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, 266 insertions, 0 deletions

diff --git a/drivers/parisc/power.c b/drivers/parisc/power.c
new file mode 100644
index 000000000..9d6c7bf72
--- /dev/null
+++ b/drivers/parisc/power.c
@@ -0,0 +1,266 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * HP PARISC soft power switch driver
+ *
+ * Copyright (c) 2001-2023 Helge Deller <deller@gmx.de>
+ *
+ *  HINT:
+ *  Support of the soft power switch button may be enabled or disabled at
+ *  runtime through the "/proc/sys/kernel/power" procfs entry.
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/panic_notifier.h>
+#include <linux/reboot.h>
+#include <linux/sched/signal.h>
+#include <linux/kthread.h>
+#include <linux/pm.h>
+
+#include <asm/pdc.h>
+#include <asm/io.h>
+#include <asm/led.h>
+
+#define DRIVER_NAME  "powersw"
+#define KTHREAD_NAME "kpowerswd"
+
+/* how often should the power button be polled ? */
+#define POWERSWITCH_POLL_PER_SEC 2
+
+/* how long does the power button needs to be down until we react ? */
+#define POWERSWITCH_DOWN_SEC 2
+
+/* assembly code to access special registers */
+/* taken from PCXL ERS page 82 */
+#define DIAG_CODE(code)		(0x14000000 + ((code)<<5))
+
+#define MFCPU_X(rDiagReg, t_ch, t_th, code) \
+	(DIAG_CODE(code) + ((rDiagReg)<<21) + ((t_ch)<<16) + ((t_th)<<0) )
+
+#define MTCPU(dr, gr)		MFCPU_X(dr, gr,  0, 0x12)       /* move value of gr to dr[dr] */
+#define MFCPU_C(dr, gr)		MFCPU_X(dr, gr,  0, 0x30)	/* for dr0 and dr8 only ! */
+#define MFCPU_T(dr, gr)		MFCPU_X(dr,  0, gr, 0xa0)	/* all dr except dr0 and dr8 */
+
+#define __getDIAG(dr) ( {			\
+        register unsigned long __res asm("r28");\
+	 __asm__ __volatile__ (			\
+		".word %1" : "=&r" (__res) : "i" (MFCPU_T(dr,28) ) \
+	);					\
+	__res;					\
+} )
+
+/* local shutdown counter */
+static int shutdown_timer __read_mostly;
+
+/* check, give feedback and start shutdown after one second */
+static void process_shutdown(void)
+{
+	if (shutdown_timer == 0)
+		printk(KERN_ALERT KTHREAD_NAME ": Shutdown requested...\n");
+
+	shutdown_timer++;
+
+	/* wait until the button was pressed for 1 second */
+	if (shutdown_timer == (POWERSWITCH_DOWN_SEC*POWERSWITCH_POLL_PER_SEC)) {
+		static const char msg[] = "Shutting down...";
+		printk(KERN_INFO KTHREAD_NAME ": %s\n", msg);
+		lcd_print(msg);
+
+		/* send kill signal */
+		if (kill_cad_pid(SIGINT, 1)) {
+			/* just in case killing init process failed */
+			machine_power_off();
+		}
+	}
+}
+
+
+/* main power switch task struct */
+static struct task_struct *power_task;
+
+/* filename in /proc which can be used to enable/disable the power switch */
+#define SYSCTL_FILENAME	"sys/kernel/power"
+
+/* soft power switch enabled/disabled */
+static int pwrsw_enabled __read_mostly = 1;
+
+static const struct ctl_table power_sysctl_table[] = {
+	{
+		.procname	= "soft-power",
+		.data		= &pwrsw_enabled,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec,
+	},
+};
+
+static int __init init_power_sysctl(void)
+{
+	register_sysctl_init("kernel", power_sysctl_table);
+	return 0;
+}
+
+arch_initcall(init_power_sysctl);
+
+/* main kernel thread worker. It polls the button state */
+static int kpowerswd(void *param)
+{
+	__set_current_state(TASK_RUNNING);
+
+	do {
+		int button_not_pressed;
+		unsigned long soft_power_reg = (unsigned long) param;
+
+		schedule_timeout_interruptible(pwrsw_enabled ? HZ : HZ/POWERSWITCH_POLL_PER_SEC);
+
+		if (unlikely(!pwrsw_enabled))
+			continue;
+
+		if (soft_power_reg) {
+			/*
+			 * Non-Gecko-style machines:
+			 * Check the power switch status which is read from the
+			 * real I/O location at soft_power_reg.
+			 * Bit 31 ("the lowest bit) is the status of the power switch.
+			 * This bit is "1" if the button is NOT pressed.
