Re: [PATCH] perf symbol: Do not use debug file as the binary type

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] The patch fails to apply the instruction trace fix to kernel modules, leaving them vulnerable to the exact same decoding error.
--

--- Patch [1]: [PATCH] perf symbol: Do not use debug file as the binary type ---
commit af2af0a33f456210f477b124b3165ecd7e50b2ad
Author: Adrian Hunter <adrian.hunter@intel.com>

perf symbol: Do not use debug file as the binary type

This commit updates dso__load() to prefer files that contain executed
instructions over debug-only files (like .gnu-debuglink) for the binary
type. It achieves this by explicitly favoring build ID cache files and
system path DSOs over previously discovered debug files.

Closes: https://lore.kernel.org/all/CAGH6UiG=RJLqBU3kLu9XJciPyPO1HZkbAPERguVUMRuWQgqf=A@mail.gmail.com/

> diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
> index 94f9c8faeddab..3587ad2431590 100644
> --- a/tools/perf/util/symbol.c
> +++ b/tools/perf/util/symbol.c
> @@ -1947,7 +1947,16 @@ int dso__load(struct dso *dso, struct map *map)
>  		if (next_slot) {
>  			ss_pos++;
>  
> -			if (dso__binary_type(dso) == DSO_BINARY_TYPE__NOT_FOUND)
> +			/*
> +			 * The binary type is used to find the file containing
> +			 * the executed instructions, so prefer the types that
> +			 * refer to the actual object over debug-only files such
> +			 * as DSO_BINARY_TYPE__DEBUGLINK.
> +			 */
> +			if (dso__binary_type(dso) == DSO_BINARY_TYPE__NOT_FOUND ||
> +			    symtab_type == DSO_BINARY_TYPE__BUILD_ID_CACHE ||
> +			    (symtab_type == DSO_BINARY_TYPE__SYSTEM_PATH_DSO &&
> +			     dso__binary_type(dso) != DSO_BINARY_TYPE__BUILD_ID_CACHE))

[Severity: Medium]
Does this new condition also need to check for kernel module object types
like DSO_BINARY_TYPE__SYSTEM_PATH_KMODULE?

If a trace contains kernel module execution and the module's debuginfo is
cached in the perf build-id cache, dso__load() might encounter the
debuginfo file first. When the actual kernel module binary is found
later, the check above will fail because it strictly looks for
DSO_BINARY_TYPE__SYSTEM_PATH_DSO.

Could this leave kernel modules vulnerable to the same decoding errors,
where the debuginfo file is retained and produces wrong instructions
during Intel PT decoding?

>  				dso__set_binary_type(dso, symtab_type);
>  
>  			if (syms_ss && runtime_ss)

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260825062345.115073-1-adrian.hunter@intel.com?part=1