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Subject[PATCH perf/core v7 07/21] perf symbol: Cleanup the code flow of dso__find_kallsyms
Date
Cleanup the code flow of dso__find_kallsyms() to remove
redundant checking code and add some comment for readability.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
tools/perf/util/symbol.c | 60 +++++++++++++++++++++-------------------------
1 file changed, 27 insertions(+), 33 deletions(-)

diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index e112bbd..b2b06b7 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -1629,6 +1629,15 @@ static int find_matching_kcore(struct map *map, char *dir, size_t dir_sz)
return ret;
}

+static bool filename__readable(const char *file)
+{
+ int fd = open(file, O_RDONLY);
+ if (fd < 0)
+ return false;
+ close(fd);
+ return true;
+}
+
static char *dso__find_kallsyms(struct dso *dso, struct map *map)
{
u8 host_build_id[BUILD_ID_SIZE];
@@ -1648,45 +1657,33 @@ static char *dso__find_kallsyms(struct dso *dso, struct map *map)
sizeof(host_build_id)) == 0)
is_host = dso__build_id_equal(dso, host_build_id);

- build_id__sprintf(dso->build_id, sizeof(dso->build_id), sbuild_id);
-
- scnprintf(path, sizeof(path), "%s/%s/%s", buildid_dir,
- DSO__NAME_KCORE, sbuild_id);
-
- /* Use /proc/kallsyms if possible */
+ /* Try a fast path for /proc/kallsyms if possible */
if (is_host) {
- DIR *d;
- int fd;
-
- /* If no cached kcore go with /proc/kallsyms */
- d = opendir(path);
- if (!d)
- goto proc_kallsyms;
- closedir(d);
-
/*
- * Do not check the build-id cache, until we know we cannot use
- * /proc/kcore.
+ * Do not check the build-id cache, unless we know we cannot use
+ * /proc/kcore or module maps don't match to /proc/kallsyms.
*/
- fd = open("/proc/kcore", O_RDONLY);
- if (fd != -1) {
- close(fd);
- /* If module maps match go with /proc/kallsyms */
- if (!validate_kcore_addresses("/proc/kallsyms", map))
- goto proc_kallsyms;
- }
-
- /* Find kallsyms in build-id cache with kcore */
- if (!find_matching_kcore(map, path, sizeof(path)))
- return strdup(path);
-
- goto proc_kallsyms;
+ if (filename__readable("/proc/kcore") &&
+ !validate_kcore_addresses("/proc/kallsyms", map))
+ goto proc_kallsyms;
}

+ build_id__sprintf(dso->build_id, sizeof(dso->build_id), sbuild_id);
+
/* Find kallsyms in build-id cache with kcore */
+ scnprintf(path, sizeof(path), "%s/%s/%s",
+ buildid_dir, DSO__NAME_KCORE, sbuild_id);
+
if (!find_matching_kcore(map, path, sizeof(path)))
return strdup(path);

+ /* Use current /proc/kallsyms if possible */
+ if (is_host) {
+proc_kallsyms:
+ return strdup("/proc/kallsyms");
+ }
+
+ /* Finally, find a cache of kallsyms */
scnprintf(path, sizeof(path), "%s/%s/%s",
buildid_dir, DSO__NAME_KALLSYMS, sbuild_id);

@@ -1697,9 +1694,6 @@ static char *dso__find_kallsyms(struct dso *dso, struct map *map)
}

return strdup(path);
-
-proc_kallsyms:
- return strdup("/proc/kallsyms");
}

static int dso__load_kernel_sym(struct dso *dso, struct map *map,
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