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, 63 insertions, 0 deletions

diff --git a/arch/powerpc/boot/epapr.c b/arch/powerpc/boot/epapr.c
new file mode 100644
index 000000000..7c5b26ade
--- /dev/null
+++ b/arch/powerpc/boot/epapr.c
@@ -0,0 +1,63 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Bootwrapper for ePAPR compliant firmwares
+ *
+ * Copyright 2010 David Gibson <david@gibson.dropbear.id.au>, IBM Corporation.
+ *
+ * Based on earlier bootwrappers by:
+ * (c) Benjamin Herrenschmidt <benh@kernel.crashing.org>, IBM Corp,\
+ *   and
+ * Scott Wood <scottwood@freescale.com>
+ * Copyright (c) 2007 Freescale Semiconductor, Inc.
+ */
+
+#include "ops.h"
+#include "stdio.h"
+#include "io.h"
+#include <libfdt.h>
+
+BSS_STACK(4096);
+
+#define EPAPR_SMAGIC	0x65504150
+#define EPAPR_EMAGIC	0x45504150
+
+static unsigned epapr_magic;
+static unsigned long ima_size;
+static unsigned long fdt_addr;
+
+static void platform_fixups(void)
+{
+	if ((epapr_magic != EPAPR_EMAGIC)
+	    && (epapr_magic != EPAPR_SMAGIC))
+		fatal("r6 contained 0x%08x instead of ePAPR magic number\n",
+		      epapr_magic);
+
+	if (ima_size < (unsigned long)_end)
+		printf("WARNING: Image loaded outside IMA!"
+		       " (_end=%p, ima_size=0x%lx)\n", _end, ima_size);
+	if (ima_size < fdt_addr)
+		printf("WARNING: Device tree address is outside IMA!"
+		       "(fdt_addr=0x%lx, ima_size=0x%lx)\n", fdt_addr,
+		       ima_size);
+	if (ima_size < fdt_addr + fdt_totalsize((void *)fdt_addr))
+		printf("WARNING: Device tree extends outside IMA!"
+		       " (fdt_addr=0x%lx, size=0x%x, ima_size=0x%lx\n",
+		       fdt_addr, fdt_totalsize((void *)fdt_addr), ima_size);
+}
+
+void epapr_platform_init(unsigned long r3, unsigned long r4, unsigned long r5,
+			 unsigned long r6, unsigned long r7)
+{
+	epapr_magic = r6;
+	ima_size = r7;
+	fdt_addr = r3;
+
+	/* FIXME: we should process reserve entries */
+
+	simple_alloc_init(_end, ima_size - (unsigned long)_end, 32, 64);
+
+	fdt_init((void *)fdt_addr);
+
+	serial_console_init();
+	platform_ops.fixups = platform_fixups;
+}