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, 50 insertions, 0 deletions

diff --git a/arch/mips/cavium-octeon/cpu.c b/arch/mips/cavium-octeon/cpu.c
new file mode 100644
index 000000000..036d56cc4
--- /dev/null
+++ b/arch/mips/cavium-octeon/cpu.c
@@ -0,0 +1,50 @@
+/*
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * Copyright (C) 2009 Wind River Systems,
+ *   written by Ralf Baechle <ralf@linux-mips.org>
+ */
+#include <linux/init.h>
+#include <linux/irqflags.h>
+#include <linux/notifier.h>
+#include <linux/prefetch.h>
+#include <linux/ptrace.h>
+#include <linux/sched.h>
+#include <linux/sched/task_stack.h>
+
+#include <asm/cop2.h>
+#include <asm/current.h>
+#include <asm/mipsregs.h>
+#include <asm/page.h>
+#include <asm/octeon/octeon.h>
+
+static int cnmips_cu2_call(struct notifier_block *nfb, unsigned long action,
+	void *data)
+{
+	unsigned long flags;
+	unsigned int status;
+
+	switch (action) {
+	case CU2_EXCEPTION:
+		prefetch(&current->thread.cp2);
+		local_irq_save(flags);
+		KSTK_STATUS(current) |= ST0_CU2;
+		status = read_c0_status();
+		write_c0_status(status | ST0_CU2);
+		octeon_cop2_restore(&(current->thread.cp2));
+		write_c0_status(status & ~ST0_CU2);
+		local_irq_restore(flags);
+
+		return NOTIFY_BAD;	/* Don't call default notifier */
+	}
+
+	return NOTIFY_OK;		/* Let default notifier send signals */
+}
+
+static int __init cnmips_cu2_setup(void)
+{
+	return cu2_notifier(cnmips_cu2_call, 0);
+}
+early_initcall(cnmips_cu2_setup);