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<div id="isso-root"><div id="isso-227" class="isso-comment isso-no-votes"><div class="avatar"><svg version="1.1" viewBox="0 0 48 48" preserveAspectRatio="xMinYMin meet" shape-rendering="crispEdges" data-hash="4d0a4c8513ba"><rect x="0" y="0" width="56" height="56" style="fill: #f0f0f0"></rect><rect x="4" y="12" width="8" height="8" style="fill: #e279a3"></rect><rect x="36" y="12" width="8" height="8" style="fill: #e279a3"></rect><rect x="12" y="4" width="8" height="8" style="fill: #e279a3"></rect><rect x="28" y="4" width="8" height="8" style="fill: #e279a3"></rect><rect x="12" y="28" width="8" height="8" style="fill: #e279a3"></rect><rect x="28" y="28" width="8" height="8" style="fill: #e279a3"></rect><rect x="12" y="36" width="8" height="8" style="fill: #e279a3"></rect><rect x="28" y="36" width="8" height="8" style="fill: #e279a3"></rect><rect x="20" y="4" width="8" height="8" style="fill: #e279a3"></rect><rect x="20" y="20" width="8" height="8" style="fill: #e279a3"></rect><rect x="20" y="28" width="8" height="8" style="fill: #e279a3"></rect><rect x="20" y="36" width="8" height="8" style="fill: #e279a3"></rect></svg></div><div class="text-wrapper"><div role="meta" class="isso-comment-header"><span class="author">Daniel</span><span class="spacer">•</span><a rel="nofollow" href="#isso-227" class="permalink"><time title="Sat Oct 24 2015 16:16:34 GMT+0200 (Central European Summer Time)" datetime="2015-09-06T14:16:34Z">vor 4 Jahren</time></a><span class="note"></span></div><div class="text"><p></p><p>Hi, thank you for the blog posts, finding them really accessible and interesting.</p><p>The <code>test_long_mode</code> function doesn't look quite right:<br></p><pre><code><br>test_long_mode:<br>  mov eax, 0x80000000     ; Set the A-register to 0x80000000.<br>  cpuid                               ; CPU identification.<br>  cmp eax, 0x80000001     ; Compare the A-register with 0x80000001.<br>  jb .no_long_mode           ; It is less, there is no long mode.<br>  mov eax, 0x80000000     ; Set the A-register to 0x80000000.<br>  cpuid                               ; CPU identification.<br>  cmp eax, 0x80000001     ; Compare the A-register with 0x80000001.<br>  jb .no_long_mode           ; It is less, there is no long mode.<br>  ret<br></code></pre><p><br>^ should probaly be (according to your linked OSDEV page):</p><p></p><pre><code><br>test_long_mode:<br>  mov eax, 0x80000000      ; Set the A-register to 0x80000000.<br>  cpuid                                ; CPU identification.<br>  cmp eax, 0x80000001      ; Compare the A-register with 0x80000001.<br>  jb .no_long_mode            ; It is less, there is no long mode.<br>  mov eax, 0x80000001      ; Set the A-register to 0x80000001.<br>  cpuid                                ; CPU identification.<br>  test edx, 1 &lt;&lt; 29              ; Test if the LM-bit, which is bit 29, is set in the D-register.<br>  jz .no_long_mode             ; They aren't, there is no long mode.<br>  ret<br></code></pre><p></p></div><div class="isso-comment-footer"><span class="votes">0</span><a rel="nofollow" href="#" class="upvote"><!-- Generator: IcoMoon.io --><svg width="16" height="16" viewBox="0 0 32 32" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" fill="gray">
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</a><a rel="nofollow" href="#" class="reply">Antworten</a></div><div class="isso-follow-up"><div id="isso-228" class="isso-comment isso-no-votes"><div class="avatar"><svg version="1.1" viewBox="0 0 48 48" preserveAspectRatio="xMinYMin meet" shape-rendering="crispEdges" data-hash="666df3217240"><rect x="0" y="0" width="56" height="56" style="fill: #f0f0f0"></rect><rect x="4" y="12" width="8" height="8" style="fill: #9abf88"></rect><rect x="36" y="12" width="8" height="8" style="fill: #9abf88"></rect><rect x="4" y="28" width="8" height="8" style="fill: #9abf88"></rect><rect x="36" y="28" width="8" height="8" style="fill: #9abf88"></rect><rect x="4" y="36" width="8" height="8" style="fill: #9abf88"></rect><rect x="36" y="36" width="8" height="8" style="fill: #9abf88"></rect><rect x="12" y="4" width="8" height="8" style="fill: #9abf88"></rect><rect x="28" y="4" width="8" height="8" style="fill: #9abf88"></rect><rect x="12" y="28" width="8" height="8" style="fill: #9abf88"></rect><rect x="28" y="28" width="8" height="8" style="fill: #9abf88"></rect><rect x="20" y="12" width="8" height="8" style="fill: #9abf88"></rect></svg></div><div class="text-wrapper"><div role="meta" class="isso-comment-header"><span class="author">Philipp Oppermann</span><span class="spacer">•</span><a rel="nofollow" href="#isso-228" class="permalink"><time title="Sat Oct 24 2015 17:16:30 GMT+0200 (Central European Summer Time)" datetime="2015-09-06T15:16:30Z">vor 4 Jahren</time></a><span class="note"></span></div><div class="text"><p>You're right, thank you! I created an Github issue and will fix it soon: <a rel="nofollow" href="https://github.com/phil-opp/blog_os/issues/6">https://github.com/phil-opp...</a></p></div><div class="isso-comment-footer"><span class="votes">0</span><a rel="nofollow" href="#" class="upvote"><!-- Generator: IcoMoon.io --><svg width="16" height="16" viewBox="0 0 32 32" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" fill="gray">
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</a><a rel="nofollow" href="#" class="reply">Antworten</a></div><div class="isso-follow-up"></div></div></div><div id="isso-229" class="isso-comment isso-no-votes"><div class="avatar"><svg version="1.1" viewBox="0 0 48 48" preserveAspectRatio="xMinYMin meet" shape-rendering="crispEdges" data-hash="4d0a4c8513ba"><rect x="0" y="0" width="56" height="56" style="fill: #f0f0f0"></rect><rect x="4" y="12" width="8" height="8" style="fill: #e279a3"></rect><rect x="36" y="12" width="8" height="8" style="fill: #e279a3"></rect><rect x="12" y="4" width="8" height="8" style="fill: #e279a3"></rect><rect x="28" y="4" width="8" height="8" style="fill: #e279a3"></rect><rect x="12" y="28" width="8" height="8" style="fill: #e279a3"></rect><rect x="28" y="28" width="8" height="8" style="fill: #e279a3"></rect><rect x="12" y="36" width="8" height="8" style="fill: #e279a3"></rect><rect x="28" y="36" width="8" height="8" style="fill: #e279a3"></rect><rect x="20" y="4" width="8" height="8" style="fill: #e279a3"></rect><rect x="20" y="20" width="8" height="8" style="fill: #e279a3"></rect><rect x="20" y="28" width="8" height="8" style="fill: #e279a3"></rect><rect x="20" y="36" width="8" height="8" style="fill: #e279a3"></rect></svg></div><div class="text-wrapper"><div role="meta" class="isso-comment-header"><span class="author">Daniel Ferguson</span><span class="spacer">•</span><a rel="nofollow" href="#isso-229" class="permalink"><time title="Sun Oct 25 2015 13:37:41 GMT+0100 (Central European Standard Time)" datetime="2015-09-00T12:37:41Z">vor 4 Jahren</time></a><span class="note"></span></div><div class="text"><p>Thank you! For any further issues I run into would you prefer I posted to the github page?</p><p>I ran into another snag, at the end of the paging setup section (just before the GDT section) you state:</p><p>"To test it we execute make run. If the green OK is still printed, we have successfully enabled paging!"</p><p>I'm assuming (based on trying it out) it would not be bootable at that stage, though it may in some way be down to the specifics of my setup or mistakes on my part.</p><p>When run with qemu it repeatedly restarts and doesn't reach an 'OK' boot.<br>Removing the `enable_paging` call allows the OS to boot properly, though the paging will not be set up. Further forwards, once the GDT is implemented, the OS once more boots without a hitch.</p><p>I checked out the repo and stripped out the later steps to compensate for any errors I made in copying.</p><p>Thanks again for these posts.</p></div><div class="isso-comment-footer"><span class="votes">0</span><a rel="nofollow" href="#" class="upvote"><!-- Generator: IcoMoon.io --><svg width="16" height="16" viewBox="0 0 32 32" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" fill="gray">
