[PATCH 38/86] perf buildid-cache: Cache debuginfo

Arnaldo Carvalho de Melo
2017-07-19T14:33:55Z

From: Krister Johansen <kjlx@templeofstupid.com>

If a stripped binary is placed in the cache, the user is in a situation
where there's a cached elf file present, but it doesn't have any symtab
to use for name resolution. Grab the debuginfo for binaries that don't
end in .ko. This yields a better chance of resolving symbols from older
traces.

Signed-off-by: Krister Johansen <kjlx@templeofstupid.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas-Mich Richter <tmricht@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/1499305693-1599-7-git-send-email-kjlx@templeofstupid.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/builtin-buildid-cache.c | 2 +-
tools/perf/util/annotate.c | 2 +-
tools/perf/util/build-id.c | 72 +++++++++++++++++++++++++++++++++++---
tools/perf/util/build-id.h | 3 +-
tools/perf/util/dso.c | 8 ++++-
tools/perf/util/dso.h | 1 +
tools/perf/util/machine.c | 3 +-
tools/perf/util/symbol.c | 12 +++++--
8 files changed, 90 insertions(+), 13 deletions(-)

diff --git a/tools/perf/builtin-buildid-cache.c b/tools/perf/builtin-buildid-cache.c
index d65bd86bee99..e3eb6240ced0 100644
--- a/tools/perf/builtin-buildid-cache.c
+++ b/tools/perf/builtin-buildid-cache.c
@@ -243,7 +243,7 @@ static bool dso__missing_buildid_cache(struct dso *dso, int parm __maybe_unused)
char filename[PATH_MAX];
u8 build_id[BUILD_ID_SIZE];

- if (dso__build_id_filename(dso, filename, sizeof(filename)) &&
+ if (dso__build_id_filename(dso, filename, sizeof(filename), false) &&
filename__read_build_id(filename, build_id,
sizeof(build_id)) != sizeof(build_id)) {
if (errno == ENOENT)
diff --git a/tools/perf/util/annotate.c b/tools/perf/util/annotate.c
index ef434b53d849..1742510f0120 100644
--- a/tools/perf/util/annotate.c
+++ b/tools/perf/util/annotate.c
@@ -1347,7 +1347,7 @@ static int dso__disassemble_filename(struct dso *dso, char *filename, size_t fil
!dso__is_kcore(dso))
return SYMBOL_ANNOTATE_ERRNO__NO_VMLINUX;

- build_id_filename = dso__build_id_filename(dso, NULL, 0);
+ build_id_filename = dso__build_id_filename(dso, NULL, 0, false);
if (build_id_filename) {
__symbol__join_symfs(filename, filename_size, build_id_filename);
free(build_id_filename);
diff --git a/tools/perf/util/build-id.c b/tools/perf/util/build-id.c
index f7bfd90a7388..e9665150e9b1 100644
--- a/tools/perf/util/build-id.c
+++ b/tools/perf/util/build-id.c
@@ -243,12 +243,15 @@ static bool build_id_cache__valid_id(char *sbuild_id)
return result;
}

-static const char *build_id_cache__basename(bool is_kallsyms, bool is_vdso)
+static const char *build_id_cache__basename(bool is_kallsyms, bool is_vdso,
+ bool is_debug)
{
- return is_kallsyms ? "kallsyms" : (is_vdso ? "vdso" : "elf");
+ return is_kallsyms ? "kallsyms" : (is_vdso ? "vdso" : (is_debug ?
+ "debug" : "elf"));
}

-char *dso__build_id_filename(const struct dso *dso, char *bf, size_t size)
+char *dso__build_id_filename(const struct dso *dso, char *bf, size_t size,
+ bool is_debug)
{
bool is_kallsyms = dso__is_kallsyms((struct dso *)dso);
bool is_vdso = dso__is_vdso((struct dso *)dso);
@@ -270,7 +273,8 @@ char *dso__build_id_filename(const struct dso *dso, char *bf, size_t size)
ret = asnprintf(&bf, size, "%s", linkname);
else
ret = asnprintf(&bf, size, "%s/%s", linkname,
- build_id_cache__basename(is_kallsyms, is_vdso));
+ build_id_cache__basename(is_kallsyms, is_vdso,
+ is_debug));
if (ret < 0 || (!alloc && size < (unsigned int)ret))
bf = NULL;
free(linkname);
@@ -603,12 +607,40 @@ static int build_id_cache__add_sdt_cache(const char *sbuild_id,
#define build_id_cache__add_sdt_cache(sbuild_id, realname, nsi) (0)
#endif

