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, 170 insertions, 0 deletions

diff --git a/tools/build/fixdep.c b/tools/build/fixdep.c
new file mode 100644
index 000000000..2501fea7a
--- /dev/null
+++ b/tools/build/fixdep.c
@@ -0,0 +1,170 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * "Optimize" a list of dependencies as spit out by gcc -MD
+ * for the build framework.
+ *
+ * Original author:
+ *   Copyright    2002 by Kai Germaschewski  <kai.germaschewski@gmx.de>
+ *
+ * This code has been borrowed from kbuild's fixdep (scripts/basic/fixdep.c),
+ * Please check it for detailed explanation. This fixdep borow only the
+ * base transformation of dependecies without the CONFIG mangle.
+ */
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/mman.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <string.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <limits.h>
+
+char *target;
+char *depfile;
+char *cmdline;
+
+static void usage(void)
+{
+	fprintf(stderr, "Usage: fixdep <depfile> <target> <cmdline>\n");
+	exit(1);
+}
+
+/*
+ * Print out the commandline prefixed with cmd_<target filename> :=
+ */
+static void print_cmdline(void)
+{
+	printf("cmd_%s := %s\n\n", target, cmdline);
+}
+
+/*
+ * Important: The below generated source_foo.o and deps_foo.o variable
+ * assignments are parsed not only by make, but also by the rather simple
+ * parser in scripts/mod/sumversion.c.
+ */
+static void parse_dep_file(void *map, size_t len)
+{
+	char *m = map;
+	char *end = m + len;
+	char *p;
+	char s[PATH_MAX];
+	int is_target, has_target = 0;
+	int saw_any_target = 0;
+	int is_first_dep = 0;
+
+	while (m < end) {
+		/* Skip any "white space" */
+		while (m < end && (*m == ' ' || *m == '\\' || *m == '\n'))
+			m++;
+		/* Find next "white space" */
+		p = m;
+		while (p < end && *p != ' ' && *p != '\\' && *p != '\n')
+			p++;
+		/* Is the token we found a target name? */
+		is_target = (*(p-1) == ':');
+		/* Don't write any target names into the dependency file */
+		if (is_target) {
+			/* The /next/ file is the first dependency */
+			is_first_dep = 1;
+			has_target = 1;
+		} else if (has_target) {
+			/* Save this token/filename */
+			memcpy(s, m, p-m);
+			s[p - m] = 0;
+
+			/*
+			 * Do not list the source file as dependency,
+			 * so that kbuild is not confused if a .c file
+			 * is rewritten into .S or vice versa. Storing
+			 * it in source_* is needed for modpost to
+			 * compute srcversions.
+			 */
+			if (is_first_dep) {
+				/*
+				 * If processing the concatenation of
+				 * multiple dependency files, only
+				 * process the first target name, which
+				 * will be the original source name,
+				 * and ignore any other target names,
+				 * which will be intermediate temporary
+				 * files.
+				 */
+				if (!saw_any_target) {
+					saw_any_target = 1;
+					printf("source_%s := %s\n\n",
+						target, s);
+					printf("deps_%s := \\\n",
+						target);
+				}
+				is_first_dep = 0;
+			} else
+				printf("  %s \\\n", s);
+		}
+		/*
+		 * Start searching for next token immediately after the first
+		 * "whitespace" character that follows this token.
+		 */
+		m = p + 1;
+	}
+
+	if (!saw_any_target) {
+		fprintf(stderr, "fixdep: parse error; no targets found\n");
+		exit(1);
+	}
+
+	printf("\n%s: $(deps_%s)\n\n", target, target);
+	printf("$(deps_%s):\n", target);
+}
+
+static void print_deps(void)
+{
+	struct stat st;
+	int fd;
+	void *map;
+
+	fd = open(depfile, O_RDONLY);
+	if (fd < 0) {
+		fprintf(stderr, "fixdep: error opening depfile: ");
+		perror(depfile);
+		exit(2);
+	}
+	if (fstat(fd, &st) < 0) {
+		fprintf(stderr, "fixdep: error fstat'ing depfile: ");
+		perror(depfile);
+		exit(2);
+	}
+	if (st.st_size == 0) {
+		fprintf(stderr, "fixdep: %s is empty\n", depfile);
+		close(fd);
+		return;
+	}
+	map = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
+	if ((long) map == -1) {
+		perror("fixdep: mmap");
+		close(fd);
+		return;
+	}
+
+	parse_dep_file(map, st.st_size);
+
+	munmap(map, st.st_size);
+
+	close(fd);
+}
+
+int main(int argc, char **argv)
+{
+	if (argc != 4)
+		usage();
+
+	depfile = argv[1];
+	target  = argv[2];
+	cmdline = argv[3];
+
+	print_cmdline();
+	print_deps();
+
+	return 0;
+}