r101'></a><span class='ecrm-0500'>101</span><span class='ectt-0800'> pr_debug(</span><span id='textcolor889'><span class='ectt-0800'>"Error: Could not initialize /proc/%s</span></span><span id='textcolor890'><span class='ectt-0800'>\n</span></span><span id='textcolor891'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, PROC_NAME);</span>
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+<a id='x1-37224r102'></a><span class='ecrm-0500'>102</span><span class='ectt-0800'> </span><span id='textcolor892'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> -ENOMEM;</span>
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+<a id='x1-37226r103'></a><span class='ecrm-0500'>103</span><span class='ectt-0800'> }</span>
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+<a id='x1-37228r104'></a><span class='ecrm-0500'>104</span>
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+<a id='x1-37230r105'></a><span class='ecrm-0500'>105</span><span class='ectt-0800'> </span><span id='textcolor893'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> 0;</span>
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+<a id='x1-37232r106'></a><span class='ecrm-0500'>106</span><span class='ectt-0800'>}</span>
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+<a id='x1-37234r107'></a><span class='ecrm-0500'>107</span>
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+<a id='x1-37236r108'></a><span class='ecrm-0500'>108</span><span id='textcolor894'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor895'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> __exit procfs4_exit(</span><span id='textcolor896'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
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+<a id='x1-37238r109'></a><span class='ecrm-0500'>109</span><span class='ectt-0800'>{</span>
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+<a id='x1-37240r110'></a><span class='ecrm-0500'>110</span><span class='ectt-0800'> remove_proc_entry(PROC_NAME, NULL);</span>
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+<a id='x1-37242r111'></a><span class='ecrm-0500'>111</span><span class='ectt-0800'> pr_debug(</span><span id='textcolor897'><span class='ectt-0800'>"/proc/%s removed</span></span><span id='textcolor898'><span class='ectt-0800'>\n</span></span><span id='textcolor899'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, PROC_NAME);</span>
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+<a id='x1-37244r112'></a><span class='ecrm-0500'>112</span><span class='ectt-0800'>}</span>
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+<a id='x1-37246r113'></a><span class='ecrm-0500'>113</span>
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+<a id='x1-37248r114'></a><span class='ecrm-0500'>114</span><span class='ectt-0800'>module_init(procfs4_init);</span>
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+<a id='x1-37250r115'></a><span class='ecrm-0500'>115</span><span class='ectt-0800'>module_exit(procfs4_exit);</span>
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+<a id='x1-37252r116'></a><span class='ecrm-0500'>116</span>
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+<a id='x1-37254r117'></a><span class='ecrm-0500'>117</span><span class='ectt-0800'>MODULE_LICENSE(</span><span id='textcolor900'><span class='ectt-0800'>"GPL"</span></span><span class='ectt-0800'>);</span></pre>
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<!-- l. 1070 --><p class='indent'> If you want more information, you can read this web page:
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</p>
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<ul class='itemize1'>
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@@ -2877,9 +2898,9 @@ replace the system call to open a file with our own function, called
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<code> <span class='ectt-1000'>our_sys_open</span>
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</code>. This function checks the uid (user’s id) of the current process, and if it is equal to the uid we
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spy on, it calls <code> <span class='ectt-1000'>pr_info()</span>
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-</code> to display the name of the file to be opened. Then, either way, it calls the
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-original open() function with the same parameters, to actually open the
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-file.
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+</code> to display the name of the file to be opened. Then, either way, it calls the original
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+<code> <span class='ectt-1000'>open()</span>
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+</code> function with the same parameters, to actually open the file.
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</p><!-- l. 1205 --><p class='indent'> The <code> <span class='ectt-1000'>init_module</span>
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</code> function replaces the appropriate location in
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<code> <span class='ectt-1000'>sys_call_table</span>
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@@ -2935,143 +2956,143 @@ patch and the README. Depending on your kernel version, you might even need to
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hand apply the patch.
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</p><!-- l. 1 --><p class='indent'>
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</p>
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- <pre class='fancyvrb' id='fancyvrb51'><a id='x1-40033r1'></a><span class='ecrm-0500'>1</span><span id='textcolor1339'><span class='ectt-0800'>/*</span></span>
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-<a id='x1-40035r2'></a><span class='ecrm-0500'>2</span><span id='textcolor1340'><span class='ectt-0800'> * syscall.c</span></span>
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-<a id='x1-40037r3'></a><span class='ecrm-0500'>3</span><span id='textcolor1341'><span class='ectt-0800'> *</span></span>
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-<a id='x1-40039r4'></a><span class='ecrm-0500'>4</span><span id='textcolor1342'><span class='ectt-0800'> * System call "stealing" sample.</span></span>
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-<a id='x1-40041r5'></a><span class='ecrm-0500'>5</span><span id='textcolor1343'><span class='ectt-0800'> *</span></span>
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-<a id='x1-40043r6'></a><span class='ecrm-0500'>6</span><span id='textcolor1344'><span class='ectt-0800'> * Disables page protection at a processor level by changing the 16th bit</span></span>
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-<a id='x1-40045r7'></a><span class='ecrm-0500'>7</span><span id='textcolor1345'><span class='ectt-0800'> * in the cr0 register (could be Intel specific).</span></span>
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-<a id='x1-40047r8'></a><span class='ecrm-0500'>8</span><span id='textcolor1346'><span class='ectt-0800'> *</span></span>
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-<a id='x1-40049r9'></a><span class='ecrm-0500'>9</span><span id='textcolor1347'><span class='ectt-0800'> * Based on example by Peter Jay Salzman and</span></span>
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-<a id='x1-40051r10'></a><span class='ecrm-0500'>10</span><span id='textcolor1348'><span class='ectt-0800'> * https://bbs.archlinux.org/viewtopic.php?id=139406</span></span>
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-<a id='x1-40053r11'></a><span class='ecrm-0500'>11</span><span id='textcolor1349'><span class='ectt-0800'> */</span></span>
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-<a id='x1-40055r12'></a><span class='ecrm-0500'>12</span>
