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@@ -686,7 +686,7 @@ parameters: a variable name and a free form string describing that variable.
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</p>
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<pre class='verbatim' id='verbatim-2'>
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$ sudo insmod hello-5.ko mystring="bebop" myintarray=-1
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-$ dmesg -t | tail -7
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+$ sudo dmesg -t | tail -7
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myshort is a short integer: 1
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myint is an integer: 420
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mylong is a long integer: 9999
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@@ -696,11 +696,11 @@ myintarray[1] = 420
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got 1 arguments for myintarray.
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$ sudo rmmod hello-5
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-$ dmesg -t | tail -1
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+$ sudo dmesg -t | tail -1
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Goodbye, world 5
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$ sudo insmod hello-5.ko mystring="supercalifragilisticexpialidocious" myintarray=-1,-1
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-$ dmesg -t | tail -7
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+$ sudo dmesg -t | tail -7
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myshort is a short integer: 1
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myint is an integer: 420
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mylong is a long integer: 9999
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@@ -710,7 +710,7 @@ myintarray[1] = -1
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got 2 arguments for myintarray.
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$ sudo rmmod hello-5
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-$ dmesg -t | tail -1
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+$ sudo dmesg -t | tail -1
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Goodbye, world 5
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$ sudo insmod hello-5.ko mylong=hello
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@@ -5047,21 +5047,20 @@ demonstration of how to calculate a sha256 hash within a kernel module.
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<a id='x1-60124r62'></a><span class='ecrm-0500'>62</span>
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<a id='x1-60126r63'></a><span class='ecrm-0500'>63</span><span class='ectt-0800'>MODULE_DESCRIPTION(</span><span id='textcolor2613'><span class='ectt-0800'>"sha256 hash test"</span></span><span class='ectt-0800'>);</span>
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<a id='x1-60128r64'></a><span class='ecrm-0500'>64</span><span class='ectt-0800'>MODULE_LICENSE(</span><span id='textcolor2614'><span class='ectt-0800'>"GPL"</span></span><span class='ectt-0800'>);</span></pre>
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-<!-- l. 1687 --><p class='indent'> Make and install the module:
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+<!-- l. 1687 --><p class='indent'> Install the module:
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</p><!-- l. 1 --><p class='indent'>
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</p>
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- <pre class='fancyvrb' id='fancyvrb70'><a id='x1-60133r1'></a><span class='ecrm-0500'>1</span><span class='ectt-1000'>make</span>
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-<a id='x1-60135r2'></a><span class='ecrm-0500'>2</span><span class='ectt-1000'>sudo insmod cryptosha256.ko</span>
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-<a id='x1-60137r3'></a><span class='ecrm-0500'>3</span><span class='ectt-1000'>dmesg</span></pre>
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-<!-- l. 1695 --><p class='indent'> And you should see that the hash was calculated for the test string.
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-</p><!-- l. 1697 --><p class='indent'> Finally, remove the test module:
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+ <pre class='fancyvrb' id='fancyvrb70'><a id='x1-60132r1'></a><span class='ecrm-0500'>1</span><span class='ectt-1000'>sudo insmod cryptosha256.ko</span>
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+<a id='x1-60134r2'></a><span class='ecrm-0500'>2</span><span class='ectt-1000'>sudo dmesg</span></pre>
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+<!-- l. 1694 --><p class='indent'> And you should see that the hash was calculated for the test string.
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+</p><!-- l. 1696 --><p class='indent'> Finally, remove the test module:
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</p><!-- l. 1 --><p class='indent'>
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</p>
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- <pre class='fancyvrb' id='fancyvrb71'><a id='x1-60140r1'></a><span class='ecrm-0500'>1</span><span class='ectt-1000'>sudo rmmod cryptosha256</span></pre>
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-<!-- l. 1703 --><p class='noindent'>
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+ <pre class='fancyvrb' id='fancyvrb71'><a id='x1-60137r1'></a><span class='ecrm-0500'>1</span><span class='ectt-1000'>sudo rmmod cryptosha256</span></pre>
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+<!-- l. 1702 --><p class='noindent'>
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</p>
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<h4 class='subsectionHead' id='symmetric-key-encryption'><span class='titlemark'>16.2 </span> <a id='x1-6100016.2'></a>Symmetric key encryption</h4>
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-<!-- l. 1705 --><p class='noindent'>Here is an example of symmetrically encrypting a string using the AES algorithm
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+<!-- l. 1704 --><p class='noindent'>Here is an example of symmetrically encrypting a string using the AES algorithm
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and a password.
