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author | Akshay <[email protected]> | 2020-04-16 09:10:50 +0100 |
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committer | Akshay <[email protected]> | 2020-04-16 09:10:50 +0100 |
commit | 2a778912251874f9b808f82e61244efcd12210aa (patch) | |
tree | 72cd692749c36f068fe22a32ede51a88a65bc759 /docs/posts/call_to_ARMs/index.html | |
parent | d71a288d944959057064d64ce03cad759a42ba06 (diff) |
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37 | Call To ARMs | 37 | Call To ARMs |
38 | </h1> | 38 | </h1> |
39 | <div class="post-text"> | 39 | <div class="post-text"> |
40 | <p>My 4th semester involves ARM programming. And proprietary | 40 | <!DOCTYPE html> |
41 | tooling (Keil C). But we don't do that here.</p> | 41 | <html xmlns="http://www.w3.org/1999/xhtml" lang="" xml:lang=""> |
42 | 42 | <head> | |
43 | <h3 id="Building">Building</h3> | 43 | <meta charset="utf-8" /> |
44 | 44 | <meta name="generator" content="pandoc" /> | |
45 | <p>Assembling and linking ARM binaries on non-ARM architecture | 45 | <meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=yes" /> |
46 | devices is fairly trivial. I went along with the GNU cross | 46 | <title>call_to_ARMs</title> |
47 | bare metal toolchain binutils, which provides <code>arm-as</code> and | 47 | <style> |
48 | <code>arm-ld</code> (among a bunch of other utils that I don't care | 48 | code{white-space: pre-wrap;} |
49 | about for now). </p> | 49 | span.smallcaps{font-variant: small-caps;} |
50 | 50 | span.underline{text-decoration: underline;} | |
51 | div.column{display: inline-block; vertical-align: top; width: 50%;} | ||
52 | div.hanging-indent{margin-left: 1.5em; text-indent: -1.5em;} | ||
53 | ul.task-list{list-style: none;} | ||
54 | </style> | ||
55 | <!--[if lt IE 9]> | ||
56 | <script src="//cdnjs.cloudflare.com/ajax/libs/html5shiv/3.7.3/html5shiv-printshiv.min.js"></script> | ||
57 | <![endif]--> | ||
58 | </head> | ||
59 | <body> | ||
60 | <p>My 4th semester involves ARM programming. And proprietary tooling (Keil C). But we don’t do that here.</p> | ||
61 | <h3 id="building">Building</h3> | ||
62 | <p>Assembling and linking ARM binaries on non-ARM architecture devices is fairly trivial. I went along with the GNU cross bare metal toolchain binutils, which provides <code>arm-as</code> and <code>arm-ld</code> (among a bunch of other utils that I don’t care about for now).</p> | ||
51 | <p>Assemble <code>.s</code> files with:</p> | 63 | <p>Assemble <code>.s</code> files with:</p> |
52 | 64 | <pre class="shell"><code>arm-none-eabi-as main.s -g -march=armv8.1-a -o main.out</code></pre> | |
53 | <pre><code class="language-shell">arm-none-eabi-as main.s -g -march=armv8.1-a -o main.out | 65 | <p>The <code>-g</code> flag generates extra debugging information that <code>gdb</code> picks up. The <code>-march</code> option establishes target architecture.</p> |
54 | </code></pre> | ||
55 | |||
56 | <p>The <code>-g</code> flag generates extra debugging information that | ||
57 | <code>gdb</code> picks up. The <code>-march</code> option establishes target | ||
58 | architecture.</p> | ||
59 | |||
60 | <p>Link <code>.o</code> files with:</p> | 66 | <p>Link <code>.o</code> files with:</p> |
61 | 67 | <pre class="shell"><code>arm-none-eabi-ld main.out -o main</code></pre> | |
62 | <pre><code class="language-shell">arm-none-eabi-ld main.out -o main | 68 | <h3 id="running-and-debugging">Running (and Debugging)</h3> |
63 | </code></pre> | 69 | <p>Things get interesting here. <code>gdb</code> on your x86 machine cannot read nor execute binaries compiled for ARM. So, we simulate an ARM processor using <code>qemu</code>. Now qemu allows you to run <code>gdbserver</code> on startup. Connecting our local <code>gdb</code> instance to <code>gdbserver</code> gives us a view into the program’s execution. Easy!</p> |
64 | 70 | <p>Run <code>qemu</code>, with <code>gdbserver</code> on port <code>1234</code>, with our ARM binary, <code>main</code>:</p> | |
65 | <h3 id="Running%20(and%20Debugging)">Running (and Debugging)</h3> | 71 | <pre class="shell"><code>qemu-arm -singlestep -g 1234 main</code></pre> |