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-<a id='x1-40057r13'></a><span class='ecrm-0500'>13</span><span id='textcolor1350'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1351'><span class='ectt-0800'><linux/delay.h></span></span>
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-<a id='x1-40059r14'></a><span class='ecrm-0500'>14</span><span id='textcolor1352'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1353'><span class='ectt-0800'><linux/kernel.h></span></span>
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-<a id='x1-40061r15'></a><span class='ecrm-0500'>15</span><span id='textcolor1354'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1355'><span class='ectt-0800'><linux/module.h></span></span>
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-<a id='x1-40063r16'></a><span class='ecrm-0500'>16</span><span id='textcolor1356'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1357'><span class='ectt-0800'><linux/moduleparam.h> /* which will have params */</span></span>
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-<a id='x1-40065r17'></a><span class='ecrm-0500'>17</span><span id='textcolor1358'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1359'><span class='ectt-0800'><linux/syscalls.h></span></span>
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-<a id='x1-40067r18'></a><span class='ecrm-0500'>18</span><span id='textcolor1360'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1361'><span class='ectt-0800'><linux/unistd.h> /* The list of system calls */</span></span>
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-<a id='x1-40069r19'></a><span class='ecrm-0500'>19</span>
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-<a id='x1-40071r20'></a><span class='ecrm-0500'>20</span><span id='textcolor1362'><span class='ectt-0800'>/* For the current (process) structure, we need this to know who the</span></span>
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-<a id='x1-40073r21'></a><span class='ecrm-0500'>21</span><span id='textcolor1363'><span class='ectt-0800'> * current user is.</span></span>
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-<a id='x1-40075r22'></a><span class='ecrm-0500'>22</span><span id='textcolor1364'><span class='ectt-0800'> */</span></span>
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-<a id='x1-40077r23'></a><span class='ecrm-0500'>23</span><span id='textcolor1365'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1366'><span class='ectt-0800'><linux/sched.h></span></span>
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-<a id='x1-40079r24'></a><span class='ecrm-0500'>24</span><span id='textcolor1367'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1368'><span class='ectt-0800'><linux/uaccess.h></span></span>
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-<a id='x1-40081r25'></a><span class='ecrm-0500'>25</span>
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-<a id='x1-40083r26'></a><span class='ecrm-0500'>26</span><span id='textcolor1369'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor1370'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> **sys_call_table;</span>
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-<a id='x1-40085r27'></a><span class='ecrm-0500'>27</span><span id='textcolor1371'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor1372'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> original_cr0;</span>
|
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-<a id='x1-40087r28'></a><span class='ecrm-0500'>28</span>
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-<a id='x1-40089r29'></a><span class='ecrm-0500'>29</span><span id='textcolor1373'><span class='ectt-0800'>/* UID we want to spy on - will be filled from the command line. */</span></span>
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-<a id='x1-40091r30'></a><span class='ecrm-0500'>30</span><span id='textcolor1374'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor1375'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> uid;</span>
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-<a id='x1-40093r31'></a><span class='ecrm-0500'>31</span><span class='ectt-0800'>module_param(uid, </span><span id='textcolor1376'><span class='ectt-0800'>int</span></span><span class='ectt-0800'>, 0644);</span>
|
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-<a id='x1-40095r32'></a><span class='ecrm-0500'>32</span>
|
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|
-<a id='x1-40097r33'></a><span class='ecrm-0500'>33</span><span id='textcolor1377'><span class='ectt-0800'>/* A pointer to the original system call. The reason we keep this, rather</span></span>
|
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-<a id='x1-40099r34'></a><span class='ecrm-0500'>34</span><span id='textcolor1378'><span class='ectt-0800'> * than call the original function (sys_open), is because somebody else</span></span>
|
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-<a id='x1-40101r35'></a><span class='ecrm-0500'>35</span><span id='textcolor1379'><span class='ectt-0800'> * might have replaced the system call before us. Note that this is not</span></span>
|
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-<a id='x1-40103r36'></a><span class='ecrm-0500'>36</span><span id='textcolor1380'><span class='ectt-0800'> * 100% safe, because if another module replaced sys_open before us,</span></span>
|
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-<a id='x1-40105r37'></a><span class='ecrm-0500'>37</span><span id='textcolor1381'><span class='ectt-0800'> * then when we are inserted, we will call the function in that module -</span></span>
|
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-<a id='x1-40107r38'></a><span class='ecrm-0500'>38</span><span id='textcolor1382'><span class='ectt-0800'> * and it might be removed before we are.</span></span>
|
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-<a id='x1-40109r39'></a><span class='ecrm-0500'>39</span><span id='textcolor1383'><span class='ectt-0800'> *</span></span>
|
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|
-<a id='x1-40111r40'></a><span class='ecrm-0500'>40</span><span id='textcolor1384'><span class='ectt-0800'> * Another reason for this is that we can not get sys_open.</span></span>
|
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-<a id='x1-40113r41'></a><span class='ecrm-0500'>41</span><span id='textcolor1385'><span class='ectt-0800'> * It is a static variable, so it is not exported.</span></span>
|
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-<a id='x1-40115r42'></a><span class='ecrm-0500'>42</span><span id='textcolor1386'><span class='ectt-0800'> */</span></span>
|
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|
-<a id='x1-40117r43'></a><span class='ecrm-0500'>43</span><span class='ectt-0800'>asmlinkage int (*original_call)(</span><span id='textcolor1387'><span class='ectt-0800'>const</span></span><span class='ectt-0800'> </span><span id='textcolor1388'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> *, </span><span id='textcolor1389'><span class='ectt-0800'>int</span></span><span class='ectt-0800'>, </span><span id='textcolor1390'><span class='ectt-0800'>int</span></span><span class='ectt-0800'>);</span>
|
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-<a id='x1-40119r44'></a><span class='ecrm-0500'>44</span>
|
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|
-<a id='x1-40121r45'></a><span class='ecrm-0500'>45</span><span id='textcolor1391'><span class='ectt-0800'>/* The function we will replace sys_open (the function called when you</span></span>
|
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|
-<a id='x1-40123r46'></a><span class='ecrm-0500'>46</span><span id='textcolor1392'><span class='ectt-0800'> * call the open system call) with. To find the exact prototype, with</span></span>
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-<a id='x1-40125r47'></a><span class='ecrm-0500'>47</span><span id='textcolor1393'><span class='ectt-0800'> * the number and type of arguments, we find the original function first</span></span>
|
