Re: [PATCH v3] perf symbols: Apply the symfs flat layout to the composed filename

[sashiko-bot@kernel.org]

> --symfs=<dir>,flat documents itself as matching only the base name, so a
> debuginfo lookup for /usr/lib/x86_64-linux-gnu/libc.so.6 should land on
> <dir>/libc.so.6.debug.  It lands on
> <dir>/debug/usr/lib/x86_64-linux-gnu/libc.so.6.debug instead, because the
> layout is applied to a fixed prefix and the file name arrives afterwards:
> 
> 	len = __symbol__join_symfs(filename, size, "/usr/lib/debug");
> 	snprintf(filename + len, size - len, "%s.debug", dso__long_name(dso));
> 
> perf_basename() only ever sees "/usr/lib/debug", so neither layout comes
> out of it.
> 
> Compose the path as it would appear on the profiled system and join it
> once, which puts the layout on the whole name.  That covers
> FEDORA_DEBUGINFO, UBUNTU_DEBUGINFO, MIXEDUP_UBUNTU_DEBUGINFO,
> [ ... ]
> 
> With --symfs /s,flat the lookups are now /s/libc.so.6, /s/libc.so.6.debug,
> /s/sleep and /s/<build id>.debug.  hierarchy is unchanged.
> 
> Signed-off-by: Zhan Xusheng <zhanxusheng@xiaomi.com>

Sashiko has reviewed this patch and found no issues. It looks great!

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Sashiko AI review · https://sashiko.dev/#/patchset/20260922131952.2922816-1-zhanxusheng@xiaomi.com?part=1