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<!DOCTYPE html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta name="generator" content="rustdoc"><meta name="description" content="Source of the Rust file `src/rt.rs`."><title>rt.rs - source</title><script>if(window.location.protocol!=="file:")document.head.insertAdjacentHTML("beforeend","SourceSerif4-Regular-46f98efaafac5295.ttf.woff2,FiraSans-Regular-018c141bf0843ffd.woff2,FiraSans-Medium-8f9a781e4970d388.woff2,SourceCodePro-Regular-562dcc5011b6de7d.ttf.woff2,SourceCodePro-Semibold-d899c5a5c4aeb14a.ttf.woff2".split(",").map(f=>`<link rel="preload" as="font" type="font/woff2" crossorigin href="../../static.files/${f}">`).join(""))</script><link rel="stylesheet" href="../../static.files/normalize-76eba96aa4d2e634.css"><link rel="stylesheet" href="../../static.files/rustdoc-b0742ba02757f159.css"><meta name="rustdoc-vars" data-root-path="../../" data-static-root-path="../../static.files/" data-current-crate="juicebox_asm" data-themes="" data-resource-suffix="" data-rustdoc-version="1.83.0 (90b35a623 2024-11-26)" data-channel="1.83.0" data-search-js="search-f0d225181b97f9a4.js" data-settings-js="settings-805db61a62df4bd2.js" ><script src="../../static.files/storage-1d39b6787ed640ff.js"></script><script defer src="../../static.files/src-script-e66d777a5a92e9b2.js"></script><script defer src="../../src-files.js"></script><script defer src="../../static.files/main-f070b9041d14864c.js"></script><noscript><link rel="stylesheet" href="../../static.files/noscript-0111fcff984fae8f.css"></noscript><link rel="alternate icon" type="image/png" href="../../static.files/favicon-32x32-422f7d1d52889060.png"><link rel="icon" type="image/svg+xml" href="../../static.files/favicon-2c020d218678b618.svg"></head><body class="rustdoc src"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><div class="src-sidebar-title"><h2>Files</h2></div></nav><div class="sidebar-resizer"></div><main><rustdoc-search></rustdoc-search><section id="main-content" class="content"><div class="main-heading"><h1><div class="sub-heading">juicebox_asm/</div>rt.rs</h1><rustdoc-toolbar></rustdoc-toolbar></div><div class="example-wrap"><div data-nosnippet><pre class="src-line-numbers">
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<a href="#264" id="264">264</a></pre></div><pre class="rust"><code><span class="doccomment">//! Simple `mmap`ed runtime.
//!
//! This runtime supports adding code to executable pages and turn the added code into user
//! specified function pointer.
</span><span class="attr">#[cfg(not(target_os = <span class="string">"linux"</span>))]
</span><span class="macro">compile_error!</span>(<span class="string">"This runtime is only supported on linux"</span>);
<span class="kw">mod </span>perf {
<span class="kw">use </span>std::fs;
<span class="kw">use </span>std::io::Write;
<span class="doccomment">/// Provide support for the simple [perf jit interface][perf-jit].
///
/// This allows a simple (static) jit runtime to generate meta data describing the generated
/// functions, which is used during post-processing by `perf report` to symbolize addresses
/// captured while executing jitted code.
///
/// By the nature of this format, this can not be used for dynamic jit runtimes, which reuses
/// memory which previously contained jitted code.
///
/// [perf-jit]: https://elixir.bootlin.com/linux/v6.6.6/source/tools/perf/Documentation/jit-interface.txt
</span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">struct </span>PerfMap {
file: std::fs::File,
}
<span class="kw">impl </span>PerfMap {
<span class="doccomment">/// Create an empty perf map file.
</span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>new() -> <span class="self">Self </span>{
<span class="kw">let </span>name = <span class="macro">format!</span>(<span class="string">"/tmp/perf-{}.map"</span>, <span class="kw">unsafe </span>{ libc::getpid() });
<span class="kw">let </span>file = fs::OpenOptions::new()
.truncate(<span class="bool-val">true</span>)
.create(<span class="bool-val">true</span>)
.write(<span class="bool-val">true</span>)
.open(<span class="kw-2">&</span>name)
.unwrap_or_else(|<span class="kw">_</span>| <span class="macro">panic!</span>(<span class="string">"Failed to open perf map file {}"</span>, <span class="kw-2">&</span>name));
PerfMap { file }
}
<span class="doccomment">/// Add an entry to the perf map file.
</span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>add_entry(<span class="kw-2">&mut </span><span class="self">self</span>, start: usize, len: usize) {
<span class="comment">// Each line has the following format, fields separated with spaces:
// START SIZE NAME
//
// START and SIZE are hex numbers without 0x.
// NAME is the rest of the line, so it could contain special characters.
</span><span class="macro">writeln!</span>(<span class="self">self</span>.file, <span class="string">"{:x} {:x} jitfn_{:x}"</span>, start, len, start)
.expect(<span class="string">"Failed to write PerfMap entry"</span>);
}
}
}
<span class="doccomment">/// A simple `mmap`ed runtime with executable pages.
