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, 69 insertions, 0 deletions

diff --git a/rust/helpers/bitops.c b/rust/helpers/bitops.c
new file mode 100644
index 000000000..271b8a712
--- /dev/null
+++ b/rust/helpers/bitops.c
@@ -0,0 +1,69 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/bitops.h>
+#include <linux/find.h>
+
+__rust_helper
+void rust_helper___set_bit(unsigned long nr, unsigned long *addr)
+{
+	__set_bit(nr, addr);
+}
+
+__rust_helper
+void rust_helper___clear_bit(unsigned long nr, unsigned long *addr)
+{
+	__clear_bit(nr, addr);
+}
+
+__rust_helper
+void rust_helper_set_bit(unsigned long nr, volatile unsigned long *addr)
+{
+	set_bit(nr, addr);
+}
+
+__rust_helper
+void rust_helper_clear_bit(unsigned long nr, volatile unsigned long *addr)
+{
+	clear_bit(nr, addr);
+}
+
+/*
+ * The rust_helper_ prefix is intentionally omitted below so that the
+ * declarations in include/linux/find.h are compatible with these helpers.
+ *
+ * Note that the below #ifdefs mean that the helper is only created if C does
+ * not provide a definition.
+ */
+#ifdef find_first_zero_bit
+__rust_helper
+unsigned long _find_first_zero_bit(const unsigned long *p, unsigned long size)
+{
+	return find_first_zero_bit(p, size);
+}
+#endif /* find_first_zero_bit */
+
+#ifdef find_next_zero_bit
+__rust_helper
+unsigned long _find_next_zero_bit(const unsigned long *addr,
+				  unsigned long size, unsigned long offset)
+{
+	return find_next_zero_bit(addr, size, offset);
+}
+#endif /* find_next_zero_bit */
+
+#ifdef find_first_bit
+__rust_helper
+unsigned long _find_first_bit(const unsigned long *addr, unsigned long size)
+{
+	return find_first_bit(addr, size);
+}
+#endif /* find_first_bit */
+
+#ifdef find_next_bit
+__rust_helper
+unsigned long _find_next_bit(const unsigned long *addr, unsigned long size,
+			     unsigned long offset)
+{
+	return find_next_bit(addr, size, offset);
+}
+#endif /* find_next_bit */