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[PATCH 10/12] perf symbols: we can now read separate debug-info files based on a build ID

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From: Dima Kogan <dima@secretsauce.net>

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>
---
 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 e7bf0c46918d..71bf711a628c 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,
-- 
2.1.0

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[GIT PULL 00/12] perf/core improvements and fixes Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-10-28 16:40 +0100
  [PATCH 07/12] perf stat: Cache aggregated map entries in extra cpumap Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-10-28 16:40 +0100
  [PATCH 08/12] perf tools: Search for more options when passing args to -h Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-10-28 16:40 +0100
  [PATCH 04/12] perf tools: Introduce usage_with_options_msg() Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-10-28 16:40 +0100
  [PATCH 10/12] perf symbols: we can now read separate debug-info files based on a build ID Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-10-28 16:40 +0100
  [PATCH 02/12] perf report: Rename to --show-cpu-utilization Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-10-28 16:40 +0100
  [PATCH 11/12] perf tools: Enable pre-event inherit setting by config terms Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-10-28 16:40 +0100
  [PATCH 12/12] perf symbols: Fix endless loop in dso__split_kallsyms_for_kcore Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-10-28 16:40 +0100
  [PATCH 09/12] perf symbols: Fix type error when reading a build-id Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-10-28 16:40 +0100
  [PATCH 01/12] perf tools: Improve ambiguous option help message Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-10-28 16:40 +0100
  [PATCH 05/12] perf evsel: Move id_offset out of struct perf_evsel union member Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-10-28 16:40 +0100
  Re: [GIT PULL 00/12] perf/core improvements and fixes Ingo Molnar <mingo@kernel.org> - 2015-10-29 10:40 +0100
    Re: [GIT PULL 00/12] perf/core improvements and fixes Ingo Molnar <mingo@kernel.org> - 2015-10-29 11:00 +0100
    Re: [GIT PULL 00/12] perf/core improvements and fixes Jiri Olsa <jolsa@redhat.com> - 2015-10-29 11:00 +0100

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