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, 298 insertions, 0 deletions

diff --git a/tools/perf/builtin-config.c b/tools/perf/builtin-config.c
new file mode 100644
index 000000000..237600643
--- /dev/null
+++ b/tools/perf/builtin-config.c
@@ -0,0 +1,298 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * builtin-config.c
+ *
+ * Copyright (C) 2015, Taeung Song <treeze.taeung@gmail.com>
+ *
+ */
+#include "builtin.h"
+
+#include "util/cache.h"
+#include <subcmd/parse-options.h>
+#include "util/debug.h"
+#include "util/config.h"
+#include <linux/string.h>
+#include <limits.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+static bool use_system_config, use_user_config;
+
+static const char * const config_usage[] = {
+	"perf config [<file-option>] [options] [section.name[=value] ...]",
+	NULL
+};
+
+static enum actions {
+	ACTION_LIST = 1
+} actions;
+
+static struct option config_options[] = {
+	OPT_SET_UINT('l', "list", &actions,
+		     "show current config variables", ACTION_LIST),
+	OPT_BOOLEAN(0, "system", &use_system_config, "use system config file"),
+	OPT_BOOLEAN(0, "user", &use_user_config, "use user config file"),
+	OPT_END()
+};
+
+static int set_config(struct perf_config_set *set, const char *file_name)
+{
+	struct perf_config_section *section = NULL;
+	struct perf_config_item *item = NULL;
+	const char *first_line = "# this file is auto-generated.";
+	FILE *fp;
+
+	if (set == NULL)
+		return -1;
+
+	fp = fopen(file_name, "w");
+	if (!fp)
+		return -1;
+
+	fprintf(fp, "%s\n", first_line);
+
+	/* overwrite configvariables */
+	perf_config_items__for_each_entry(&set->sections, section) {
+		if (!use_system_config && section->from_system_config)
+			continue;
+		fprintf(fp, "[%s]\n", section->name);
+
+		perf_config_items__for_each_entry(&section->items, item) {
+			if (!use_system_config && item->from_system_config)
+				continue;
+			if (item->value)
+				fprintf(fp, "\t%s = %s\n",
+					item->name, item->value);
+		}
+	}
+	fclose(fp);
+
+	return 0;
+}
+
+static int show_spec_config(struct perf_config_set *set, const char *var)
+{
+	struct perf_config_section *section;
+	struct perf_config_item *item;
+
+	if (set == NULL)
+		return -1;
+
+	perf_config_items__for_each_entry(&set->sections, section) {
+		if (!strstarts(var, section->name))
+			continue;
+
+		perf_config_items__for_each_entry(&section->items, item) {
+			const char *name = var + strlen(section->name) + 1;
+
+			if (strcmp(name, item->name) == 0) {
+				char *value = item->value;
+
+				if (value) {
+					printf("%s=%s\n", var, value);
+					return 0;
+				}
+			}
+
+		}
+	}
+
+	return 0;
+}
+
+static int show_config(struct perf_config_set *set)
+{
+	struct perf_config_section *section;
+	struct perf_config_item *item;
+
+	if (set == NULL)
+		return -1;
+
+	perf_config_set__for_each_entry(set, section, item) {
+		char *value = item->value;
+
+		if (value)
+			printf("%s.%s=%s\n", section->name,
+			       item->name, value);
+	}
+
+	return 0;
+}
+
+static int parse_config_arg(char *arg, char **var, char **value)
+{
+	const char *last_dot = strchr(arg, '.');
+
+	/*
+	 * Since "var" actually contains the section name and the real
+	 * config variable name separated by a dot, we have to know where the dot is.