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-<a id='x1-40127r48'></a><span class='ecrm-0500'>48</span><span id='textcolor1394'><span class='ectt-0800'> * (it is at fs/open.c).</span></span>
|
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|
-<a id='x1-40129r49'></a><span class='ecrm-0500'>49</span><span id='textcolor1395'><span class='ectt-0800'> *</span></span>
|
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|
-<a id='x1-40131r50'></a><span class='ecrm-0500'>50</span><span id='textcolor1396'><span class='ectt-0800'> * In theory, this means that we are tied to the current version of the</span></span>
|
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|
-<a id='x1-40133r51'></a><span class='ecrm-0500'>51</span><span id='textcolor1397'><span class='ectt-0800'> * kernel. In practice, the system calls almost never change (it would</span></span>
|
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|
-<a id='x1-40135r52'></a><span class='ecrm-0500'>52</span><span id='textcolor1398'><span class='ectt-0800'> * wreck havoc and require programs to be recompiled, since the system</span></span>
|
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|
-<a id='x1-40137r53'></a><span class='ecrm-0500'>53</span><span id='textcolor1399'><span class='ectt-0800'> * calls are the interface between the kernel and the processes).</span></span>
|
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-<a id='x1-40139r54'></a><span class='ecrm-0500'>54</span><span id='textcolor1400'><span class='ectt-0800'> */</span></span>
|
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|
-<a id='x1-40141r55'></a><span class='ecrm-0500'>55</span><span class='ectt-0800'>asmlinkage </span><span id='textcolor1401'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> our_sys_open(</span><span id='textcolor1402'><span class='ectt-0800'>const</span></span><span class='ectt-0800'> </span><span id='textcolor1403'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> *filename, </span><span id='textcolor1404'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> flags, </span><span id='textcolor1405'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> mode)</span>
|
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|
-<a id='x1-40143r56'></a><span class='ecrm-0500'>56</span><span class='ectt-0800'>{</span>
|
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|
-<a id='x1-40145r57'></a><span class='ecrm-0500'>57</span><span class='ectt-0800'> </span><span id='textcolor1406'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> i = 0;</span>
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|
-<a id='x1-40147r58'></a><span class='ecrm-0500'>58</span><span class='ectt-0800'> </span><span id='textcolor1407'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> ch;</span>
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|
-<a id='x1-40149r59'></a><span class='ecrm-0500'>59</span>
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|
-<a id='x1-40151r60'></a><span class='ecrm-0500'>60</span><span class='ectt-0800'> </span><span id='textcolor1408'><span class='ectt-0800'>/* Report the file, if relevant */</span></span>
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|
-<a id='x1-40153r61'></a><span class='ecrm-0500'>61</span><span class='ectt-0800'> pr_info(</span><span id='textcolor1409'><span class='ectt-0800'>"Opened file by %d: "</span></span><span class='ectt-0800'>, uid);</span>
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|
-<a id='x1-40155r62'></a><span class='ecrm-0500'>62</span><span class='ectt-0800'> </span><span id='textcolor1410'><span class='ectt-0800'>do</span></span><span class='ectt-0800'> {</span>
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|
-<a id='x1-40157r63'></a><span class='ecrm-0500'>63</span><span class='ectt-0800'> get_user(ch, filename + i);</span>
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|
-<a id='x1-40159r64'></a><span class='ecrm-0500'>64</span><span class='ectt-0800'> i++;</span>
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|
-<a id='x1-40161r65'></a><span class='ecrm-0500'>65</span><span class='ectt-0800'> pr_info(</span><span id='textcolor1411'><span class='ectt-0800'>"%c"</span></span><span class='ectt-0800'>, ch);</span>
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|
-<a id='x1-40163r66'></a><span class='ecrm-0500'>66</span><span class='ectt-0800'> } </span><span id='textcolor1412'><span class='ectt-0800'>while</span></span><span class='ectt-0800'> (ch != 0);</span>
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|
-<a id='x1-40165r67'></a><span class='ecrm-0500'>67</span><span class='ectt-0800'> pr_info(</span><span id='textcolor1413'><span class='ectt-0800'>"</span></span><span id='textcolor1414'><span class='ectt-0800'>\n</span></span><span id='textcolor1415'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
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|
-<a id='x1-40167r68'></a><span class='ecrm-0500'>68</span>
|
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|
-<a id='x1-40169r69'></a><span class='ecrm-0500'>69</span><span class='ectt-0800'> </span><span id='textcolor1416'><span class='ectt-0800'>/* Call the original sys_open - otherwise, we lose the ability to</span></span>
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|
-<a id='x1-40171r70'></a><span class='ecrm-0500'>70</span><span id='textcolor1417'><span class='ectt-0800'> * open files.</span></span>
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|
-<a id='x1-40173r71'></a><span class='ecrm-0500'>71</span><span id='textcolor1418'><span class='ectt-0800'> */</span></span>
|
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|
-<a id='x1-40175r72'></a><span class='ecrm-0500'>72</span><span class='ectt-0800'> </span><span id='textcolor1419'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> original_call(filename, flags, mode);</span>
|
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|
-<a id='x1-40177r73'></a><span class='ecrm-0500'>73</span><span class='ectt-0800'>}</span>
|
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|
-<a id='x1-40179r74'></a><span class='ecrm-0500'>74</span>
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-<a id='x1-40181r75'></a><span class='ecrm-0500'>75</span><span id='textcolor1420'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor1421'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor1422'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> **aquire_sys_call_table(</span><span id='textcolor1423'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
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-<a id='x1-40183r76'></a><span class='ecrm-0500'>76</span><span class='ectt-0800'>{</span>
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-<a id='x1-40185r77'></a><span class='ecrm-0500'>77</span><span class='ectt-0800'> </span><span id='textcolor1424'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor1425'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> </span><span id='textcolor1426'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> offset = PAGE_OFFSET;</span>
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-<a id='x1-40187r78'></a><span class='ecrm-0500'>78</span><span class='ectt-0800'> </span><span id='textcolor1427'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor1428'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> **sct;</span>
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-<a id='x1-40189r79'></a><span class='ecrm-0500'>79</span>
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-<a id='x1-40191r80'></a><span class='ecrm-0500'>80</span><span class='ectt-0800'> </span><span id='textcolor1429'><span class='ectt-0800'>while</span></span><span class='ectt-0800'> (offset < ULLONG_MAX) {</span>
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-<a id='x1-40193r81'></a><span class='ecrm-0500'>81</span><span class='ectt-0800'> sct = (</span><span id='textcolor1430'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor1431'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> **) offset;</span>
