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, 232 insertions, 0 deletions

diff --git a/drivers/char/adi.c b/drivers/char/adi.c
new file mode 100644
index 000000000..0849d933a
--- /dev/null
+++ b/drivers/char/adi.c
@@ -0,0 +1,232 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Privileged ADI driver for sparc64
+ *
+ * Author: Tom Hromatka <tom.hromatka@oracle.com>
+ */
+#include <linux/kernel.h>
+#include <linux/miscdevice.h>
+#include <linux/module.h>
+#include <linux/proc_fs.h>
+#include <linux/slab.h>
+#include <linux/uaccess.h>
+#include <asm/asi.h>
+
+#define MAX_BUF_SZ	PAGE_SIZE
+
+static int read_mcd_tag(unsigned long addr)
+{
+	long err;
+	int ver;
+
+	__asm__ __volatile__(
+		"1:	ldxa [%[addr]] %[asi], %[ver]\n"
+		"	mov 0, %[err]\n"
+		"2:\n"
+		"	.section .fixup,#alloc,#execinstr\n"
+		"	.align 4\n"
+		"3:	sethi %%hi(2b), %%g1\n"
+		"	jmpl  %%g1 + %%lo(2b), %%g0\n"
+		"	mov %[invalid], %[err]\n"
+		"	.previous\n"
+		"	.section __ex_table, \"a\"\n"
+		"	.align 4\n"
+		"	.word  1b, 3b\n"
+		"	.previous\n"
+		: [ver] "=r" (ver), [err] "=r" (err)
+		: [addr] "r"  (addr), [invalid] "i" (EFAULT),
+		  [asi] "i" (ASI_MCD_REAL)
+		: "memory", "g1"
+		);
+
+	if (err)
+		return -EFAULT;
+	else
+		return ver;
+}
+
+static ssize_t adi_read(struct file *file, char __user *buf,
+			size_t count, loff_t *offp)
+{
+	size_t ver_buf_sz, bytes_read = 0;
+	int ver_buf_idx = 0;
+	loff_t offset;
+	u8 *ver_buf;
+	ssize_t ret;
+
+	ver_buf_sz = min_t(size_t, count, MAX_BUF_SZ);
+	ver_buf = kmalloc(ver_buf_sz, GFP_KERNEL);
+	if (!ver_buf)
+		return -ENOMEM;
+
+	offset = (*offp) * adi_blksize();
+
+	while (bytes_read < count) {
+		ret = read_mcd_tag(offset);
+		if (ret < 0)
+			goto out;
+
+		ver_buf[ver_buf_idx] = (u8)ret;
+		ver_buf_idx++;
+		offset += adi_blksize();
+
+		if (ver_buf_idx >= ver_buf_sz) {
+			if (copy_to_user(buf + bytes_read, ver_buf,
+					 ver_buf_sz)) {
+				ret = -EFAULT;
+				goto out;
+			}
+
+			bytes_read += ver_buf_sz;
+			ver_buf_idx = 0;
+
+			ver_buf_sz = min_t(size_t, count - bytes_read,
+					   MAX_BUF_SZ);
+		}
+	}
+
+	(*offp) += bytes_read;
+	ret = bytes_read;
+out:
+	kfree(ver_buf);
+	return ret;
+}
+
+static int set_mcd_tag(unsigned long addr, u8 ver)
+{
+	long err;
+
+	__asm__ __volatile__(
+		"1:	stxa %[ver], [%[addr]] %[asi]\n"
+		"	mov 0, %[err]\n"
+		"2:\n"
+		"	.section .fixup,#alloc,#execinstr\n"
+		"	.align 4\n"
+		"3:	sethi %%hi(2b), %%g1\n"
+		"	jmpl %%g1 + %%lo(2b), %%g0\n"
+		"	mov %[invalid], %[err]\n"
+		"	.previous\n"
+		"	.section __ex_table, \"a\"\n"
+		"	.align 4\n"
+		"	.word 1b, 3b\n"
+		"	.previous\n"
+		: [err] "=r" (err)
+		: [ver] "r" (ver), [addr] "r"  (addr),
+		  [invalid] "i" (EFAULT), [asi] "i" (ASI_MCD_REAL)
+		: "memory", "g1"
+		);
+
+	if (err)
+		return -EFAULT;
+	else
+		return ver;
+}
+
+static ssize_t adi_write(struct file *file, const char __user *buf,
+			 size_t count, loff_t *offp)
+{
+	size_t ver_buf_sz, bytes_written = 0;
+	loff_t offset;
+	u8 *ver_buf;
+	ssize_t ret;
+	int i;
+
+	if (count == 0)
+		return -EINVAL;
+
+	ver_buf_sz = min_t(size_t, count, MAX_BUF_SZ);
+	ver_buf = kmalloc(ver_buf_sz, GFP_KERNEL);
+	if (!ver_buf)
+		return -ENOMEM;
+
+	offset = (*offp) * adi_blksize();
+
+	do {
+		if (copy_from_user(ver_buf, &buf[bytes_written],
+				   ver_buf_sz)) {
+			ret = -EFAULT;
+			goto out;
+		}
+
+		for (i = 0; i < ver_buf_sz; i++) {
+			ret = set_mcd_tag(offset, ver_buf[i]);
+			if (ret < 0)
+				goto out;
+
+			offset += adi_blksize();
+		}
+
+		bytes_written += ver_buf_sz;
+		ver_buf_sz = min_t(size_t, count - bytes_written, MAX_BUF_SZ);
+	} while (bytes_written < count);
+
+	(*offp) += bytes_written;
+	ret = bytes_written;
+out:
+	__asm__ __volatile__("membar #Sync");
+	kfree(ver_buf);
+	return ret;
+}
+
+static loff_t adi_llseek(struct file *file, loff_t offset, int whence)
+{
+	loff_t ret = -EINVAL;
+
+	switch (whence) {
+	case SEEK_END:
+	case SEEK_DATA:
+	case SEEK_HOLE:
+		/* unsupported */
+		return -EINVAL;
+	case SEEK_CUR:
+		if (offset == 0)
+			return file->f_pos;
+
+		offset += file->f_pos;
+		break;
+	case SEEK_SET:
+		break;
+	}
+
+	if (offset != file->f_pos) {
+		file->f_pos = offset;
+		ret = offset;
+	}
+
+	return ret;
+}
+
+static const struct file_operations adi_fops = {
+	.owner		= THIS_MODULE,
+	.llseek		= adi_llseek,
+	.read		= adi_read,
+	.write		= adi_write,
+	.fop_flags	= FOP_UNSIGNED_OFFSET,
+};
+
+static struct miscdevice adi_miscdev = {
+	.minor = MISC_DYNAMIC_MINOR,
+	.name = KBUILD_MODNAME,
+	.fops = &adi_fops,
+};
+
+static int __init adi_init(void)
+{
+	if (!adi_capable())
+		return -EPERM;
+
+	return misc_register(&adi_miscdev);
+}
+
+static void __exit adi_exit(void)
+{
+	misc_deregister(&adi_miscdev);
+}
+
+module_init(adi_init);
+module_exit(adi_exit);
+
+MODULE_AUTHOR("Tom Hromatka <tom.hromatka@oracle.com>");
+MODULE_DESCRIPTION("Privileged interface to ADI");
+MODULE_VERSION("1.0");
+MODULE_LICENSE("GPL v2");