wasmtime/profiling_agent/
perfmap.rs

1use crate::prelude::*;
2use crate::profiling_agent::ProfilingAgent;
3use std::io::{self, BufWriter, Write};
4use std::process;
5use std::{fs::File, sync::Mutex};
6
7/// Process-wide perf map file. Perf only reads a unique file per process.
8static PERFMAP_FILE: Mutex<Option<BufWriter<File>>> = Mutex::new(None);
9
10/// Interface for driving the creation of jitdump files
11struct PerfMapAgent;
12
13/// Initialize a JitDumpAgent and write out the header.
14pub fn new() -> Result<Box<dyn ProfilingAgent>> {
15    let mut file = PERFMAP_FILE.lock().unwrap();
16    if file.is_none() {
17        let filename = format!("/tmp/perf-{}.map", process::id());
18        *file = Some(BufWriter::new(File::create(filename)?));
19    }
20    Ok(Box::new(PerfMapAgent))
21}
22
23impl PerfMapAgent {
24    fn make_line(writer: &mut dyn Write, name: &str, code: &[u8]) -> io::Result<()> {
25        // Format is documented here: https://github.com/torvalds/linux/blob/master/tools/perf/Documentation/jit-interface.txt
26        // Try our best to sanitize the name, since wasm allows for any utf8 string in there.
27        let sanitized_name = name.replace('\n', "_").replace('\r', "_");
28        write!(
29            writer,
30            "{:p} {:x} {}\n",
31            code.as_ptr(),
32            code.len(),
33            sanitized_name
34        )?;
35        writer.flush()?;
36        Ok(())
37    }
38}
39
40impl ProfilingAgent for PerfMapAgent {
41    fn register_function(&self, name: &str, code: &[u8]) {
42        let mut file = PERFMAP_FILE.lock().unwrap();
43        let file = file.as_mut().unwrap();
44        if let Err(err) = Self::make_line(file, name, code) {
45            eprintln!("Error when writing import trampoline info to the perf map file: {err}");
46        }
47    }
48}
wasmtime/profiling_agent/perfmap.rs

wasmtime/profiling_agent/
perfmap.rs