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</a><a rel="nofollow" href="#" class="reply">Antworten</a></div><div class="isso-follow-up"></div></div></div><div id="isso-230" class="isso-comment isso-no-votes"><div class="avatar"><svg version="1.1" viewBox="0 0 48 48" preserveAspectRatio="xMinYMin meet" shape-rendering="crispEdges" data-hash="666df3217240"><rect x="0" y="0" width="56" height="56" style="fill: #f0f0f0"></rect><rect x="4" y="12" width="8" height="8" style="fill: #9abf88"></rect><rect x="36" y="12" width="8" height="8" style="fill: #9abf88"></rect><rect x="4" y="28" width="8" height="8" style="fill: #9abf88"></rect><rect x="36" y="28" width="8" height="8" style="fill: #9abf88"></rect><rect x="4" y="36" width="8" height="8" style="fill: #9abf88"></rect><rect x="36" y="36" width="8" height="8" style="fill: #9abf88"></rect><rect x="12" y="4" width="8" height="8" style="fill: #9abf88"></rect><rect x="28" y="4" width="8" height="8" style="fill: #9abf88"></rect><rect x="12" y="28" width="8" height="8" style="fill: #9abf88"></rect><rect x="28" y="28" width="8" height="8" style="fill: #9abf88"></rect><rect x="20" y="12" width="8" height="8" style="fill: #9abf88"></rect></svg></div><div class="text-wrapper"><div role="meta" class="isso-comment-header"><span class="author">Philipp Oppermann</span><span class="spacer">•</span><a rel="nofollow" href="#isso-230" class="permalink"><time title="Sun Oct 25 2015 14:35:18 GMT+0100 (Central European Standard Time)" datetime="2015-09-00T13:35:18Z">vor 4 Jahren</time></a><span class="note"></span></div><div class="text"><p>Post issues wherever you want (and thank you for doing it).</p><p>Hmm, I can't reproduce it on my machine. I checked out commit 457a613 (see link below) and it ran without problems. Could you try the code from this commit?</p><p>Link to 457a613: <a rel="nofollow" href="https://github.com/phil-opp/blog_os/tree/457a61341a3b62c9c99981bf2fa90a333aedc928/src/arch/x86_64">https://github.com/phil-opp...</a></p></div><div class="isso-comment-footer"><span class="votes">0</span><a rel="nofollow" href="#" class="upvote"><!-- Generator: IcoMoon.io --><svg width="16" height="16" viewBox="0 0 32 32" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" fill="gray">
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</a><a rel="nofollow" href="#" class="reply">Antworten</a></div><div class="isso-follow-up"></div></div></div></div></div></div><div id="isso-232" class="isso-comment isso-no-votes"><div class="avatar"><svg version="1.1" viewBox="0 0 48 48" preserveAspectRatio="xMinYMin meet" shape-rendering="crispEdges" data-hash="6334312b9f4a"><rect x="0" y="0" width="56" height="56" style="fill: #f0f0f0"></rect><rect x="4" y="4" width="8" height="8" style="fill: #e279a3"></rect><rect x="36" y="4" width="8" height="8" style="fill: #e279a3"></rect><rect x="4" y="12" width="8" height="8" style="fill: #e279a3"></rect><rect x="36" y="12" width="8" height="8" style="fill: #e279a3"></rect><rect x="4" y="20" width="8" height="8" style="fill: #e279a3"></rect><rect x="36" y="20" width="8" height="8" style="fill: #e279a3"></rect><rect x="12" y="4" width="8" height="8" style="fill: #e279a3"></rect><rect x="28" y="4" width="8" height="8" style="fill: #e279a3"></rect><rect x="12" y="12" width="8" height="8" style="fill: #e279a3"></rect><rect x="28" y="12" width="8" height="8" style="fill: #e279a3"></rect><rect x="12" y="20" width="8" height="8" style="fill: #e279a3"></rect><rect x="28" y="20" width="8" height="8" style="fill: #e279a3"></rect><rect x="12" y="28" width="8" height="8" style="fill: #e279a3"></rect><rect x="28" y="28" width="8" height="8" style="fill: #e279a3"></rect><rect x="12" y="36" width="8" height="8" style="fill: #e279a3"></rect><rect x="28" y="36" width="8" height="8" style="fill: #e279a3"></rect><rect x="20" y="12" width="8" height="8" style="fill: #e279a3"></rect><rect x="20" y="36" width="8" height="8" style="fill: #e279a3"></rect></svg></div><div class="text-wrapper"><div role="meta" class="isso-comment-header"><span class="author">emk1024</span><span class="spacer">•</span><a rel="nofollow" href="#isso-232" class="permalink"><time title="Wed Oct 28 2015 23:18:55 GMT+0100 (Central European Standard Time)" datetime="2015-09-03T22:18:55Z">vor 4 Jahren</time></a><span class="note"></span></div><div class="text"><p>This is fun!</p><p>Continuing my saga of trying to get this running under Ubuntu 14.04 LTS on a MacBook Pro, if you find that enabling long paging causes an infinite reboot cycle (triple fault?) in QEMU, then you might want to check your qemu-system-x86_64 version. Version 2.0 will reboot infinitely as soon as you try to turn on paging. Version 2.1.2, however, works fine.</p><p>Is this perhaps a problem with huge pages? Would it help to add another feature test?</p><p>In order to prevent more debugging fun, I've downloaded and built your blog_os repo, and I can now see it print "Hello world", so it should be smooth sailing from here. :-)</p><p>Once again, thank you for a cool series of blog posts! Are there any OS development books that you recommend for ideas on further enhancing this basic system?</p></div><div class="isso-comment-footer"><span class="votes">0</span><a rel="nofollow" href="#" class="upvote"><!-- Generator: IcoMoon.io --><svg width="16" height="16" viewBox="0 0 32 32" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" fill="gray">
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</a><a rel="nofollow" href="#" class="reply">Antworten</a></div><div class="isso-follow-up"></div></div></div><div id="isso-234" class="isso-comment isso-no-votes"><div class="avatar"><svg version="1.1" viewBox="0 0 48 48" preserveAspectRatio="xMinYMin meet" shape-rendering="crispEdges" data-hash="666df3217240"><rect x="0" y="0" width="56" height="56" style="fill: #f0f0f0"></rect><rect x="4" y="12" width="8" height="8" style="fill: #9abf88"></rect><rect x="36" y="12" width="8" height="8" style="fill: #9abf88"></rect><rect x="4" y="28" width="8" height="8" style="fill: #9abf88"></rect><rect x="36" y="28" width="8" height="8" style="fill: #9abf88"></rect><rect x="4" y="36" width="8" height="8" style="fill: #9abf88"></rect><rect x="36" y="36" width="8" height="8" style="fill: #9abf88"></rect><rect x="12" y="4" width="8" height="8" style="fill: #9abf88"></rect><rect x="28" y="4" width="8" height="8" style="fill: #9abf88"></rect><rect x="12" y="28" width="8" height="8" style="fill: #9abf88"></rect><rect x="28" y="28" width="8" height="8" style="fill: #9abf88"></rect><rect x="20" y="12" width="8" height="8" style="fill: #9abf88"></rect></svg></div><div class="text-wrapper"><div role="meta" class="isso-comment-header"><span class="author">Philipp Oppermann</span><span class="spacer">•</span><a rel="nofollow" href="#isso-234" class="permalink"><time title="Thu Oct 29 2015 20:32:02 GMT+0100 (Central European Standard Time)" datetime="2015-09-04T19:32:02Z">vor 4 Jahren</time></a><span class="note"></span></div><div class="text"><p></p><blockquote>Are there any OS development books that you recommend for ideas on further enhancing this basic system?</blockquote><p></p><p>Well, there is the <a rel="nofollow" href="http://pages.cs.wisc.edu/~remzi/OSTEP/">Three Easy Pieces</a> book I linked in the post, which gives a theoretical overview over different OS concepts. Then there's <a rel="nofollow" href="http://littleosbook.github.io">the little book about OS development</a>, which is more practical and contains C example code. Of course there are <a rel="nofollow" href="https://wiki.osdev.org/Books#Operating_Systems">many paid books</a>, too.</p><p>Besides books, the <a rel="nofollow" href="https://wiki.osdev.org/Main_Page">OSDev Wiki</a> is also a good resource for many topics. Looking at the source of e.g. <a rel="nofollow" href="https://github.com/redox-os/redox">Redox</a> can be helpful, too.</p><p>For exotical ideas, I really like the concept of <a rel="nofollow" href="https://en.wikipedia.org/wiki/Phantom_OS">Phantom OS</a> and Rust's memory safety might allow something similar… We'll see ;)</p><p></p></div><div class="isso-comment-footer"><span class="votes">0</span><a rel="nofollow" href="#" class="upvote"><!-- Generator: IcoMoon.io --><svg width="16" height="16" viewBox="0 0 32 32" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" fill="gray">
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</a><a rel="nofollow" href="#" class="reply">Antworten</a></div><div class="isso-follow-up"></div></div></div><div id="isso-235" class="isso-comment isso-no-votes"><div class="avatar"><svg version="1.1" viewBox="0 0 48 48" preserveAspectRatio="xMinYMin meet" shape-rendering="crispEdges" data-hash="795b6c68aba8"><rect x="0" y="0" width="56" height="56" style="fill: #f0f0f0"></rect><rect x="4" y="20" width="8" height="8" style="fill: #9abf88"></rect><rect x="36" y="20" width="8" height="8" style="fill: #9abf88"></rect><rect x="4" y="36" width="8" height="8" style="fill: #9abf88"></rect><rect x="36" y="36" width="8" height="8" style="fill: #9abf88"></rect><rect x="12" y="12" width="8" height="8" style="fill: #9abf88"></rect><rect x="28" y="12" width="8" height="8" style="fill: #9abf88"></rect><rect x="12" y="28" width="8" height="8" style="fill: #9abf88"></rect><rect x="28" y="28" width="8" height="8" style="fill: #9abf88"></rect><rect x="12" y="36" width="8" height="8" style="fill: #9abf88"></rect><rect x="28" y="36" width="8" height="8" style="fill: #9abf88"></rect><rect x="20" y="4" width="8" height="8" style="fill: #9abf88"></rect><rect x="20" y="20" width="8" height="8" style="fill: #9abf88"></rect><rect x="20" y="36" width="8" height="8" style="fill: #9abf88"></rect></svg></div><div class="text-wrapper"><div role="meta" class="isso-comment-header"><span class="author">Tom Smeding</span><span class="spacer">•</span><a rel="nofollow" href="#isso-235" class="permalink"><time title="Thu Oct 29 2015 21:46:13 GMT+0100 (Central European Standard Time)" datetime="2015-09-04T20:46:13Z">vor 4 Jahren</time></a><span class="note"></span></div><div class="text"><p>There's still some text in the article referring to the gigabyte page, like "Now the first gigabyte of our kernel is identity mapped", but otherwise, immense thanks for this article; even though I'm not going to use Rust, these two articles actually got me up and running in long mode *without* hassle!</p></div><div class="isso-comment-footer"><span class="votes">0</span><a rel="nofollow" href="#" class="upvote"><!-- Generator: IcoMoon.io --><svg width="16" height="16" viewBox="0 0 32 32" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" fill="gray">