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</p><!-- l. 1 --><p class='indent'>
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@@ -5266,10 +5265,10 @@ and a password.
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<a id='x1-61392r196'></a><span class='ecrm-0500'>196</span>
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<a id='x1-61394r197'></a><span class='ecrm-0500'>197</span><span class='ectt-0800'>MODULE_DESCRIPTION(</span><span id='textcolor2766'><span class='ectt-0800'>"Symmetric key encryption example"</span></span><span class='ectt-0800'>);</span>
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<a id='x1-61396r198'></a><span class='ecrm-0500'>198</span><span class='ectt-0800'>MODULE_LICENSE(</span><span id='textcolor2767'><span class='ectt-0800'>"GPL"</span></span><span class='ectt-0800'>);</span></pre>
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-<!-- l. 1709 --><p class='noindent'>
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+<!-- l. 1708 --><p class='noindent'>
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</p>
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<h3 class='sectionHead' id='standardizing-the-interfaces-the-device-model'><span class='titlemark'>17 </span> <a id='x1-6200017'></a>Standardizing the interfaces: The Device Model</h3>
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-<!-- l. 1711 --><p class='noindent'>Up to this point we have seen all kinds of modules doing all kinds of things, but there
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+<!-- l. 1710 --><p class='noindent'>Up to this point we have seen all kinds of modules doing all kinds of things, but there
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was no consistency in their interfaces with the rest of the kernel. To impose some
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consistency such that there is at minimum a standardized way to start, suspend and
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resume a device a device model was added. An example is shown below, and you can
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@@ -5376,13 +5375,13 @@ functions.
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<a id='x1-62194r97'></a><span class='ecrm-0500'>97</span>
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<a id='x1-62196r98'></a><span class='ecrm-0500'>98</span><span class='ectt-0800'>MODULE_LICENSE(</span><span id='textcolor2842'><span class='ectt-0800'>"GPL"</span></span><span class='ectt-0800'>);</span>
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<a id='x1-62198r99'></a><span class='ecrm-0500'>99</span><span class='ectt-0800'>MODULE_DESCRIPTION(</span><span id='textcolor2843'><span class='ectt-0800'>"Linux Device Model example"</span></span><span class='ectt-0800'>);</span></pre>
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-<!-- l. 1717 --><p class='noindent'>
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+<!-- l. 1716 --><p class='noindent'>
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</p>
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<h3 class='sectionHead' id='optimizations'><span class='titlemark'>18 </span> <a id='x1-6300018'></a>Optimizations</h3>
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-<!-- l. 1719 --><p class='noindent'>
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+<!-- l. 1718 --><p class='noindent'>
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</p>
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<h4 class='subsectionHead' id='likely-and-unlikely-conditions'><span class='titlemark'>18.1 </span> <a id='x1-6400018.1'></a>Likely and Unlikely conditions</h4>
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-<!-- l. 1721 --><p class='noindent'>Sometimes you might want your code to run as quickly as possible,
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+<!-- l. 1720 --><p class='noindent'>Sometimes you might want your code to run as quickly as possible,
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especially if it is handling an interrupt or doing something which might
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cause noticeable latency. If your code contains boolean conditions and if
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you know that the conditions are almost always likely to evaluate as either
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@@ -5404,35 +5403,35 @@ to succeed.
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-<!-- l. 1735 --><p class='indent'> When the <code> <span class='ectt-1000'>unlikely</span>
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+<!-- l. 1734 --><p class='indent'> When the <code> <span class='ectt-1000'>unlikely</span>
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</code> macro is used, the compiler alters its machine instruction output, so that it
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continues along the false branch and only jumps if the condition is true. That
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avoids flushing the processor pipeline. The opposite happens if you use the
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<code> <span class='ectt-1000'>likely</span>
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</code> macro.
