[PATCH v2 2/4] perf: disasm: use build_id_path if fallback failed

Changbin Du
2024-06-15T09:20:42Z

If we can not fallback for special dso (vmlinx and vdso), use the
build_id_path found previously.

To make change easy, this change first refactors the code by extracting
two functions read_buildid_linkname() and fallback_filename().

Signed-off-by: Changbin Du <changbin.du@huawei.com>
---
tools/perf/util/disasm.c | 121 ++++++++++++++++++++++++---------------
1 file changed, 75 insertions(+), 46 deletions(-)

diff --git a/tools/perf/util/disasm.c b/tools/perf/util/disasm.c
index 442e9802a772..3075daa61916 100644
--- a/tools/perf/util/disasm.c
+++ b/tools/perf/util/disasm.c
@@ -1092,14 +1092,72 @@ int symbol__strerror_disassemble(struct map_symbol *ms, int errnum, char *buf, s
return 0;
}

-static int dso__disassemble_filename(struct dso *dso, char *filename, size_t filename_size)
+static int read_buildid_linkname(char *filename, char *linkname, size_t linkname_size)
{
- char linkname[PATH_MAX];
- char *build_id_filename;
char *build_id_path = NULL;
char *pos;
int len;

+ build_id_path = strdup(filename);
+ if (!build_id_path)
+ return ENOMEM;
+
+ /*
+ * old style build-id cache has name of XX/XXXXXXX.. while
+ * new style has XX/XXXXXXX../{elf,kallsyms,vdso}.
+ * extract the build-id part of dirname in the new style only.
+ */
+ pos = strrchr(build_id_path, '/');
+ if (pos && strlen(pos) < SBUILD_ID_SIZE - 2)
+ dirname(build_id_path);
+
+ len = readlink(build_id_path, linkname, linkname_size);
+ if (len < 0) {
+ free(build_id_path);
+ return -1;
+ }
+
+ linkname[len] = '\0';
+ free(build_id_path);
+ return 0;
+}
+
+static int fallback_filename(struct dso *dso, char *filename, size_t filename_size)
+{
+ char filepath[PATH_MAX];
+
+ /*
+ * If we don't have build-ids or the build-id file isn't in the
+ * cache, or is just a kallsyms file, well, lets hope that this
+ * DSO is the same as when 'perf record' ran.
+ */
+ if ((dso__kernel(dso) || dso__is_vdso(dso)) && dso__long_name(dso)[0] == '/')
+ snprintf(filepath, sizeof(filepath), "%s", dso__long_name(dso));
+ else
+ __symbol__join_symfs(filepath, sizeof(filepath), dso__long_name(dso));
+
+ mutex_lock(dso__lock(dso));
+ if (access(filepath, R_OK) && errno == ENOENT && dso__nsinfo(dso)) {
+ char *new_name = dso__filename_with_chroot(dso, filepath);
+ if (new_name) {
+ strlcpy(filepath, new_name, sizeof(filepath));
+ free(new_name);
+ }
+ }
+ mutex_unlock(dso__lock(dso));
+
+ if (access(filepath, R_OK) && errno == ENOENT)
+ return ENOENT;
+
+ snprintf(filename, filename_size, "%s", filepath);
+ return 0;
+}
+
+static int dso__disassemble_filename(struct dso *dso, char *filename, size_t filename_size)
+{
+ char linkname[PATH_MAX];
+ char *build_id_filename;
+
if (dso__symtab_type(dso) == DSO_BINARY_TYPE__KALLSYMS &&
!dso__is_kcore(dso))
return SYMBOL_ANNOTATE_ERRNO__NO_VMLINUX;
@@ -1111,57 +1169,28 @@ static int dso__disassemble_filename(struct dso *dso, char *filename, size_t fil
} else {
if (dso__has_build_id(dso))
return ENOMEM;
- goto fallback;
+ return fallback_filename(dso, filename, filename_size);
}

- build_id_path = strdup(filename);
- if (!build_id_path)
- return ENOMEM;
-
- /*
- * old style build-id cache has name of XX/XXXXXXX.. while
- * new style has XX/XXXXXXX../{elf,kallsyms,vdso}.
- * extract the build-id part of dirname in the new style only.
- */
- pos = strrchr(build_id_path, '/');
- if (pos && strlen(pos) < SBUILD_ID_SIZE - 2)
- dirname(build_id_path);
+ if (access(filename, R_OK))
+ return fallback_filename(dso, filename, filename_size);

- if (dso__is_kcore(dso))
+ if (dso__is_kcore(dso) || dso__is_vdso(dso))
goto fallback;

- len = readlink(build_id_path, linkname, sizeof(linkname) - 1);
- if (len < 0)
- goto fallback;
+ if (!read_buildid_linkname(filename, linkname, sizeof(linkname) - 1) &&
+ (!strstr(linkname, DSO__NAME_KALLSYMS) && !strstr(linkname, DSO__NAME_VDSO))) {
+ /* not kallsysms or vdso, use build_id path found above */
+ goto out;
+ }

- linkname[len] = '\0';
- if (strstr(linkname, DSO__NAME_KALLSYMS) || strstr(linkname, DSO__NAME_VDSO) ||
- access(filename, R_OK)) {
fallback:
- /*
- * If we don't have build-ids or the build-id file isn't in the
- * cache, or is just a kallsyms file, well, lets hope that this
- * DSO is the same as when 'perf record' ran.
- */
- if ((dso__kernel(dso) || dso__is_vdso(dso)) && dso__long_name(dso)[0] == '/')
- snprintf(filename, filename_size, "%s", dso__long_name(dso));
- else
- __symbol__join_symfs(filename, filename_size, dso__long_name(dso));
-
- mutex_lock(dso__lock(dso));
- if (access(filename, R_OK) && errno == ENOENT && dso__nsinfo(dso)) {
- char *new_name = dso__filename_with_chroot(dso, filename);
- if (new_name) {
- strlcpy(filename, new_name, filename_size);
- free(new_name);
- }
- }
- mutex_unlock(dso__lock(dso));
- } else if (dso__binary_type(dso) == DSO_BINARY_TYPE__NOT_FOUND) {
- dso__set_binary_type(dso, DSO_BINARY_TYPE__BUILD_ID_CACHE);
+ if (fallback_filename(dso, filename, filename_size)) {
+ /* if fallback failed, use build_id path found above */
+out:
+ if (dso__binary_type(dso) == DSO_BINARY_TYPE__NOT_FOUND)
+ dso__set_binary_type(dso, DSO_BINARY_TYPE__BUILD_ID_CACHE);
}
-
- free(build_id_path);
return 0;
}

--
2.34.1