https://monjiapawne.github.io/blog/docs/x86-64/Recent content in x86-64 AT&T on monjiapawneHugoen-usWed, 22 Apr 2026 21:19:13 -0400https://monjiapawne.github.io/blog/docs/x86-64/cheatsheet/Wed, 22 Apr 2026 21:19:13 -0400https://monjiapawne.github.io/blog/docs/x86-64/cheatsheet/<h1 id="x86-64-att-syntax">x86-64 (AT&amp;T Syntax)<a class="anchor" href="#x86-64-att-syntax">#</a></h1> <hr> <h2 id="registers">Registers<a class="anchor" href="#registers">#</a></h2> <h3 id="general-purpose">General Purpose<a class="anchor" href="#general-purpose">#</a></h3> <table> <thead> <tr> <th>Register</th> <th>64</th> <th>32</th> <th>16</th> <th>8</th> </tr> </thead> <tbody> <tr> <td>accumulator</td> <td><code>%rax</code></td> <td><code>%eax</code></td> <td><code>%ax</code></td> <td><code>%al</code></td> </tr> <tr> <td>base</td> <td><code>%rbx</code></td> <td><code>%ebx</code></td> <td><code>%bx</code></td> <td><code>%bl</code></td> </tr> <tr> <td>counter</td> <td><code>%rcx</code></td> <td><code>%ecx</code></td> <td><code>%cx</code></td> <td><code>%cl</code></td> </tr> <tr> <td>data</td> <td><code>%rdx</code></td> <td><code>%edx</code></td> <td><code>%dx</code></td> <td><code>%dl</code></td> </tr> <tr> <td>source index</td> <td><code>%rsi</code></td> <td><code>%esi</code></td> <td><code>%si</code></td> <td><code>%sil</code></td> </tr> <tr> <td>dest index</td> <td><code>%rdi</code></td> <td><code>%edi</code></td> <td><code>%di</code></td> <td><code>%dil</code></td> </tr> <tr> <td>stack pointer</td> <td><code>%rsp</code></td> <td>—</td> <td>—</td> <td>—</td> </tr> <tr> <td>base pointer</td> <td><code>%rbp</code></td> <td>—</td> <td>—</td> <td>—</td> </tr> <tr> <td>extended</td> <td><code>%r8</code>–<code>%r15</code></td> <td><code>%r8d</code></td> <td><code>%r8w</code></td> <td><code>%r8b</code></td> </tr> </tbody> </table> <h3 id="size-suffixes-gnu">Size Suffixes (GNU)<a class="anchor" href="#size-suffixes-gnu">#</a></h3> <ul> <li><code>q</code> — 8 bytes</li> <li><code>l</code> — 4 bytes</li> <li><code>w</code> — 2 bytes</li> <li><code>b</code> — 1 byte</li> </ul> <hr> <h3 id="caller-saved">Caller-Saved<a class="anchor" href="#caller-saved">#</a></h3> <p>registers the caller must save if needed after a call</p>https://monjiapawne.github.io/blog/docs/x86-64/resources/Wed, 22 Apr 2026 21:19:13 -0400https://monjiapawne.github.io/blog/docs/x86-64/resources/<h1 id="resources">resources<a class="anchor" href="#resources">#</a></h1> <h2 id="syscalls">Syscalls<a class="anchor" href="#syscalls">#</a></h2> <ul> <li><a href="https://www.chromium.org/chromium-os/developer-library/reference/linux-constants/syscalls/">chromium docs</a></li> </ul> <h2 id="registers">Registers<a class="anchor" href="#registers">#</a></h2> <ul> <li><a href="https://go.dev/src/cmd/compile/abi-internal#amd64-architecture">https://go.dev/src/cmd/compile/abi-internal#amd64-architecture</a></li> <li><a href="https://wiki.osdev.org/CPU_Registers_x86-64">https://wiki.osdev.org/CPU_Registers_x86-64</a></li> </ul> <h2 id="instructions">Instructions<a class="anchor" href="#instructions">#</a></h2> <ul> <li><a href="http://ref.x86asm.net/coder64-abc.html">http://ref.x86asm.net/coder64-abc.html</a></li> <li><a href="https://learning.oreilly.com/library/view/learn-to-program/9781484274378/html/514232_1_En_24_Chapter.xhtml">https://learning.oreilly.com/library/view/learn-to-program/9781484274378/html/514232_1_En_24_Chapter.xhtml</a></li> </ul> <h2 id="glibc">glibc<a class="anchor" href="#glibc">#</a></h2> <ul> <li><a href="https://sourceware.org/glibc/manual/2.43/html_mono/libc.html#Streams">https://sourceware.org/glibc/manual/2.43/html_mono/libc.html#Streams</a></li> </ul> <h2 id="books">Books<a class="anchor" href="#books">#</a></h2> <figure><a