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, 176 insertions, 0 deletions

diff --git a/tools/gpio/gpio-hammer.c b/tools/gpio/gpio-hammer.c
new file mode 100644
index 000000000..ba0866eb3
--- /dev/null
+++ b/tools/gpio/gpio-hammer.c
@@ -0,0 +1,176 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * gpio-hammer - example swiss army knife to shake GPIO lines on a system
+ *
+ * Copyright (C) 2016 Linus Walleij
+ *
+ * Usage:
+ *	gpio-hammer -n <device-name> -o <offset1> -o <offset2>
+ */
+
+#include <unistd.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <dirent.h>
+#include <errno.h>
+#include <string.h>
+#include <poll.h>
+#include <fcntl.h>
+#include <getopt.h>
+#include <sys/ioctl.h>
+#include <linux/gpio.h>
+#include "gpio-utils.h"
+
+int hammer_device(const char *device_name, unsigned int *lines, int num_lines,
+		  unsigned int loops)
+{
+	struct gpio_v2_line_values values;
+	struct gpio_v2_line_config config;
+	char swirr[] = "-\\|/";
+	int fd;
+	int ret;
+	int i, j;
+	unsigned int iteration = 0;
+
+	memset(&config, 0, sizeof(config));
+	config.flags = GPIO_V2_LINE_FLAG_OUTPUT;
+
+	ret = gpiotools_request_line(device_name, lines, num_lines,
+				     &config, "gpio-hammer");
+	if (ret < 0)
+		goto exit_error;
+	else
+		fd = ret;
+
+	values.mask = 0;
+	values.bits = 0;
+	for (i = 0; i < num_lines; i++)
+		gpiotools_set_bit(&values.mask, i);
+
+	ret = gpiotools_get_values(fd, &values);
+	if (ret < 0)
+		goto exit_close_error;
+
+	fprintf(stdout, "Hammer lines [");
+	for (i = 0; i < num_lines; i++) {
+		fprintf(stdout, "%u", lines[i]);
+		if (i != (num_lines - 1))
+			fprintf(stdout, ", ");
+	}
+	fprintf(stdout, "] on %s, initial states: [", device_name);
+	for (i = 0; i < num_lines; i++) {
+		fprintf(stdout, "%d", gpiotools_test_bit(values.bits, i));
+		if (i != (num_lines - 1))
+			fprintf(stdout, ", ");
+	}
+	fprintf(stdout, "]\n");
+
+	/* Hammertime! */
+	j = 0;
+	while (1) {
+		/* Invert all lines so we blink */
+		for (i = 0; i < num_lines; i++)
+			gpiotools_change_bit(&values.bits, i);
+
+		ret = gpiotools_set_values(fd, &values);
+		if (ret < 0)
+			goto exit_close_error;
+
+		/* Re-read values to get status */
+		ret = gpiotools_get_values(fd, &values);
+		if (ret < 0)
+			goto exit_close_error;
+
+		fprintf(stdout, "[%c] ", swirr[j]);
+		j++;
+		if (j == sizeof(swirr) - 1)
+			j = 0;
+
+		fprintf(stdout, "[");
+		for (i = 0; i < num_lines; i++) {
+			fprintf(stdout, "%u: %d", lines[i],
+				gpiotools_test_bit(values.bits, i));
+			if (i != (num_lines - 1))
+				fprintf(stdout, ", ");
+		}
+		fprintf(stdout, "]\r");
+		fflush(stdout);
+		sleep(1);
+		iteration++;
+		if (loops && iteration == loops)
+			break;
+	}
+	fprintf(stdout, "\n");
+	ret = 0;
+
+exit_close_error:
+	gpiotools_release_line(fd);
+exit_error:
+	return ret;
+}
+
+void print_usage(void)
+{
+	fprintf(stderr, "Usage: gpio-hammer [options]...\n"
+		"Hammer GPIO lines, 0->1->0->1...\n"
+		"  -n <name>  Hammer GPIOs on a named device (must be stated)\n"
+		"  -o <n>     Offset[s] to hammer, at least one, several can be stated\n"
+		" [-c <n>]    Do <n> loops (optional, infinite loop if not stated)\n"
+		"  -?         This helptext\n"
+		"\n"
+		"Example:\n"
+		"gpio-hammer -n gpiochip0 -o 4\n"
+	);
+}
+
+int main(int argc, char **argv)
+{
+	const char *device_name = NULL;
+	unsigned int lines[GPIOHANDLES_MAX];
+	unsigned int loops = 0;
+	int num_lines;
+	int c;
+	int i;
+
+	i = 0;
+	while ((c = getopt(argc, argv, "c:n:o:?")) != -1) {
+		switch (c) {
+		case 'c':
+			loops = strtoul(optarg, NULL, 10);
+			break;
+		case 'n':
+			device_name = optarg;
+			break;
+		case 'o':
+			/*
+			 * Avoid overflow. Do not immediately error, we want to
+			 * be able to accurately report on the amount of times
+			 * '-o' was given to give an accurate error message
+			 */
+			if (i < GPIOHANDLES_MAX)
+				lines[i] = strtoul(optarg, NULL, 10);
+
+			i++;
+			break;
+		case '?':
+			print_usage();
+			return -1;
+		}
+	}
+
+	if (i >= GPIOHANDLES_MAX) {
+		fprintf(stderr,
+			"Only %d occurrences of '-o' are allowed, %d were found\n",
+			GPIOHANDLES_MAX, i + 1);
+		return -1;
+	}
+
+	num_lines = i;
+
+	if (!device_name || !num_lines) {
+		print_usage();
+		return -1;
+	}
+	return hammer_device(device_name, lines, num_lines, loops);
+}