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-<a id='x1-40195r82'></a><span class='ecrm-0500'>82</span>
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-<a id='x1-40197r83'></a><span class='ecrm-0500'>83</span><span class='ectt-0800'> </span><span id='textcolor1432'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (sct[__NR_close] == (</span><span id='textcolor1433'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor1434'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> *) ksys_close)</span>
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-<a id='x1-40199r84'></a><span class='ecrm-0500'>84</span><span class='ectt-0800'> </span><span id='textcolor1435'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> sct;</span>
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-<a id='x1-40201r85'></a><span class='ecrm-0500'>85</span>
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-<a id='x1-40203r86'></a><span class='ecrm-0500'>86</span><span class='ectt-0800'> offset += </span><span id='textcolor1436'><span class='ectt-0800'>sizeof</span></span><span class='ectt-0800'>(</span><span id='textcolor1437'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> *);</span>
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-<a id='x1-40205r87'></a><span class='ecrm-0500'>87</span><span class='ectt-0800'> }</span>
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-<a id='x1-40207r88'></a><span class='ecrm-0500'>88</span>
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-<a id='x1-40209r89'></a><span class='ecrm-0500'>89</span><span class='ectt-0800'> </span><span id='textcolor1438'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> NULL;</span>
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-<a id='x1-40211r90'></a><span class='ecrm-0500'>90</span><span class='ectt-0800'>}</span>
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-<a id='x1-40213r91'></a><span class='ecrm-0500'>91</span>
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-<a id='x1-40215r92'></a><span class='ecrm-0500'>92</span><span id='textcolor1439'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor1440'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> __init syscall_start(</span><span id='textcolor1441'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
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-<a id='x1-40217r93'></a><span class='ecrm-0500'>93</span><span class='ectt-0800'>{</span>
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-<a id='x1-40219r94'></a><span class='ecrm-0500'>94</span><span class='ectt-0800'> </span><span id='textcolor1442'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (!(sys_call_table = aquire_sys_call_table()))</span>
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-<a id='x1-40221r95'></a><span class='ecrm-0500'>95</span><span class='ectt-0800'> </span><span id='textcolor1443'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> -1;</span>
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-<a id='x1-40223r96'></a><span class='ecrm-0500'>96</span>
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-<a id='x1-40225r97'></a><span class='ecrm-0500'>97</span><span class='ectt-0800'> original_cr0 = read_cr0();</span>
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-<a id='x1-40227r98'></a><span class='ecrm-0500'>98</span>
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-<a id='x1-40229r99'></a><span class='ecrm-0500'>99</span><span class='ectt-0800'> write_cr0(original_cr0 & ~0x00010000);</span>
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-<a id='x1-40231r100'></a><span class='ecrm-0500'>100</span>
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-<a id='x1-40233r101'></a><span class='ecrm-0500'>101</span><span class='ectt-0800'> </span><span id='textcolor1444'><span class='ectt-0800'>/* keep track of the original open function */</span></span>
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-<a id='x1-40235r102'></a><span class='ecrm-0500'>102</span><span class='ectt-0800'> original_call = (</span><span id='textcolor1445'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> *) sys_call_table[__NR_open];</span>
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-<a id='x1-40237r103'></a><span class='ecrm-0500'>103</span>
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-<a id='x1-40239r104'></a><span class='ecrm-0500'>104</span><span class='ectt-0800'> </span><span id='textcolor1446'><span class='ectt-0800'>/* use our open function instead */</span></span>
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-<a id='x1-40241r105'></a><span class='ecrm-0500'>105</span><span class='ectt-0800'> sys_call_table[__NR_open] = (</span><span id='textcolor1447'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor1448'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> *) our_sys_open;</span>
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-<a id='x1-40243r106'></a><span class='ecrm-0500'>106</span>
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-<a id='x1-40245r107'></a><span class='ecrm-0500'>107</span><span class='ectt-0800'> write_cr0(original_cr0);</span>
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-<a id='x1-40247r108'></a><span class='ecrm-0500'>108</span>
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-<a id='x1-40249r109'></a><span class='ecrm-0500'>109</span><span class='ectt-0800'> pr_info(</span><span id='textcolor1449'><span class='ectt-0800'>"Spying on UID:%d</span></span><span id='textcolor1450'><span class='ectt-0800'>\n</span></span><span id='textcolor1451'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, uid);</span>
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-<a id='x1-40251r110'></a><span class='ecrm-0500'>110</span>
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-<a id='x1-40253r111'></a><span class='ecrm-0500'>111</span><span class='ectt-0800'> </span><span id='textcolor1452'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> 0;</span>
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-<a id='x1-40255r112'></a><span class='ecrm-0500'>112</span><span class='ectt-0800'>}</span>
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-<a id='x1-40257r113'></a><span class='ecrm-0500'>113</span>
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-<a id='x1-40259r114'></a><span class='ecrm-0500'>114</span><span id='textcolor1453'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor1454'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> __exit syscall_end(</span><span id='textcolor1455'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
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-<a id='x1-40261r115'></a><span class='ecrm-0500'>115</span><span class='ectt-0800'>{</span>
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-<a id='x1-40263r116'></a><span class='ecrm-0500'>116</span><span class='ectt-0800'> </span><span id='textcolor1456'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (!sys_call_table)</span>
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-<a id='x1-40265r117'></a><span class='ecrm-0500'>117</span><span class='ectt-0800'> </span><span id='textcolor1457'><span class='ectt-0800'>return</span></span><span class='ectt-0800'>;</span>
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-<a id='x1-40267r118'></a><span class='ecrm-0500'>118</span>
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-<a id='x1-40269r119'></a><span class='ecrm-0500'>119</span><span class='ectt-0800'> </span><span id='textcolor1458'><span class='ectt-0800'>/* Return the system call back to normal */</span></span>
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-<a id='x1-40271r120'></a><span class='ecrm-0500'>120</span><span class='ectt-0800'> </span><span id='textcolor1459'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (sys_call_table[__NR_open] != (</span><span id='textcolor1460'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor1461'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> *) our_sys_open) {</span>
