perf symbols: we can now read separate debug-info files based on a build ID

Recent GDB (at least on a vanilla Debian box) looks for debug information in

  /usr/lib/debug/.build-id/nn/nnnnnnn

where nn/nnnnnn is the build-id of the stripped ELF binary. This is
documented here:

  https://sourceware.org/gdb/onlinedocs/gdb/Separate-Debug-Files.html

This was not working in perf because we didn't read the build id until
AFTER we searched for the separate debug information file. This patch
reads the build ID and THEN does the search.

Signed-off-by: Dima Kogan <dima@secretsauce.net>
Link: http://lkml.kernel.org/r/87si6pfwz4.fsf@secretsauce.net
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index e7bf0c46918d25592207b935ff5509a9be3841e4..71bf711a628cedceaf52d703f1992847e028c057 100644 (file)
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -1406,6 +1406,7 @@ int dso__load(struct dso *dso, struct map *map, symbol_filter_t filter)
        struct symsrc ss_[2];
        struct symsrc *syms_ss = NULL, *runtime_ss = NULL;
        bool kmod;
+       unsigned char build_id[BUILD_ID_SIZE];
 
        pthread_mutex_lock(&dso->lock);
 
@@ -1461,6 +1462,14 @@ int dso__load(struct dso *dso, struct map *map, symbol_filter_t filter)
                dso->symtab_type == DSO_BINARY_TYPE__GUEST_KMODULE ||
                dso->symtab_type == DSO_BINARY_TYPE__GUEST_KMODULE_COMP;
 
+
+       /*
+        * Read the build id if possible. This is required for
+        * DSO_BINARY_TYPE__BUILDID_DEBUGINFO to work
+        */
+       if (filename__read_build_id(dso->name, build_id, BUILD_ID_SIZE) > 0)
+               dso__set_build_id(dso, build_id);
+
        /*
         * Iterate over candidate debug images.
         * Keep track of "interesting" ones (those which have a symtab, dynsym,