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, 361 insertions, 0 deletions

diff --git a/fs/pstore/blk.c b/fs/pstore/blk.c
new file mode 100644
index 000000000..12070b6a7
--- /dev/null
+++ b/fs/pstore/blk.c
@@ -0,0 +1,361 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Implements pstore backend driver that write to block (or non-block) storage
+ * devices, using the pstore/zone API.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/blkdev.h>
+#include <linux/string.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/platform_device.h>
+#include <linux/pstore_blk.h>
+#include <linux/fs.h>
+#include <linux/file.h>
+#include <linux/init_syscalls.h>
+#include <linux/mount.h>
+
+static long kmsg_size = CONFIG_PSTORE_BLK_KMSG_SIZE;
+module_param(kmsg_size, long, 0400);
+MODULE_PARM_DESC(kmsg_size, "kmsg dump record size in kbytes");
+
+static int max_reason = CONFIG_PSTORE_BLK_MAX_REASON;
+module_param(max_reason, int, 0400);
+MODULE_PARM_DESC(max_reason,
+		 "maximum reason for kmsg dump (default 2: Oops and Panic)");
+
+#if IS_ENABLED(CONFIG_PSTORE_PMSG)
+static long pmsg_size = CONFIG_PSTORE_BLK_PMSG_SIZE;
+#else
+static long pmsg_size = -1;
+#endif
+module_param(pmsg_size, long, 0400);
+MODULE_PARM_DESC(pmsg_size, "pmsg size in kbytes");
+
+#if IS_ENABLED(CONFIG_PSTORE_CONSOLE)
+static long console_size = CONFIG_PSTORE_BLK_CONSOLE_SIZE;
+#else
+static long console_size = -1;
+#endif
+module_param(console_size, long, 0400);
+MODULE_PARM_DESC(console_size, "console size in kbytes");
+
+#if IS_ENABLED(CONFIG_PSTORE_FTRACE)
+static long ftrace_size = CONFIG_PSTORE_BLK_FTRACE_SIZE;
+#else
+static long ftrace_size = -1;
+#endif
+module_param(ftrace_size, long, 0400);
+MODULE_PARM_DESC(ftrace_size, "ftrace size in kbytes");
+
+static bool best_effort;
+module_param(best_effort, bool, 0400);
+MODULE_PARM_DESC(best_effort, "use best effort to write (i.e. do not require storage driver pstore support, default: off)");
+
+/*
+ * blkdev - the block device to use for pstore storage
+ * See Documentation/admin-guide/pstore-blk.rst for details.
+ */
+static char blkdev[80] = CONFIG_PSTORE_BLK_BLKDEV;
+module_param_string(blkdev, blkdev, 80, 0400);
+MODULE_PARM_DESC(blkdev, "block device for pstore storage");
+
+/*
+ * All globals must only be accessed under the pstore_blk_lock
+ * during the register/unregister functions.