+	 */
+	if (last_dot == NULL || last_dot == arg) {
+		pr_err("The config variable does not contain a section name: %s\n", arg);
+		return -1;
+	}
+	if (!last_dot[1]) {
+		pr_err("The config variable does not contain a variable name: %s\n", arg);
+		return -1;
+	}
+
+	*value = strchr(arg, '=');
+	if (*value == NULL)
+		*var = arg;
+	else if (!strcmp(*value, "=")) {
+		pr_err("The config variable does not contain a value: %s\n", arg);
+		return -1;
+	} else {
+		*value = *value + 1; /* excluding a first character '=' */
+		*var = strsep(&arg, "=");
+		if (*var[0] == '\0') {
+			pr_err("invalid config variable: %s\n", arg);
+			return -1;
+		}
+	}
+
+	return 0;
+}
+
+int perf_config__set_variable(const char *var, const char *value)
+{
+	char path[PATH_MAX];
+	char *user_config = mkpath(path, sizeof(path), "%s/.perfconfig", getenv("HOME"));
+	const char *config_filename;
+	struct perf_config_set *set;
+	int ret = -1;
+
+	if (use_system_config)
+		config_exclusive_filename = perf_etc_perfconfig();
+	else if (use_user_config)
+		config_exclusive_filename = user_config;
+
+	if (!config_exclusive_filename)
+		config_filename = user_config;
+	else
+		config_filename = config_exclusive_filename;
+
+	set = perf_config_set__new();
+	if (!set)
+		goto out_err;
+
+	if (perf_config_set__collect(set, config_filename, var, value) < 0) {
+		pr_err("Failed to add '%s=%s'\n", var, value);
+		goto out_err;
+	}
+
+	if (set_config(set, config_filename) < 0) {
+		pr_err("Failed to set the configs on %s\n", config_filename);
+		goto out_err;
+	}
+
+	ret = 0;
+out_err:
+	perf_config_set__delete(set);
+	return ret;
+}
+
+int cmd_config(int argc, const char **argv)
+{
+	int i, ret = -1;
+	struct perf_config_set *set;
+	char path[PATH_MAX];
+	char *user_config = mkpath(path, sizeof(path), "%s/.perfconfig", getenv("HOME"));
+	const char *config_filename;
+	bool changed = false;
+
+	argc = parse_options(argc, argv, config_options, config_usage,
+			     PARSE_OPT_STOP_AT_NON_OPTION);
+
+	if (use_system_config && use_user_config) {
+		pr_err("Error: only one config file at a time\n");
+		parse_options_usage(config_usage, config_options, "user", 0);
+		parse_options_usage(NULL, config_options, "system", 0);
+		return -1;
+	}
+
+	if (use_system_config)
+		config_exclusive_filename = perf_etc_perfconfig();
+	else if (use_user_config)
+		config_exclusive_filename = user_config;
+
+	if (!config_exclusive_filename)
+		config_filename = user_config;
+	else
+		config_filename = config_exclusive_filename;
+
+	/*
+	 * At only 'config' sub-command, individually use the config set
+	 * because of reinitializing with options config file location.
+	 */
+	set = perf_config_set__new();
+	if (!set)
+		goto out_err;
+
+	switch (actions) {
+	case ACTION_LIST:
+		if (argc) {
+			pr_err("Error: takes no arguments\n");
+			parse_options_usage(config_usage, config_options, "l", 1);
+		} else {
+do_action_list:
+			if (show_config(set) < 0) {
+				pr_err("Nothing configured, "
+				       "please check your %s \n", config_filename);
+				goto out_err;
+			}
+		}
+		break;
+	default:
+		if (!argc)
+			goto do_action_list;
+
+		for (i = 0; argv[i]; i++) {
+			char *var, *value;
+			char *arg = strdup(argv[i]);
+
+			if (!arg) {
+				pr_err("%s: strdup failed\n", __func__);
+				goto out_err;
+			}
+
+			if (parse_config_arg(arg, &var, &value) < 0) {
+				free(arg);
+				goto out_err;
+			}
+
+			if (value == NULL) {
+				if (show_spec_config(set, var) < 0) {
+					pr_err("%s is not configured: %s\n",
+					       var, config_filename);
+					free(arg);
+					goto out_err;
+				}
+			} else {
+				if (perf_config_set__collect(set, config_filename,
+							     var, value) < 0) {
+					pr_err("Failed to add '%s=%s'\n",
+					       var, value);
+					free(arg);
+					goto out_err;
+				}
+				changed = true;
+			}
+			free(arg);
+		}
+
+		if (!changed)
+			break;
+
+		if (set_config(set, config_filename) < 0) {
+			pr_err("Failed to set the configs on %s\n",
+			       config_filename);
+			goto out_err;
+		}
+	}
+
+	ret = 0;
+out_err:
+	perf_config_set__delete(set);
+	return ret;
+}