+static char *build_id_cache__find_debug(const char *sbuild_id,
+ struct nsinfo *nsi)
+{
+ char *realname = NULL;
+ char *debugfile;
+ struct nscookie nsc;
+ size_t len = 0;
+
+ debugfile = calloc(1, PATH_MAX);
+ if (!debugfile)
+ goto out;
+
+ len = __symbol__join_symfs(debugfile, PATH_MAX,
+ "/usr/lib/debug/.build-id/");
+ snprintf(debugfile + len, PATH_MAX - len, "%.2s/%s.debug", sbuild_id,
+ sbuild_id + 2);
+
+ nsinfo__mountns_enter(nsi, &nsc);
+ realname = realpath(debugfile, NULL);
+ if (realname && access(realname, R_OK))
+ zfree(&realname);
+ nsinfo__mountns_exit(&nsc);
+out:
+ free(debugfile);
+ return realname;
+}
+
int build_id_cache__add_s(const char *sbuild_id, const char *name,
struct nsinfo *nsi, bool is_kallsyms, bool is_vdso)
{
const size_t size = PATH_MAX;
char *realname = NULL, *filename = NULL, *dir_name = NULL,
*linkname = zalloc(size), *tmp;
+ char *debugfile = NULL;
int err = -1;

if (!is_kallsyms) {
@@ -635,7 +667,8 @@ int build_id_cache__add_s(const char *sbuild_id, const char *name,

/* Save the allocated buildid dirname */
if (asprintf(&filename, "%s/%s", dir_name,
- build_id_cache__basename(is_kallsyms, is_vdso)) < 0) {
+ build_id_cache__basename(is_kallsyms, is_vdso,
+ false)) < 0) {
filename = NULL;
goto out_free;
}
@@ -652,6 +685,34 @@ int build_id_cache__add_s(const char *sbuild_id, const char *name,
goto out_free;
}

+ /* Some binaries are stripped, but have .debug files with their symbol
+ * table. Check to see if we can locate one of those, since the elf
+ * file itself may not be very useful to users of our tools without a
+ * symtab.
+ */
+ if (!is_kallsyms && !is_vdso &&
+ strncmp(".ko", name + strlen(name) - 3, 3)) {
+ debugfile = build_id_cache__find_debug(sbuild_id, nsi);
+ if (debugfile) {
+ zfree(&filename);
+ if (asprintf(&filename, "%s/%s", dir_name,
+ build_id_cache__basename(false, false, true)) < 0) {
+ filename = NULL;
+ goto out_free;
+ }
+ if (access(filename, F_OK)) {
+ if (nsi && nsi->need_setns) {
+ if (copyfile_ns(debugfile, filename,
+ nsi))
+ goto out_free;
+ } else if (link(debugfile, filename) &&
+ errno != EEXIST &&
+ copyfile(debugfile, filename))
+ goto out_free;
+ }
+ }
+ }
+
if (!build_id_cache__linkname(sbuild_id, linkname, size))
goto out_free;
tmp = strrchr(linkname, '/');
@@ -676,6 +737,7 @@ int build_id_cache__add_s(const char *sbuild_id, const char *name,
if (!is_kallsyms)
free(realname);
free(filename);
+ free(debugfile);
free(dir_name);
free(linkname);
return err;
diff --git a/tools/perf/util/build-id.h b/tools/perf/util/build-id.h
index 23970847d4c4..113dc0615c57 100644
--- a/tools/perf/util/build-id.h
+++ b/tools/perf/util/build-id.h
@@ -17,7 +17,8 @@ int filename__sprintf_build_id(const char *pathname, char *sbuild_id);
char *build_id_cache__kallsyms_path(const char *sbuild_id, char *bf,
size_t size);

-char *dso__build_id_filename(const struct dso *dso, char *bf, size_t size);
+char *dso__build_id_filename(const struct dso *dso, char *bf, size_t size,
+ bool is_debug);

int build_id__mark_dso_hit(struct perf_tool *tool, union perf_event *event,
struct perf_sample *sample, struct perf_evsel *evsel,
diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c
index dc9b49533a8f..b9e087fb8247 100644
--- a/tools/perf/util/dso.c
+++ b/tools/perf/util/dso.c
@@ -32,6 +32,7 @@ char dso__symtab_origin(const struct dso *dso)
[DSO_BINARY_TYPE__JAVA_JIT] = 'j',
[DSO_BINARY_TYPE__DEBUGLINK] = 'l',
[DSO_BINARY_TYPE__BUILD_ID_CACHE] = 'B',
+ [DSO_BINARY_TYPE__BUILD_ID_CACHE_DEBUGINFO] = 'D',
[DSO_BINARY_TYPE__FEDORA_DEBUGINFO] = 'f',
[DSO_BINARY_TYPE__UBUNTU_DEBUGINFO] = 'u',
[DSO_BINARY_TYPE__OPENEMBEDDED_DEBUGINFO] = 'o',
@@ -97,7 +98,12 @@ int dso__read_binary_type_filename(const struct dso *dso,
break;
}
case DSO_BINARY_TYPE__BUILD_ID_CACHE:
- if (dso__build_id_filename(dso, filename, size) == NULL)
+ if (dso__build_id_filename(dso, filename, size, false) == NULL)
+ ret = -1;
+ break;
+
+ case DSO_BINARY_TYPE__BUILD_ID_CACHE_DEBUGINFO:
+ if (dso__build_id_filename(dso, filename, size, true) == NULL)
ret = -1;
break;

