Em Wed, May 11, 2016 at 10:52:27PM +0900, Masami Hiramatsu escreveu:
> Cleanup the code flow of dso__find_kallsyms() to remove
> redundant checking code and add some comment for readability.
>
> Signed-off-by: Masami Hiramatsu <mhira...@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;
> +}
Do we really have to use this big hammer just for checking if a file is
readable? What is wronte with:
access(pathname, R_OK)
?
I see, you're keeping the existing logic, but since you've gone to the
trouble of introducing a seemingly generic function like
filename__readable(), you could as well use the canonical way to check
if a file is readable, namely access(R_OK), no?
Adrian, is there something magical about /proc/kcore for this test to be
done that way? If so, we better document not to waste our time next time
we look at this...
- Arnaldo
> +
> 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 */
How that improves the previous comment?
> 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,
