Wrong symbols for Rust binary

[zecakeh]

When profiling a Rust binary, it seems the symbols are not correct. Instead of the function names for all my binary I get fun_XXXX where XXXX is an hexadecimal number. However function names for C libraries we depend on are properly displayed.

I know that the symbols are available because using e.g. flamegraph, the proper function names show up.

I would like to help debug this but the only error I'm seeing is this in the web console:

17:38:33,589 SymbolsNotFoundError: Could not obtain symbols for [vdso]/000000000000000000000000000000000.
 - Error: The symbol server does not have symbols for [vdso]/000000000000000000000000000000000.
 - Error: No connection to the browser, cannot run querySymbolicationApi
 - Error: No connection to the browser, cannot obtain symbol tables
    Fi errors.js:16
    _getSymbolTablesFromBrowser symbol-store.js:504
symbolication.js:915:14

[mstange]

Is this on Linux or macOS? Can you share the binary and the profile.json file with me (e.g. by email)? Does this also reproduce with a samply compiled manually from the main branch of this repo?

[zecakeh]

This is on Linux, this is an open source project called Fractal. The problem still happens on the main branch.

I have investigated further, getting the symbols works fine if they are included in the binary. However as part of our release process, the debuginfo is split into a fractal.debug file with eu-strip from elfutils. The command is:

eu-strip --remove-comment --reloc-debug-sections -f fractal.debug

It's after this point that the symbols seem to not be found. The binary is in /app/bin/fractal and the debug file is in /usr/lib/debug/app/bin/fractal.debug so according to GDB's guide for separate debug files it should be found.

I have also tried placing fractal.debug alongside fractal, and in a .debug subfolder with the same result.

Finally, after some investigating, the culprit seems to be this function:

samply/wholesym/src/helper.rs

Lines 620 to 639 in 3e36c91

	fn get_candidate_paths_for_gnu_debug_link_dest(
	&self,
	debug_link_name: &str,
	) -> FileAndPathHelperResult<Vec<WholesymFileLocation>> {
	// https://www-zeuthen.desy.de/unix/unixguide/infohtml/gdb/Separate-Debug-Files.html
	Ok(vec![
	WholesymFileLocation::LocalFile(PathBuf::from(format!(
	"/usr/bin/{}.debug",
	&debug_link_name
	))),
	WholesymFileLocation::LocalFile(PathBuf::from(format!(
	"/usr/bin/.debug/{}.debug",
	&debug_link_name
	))),
	WholesymFileLocation::LocalFile(PathBuf::from(format!(
	"/usr/lib/debug/usr/bin/{}.debug",
	&debug_link_name
	))),
	])
	}

The binary's location is hardcoded as /usr/bin, but it shouldn't be.

I might have time to open a PR about that later today and to test it to make sure that's the only issue.