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-<a id='x1-40273r121'></a><span class='ecrm-0500'>121</span><span class='ectt-0800'> pr_alert(</span><span id='textcolor1462'><span class='ectt-0800'>"Somebody else also played with the "</span></span><span class='ectt-0800'>);</span>
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-<a id='x1-40275r122'></a><span class='ecrm-0500'>122</span><span class='ectt-0800'> pr_alert(</span><span id='textcolor1463'><span class='ectt-0800'>"open system call</span></span><span id='textcolor1464'><span class='ectt-0800'>\n</span></span><span id='textcolor1465'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
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-<a id='x1-40277r123'></a><span class='ecrm-0500'>123</span><span class='ectt-0800'> pr_alert(</span><span id='textcolor1466'><span class='ectt-0800'>"The system may be left in "</span></span><span class='ectt-0800'>);</span>
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-<a id='x1-40279r124'></a><span class='ecrm-0500'>124</span><span class='ectt-0800'> pr_alert(</span><span id='textcolor1467'><span class='ectt-0800'>"an unstable state.</span></span><span id='textcolor1468'><span class='ectt-0800'>\n</span></span><span id='textcolor1469'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
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-<a id='x1-40281r125'></a><span class='ecrm-0500'>125</span><span class='ectt-0800'> }</span>
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-<a id='x1-40283r126'></a><span class='ecrm-0500'>126</span>
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-<a id='x1-40285r127'></a><span class='ecrm-0500'>127</span><span class='ectt-0800'> write_cr0(original_cr0 & ~0x00010000);</span>
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-<a id='x1-40287r128'></a><span class='ecrm-0500'>128</span><span class='ectt-0800'> sys_call_table[__NR_open] = (</span><span id='textcolor1470'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor1471'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> *) original_call;</span>
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-<a id='x1-40289r129'></a><span class='ecrm-0500'>129</span><span class='ectt-0800'> write_cr0(original_cr0);</span>
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-<a id='x1-40291r130'></a><span class='ecrm-0500'>130</span>
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-<a id='x1-40293r131'></a><span class='ecrm-0500'>131</span><span class='ectt-0800'> msleep(2000);</span>
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-<a id='x1-40295r132'></a><span class='ecrm-0500'>132</span><span class='ectt-0800'>}</span>
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-<a id='x1-40297r133'></a><span class='ecrm-0500'>133</span>
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-<a id='x1-40299r134'></a><span class='ecrm-0500'>134</span><span class='ectt-0800'>module_init(syscall_start);</span>
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-<a id='x1-40301r135'></a><span class='ecrm-0500'>135</span><span class='ectt-0800'>module_exit(syscall_end);</span>
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-<a id='x1-40303r136'></a><span class='ecrm-0500'>136</span>
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-<a id='x1-40305r137'></a><span class='ecrm-0500'>137</span><span class='ectt-0800'>MODULE_LICENSE(</span><span id='textcolor1472'><span class='ectt-0800'>"GPL"</span></span><span class='ectt-0800'>);</span></pre>
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+ <pre class='fancyvrb' id='fancyvrb51'><a id='x1-40034r1'></a><span class='ecrm-0500'>1</span><span id='textcolor1339'><span class='ectt-0800'>/*</span></span>
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+<a id='x1-40036r2'></a><span class='ecrm-0500'>2</span><span id='textcolor1340'><span class='ectt-0800'> * syscall.c</span></span>
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+<a id='x1-40038r3'></a><span class='ecrm-0500'>3</span><span id='textcolor1341'><span class='ectt-0800'> *</span></span>
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+<a id='x1-40040r4'></a><span class='ecrm-0500'>4</span><span id='textcolor1342'><span class='ectt-0800'> * System call "stealing" sample.</span></span>
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+<a id='x1-40042r5'></a><span class='ecrm-0500'>5</span><span id='textcolor1343'><span class='ectt-0800'> *</span></span>
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+<a id='x1-40044r6'></a><span class='ecrm-0500'>6</span><span id='textcolor1344'><span class='ectt-0800'> * Disables page protection at a processor level by changing the 16th bit</span></span>
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+<a id='x1-40046r7'></a><span class='ecrm-0500'>7</span><span id='textcolor1345'><span class='ectt-0800'> * in the cr0 register (could be Intel specific).</span></span>
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+<a id='x1-40048r8'></a><span class='ecrm-0500'>8</span><span id='textcolor1346'><span class='ectt-0800'> *</span></span>
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+<a id='x1-40050r9'></a><span class='ecrm-0500'>9</span><span id='textcolor1347'><span class='ectt-0800'> * Based on example by Peter Jay Salzman and</span></span>
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+<a id='x1-40052r10'></a><span class='ecrm-0500'>10</span><span id='textcolor1348'><span class='ectt-0800'> * https://bbs.archlinux.org/viewtopic.php?id=139406</span></span>
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+<a id='x1-40054r11'></a><span class='ecrm-0500'>11</span><span id='textcolor1349'><span class='ectt-0800'> */</span></span>
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+<a id='x1-40056r12'></a><span class='ecrm-0500'>12</span>
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+<a id='x1-40058r13'></a><span class='ecrm-0500'>13</span><span id='textcolor1350'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1351'><span class='ectt-0800'><linux/delay.h></span></span>
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+<a id='x1-40060r14'></a><span class='ecrm-0500'>14</span><span id='textcolor1352'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1353'><span class='ectt-0800'><linux/kernel.h></span></span>
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+<a id='x1-40062r15'></a><span class='ecrm-0500'>15</span><span id='textcolor1354'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1355'><span class='ectt-0800'><linux/module.h></span></span>
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+<a id='x1-40064r16'></a><span class='ecrm-0500'>16</span><span id='textcolor1356'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1357'><span class='ectt-0800'><linux/moduleparam.h> /* which will have params */</span></span>
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+<a id='x1-40066r17'></a><span class='ecrm-0500'>17</span><span id='textcolor1358'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1359'><span class='ectt-0800'><linux/syscalls.h></span></span>
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+<a id='x1-40068r18'></a><span class='ecrm-0500'>18</span><span id='textcolor1360'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1361'><span class='ectt-0800'><linux/unistd.h> /* The list of system calls */</span></span>
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+<a id='x1-40070r19'></a><span class='ecrm-0500'>19</span>
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+<a id='x1-40072r20'></a><span class='ecrm-0500'>20</span><span id='textcolor1362'><span class='ectt-0800'>/* For the current (process) structure, we need this to know who the</span></span>
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+<a id='x1-40074r21'></a><span class='ecrm-0500'>21</span><span id='textcolor1363'><span class='ectt-0800'> * current user is.</span></span>
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+<a id='x1-40076r22'></a><span class='ecrm-0500'>22</span><span id='textcolor1364'><span class='ectt-0800'> */</span></span>
