Re: [PATCH 1/3] perf libdw: Optimize fallback logic for missing DWARF

[sashiko-bot@kernel.org]

> When libdw encounters a DWARF definition it cannot accurately un-inline
> or an address block natively missing structural line maps,
> dwfl_module_getsrc() returns NULL. Previously, libdw__addr2line()
> returned -1 in both dwfl_module_getdwarf() and dwfl_module_getsrc()
> failure paths while addr2line() in srcline.c only stopped its fallback
> loop on ret > 0. This caused perf's addr2line_style loop to fall back to
> llvm, libbfd, and the cmd__addr2line() subprocess wrapper on every
> unmapped address or stripped DSO.
> 
> Update the addr2line_style pipeline return semantics consistently:
> 1. Backends return 0 to denote conclusively missing information
>    (e.g. valid ELF but no DWARF inside, or parsed DWARF with no mapped
>    lines), stopping the fallback loop.
> 2. Backends (and uncompiled stubs) return < 0 to denote initialization
>    or backend errors, instructing the loop to iterate to the next
>    configured fallback.
> 3. Backends return > 0 on successful source line resolution.
> 
> Fixes: bf96e296d52d ("perf libdw: Fix Dwfl discovery with split files")
> Signed-off-by: Ian Rogers <irogers@google.com>

Sashiko has reviewed this patch and found no issues.

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