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>

4 files changed, 225 insertions, 0 deletions

diff --git a/tools/lib/symbol/Build b/tools/lib/symbol/Build
new file mode 100644
index 000000000..9b9a9c78d
--- /dev/null
+++ b/tools/lib/symbol/Build
@@ -0,0 +1 @@
+libsymbol-y += kallsyms.o
diff --git a/tools/lib/symbol/Makefile b/tools/lib/symbol/Makefile
new file mode 100644
index 000000000..d692abe8a
--- /dev/null
+++ b/tools/lib/symbol/Makefile
@@ -0,0 +1,114 @@
+# SPDX-License-Identifier: GPL-2.0
+include ../../scripts/Makefile.include
+include ../../scripts/utilities.mak		# QUIET_CLEAN
+
+ifeq ($(srctree),)
+srctree := $(patsubst %/,%,$(dir $(CURDIR)))
+srctree := $(patsubst %/,%,$(dir $(srctree)))
+srctree := $(patsubst %/,%,$(dir $(srctree)))
+#$(info Determined 'srctree' to be $(srctree))
+endif
+
+MAKEFLAGS += --no-print-directory
+
+INSTALL = install
+
+
+# Use DESTDIR for installing into a different root directory.
+# This is useful for building a package. The program will be
+# installed in this directory as if it was the root directory.
+# Then the build tool can move it later.
+DESTDIR ?=
+DESTDIR_SQ = '$(subst ','\'',$(DESTDIR))'
+
+LIBFILE = $(OUTPUT)libsymbol.a
+
+CFLAGS := $(EXTRA_WARNINGS) $(EXTRA_CFLAGS)
+CFLAGS += -ggdb3 -Wall -Wextra -std=gnu11 -U_FORTIFY_SOURCE -fPIC
+
+ifeq ($(DEBUG),0)
+  CFLAGS += -O3
+endif
+
+ifeq ($(DEBUG),0)
+  CFLAGS += -D_FORTIFY_SOURCE
+endif
+
+# Treat warnings as errors unless directed not to
+ifneq ($(WERROR),0)
+  CFLAGS += -Werror
+endif
+
+CFLAGS += -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64
+
+CFLAGS += -I$(srctree)/tools/lib
+CFLAGS += -I$(srctree)/tools/include
+
+RM = rm -f
+
+SYMBOL_IN := $(OUTPUT)libsymbol-in.o
+
+ifeq ($(LP64), 1)
+  libdir_relative = lib64
+else
+  libdir_relative = lib
+endif
+
+prefix ?=
+libdir = $(prefix)/$(libdir_relative)
+
+# Shell quotes
+libdir_SQ = $(subst ','\'',$(libdir))
+
+all:
+
+export srctree OUTPUT CC LD CFLAGS V
+include $(srctree)/tools/build/Makefile.include
+include $(srctree)/tools/scripts/Makefile.include
+
+all: fixdep $(LIBFILE)
+
+$(SYMBOL_IN): FORCE
+	@$(MAKE) $(build)=libsymbol
+
+$(LIBFILE): $(SYMBOL_IN)
+	$(QUIET_AR)$(RM) $@ && $(AR) rcs $@ $(SYMBOL_IN)
+
+define do_install_mkdir
+	if [ ! -d '$(DESTDIR_SQ)$1' ]; then             \
+		$(INSTALL) -d -m 755 '$(DESTDIR_SQ)$1'; \
+	fi
+endef
+
+define do_install
+	if [ ! -d '$2' ]; then             \
+		$(INSTALL) -d -m 755 '$2'; \
+	fi;                                \
+	$(INSTALL) $1 $(if $3,-m $3,) '$2'
+endef
+
+install_lib: $(LIBFILE)
+	$(call QUIET_INSTALL, $(LIBFILE)) \
+		$(call do_install_mkdir,$(libdir_SQ)); \
+		cp -fpR $(LIBFILE) $(DESTDIR)$(libdir_SQ)
+
+HDRS := kallsyms.h
+INSTALL_HDRS_PFX := $(DESTDIR)$(prefix)/include/symbol
+INSTALL_HDRS := $(addprefix $(INSTALL_HDRS_PFX)/, $(HDRS))
+
+$(INSTALL_HDRS): $(INSTALL_HDRS_PFX)/%.h: %.h
+	$(call QUIET_INSTALL, $@) \