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+<a id='x1-40078r23'></a><span class='ecrm-0500'>23</span><span id='textcolor1365'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1366'><span class='ectt-0800'><linux/sched.h></span></span>
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+<a id='x1-40080r24'></a><span class='ecrm-0500'>24</span><span id='textcolor1367'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor1368'><span class='ectt-0800'><linux/uaccess.h></span></span>
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+<a id='x1-40082r25'></a><span class='ecrm-0500'>25</span>
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+<a id='x1-40084r26'></a><span class='ecrm-0500'>26</span><span id='textcolor1369'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor1370'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> **sys_call_table;</span>
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+<a id='x1-40086r27'></a><span class='ecrm-0500'>27</span><span id='textcolor1371'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor1372'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> original_cr0;</span>
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+<a id='x1-40088r28'></a><span class='ecrm-0500'>28</span>
|
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|
+<a id='x1-40090r29'></a><span class='ecrm-0500'>29</span><span id='textcolor1373'><span class='ectt-0800'>/* UID we want to spy on - will be filled from the command line. */</span></span>
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+<a id='x1-40092r30'></a><span class='ecrm-0500'>30</span><span id='textcolor1374'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor1375'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> uid;</span>
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|
+<a id='x1-40094r31'></a><span class='ecrm-0500'>31</span><span class='ectt-0800'>module_param(uid, </span><span id='textcolor1376'><span class='ectt-0800'>int</span></span><span class='ectt-0800'>, 0644);</span>
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|
+<a id='x1-40096r32'></a><span class='ecrm-0500'>32</span>
|
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+<a id='x1-40098r33'></a><span class='ecrm-0500'>33</span><span id='textcolor1377'><span class='ectt-0800'>/* A pointer to the original system call. The reason we keep this, rather</span></span>
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+<a id='x1-40100r34'></a><span class='ecrm-0500'>34</span><span id='textcolor1378'><span class='ectt-0800'> * than call the original function (sys_open), is because somebody else</span></span>
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+<a id='x1-40102r35'></a><span class='ecrm-0500'>35</span><span id='textcolor1379'><span class='ectt-0800'> * might have replaced the system call before us. Note that this is not</span></span>
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+<a id='x1-40104r36'></a><span class='ecrm-0500'>36</span><span id='textcolor1380'><span class='ectt-0800'> * 100% safe, because if another module replaced sys_open before us,</span></span>
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+<a id='x1-40106r37'></a><span class='ecrm-0500'>37</span><span id='textcolor1381'><span class='ectt-0800'> * then when we are inserted, we will call the function in that module -</span></span>
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+<a id='x1-40108r38'></a><span class='ecrm-0500'>38</span><span id='textcolor1382'><span class='ectt-0800'> * and it might be removed before we are.</span></span>
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+<a id='x1-40110r39'></a><span class='ecrm-0500'>39</span><span id='textcolor1383'><span class='ectt-0800'> *</span></span>
|
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+<a id='x1-40112r40'></a><span class='ecrm-0500'>40</span><span id='textcolor1384'><span class='ectt-0800'> * Another reason for this is that we can not get sys_open.</span></span>
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+<a id='x1-40114r41'></a><span class='ecrm-0500'>41</span><span id='textcolor1385'><span class='ectt-0800'> * It is a static variable, so it is not exported.</span></span>
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+<a id='x1-40116r42'></a><span class='ecrm-0500'>42</span><span id='textcolor1386'><span class='ectt-0800'> */</span></span>
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+<a id='x1-40118r43'></a><span class='ecrm-0500'>43</span><span class='ectt-0800'>asmlinkage int (*original_call)(</span><span id='textcolor1387'><span class='ectt-0800'>const</span></span><span class='ectt-0800'> </span><span id='textcolor1388'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> *, </span><span id='textcolor1389'><span class='ectt-0800'>int</span></span><span class='ectt-0800'>, </span><span id='textcolor1390'><span class='ectt-0800'>int</span></span><span class='ectt-0800'>);</span>
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+<a id='x1-40120r44'></a><span class='ecrm-0500'>44</span>
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+<a id='x1-40122r45'></a><span class='ecrm-0500'>45</span><span id='textcolor1391'><span class='ectt-0800'>/* The function we will replace sys_open (the function called when you</span></span>
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+<a id='x1-40124r46'></a><span class='ecrm-0500'>46</span><span id='textcolor1392'><span class='ectt-0800'> * call the open system call) with. To find the exact prototype, with</span></span>
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+<a id='x1-40126r47'></a><span class='ecrm-0500'>47</span><span id='textcolor1393'><span class='ectt-0800'> * the number and type of arguments, we find the original function first</span></span>
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+<a id='x1-40128r48'></a><span class='ecrm-0500'>48</span><span id='textcolor1394'><span class='ectt-0800'> * (it is at fs/open.c).</span></span>
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+<a id='x1-40130r49'></a><span class='ecrm-0500'>49</span><span id='textcolor1395'><span class='ectt-0800'> *</span></span>
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+<a id='x1-40132r50'></a><span class='ecrm-0500'>50</span><span id='textcolor1396'><span class='ectt-0800'> * In theory, this means that we are tied to the current version of the</span></span>
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+<a id='x1-40134r51'></a><span class='ecrm-0500'>51</span><span id='textcolor1397'><span class='ectt-0800'> * kernel. In practice, the system calls almost never change (it would</span></span>
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+<a id='x1-40136r52'></a><span class='ecrm-0500'>52</span><span id='textcolor1398'><span class='ectt-0800'> * wreck havoc and require programs to be recompiled, since the system</span></span>
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+<a id='x1-40138r53'></a><span class='ecrm-0500'>53</span><span id='textcolor1399'><span class='ectt-0800'> * calls are the interface between the kernel and the processes).</span></span>
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+<a id='x1-40140r54'></a><span class='ecrm-0500'>54</span><span id='textcolor1400'><span class='ectt-0800'> */</span></span>
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+<a id='x1-40142r55'></a><span class='ecrm-0500'>55</span><span class='ectt-0800'>asmlinkage </span><span id='textcolor1401'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> our_sys_open(</span><span id='textcolor1402'><span class='ectt-0800'>const</span></span><span class='ectt-0800'> </span><span id='textcolor1403'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> *filename, </span><span id='textcolor1404'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> flags, </span><span id='textcolor1405'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> mode)</span>