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</a><a rel="nofollow" href="#" class="reply">Antworten</a></div><div class="isso-follow-up"></div></div></div><div id="isso-237" class="isso-comment isso-no-votes"><div class="avatar"><svg version="1.1" viewBox="0 0 48 48" preserveAspectRatio="xMinYMin meet" shape-rendering="crispEdges" data-hash="795b6c68aba8"><rect x="0" y="0" width="56" height="56" style="fill: #f0f0f0"></rect><rect x="4" y="20" width="8" height="8" style="fill: #9abf88"></rect><rect x="36" y="20" width="8" height="8" style="fill: #9abf88"></rect><rect x="4" y="36" width="8" height="8" style="fill: #9abf88"></rect><rect x="36" y="36" width="8" height="8" style="fill: #9abf88"></rect><rect x="12" y="12" width="8" height="8" style="fill: #9abf88"></rect><rect x="28" y="12" width="8" height="8" style="fill: #9abf88"></rect><rect x="12" y="28" width="8" height="8" style="fill: #9abf88"></rect><rect x="28" y="28" width="8" height="8" style="fill: #9abf88"></rect><rect x="12" y="36" width="8" height="8" style="fill: #9abf88"></rect><rect x="28" y="36" width="8" height="8" style="fill: #9abf88"></rect><rect x="20" y="4" width="8" height="8" style="fill: #9abf88"></rect><rect x="20" y="20" width="8" height="8" style="fill: #9abf88"></rect><rect x="20" y="36" width="8" height="8" style="fill: #9abf88"></rect></svg></div><div class="text-wrapper"><div role="meta" class="isso-comment-header"><span class="author">Tom Smeding</span><span class="spacer">•</span><a rel="nofollow" href="#isso-237" class="permalink"><time title="Fri Oct 30 2015 11:00:14 GMT+0100 (Central European Standard Time)" datetime="2015-09-05T10:00:14Z">vor 4 Jahren</time></a><span class="note"></span></div><div class="text"><p>Oh of course, silly me :P</p></div><div class="isso-comment-footer"><span class="votes">0</span><a rel="nofollow" href="#" class="upvote"><!-- Generator: IcoMoon.io --><svg width="16" height="16" viewBox="0 0 32 32" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" fill="gray">
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</a><a rel="nofollow" href="#" class="reply">Antworten</a></div><div class="isso-follow-up"></div></div></div><div id="isso-loader-232" class="isso-comment-loader"><a rel="nofollow" href="#" class="load_hidden">3 versteckt</a></div></div></div></div><div id="isso-238" class="isso-comment isso-no-votes"><div class="avatar"><svg version="1.1" viewBox="0 0 48 48" preserveAspectRatio="xMinYMin meet" shape-rendering="crispEdges" data-hash="0bc2df00636d"><rect x="0" y="0" width="56" height="56" style="fill: #f0f0f0"></rect><rect x="4" y="28" width="8" height="8" style="fill: #f19670"></rect><rect x="36" y="28" width="8" height="8" style="fill: #f19670"></rect><rect x="4" y="36" width="8" height="8" style="fill: #f19670"></rect><rect x="36" y="36" width="8" height="8" style="fill: #f19670"></rect><rect x="12" y="28" width="8" height="8" style="fill: #f19670"></rect><rect x="28" y="28" width="8" height="8" style="fill: #f19670"></rect><rect x="12" y="36" width="8" height="8" style="fill: #f19670"></rect><rect x="28" y="36" width="8" height="8" style="fill: #f19670"></rect><rect x="20" y="12" width="8" height="8" style="fill: #f19670"></rect><rect x="20" y="20" width="8" height="8" style="fill: #f19670"></rect><rect x="20" y="36" width="8" height="8" style="fill: #f19670"></rect></svg></div><div class="text-wrapper"><div role="meta" class="isso-comment-header"><span class="author">Tobias Schottdorf</span><span class="spacer">•</span><a rel="nofollow" href="#isso-238" class="permalink"><time title="Sun Nov 08 2015 16:53:32 GMT+0100 (Central European Standard Time)" datetime="2015-10-00T15:53:32Z">vor 4 Jahren</time></a><span class="note"></span></div><div class="text"><p>&gt; An entry in the P4, P3, P2, and P1 tables consists of the page aligned 52-bit physical address of the page/next page table and the following bits that can be OR-ed in:</p><p>I can't quite make sense of that - so the physical addresses which are available to virtual addressing are only 52bit (instead of all 64bit)? There appear to be 24 flags which can be or'ed in, but wouldn't that necessitate overwriting parts of the physical address (52bit + 22bit &gt; 64bit) of the page/page table?</p></div><div class="isso-comment-footer"><span class="votes">0</span><a rel="nofollow" href="#" class="upvote"><!-- Generator: IcoMoon.io --><svg width="16" height="16" viewBox="0 0 32 32" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" fill="gray">
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</a><a rel="nofollow" href="#" class="reply">Antworten</a></div><div class="isso-follow-up"><div id="isso-239" class="isso-comment isso-no-votes"><div class="avatar"><svg version="1.1" viewBox="0 0 48 48" preserveAspectRatio="xMinYMin meet" shape-rendering="crispEdges" data-hash="666df3217240"><rect x="0" y="0" width="56" height="56" style="fill: #f0f0f0"></rect><rect x="4" y="12" width="8" height="8" style="fill: #9abf88"></rect><rect x="36" y="12" width="8" height="8" style="fill: #9abf88"></rect><rect x="4" y="28" width="8" height="8" style="fill: #9abf88"></rect><rect x="36" y="28" width="8" height="8" style="fill: #9abf88"></rect><rect x="4" y="36" width="8" height="8" style="fill: #9abf88"></rect><rect x="36" y="36" width="8" height="8" style="fill: #9abf88"></rect><rect x="12" y="4" width="8" height="8" style="fill: #9abf88"></rect><rect x="28" y="4" width="8" height="8" style="fill: #9abf88"></rect><rect x="12" y="28" width="8" height="8" style="fill: #9abf88"></rect><rect x="28" y="28" width="8" height="8" style="fill: #9abf88"></rect><rect x="20" y="12" width="8" height="8" style="fill: #9abf88"></rect></svg></div><div class="text-wrapper"><div role="meta" class="isso-comment-header"><span class="author">Philipp Oppermann</span><span class="spacer">•</span><a rel="nofollow" href="#isso-239" class="permalink"><time title="Sun Nov 08 2015 19:20:42 GMT+0100 (Central European Standard Time)" datetime="2015-10-00T18:20:42Z">vor 4 Jahren</time></a><span class="note"></span></div><div class="text"><p>The key is that the physical addresses are page aligned. The last 12 bits are thus guaranteed to be 0 and can be used to store some flags. So there are 24 bits for the various flags and 52-12=40 bits for the aligned physical address. </p></div><div class="isso-comment-footer"><span class="votes">0</span><a rel="nofollow" href="#" class="upvote"><!-- Generator: IcoMoon.io --><svg width="16" height="16" viewBox="0 0 32 32" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" fill="gray">
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</a><a rel="nofollow" href="#" class="reply">Antworten</a></div><div class="isso-follow-up"></div></div></div><div id="isso-256" class="isso-comment isso-no-votes"><div class="avatar"><svg version="1.1" viewBox="0 0 48 48" preserveAspectRatio="xMinYMin meet" shape-rendering="crispEdges" data-hash="c08d83f42dfd"><rect x="0" y="0" width="56" height="56" style="fill: #f0f0f0"></rect><rect x="4" y="36" width="8" height="8" style="fill: #f19670"></rect><rect x="36" y="36" width="8" height="8" style="fill: #f19670"></rect><rect x="12" y="12" width="8" height="8" style="fill: #f19670"></rect><rect x="28" y="12" width="8" height="8" style="fill: #f19670"></rect><rect x="12" y="20" width="8" height="8" style="fill: #f19670"></rect><rect x="28" y="20" width="8" height="8" style="fill: #f19670"></rect><rect x="12" y="36" width="8" height="8" style="fill: #f19670"></rect><rect x="28" y="36" width="8" height="8" style="fill: #f19670"></rect><rect x="20" y="4" width="8" height="8" style="fill: #f19670"></rect><rect x="20" y="12" width="8" height="8" style="fill: #f19670"></rect><rect x="20" y="20" width="8" height="8" style="fill: #f19670"></rect><rect x="20" y="28" width="8" height="8" style="fill: #f19670"></rect><rect x="20" y="36" width="8" height="8" style="fill: #f19670"></rect></svg></div><div class="text-wrapper"><div role="meta" class="isso-comment-header"><span class="author">Nicholas Platt</span><span class="spacer">•</span><a rel="nofollow" href="#isso-256" class="permalink"><time title="Sun Mar 20 2016 19:55:05 GMT+0100 (Central European Standard Time)" datetime="2016-02-00T18:55:05Z">vor 3 Jahren</time></a><span class="note"></span></div><div class="text"><p>I'm confused about this as well. Why say "52-bit physical address" if the address is only 40 bits? Is it because the address is between sets of flags? Meaning, do the table entries really look like this?</p><p></p><pre>+-------+----------------------------------------+-------+<br>| flags | physical address (frame or next table) | flags |<br>+-------+----------------------------------------+-------+<br> 63      51                                       11     0</pre><p></p><p>Can you check my understanding:</p><p></p><pre>* Virtual addresses are effectively 48 bits:<br>    * Highest 16 bits are sign extension of 48th bit<br>    * Next 36 bits are used to navigate the paging tables<br>    * Lowest 12 bits are used as offset from physical address<br>      found in P1<br><br>* Physical addresses are effectively 40 bits and page aligned<br><br>* Paging table entries are 64 bits:<br>    * Highest 12 bits are flags<br>    * Next 40 bits are the physical address of a table or frame<br>    * Lowest 12 bits are flags<br></pre><p></p><p>Thus physical addresses identify the start of each aligned frame, and virtual addresses identify the location within the frame.</p></div><div class="isso-comment-footer"><span class="votes">0</span><a rel="nofollow" href="#" class="upvote"><!-- Generator: IcoMoon.io --><svg width="16" height="16" viewBox="0 0 32 32" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" fill="gray">