+ */
+static DEFINE_MUTEX(pstore_blk_lock);
+static struct file *psblk_file;
+static struct pstore_device_info *pstore_device_info;
+
+#define check_size(name, alignsize) ({				\
+	long _##name_ = (name);					\
+	_##name_ = _##name_ <= 0 ? 0 : (_##name_ * 1024);	\
+	if (_##name_ & ((alignsize) - 1)) {			\
+		pr_info(#name " must align to %d\n",		\
+				(alignsize));			\
+		_##name_ = ALIGN(name, (alignsize));		\
+	}							\
+	_##name_;						\
+})
+
+#define verify_size(name, alignsize, enabled) {			\
+	long _##name_;						\
+	if (enabled)						\
+		_##name_ = check_size(name, alignsize);		\
+	else							\
+		_##name_ = 0;					\
+	/* Synchronize module parameters with results. */	\
+	name = _##name_ / 1024;					\
+	dev->zone.name = _##name_;				\
+}
+
+static int __register_pstore_device(struct pstore_device_info *dev)
+{
+	int ret;
+
+	lockdep_assert_held(&pstore_blk_lock);
+
+	if (!dev) {
+		pr_err("NULL device info\n");
+		return -EINVAL;
+	}
+	if (!dev->zone.total_size) {
+		pr_err("zero sized device\n");
+		return -EINVAL;
+	}
+	if (!dev->zone.read) {
+		pr_err("no read handler for device\n");
+		return -EINVAL;
+	}
+	if (!dev->zone.write) {
+		pr_err("no write handler for device\n");
+		return -EINVAL;
+	}
+
+	/* someone already registered before */
+	if (pstore_device_info)
+		return -EBUSY;
+
+	/* zero means no limit on which backends attempt to store. */
+	if (!dev->flags)
+		dev->flags = UINT_MAX;
+
+	/* Copy in module parameters. */
+	verify_size(kmsg_size, 4096, dev->flags & PSTORE_FLAGS_DMESG);
+	verify_size(pmsg_size, 4096, dev->flags & PSTORE_FLAGS_PMSG);
+	verify_size(console_size, 4096, dev->flags & PSTORE_FLAGS_CONSOLE);
+	verify_size(ftrace_size, 4096, dev->flags & PSTORE_FLAGS_FTRACE);
+	dev->zone.max_reason = max_reason;
+
+	/* Initialize required zone ownership details. */
+	dev->zone.name = KBUILD_MODNAME;
+	dev->zone.owner = THIS_MODULE;
+
+	ret = register_pstore_zone(&dev->zone);
+	if (ret == 0)
+		pstore_device_info = dev;
+
+	return ret;
+}
+/**
+ * register_pstore_device() - register non-block device to pstore/blk
+ *
+ * @dev: non-block device information
+ *
+ * Return:
+ * * 0		- OK
+ * * Others	- something error.
+ */
+int register_pstore_device(struct pstore_device_info *dev)
+{
+	int ret;
+
+	mutex_lock(&pstore_blk_lock);
+	ret = __register_pstore_device(dev);
+	mutex_unlock(&pstore_blk_lock);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(register_pstore_device);
+
+static void __unregister_pstore_device(struct pstore_device_info *dev)
+{
+	lockdep_assert_held(&pstore_blk_lock);
+	if (pstore_device_info && pstore_device_info == dev) {
+		unregister_pstore_zone(&dev->zone);
+		pstore_device_info = NULL;
+	}
+}
+
+/**
+ * unregister_pstore_device() - unregister non-block device from pstore/blk
+ *
+ * @dev: non-block device information
+ */
+void unregister_pstore_device(struct pstore_device_info *dev)
+{
+	mutex_lock(&pstore_blk_lock);
+	__unregister_pstore_device(dev);
+	mutex_unlock(&pstore_blk_lock);
+}
+EXPORT_SYMBOL_GPL(unregister_pstore_device);
+
+static ssize_t psblk_generic_blk_read(char *buf, size_t bytes, loff_t pos)
+{
+	return kernel_read(psblk_file, buf, bytes, &pos);
+}
+
+static ssize_t psblk_generic_blk_write(const char *buf, size_t bytes,
+		loff_t pos)
+{
+	/* Console/Ftrace backend may handle buffer until flush dirty zones */
+	if (in_interrupt() || irqs_disabled())
+		return -EBUSY;
+	return kernel_write(psblk_file, buf, bytes, &pos);
+}
+
+/*
+ * This takes its configuration only from the module parameters now.
