tools api fs: Dynamically allocate cgroupfs mount point cache, removing 4128 bytes from .bss

Move the cgroupfs_cache_entry 4128 byte array out of .bss.

Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: K Prateek Nayak <kprateek.nayak@amd.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Leo Yan <leo.yan@linaro.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Bangoria <ravi.bangoria@amd.com>
Cc: Ross Zwisler <zwisler@chromium.org>
Cc: Sean Christopherson <seanjc@google.com>
Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Tiezhu Yang <yangtiezhu@loongson.cn>
Cc: Yang Jihong <yangjihong1@huawei.com>
Link: https://lore.kernel.org/r/20230526183401.2326121-15-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/lib/api/fs/cgroup.c

@@ -14,7 +14,7 @@ struct cgroupfs_cache_entry {
 };
 
 /* just cache last used one */
-static struct cgroupfs_cache_entry cached;
+static struct cgroupfs_cache_entry *cached;
 
 int cgroupfs_find_mountpoint(char *buf, size_t maxlen, const char *subsys)
 {
@@ -24,9 +24,9 @@ int cgroupfs_find_mountpoint(char *buf, size_t maxlen, const char *subsys)
 	char *p, *path;
 	char mountpoint[PATH_MAX];
 
-	if (!strcmp(cached.subsys, subsys)) {
-		if (strlen(cached.mountpoint) < maxlen) {
-			strcpy(buf, cached.mountpoint);
+	if (cached && !strcmp(cached->subsys, subsys)) {
+		if (strlen(cached->mountpoint) < maxlen) {
+			strcpy(buf, cached->mountpoint);
 			return 0;
 		}
 		return -1;
@@ -91,8 +91,13 @@ int cgroupfs_find_mountpoint(char *buf, size_t maxlen, const char *subsys)
 	free(line);
 	fclose(fp);
 
-	strncpy(cached.subsys, subsys, sizeof(cached.subsys) - 1);
-	strcpy(cached.mountpoint, mountpoint);
+	if (!cached)
+		cached = calloc(1, sizeof(*cached));
+
+	if (cached) {
+		strncpy(cached->subsys, subsys, sizeof(cached->subsys) - 1);
+		strcpy(cached->mountpoint, mountpoint);
+	}
 
 	if (mountpoint[0] && strlen(mountpoint) < maxlen) {
 		strcpy(buf, mountpoint);