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-</p><!-- l. 1739 --><p class='noindent'>
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+</p><!-- l. 1738 --><p class='noindent'>
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</p>
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<h3 class='sectionHead' id='common-pitfalls'><span class='titlemark'>19 </span> <a id='x1-6500019'></a>Common Pitfalls</h3>
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-<!-- l. 1742 --><p class='noindent'>
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+<!-- l. 1741 --><p class='noindent'>
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</p>
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<h4 class='subsectionHead' id='using-standard-libraries'><span class='titlemark'>19.1 </span> <a id='x1-6600019.1'></a>Using standard libraries</h4>
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-<!-- l. 1744 --><p class='noindent'>You can not do that. In a kernel module, you can only use kernel functions which are
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+<!-- l. 1743 --><p class='noindent'>You can not do that. In a kernel module, you can only use kernel functions which are
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the functions you can see in <span class='obeylines-h'><span class='verb'><span class='ectt-1000'>/proc/kallsyms</span></span></span>.
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-</p><!-- l. 1747 --><p class='noindent'>
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+</p><!-- l. 1746 --><p class='noindent'>
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</p>
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<h4 class='subsectionHead' id='disabling-interrupts'><span class='titlemark'>19.2 </span> <a id='x1-6700019.2'></a>Disabling interrupts</h4>
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-<!-- l. 1749 --><p class='noindent'>You might need to do this for a short time and that is OK, but if you do not enable
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+<!-- l. 1748 --><p class='noindent'>You might need to do this for a short time and that is OK, but if you do not enable
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them afterwards, your system will be stuck and you will have to power it
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off.
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-</p><!-- l. 1751 --><p class='noindent'>
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+</p><!-- l. 1750 --><p class='noindent'>
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</p>
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<h3 class='sectionHead' id='where-to-go-from-here'><span class='titlemark'>20 </span> <a id='x1-6800020'></a>Where To Go From Here?</h3>
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-<!-- l. 1753 --><p class='noindent'>For people seriously interested in kernel programming, I recommend <a href='https://kernelnewbies.org'>kernelnewbies.org</a>
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+<!-- l. 1752 --><p class='noindent'>For people seriously interested in kernel programming, I recommend <a href='https://kernelnewbies.org'>kernelnewbies.org</a>
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and the <a href='https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/Documentation'>Documentation</a> subdirectory within the kernel source code which is not
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always easy to understand but can be a starting point for further investigation. Also,
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as Linus Torvalds said, the best way to learn the kernel is to read the source code
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yourself.
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-</p><!-- l. 1756 --><p class='indent'> If you are interested in more examples of short kernel modules then searching on
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+</p><!-- l. 1755 --><p class='indent'> If you are interested in more examples of short kernel modules then searching on
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sites such as Github and Gitlab is a good way to start, although there is a lot of
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duplication of older LKMPG examples which may not compile with newer kernel
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versions. You will also be able to find examples of the use of kernel modules to attack
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@@ -5442,12 +5441,12 @@ kernel.
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-</p><!-- l. 1759 --><p class='indent'> I hope I have helped you in your quest to become a better programmer, or at
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+</p><!-- l. 1758 --><p class='indent'> I hope I have helped you in your quest to become a better programmer, or at
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least to have fun through technology. And, if you do write useful kernel modules, I
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hope you publish them under the GPL, so I can use them too.
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-</p><!-- l. 1762 --><p class='indent'> If you would like to contribute to this guide or notice anything glaringly wrong,
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+</p><!-- l. 1761 --><p class='indent'> If you would like to contribute to this guide or notice anything glaringly wrong,
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please create an issue at <a class='url' href='https://github.com/sysprog21/lkmpg'><span class='ectt-1000'>https://github.com/sysprog21/lkmpg</span></a>.
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-</p><!-- l. 1764 --><p class='indent'> Happy hacking!
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+</p><!-- l. 1763 --><p class='indent'> Happy hacking!
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</p>
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<div class='footnotes'><!-- l. 1593 --><p class='indent'> <span class='footnote-mark'><a href='#fn1x0-bk' id='fn1x0'><sup class='textsuperscript'>1</sup></a></span><span class='ecrm-0800'>The goal of threaded interrupts is to push more of the work to separate threads, so that the
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</span><span class='ecrm-0800'>minimum needed for acknowledging an interrupt is reduced, and therefore the time spent handling
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jserv