[PATCH 2/2] perf: we can now read separate debug-info files based on a build ID

[Dima Kogan]

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@xxxxxxxxxxxxxxx>
---
 tools/perf/util/symbol.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index 1f97ffb..05c656b 100644
--- 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,
-- 
2.1.4


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