perf machine: Reuse module path buffer

Rather than copying the path and appending the directory entry in a
fresh path buffer, append to the path at the end of where it is for
the recursion level. This saves a PATH_MAX buffer per recursion level
and some unnecessary copying.

Signed-off-by: Ian Rogers <irogers@google.com>
Link: https://lore.kernel.org/r/20250222061015.303622-9-irogers@google.com
Signed-off-by: Namhyung Kim <namhyung@kernel.org>

diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index e394c630e3a2506ed2b3e993d6edde4e689a27be..3f1faf94198dbe56b944613b3ce05d93f4c98c53 100644 (file)
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -1338,22 +1338,23 @@ static int maps__set_module_path(struct maps *maps, const char *path, struct kmo
        return 0;
 }
 
-static int maps__set_modules_path_dir(struct maps *maps, const char *dir_name, int depth)
+static int maps__set_modules_path_dir(struct maps *maps, char *path, size_t path_size, int depth)
 {
        struct io_dirent64 *dent;
        struct io_dir iod;
+       size_t root_len = strlen(path);
        int ret = 0;
 
-       io_dir__init(&iod, open(dir_name, O_CLOEXEC | O_DIRECTORY | O_RDONLY));
+       io_dir__init(&iod, open(path, O_CLOEXEC | O_DIRECTORY | O_RDONLY));
        if (iod.dirfd < 0) {
-               pr_debug("%s: cannot open %s dir\n", __func__, dir_name);
+               pr_debug("%s: cannot open %s dir\n", __func__, path);
                return -1;
        }
-
+       /* Bounds check, should never happen. */
+       if (root_len >= path_size)
+               return -1;
+       path[root_len++] = '/';
        while ((dent = io_dir__readdir(&iod)) != NULL) {
-               char path[PATH_MAX];
-
-               path__join(path, sizeof(path), dir_name, dent->d_name);
                if (io_dir__is_dir(&iod, dent)) {
                        if (!strcmp(dent->d_name, ".") ||
                            !strcmp(dent->d_name, ".."))
@@ -1366,7 +1367,12 @@ static int maps__set_modules_path_dir(struct maps *maps, const char *dir_name, i
                                        continue;
                        }
 
-                       ret = maps__set_modules_path_dir(maps, path, depth + 1);
+                       /* Bounds check, should never happen. */
+                       if (root_len + strlen(dent->d_name) >= path_size)
+                               continue;
+
+                       strcpy(path + root_len, dent->d_name);
+                       ret = maps__set_modules_path_dir(maps, path, path_size, depth + 1);
                        if (ret < 0)
                                goto out;
                } else {
@@ -1376,9 +1382,14 @@ static int maps__set_modules_path_dir(struct maps *maps, const char *dir_name, i
                        if (ret)
                                goto out;
 
-                       if (m.kmod)
-                               ret = maps__set_module_path(maps, path, &m);
+                       if (m.kmod) {
+                               /* Bounds check, should never happen. */
+                               if (root_len + strlen(dent->d_name) < path_size) {
+                                       strcpy(path + root_len, dent->d_name);
+                                       ret = maps__set_module_path(maps, path, &m);
 
+                               }
+                       }
                        zfree(&m.name);
 
                        if (ret)
@@ -1404,7 +1415,8 @@ static int machine__set_modules_path(struct machine *machine)
                 machine->root_dir, version);
        free(version);
 
-       return maps__set_modules_path_dir(machine__kernel_maps(machine), modules_path, 0);
+       return maps__set_modules_path_dir(machine__kernel_maps(machine),
+                                         modules_path, sizeof(modules_path), 0);
 }
 int __weak arch__fix_module_text_start(u64 *start __maybe_unused,
                                u64 *size __maybe_unused,