diff --git a/tools/perf/util/dso.h b/tools/perf/util/dso.h
index 78ec637fc68b..f886141678eb 100644
--- a/tools/perf/util/dso.h
+++ b/tools/perf/util/dso.h
@@ -21,6 +21,7 @@ enum dso_binary_type {
DSO_BINARY_TYPE__JAVA_JIT,
DSO_BINARY_TYPE__DEBUGLINK,
DSO_BINARY_TYPE__BUILD_ID_CACHE,
+ DSO_BINARY_TYPE__BUILD_ID_CACHE_DEBUGINFO,
DSO_BINARY_TYPE__FEDORA_DEBUGINFO,
DSO_BINARY_TYPE__UBUNTU_DEBUGINFO,
DSO_BINARY_TYPE__BUILDID_DEBUGINFO,
diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index 246b441110a1..a54a2be5eda4 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -705,7 +705,8 @@ size_t machine__fprintf_vmlinux_path(struct machine *machine, FILE *fp)

if (kdso->has_build_id) {
char filename[PATH_MAX];
- if (dso__build_id_filename(kdso, filename, sizeof(filename)))
+ if (dso__build_id_filename(kdso, filename, sizeof(filename),
+ false))
printed += fprintf(fp, "[0] %s\n", filename);
}

diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index 8c7bae545617..971b990557b4 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -53,6 +53,7 @@ static enum dso_binary_type binary_type_symtab[] = {
DSO_BINARY_TYPE__JAVA_JIT,
DSO_BINARY_TYPE__DEBUGLINK,
DSO_BINARY_TYPE__BUILD_ID_CACHE,
+ DSO_BINARY_TYPE__BUILD_ID_CACHE_DEBUGINFO,
DSO_BINARY_TYPE__FEDORA_DEBUGINFO,
DSO_BINARY_TYPE__UBUNTU_DEBUGINFO,
DSO_BINARY_TYPE__BUILDID_DEBUGINFO,
@@ -1418,6 +1419,7 @@ static bool dso__is_compatible_symtab_type(struct dso *dso, bool kmod,
return kmod && dso->symtab_type == type;

case DSO_BINARY_TYPE__BUILD_ID_CACHE:
+ case DSO_BINARY_TYPE__BUILD_ID_CACHE_DEBUGINFO:
return true;

case DSO_BINARY_TYPE__NOT_FOUND:
@@ -1565,10 +1567,14 @@ int dso__load(struct dso *dso, struct map *map)
struct symsrc *ss = &ss_[ss_pos];
bool next_slot = false;
bool is_reg;
+ bool nsexit;
int sirc;

enum dso_binary_type symtab_type = binary_type_symtab[i];

+ nsexit = (symtab_type == DSO_BINARY_TYPE__BUILD_ID_CACHE ||
+ symtab_type == DSO_BINARY_TYPE__BUILD_ID_CACHE_DEBUGINFO);
+
if (!dso__is_compatible_symtab_type(dso, kmod, symtab_type))
continue;

@@ -1576,13 +1582,13 @@ int dso__load(struct dso *dso, struct map *map)
root_dir, name, PATH_MAX))
continue;

- if (symtab_type == DSO_BINARY_TYPE__BUILD_ID_CACHE)
+ if (nsexit)
nsinfo__mountns_exit(&nsc);

is_reg = is_regular_file(name);
sirc = symsrc__init(ss, dso, name, symtab_type);

- if (symtab_type == DSO_BINARY_TYPE__BUILD_ID_CACHE)
+ if (nsexit)
nsinfo__mountns_enter(dso->nsinfo, &nsc);

if (!is_reg || sirc < 0) {
@@ -1724,7 +1730,7 @@ int dso__load_vmlinux_path(struct dso *dso, struct map *map)
}

if (!symbol_conf.ignore_vmlinux_buildid)
- filename = dso__build_id_filename(dso, NULL, 0);
+ filename = dso__build_id_filename(dso, NULL, 0, false);
if (filename != NULL) {
err = dso__load_vmlinux(dso, map, filename, true);
if (err > 0)
--
2.9.4