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</a><a rel="nofollow" href="#" class="reply">Antworten</a></div><div class="isso-follow-up"></div></div></div><div id="isso-258" class="isso-comment isso-no-votes"><div class="avatar"><svg version="1.1" viewBox="0 0 48 48" preserveAspectRatio="xMinYMin meet" shape-rendering="crispEdges" data-hash="666df3217240"><rect x="0" y="0" width="56" height="56" style="fill: #f0f0f0"></rect><rect x="4" y="12" width="8" height="8" style="fill: #9abf88"></rect><rect x="36" y="12" width="8" height="8" style="fill: #9abf88"></rect><rect x="4" y="28" width="8" height="8" style="fill: #9abf88"></rect><rect x="36" y="28" width="8" height="8" style="fill: #9abf88"></rect><rect x="4" y="36" width="8" height="8" style="fill: #9abf88"></rect><rect x="36" y="36" width="8" height="8" style="fill: #9abf88"></rect><rect x="12" y="4" width="8" height="8" style="fill: #9abf88"></rect><rect x="28" y="4" width="8" height="8" style="fill: #9abf88"></rect><rect x="12" y="28" width="8" height="8" style="fill: #9abf88"></rect><rect x="28" y="28" width="8" height="8" style="fill: #9abf88"></rect><rect x="20" y="12" width="8" height="8" style="fill: #9abf88"></rect></svg></div><div class="text-wrapper"><div role="meta" class="isso-comment-header"><span class="author">Philipp Oppermann</span><span class="spacer">•</span><a rel="nofollow" href="#isso-258" class="permalink"><time title="Sun Mar 20 2016 23:44:25 GMT+0100 (Central European Standard Time)" datetime="2016-02-00T22:44:25Z">vor 3 Jahren</time></a><span class="note"></span></div><div class="text"><p>The physical address is 52 bits. It is possible to address up to 2^52 bytes of memory with it. Operating systems without paging (e.g. MS-DOS) directly use the physical address to access memory. And so do we before we enable paging.</p><p>As soon as we enable paging, the CPU uses the memory management unit (MMU) to translate used addresses (“virtual addresses”) to the real memory addresses. These virtual addresses are effectively 48 bits on x86_64 and behave exactly as you stated.</p><p>So why are only 40 physical address bits stored in the page table? The reason is that the physical memory is split into page sized chunks, which are called frames. The first frame starts at physical address 0, the second frame at physical address 4096, and so on. Thus the physical address of a frame is always page aligned. There are still non-page-aligned physical addresses but they can't be the start of a frame.</p><p>So the lowest 12 bits of a valid physical frame address are always 0. We don't need to store anything if we know that it is always 0. Thus these bits can be used to store useful information instead (flags in our case).</p><p>I hope this helps in clearing up your confusion.</p></div><div class="isso-comment-footer"><span class="votes">0</span><a rel="nofollow" href="#" class="upvote"><!-- Generator: IcoMoon.io --><svg width="16" height="16" viewBox="0 0 32 32" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" fill="gray">
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</a><a rel="nofollow" href="#" class="reply">Antworten</a></div><div class="isso-follow-up"></div></div></div><div id="isso-259" class="isso-comment isso-no-votes"><div class="avatar"><svg version="1.1" viewBox="0 0 48 48" preserveAspectRatio="xMinYMin meet" shape-rendering="crispEdges" data-hash="c08d83f42dfd"><rect x="0" y="0" width="56" height="56" style="fill: #f0f0f0"></rect><rect x="4" y="36" width="8" height="8" style="fill: #f19670"></rect><rect x="36" y="36" width="8" height="8" style="fill: #f19670"></rect><rect x="12" y="12" width="8" height="8" style="fill: #f19670"></rect><rect x="28" y="12" width="8" height="8" style="fill: #f19670"></rect><rect x="12" y="20" width="8" height="8" style="fill: #f19670"></rect><rect x="28" y="20" width="8" height="8" style="fill: #f19670"></rect><rect x="12" y="36" width="8" height="8" style="fill: #f19670"></rect><rect x="28" y="36" width="8" height="8" style="fill: #f19670"></rect><rect x="20" y="4" width="8" height="8" style="fill: #f19670"></rect><rect x="20" y="12" width="8" height="8" style="fill: #f19670"></rect><rect x="20" y="20" width="8" height="8" style="fill: #f19670"></rect><rect x="20" y="28" width="8" height="8" style="fill: #f19670"></rect><rect x="20" y="36" width="8" height="8" style="fill: #f19670"></rect></svg></div><div class="text-wrapper"><div role="meta" class="isso-comment-header"><span class="author">Nicholas Platt</span><span class="spacer">•</span><a rel="nofollow" href="#isso-259" class="permalink"><time title="Mon Mar 21 2016 01:26:20 GMT+0100 (Central European Standard Time)" datetime="2016-02-01T00:26:20Z">vor 3 Jahren</time></a><span class="note"></span></div><div class="text"><p>Thanks, this has indeed become more clear as I've worked with it. I wrote (and just revised due to better understanding) <a rel="nofollow" href="https://github.com/caipre/mezzo/commit/d73dc2d3a84b68fd5c83c0c9959ffdf20a34ebde">a detailed comment</a> and that helped nail it down for me.</p><p>In case it's not clear to anyone else, the reason the lower bits are always 0 is because <code>4096 = 0x1000</code>.</p><p>Another question then: since we're aligning on 2mib pages here (<code>0x200000</code>), can we access the extra few bits (21 vs 12)?</p><p>I'll try this myself once I'm allocating pages.</p><p><strong>Edit:</strong><br>It seems like this idea works. I added the following lines after the paging table setup and didn't encounter any processor exceptions:</p><p></p><pre>; try writing within reserved address space,<br>; in a middle entry of P4<br>mov eax, (1 &lt;&lt; 31)<br>or [p4_table + (256*8)], eax</pre><p></p><p>I guess this works, just be sure you're acting on a 2mib page and not a 4kib page.</p><p></p></div><div class="isso-comment-footer"><span class="votes">0</span><a rel="nofollow" href="#" class="upvote"><!-- Generator: IcoMoon.io --><svg width="16" height="16" viewBox="0 0 32 32" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" fill="gray">
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</a><a rel="nofollow" href="#" class="reply">Antworten</a></div><div class="isso-follow-up"><div id="isso-243" class="isso-comment isso-no-votes"><div class="avatar"><svg version="1.1" viewBox="0 0 48 48" preserveAspectRatio="xMinYMin meet" shape-rendering="crispEdges" data-hash="666df3217240"><rect x="0" y="0" width="56" height="56" style="fill: #f0f0f0"></rect><rect x="4" y="12" width="8" height="8" style="fill: #9abf88"></rect><rect x="36" y="12" width="8" height="8" style="fill: #9abf88"></rect><rect x="4" y="28" width="8" height="8" style="fill: #9abf88"></rect><rect x="36" y="28" width="8" height="8" style="fill: #9abf88"></rect><rect x="4" y="36" width="8" height="8" style="fill: #9abf88"></rect><rect x="36" y="36" width="8" height="8" style="fill: #9abf88"></rect><rect x="12" y="4" width="8" height="8" style="fill: #9abf88"></rect><rect x="28" y="4" width="8" height="8" style="fill: #9abf88"></rect><rect x="12" y="28" width="8" height="8" style="fill: #9abf88"></rect><rect x="28" y="28" width="8" height="8" style="fill: #9abf88"></rect><rect x="20" y="12" width="8" height="8" style="fill: #9abf88"></rect></svg></div><div class="text-wrapper"><div role="meta" class="isso-comment-header"><span class="author">Philipp Oppermann</span><span class="spacer">•</span><a rel="nofollow" href="#isso-243" class="permalink"><time title="Sun Dec 27 2015 16:50:47 GMT+0100 (Central European Standard Time)" datetime="2015-11-00T15:50:47Z">vor 3 Jahren</time></a><span class="note"></span></div><div class="text"><p>Nice! You are porting it to C?</p></div><div class="isso-comment-footer"><span class="votes">0</span><a rel="nofollow" href="#" class="upvote"><!-- Generator: IcoMoon.io --><svg width="16" height="16" viewBox="0 0 32 32" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" fill="gray">
