[Mesa-dev] [PATCH] util: Query build-id by symbol address, not library name

[Chad Versace]

On Tue 12 Sep 2017, Matt Turner wrote:
> On Tue, Sep 12, 2017 at 5:05 PM, Chad Versace <chad at kiwitree.net> wrote:
> > This patch renames build_id_find_nhdr() to
> > build_id_find_nhdr_for_addr(), and changes it to never examine the
> > library name.
> >
> > Tested on Fedora by confirming that build_id_get_data() returns the same
> > build-id as the file(1) tool. For BSD, I confirmed that the API used
> > (dladdr() and struct Dl_info) is documented in FreeBSD's manpages.
> >
> > This solves several problems, some more realistic than others:
> >
> >     - We can now the query the build-id without knowing the installed library's
> >       filename.
> >
> >       This matters because Android requires specific filenames for HAL
> >       modules, such as "/vendor/lib/hw/vulkan.${board}.so". The HAL
> >       filenames do not follow the Unix convention of "libfoo.so".  In
> >       other words, the same query code will now work on Linux and Android.
> >
> >     - Querying the build-id now works correctly when the process
> >       contains multiple shared objects with the same basename.
> >       (Admittedly, this is a highly unlikely scenario).
> >
> >     - Querying the build-id now works correctly when the library is
> >       statically linked into the executable. (This even more unlikely
> >       than the previous scenario).
> 
> I assume this one is speculative? I'm not sure how the build-id ELF
> section could exist in a static archive, and I'm not sure how it could
> end up in a statically linked binary (much less more than one of
> them).

Yeah. My brain wasn't working when I wrote the last issue. I'll remove
it from the commit message.

> Otherwise, it looks like a nice change.
> 
> Reviewed-by: Matt Turner <mattst88 at gmail.com>
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