fix: validate jitdump filename PID matches MMAP2 record PID

Match perf's jit_detect() behavior: the PID embedded in the jitdump
filename must match the MMAP2 record's PID. Also fixes a bug where
rposition returned a usize that was incorrectly used as a byte slice.

Author: DaniPopes

src/executor/wall_time/perf/parse_perf_file.rs

@@ -111,7 +111,7 @@ pub fn parse_for_memmap2<P: AsRef<Path>>(
                 // Collect jitdump file paths before the PROT_EXEC filter in process_mmap2_record
                 // skips them. JIT runtimes mmap the jitdump file so perf records it.
                 // Match perf's jit_detect(): basename must be `jit-<pid>.dump`.
-                if is_jit_dump_path(&mmap2_record.path.as_slice()) {
+                if is_jit_dump_path(&mmap2_record.path.as_slice(), mmap2_record.pid) {
                     let path = PathBuf::from(
                         String::from_utf8_lossy(&mmap2_record.path.as_slice()).into_owned(),
                     );
@@ -180,21 +180,15 @@ impl PidFilter {
     }
 }
 
-/// Returns true if the path basename matches perf's jitdump pattern: `jit-<digits>.dump`.
-fn is_jit_dump_path(path: &[u8]) -> bool {
-    let basename = match path.iter().rposition(|&b| b == b'/') {
-        Some(pos) => &path[pos + 1..],
-        None => return false,
+/// Returns true if the path basename matches perf's `jit_detect()` pattern: `jit-<pid>.dump`,
+/// where `<pid>` must match the MMAP2 record's PID.
+fn is_jit_dump_path(path: &[u8], pid: pid_t) -> bool {
+    let Some(pos) = path.iter().rposition(|&b| b == b'/') else {
+        return false;
     };
-    let rest = match basename.strip_prefix(b"jit-") {
-        Some(rest) => rest,
-        None => return false,
-    };
-    let rest = match rest.strip_suffix(b".dump") {
-        Some(rest) => rest,
-        None => return false,
-    };
-    !rest.is_empty() && rest.iter().all(|b| b.is_ascii_digit())
+    let basename = &path[pos + 1..];
+    let expected = format!("jit-{pid}.dump");
+    basename == expected.as_bytes()
 }
 
 /// Process a single MMAP2 record and add it to the symbols and unwind data maps