[PATCH v1 02/25] perf pmu: Avoid a path name copy

From: Ian Rogers
Date: Wed Aug 23 2023 - 04:12:36 EST


Rather than read a base path and append into a 2nd path, read the base
path directly into output buffer and append to that.

Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>
---
tools/perf/util/pmu.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
index a7f05e4dda97..7683c6749d66 100644
--- a/tools/perf/util/pmu.c
+++ b/tools/perf/util/pmu.c
@@ -1756,17 +1756,19 @@ int perf_pmu__event_source_devices_fd(void)
* then pathname will be filled with
* "/sys/bus/event_source/devices/cs_etm/format"
*
- * Return 0 if the sysfs mountpoint couldn't be found or if no
- * characters were written.
+ * Return 0 if the sysfs mountpoint couldn't be found, if no characters were
+ * written or if the buffer size is exceeded.
*/
int perf_pmu__pathname_scnprintf(char *buf, size_t size,
const char *pmu_name, const char *filename)
{
- char base_path[PATH_MAX];
+ size_t len;

- if (!perf_pmu__event_source_devices_scnprintf(base_path, sizeof(base_path)))
+ len = perf_pmu__event_source_devices_scnprintf(buf, size);
+ if (!len || (len + strlen(pmu_name) + strlen(filename) + 1) >= size)
return 0;
- return scnprintf(buf, size, "%s%s/%s", base_path, pmu_name, filename);
+
+ return scnprintf(buf + len, size - len, "%s/%s", pmu_name, filename);
}

int perf_pmu__pathname_fd(int dirfd, const char *pmu_name, const char *filename, int flags)
--
2.42.0.rc1.204.g551eb34607-goog