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-rw-r--r--tools/lib/api/fs/cgroup.c102
1 files changed, 102 insertions, 0 deletions
diff --git a/tools/lib/api/fs/cgroup.c b/tools/lib/api/fs/cgroup.c
new file mode 100644
index 000000000..1573dae42
--- /dev/null
+++ b/tools/lib/api/fs/cgroup.c
@@ -0,0 +1,102 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/stringify.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include "fs.h"
+
+struct cgroupfs_cache_entry {
+ char subsys[32];
+ char mountpoint[PATH_MAX];
+};
+
+/* just cache last used one */
+static struct cgroupfs_cache_entry cached;
+
+int cgroupfs_find_mountpoint(char *buf, size_t maxlen, const char *subsys)
+{
+ FILE *fp;
+ char *line = NULL;
+ size_t len = 0;
+ char *p, *path;
+ char mountpoint[PATH_MAX];
+
+ if (!strcmp(cached.subsys, subsys)) {
+ if (strlen(cached.mountpoint) < maxlen) {
+ strcpy(buf, cached.mountpoint);
+ return 0;
+ }
+ return -1;
+ }
+
+ fp = fopen("/proc/mounts", "r");
+ if (!fp)
+ return -1;
+
+ /*
+ * in order to handle split hierarchy, we need to scan /proc/mounts
+ * and inspect every cgroupfs mount point to find one that has
+ * the given subsystem. If we found v1, just use it. If not we can
+ * use v2 path as a fallback.
+ */
+ mountpoint[0] = '\0';
+
+ /*
+ * The /proc/mounts has the follow format:
+ *
+ * <devname> <mount point> <fs type> <options> ...
+ *
+ */
+ while (getline(&line, &len, fp) != -1) {
+ /* skip devname */
+ p = strchr(line, ' ');
+ if (p == NULL)
+ continue;
+
+ /* save the mount point */
+ path = ++p;
+ p = strchr(p, ' ');
+ if (p == NULL)
+ continue;
+
+ *p++ = '\0';
+
+ /* check filesystem type */
+ if (strncmp(p, "cgroup", 6))
+ continue;
+
+ if (p[6] == '2') {
+ /* save cgroup v2 path */
+ strcpy(mountpoint, path);
+ continue;
+ }
+
+ /* now we have cgroup v1, check the options for subsystem */
+ p += 7;
+
+ p = strstr(p, subsys);
+ if (p == NULL)
+ continue;
+
+ /* sanity check: it should be separated by a space or a comma */
+ if (!strchr(" ,", p[-1]) || !strchr(" ,", p[strlen(subsys)]))
+ continue;
+
+ strcpy(mountpoint, path);
+ break;
+ }
+ free(line);
+ fclose(fp);
+
+ strncpy(cached.subsys, subsys, sizeof(cached.subsys) - 1);
+ strcpy(cached.mountpoint, mountpoint);
+
+ if (mountpoint[0] && strlen(mountpoint) < maxlen) {
+ strcpy(buf, mountpoint);
+ return 0;
+ }
+ return -1;
+}