Re: [PATCH v3 2/6] perf dwarf-aux: Fix libdw API contract violations

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] Returning `-EINVAL` when `dwarf_decl_line` fails for the root DIE breaks line walking for valid functions.
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commit c967da2fa8dfee2321c45ab4e1d42344eca760b5
Author: Ian Rogers <irogers@google.com>

perf dwarf-aux: Fix libdw API contract violations

This commit adds return value checks to dwarf_decl_line, dwarf_getfuncs,
and dwarf_lineaddr across dwarf-aux.c. It aims to prevent the use of
uninitialized stack variables or incorrectly reporting success on failure.

> diff --git a/tools/perf/util/dwarf-aux.c b/tools/perf/util/dwarf-aux.c
> index 8e83cb2d565e..1168e69a9292 100644
> --- a/tools/perf/util/dwarf-aux.c
> +++ b/tools/perf/util/dwarf-aux.c
[ ... ]
> @@ -949,7 +949,11 @@ int die_walk_lines(Dwarf_Die *rt_die, line_walk_callback_t callback, void *data)
>  	/* Get the CU die */
>  	if (dwarf_tag(rt_die) != DW_TAG_compile_unit) {
>  		cu_die = dwarf_diecu(rt_die, &die_mem, NULL, NULL);
> -		dwarf_decl_line(rt_die, &decl);
> +		if (dwarf_decl_line(rt_die, &decl) != 0) {
> +			pr_debug2("Failed to get the declared line number of %s\n",
> +				  dwarf_diename(rt_die));
> +			return -EINVAL;
> +		}

Does returning -EINVAL here break line walking for valid functions that
omit the declaration line attribute?

DWARF attributes like DW_AT_decl_line and DW_AT_decl_file are optional and
frequently omitted by compilers for assembly functions, artificial functions,
or compiler-generated thunks.

Before this change, if dwarf_decl_line() failed, decl remained 0 and
the function continued gracefully. Aborting with -EINVAL might prevent
tools like perf probe from working on valid functions.

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Sashiko AI review · https://sashiko.dev/#/patchset/20260503003552.1063540-1-irogers@google.com?part=2