[PATCH 2/4] perf lock contention: Check --max-stack option

[Namhyung Kim]

The --max-stack option is used to allocate the BPF stack map and stack
trace array in the userspace.  Check the value properly before using.
Practically it cannot be greater than the sysctl_perf_event_max_stack.

Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx>
---
 tools/perf/builtin-lock.c | 30 +++++++++++++++++++++++++++---
 1 file changed, 27 insertions(+), 3 deletions(-)

diff --git a/tools/perf/builtin-lock.c b/tools/perf/builtin-lock.c
index 9722d4ab2e55..f67db60f1de6 100644
--- a/tools/perf/builtin-lock.c
+++ b/tools/perf/builtin-lock.c
@@ -24,6 +24,7 @@
 #include "util/data.h"
 #include "util/string2.h"
 #include "util/map.h"
+#include "util/util.h"
 
 #include <sys/types.h>
 #include <sys/prctl.h>
@@ -1858,6 +1859,29 @@ static int parse_map_entry(const struct option *opt, const char *str,
 	return 0;
 }
 
+static int parse_max_stack(const struct option *opt, const char *str,
+			   int unset __maybe_unused)
+{
+	unsigned long *len = (unsigned long *)opt->value;
+	long val;
+	char *endptr;
+
+	errno = 0;
+	val = strtol(str, &endptr, 0);
+	if (*endptr != '\0' || errno != 0) {
+		pr_err("invalid max stack depth: %s\n", str);
+		return -1;
+	}
+
+	if (val < 0 || val > sysctl__max_stack()) {
+		pr_err("invalid max stack depth: %ld\n", val);
+		return -1;
+	}
+
+	*len = val;
+	return 0;
+}
+
 int cmd_lock(int argc, const char **argv)
 {
 	const struct option lock_options[] = {
@@ -1913,9 +1937,9 @@ int cmd_lock(int argc, const char **argv)
 		   "Trace on existing thread id (exclusive to --pid)"),
 	OPT_CALLBACK(0, "map-nr-entries", &bpf_map_entries, "num",
 		     "Max number of BPF map entries", parse_map_entry),
-	OPT_INTEGER(0, "max-stack", &max_stack_depth,
-		    "Set the maximum stack depth when collecting lock contention, "
-		    "Default: " __stringify(CONTENTION_STACK_DEPTH)),
+	OPT_CALLBACK(0, "max-stack", &max_stack_depth, "num",
+		     "Set the maximum stack depth when collecting lopck contention, "
+		     "Default: " __stringify(CONTENTION_STACK_DEPTH), parse_max_stack),
 	OPT_INTEGER(0, "stack-skip", &stack_skip,
 		    "Set the number of stack depth to skip when finding a lock caller, "
 		    "Default: " __stringify(CONTENTION_STACK_SKIP)),
-- 
2.38.1.273.g43a17bfeac-goog