Re: [PATCH 2/3] perf annotate: fall back to original binary if build-id cache entry is not a valid ELF

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] Spurious warning emitted for missing build-id cache files and valid kallsyms cache entries.
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commit 4a56442e475b7351d0cee0b5ef94464e2d112fe2
Author: Athira Rajeev <atrajeev@linux.ibm.com>

perf annotate: fall back to original binary if build-id cache entry is not a valid ELF

This commit adds a check to verify that a build-id cache file is actually a
valid ELF before passing it to objdump. If the file is not a valid ELF, it
emits a warning and falls back to the original binary path.

> diff --git a/tools/perf/util/disasm.c b/tools/perf/util/disasm.c
> index 6cfdbabbb8c7d..e263a2a8715dd 100644
> --- a/tools/perf/util/disasm.c
> +++ b/tools/perf/util/disasm.c
> @@ -1201,6 +1201,12 @@ static int dso__disassemble_filename(struct dso *dso, char *filename, size_t fil
>  	if (len < 0)
>  		goto fallback;
>  
> +	if (!is_valid_elf(filename)) {
> +		pr_warning("build-id cache file is not a valid ELF, falling back to original binary: %s\n",
> +			filename);
> +		goto fallback;
> +	}
> +

[Severity: Medium]
Will this emit spurious warnings for missing build-id cache files or valid 
kallsyms cache entries?

When perf annotate looks up a build-id and finds a kallsyms entry (which is a 
plain text copy of /proc/kallsyms, not an ELF) or a dangling symlink (missing 
file), the newly added is_valid_elf() check evaluates to false.

Because this check is placed before the original access() and 
strstr(..., DSO__NAME_KALLSYMS) checks, it preempts the expected silent 
fallback paths and prints a warning.

>  	linkname[len] = '\0';
>  	if (strstr(linkname, DSO__NAME_KALLSYMS) ||
>  		access(filename, R_OK)) {
> fallback:

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Sashiko AI review · https://sashiko.dev/#/patchset/20260907034554.714-1-atrajeev@linux.ibm.com?part=2