+		$(call do_install,$<,$(INSTALL_HDRS_PFX)/,644)
+
+install_headers: $(INSTALL_HDRS)
+	$(call QUIET_INSTALL, libsymbol_headers)
+
+install: install_lib install_headers
+
+clean:
+	$(call QUIET_CLEAN, libsymbol) $(RM) $(LIBFILE); \
+	find $(or $(OUTPUT),.) -name \*.o -or -name \*.o.cmd -or -name \*.o.d | xargs $(RM)
+
+FORCE:
+
+.PHONY: clean FORCE
diff --git a/tools/lib/symbol/kallsyms.c b/tools/lib/symbol/kallsyms.c
new file mode 100644
index 000000000..d64bd9cc8
--- /dev/null
+++ b/tools/lib/symbol/kallsyms.c
@@ -0,0 +1,81 @@
+// SPDX-License-Identifier: GPL-2.0
+#include "symbol/kallsyms.h"
+#include "api/io.h"
+#include <stdio.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+
+u8 kallsyms2elf_type(char type)
+{
+	type = tolower(type);
+	return (type == 't' || type == 'w') ? STT_FUNC : STT_OBJECT;
+}
+
+bool kallsyms__is_function(char symbol_type)
+{
+	symbol_type = toupper(symbol_type);
+	return symbol_type == 'T' || symbol_type == 'W';
+}
+
+static void read_to_eol(struct io *io)
+{
+	int ch;
+
+	for (;;) {
+		ch = io__get_char(io);
+		if (ch < 0 || ch == '\n')
+			return;
+	}
+}
+
+int kallsyms__parse(const char *filename, void *arg,
+		    int (*process_symbol)(void *arg, const char *name,
+					  char type, u64 start))
+{
+	struct io io;
+	char bf[BUFSIZ];
+	int err;
+
+	io.fd = open(filename, O_RDONLY, 0);
+
+	if (io.fd < 0)
+		return -1;
+
+	io__init(&io, io.fd, bf, sizeof(bf));
+
+	err = 0;
+	while (!io.eof) {
+		__u64 start;
+		int ch;
+		size_t i;
+		char symbol_type;
+		char symbol_name[KSYM_NAME_LEN + 1];
+
+		if (io__get_hex(&io, &start) != ' ') {
+			read_to_eol(&io);
+			continue;
+		}
+		symbol_type = io__get_char(&io);
+		if (io__get_char(&io) != ' ') {
+			read_to_eol(&io);
+			continue;
+		}
+		for (i = 0; i < KSYM_NAME_LEN; i++) {
+			ch = io__get_char(&io);
+			if (ch < 0 || ch == '\n')
+				break;
+			symbol_name[i]  = ch;
+		}
+		symbol_name[i]  = '\0';
+
+		if (i == KSYM_NAME_LEN)
+			read_to_eol(&io);
+
+		err = process_symbol(arg, symbol_name, symbol_type, start);
+		if (err)
+			break;
+	}
+
+	close(io.fd);
+	return err;
+}
diff --git a/tools/lib/symbol/kallsyms.h b/tools/lib/symbol/kallsyms.h
new file mode 100644
index 000000000..542f9b059
--- /dev/null
+++ b/tools/lib/symbol/kallsyms.h
@@ -0,0 +1,29 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __TOOLS_KALLSYMS_H_
+#define __TOOLS_KALLSYMS_H_ 1
+
+#include <elf.h>
+#include <linux/ctype.h>
+#include <linux/types.h>
+
+#ifndef KSYM_NAME_LEN
+#define KSYM_NAME_LEN 512
+#endif
+
+static inline u8 kallsyms2elf_binding(char type)
+{
+	if (type == 'W')
+		return STB_WEAK;
+
+	return isupper(type) ? STB_GLOBAL : STB_LOCAL;
+}
+
+u8 kallsyms2elf_type(char type);
+
+bool kallsyms__is_function(char symbol_type);
+
+int kallsyms__parse(const char *filename, void *arg,
+		    int (*process_symbol)(void *arg, const char *name,
+					  char type, u64 start));
+
+#endif /* __TOOLS_KALLSYMS_H_ */