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, 93 insertions, 0 deletions

diff --git a/arch/powerpc/boot/of.c b/arch/powerpc/boot/of.c
new file mode 100644
index 000000000..2fbd4ae60
--- /dev/null
+++ b/arch/powerpc/boot/of.c
@@ -0,0 +1,93 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) Paul Mackerras 1997.
+ */
+#include <stdarg.h>
+#include <stddef.h>
+#include "types.h"
+#include "elf.h"
+#include "string.h"
+#include "stdio.h"
+#include "page.h"
+#include "ops.h"
+
+#include "of.h"
+
+/* Value picked to match that used by yaboot */
+#define PROG_START	0x01400000	/* only used on 64-bit systems */
+#define RAM_END		(512<<20)	/* Fixme: use OF */
+#define	ONE_MB		0x100000
+
+
+
+static unsigned long claim_base;
+
+void epapr_platform_init(unsigned long r3, unsigned long r4, unsigned long r5,
+			 unsigned long r6, unsigned long r7);
+
+static void *of_try_claim(unsigned long size)
+{
+	unsigned long addr = 0;
+
+	if (claim_base == 0)
+		claim_base = _ALIGN_UP((unsigned long)_end, ONE_MB);
+
+	for(; claim_base < RAM_END; claim_base += ONE_MB) {
+#ifdef DEBUG
+		printf("    trying: 0x%08lx\n\r", claim_base);
+#endif
+		addr = (unsigned long) of_claim(claim_base, size, 0);
+		if (addr != PROM_ERROR)
+			break;
+	}
+	if (addr == 0)
+		return NULL;
+	claim_base = PAGE_ALIGN(claim_base + size);
+	return (void *)addr;
+}
+
+static void of_image_hdr(const void *hdr)
+{
+	const Elf64_Ehdr *elf64 = hdr;
+
+	if (elf64->e_ident[EI_CLASS] == ELFCLASS64) {
+		/*
+		 * Maintain a "magic" minimum address. This keeps some older
+		 * firmware platforms running.
+		 */
+		if (claim_base < PROG_START)
+			claim_base = PROG_START;
+	}
+}
+
+static void of_platform_init(unsigned long a1, unsigned long a2, void *promptr)
+{
+	platform_ops.image_hdr = of_image_hdr;
+	platform_ops.malloc = of_try_claim;
+	platform_ops.exit = of_exit;
+	platform_ops.vmlinux_alloc = of_vmlinux_alloc;
+
+	dt_ops.finddevice = of_finddevice;
+	dt_ops.getprop = of_getprop;
+	dt_ops.setprop = of_setprop;
+
+	of_console_init();
+
+	of_init(promptr);
+	loader_info.promptr = promptr;
+	if (a1 && a2 && a2 != 0xdeadbeef) {
+		loader_info.initrd_addr = a1;
+		loader_info.initrd_size = a2;
+	}
+}
+
+void platform_init(unsigned long r3, unsigned long r4, unsigned long r5,
+		   unsigned long r6, unsigned long r7)
+{
+	/* Detect OF vs. ePAPR boot */
+	if (r5)
+		of_platform_init(r3, r4, (void *)r5);
+	else
+		epapr_platform_init(r3, r4, r5, r6, r7);
+}
+