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</a><a rel="nofollow" href="#" class="reply">Antworten</a></div><div class="isso-follow-up"></div></div></div><div id="isso-248" class="isso-comment isso-no-votes"><div class="avatar"><svg version="1.1" viewBox="0 0 48 48" preserveAspectRatio="xMinYMin meet" shape-rendering="crispEdges" data-hash="823a84765cf4"><rect x="0" y="0" width="56" height="56" style="fill: #f0f0f0"></rect><rect x="4" y="4" width="8" height="8" style="fill: #be5168"></rect><rect x="36" y="4" width="8" height="8" style="fill: #be5168"></rect><rect x="4" y="28" width="8" height="8" style="fill: #be5168"></rect><rect x="36" y="28" width="8" height="8" style="fill: #be5168"></rect><rect x="12" y="4" width="8" height="8" style="fill: #be5168"></rect><rect x="28" y="4" width="8" height="8" style="fill: #be5168"></rect><rect x="12" y="12" width="8" height="8" style="fill: #be5168"></rect><rect x="28" y="12" width="8" height="8" style="fill: #be5168"></rect><rect x="12" y="20" width="8" height="8" style="fill: #be5168"></rect><rect x="28" y="20" width="8" height="8" style="fill: #be5168"></rect><rect x="20" y="4" width="8" height="8" style="fill: #be5168"></rect><rect x="20" y="12" width="8" height="8" style="fill: #be5168"></rect><rect x="20" y="20" width="8" height="8" style="fill: #be5168"></rect><rect x="20" y="28" width="8" height="8" style="fill: #be5168"></rect></svg></div><div class="text-wrapper"><div role="meta" class="isso-comment-header"><span class="author">anula</span><span class="spacer">•</span><a rel="nofollow" href="#isso-248" class="permalink"><time title="Thu Feb 18 2016 19:13:35 GMT+0100 (Central European Standard Time)" datetime="2016-01-04T18:13:35Z">vor 3 Jahren</time></a><span class="note"></span></div><div class="text"><p>Uh, that is an.. embarrassing error. I checked all registers twice (easy to mistake eax with ecx) but somehow never thought to check that... I guess that when you see top above bottom in code you unconsciously decide that it is ok.</p><p>About the note - it would probably make sense, maybe it will make someone to check their code twice, and surely will be a good reminder for people that have little experience with low level things like that.</p><p>Thanks very much for the help - I guess it would take me a lot of time later to debug it, when it would start to mysteriously fall after I add another function call in Rust.</p></div><div class="isso-comment-footer"><span class="votes">0</span><a rel="nofollow" href="#" class="upvote"><!-- Generator: IcoMoon.io --><svg width="16" height="16" viewBox="0 0 32 32" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" fill="gray">
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</a><a rel="nofollow" href="#" class="reply">Antworten</a></div><div class="isso-follow-up"></div></div></div><div id="isso-249" class="isso-comment isso-no-votes"><div class="avatar"><svg version="1.1" viewBox="0 0 48 48" preserveAspectRatio="xMinYMin meet" shape-rendering="crispEdges" data-hash="666df3217240"><rect x="0" y="0" width="56" height="56" style="fill: #f0f0f0"></rect><rect x="4" y="12" width="8" height="8" style="fill: #9abf88"></rect><rect x="36" y="12" width="8" height="8" style="fill: #9abf88"></rect><rect x="4" y="28" width="8" height="8" style="fill: #9abf88"></rect><rect x="36" y="28" width="8" height="8" style="fill: #9abf88"></rect><rect x="4" y="36" width="8" height="8" style="fill: #9abf88"></rect><rect x="36" y="36" width="8" height="8" style="fill: #9abf88"></rect><rect x="12" y="4" width="8" height="8" style="fill: #9abf88"></rect><rect x="28" y="4" width="8" height="8" style="fill: #9abf88"></rect><rect x="12" y="28" width="8" height="8" style="fill: #9abf88"></rect><rect x="28" y="28" width="8" height="8" style="fill: #9abf88"></rect><rect x="20" y="12" width="8" height="8" style="fill: #9abf88"></rect></svg></div><div class="text-wrapper"><div role="meta" class="isso-comment-header"><span class="author">Philipp Oppermann</span><span class="spacer">•</span><a rel="nofollow" href="#isso-249" class="permalink"><time title="Fri Feb 19 2016 10:20:18 GMT+0100 (Central European Standard Time)" datetime="2016-01-05T09:20:18Z">vor 3 Jahren</time></a><span class="note"></span></div><div class="text"><p>Not embarrassing at all, just hard to debug!</p><p>I created <a rel="nofollow" href="https://github.com/phil-opp/blog_os/issues/133">an issue</a> for the note, but it will take a while since I'm short on time right now. If you like, feel free to send a PR.</p></div><div class="isso-comment-footer"><span class="votes">0</span><a rel="nofollow" href="#" class="upvote"><!-- Generator: IcoMoon.io --><svg width="16" height="16" viewBox="0 0 32 32" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" fill="gray">
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</a><a rel="nofollow" href="#" class="reply">Antworten</a></div><div class="isso-follow-up"><div id="isso-251" class="isso-comment isso-no-votes"><div class="avatar"><svg version="1.1" viewBox="0 0 48 48" preserveAspectRatio="xMinYMin meet" shape-rendering="crispEdges" data-hash="666df3217240"><rect x="0" y="0" width="56" height="56" style="fill: #f0f0f0"></rect><rect x="4" y="12" width="8" height="8" style="fill: #9abf88"></rect><rect x="36" y="12" width="8" height="8" style="fill: #9abf88"></rect><rect x="4" y="28" width="8" height="8" style="fill: #9abf88"></rect><rect x="36" y="28" width="8" height="8" style="fill: #9abf88"></rect><rect x="4" y="36" width="8" height="8" style="fill: #9abf88"></rect><rect x="36" y="36" width="8" height="8" style="fill: #9abf88"></rect><rect x="12" y="4" width="8" height="8" style="fill: #9abf88"></rect><rect x="28" y="4" width="8" height="8" style="fill: #9abf88"></rect><rect x="12" y="28" width="8" height="8" style="fill: #9abf88"></rect><rect x="28" y="28" width="8" height="8" style="fill: #9abf88"></rect><rect x="20" y="12" width="8" height="8" style="fill: #9abf88"></rect></svg></div><div class="text-wrapper"><div role="meta" class="isso-comment-header"><span class="author">Philipp Oppermann</span><span class="spacer">•</span><a rel="nofollow" href="#isso-251" class="permalink"><time title="Tue Mar 01 2016 17:17:21 GMT+0100 (Central European Standard Time)" datetime="2016-02-02T16:17:21Z">vor 3 Jahren</time></a><span class="note"></span></div><div class="text"><p>A double fault occurs when you don't handle an exception/interrupt or your exception handler causes another exception. Do you enable interrupts (<code>sti</code>) or do you just catch cpu exceptions? Maybe you forgot to handle the interrupts from the hardware timer? But it's difficult to help without the actual code…</p></div><div class="isso-comment-footer"><span class="votes">0</span><a rel="nofollow" href="#" class="upvote"><!-- Generator: IcoMoon.io --><svg width="16" height="16" viewBox="0 0 32 32" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" fill="gray">
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</a><a rel="nofollow" href="#" class="reply">Antworten</a></div><div class="isso-follow-up"></div></div></div><div id="isso-252" class="isso-comment isso-no-votes"><div class="avatar"><svg version="1.1" viewBox="0 0 48 48" preserveAspectRatio="xMinYMin meet" shape-rendering="crispEdges" data-hash="3773460ec1e4"><rect x="0" y="0" width="56" height="56" style="fill: #f0f0f0"></rect><rect x="4" y="4" width="8" height="8" style="fill: #be5168"></rect><rect x="36" y="4" width="8" height="8" style="fill: #be5168"></rect><rect x="4" y="20" width="8" height="8" style="fill: #be5168"></rect><rect x="36" y="20" width="8" height="8" style="fill: #be5168"></rect><rect x="4" y="28" width="8" height="8" style="fill: #be5168"></rect><rect x="36" y="28" width="8" height="8" style="fill: #be5168"></rect><rect x="12" y="36" width="8" height="8" style="fill: #be5168"></rect><rect x="28" y="36" width="8" height="8" style="fill: #be5168"></rect><rect x="20" y="4" width="8" height="8" style="fill: #be5168"></rect><rect x="20" y="12" width="8" height="8" style="fill: #be5168"></rect><rect x="20" y="20" width="8" height="8" style="fill: #be5168"></rect></svg></div><div class="text-wrapper"><div role="meta" class="isso-comment-header"><span class="author">Wink Saville</span><span class="spacer">•</span><a rel="nofollow" href="#isso-252" class="permalink"><time title="Tue Mar 01 2016 21:32:36 GMT+0100 (Central European Standard Time)" datetime="2016-02-02T20:32:36Z">vor 3 Jahren</time></a><span class="note"></span></div><div class="text"><p>Agreed, and I see that in my more sophisticated program, the question is what is it that I'm doing wrong. I believe I've setup the Interrupt Descriptor Table to handle all interrupts, i.e. I have an array of 256 interrupt gates. That program is here (https://github.com/winksaville/sadie but its too complicated to debug and I haven't yet checked in my non-working APIC timer code. But with that code I'm able to do software interrupts and also when my APIC timer code fires an interrupt fast enough it does work. So it would seem I've done most of the initialization "properly". Note, I'm also compiling my code with -mno-red-zone so that shouldn't be the problem.