On August 28, 2025 5:51:39 PM GMT-03:00, Steven Rostedt <rost...@kernel.org>
wrote:
>On Thu, 28 Aug 2025 17:27:37 -0300
>Arnaldo Carvalho de Melo <arnaldo.m...@gmail.com> wrote:
>
>> >I would love to have a hash to use. The next patch does the mapping
>> >of the inode numbers to their path name. It can
>>
>> The path name is a nice to have detail, but a content based hash is
>> what we want, no?
>>
>> Tracing/profiling has to be about contents of files later used for
>> analysis, and filenames provide no guarantee about that.
>
>I could add the build id to the inode_cache as well (which I'll rename
>to file_cache).
>
>Thus, the user stack trace will just have the offset and a hash value
>that will be match the output of the file_cache event which will have
>the path name and a build id (if one exists).
>
>Would that work?
Probably.
This "if it is available" question is valid, but since 2016 it's is more of a
"did developers disabled it explicitly?"
If my "googling" isn't wrong, GNU LD defaults to generating a build ID in ELF
images since 2011 and clang's companion since 2016.
So making it even more available than what the BPF guys did long ago and perf
piggybacked on at some point, by having it cached, on request?, in some 20
bytes alignment hole in task_struct that would be only used when
profiling/tracing may be amenable.
- Arnaldo
