[PATCH perf/core v4 03/19] perf buildid-cache: Fall back to the old style build-id cache

[Masami Hiramatsu]

Fall back to the old style build-id cache
(~/.debug/<path-to-bin>/<build-id>) if possible.
Because there is old build-id cache under ~/.debug, perf
has to check if the old entry is there instead of returning
an error. Or, user have to remove ~/.debug completely.

This patch introduces fallback code to try using old-style
buildid caches. To update the cached entry, you just need to
add a cache. It automatically removes old cache entry and
make a new one in new style
(~/.debug/<path-to-bin>/<build-id>/[elf|vdso|kallsyms]).

IOW, without this patch, "perf buildid-cache --add" always
gets errors when adding existing binaries.
  ----
  # perf buildid-cache -a /usr/lib64/libc-2.20.so,/usr/bin/gcc
  Couldn't add /usr/bin/gcc: Not a directory
  Couldn't add /usr/lib64/libc-2.20.so: Not a directory
  ----
Moreover, --update option removes only symlink, thus the
build-id cache is corrupted.

This fixes above issues.

Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
---
 tools/perf/util/build-id.c |   17 ++++++++++++++++-
 tools/perf/util/symbol.c   |   13 +++++++++----
 2 files changed, 25 insertions(+), 5 deletions(-)

diff --git a/tools/perf/util/build-id.c b/tools/perf/util/build-id.c
index 46a8bcc..b035483 100644
--- a/tools/perf/util/build-id.c
+++ b/tools/perf/util/build-id.c
@@ -155,6 +155,12 @@ static char *build_id_cache__linkname(const char *sbuild_id, char *bf,
 	return bf;
 }
 
+static bool __is_regular_file(const char *pathname)
+{
+	struct stat sb;
+	return stat(pathname, &sb) == 0 && S_ISREG(sb.st_mode);
+}
+
 static const char *build_id_cache__basename(bool is_kallsyms, bool is_vdso)
 {
 	return is_kallsyms ? "kallsyms" : (is_vdso ? "vdso" : "elf");
@@ -177,7 +183,11 @@ char *dso__build_id_filename(const struct dso *dso, char *bf, size_t size)
 	if (!linkname)
 		return NULL;
 
-	ret = asnprintf(&bf, size, "%s/%s", linkname,
+	/* Check if old style build_id cache */
+	if (__is_regular_file(linkname))
+		ret = asnprintf(&bf, size, "%s", linkname);
+	else
+		ret = asnprintf(&bf, size, "%s/%s", linkname,
 			 build_id_cache__basename(is_kallsyms, is_vdso));
 	if (ret < 0 || (!alloc && size < (unsigned int)ret))
 		bf = NULL;
@@ -445,6 +455,11 @@ int build_id_cache__add_s(const char *sbuild_id, const char *name,
 	if (!dir_name)
 		goto out_free;
 
+	/* Remove old style build-id cache */
+	if (__is_regular_file(dir_name))
+		if (unlink(dir_name))
+			goto out_free;
+
 	if (mkdir_p(dir_name, 0755))
 		goto out_free;
 
diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index c57cb47..9463c7d 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -1687,11 +1687,16 @@ static char *dso__find_kallsyms(struct dso *dso, struct map *map)
 
 	scnprintf(path, sizeof(path), "%s/[kernel.kallsyms]/%s/kallsyms",
 		  buildid_dir, sbuild_id);
-
+	/* Try old style kallsyms cache */
 	if (access(path, F_OK)) {
-		pr_err("No kallsyms or vmlinux with build-id %s was found\n",
-		       sbuild_id);
-		return NULL;
+		scnprintf(path, sizeof(path), "%s/[kernel.kallsyms]/%s",
+			  buildid_dir, sbuild_id);
+
+		if (access(path, F_OK)) {
+			pr_err("No kallsyms or vmlinux with build-id %s was found\n",
+			       sbuild_id);
+			return NULL;
+		}
 	}
 
 	return strdup(path);