</p><p>So my debug strategy in situations such as this is to simplify. So the first thing was to just enable interrupts and doing nothing that should cause an interrupt to occur and then delay awhile in the code and see what happens. But, sure enough I'm still getting a double fault. Of course according to the documentation in the Intel SDM Volume 3 section 6.15 "Interrupt 8--Double Fault Exception (#DF)" the error code is 0 and CS EIP registers are undefined :(</p><p>Anyway, I then simplified to as simple as I can get. I modified your boot.asm program adding the code below the esp initialization that output's character to the VGA display.</p><p></p><pre><code><br>start:<br>  mov esp, stack_top<br><br>  ; Save registers<br>  push edx<br>  push ecx<br>  push ebx<br>  push eax<br><br>  ; Enable interrupts<br>  ;sti<br><br>  ; Initialize edx to vga buffer ah attribute, al ch<br>  mov edx, 0xb8000<br>  mov ax, 0x0f60<br><br>  ; ebx number of loops<br>  mov ebx,10000<br><br>.loop:<br><br>  ; Output next character and attribute<br>  mov word [edx], ax<br><br>  ; Increment to next character with wrap<br>  inc al<br>  cmp al, 0x7f<br>  jne .nextloc<br>  mov al,60<br><br>  ; Next location with wrap<br>.nextloc:<br>  add edx, 2<br>  and edx,0x7ff<br>  or  edx,0xb8000<br><br>  ; Delay<br>  mov ecx,0x2000<br>.delay:<br>  loop .delay<br><br>  ; Continue looping until ebx is 0<br>  dec ebx<br>  jnz .loop<br><br>  ; Disable interrupts<br>  cli<br><br>  ; Restore registers<br>  pop  eax<br>  pop  ebx<br>  pop  ecx<br>  pop  edx<br></code></pre><p></p><p>Here is a github repo: (https://github.com/winksaville/baremetal-po-x86_64/tree/test_enable_interrupts). If you add the above code to your boot.asm it will print 10,000 characters to the VGA display and then continue with the normal code paths. If the "sti" instruction is commented out, as it is above, then all is well. But if I uncomment the "sti" thus enabling interrupts then it fails.</p><p>I anticipated that enabling interrupts would succeed as I wouldn't expect any interrupts because the hardware is in a state where no interrupts should be generated. Or if grub or the BIOS is using interrupts then I'd expect things to also be OK.</p><p>Obviously I'm wrong and I'd hope you'd be able to suggest where my flaw is.</p></div><div class="isso-comment-footer"><span class="votes">0</span><a rel="nofollow" href="#" class="upvote"><!-- Generator: IcoMoon.io --><svg width="16" height="16" viewBox="0 0 32 32" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" fill="gray">
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</a><a rel="nofollow" href="#" class="reply">Antworten</a></div><div class="isso-follow-up"></div></div></div><div id="isso-253" class="isso-comment isso-no-votes"><div class="avatar"><svg version="1.1" viewBox="0 0 48 48" preserveAspectRatio="xMinYMin meet" shape-rendering="crispEdges" data-hash="666df3217240"><rect x="0" y="0" width="56" height="56" style="fill: #f0f0f0"></rect><rect x="4" y="12" width="8" height="8" style="fill: #9abf88"></rect><rect x="36" y="12" width="8" height="8" style="fill: #9abf88"></rect><rect x="4" y="28" width="8" height="8" style="fill: #9abf88"></rect><rect x="36" y="28" width="8" height="8" style="fill: #9abf88"></rect><rect x="4" y="36" width="8" height="8" style="fill: #9abf88"></rect><rect x="36" y="36" width="8" height="8" style="fill: #9abf88"></rect><rect x="12" y="4" width="8" height="8" style="fill: #9abf88"></rect><rect x="28" y="4" width="8" height="8" style="fill: #9abf88"></rect><rect x="12" y="28" width="8" height="8" style="fill: #9abf88"></rect><rect x="28" y="28" width="8" height="8" style="fill: #9abf88"></rect><rect x="20" y="12" width="8" height="8" style="fill: #9abf88"></rect></svg></div><div class="text-wrapper"><div role="meta" class="isso-comment-header"><span class="author">Philipp Oppermann</span><span class="spacer">•</span><a rel="nofollow" href="#isso-253" class="permalink"><time title="Wed Mar 02 2016 16:30:12 GMT+0100 (Central European Standard Time)" datetime="2016-02-03T15:30:12Z">vor 3 Jahren</time></a><span class="note"></span></div><div class="text"><p>Thanks for the overview and the simplified example! I haven't had the time to look at it in detail, but the problem in your simplified example could be the <a rel="nofollow" href="https://wiki.osdev.org/Programmable_Interval_Timer">Programmable Interval timer</a>. From the “Outputs” section:</p><p></p><blockquote>The output from PIT channel 0 is connected to the PIC chip, so that it generates an "IRQ 0". Typically during boot the BIOS sets channel 0 with a count of 65535 or 0 (which translates to 65536), which gives an output frequency of 18.2065 Hz (or an IRQ every 54.9254 ms).</blockquote><p></p><p>So it seems like the BIOS turns it on by default so that it causes an interrupts every ~55ms. This causes a double fault, since there is no interrupt handler for IRQ 0.</p></div><div class="isso-comment-footer"><span class="votes">0</span><a rel="nofollow" href="#" class="upvote"><!-- Generator: IcoMoon.io --><svg width="16" height="16" viewBox="0 0 32 32" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" fill="gray">
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</a><a rel="nofollow" href="#" class="reply">Antworten</a></div><div class="isso-follow-up"></div></div></div><div id="isso-254" class="isso-comment isso-no-votes"><div class="avatar"><svg version="1.1" viewBox="0 0 48 48" preserveAspectRatio="xMinYMin meet" shape-rendering="crispEdges" data-hash="3773460ec1e4"><rect x="0" y="0" width="56" height="56" style="fill: #f0f0f0"></rect><rect x="4" y="4" width="8" height="8" style="fill: #be5168"></rect><rect x="36" y="4" width="8" height="8" style="fill: #be5168"></rect><rect x="4" y="20" width="8" height="8" style="fill: #be5168"></rect><rect x="36" y="20" width="8" height="8" style="fill: #be5168"></rect><rect x="4" y="28" width="8" height="8" style="fill: #be5168"></rect><rect x="36" y="28" width="8" height="8" style="fill: #be5168"></rect><rect x="12" y="36" width="8" height="8" style="fill: #be5168"></rect><rect x="28" y="36" width="8" height="8" style="fill: #be5168"></rect><rect x="20" y="4" width="8" height="8" style="fill: #be5168"></rect><rect x="20" y="12" width="8" height="8" style="fill: #be5168"></rect><rect x="20" y="20" width="8" height="8" style="fill: #be5168"></rect></svg></div><div class="text-wrapper"><div role="meta" class="isso-comment-header"><span class="author">Wink Saville</span><span class="spacer">•</span><a rel="nofollow" href="#isso-254" class="permalink"><time title="Thu Mar 03 2016 04:46:05 GMT+0100 (Central European Standard Time)" datetime="2016-02-04T03:46:05Z">vor 3 Jahren</time></a><span class="note"></span></div><div class="text"><p>Philipp, you were correct, the PIT was the culprit causing the "Double Fault". Although it turns out the PIT is actually generating an Interrupt 8 so its not really a Double Fault it just a PIT interrupt.</p><p>My short term solution is to add a pit_isr as interrupt 8 handler and at the end of pit_isr send an EOI to the PIT using outb(0x20, 0x20). I also needed to issue a APIC EOI for my apic_timer_isr and I cleaned up the initialization. So now my system is cleanly handling these interrupts at least.</p><p>For the PIT I really want to disable it and I'd like to suggest disabling the PIT be part of boot.asm so that my simple sti, delay, cli test works. If/when I figure that out I'll let you know. Oh, and if know how to disalbe the PIT please let me know.</p><p>Thanks again for your help!</p></div><div class="isso-comment-footer"><span class="votes">0</span><a rel="nofollow" href="#" class="upvote"><!-- Generator: IcoMoon.io --><svg width="16" height="16" viewBox="0 0 32 32" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" fill="gray">
