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, 126 insertions, 0 deletions

diff --git a/drivers/char/nsc_gpio.c b/drivers/char/nsc_gpio.c
new file mode 100644
index 000000000..2c9b12b85
--- /dev/null
+++ b/drivers/char/nsc_gpio.c
@@ -0,0 +1,126 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* linux/drivers/char/nsc_gpio.c
+
+   National Semiconductor common GPIO device-file/VFS methods.
+   Allows a user space process to control the GPIO pins.
+
+   Copyright (c) 2001,2002 Christer Weinigel <wingel@nano-system.com>
+   Copyright (c) 2005      Jim Cromie <jim.cromie@gmail.com>
+*/
+
+#include <linux/fs.h>
+#include <linux/module.h>
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/nsc_gpio.h>
+#include <linux/platform_device.h>
+#include <linux/uaccess.h>
+#include <asm/io.h>
+
+#define NAME "nsc_gpio"
+
+void nsc_gpio_dump(struct nsc_gpio_ops *amp, unsigned index)
+{
+	/* retrieve current config w/o changing it */
+	u32 config = amp->gpio_config(index, ~0, 0);
+
+	/* user requested via 'v' command, so its INFO */
+	dev_info(amp->dev, "io%02u: 0x%04x %s %s %s %s %s %s %s\tio:%d/%d\n",
+		 index, config,
+		 (config & 1) ? "OE" : "TS",      /* output-enabled/tristate */
+		 (config & 2) ? "PP" : "OD",      /* push pull / open drain */
+		 (config & 4) ? "PUE" : "PUD",    /* pull up enabled/disabled */
+		 (config & 8) ? "LOCKED" : "",    /* locked / unlocked */
+		 (config & 16) ? "LEVEL" : "EDGE",/* level/edge input */
+		 (config & 32) ? "HI" : "LO",     /* trigger on rise/fall edge */
+		 (config & 64) ? "DEBOUNCE" : "", /* debounce */
+
+		 amp->gpio_get(index), amp->gpio_current(index));
+}
+
+ssize_t nsc_gpio_write(struct file *file, const char __user *data,
+		       size_t len, loff_t *ppos)
+{
+	unsigned m = iminor(file_inode(file));
+	struct nsc_gpio_ops *amp = file->private_data;
+	struct device *dev = amp->dev;
+	size_t i;
+	int err = 0;
+
+	for (i = 0; i < len; ++i) {
+		char c;
+		if (get_user(c, data + i))
+			return -EFAULT;
+		switch (c) {
+		case '0':
+			amp->gpio_set(m, 0);
+			break;
+		case '1':
+			amp->gpio_set(m, 1);
+			break;
+		case 'O':
+			dev_dbg(dev, "GPIO%d output enabled\n", m);
+			amp->gpio_config(m, ~1, 1);
+			break;
+		case 'o':
+			dev_dbg(dev, "GPIO%d output disabled\n", m);
+			amp->gpio_config(m, ~1, 0);
+			break;
+		case 'T':
+			dev_dbg(dev, "GPIO%d output is push pull\n", m);
+			amp->gpio_config(m, ~2, 2);
+			break;
+		case 't':
+			dev_dbg(dev, "GPIO%d output is open drain\n", m);
+			amp->gpio_config(m, ~2, 0);
+			break;
+		case 'P':
+			dev_dbg(dev, "GPIO%d pull up enabled\n", m);
+			amp->gpio_config(m, ~4, 4);
+			break;
+		case 'p':
+			dev_dbg(dev, "GPIO%d pull up disabled\n", m);
+			amp->gpio_config(m, ~4, 0);
+			break;
+		case 'v':
+			/* View Current pin settings */
+			amp->gpio_dump(amp, m);
+			break;
+		case '\n':
+			/* end of settings string, do nothing */
+			break;
+		default:
+			dev_err(dev, "io%2d bad setting: chr<0x%2x>\n",
+				m, (int)c);
+			err++;
+		}
+	}
+	if (err)
+		return -EINVAL;	/* full string handled, report error */
+
+	return len;
+}
+
+ssize_t nsc_gpio_read(struct file *file, char __user * buf,
+		      size_t len, loff_t * ppos)
+{
+	unsigned m = iminor(file_inode(file));
+	int value;
+	struct nsc_gpio_ops *amp = file->private_data;
+
+	value = amp->gpio_get(m);
+	if (put_user(value ? '1' : '0', buf))
+		return -EFAULT;
+
+	return 1;
+}
+
+/* common file-ops routines for both scx200_gpio and pc87360_gpio */
+EXPORT_SYMBOL(nsc_gpio_write);
+EXPORT_SYMBOL(nsc_gpio_read);
+EXPORT_SYMBOL(nsc_gpio_dump);
+
+MODULE_AUTHOR("Jim Cromie <jim.cromie@gmail.com>");
+MODULE_DESCRIPTION("NatSemi GPIO Common Methods");
+MODULE_LICENSE("GPL");