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+<a id='x1-40144r56'></a><span class='ecrm-0500'>56</span><span class='ectt-0800'>{</span>
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+<a id='x1-40146r57'></a><span class='ecrm-0500'>57</span><span class='ectt-0800'> </span><span id='textcolor1406'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> i = 0;</span>
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+<a id='x1-40148r58'></a><span class='ecrm-0500'>58</span><span class='ectt-0800'> </span><span id='textcolor1407'><span class='ectt-0800'>char</span></span><span class='ectt-0800'> ch;</span>
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+<a id='x1-40150r59'></a><span class='ecrm-0500'>59</span>
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+<a id='x1-40152r60'></a><span class='ecrm-0500'>60</span><span class='ectt-0800'> </span><span id='textcolor1408'><span class='ectt-0800'>/* Report the file, if relevant */</span></span>
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+<a id='x1-40154r61'></a><span class='ecrm-0500'>61</span><span class='ectt-0800'> pr_info(</span><span id='textcolor1409'><span class='ectt-0800'>"Opened file by %d: "</span></span><span class='ectt-0800'>, uid);</span>
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+<a id='x1-40156r62'></a><span class='ecrm-0500'>62</span><span class='ectt-0800'> </span><span id='textcolor1410'><span class='ectt-0800'>do</span></span><span class='ectt-0800'> {</span>
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+<a id='x1-40158r63'></a><span class='ecrm-0500'>63</span><span class='ectt-0800'> get_user(ch, filename + i);</span>
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+<a id='x1-40160r64'></a><span class='ecrm-0500'>64</span><span class='ectt-0800'> i++;</span>
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+<a id='x1-40162r65'></a><span class='ecrm-0500'>65</span><span class='ectt-0800'> pr_info(</span><span id='textcolor1411'><span class='ectt-0800'>"%c"</span></span><span class='ectt-0800'>, ch);</span>
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+<a id='x1-40164r66'></a><span class='ecrm-0500'>66</span><span class='ectt-0800'> } </span><span id='textcolor1412'><span class='ectt-0800'>while</span></span><span class='ectt-0800'> (ch != 0);</span>
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+<a id='x1-40166r67'></a><span class='ecrm-0500'>67</span><span class='ectt-0800'> pr_info(</span><span id='textcolor1413'><span class='ectt-0800'>"</span></span><span id='textcolor1414'><span class='ectt-0800'>\n</span></span><span id='textcolor1415'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
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+<a id='x1-40168r68'></a><span class='ecrm-0500'>68</span>
|
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|
+<a id='x1-40170r69'></a><span class='ecrm-0500'>69</span><span class='ectt-0800'> </span><span id='textcolor1416'><span class='ectt-0800'>/* Call the original sys_open - otherwise, we lose the ability to</span></span>
|
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+<a id='x1-40172r70'></a><span class='ecrm-0500'>70</span><span id='textcolor1417'><span class='ectt-0800'> * open files.</span></span>
|
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+<a id='x1-40174r71'></a><span class='ecrm-0500'>71</span><span id='textcolor1418'><span class='ectt-0800'> */</span></span>
|
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|
+<a id='x1-40176r72'></a><span class='ecrm-0500'>72</span><span class='ectt-0800'> </span><span id='textcolor1419'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> original_call(filename, flags, mode);</span>
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+<a id='x1-40178r73'></a><span class='ecrm-0500'>73</span><span class='ectt-0800'>}</span>
|
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+<a id='x1-40180r74'></a><span class='ecrm-0500'>74</span>
|
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|
+<a id='x1-40182r75'></a><span class='ecrm-0500'>75</span><span id='textcolor1420'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor1421'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor1422'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> **aquire_sys_call_table(</span><span id='textcolor1423'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
|
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+<a id='x1-40184r76'></a><span class='ecrm-0500'>76</span><span class='ectt-0800'>{</span>
|
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|
+<a id='x1-40186r77'></a><span class='ecrm-0500'>77</span><span class='ectt-0800'> </span><span id='textcolor1424'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor1425'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> </span><span id='textcolor1426'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> offset = PAGE_OFFSET;</span>
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+<a id='x1-40188r78'></a><span class='ecrm-0500'>78</span><span class='ectt-0800'> </span><span id='textcolor1427'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor1428'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> **sct;</span>
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|
+<a id='x1-40190r79'></a><span class='ecrm-0500'>79</span>
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+<a id='x1-40192r80'></a><span class='ecrm-0500'>80</span><span class='ectt-0800'> </span><span id='textcolor1429'><span class='ectt-0800'>while</span></span><span class='ectt-0800'> (offset < ULLONG_MAX) {</span>
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|
+<a id='x1-40194r81'></a><span class='ecrm-0500'>81</span><span class='ectt-0800'> sct = (</span><span id='textcolor1430'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor1431'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> **) offset;</span>
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+<a id='x1-40196r82'></a><span class='ecrm-0500'>82</span>
|
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|
+<a id='x1-40198r83'></a><span class='ecrm-0500'>83</span><span class='ectt-0800'> </span><span id='textcolor1432'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (sct[__NR_close] == (</span><span id='textcolor1433'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor1434'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> *) ksys_close)</span>
|
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|
+<a id='x1-40200r84'></a><span class='ecrm-0500'>84</span><span class='ectt-0800'> </span><span id='textcolor1435'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> sct;</span>
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+<a id='x1-40202r85'></a><span class='ecrm-0500'>85</span>
|
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|
+<a id='x1-40204r86'></a><span class='ecrm-0500'>86</span><span class='ectt-0800'> offset += </span><span id='textcolor1436'><span class='ectt-0800'>sizeof</span></span><span class='ectt-0800'>(</span><span id='textcolor1437'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> *);</span>
|
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+<a id='x1-40206r87'></a><span class='ecrm-0500'>87</span><span class='ectt-0800'> }</span>
|
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|
+<a id='x1-40208r88'></a><span class='ecrm-0500'>88</span>
|
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|
+<a id='x1-40210r89'></a><span class='ecrm-0500'>89</span><span class='ectt-0800'> </span><span id='textcolor1438'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> NULL;</span>
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+<a id='x1-40212r90'></a><span class='ecrm-0500'>90</span><span class='ectt-0800'>}</span>
|
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|
+<a id='x1-40214r91'></a><span class='ecrm-0500'>91</span>
|
|
|
+<a id='x1-40216r92'></a><span class='ecrm-0500'>92</span><span id='textcolor1439'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor1440'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> __init syscall_start(</span><span id='textcolor1441'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
