ftrace: Synchronize the initialization of ftrace_opsgrafted

There's some internal state that ftrace_ops needs to have set, but since
it can be declared outside of the ftrace.c code, it calls
ftrace_ops_init() on the ops in every global function. The issue is that
if two tasks call it on the same ops at the same time it is possible to
have the initialization of one corrupt the initialization of the other
call.

Create a ops_mutex to use to synchronize every initialization of the
ftrace_ops. The mutex is taken within checking the ftrace_ops flag that
states it was initializied but the flag is checked again after the mutex
has been taken. Checking first outside the mutex allows it to shortcut
having to take the mutex. But then the check needs to be done again after
the mute is taken in case of races.

Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home
Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock")
Reported-by: sashiko-bot@kernel.org
Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 142 insertions, 0 deletions

diff --git a/tools/perf/util/target.c b/tools/perf/util/target.c
new file mode 100644
index 000000000..8cf71bea2
--- /dev/null
+++ b/tools/perf/util/target.c
@@ -0,0 +1,142 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Helper functions for handling target threads/cpus
+ *
+ * Copyright (C) 2012, LG Electronics, Namhyung Kim <namhyung.kim@lge.com>
+ */
+
+#include "target.h"
+
+#include <pwd.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <linux/kernel.h>
+#include <linux/string.h>
+
+enum target_errno target__validate(struct target *target)
+{
+	enum target_errno ret = TARGET_ERRNO__SUCCESS;
+
+	if (target->pid)
+		target->tid = target->pid;
+
+	/* CPU and PID are mutually exclusive */
+	if (target->tid && target->cpu_list) {
+		target->cpu_list = NULL;
+		if (ret == TARGET_ERRNO__SUCCESS)
+			ret = TARGET_ERRNO__PID_OVERRIDE_CPU;
+	}
+
+	/* PID and SYSTEM are mutually exclusive */
+	if (target->tid && target->system_wide) {
+		target->system_wide = false;
+		if (ret == TARGET_ERRNO__SUCCESS)
+			ret = TARGET_ERRNO__PID_OVERRIDE_SYSTEM;
+	}
+
+	/* BPF and CPU are mutually exclusive */
+	if (target->bpf_str && target->cpu_list) {
+		target->cpu_list = NULL;
+		if (ret == TARGET_ERRNO__SUCCESS)
+			ret = TARGET_ERRNO__BPF_OVERRIDE_CPU;
+	}
+
+	/* BPF and PID/TID are mutually exclusive */
+	if (target->bpf_str && target->tid) {
+		target->tid = NULL;
+		if (ret == TARGET_ERRNO__SUCCESS)
+			ret = TARGET_ERRNO__BPF_OVERRIDE_PID;
+	}
+
+	/* BPF and THREADS are mutually exclusive */
+	if (target->bpf_str && target->per_thread) {
+		target->per_thread = false;
+		if (ret == TARGET_ERRNO__SUCCESS)
+			ret = TARGET_ERRNO__BPF_OVERRIDE_THREAD;
+	}
+
+	/* THREAD and SYSTEM/CPU are mutually exclusive */
+	if (target->per_thread && (target->system_wide || target->cpu_list)) {
+		target->per_thread = false;
+		if (ret == TARGET_ERRNO__SUCCESS)
+			ret = TARGET_ERRNO__SYSTEM_OVERRIDE_THREAD;
+	}
+
+	return ret;
+}
+
+uid_t parse_uid(const char *str)
+{
+	struct passwd pwd, *result;
+	char buf[1024];
+
+	if (str == NULL)
+		return UINT_MAX;
+
+	/* Try user name first */
+	getpwnam_r(str, &pwd, buf, sizeof(buf), &result);
+
+	if (result == NULL) {
+		/*
+		 * The user name not found. Maybe it's a UID number.
+		 */
+		char *endptr;
+		int uid = strtol(str, &endptr, 10);
+
+		if (*endptr != '\0')
+			return UINT_MAX;
+
+		getpwuid_r(uid, &pwd, buf, sizeof(buf), &result);
+
+		if (result == NULL)
+			return UINT_MAX;
+	}
+
+	return result->pw_uid;
+}
+
+/*
+ * This must have a same ordering as the enum target_errno.
+ */
+static const char *target__error_str[] = {
+	"PID/TID switch overriding CPU",
+	"PID/TID switch overriding SYSTEM",
+	"SYSTEM/CPU switch overriding PER-THREAD",
+	"BPF switch overriding CPU",
+	"BPF switch overriding PID/TID",
+	"BPF switch overriding THREAD",
+};
+
+int target__strerror(struct target *target __maybe_unused, int errnum,
+			  char *buf, size_t buflen)
+{
+	int idx;
+	const char *msg;
+
+	BUG_ON(buflen == 0);
+
+	if (errnum >= 0) {
+		str_error_r(errnum, buf, buflen);
+		return 0;
+	}
+
+	if (errnum <  __TARGET_ERRNO__START || errnum >= __TARGET_ERRNO__END)
+		return -1;
+
+	idx = errnum - __TARGET_ERRNO__START;
+	msg = target__error_str[idx];
+
+	switch (errnum) {
+	case TARGET_ERRNO__PID_OVERRIDE_CPU ...
+	     TARGET_ERRNO__BPF_OVERRIDE_THREAD:
+		snprintf(buf, buflen, "%s", msg);
+		break;
+
+	default:
+		/* cannot reach here */
+		break;
+	}
+
+	return 0;
+}