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, 152 insertions, 0 deletions

diff --git a/arch/powerpc/boot/serial.c b/arch/powerpc/boot/serial.c
new file mode 100644
index 000000000..1d221ff42
--- /dev/null
+++ b/arch/powerpc/boot/serial.c
@@ -0,0 +1,152 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Generic serial console support
+ *
+ * Author: Mark A. Greer <mgreer@mvista.com>
+ *
+ * Code in serial_edit_cmdline() copied from <file:arch/ppc/boot/simple/misc.c>
+ * and was written by Matt Porter <mporter@kernel.crashing.org>.
+ *
+ * 2001,2006 (c) MontaVista Software, Inc.
+ */
+#include <stdarg.h>
+#include <stddef.h>
+#include "types.h"
+#include "string.h"
+#include "stdio.h"
+#include "io.h"
+#include "ops.h"
+
+static int serial_open(void)
+{
+	struct serial_console_data *scdp = console_ops.data;
+	return scdp->open();
+}
+
+static void serial_write(const char *buf, int len)
+{
+	struct serial_console_data *scdp = console_ops.data;
+
+	while (*buf != '\0')
+		scdp->putc(*buf++);
+}
+
+static void serial_edit_cmdline(char *buf, int len, unsigned int timeout)
+{
+	int timer = 0, count;
+	char ch, *cp;
+	struct serial_console_data *scdp = console_ops.data;
+
+	count = strlen(buf);
+	cp = &buf[count];
+	count++;
+
+	do {
+		if (scdp->tstc()) {
+			while (((ch = scdp->getc()) != '\n') && (ch != '\r')) {
+				/* Test for backspace/delete */
+				if ((ch == '\b') || (ch == '\177')) {
+					if (cp != buf) {
+						cp--;
+						count--;
+						printf("\b \b");
+					}
+				/* Test for ^x/^u (and wipe the line) */
+				} else if ((ch == '\030') || (ch == '\025')) {
+					while (cp != buf) {
+						cp--;
+						count--;
+						printf("\b \b");
+					}
+				} else if (count < len) {
+						*cp++ = ch;
+						count++;
+						scdp->putc(ch);
+				}
+			}
+			break;  /* Exit 'timer' loop */
+		}
+		udelay(1000);  /* 1 msec */
+	} while (timer++ < timeout);
+	*cp = 0;
+}
+
+static void serial_close(void)
+{
+	struct serial_console_data *scdp = console_ops.data;
+
+	if (scdp->close)
+		scdp->close();
+}
+
+static void *serial_get_stdout_devp(void)
+{
+	void *devp;
+	char devtype[MAX_PROP_LEN];
+	char path[MAX_PATH_LEN];
+
+	devp = finddevice("/chosen");
+	if (devp == NULL)
+		goto err_out;
+
+	if (getprop(devp, "linux,stdout-path", path, MAX_PATH_LEN) > 0 ||
+		getprop(devp, "stdout-path", path, MAX_PATH_LEN) > 0) {
+		devp = finddevice(path);
+		if (devp == NULL)
+			goto err_out;
+
+		if ((getprop(devp, "device_type", devtype, sizeof(devtype)) > 0)
+				&& !strcmp(devtype, "serial"))
+			return devp;
+	}
+err_out:
+	return NULL;
+}
+
+static struct serial_console_data serial_cd;
+
+/* Node's "compatible" property determines which serial driver to use */
+int serial_console_init(void)
+{
+	void *devp;
+	int rc = -1;
+
+	devp = serial_get_stdout_devp();
+	if (devp == NULL)
+		goto err_out;
+
+	if (dt_is_compatible(devp, "ns16550") ||
+	    dt_is_compatible(devp, "pnpPNP,501"))
+		rc = ns16550_console_init(devp, &serial_cd);
+#ifdef CONFIG_CPM
+	else if (dt_is_compatible(devp, "fsl,cpm1-scc-uart") ||
+	         dt_is_compatible(devp, "fsl,cpm1-smc-uart") ||
+	         dt_is_compatible(devp, "fsl,cpm2-scc-uart") ||
+	         dt_is_compatible(devp, "fsl,cpm2-smc-uart"))
+		rc = cpm_console_init(devp, &serial_cd);
+#endif
+#ifdef CONFIG_PPC_MPC52xx
+	else if (dt_is_compatible(devp, "fsl,mpc5200-psc-uart"))
+		rc = mpc5200_psc_console_init(devp, &serial_cd);
+#endif
+#ifdef CONFIG_PPC_POWERNV
+	else if (dt_is_compatible(devp, "ibm,opal-console-raw"))
+		rc = opal_console_init(devp, &serial_cd);
+#endif
+
+	/* Add other serial console driver calls here */
+
+	if (!rc) {
+		console_ops.open = serial_open;
+		console_ops.write = serial_write;
+		console_ops.close = serial_close;
+		console_ops.data = &serial_cd;
+
+		if (serial_cd.getc)
+			console_ops.edit_cmdline = serial_edit_cmdline;
+
+		return 0;
+	}
+err_out:
+	return -1;
+}