</span><span class="kw">pub struct </span>Runtime {
buf: <span class="kw-2">*mut </span>u8,
len: usize,
idx: usize,
perf: <span class="prelude-ty">Option</span><perf::PerfMap>,
}
<span class="kw">impl </span>Runtime {
<span class="doccomment">/// Create a new [Runtime].
///
/// # Panics
///
/// Panics if the `mmap` call fails.
</span><span class="kw">pub fn </span>new() -> Runtime {
<span class="comment">// Allocate a single page.
</span><span class="kw">let </span>len = <span class="number">4096</span>;
<span class="kw">let </span>buf = <span class="kw">unsafe </span>{
libc::mmap(
std::ptr::null_mut(),
len,
libc::PROT_NONE,
libc::MAP_PRIVATE | libc::MAP_ANONYMOUS,
<span class="number">0</span>, <span class="comment">/* fd */
</span><span class="number">0</span>, <span class="comment">/* off */
</span>) <span class="kw">as </span><span class="kw-2">*mut </span>u8
};
<span class="macro">assert_ne!</span>(
buf.cast(),
libc::MAP_FAILED,
<span class="string">"Failed to mmap runtime code page"
</span>);
Runtime {
buf,
len,
idx: <span class="number">0</span>,
perf: <span class="prelude-val">None</span>,
}
}
<span class="doccomment">/// Create a new [Runtime] which also generates static perf metat data.
///
/// For each function added to the [Runtime], an entry will be generated in the
/// `/tmp/perf-<PID>.map` file, which `perf report` uses to symbolicate unknown addresses.
/// This is applicable for static runtimes only.
///
/// # Panics
///
/// Panics if the `mmap` call fails.
</span><span class="kw">pub fn </span>with_profile() -> Runtime {
<span class="kw">let </span><span class="kw-2">mut </span>rt = Runtime::new();
rt.perf = <span class="prelude-val">Some</span>(perf::PerfMap::new());
rt
}
<span class="doccomment">/// Add the block of `code` to the runtime and a get function pointer of type `F`.
///
/// # Panics
///
/// Panics if the `code` does not fit on the `mmap`ed pages or is empty.
///
/// # Safety
///
/// The code added must fulfill the ABI of the specified function `F` and the returned function
/// pointer is only valid until the [`Runtime`] is dropped.
///
/// # Examples
///
/// ```
/// let mut rt = juicebox_asm::Runtime::new();
///
/// let code = [ 0x90 /* nop */, 0xc3 /* ret */ ];
/// let nop = unsafe { rt.add_code::<extern "C" fn()>(&code) };
///
/// nop();
/// ```
</span><span class="kw">pub unsafe fn </span>add_code<F>(<span class="kw-2">&mut </span><span class="self">self</span>, code: <span class="kw">impl </span>AsRef<[u8]>) -> F {
<span class="comment">// Get pointer to start of next free byte.
</span><span class="macro">assert!</span>(<span class="self">self</span>.idx < <span class="self">self</span>.len, <span class="string">"Runtime code page full"</span>);
<span class="kw">let </span>fn_start = <span class="self">self</span>.buf.add(<span class="self">self</span>.idx);
<span class="comment">// Copy over code.
</span><span class="kw">let </span>code = code.as_ref();
<span class="macro">assert!</span>(!code.is_empty(), <span class="string">"Adding empty code not supported"</span>);
<span class="macro">assert!</span>(
code.len() <= (<span class="self">self</span>.len - <span class="self">self</span>.idx),
<span class="string">"Code does not fit on the runtime code page"
</span>);
<span class="self">self</span>.unprotect();
<span class="kw">unsafe </span>{ std::ptr::copy_nonoverlapping(code.as_ptr(), fn_start, code.len()) };
<span class="self">self</span>.protect();
<span class="comment">// Increment index to next free byte.
</span><span class="self">self</span>.idx += code.len();
<span class="comment">// Add perf map entry.
</span><span class="kw">if let </span><span class="prelude-val">Some</span>(map) = <span class="kw-2">&mut </span><span class="self">self</span>.perf {
map.add_entry(fn_start <span class="kw">as </span>usize, code.len());
}
<span class="comment">// Return function to newly added code.
</span><span class="kw">unsafe </span>{ <span class="self">Self</span>::as_fn::<F>(fn_start) }
}
<span class="doccomment">/// Disassemble the code currently added to the runtime, using
/// [`ndisasm`](https://nasm.us/index.php) and print it to _stdout_. If
/// `ndisasm` is not available on the system this prints a warning and
/// becomes a nop.
///
/// # Panics
///
/// Panics if anything goes wrong with spawning, writing to or reading from
/// the `ndisasm` child process.
