[PATCH v5 2/8] perf list: Add scandirat compatibility function

Ian Rogers
2024-02-16T23:55:17Z

scandirat is used during the printing of tracepoint events but may be
missing from certain libcs. Add a compatibility implementation that
uses the symlink of an fd in /proc as a path for the reliably present
scandir.

Signed-off-by: Ian Rogers <irogers@google.com>
---
tools/perf/util/print-events.c | 12 +++---------
tools/perf/util/util.c | 19 +++++++++++++++++++
tools/perf/util/util.h | 8 ++++++++
3 files changed, 30 insertions(+), 9 deletions(-)

diff --git a/tools/perf/util/print-events.c b/tools/perf/util/print-events.c
index 9e47712507cc..bf79dd366e2e 100644
--- a/tools/perf/util/print-events.c
+++ b/tools/perf/util/print-events.c
@@ -63,6 +63,8 @@ void print_tracepoint_events(const struct print_callbacks *print_cb __maybe_unus
{
char *events_path = get_tracing_file("events");
int events_fd = open(events_path, O_PATH);
+ struct dirent **sys_namelist = NULL;
+ int sys_items;

put_tracing_file(events_path);
if (events_fd < 0) {
@@ -70,10 +72,7 @@ void print_tracepoint_events(const struct print_callbacks *print_cb __maybe_unus
return;
}

-#ifdef HAVE_SCANDIRAT_SUPPORT
-{
- struct dirent **sys_namelist = NULL;
- int sys_items = tracing_events__scandir_alphasort(&sys_namelist);
+ sys_items = tracing_events__scandir_alphasort(&sys_namelist);

for (int i = 0; i < sys_items; i++) {
struct dirent *sys_dirent = sys_namelist[i];
@@ -130,11 +129,6 @@ void print_tracepoint_events(const struct print_callbacks *print_cb __maybe_unus
}

free(sys_namelist);
-}
-#else
- printf("\nWARNING: Your libc doesn't have the scandirat function, please ask its maintainers to implement it.\n"
- " As a rough fallback, please do 'ls %s' to see the available tracepoint events.\n", events_path);
-#endif
close(events_fd);
}

diff --git a/tools/perf/util/util.c b/tools/perf/util/util.c
index c1fd9ba6d697..4f561e5e4162 100644
--- a/tools/perf/util/util.c
+++ b/tools/perf/util/util.c
@@ -552,3 +552,22 @@ int sched_getcpu(void)
return -1;
}
#endif
+
+#ifndef HAVE_SCANDIRAT_SUPPORT
+int scandirat(int dirfd, const char *dirp,
+ struct dirent ***namelist,
+ int (*filter)(const struct dirent *),
+ int (*compar)(const struct dirent **, const struct dirent **))
+{
+ char path[PATH_MAX];
+ int err, fd = openat(dirfd, dirp, O_PATH);
+
+ if (fd < 0)
+ return fd;
+
+ snprintf(path, sizeof(path), "/proc/%d/fd/%d", getpid(), fd);
+ err = scandir(path, namelist, filter, compar);
+ close(fd);
+ return err;
+}
+#endif
diff --git a/tools/perf/util/util.h b/tools/perf/util/util.h
index 7c8915d92dca..9966c21aaf04 100644
--- a/tools/perf/util/util.h
+++ b/tools/perf/util/util.h
@@ -6,6 +6,7 @@
/* glibc 2.20 deprecates _BSD_SOURCE in favour of _DEFAULT_SOURCE */
#define _DEFAULT_SOURCE 1

+#include <dirent.h>
#include <fcntl.h>
#include <stdbool.h>
#include <stddef.h>
@@ -56,6 +57,13 @@ int perf_tip(char **strp, const char *dirpath);
int sched_getcpu(void);
#endif

+#ifndef HAVE_SCANDIRAT_SUPPORT
+int scandirat(int dirfd, const char *dirp,
+ struct dirent ***namelist,
+ int (*filter)(const struct dirent *),
+ int (*compar)(const struct dirent **, const struct dirent **));
+#endif
+
extern bool perf_singlethreaded;

void perf_set_singlethreaded(void);
--
2.44.0.rc0.258.g7320e95886-goog