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, 168 insertions, 0 deletions

diff --git a/arch/m68k/mac/psc.c b/arch/m68k/mac/psc.c
new file mode 100644
index 000000000..b4183cf66
--- /dev/null
+++ b/arch/m68k/mac/psc.c
@@ -0,0 +1,168 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *	Apple Peripheral System Controller (PSC)
+ *
+ *	The PSC is used on the AV Macs to control IO functions not handled
+ *	by the VIAs (Ethernet, DSP, SCC).
+ *
+ * TO DO:
+ *
+ * Try to figure out what's going on in pIFR5 and pIFR6. There seem to be
+ * persisant interrupt conditions in those registers and I have no idea what
+ * they are. Granted it doesn't affect since we're not enabling any interrupts
+ * on those levels at the moment, but it would be nice to know. I have a feeling
+ * they aren't actually interrupt lines but data lines (to the DSP?)
+ */
+
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/delay.h>
+#include <linux/init.h>
+#include <linux/irq.h>
+
+#include <asm/traps.h>
+#include <asm/macintosh.h>
+#include <asm/macints.h>
+#include <asm/mac_psc.h>
+
+#include "mac.h"
+
+#define DEBUG_PSC
+
+volatile __u8 *psc;
+EXPORT_SYMBOL_GPL(psc);
+
+/*
+ * Debugging dump, used in various places to see what's going on.
+ */
+
+static void psc_debug_dump(void)
+{
+	int	i;
+
+	if (!psc)
+		return;
+
+	for (i = 0x30 ; i < 0x70 ; i += 0x10) {
+		printk(KERN_DEBUG "PSC #%d:  IFR = 0x%02X IER = 0x%02X\n",
+			i >> 4,
+			(int) psc_read_byte(pIFRbase + i),
+			(int) psc_read_byte(pIERbase + i));
+	}
+}
+
+/*
+ * Try to kill all DMA channels on the PSC. Not sure how this his
+ * supposed to work; this is code lifted from macmace.c and then
+ * expanded to cover what I think are the other 7 channels.
+ */
+
+static __init void psc_dma_die_die_die(void)
+{
+	int i;
+
+	for (i = 0 ; i < 9 ; i++) {
+		psc_write_word(PSC_CTL_BASE + (i << 4), 0x8800);
+		psc_write_word(PSC_CTL_BASE + (i << 4), 0x1000);
+		psc_write_word(PSC_CMD_BASE + (i << 5), 0x1100);
+		psc_write_word(PSC_CMD_BASE + (i << 5) + 0x10, 0x1100);
+	}
+}
+
+/*
+ * Initialize the PSC. For now this just involves shutting down all
+ * interrupt sources using the IERs.
+ */
+
+void __init psc_init(void)
+{
+	int i;
+
+	if (macintosh_config->ident != MAC_MODEL_C660
+	 && macintosh_config->ident != MAC_MODEL_Q840)
+	{
+		psc = NULL;
+		return;
+	}
+
+	/*
+	 * The PSC is always at the same spot, but using psc
+	 * keeps things consistent with the psc_xxxx functions.
+	 */
+
+	psc = (void *) PSC_BASE;
+
+	pr_debug("PSC detected at %p\n", psc);
+
+	psc_dma_die_die_die();
+
+#ifdef DEBUG_PSC
+	psc_debug_dump();
+#endif
+	/*
+	 * Mask and clear all possible interrupts
+	 */
+
+	for (i = 0x30 ; i < 0x70 ; i += 0x10) {
+		psc_write_byte(pIERbase + i, 0x0F);
+		psc_write_byte(pIFRbase + i, 0x0F);
+	}
+}
+
+/*
+ * PSC interrupt handler. It's a lot like the VIA interrupt handler.
+ */
+
+static void psc_irq(struct irq_desc *desc)
+{
+	unsigned int offset = (unsigned int)irq_desc_get_handler_data(desc);
+	unsigned int irq = irq_desc_get_irq(desc);
+	int pIFR	= pIFRbase + offset;
+	int pIER	= pIERbase + offset;
+	int irq_num;
+	unsigned char irq_bit, events;
+
+	events = psc_read_byte(pIFR) & psc_read_byte(pIER) & 0xF;
+	if (!events)
+		return;
+
+	irq_num = irq << 3;
+	irq_bit = 1;
+	do {
+		if (events & irq_bit) {
+			psc_write_byte(pIFR, irq_bit);
+			generic_handle_irq(irq_num);
+		}
+		irq_num++;
+		irq_bit <<= 1;
+	} while (events >= irq_bit);
+}
+
+/*
+ * Register the PSC interrupt dispatchers for autovector interrupts 3-6.
+ */
+
+void __init psc_register_interrupts(void)
+{
+	irq_set_chained_handler_and_data(IRQ_AUTO_3, psc_irq, (void *)0x30);
+	irq_set_chained_handler_and_data(IRQ_AUTO_4, psc_irq, (void *)0x40);
+	irq_set_chained_handler_and_data(IRQ_AUTO_5, psc_irq, (void *)0x50);
+	irq_set_chained_handler_and_data(IRQ_AUTO_6, psc_irq, (void *)0x60);
+}
+
+void psc_irq_enable(int irq) {
+	int irq_src	= IRQ_SRC(irq);
+	int irq_idx	= IRQ_IDX(irq);
+	int pIER	= pIERbase + (irq_src << 4);
+
+	psc_write_byte(pIER, (1 << irq_idx) | 0x80);
+}
+
+void psc_irq_disable(int irq) {
+	int irq_src	= IRQ_SRC(irq);
+	int irq_idx	= IRQ_IDX(irq);
+	int pIER	= pIERbase + (irq_src << 4);
+
+	psc_write_byte(pIER, 1 << irq_idx);
+}