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, 215 insertions, 0 deletions

diff --git a/drivers/sbus/char/flash.c b/drivers/sbus/char/flash.c
new file mode 100644
index 000000000..6524a4a19
--- /dev/null
+++ b/drivers/sbus/char/flash.c
@@ -0,0 +1,215 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* flash.c: Allow mmap access to the OBP Flash, for OBP updates.
+ *
+ * Copyright (C) 1997  Eddie C. Dost  (ecd@skynet.be)
+ */
+
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/errno.h>
+#include <linux/miscdevice.h>
+#include <linux/fcntl.h>
+#include <linux/poll.h>
+#include <linux/mutex.h>
+#include <linux/spinlock.h>
+#include <linux/mm.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+
+#include <linux/uaccess.h>
+#include <asm/io.h>
+#include <asm/upa.h>
+
+static DEFINE_MUTEX(flash_mutex);
+static DEFINE_SPINLOCK(flash_lock);
+static struct {
+	unsigned long read_base;	/* Physical read address */
+	unsigned long write_base;	/* Physical write address */
+	unsigned long read_size;	/* Size of read area */
+	unsigned long write_size;	/* Size of write area */
+	unsigned long busy;		/* In use? */
+} flash;
+
+static int
+flash_mmap(struct file *file, struct vm_area_struct *vma)
+{
+	unsigned long addr;
+	unsigned long size;
+
+	spin_lock(&flash_lock);
+	if (flash.read_base == flash.write_base) {
+		addr = flash.read_base;
+		size = flash.read_size;
+	} else {
+		if ((vma->vm_flags & VM_READ) &&
+		    (vma->vm_flags & VM_WRITE)) {
+			spin_unlock(&flash_lock);
+			return -EINVAL;
+		}
+		if (vma->vm_flags & VM_READ) {
+			addr = flash.read_base;
+			size = flash.read_size;
+		} else if (vma->vm_flags & VM_WRITE) {
+			addr = flash.write_base;
+			size = flash.write_size;
+		} else {
+			spin_unlock(&flash_lock);
+			return -ENXIO;
+		}
+	}
+	spin_unlock(&flash_lock);
+
+	if ((vma->vm_pgoff << PAGE_SHIFT) > size)
+		return -ENXIO;
+	addr = vma->vm_pgoff + (addr >> PAGE_SHIFT);
+
+	if (vma->vm_end - (vma->vm_start + (vma->vm_pgoff << PAGE_SHIFT)) > size)
+		size = vma->vm_end - (vma->vm_start + (vma->vm_pgoff << PAGE_SHIFT));
+
+	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
+
+	if (io_remap_pfn_range(vma, vma->vm_start, addr, size, vma->vm_page_prot))
+		return -EAGAIN;
+		
+	return 0;
+}
+
+static long long
+flash_llseek(struct file *file, long long offset, int origin)
+{
+	mutex_lock(&flash_mutex);
+	switch (origin) {
+		case 0:
+			file->f_pos = offset;
+			break;
+		case 1:
+			file->f_pos += offset;
+			if (file->f_pos > flash.read_size)
+				file->f_pos = flash.read_size;
+			break;
+		case 2:
+			file->f_pos = flash.read_size;
+			break;
+		default:
+			mutex_unlock(&flash_mutex);
+			return -EINVAL;
+	}
+	mutex_unlock(&flash_mutex);
+	return file->f_pos;
+}
+
+static ssize_t
+flash_read(struct file * file, char __user * buf,
+	   size_t count, loff_t *ppos)
+{
+	loff_t p = *ppos;
+	int i;
+
+	if (count > flash.read_size - p)
+		count = flash.read_size - p;
+
+	for (i = 0; i < count; i++) {
+		u8 data = upa_readb(flash.read_base + p + i);
+		if (put_user(data, buf))
+			return -EFAULT;
+		buf++;
+	}
+
+	*ppos += count;
+	return count;
+}
+
+static int
+flash_open(struct inode *inode, struct file *file)
+{
+	mutex_lock(&flash_mutex);
+	if (test_and_set_bit(0, (void *)&flash.busy) != 0) {
+		mutex_unlock(&flash_mutex);
+		return -EBUSY;
+	}
+
+	mutex_unlock(&flash_mutex);
+	return 0;
+}
+
+static int
+flash_release(struct inode *inode, struct file *file)
+{
+	spin_lock(&flash_lock);
+	flash.busy = 0;
+	spin_unlock(&flash_lock);
+
+	return 0;
+}
+
+static const struct file_operations flash_fops = {
+	/* no write to the Flash, use mmap
+	 * and play flash dependent tricks.
+	 */
+	.owner =	THIS_MODULE,
+	.llseek =	flash_llseek,
+	.read =		flash_read,
+	.mmap =		flash_mmap,
+	.open =		flash_open,
+	.release =	flash_release,
+};
+
+static struct miscdevice flash_dev = { SBUS_FLASH_MINOR, "flash", &flash_fops };
+
+static int flash_probe(struct platform_device *op)
+{
+	struct device_node *dp = op->dev.of_node;
+	struct device_node *parent;
+
+	parent = dp->parent;
+
+	if (!of_node_name_eq(parent, "sbus") &&
+	    !of_node_name_eq(parent, "sbi") &&
+	    !of_node_name_eq(parent, "ebus"))
+		return -ENODEV;
+
+	flash.read_base = op->resource[0].start;
+	flash.read_size = resource_size(&op->resource[0]);
+	if (op->resource[1].flags) {
+		flash.write_base = op->resource[1].start;
+		flash.write_size = resource_size(&op->resource[1]);
+	} else {
+		flash.write_base = op->resource[0].start;
+		flash.write_size = resource_size(&op->resource[0]);
+	}
+	flash.busy = 0;
+
+	printk(KERN_INFO "%pOF: OBP Flash, RD %lx[%lx] WR %lx[%lx]\n",
+	       op->dev.of_node,
+	       flash.read_base, flash.read_size,
+	       flash.write_base, flash.write_size);
+
+	return misc_register(&flash_dev);
+}
+
+static void flash_remove(struct platform_device *op)
+{
+	misc_deregister(&flash_dev);
+}
+
+static const struct of_device_id flash_match[] = {
+	{
+		.name = "flashprom",
+	},
+	{},
+};
+MODULE_DEVICE_TABLE(of, flash_match);
+
+static struct platform_driver flash_driver = {
+	.driver = {
+		.name = "flash",
+		.of_match_table = flash_match,
+	},
+	.probe		= flash_probe,
+	.remove		= flash_remove,
+};
+
+module_platform_driver(flash_driver);
+
+MODULE_DESCRIPTION("OBP Flash Device driver");
+MODULE_LICENSE("GPL");