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, 132 insertions, 0 deletions

diff --git a/drivers/mtd/maps/physmap-ixp4xx.c b/drivers/mtd/maps/physmap-ixp4xx.c
new file mode 100644
index 000000000..c561468f9
--- /dev/null
+++ b/drivers/mtd/maps/physmap-ixp4xx.c
@@ -0,0 +1,132 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Intel IXP4xx OF physmap add-on
+ * Copyright (C) 2019 Linus Walleij <linus.walleij@linaro.org>
+ *
+ * Based on the ixp4xx.c map driver, originally written by:
+ * Intel Corporation
+ * Deepak Saxena <dsaxena@mvista.com>
+ * Copyright (C) 2002 Intel Corporation
+ * Copyright (C) 2003-2004 MontaVista Software, Inc.
+ */
+#include <linux/export.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/mtd/map.h>
+#include <linux/mtd/xip.h>
+#include "physmap-ixp4xx.h"
+
+/*
+ * Read/write a 16 bit word from flash address 'addr'.
+ *
+ * When the cpu is in little-endian mode it swizzles the address lines
+ * ('address coherency') so we need to undo the swizzling to ensure commands
+ * and the like end up on the correct flash address.
+ *
+ * To further complicate matters, due to the way the expansion bus controller
+ * handles 32 bit reads, the byte stream ABCD is stored on the flash as:
+ *     D15    D0
+ *     +---+---+
+ *     | A | B | 0
+ *     +---+---+
+ *     | C | D | 2
+ *     +---+---+
+ * This means that on LE systems each 16 bit word must be swapped. Note that
+ * this requires CONFIG_MTD_CFI_BE_BYTE_SWAP to be enabled to 'unswap' the CFI
+ * data and other flash commands which are always in D7-D0.
+ */
+#ifndef CONFIG_CPU_BIG_ENDIAN
+
+static inline u16 flash_read16(void __iomem *addr)
+{
+	return be16_to_cpu(__raw_readw((void __iomem *)((unsigned long)addr ^ 0x2)));
+}
+
+static inline void flash_write16(u16 d, void __iomem *addr)
+{
+	__raw_writew(cpu_to_be16(d), (void __iomem *)((unsigned long)addr ^ 0x2));
+}
+
+#define	BYTE0(h)	((h) & 0xFF)
+#define	BYTE1(h)	(((h) >> 8) & 0xFF)
+
+#else
+
+static inline u16 flash_read16(const void __iomem *addr)
+{
+	return __raw_readw(addr);
+}
+
+static inline void flash_write16(u16 d, void __iomem *addr)
+{
+	__raw_writew(d, addr);
+}
+
+#define	BYTE0(h)	(((h) >> 8) & 0xFF)
+#define	BYTE1(h)	((h) & 0xFF)
+#endif
+
+static map_word ixp4xx_read16(struct map_info *map, unsigned long ofs)
+{
+	map_word val;
+
+	val.x[0] = flash_read16(map->virt + ofs);
+	return val;
+}
+
+/*
+ * The IXP4xx expansion bus only allows 16-bit wide acceses
+ * when attached to a 16-bit wide device (such as the 28F128J3A),
+ * so we can't just memcpy_fromio().
+ */
+static void ixp4xx_copy_from(struct map_info *map, void *to,
+			     unsigned long from, ssize_t len)
+{
+	u8 *dest = (u8 *) to;
+	void __iomem *src = map->virt + from;
+
+	if (len <= 0)
+		return;
+
+	if (from & 1) {
+		*dest++ = BYTE1(flash_read16(src-1));
+		src++;
+		--len;
+	}
+
+	while (len >= 2) {
+		u16 data = flash_read16(src);
+		*dest++ = BYTE0(data);
+		*dest++ = BYTE1(data);
+		src += 2;
+		len -= 2;
+	}
+
+	if (len > 0)
+		*dest++ = BYTE0(flash_read16(src));
+}
+
+static void ixp4xx_write16(struct map_info *map, map_word d, unsigned long adr)
+{
+	flash_write16(d.x[0], map->virt + adr);
+}
+
+int of_flash_probe_ixp4xx(struct platform_device *pdev,
+			  struct device_node *np,
+			  struct map_info *map)
+{
+	struct device *dev = &pdev->dev;
+
+	/* Multiplatform guard */
+	if (!of_device_is_compatible(np, "intel,ixp4xx-flash"))
+		return 0;
+
+	map->read = ixp4xx_read16;
+	map->write = ixp4xx_write16;
+	map->copy_from = ixp4xx_copy_from;
+	map->copy_to = NULL;
+
+	dev_info(dev, "initialized Intel IXP4xx-specific physmap control\n");
+
+	return 0;
+}