From 1e1a5df862d8f0739a2c72197fa1620987945f3a Mon Sep 17 00:00:00 2001
From: Johannes Stoelp <johannes.stoelp@gmail.com>
Date: Wed, 28 Feb 2024 18:55:10 +0100
Subject: rt: add perf static jit profile support
---
src/rt.rs | 62 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 60 insertions(+), 2 deletions(-)
(limited to 'src')
diff --git a/src/rt.rs b/src/rt.rs
index a27a67f..f468033 100644
--- a/src/rt.rs
+++ b/src/rt.rs
@@ -3,16 +3,62 @@
//! This runtime supports adding code to executable pages and turn the added code into user
//! specified function pointer.
-use nix::sys::mman::{mmap, mprotect, munmap, MapFlags, ProtFlags};
-
#[cfg(not(target_os = "linux"))]
compile_error!("This runtime is only supported on linux");
+use nix::sys::mman::{mmap, mprotect, munmap, MapFlags, ProtFlags};
+
+mod perf {
+ use std::fs;
+ use std::io::Write;
+
+ /// 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
+ pub(super) struct PerfMap {
+ file: std::fs::File,
+ }
+
+ impl PerfMap {
+ /// Create an empty perf map file.
+ pub(super) fn new() -> Self {
+ let name = format!("/tmp/perf-{}.map", nix::unistd::getpid());
+ let file = fs::OpenOptions::new()
+ .truncate(true)
+ .create(true)
+ .write(true)
+ .open(&name)
+ .unwrap_or_else(|_| panic!("Failed to open perf map file {}", &name));
+
+ PerfMap { file }
+ }
+
+ /// Add an entry to the perf map file.
+ pub(super) fn add_entry(&mut self, start: usize, len: usize) {
+ // 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.
+ writeln!(self.file, "{:x} {:x} jitfn_{:x}", start, len, start)
+ .expect("Failed to write PerfMap entry");
+ }
+ }
+}
+
/// A simple `mmap`ed runtime with executable pages.
pub struct Runtime {
buf: *mut u8,
len: usize,
idx: usize,
+ perf: Option<perf::PerfMap>,
}
impl Runtime {
@@ -40,9 +86,16 @@ impl Runtime {
buf,
len: len.get(),
idx: 0,
+ perf: None,
}
}
+ pub fn with_profile() -> Runtime {
+ let mut rt = Runtime::new();
+ rt.perf = Some(perf::PerfMap::new());
+ rt
+ }
+
/// Add the block of `code` to the runtime and a get function pointer of type `F`.
///
/// # Panics
@@ -83,6 +136,11 @@ impl Runtime {
// Increment index to next free byte.
self.idx += code.len();
+ // Add perf map entry.
+ if let Some(map) = &mut self.perf {
+ map.add_entry(fn_start as usize, code.len());
+ }
+
// Return function to newly added code.
unsafe { Self::as_fn::<F>(fn_start) }
}
--
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