[tip:perfcounters/urgent] perf symbol: Fix symbol parsing in certain cases: use the build-id as a symlink

tip-bot for Arnaldo Carvalho de Melo
2009-08-06T18:28:07Z

Commit-ID: 4d1e00a8af426500edfb8643fa6c375b89f1f804
Gitweb: http://git.kernel.org/tip/4d1e00a8af426500edfb8643fa6c375b89f1f804
Author: Arnaldo Carvalho de Melo <acme@redhat.com>
AuthorDate: Wed, 5 Aug 2009 19:02:49 -0300
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Thu, 6 Aug 2009 20:24:37 +0200

perf symbol: Fix symbol parsing in certain cases: use the build-id as a symlink

In some cases distros have binaries and debuginfo in weird places:

[root@doppio tuna]# ls -la /usr/lib64/{xulrunner-1.9.1/xulrunner-stub,firefox-3.5.2/firefox}
-rwxr-xr-x 1 root root 90024 2009-08-03 19:45 /usr/lib64/firefox-3.5.2/firefox
-rwxr-xr-x 1 root root 90024 2009-08-03 18:23 /usr/lib64/xulrunner-1.9.1/xulrunner-stub
[root@doppio tuna]# sha1sum /usr/lib64/{xulrunner-1.9.1/xulrunner-stub,firefox-3.5.2/firefox}
19a858077d263d5de22c9c5da250d3e4396ae739 /usr/lib64/xulrunner-1.9.1/xulrunner-stub
19a858077d263d5de22c9c5da250d3e4396ae739 /usr/lib64/firefox-3.5.2/firefox
[root@doppio tuna]# rpm -qf /usr/lib64/{xulrunner-1.9.1/xulrunner-stub,firefox-3.5.2/firefox}
xulrunner-1.9.1.2-1.fc11.x86_64
firefox-3.5.2-2.fc11.x86_64
[root@doppio tuna]# ls -la /usr/lib/debug/{usr/lib64/xulrunner-1.9.1/xulrunner-stub,usr/lib64/firefox-3.5.2/firefox}.debug
ls: cannot access /usr/lib/debug/usr/lib64/firefox-3.5.2/firefox.debug: No such file or directory
-rwxr-xr-x 1 root root 403608 2009-08-03 18:22 /usr/lib/debug/usr/lib64/xulrunner-1.9.1/xulrunner-stub.debug

Seemingly we don't have a .symtab when we actually can find it
if we use the .note.gnu.build-id ELF section put in place by
some distros. Use it and find the symbols we need.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

---
tools/perf/util/symbol.c | 76 ++++++++++++++++++++++++++++++++++++++++++++--
1 files changed, 73 insertions(+), 3 deletions(-)

diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index 0580b94..16ddca2 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -661,10 +661,69 @@ out_close:
return err;
}

+#define BUILD_ID_SIZE 128
+
+static char *dso__read_build_id(struct dso *self, int verbose)
+{
+ int i;
+ GElf_Ehdr ehdr;
+ GElf_Shdr shdr;
+ Elf_Data *build_id_data;
+ Elf_Scn *sec;
+ char *build_id = NULL, *bid;
+ unsigned char *raw;
+ Elf *elf;
+ int fd = open(self->name, O_RDONLY);
+
+ if (fd < 0)
+ goto out;
+
+ elf = elf_begin(fd, ELF_C_READ_MMAP, NULL);
+ if (elf == NULL) {
+ if (verbose)
+ fprintf(stderr, "%s: cannot read %s ELF file.\n",
+ __func__, self->name);
+ goto out_close;
+ }
+
+ if (gelf_getehdr(elf, &ehdr) == NULL) {
+ if (verbose)
+ fprintf(stderr, "%s: cannot get elf header.\n", __func__);
+ goto out_elf_end;
+ }
+
+ sec = elf_section_by_name(elf, &ehdr, &shdr, ".note.gnu.build-id", NULL);
+ if (sec == NULL)
+ goto out_elf_end;
+
+ build_id_data = elf_getdata(sec, NULL);
+ if (build_id_data == NULL)
+ goto out_elf_end;
+ build_id = malloc(BUILD_ID_SIZE);
+ if (build_id == NULL)
+ goto out_elf_end;
+ raw = build_id_data->d_buf + 16;
+ bid = build_id;
+
+ for (i = 0; i < 20; ++i) {
+ sprintf(bid, "%02x", *raw);
+ ++raw;
+ bid += 2;
+ }
+ if (verbose)
+ printf("%s(%s): %s\n", __func__, self->name, build_id);
+out_elf_end:
+ elf_end(elf);
+out_close:
+ close(fd);
+out:
+ return build_id;
+}
+
int dso__load(struct dso *self, symbol_filter_t filter, int verbose)
{
- int size = strlen(self->name) + sizeof("/usr/lib/debug%s.debug");
- char *name = malloc(size);
+ int size = PATH_MAX;
+ char *name = malloc(size), *build_id = NULL;
int variant = 0;
int ret = -1;
int fd;
@@ -686,7 +745,18 @@ more:
case 1: /* Ubuntu */
snprintf(name, size, "/usr/lib/debug%s", self->name);
break;
- case 2: /* Sane people */
+ case 2:
+ build_id = dso__read_build_id(self, verbose);
+ if (build_id != NULL) {
+ snprintf(name, size,
+ "/usr/lib/debug/.build-id/%.2s/%s.debug",
+ build_id, build_id + 2);
+ free(build_id);
+ break;
+ }
+ variant++;
+ /* Fall thru */
+ case 3: /* Sane people */
snprintf(name, size, "%s", self->name);
break;