|
|
|
+<a id='x1-40218r93'></a><span class='ecrm-0500'>93</span><span class='ectt-0800'>{</span>
|
|
|
+<a id='x1-40220r94'></a><span class='ecrm-0500'>94</span><span class='ectt-0800'> </span><span id='textcolor1442'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (!(sys_call_table = aquire_sys_call_table()))</span>
|
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|
+<a id='x1-40222r95'></a><span class='ecrm-0500'>95</span><span class='ectt-0800'> </span><span id='textcolor1443'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> -1;</span>
|
|
|
+<a id='x1-40224r96'></a><span class='ecrm-0500'>96</span>
|
|
|
+<a id='x1-40226r97'></a><span class='ecrm-0500'>97</span><span class='ectt-0800'> original_cr0 = read_cr0();</span>
|
|
|
+<a id='x1-40228r98'></a><span class='ecrm-0500'>98</span>
|
|
|
+<a id='x1-40230r99'></a><span class='ecrm-0500'>99</span><span class='ectt-0800'> write_cr0(original_cr0 & ~0x00010000);</span>
|
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|
+<a id='x1-40232r100'></a><span class='ecrm-0500'>100</span>
|
|
|
+<a id='x1-40234r101'></a><span class='ecrm-0500'>101</span><span class='ectt-0800'> </span><span id='textcolor1444'><span class='ectt-0800'>/* keep track of the original open function */</span></span>
|
|
|
+<a id='x1-40236r102'></a><span class='ecrm-0500'>102</span><span class='ectt-0800'> original_call = (</span><span id='textcolor1445'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> *) sys_call_table[__NR_open];</span>
|
|
|
+<a id='x1-40238r103'></a><span class='ecrm-0500'>103</span>
|
|
|
+<a id='x1-40240r104'></a><span class='ecrm-0500'>104</span><span class='ectt-0800'> </span><span id='textcolor1446'><span class='ectt-0800'>/* use our open function instead */</span></span>
|
|
|
+<a id='x1-40242r105'></a><span class='ecrm-0500'>105</span><span class='ectt-0800'> sys_call_table[__NR_open] = (</span><span id='textcolor1447'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor1448'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> *) our_sys_open;</span>
|
|
|
+<a id='x1-40244r106'></a><span class='ecrm-0500'>106</span>
|
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|
+<a id='x1-40246r107'></a><span class='ecrm-0500'>107</span><span class='ectt-0800'> write_cr0(original_cr0);</span>
|
|
|
+<a id='x1-40248r108'></a><span class='ecrm-0500'>108</span>
|
|
|
+<a id='x1-40250r109'></a><span class='ecrm-0500'>109</span><span class='ectt-0800'> pr_info(</span><span id='textcolor1449'><span class='ectt-0800'>"Spying on UID:%d</span></span><span id='textcolor1450'><span class='ectt-0800'>\n</span></span><span id='textcolor1451'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>, uid);</span>
|
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+<a id='x1-40252r110'></a><span class='ecrm-0500'>110</span>
|
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|
+<a id='x1-40254r111'></a><span class='ecrm-0500'>111</span><span class='ectt-0800'> </span><span id='textcolor1452'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> 0;</span>
|
|
|
+<a id='x1-40256r112'></a><span class='ecrm-0500'>112</span><span class='ectt-0800'>}</span>
|
|
|
+<a id='x1-40258r113'></a><span class='ecrm-0500'>113</span>
|
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|
+<a id='x1-40260r114'></a><span class='ecrm-0500'>114</span><span id='textcolor1453'><span class='ectt-0800'>static</span></span><span class='ectt-0800'> </span><span id='textcolor1454'><span class='ectt-0800'>void</span></span><span class='ectt-0800'> __exit syscall_end(</span><span id='textcolor1455'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
|
|
|
+<a id='x1-40262r115'></a><span class='ecrm-0500'>115</span><span class='ectt-0800'>{</span>
|
|
|
+<a id='x1-40264r116'></a><span class='ecrm-0500'>116</span><span class='ectt-0800'> </span><span id='textcolor1456'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (!sys_call_table)</span>
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|
|
+<a id='x1-40266r117'></a><span class='ecrm-0500'>117</span><span class='ectt-0800'> </span><span id='textcolor1457'><span class='ectt-0800'>return</span></span><span class='ectt-0800'>;</span>
|
|
|
+<a id='x1-40268r118'></a><span class='ecrm-0500'>118</span>
|
|
|
+<a id='x1-40270r119'></a><span class='ecrm-0500'>119</span><span class='ectt-0800'> </span><span id='textcolor1458'><span class='ectt-0800'>/* Return the system call back to normal */</span></span>
|
|
|
+<a id='x1-40272r120'></a><span class='ecrm-0500'>120</span><span class='ectt-0800'> </span><span id='textcolor1459'><span class='ectt-0800'>if</span></span><span class='ectt-0800'> (sys_call_table[__NR_open] != (</span><span id='textcolor1460'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor1461'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> *) our_sys_open) {</span>
|
|
|
+<a id='x1-40274r121'></a><span class='ecrm-0500'>121</span><span class='ectt-0800'> pr_alert(</span><span id='textcolor1462'><span class='ectt-0800'>"Somebody else also played with the "</span></span><span class='ectt-0800'>);</span>
|
|
|
+<a id='x1-40276r122'></a><span class='ecrm-0500'>122</span><span class='ectt-0800'> pr_alert(</span><span id='textcolor1463'><span class='ectt-0800'>"open system call</span></span><span id='textcolor1464'><span class='ectt-0800'>\n</span></span><span id='textcolor1465'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
|
+<a id='x1-40278r123'></a><span class='ecrm-0500'>123</span><span class='ectt-0800'> pr_alert(</span><span id='textcolor1466'><span class='ectt-0800'>"The system may be left in "</span></span><span class='ectt-0800'>);</span>
|
|
|
+<a id='x1-40280r124'></a><span class='ecrm-0500'>124</span><span class='ectt-0800'> pr_alert(</span><span id='textcolor1467'><span class='ectt-0800'>"an unstable state.</span></span><span id='textcolor1468'><span class='ectt-0800'>\n</span></span><span id='textcolor1469'><span class='ectt-0800'>"</span></span><span class='ectt-0800'>);</span>
|
|
|
+<a id='x1-40282r125'></a><span class='ecrm-0500'>125</span><span class='ectt-0800'> }</span>
|
|
|
+<a id='x1-40284r126'></a><span class='ecrm-0500'>126</span>
|
|
|
+<a id='x1-40286r127'></a><span class='ecrm-0500'>127</span><span class='ectt-0800'> write_cr0(original_cr0 & ~0x00010000);</span>
|
|
|
+<a id='x1-40288r128'></a><span class='ecrm-0500'>128</span><span class='ectt-0800'> sys_call_table[__NR_open] = (</span><span id='textcolor1470'><span class='ectt-0800'>unsigned</span></span><span class='ectt-0800'> </span><span id='textcolor1471'><span class='ectt-0800'>long</span></span><span class='ectt-0800'> *) original_call;</span>
|
|
|
+<a id='x1-40290r129'></a><span class='ecrm-0500'>129</span><span class='ectt-0800'> write_cr0(original_cr0);</span>
|
|
|
+<a id='x1-40292r130'></a><span class='ecrm-0500'>130</span>
|
|
|
+<a id='x1-40294r131'></a><span class='ecrm-0500'>131</span><span class='ectt-0800'> msleep(2000);</span>
|
|
|
+<a id='x1-40296r132'></a><span class='ecrm-0500'>132</span><span class='ectt-0800'>}</span>
|
|
|
+<a id='x1-40298r133'></a><span class='ecrm-0500'>133</span>
|
|
|
+<a id='x1-40300r134'></a><span class='ecrm-0500'>134</span><span class='ectt-0800'>module_init(syscall_start);</span>
|
|
|
+<a id='x1-40302r135'></a><span class='ecrm-0500'>135</span><span class='ectt-0800'>module_exit(syscall_end);</span>
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|
|
+<a id='x1-40304r136'></a><span class='ecrm-0500'>136</span>
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+<a id='x1-40306r137'></a><span class='ecrm-0500'>137</span><span class='ectt-0800'>MODULE_LICENSE(</span><span id='textcolor1472'><span class='ectt-0800'>"GPL"</span></span><span class='ectt-0800'>);</span></pre>
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<h3 class='sectionHead' id='blocking-processes-and-threads'><span class='titlemark'>0.11 </span> <a id='x1-410000.11'></a>Blocking Processes and threads</h3>
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