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</a><a rel="nofollow" href="#" class="reply">Antworten</a></div><div class="isso-follow-up"></div></div></div><div id="isso-255" class="isso-comment isso-no-votes"><div class="avatar"><svg version="1.1" viewBox="0 0 48 48" preserveAspectRatio="xMinYMin meet" shape-rendering="crispEdges" data-hash="3773460ec1e4"><rect x="0" y="0" width="56" height="56" style="fill: #f0f0f0"></rect><rect x="4" y="4" width="8" height="8" style="fill: #be5168"></rect><rect x="36" y="4" width="8" height="8" style="fill: #be5168"></rect><rect x="4" y="20" width="8" height="8" style="fill: #be5168"></rect><rect x="36" y="20" width="8" height="8" style="fill: #be5168"></rect><rect x="4" y="28" width="8" height="8" style="fill: #be5168"></rect><rect x="36" y="28" width="8" height="8" style="fill: #be5168"></rect><rect x="12" y="36" width="8" height="8" style="fill: #be5168"></rect><rect x="28" y="36" width="8" height="8" style="fill: #be5168"></rect><rect x="20" y="4" width="8" height="8" style="fill: #be5168"></rect><rect x="20" y="12" width="8" height="8" style="fill: #be5168"></rect><rect x="20" y="20" width="8" height="8" style="fill: #be5168"></rect></svg></div><div class="text-wrapper"><div role="meta" class="isso-comment-header"><span class="author">Wink Saville</span><span class="spacer">•</span><a rel="nofollow" href="#isso-255" class="permalink"><time title="Fri Mar 04 2016 01:53:38 GMT+0100 (Central European Standard Time)" datetime="2016-02-05T00:53:38Z">vor 3 Jahren</time></a><span class="note"></span></div><div class="text"><p>Here is a solution. There doesn't seem to be a way to disable the PIT, but you can disable all IRQ's from the PIC, adding the following code to my test_enable_interrupts branch allows the code to work even with the enabling interrupts:</p><p>```<br>    ; Disable PIC interrupts so we don't get interrupts if the PIC<br>    ; was being used by grub or BIOS. See Disabling section of<br>    ; <a rel="nofollow" href="https://wiki.osdev.org/PIC">https://wiki.osdev.org/PIC</a>. If the application wants to use devices<br>; connected to the PIC, such at the PIT, it will probably want<br>    ; to remap the PIC interrupts to be above 0 .. 31 which are<br>    ; used or reserved by Intel. See the Initialisation section of<br>    ; the same page for the PIC_remap subroutine.</p><p>    mov al,0xff<br>    out 0xa1, al<br>    out 0x21, al<br>```</p><p>Thanks again for your help.</p></div><div class="isso-comment-footer"><span class="votes">0</span><a rel="nofollow" href="#" class="upvote"><!-- Generator: IcoMoon.io --><svg width="16" height="16" viewBox="0 0 32 32" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" fill="gray">
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</a><a rel="nofollow" href="#" class="reply">Antworten</a></div><div class="isso-follow-up"></div></div></div><div id="isso-264" class="isso-comment isso-no-votes"><div class="avatar"><svg version="1.1" viewBox="0 0 48 48" preserveAspectRatio="xMinYMin meet" shape-rendering="crispEdges" data-hash="4063fb57aa16"><rect x="0" y="0" width="56" height="56" style="fill: #f0f0f0"></rect><rect x="4" y="4" width="8" height="8" style="fill: #e4bf80"></rect><rect x="36" y="4" width="8" height="8" style="fill: #e4bf80"></rect><rect x="4" y="12" width="8" height="8" style="fill: #e4bf80"></rect><rect x="36" y="12" width="8" height="8" style="fill: #e4bf80"></rect><rect x="4" y="20" width="8" height="8" style="fill: #e4bf80"></rect><rect x="36" y="20" width="8" height="8" style="fill: #e4bf80"></rect><rect x="4" y="36" width="8" height="8" style="fill: #e4bf80"></rect><rect x="36" y="36" width="8" height="8" style="fill: #e4bf80"></rect><rect x="12" y="12" width="8" height="8" style="fill: #e4bf80"></rect><rect x="28" y="12" width="8" height="8" style="fill: #e4bf80"></rect><rect x="12" y="28" width="8" height="8" style="fill: #e4bf80"></rect><rect x="28" y="28" width="8" height="8" style="fill: #e4bf80"></rect><rect x="20" y="28" width="8" height="8" style="fill: #e4bf80"></rect></svg></div><div class="text-wrapper"><div role="meta" class="isso-comment-header"><span class="author">Don Rowe</span><span class="spacer">•</span><a rel="nofollow" href="#isso-264" class="permalink"><time title="Thu Jul 28 2016 08:09:33 GMT+0200 (Central European Summer Time)" datetime="2016-06-04T06:09:33Z">vor 3 Jahren</time></a><span class="note"></span></div><div class="text"><p>Hi, Philipp! Thanks so much for creating this for us--it's been very fun to go from 0-OKAY with the ASM here, and I can't wait to get to the Rust portion (which is what drew me to this project in the first place. I'm a little confused, though, about the 4-level paging structure. Is there exactly one each of P2, P3, and P4, and then 512 different P1's that each point to various 4K physical pages?</p></div><div class="isso-comment-footer"><span class="votes">0</span><a rel="nofollow" href="#" class="upvote"><!-- Generator: IcoMoon.io --><svg width="16" height="16" viewBox="0 0 32 32" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" fill="gray">
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</a><a rel="nofollow" href="#" class="reply">Antworten</a></div><div class="isso-follow-up"><div id="isso-286" class="isso-comment isso-no-votes"><div class="avatar"><svg version="1.1" viewBox="0 0 48 48" preserveAspectRatio="xMinYMin meet" shape-rendering="crispEdges" data-hash="666df3217240"><rect x="0" y="0" width="56" height="56" style="fill: #f0f0f0"></rect><rect x="4" y="12" width="8" height="8" style="fill: #9abf88"></rect><rect x="36" y="12" width="8" height="8" style="fill: #9abf88"></rect><rect x="4" y="28" width="8" height="8" style="fill: #9abf88"></rect><rect x="36" y="28" width="8" height="8" style="fill: #9abf88"></rect><rect x="4" y="36" width="8" height="8" style="fill: #9abf88"></rect><rect x="36" y="36" width="8" height="8" style="fill: #9abf88"></rect><rect x="12" y="4" width="8" height="8" style="fill: #9abf88"></rect><rect x="28" y="4" width="8" height="8" style="fill: #9abf88"></rect><rect x="12" y="28" width="8" height="8" style="fill: #9abf88"></rect><rect x="28" y="28" width="8" height="8" style="fill: #9abf88"></rect><rect x="20" y="12" width="8" height="8" style="fill: #9abf88"></rect></svg></div><div class="text-wrapper"><div role="meta" class="isso-comment-header"><span class="author">Philipp Oppermann</span><span class="spacer">•</span><a rel="nofollow" href="#isso-286" class="permalink"><time title="Mon Apr 17 2017 12:52:41 GMT+0200 (Central European Summer Time)" datetime="2017-03-01T10:52:41Z">vor 2 Jahren</time></a><span class="note"></span></div><div class="text"><p>Thanks!</p><p>We don't use a P1 because it would be cumbersome to set up 512 P1 tables in assembly. Instead, we set the huge bit in the P2 entries, which signals to the CPU that the entry directly points to the physical start address of a 2MiB page frame. This address has to be 2MiB aligned, so bits 0-23 have to be zero. When translating an address, these bits specify the offset in the 2MiB page.</p><p></p><blockquote>Just a remark, would be clearer to add in the Paging section the meaning of bits 12-31 containing the physical address of the next P or the physical address.</blockquote><p></p><p>Thanks for the suggestion! I opened <a rel="nofollow" href="https://github.com/phil-opp/blog_os/issues/314">#314</a> to track it.</p></div><div class="isso-comment-footer"><span class="votes">0</span><a rel="nofollow" href="#" class="upvote"><!-- Generator: IcoMoon.io --><svg width="16" height="16" viewBox="0 0 32 32" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" fill="gray">
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</a><a rel="nofollow" href="#" class="reply">Antworten</a></div><div class="isso-follow-up"></div></div></div><div id="isso-291" class="isso-comment isso-no-votes"><div class="avatar"><svg version="1.1" viewBox="0 0 48 48" preserveAspectRatio="xMinYMin meet" shape-rendering="crispEdges" data-hash="666df3217240"><rect x="0" y="0" width="56" height="56" style="fill: #f0f0f0"></rect><rect x="4" y="12" width="8" height="8" style="fill: #9abf88"></rect><rect x="36" y="12" width="8" height="8" style="fill: #9abf88"></rect><rect x="4" y="28" width="8" height="8" style="fill: #9abf88"></rect><rect x="36" y="28" width="8" height="8" style="fill: #9abf88"></rect><rect x="4" y="36" width="8" height="8" style="fill: #9abf88"></rect><rect x="36" y="36" width="8" height="8" style="fill: #9abf88"></rect><rect x="12" y="4" width="8" height="8" style="fill: #9abf88"></rect><rect x="28" y="4" width="8" height="8" style="fill: #9abf88"></rect><rect x="12" y="28" width="8" height="8" style="fill: #9abf88"></rect><rect x="28" y="28" width="8" height="8" style="fill: #9abf88"></rect><rect x="20" y="12" width="8" height="8" style="fill: #9abf88"></rect></svg></div><div class="text-wrapper"><div role="meta" class="isso-comment-header"><span class="author">Philipp Oppermann</span><span class="spacer">•</span><a rel="nofollow" href="#isso-291" class="permalink"><time title="Thu Jun 08 2017 11:44:20 GMT+0200 (Central European Summer Time)" datetime="2017-05-04T09:44:20Z">vor 2 Jahren</time></a><span class="note"></span></div><div class="text"><p>Hmm, do you have a link to the documentation? I can't find anything relevant on page 4-37 in this document: https://www.intel.com/Assets/en_US/PDF/manual/253667.pdf</p><p>The AMD64 manual states on page 253:</p><p></p><blockquote>Normally, an IRET that pops a null selector into the SS register causes a general-protection exception (#GP) to occur. However, in long mode, the null selector indicates the existence of nested interrupt handlers and/or privileged software in 64-bit mode. Long mode allows an IRET to pop a null selector into SS from the stack under the following conditions:<br>• The target mode is 64-bit mode.<br>• The target CPL&lt;3.<br>In this case, the processor does not load an SS descriptor, and the null selector is loaded into SS without causing a #GP exception<br></blockquote><p></p><p>Maybe I interpreted that wrong, though…</p></div><div class="isso-comment-footer"><span class="votes">0</span><a rel="nofollow" href="#" class="upvote"><!-- Generator: IcoMoon.io --><svg width="16" height="16" viewBox="0 0 32 32" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" fill="gray">
