util: Query build-id by symbol address, not library name

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 two problems:

    - 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).

Cc: Jonathan Gray <[email protected]>
Reviewed-by: Matt Turner <[email protected]>
Reviewed-by: Emil Velikov <[email protected]>

1 files changed, 1 insertions, 1 deletions

diff --git a/src/util/build_id.h b/src/util/build_id.h
index 18641c44af2..86d611d8db7 100644
--- a/src/util/build_id.h
+++ b/src/util/build_id.h
@@ -29,7 +29,7 @@
 struct build_id_note;
 
 const struct build_id_note *
-build_id_find_nhdr(const char *filename);
+build_id_find_nhdr_for_addr(const void *addr);
 
 unsigned
 build_id_length(const struct build_id_note *note);