66 | 72 | <p>Start up <code>gdb</code> on your machine, and connect to <code>qemu</code>’s <code>gdbserver</code>:</p> | |
67 | <p>Things get interesting here. <code>gdb</code> on your x86 machine | ||
68 | cannot read nor execute binaries compiled for ARM. So, we | ||
69 | simulate an ARM processor using <code>qemu</code>. Now qemu allows you | ||
70 | to run <code>gdbserver</code> on startup. Connecting our local <code>gdb</code> | ||
71 | instance to <code>gdbserver</code> gives us a view into the program’s | ||
72 | execution. Easy!</p> | ||
73 | |||
74 | <p>Run <code>qemu</code>, with <code>gdbserver</code> on port <code>1234</code>, with our ARM | ||
75 | binary, <code>main</code>:</p> | ||
76 | |||
77 | <pre><code class="language-shell">qemu-arm -singlestep -g 1234 main | ||
78 | </code></pre> | ||
79 | |||
80 | <p>Start up <code>gdb</code> on your machine, and connect to <code>qemu</code>’s | ||
81 | <code>gdbserver</code>:</p> | ||
82 | |||
83 | <pre><code>(gdb) set architecture armv8-a | 73 | <pre><code>(gdb) set architecture armv8-a |
84 | (gdb) target remote localhost:1234 | 74 | (gdb) target remote localhost:1234 |
85 | (gdb) file main | 75 | (gdb) file main |
86 | Reading symbols from main... # yay! | 76 | Reading symbols from main... # yay!</code></pre> |
87 | </code></pre> | 77 | <h3 id="gdb-enhanced">GDB Enhanced</h3> |
88 | 78 | <p><code>gdb</code> is cool, but it’s not nearly as comfortable as well fleshed out emulators/IDEs like Keil. Watching registers, CPSR and memory chunks update <em>is</em> pretty fun.</p> | |
89 | <h3 id="GDB%20Enhanced">GDB Enhanced</h3> | 79 | <p>I came across <code>gdb</code>’s TUI mode (hit <code>C-x C-a</code> or type <code>tui enable</code> at the prompt). TUI mode is a godsend. It highlights the current line of execution, shows you disassembly outputs, updated registers, active breakpoints and more.</p> |
90 | |||
91 | <p><code>gdb</code> is cool, but it's not nearly as comfortable as well | ||
92 | fleshed out emulators/IDEs like Keil. Watching registers, | ||
93 | CPSR and memory chunks update <em>is</em> pretty fun. </p> | ||
94 | |||
95 | <p>I came across <code>gdb</code>'s TUI mode (hit <code>C-x C-a</code> or type <code>tui | ||
96 | enable</code> at the prompt). TUI mode is a godsend. It highlights | ||
97 | the current line of execution, shows you disassembly | ||
98 | outputs, updated registers, active breakpoints and more.</p> | ||
99 | |||
100 | <p><em>But</em>, it is an absolute eyesore.</p> | 80 | <p><em>But</em>, it is an absolute eyesore.</p> |
101 | 81 | <p>Say hello to <a href="https://github.com/hugsy/gef">GEF</a>! “GDB Enhanced Features” teaches our old dog some cool new tricks. Here are some additions that made my ARM debugging experience loads better:</p> | |
102 | <p>Say hello to <a href="https://github.com/hugsy/gef">GEF</a>! “GDB | ||
103 | Enhanced Features” teaches our old dog some cool new tricks. | ||
104 | Here are some additions that made my ARM debugging | ||
105 | experience loads better:</p> | ||
106 | |||
107 | <ul> | 82 | <ul> |
108 | <li>Memory watches</li> | 83 | <li>Memory watches</li> |
109 | <li>Register watches, with up to 7 levels of deref (overkill, | 84 | <li>Register watches, with up to 7 levels of deref (overkill, I agree)</li> |
110 | I agree)</li> | ||
111 | <li>Stack tracing</li> | 85 | <li>Stack tracing</li> |
112 | </ul> | 86 | </ul> |
113 | 87 | <p>And it’s pretty! See for yourself:</p> | |
114 | <p>And it's pretty! See for yourself:</p> | 88 | <p><a href="https://u.peppe.rs/wq.png"><img src="https://u.peppe.rs/wq.png" /></a></p> |
115 | 89 | <h3 id="editing">Editing</h3> | |
116 | <p><a href="https://u.peppe.rs/wq.png"><img src="https://u.peppe.rs/wq.png" alt="gef.png" /></a></p> | 90 | <p>Vim, with <code>syntax off</code> because it dosen’t handle GNU ARM syntax too well.</p> |
117 | 91 | </body> | |
118 | <h3 id="Editing">Editing</h3> | 92 | </html> |
119 | |||
120 | <p>Vim, with <code>syntax off</code> because it | ||
121 | dosen't handle GNU ARM syntax too well.</p> | ||
122 | 93 | ||
123 | </div> | 94 | </div> |
124 | 95 | ||