</span><span class="kw">pub fn </span>disasm(<span class="kw-2">&</span><span class="self">self</span>) {
<span class="macro">assert!</span>(<span class="self">self</span>.idx <= <span class="self">self</span>.len);
<span class="kw">crate</span>::disasm::disasm(<span class="kw">unsafe </span>{ core::slice::from_raw_parts(<span class="self">self</span>.buf, <span class="self">self</span>.idx) });
}
<span class="doccomment">/// Reinterpret the block of code pointed to by `fn_start` as `F`.
</span><span class="attr">#[inline]
</span><span class="kw">unsafe fn </span>as_fn<F>(fn_start: <span class="kw-2">*mut </span>u8) -> F {
<span class="kw">unsafe </span>{ std::mem::transmute_copy(<span class="kw-2">&</span>fn_start) }
}
<span class="doccomment">/// Add write protection the underlying code page(s).
///
/// # Panics
///
/// Panics if the `mprotect` call fails.
</span><span class="kw">fn </span>protect(<span class="kw-2">&mut </span><span class="self">self</span>) {
<span class="kw">unsafe </span>{
<span class="comment">// Remove write permissions from code page and allow to read-execute from it.
</span><span class="kw">let </span>ret = libc::mprotect(<span class="self">self</span>.buf.cast(), <span class="self">self</span>.len, libc::PROT_READ | libc::PROT_EXEC);
<span class="macro">assert_eq!</span>(ret, <span class="number">0</span>, <span class="string">"Failed to RX mprotect runtime code page"</span>);
}
}
<span class="doccomment">/// Remove write protection the underlying code page(s).
///
/// # Panics
///
/// Panics if the `mprotect` call fails.
</span><span class="kw">fn </span>unprotect(<span class="kw-2">&mut </span><span class="self">self</span>) {
<span class="kw">unsafe </span>{
<span class="comment">// Add write permissions to code page.
</span><span class="kw">let </span>ret = libc::mprotect(<span class="self">self</span>.buf.cast(), <span class="self">self</span>.len, libc::PROT_WRITE);
<span class="macro">assert_eq!</span>(ret, <span class="number">0</span>, <span class="string">"Failed to W mprotect runtime code page"</span>);
}
}
}
<span class="kw">impl </span>Drop <span class="kw">for </span>Runtime {
<span class="doccomment">/// Unmaps the code page. This invalidates all the function pointer returned by
/// [`Runtime::add_code`].
</span><span class="kw">fn </span>drop(<span class="kw-2">&mut </span><span class="self">self</span>) {
<span class="kw">unsafe </span>{
<span class="kw">let </span>ret = libc::munmap(<span class="self">self</span>.buf.cast(), <span class="self">self</span>.len);
<span class="macro">assert_eq!</span>(ret, <span class="number">0</span>, <span class="string">"Failed to munmap runtime"</span>);
}
}
}
<span class="attr">#[cfg(test)]
</span><span class="kw">mod </span>test {
<span class="kw">use super</span>::<span class="kw-2">*</span>;
<span class="attr">#[test]
</span><span class="kw">fn </span>test_code_max_size() {
<span class="kw">let </span><span class="kw-2">mut </span>rt = Runtime::new();
<span class="kw">let </span>code = [<span class="number">0u8</span>; <span class="number">4096</span>];
<span class="kw">unsafe </span>{
rt.add_code::<<span class="kw">extern </span><span class="string">"C" </span><span class="kw">fn</span>()>(code);
}
}
<span class="attr">#[test]
#[should_panic]
</span><span class="kw">fn </span>test_code_max_size_plus_1() {
<span class="kw">let </span><span class="kw-2">mut </span>rt = Runtime::new();
<span class="kw">let </span>code = [<span class="number">0u8</span>; <span class="number">4097</span>];
<span class="kw">unsafe </span>{
rt.add_code::<<span class="kw">extern </span><span class="string">"C" </span><span class="kw">fn</span>()>(code);
}
}
<span class="attr">#[test]
#[should_panic]
</span><span class="kw">fn </span>test_code_max_size_plus_1_2() {
<span class="kw">let </span><span class="kw-2">mut </span>rt = Runtime::new();
<span class="kw">let </span>code = [<span class="number">0u8</span>; <span class="number">4096</span>];
<span class="kw">unsafe </span>{
rt.add_code::<<span class="kw">extern </span><span class="string">"C" </span><span class="kw">fn</span>()>(code);
}
<span class="kw">let </span>code = [<span class="number">0u8</span>; <span class="number">1</span>];
<span class="kw">unsafe </span>{
rt.add_code::<<span class="kw">extern </span><span class="string">"C" </span><span class="kw">fn</span>()>(code);
}
}
<span class="attr">#[test]
#[should_panic]
</span><span class="kw">fn </span>test_empty_code() {
<span class="kw">let </span><span class="kw-2">mut </span>rt = Runtime::new();
<span class="kw">let </span>code = [<span class="number">0u8</span>; <span class="number">0</span>];
<span class="kw">unsafe </span>{
rt.add_code::<<span class="kw">extern </span><span class="string">"C" </span><span class="kw">fn</span>()>(code);
}
}
}
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