+			 */
+			button_not_pressed = (gsc_readl(soft_power_reg) & 0x1);
+		} else {
+			/*
+			 * On gecko style machines (e.g. 712/xx and 715/xx)
+			 * the power switch status is stored in Bit 0 ("the highest bit")
+			 * of CPU diagnose register 25.
+			 * Warning: Some machines never reset the DIAG flag, even if
+			 * the button has been released again.
+			 */
+			button_not_pressed = (__getDIAG(25) & 0x80000000);
+		}
+
+		if (likely(button_not_pressed)) {
+			if (unlikely(shutdown_timer && /* avoid writing if not necessary */
+				shutdown_timer < (POWERSWITCH_DOWN_SEC*POWERSWITCH_POLL_PER_SEC))) {
+				shutdown_timer = 0;
+				printk(KERN_INFO KTHREAD_NAME ": Shutdown request aborted.\n");
+			}
+		} else
+			process_shutdown();
+
+
+	} while (!kthread_should_stop());
+
+	return 0;
+}
+
+
+/*
+ * powerfail interruption handler (irq IRQ_FROM_REGION(CPU_IRQ_REGION)+2)
+ */
+#if 0
+static void powerfail_interrupt(int code, void *x)
+{
+	printk(KERN_CRIT "POWERFAIL INTERRUPTION !\n");
+	poweroff();
+}
+#endif
+
+
+
+
+/*
+ * parisc_panic_event() is called by the panic handler.
+ *
+ * As soon as a panic occurs, our tasklets above will not
+ * be executed any longer. This function then re-enables
+ * the soft-power switch and allows the user to switch off
+ * the system. We rely in pdc_soft_power_button_panic()
+ * since this version spin_trylocks (instead of regular
+ * spinlock), preventing deadlocks on panic path.
+ */
+static int parisc_panic_event(struct notifier_block *this,
+		unsigned long event, void *ptr)
+{
+	/* re-enable the soft-power switch */
+	pdc_soft_power_button_panic(0);
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block parisc_panic_block = {
+	.notifier_call	= parisc_panic_event,
+	.priority	= INT_MAX,
+};
+
+/* qemu soft power-off function */
+static int qemu_power_off(struct sys_off_data *data)
+{
+	/* this turns the system off via SeaBIOS */
+	gsc_writel(0, (unsigned long) data->cb_data);
+	pdc_soft_power_button(1);
+	return NOTIFY_DONE;
+}
+
+static int __init power_init(void)
+{
+	unsigned long ret;
+	unsigned long soft_power_reg;
+
+#if 0
+	request_irq( IRQ_FROM_REGION(CPU_IRQ_REGION)+2, &powerfail_interrupt,
+		0, "powerfail", NULL);
+#endif
+
+	/* enable the soft power switch if possible */
+	ret = pdc_soft_power_info(&soft_power_reg);
+	if (ret == PDC_OK)
+		ret = pdc_soft_power_button(1);
+	if (ret != PDC_OK)
+		soft_power_reg = -1UL;
+
+	switch (soft_power_reg) {
+	case 0:		printk(KERN_INFO DRIVER_NAME ": Gecko-style soft power switch enabled.\n");
+			break;
+
+	case -1UL:	printk(KERN_INFO DRIVER_NAME ": Soft power switch support not available.\n");
+			return -ENODEV;
+
+	default:	printk(KERN_INFO DRIVER_NAME ": Soft power switch at 0x%08lx enabled.\n",
+				soft_power_reg);
+	}
+
+	power_task = NULL;
+	if (running_on_qemu && soft_power_reg)
+		register_sys_off_handler(SYS_OFF_MODE_POWER_OFF, SYS_OFF_PRIO_DEFAULT,
+					qemu_power_off, (void *)soft_power_reg);
+	if (!running_on_qemu || soft_power_reg)
+		power_task = kthread_run(kpowerswd, (void*)soft_power_reg,
+					KTHREAD_NAME);
+	if (IS_ERR(power_task)) {
+		printk(KERN_ERR DRIVER_NAME ": thread creation failed.  Driver not loaded.\n");
+		pdc_soft_power_button(0);
+		return -EIO;
+	}
+
+	/* Register a call for panic conditions. */
+	atomic_notifier_chain_register(&panic_notifier_list,
+			&parisc_panic_block);
+
+	return 0;
+}
+
+static void __exit power_exit(void)
+{
+	kthread_stop(power_task);
+
+	atomic_notifier_chain_unregister(&panic_notifier_list,
+			&parisc_panic_block);
+
+	pdc_soft_power_button(0);
+}
+
+arch_initcall(power_init);
+module_exit(power_exit);
+
+
+MODULE_AUTHOR("Helge Deller <deller@gmx.de>");
+MODULE_DESCRIPTION("Soft power switch driver");
+MODULE_LICENSE("Dual BSD/GPL");