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, 87 insertions, 0 deletions

diff --git a/arch/powerpc/boot/simpleboot.c b/arch/powerpc/boot/simpleboot.c
new file mode 100644
index 000000000..27591df41
--- /dev/null
+++ b/arch/powerpc/boot/simpleboot.c
@@ -0,0 +1,87 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * The simple platform -- for booting when firmware doesn't supply a device
+ *                        tree or any platform configuration information.
+ *                        All data is extracted from an embedded device tree
+ *                        blob.
+ *
+ * Authors: Scott Wood <scottwood@freescale.com>
+ *          Grant Likely <grant.likely@secretlab.ca>
+ *
+ * Copyright (c) 2007 Freescale Semiconductor, Inc.
+ * Copyright (c) 2008 Secret Lab Technologies Ltd.
+ */
+
+#include "ops.h"
+#include "types.h"
+#include "io.h"
+#include "stdio.h"
+#include <libfdt.h>
+
+BSS_STACK(4*1024);
+
+extern int platform_specific_init(void) __attribute__((weak));
+
+void platform_init(unsigned long r3, unsigned long r4, unsigned long r5,
+		   unsigned long r6, unsigned long r7)
+{
+	const u32 *na, *ns, *reg, *timebase;
+	u64 memsize64;
+	int node, size, i;
+
+	/* Make sure FDT blob is sane */
+	if (fdt_check_header(_dtb_start) != 0)
+		fatal("Invalid device tree blob\n");
+
+	/* Find the #address-cells and #size-cells properties */
+	node = fdt_path_offset(_dtb_start, "/");
+	if (node < 0)
+		fatal("Cannot find root node\n");
+	na = fdt_getprop(_dtb_start, node, "#address-cells", &size);
+	if (!na || (size != 4))
+		fatal("Cannot find #address-cells property");
+	ns = fdt_getprop(_dtb_start, node, "#size-cells", &size);
+	if (!ns || (size != 4))
+		fatal("Cannot find #size-cells property");
+
+	/* Find the memory range */
+	node = fdt_node_offset_by_prop_value(_dtb_start, -1, "device_type",
+					     "memory", sizeof("memory"));
+	if (node < 0)
+		fatal("Cannot find memory node\n");
+	reg = fdt_getprop(_dtb_start, node, "reg", &size);
+	if (size < (*na+*ns) * sizeof(u32))
+		fatal("cannot get memory range\n");
+
+	/* Only interested in memory based at 0 */
+	for (i = 0; i < *na; i++)
+		if (*reg++ != 0)
+			fatal("Memory range is not based at address 0\n");
+
+	/* get the memsize and truncate it to under 4G on 32 bit machines */
+	memsize64 = 0;
+	for (i = 0; i < *ns; i++)
+		memsize64 = (memsize64 << 32) | *reg++;
+	if (sizeof(void *) == 4 && memsize64 >= 0x100000000ULL)
+		memsize64 = 0xffffffff;
+
+	/* finally, setup the timebase */
+	node = fdt_node_offset_by_prop_value(_dtb_start, -1, "device_type",
+					     "cpu", sizeof("cpu"));
+	if (node < 0)
+		fatal("Cannot find cpu node\n");
+	timebase = fdt_getprop(_dtb_start, node, "timebase-frequency", &size);
+	if (timebase && (size == 4))
+		timebase_period_ns = 1000000000 / *timebase;
+
+	/* Now we have the memory size; initialize the heap */
+	simple_alloc_init(_end, memsize64 - (unsigned long)_end, 32, 64);
+
+	/* prepare the device tree and find the console */
+	fdt_init(_dtb_start);
+
+	if (platform_specific_init)
+		platform_specific_init();
+
+	serial_console_init();
+}