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Fix loading kernel symbols from perf.data #734

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Merged
mstange merged 2 commits into from
Dec 22, 2025
Merged

Fix loading kernel symbols from perf.data #734

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e4d0c23
Fix loading kernel symbols from perf.data
DaniPopes Dec 19, 2025
3ff6f1d
Merge branch 'main' into cvt-load-kernel
mstange Dec 22, 2025
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146 changes: 78 additions & 68 deletions samply/src/linux_shared/converter.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -59,6 +59,8 @@ use crate::shared::unresolved_samples::{
};
use crate::shared::utils::open_file_with_fallback;

const PROT_EXEC: u32 = 0b100;

pub struct Converter<U>
where
U: Unwinder<Module = Module<MmapRangeOrVec>> + Default,
Expand Down Expand Up @@ -700,54 +702,39 @@ where
}

pub fn handle_mmap(&mut self, e: MmapRecord, timestamp: u64) {
let mut path = e.path.as_slice();
self.add_mmap_marker(e.pid, e.tid, &path, timestamp);

if self.check_jitdump_or_marker_file(&path, e.pid, e.tid) {
// Not a DSO.
return;
}

if e.page_offset == 0 {
self.pe_mappings.check_mmap(&path, e.address);
}

if !e.is_executable {
return;
}

let dso_key = match DsoKey::detect(&path, e.cpu_mode) {
Some(dso_key) => dso_key,
None => return,
};
let mut build_id = None;
if let Some(dso_info) = self.build_ids.get(&dso_key) {
build_id = Some(dso_info.build_id.to_owned());
// Overwrite the path from the mmap record with the path from the build ID info.
// These paths are usually the same, but in some cases the path from the build
// ID info can be "better". For example, the synthesized mmap event for the
// kernel vmlinux image usually has "[kernel.kallsyms]_text" whereas the build
// ID info might have the full path to a kernel debug file, e.g.
// "/usr/lib/debug/boot/vmlinux-4.16.0-1-amd64".
path = dso_info.path.to_owned().into();
}

if e.pid == -1 {
self.add_kernel_module(e.address, e.length, dso_key, build_id.as_deref(), &path);
} else {
self.add_module_to_process(
e.pid,
&path,
e.page_offset,
e.address,
e.length,
build_id.as_deref(),
timestamp,
);
}
let MmapRecord {
pid,
tid,
address,
length,
page_offset,
is_executable,
cpu_mode,
path,
} = e;
self.handle_mmap_inner(
Mmap2Record {
pid,
tid,
address,
length,
page_offset,
file_id: Mmap2FileId::BuildId(vec![]),
protection: if is_executable { PROT_EXEC } else { 0 },
flags: 0,
cpu_mode,
path,
},
timestamp,
false,
);
}

pub fn handle_mmap2(&mut self, e: Mmap2Record, timestamp: u64) {
self.handle_mmap_inner(e, timestamp, true);
}

fn handle_mmap_inner(&mut self, e: Mmap2Record, timestamp: u64, v2: bool) {
let path = e.path.as_slice();
self.add_mmap_marker(e.pid, e.tid, &path, timestamp);

Expand All @@ -766,41 +753,64 @@ where
self.pe_mappings.check_mmap(&path, e.address);
}

const PROT_EXEC: u32 = 0b100;
if e.protection & PROT_EXEC == 0 && !self.simpleperf.symbol_tables.user.contains_key(&*path)
let Some(dso_key) = DsoKey::detect(&path, e.cpu_mode) else {
return;
};

if matches!(dso_key, DsoKey::User { .. })
&& e.protection & PROT_EXEC == 0
&& !self.simpleperf.symbol_tables.user.contains_key(&*path)
{
// Ignore non-executable mappings.
// Ignore non-executable user mappings.
// Don't ignore mappings that simpleperf found symbols for, even if they're
// non-executable. TODO: Find out why .vdex and .jar mappings with symbols aren't
// non-executable.
// TODO: Find out why .vdex and .jar mappings with symbols aren't
// marked as executable in the simpleperf perf.data files. Is simpleperf simply
// forgetting to set the right flag? Or are these mappings synthetic? Are we
// actually running code from inside these mappings? Surely then the memory must
// be executable?
return;
}

let build_id = match &e.file_id {
Mmap2FileId::BuildId(build_id) => Some(build_id.to_owned()),
Mmap2FileId::InodeAndVersion(_) => {
let dso_key = match DsoKey::detect(&path, e.cpu_mode) {
Some(dso_key) => dso_key,
None => return,
};
self.build_ids
.get(&dso_key)
.map(|db| db.build_id.to_owned())
let inline_build_id = if v2 {
match &e.file_id {
Mmap2FileId::BuildId(build_id) => Some(build_id.as_slice()),
Mmap2FileId::InodeAndVersion(_) => None,
}
} else {
None
};

self.add_module_to_process(
e.pid,
&path,
e.page_offset,
e.address,
e.length,
build_id.as_deref(),
timestamp,
);
// Get build_id and potentially override path from build_ids map.
// These paths are usually the same, but in some cases the path from the build
// ID info can be "better". For example, the synthesized mmap event for the
// kernel vmlinux image usually has "[kernel.kallsyms]_text" whereas the build
// ID info might have the full path to a kernel debug file, e.g.
// "/usr/lib/debug/boot/vmlinux-4.16.0-1-amd64".
let (build_id, path) = match inline_build_id {
Some(build_id) => (Some(build_id.to_owned()), path),
None => match self.build_ids.get(&dso_key) {
Some(dso_info) => (
Some(dso_info.build_id.to_owned()),
dso_info.path.to_owned().into(),
),
None => (None, path),
},
};

if e.pid == -1 {
self.add_kernel_module(e.address, e.length, dso_key, build_id.as_deref(), &path);
} else {
self.add_module_to_process(
e.pid,
&path,
e.page_offset,
e.address,
e.length,
build_id.as_deref(),
timestamp,
);
}
}

fn check_jitdump_or_marker_file(&mut self, path: &[u8], pid: i32, tid: i32) -> bool {
Expand Down
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