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Subject[PATCH v2] perf symbols: Follow .gnu_debuglink section to find separate symbols
The .gnu_debuglink section is specified to contain the filename of the
debug info file, as well as a CRC that can be used to validate it.

This doesn't currently use the checksum and relies on the usual build-id
matching for validation.

This provides more context:
http://sourceware.org/gdb/onlinedocs/gdb/Separate-Debug-Files.html

Signed-off-by: Pierre-Loup A. Griffais <pgriffais@nvidia.com>
Reported-by: Mike Sartain <mikesart@valvesoftware.com>
Tested-by: Mike Sartain <mikesart@valvesoftware.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
---
tools/perf/util/symbol.c | 65 +++++++++++++++++++++++++++++++++++++++++++++-
tools/perf/util/symbol.h | 1 +
2 files changed, 65 insertions(+), 1 deletion(-)
diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index 3e2e5ea..994f4ff 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -1590,11 +1590,62 @@ out:
return err;
}

+static int filename__read_debuglink(const char *filename,
+ char *debuglink, size_t size)
+{
+ int fd, err = -1;
+ Elf *elf;
+ GElf_Ehdr ehdr;
+ GElf_Shdr shdr;
+ Elf_Data *data;
+ Elf_Scn *sec;
+ Elf_Kind ek;
+
+ fd = open(filename, O_RDONLY);
+ if (fd < 0)
+ goto out;
+
+ elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
+ if (elf == NULL) {
+ pr_debug2("%s: cannot read %s ELF file.\n", __func__, filename);
+ goto out_close;
+ }
+
+ ek = elf_kind(elf);
+ if (ek != ELF_K_ELF)
+ goto out_close;
+
+ if (gelf_getehdr(elf, &ehdr) == NULL) {
+ pr_err("%s: cannot get elf header.\n", __func__);
+ goto out_close;
+ }
+
+ sec = elf_section_by_name(elf, &ehdr, &shdr,
+ ".gnu_debuglink", NULL);
+ if (sec == NULL)
+ goto out_close;
+
+ data = elf_getdata(sec, NULL);
+ if (data == NULL)
+ goto out_close;
+
+ /* the start of this section is a zero-terminated string */
+ strncpy(debuglink, data->d_buf, size);
+
+ elf_end(elf);
+
+out_close:
+ close(fd);
+out:
+ return err;
+}
+
char dso__symtab_origin(const struct dso *dso)
{
static const char origin[] = {
[SYMTAB__KALLSYMS] = 'k',
[SYMTAB__JAVA_JIT] = 'j',
+ [SYMTAB__DEBUGLINK] = 'l',
[SYMTAB__BUILD_ID_CACHE] = 'B',
[SYMTAB__FEDORA_DEBUGINFO] = 'f',
[SYMTAB__UBUNTU_DEBUGINFO] = 'u',
@@ -1662,10 +1713,22 @@ int dso__load(struct dso *dso, struct map *map, symbol_filter_t filter)
*/
want_symtab = 1;
restart:
- for (dso->symtab_type = SYMTAB__BUILD_ID_CACHE;
+ for (dso->symtab_type = SYMTAB__DEBUGLINK;
dso->symtab_type != SYMTAB__NOT_FOUND;
dso->symtab_type++) {
switch (dso->symtab_type) {
+ case SYMTAB__DEBUGLINK: {
+ char *debuglink;
+ strncpy(name, dso->long_name, size);
+ debuglink = name + dso->long_name_len;
+ while (debuglink != name && *debuglink != '/')
+ debuglink--;
+ if (*debuglink == '/')
+ debuglink++;
+ filename__read_debuglink(dso->long_name, debuglink,
+ size - (debuglink - name));
+ }
+ break;
case SYMTAB__BUILD_ID_CACHE:
/* skip the locally configured cache if a symfs is given */
if (symbol_conf.symfs[0] ||
diff --git a/tools/perf/util/symbol.h b/tools/perf/util/symbol.h
index af0752b..a884b99 100644
--- a/tools/perf/util/symbol.h
+++ b/tools/perf/util/symbol.h
@@ -257,6 +257,7 @@ enum symtab_type {
SYMTAB__KALLSYMS = 0,
SYMTAB__GUEST_KALLSYMS,
SYMTAB__JAVA_JIT,
+ SYMTAB__DEBUGLINK,
SYMTAB__BUILD_ID_CACHE,
SYMTAB__FEDORA_DEBUGINFO,
SYMTAB__UBUNTU_DEBUGINFO,
--
1.7.9.5

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