perf events: Remove scandir in thread synthesis

This avoids scanddir reading the directory into memory that's
allocated and instead allocates on the stack.

Acked-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Ian Rogers <irogers@google.com>
Acked-by: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20250222061015.303622-6-irogers@google.com
Signed-off-by: Namhyung Kim <namhyung@kernel.org>

diff --git a/tools/perf/util/synthetic-events.c b/tools/perf/util/synthetic-events.c
index 2dfc4260d36dc6ce29692213686b7588c9dd3657..2fc4d05378402c14e0e64f60fa258d097d20ca16 100644 (file)
--- a/tools/perf/util/synthetic-events.c
+++ b/tools/perf/util/synthetic-events.c
@@ -38,6 +38,7 @@
 #include <uapi/linux/mman.h> /* To get things like MAP_HUGETLB even on older libc headers */
 #include <api/fs/fs.h>
 #include <api/io.h>
+#include <api/io_dir.h>
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <fcntl.h>
@@ -767,10 +768,10 @@ static int __event__synthesize_thread(union perf_event *comm_event,
                                      bool needs_mmap, bool mmap_data)
 {
        char filename[PATH_MAX];
-       struct dirent **dirent;
+       struct io_dir iod;
+       struct io_dirent64 *dent;
        pid_t tgid, ppid;
        int rc = 0;
-       int i, n;
 
        /* special case: only send one comm event using passed in pid */
        if (!full) {
@@ -802,16 +803,19 @@ static int __event__synthesize_thread(union perf_event *comm_event,
        snprintf(filename, sizeof(filename), "%s/proc/%d/task",
                 machine->root_dir, pid);
 
-       n = scandir(filename, &dirent, filter_task, NULL);
-       if (n < 0)
-               return n;
+       io_dir__init(&iod, open(filename, O_CLOEXEC | O_DIRECTORY | O_RDONLY));
+       if (iod.dirfd < 0)
+               return -1;
 
-       for (i = 0; i < n; i++) {
+       while ((dent = io_dir__readdir(&iod)) != NULL) {
                char *end;
                pid_t _pid;
                bool kernel_thread = false;
 
-               _pid = strtol(dirent[i]->d_name, &end, 10);
+               if (!isdigit(dent->d_name[0]))
+                       continue;
+
+               _pid = strtol(dent->d_name, &end, 10);
                if (*end)
                        continue;
 
@@ -845,9 +849,7 @@ static int __event__synthesize_thread(union perf_event *comm_event,
                }
        }
 
-       for (i = 0; i < n; i++)
-               zfree(&dirent[i]);
-       free(dirent);
+       close(iod.dirfd);
 
        return rc;
 }