href="https://learning.oreilly.com/library/view/learn-to-program/9781484274378/"><img src="https://monjiapawne.github.io/blog/images/jonathanbarlett.png" alt="asm book" width="200"></a> </figure> <ul> <li>Learn to Program with Assembly: Foundational Learning for New Programmers - Jonathan Bartlett</li> </ul>https://monjiapawne.github.io/blog/docs/x86-64/concepts/Mon, 01 Jan 0001 00:00:00 +0000https://monjiapawne.github.io/blog/docs/x86-64/concepts/<h1 id="x86-64-att-syntax">x86-64 (AT&amp;T Syntax)<a class="anchor" href="#x86-64-att-syntax">#</a></h1> <h2 id="abi">ABI<a class="anchor" href="#abi">#</a></h2> <p>ABI - Application Binary Interface is a type of convention for function calls, similar to how there is for syscalls. The ABI that linux uses is called - <strong>System V ABI</strong></p> <blockquote class='book-hint '> <p><strong>Q:</strong> Why do I care? Why should I follow their convention?</p> </blockquote><p>It allows you to call functions written by other people, even in other programming languages and allows you to estimate the behavior and safety of your registers/stack.</p>https://monjiapawne.github.io/blog/docs/x86-64/examples/Mon, 01 Jan 0001 00:00:00 +0000https://monjiapawne.github.io/blog/docs/x86-64/examples/<h1 id="examples">Examples<a class="anchor" href="#examples">#</a></h1> <h2 id="glibc-function-call-fprintf">glibc function call fprintf<a class="anchor" href="#glibc-function-call-fprintf">#</a></h2> <div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#000;-moz-tab-size:4;-o-tab-size:4;tab-size:4;-webkit-text-size-adjust:none;"><code class="language-gas" data-lang="gas"><span style="display:flex;"><span><span style="color:#0f0"># Prints &#34;25&#34; to stdout </span></span></span><span style="display:flex;"><span><span style="color:#0f0"># build: gcc -static print_example.s </span></span></span><span style="display:flex;"><span>.globl <span style="color:#7fffd4">main</span> </span></span><span style="display:flex;"><span>.section <span style="color:#7fffd4">.data</span> </span></span><span style="display:flex;"><span>fmt_int: </span></span><span style="display:flex;"><span> .ascii <span style="color:#87ceeb">&#34;%d\n\0&#34;</span> </span></span><span style="display:flex;"><span>.section <span style="color:#7fffd4">.text</span> </span></span><span style="display:flex;"><span>main: </span></span><span style="display:flex;"><span> <span style="color:#ff0">movq</span> <span style="color:#7fffd4">stdout</span>, <span style="color:#eedd82">%rdi</span> <span style="color:#0f0"># arg1: FILE* stdout </span></span></span><span style="display:flex;"><span> <span style="color:#ff0">movq</span> <span style="color:#7fffd4">$fmt_int</span>, <span style="color:#eedd82">%rsi</span> <span style="color:#0f0"># arg2: format string </span></span></span><span style="display:flex;"><span> <span style="color:#ff0">movq</span> <span style="color:#7fffd4">$25</span>, <span style="color:#eedd82">%rdx</span> <span style="color:#0f0"># arg3: integer to print </span></span></span><span style="display:flex;"><span> <span style="color:#ff0">movq</span> <span style="color:#7fffd4">$0</span>, <span style="color:#eedd82">%rax</span> <span style="color:#0f0"># no floating-point args (required by ABI) </span></span></span><span style="display:flex;"><span> <span style="color:#ff0">call</span> <span style="color:#7fffd4">fprintf</span> <span style="color:#0f0"># fprintf(stdout, &#34;%d\n&#34;, 25) </span></span></span><span style="display:flex;"><span> </span></span><span style="display:flex;"><span> <span style="color:#ff0">mov</span> <span style="color:#7fffd4">$0</span>, <span style="color:#eedd82">%rax</span> </span></span><span style="display:flex;"><span> <span style="color:#ff0">ret</span></span></span></code></pre></div>