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, 185 insertions, 0 deletions

diff --git a/arch/powerpc/boot/libfdt-wrapper.c b/arch/powerpc/boot/libfdt-wrapper.c
new file mode 100644
index 000000000..217d0d7a6
--- /dev/null
+++ b/arch/powerpc/boot/libfdt-wrapper.c
@@ -0,0 +1,185 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * This file does the necessary interface mapping between the bootwrapper
+ * device tree operations and the interface provided by shared source
+ * files flatdevicetree.[ch].
+ *
+ * Copyright 2007 David Gibson, IBM Corporation.
+ */
+
+#include <stddef.h>
+#include <stdio.h>
+#include <page.h>
+#include <libfdt.h>
+#include "ops.h"
+
+#define DEBUG	0
+#define BAD_ERROR(err)	(((err) < 0) \
+			 && ((err) != -FDT_ERR_NOTFOUND) \
+			 && ((err) != -FDT_ERR_EXISTS))
+
+#define check_err(err) \
+	({ \
+		if (BAD_ERROR(err) || ((err < 0) && DEBUG)) \
+			printf("%s():%d  %s\n\r", __func__, __LINE__, \
+			       fdt_strerror(err)); \
+		if (BAD_ERROR(err)) \
+			exit(); \
+		(err < 0) ? -1 : 0; \
+	})
+
+#define offset_devp(off)	\
+	({ \
+		unsigned long _offset = (off); \
+		check_err(_offset) ? NULL : (void *)(_offset+1); \
+	})
+
+#define devp_offset_find(devp)	(((unsigned long)(devp))-1)
+#define devp_offset(devp)	(devp ? ((unsigned long)(devp))-1 : 0)
+
+static void *fdt;
+static void *buf; /* = NULL */
+
+#define EXPAND_GRANULARITY	1024
+
+static void expand_buf(int minexpand)
+{
+	int size = fdt_totalsize(fdt);
+	int rc;
+
+	size = _ALIGN(size + minexpand, EXPAND_GRANULARITY);
+	buf = platform_ops.realloc(buf, size);
+	if (!buf)
+		fatal("Couldn't find %d bytes to expand device tree\n\r", size);
+	rc = fdt_open_into(fdt, buf, size);
+	if (rc != 0)
+		fatal("Couldn't expand fdt into new buffer: %s\n\r",
+		      fdt_strerror(rc));
+
+	fdt = buf;
+}
+
+static void *fdt_wrapper_finddevice(const char *path)
+{
+	return offset_devp(fdt_path_offset(fdt, path));
+}
+
+static int fdt_wrapper_getprop(const void *devp, const char *name,
+			       void *buf, const int buflen)
+{
+	const void *p;
+	int len;
+
+	p = fdt_getprop(fdt, devp_offset(devp), name, &len);
+	if (!p)
+		return check_err(len);
+	memcpy(buf, p, min(len, buflen));
+	return len;
+}
+
+static int fdt_wrapper_setprop(const void *devp, const char *name,
+			       const void *buf, const int len)
+{
+	int rc;
+
+	rc = fdt_setprop(fdt, devp_offset(devp), name, buf, len);
+	if (rc == -FDT_ERR_NOSPACE) {
+		expand_buf(len + 16);
+		rc = fdt_setprop(fdt, devp_offset(devp), name, buf, len);
+	}
+
+	return check_err(rc);
+}
+
+static int fdt_wrapper_del_node(const void *devp)
+{
+	return fdt_del_node(fdt, devp_offset(devp));
+}
+
+static void *fdt_wrapper_get_parent(const void *devp)
+{
+	return offset_devp(fdt_parent_offset(fdt, devp_offset(devp)));
+}
+
+static void *fdt_wrapper_create_node(const void *devp, const char *name)
+{
+	int offset;
+
+	offset = fdt_add_subnode(fdt, devp_offset(devp), name);
+	if (offset == -FDT_ERR_NOSPACE) {
+		expand_buf(strlen(name) + 16);
+		offset = fdt_add_subnode(fdt, devp_offset(devp), name);
+	}
+
+	return offset_devp(offset);
+}
+
+static void *fdt_wrapper_find_node_by_prop_value(const void *prev,
+						 const char *name,
+						 const char *val,
+						 int len)
+{
+	int offset = fdt_node_offset_by_prop_value(fdt, devp_offset_find(prev),
+	                                           name, val, len);
+	return offset_devp(offset);
+}
+
+static void *fdt_wrapper_find_node_by_compatible(const void *prev,
+						 const char *val)
+{
+	int offset = fdt_node_offset_by_compatible(fdt, devp_offset_find(prev),
+	                                           val);
+	return offset_devp(offset);
+}
+
+static char *fdt_wrapper_get_path(const void *devp, char *buf, int len)
+{
+	int rc;
+
+	rc = fdt_get_path(fdt, devp_offset(devp), buf, len);
+	if (check_err(rc))
+		return NULL;
+	return buf;
+}
+
+static unsigned long fdt_wrapper_finalize(void)
+{
+	int rc;
+
+	rc = fdt_pack(fdt);
+	if (rc != 0)
+		fatal("Couldn't pack flat tree: %s\n\r",
+		      fdt_strerror(rc));
+	return (unsigned long)fdt;
+}
+
+void fdt_init(void *blob)
+{
+	int err;
+	int bufsize;
+
+	dt_ops.finddevice = fdt_wrapper_finddevice;
+	dt_ops.getprop = fdt_wrapper_getprop;
+	dt_ops.setprop = fdt_wrapper_setprop;
+	dt_ops.get_parent = fdt_wrapper_get_parent;
+	dt_ops.create_node = fdt_wrapper_create_node;
+	dt_ops.find_node_by_prop_value = fdt_wrapper_find_node_by_prop_value;
+	dt_ops.find_node_by_compatible = fdt_wrapper_find_node_by_compatible;
+	dt_ops.del_node = fdt_wrapper_del_node;
+	dt_ops.get_path = fdt_wrapper_get_path;
+	dt_ops.finalize = fdt_wrapper_finalize;
+
+	/* Make sure the dt blob is the right version and so forth */
+	fdt = blob;
+	bufsize = fdt_totalsize(fdt) + EXPAND_GRANULARITY;
+	buf = malloc(bufsize);
+	if(!buf)
+		fatal("malloc failed. can't relocate the device tree\n\r");
+
+	err = fdt_open_into(fdt, buf, bufsize);
+
+	if (err != 0)
+		fatal("fdt_init(): %s\n\r", fdt_strerror(err));
+
+	fdt = buf;
+}