+ */
+static int __register_pstore_blk(struct pstore_device_info *dev,
+				 const char *devpath)
+{
+	int ret = -ENODEV;
+
+	lockdep_assert_held(&pstore_blk_lock);
+
+	psblk_file = filp_open(devpath, O_RDWR | O_DSYNC | O_NOATIME | O_EXCL, 0);
+	if (IS_ERR(psblk_file)) {
+		ret = PTR_ERR(psblk_file);
+		pr_err("failed to open '%s': %d!\n", devpath, ret);
+		goto err;
+	}
+
+	if (!S_ISBLK(file_inode(psblk_file)->i_mode)) {
+		pr_err("'%s' is not block device!\n", devpath);
+		goto err_fput;
+	}
+
+	dev->zone.total_size =
+		bdev_nr_bytes(I_BDEV(psblk_file->f_mapping->host));
+
+	ret = __register_pstore_device(dev);
+	if (ret)
+		goto err_fput;
+
+	return 0;
+
+err_fput:
+	fput(psblk_file);
+err:
+	psblk_file = NULL;
+
+	return ret;
+}
+
+/* get information of pstore/blk */
+int pstore_blk_get_config(struct pstore_blk_config *info)
+{
+	strscpy(info->device, blkdev);
+	info->max_reason = max_reason;
+	info->kmsg_size = check_size(kmsg_size, 4096);
+	info->pmsg_size = check_size(pmsg_size, 4096);
+	info->ftrace_size = check_size(ftrace_size, 4096);
+	info->console_size = check_size(console_size, 4096);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(pstore_blk_get_config);
+
+
+#ifndef MODULE
+static const char devname[] = "/dev/pstore-blk";
+static __init const char *early_boot_devpath(const char *initial_devname)
+{
+	/*
+	 * During early boot the real root file system hasn't been
+	 * mounted yet, and no device nodes are present yet. Use the
+	 * same scheme to find the device that we use for mounting
+	 * the root file system.
+	 */
+	dev_t dev;
+
+	if (early_lookup_bdev(initial_devname, &dev)) {
+		pr_err("failed to resolve '%s'!\n", initial_devname);
+		return initial_devname;
+	}
+
+	init_unlink(devname);
+	init_mknod(devname, S_IFBLK | 0600, new_encode_dev(dev));
+
+	return devname;
+}
+#else
+static inline const char *early_boot_devpath(const char *initial_devname)
+{
+	return initial_devname;
+}
+#endif
+
+static int __init __best_effort_init(void)
+{
+	struct pstore_device_info *best_effort_dev;
+	int ret;
+
+	/* No best-effort mode requested. */
+	if (!best_effort)
+		return 0;
+
+	/* Reject an empty blkdev. */
+	if (!blkdev[0]) {
+		pr_err("blkdev empty with best_effort=Y\n");
+		return -EINVAL;
+	}
+
+	best_effort_dev = kzalloc_obj(*best_effort_dev);
+	if (!best_effort_dev)
+		return -ENOMEM;
+
+	best_effort_dev->zone.read = psblk_generic_blk_read;
+	best_effort_dev->zone.write = psblk_generic_blk_write;
+
+	ret = __register_pstore_blk(best_effort_dev,
+				    early_boot_devpath(blkdev));
+	if (ret)
+		kfree(best_effort_dev);
+	else
+		pr_info("attached %s (%lu) (no dedicated panic_write!)\n",
+			blkdev, best_effort_dev->zone.total_size);
+
+	return ret;
+}
+
+static void __exit __best_effort_exit(void)
+{
+	/*
+	 * Currently, the only user of psblk_file is best_effort, so
+	 * we can assume that pstore_device_info is associated with it.
+	 * Once there are "real" blk devices, there will need to be a
+	 * dedicated pstore_blk_info, etc.
+	 */
+	if (psblk_file) {
+		struct pstore_device_info *dev = pstore_device_info;
+
+		__unregister_pstore_device(dev);
+		kfree(dev);
+		fput(psblk_file);
+		psblk_file = NULL;
+	}
+}
+
+static int __init pstore_blk_init(void)
+{
+	int ret;
+
+	mutex_lock(&pstore_blk_lock);
+	ret = __best_effort_init();
+	mutex_unlock(&pstore_blk_lock);
+
+	return ret;
+}
+late_initcall(pstore_blk_init);
+
+static void __exit pstore_blk_exit(void)
+{
+	mutex_lock(&pstore_blk_lock);
+	__best_effort_exit();
+	/* If we've been asked to unload, unregister any remaining device. */
+	__unregister_pstore_device(pstore_device_info);
+	mutex_unlock(&pstore_blk_lock);
+}
+module_exit(pstore_blk_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("WeiXiong Liao <liaoweixiong@allwinnertech.com>");
+MODULE_AUTHOR("Kees Cook <keescook@chromium.org>");
+MODULE_DESCRIPTION("pstore backend for block devices");