|
|
@@ -18,7 +18,7 @@
|
|
|
|
|
|
<h2 class='titleHead'>The Linux Kernel Module Programming Guide</h2>
|
|
|
<div class='author'><span class='ecrm-1200'>Peter Jay Salzman, Michael Burian, Ori Pomerantz, Bob Mottram, Jim Huang</span></div><br />
|
|
|
-<div class='date'><span class='ecrm-1200'>March 9, 2022</span></div>
|
|
|
+<div class='date'><span class='ecrm-1200'>March 16, 2022</span></div>
|
|
|
|
|
|
|
|
|
|
|
|
@@ -1079,12 +1079,13 @@ code.
|
|
|
</p><!-- l. 706 --><p class='indent'> Kernel modules are different here, too. In the hello world
|
|
|
example, you might have noticed that we used a function,
|
|
|
<code> <span class='ectt-1000'>pr_info()</span>
|
|
|
-</code> but did not include a standard I/O library. That is because modules are object files whose symbols
|
|
|
-get resolved upon <code> <span class='ectt-1000'>insmod</span>
|
|
|
-</code>’ing. The definition for the symbols comes from the kernel itself; the only
|
|
|
-external functions you can use are the ones provided by the kernel. If you’re
|
|
|
-curious about what symbols have been exported by your kernel, take a look at
|
|
|
-<span class='obeylines-h'><span class='verb'><span class='ectt-1000'>/proc/kallsyms</span></span></span>.
|
|
|
+</code> but did not include a standard I/O library. That is because
|
|
|
+modules are object files whose symbols get resolved upon running
|
|
|
+<code> <span class='ectt-1000'>insmod</span>
|
|
|
+</code> or <code> <span class='ectt-1000'>modprobe</span>
|
|
|
+</code>. The definition for the symbols comes from the kernel itself; the only external
|
|
|
+functions you can use are the ones provided by the kernel. If you’re curious about
|
|
|
+what symbols have been exported by your kernel, take a look at <span class='obeylines-h'><span class='verb'><span class='ectt-1000'>/proc/kallsyms</span></span></span>.
|
|
|
</p><!-- l. 711 --><p class='indent'> One point to keep in mind is the difference between library functions and system
|
|
|
calls. Library functions are higher level, run completely in user space and
|
|
|
provide a more convenient interface for the programmer to the functions
|
|
|
@@ -1103,13 +1104,13 @@ data into strings and write the string data using the low-level system call
|
|
|
</code>? It is easy! Compile the following program:
|
|
|
</p><!-- l. 1 --><p class='indent'>
|
|
|
</p>
|
|
|
- <pre class='fancyvrb' id='fancyvrb35'><a id='x1-21016r1'></a><span class='ecrm-0500'>1</span><span id='textcolor259'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor260'><span class='ectt-0800'><stdio.h></span></span>
|
|
|
-<a id='x1-21018r2'></a><span class='ecrm-0500'>2</span>
|
|
|
-<a id='x1-21020r3'></a><span class='ecrm-0500'>3</span><span id='textcolor261'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> main(</span><span id='textcolor262'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
|
|
|
-<a id='x1-21022r4'></a><span class='ecrm-0500'>4</span><span class='ectt-0800'>{</span>
|
|
|
-<a id='x1-21024r5'></a><span class='ecrm-0500'>5</span><span class='ectt-0800'> printf(</span><span id='textcolor263'><span class='ectt-0800'>"hello"</span></span><span class='ectt-0800'>);</span>
|
|
|
-<a id='x1-21026r6'></a><span class='ecrm-0500'>6</span><span class='ectt-0800'> </span><span id='textcolor264'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> 0;</span>
|
|
|
-<a id='x1-21028r7'></a><span class='ecrm-0500'>7</span><span class='ectt-0800'>}</span></pre>
|
|
|
+ <pre class='fancyvrb' id='fancyvrb35'><a id='x1-21017r1'></a><span class='ecrm-0500'>1</span><span id='textcolor259'><span class='ectt-0800'>#include</span></span><span class='ectt-0800'> </span><span id='textcolor260'><span class='ectt-0800'><stdio.h></span></span>
|
|
|
+<a id='x1-21019r2'></a><span class='ecrm-0500'>2</span>
|
|
|
+<a id='x1-21021r3'></a><span class='ecrm-0500'>3</span><span id='textcolor261'><span class='ectt-0800'>int</span></span><span class='ectt-0800'> main(</span><span id='textcolor262'><span class='ectt-0800'>void</span></span><span class='ectt-0800'>)</span>
|
|
|
+<a id='x1-21023r4'></a><span class='ecrm-0500'>4</span><span class='ectt-0800'>{</span>
|
|
|
+<a id='x1-21025r5'></a><span class='ecrm-0500'>5</span><span class='ectt-0800'> printf(</span><span id='textcolor263'><span class='ectt-0800'>"hello"</span></span><span class='ectt-0800'>);</span>
|
|
|
+<a id='x1-21027r6'></a><span class='ecrm-0500'>6</span><span class='ectt-0800'> </span><span id='textcolor264'><span class='ectt-0800'>return</span></span><span class='ectt-0800'> 0;</span>
|
|
|
+<a id='x1-21029r7'></a><span class='ecrm-0500'>7</span><span class='ectt-0800'>}</span></pre>
|
|
|
<!-- l. 729 --><p class='indent'> with <code> <span class='ectt-1000'>gcc -Wall -o hello hello.c</span>
|
|
|
</code>. Run the executable with <code> <span class='ectt-1000'>strace ./hello</span>
|
|
|
</code>. Are you impressed? Every line you see corresponds to a system call. <a href='https://strace.io/'>strace</a> is a
|
jserv