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</a><a rel="nofollow" href="#" class="reply">Antworten</a></div><div class="isso-follow-up"></div></div></div><div id="isso-292" class="isso-comment isso-no-votes"><div class="avatar"><svg version="1.1" viewBox="0 0 48 48" preserveAspectRatio="xMinYMin meet" shape-rendering="crispEdges" data-hash="f6ffed79ea8d"><rect x="0" y="0" width="56" height="56" style="fill: #f0f0f0"></rect><rect x="4" y="12" width="8" height="8" style="fill: #f19670"></rect><rect x="36" y="12" width="8" height="8" style="fill: #f19670"></rect><rect x="4" y="20" width="8" height="8" style="fill: #f19670"></rect><rect x="36" y="20" width="8" height="8" style="fill: #f19670"></rect><rect x="4" y="28" width="8" height="8" style="fill: #f19670"></rect><rect x="36" y="28" width="8" height="8" style="fill: #f19670"></rect><rect x="4" y="36" width="8" height="8" style="fill: #f19670"></rect><rect x="36" y="36" width="8" height="8" style="fill: #f19670"></rect><rect x="12" y="12" width="8" height="8" style="fill: #f19670"></rect><rect x="28" y="12" width="8" height="8" style="fill: #f19670"></rect><rect x="12" y="28" width="8" height="8" style="fill: #f19670"></rect><rect x="28" y="28" width="8" height="8" style="fill: #f19670"></rect><rect x="20" y="4" width="8" height="8" style="fill: #f19670"></rect><rect x="20" y="36" width="8" height="8" style="fill: #f19670"></rect></svg></div><div class="text-wrapper"><div role="meta" class="isso-comment-header"><span class="author">Anatol Pomozov</span><span class="spacer">•</span><a rel="nofollow" href="#isso-292" class="permalink"><time title="Thu Jun 08 2017 13:41:12 GMT+0200 (Central European Summer Time)" datetime="2017-05-04T11:41:12Z">vor 2 Jahren</time></a><span class="note"></span></div><div class="text"><p>Hi Philipp, your link points to 6 years old Intel doc, here is the same but much more recent <a rel="nofollow" href="https://software.intel.com/sites/default/files/managed/7c/f1/253667-sdm-vol-2b.pdf">https://software.intel.com/...</a></p><p>Scroll to 'MOV' instruction, page 4-37. There is a block algorithm for MOV that says</p><p>IF segment selector is NULL<br>THEN #GP(0); FI;</p><p>I believe I hit this issue.</p></div><div class="isso-comment-footer"><span class="votes">0</span><a rel="nofollow" href="#" class="upvote"><!-- Generator: IcoMoon.io --><svg width="16" height="16" viewBox="0 0 32 32" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" fill="gray">
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</a><a rel="nofollow" href="#" class="reply">Antworten</a></div><div class="isso-follow-up"></div></div></div><div id="isso-loader-288" class="isso-comment-loader"><a rel="nofollow" href="#" class="load_hidden">1 versteckt</a></div></div></div></div><div id="isso-300" class="isso-comment isso-no-votes"><div class="avatar"><svg version="1.1" viewBox="0 0 48 48" preserveAspectRatio="xMinYMin meet" shape-rendering="crispEdges" data-hash="f6ffed79ea8d"><rect x="0" y="0" width="56" height="56" style="fill: #f0f0f0"></rect><rect x="4" y="12" width="8" height="8" style="fill: #f19670"></rect><rect x="36" y="12" width="8" height="8" style="fill: #f19670"></rect><rect x="4" y="20" width="8" height="8" style="fill: #f19670"></rect><rect x="36" y="20" width="8" height="8" style="fill: #f19670"></rect><rect x="4" y="28" width="8" height="8" style="fill: #f19670"></rect><rect x="36" y="28" width="8" height="8" style="fill: #f19670"></rect><rect x="4" y="36" width="8" height="8" style="fill: #f19670"></rect><rect x="36" y="36" width="8" height="8" style="fill: #f19670"></rect><rect x="12" y="12" width="8" height="8" style="fill: #f19670"></rect><rect x="28" y="12" width="8" height="8" style="fill: #f19670"></rect><rect x="12" y="28" width="8" height="8" style="fill: #f19670"></rect><rect x="28" y="28" width="8" height="8" style="fill: #f19670"></rect><rect x="20" y="4" width="8" height="8" style="fill: #f19670"></rect><rect x="20" y="36" width="8" height="8" style="fill: #f19670"></rect></svg></div><div class="text-wrapper"><div role="meta" class="isso-comment-header"><span class="author">Anatol Pomozov</span><span class="spacer">•</span><a rel="nofollow" href="#isso-300" class="permalink"><time title="Thu Jun 22 2017 20:21:41 GMT+0200 (Central European Summer Time)" datetime="2017-05-04T18:21:41Z">letztes Jahr</time></a><span class="note"></span></div><div class="text"><p>I have one more question. In your example you do a jump to long mode. As far as I know long 'call' can be used here as well. In fact call works in KVM and vmware but for some reason the operation crashes with #GP error. Do you know why it can be?</p></div><div class="isso-comment-footer"><span class="votes">0</span><a rel="nofollow" href="#" class="upvote"><!-- Generator: IcoMoon.io --><svg width="16" height="16" viewBox="0 0 32 32" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" fill="gray">
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</a><a rel="nofollow" href="#" class="reply">Antworten</a></div><div class="isso-follow-up"></div></div></div></div></div></div><div id="isso-307" class="isso-comment isso-no-votes"><div class="avatar"><svg version="1.1" viewBox="0 0 48 48" preserveAspectRatio="xMinYMin meet" shape-rendering="crispEdges" data-hash="49569f04b2b6"><rect x="0" y="0" width="56" height="56" style="fill: #f0f0f0"></rect><rect x="4" y="20" width="8" height="8" style="fill: #e4bf80"></rect><rect x="36" y="20" width="8" height="8" style="fill: #e4bf80"></rect><rect x="4" y="36" width="8" height="8" style="fill: #e4bf80"></rect><rect x="36" y="36" width="8" height="8" style="fill: #e4bf80"></rect><rect x="12" y="4" width="8" height="8" style="fill: #e4bf80"></rect><rect x="28" y="4" width="8" height="8" style="fill: #e4bf80"></rect><rect x="12" y="28" width="8" height="8" style="fill: #e4bf80"></rect><rect x="28" y="28" width="8" height="8" style="fill: #e4bf80"></rect><rect x="20" y="4" width="8" height="8" style="fill: #e4bf80"></rect><rect x="20" y="20" width="8" height="8" style="fill: #e4bf80"></rect><rect x="20" y="28" width="8" height="8" style="fill: #e4bf80"></rect></svg></div><div class="text-wrapper"><div role="meta" class="isso-comment-header"><span class="author">Tomáš Král</span><span class="spacer">•</span><a rel="nofollow" href="#isso-307" class="permalink"><time title="Wed Jul 12 2017 12:08:32 GMT+0200 (Central European Summer Time)" datetime="2017-06-03T10:08:32Z">letztes Jahr</time></a><span class="note"></span></div><div class="text"><p>Hi, I can't get the boot.asm file to assemble because it gives me this error: src/arch/x86_64/boot.asm:(.text+0x4a): undefined reference to `long_mode_start'</p></div><div class="isso-comment-footer"><span class="votes">0</span><a rel="nofollow" href="#" class="upvote"><!-- Generator: IcoMoon.io --><svg width="16" height="16" viewBox="0 0 32 32" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" fill="gray">
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<p>out of curiosity: Does it make sense to keep the 32bit print instructions as "dead code" in the program? It can never be reached, right?</p>

<pre><code>; print `OK` to screen
mov dword [0xb8000], 0x2f4b2f4f
hlt
</code></pre></div><div class="isso-comment-footer"><span class="votes">0</span><a rel="nofollow" href="#" class="upvote"><!-- Generator: IcoMoon.io --><svg width="16" height="16" viewBox="0 0 32 32" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" fill="gray">
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contains the 52-bit physical address of the next frame/entry but in the
table it looks like only bits 12-51 (40 bits) are used for that.</p></div><div class="isso-comment-footer"><span class="votes">1</span><a rel="nofollow" href="#" class="upvote"><!-- Generator: IcoMoon.io --><svg width="16" height="16" viewBox="0 0 32 32" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" fill="gray">
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<p>I'm trying to follow your steps while I'm trying to build a kernel in Rust. I have some questions at this point:</p>

<ol>
<li><p>you skipped the A20 gate checking altogether. Is that an error or you consider it so arcane that is just not needed? On my emulators I'm trying to activate it and my machine just goes haywire.</p></li>
<li><p>why do you map 1 GB for your kernel here? A smaller amount would surely be as suitable as 1 GB</p></li>
<li><p>some other sites/blogs/resources I read on the internet warn us to map the kernel to a higher area due to linker issues</p></li>
<li><p>I haven't read in detail the next posts, but I've seen you remap the kernel somewhere in the future. Is that because what you are doing here is just a quick way to go to long mode, and you actually do it as needed in Rust?</p></li>
<li><p>On OSDev they also mention something about a P5 coming in the future.</p></li>
</ol>

<p>Thanks, very informative reading!</p></div><div class="isso-comment-footer"><span class="votes">0</span><a rel="nofollow" href="#" class="upvote"><!-- Generator: IcoMoon.io --><svg width="16" height="16" viewBox="0 0 32 32" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" fill="gray">
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{% endraw %}
