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, 90 insertions, 0 deletions

diff --git a/drivers/clocksource/scx200_hrt.c b/drivers/clocksource/scx200_hrt.c
new file mode 100644
index 000000000..5a99801a1
--- /dev/null
+++ b/drivers/clocksource/scx200_hrt.c
@@ -0,0 +1,90 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2006 Jim Cromie
+ *
+ * This is a clocksource driver for the Geode SCx200's 1 or 27 MHz
+ * high-resolution timer.  The Geode SC-1100 (at least) has a buggy
+ * time stamp counter (TSC), which loses time unless 'idle=poll' is
+ * given as a boot-arg. In its absence, the Generic Timekeeping code
+ * will detect and de-rate the bad TSC, allowing this timer to take
+ * over timekeeping duties.
+ *
+ * Based on work by John Stultz, and Ted Phelps (in a 2.6.12-rc6 patch)
+ */
+
+#include <linux/clocksource.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/ioport.h>
+#include <linux/scx200.h>
+
+#define NAME "scx200_hrt"
+
+static int mhz27;
+module_param(mhz27, int, 0);	/* load time only */
+MODULE_PARM_DESC(mhz27, "count at 27.0 MHz (default is 1.0 MHz)");
+
+static int ppm;
+module_param(ppm, int, 0);	/* load time only */
+MODULE_PARM_DESC(ppm, "+-adjust to actual XO freq (ppm)");
+
+/* HiRes Timer configuration register address */
+#define SCx200_TMCNFG_OFFSET (SCx200_TIMER_OFFSET + 5)
+
+/* and config settings */
+#define HR_TMEN (1 << 0)	/* timer interrupt enable */
+#define HR_TMCLKSEL (1 << 1)	/* 1|0 counts at 27|1 MHz */
+#define HR_TM27MPD (1 << 2)	/* 1 turns off input clock (power-down) */
+
+/* The base timer frequency, * 27 if selected */
+#define HRT_FREQ   1000000
+
+static u64 read_hrt(struct clocksource *cs)
+{
+	/* Read the timer value */
+	return (u64) inl(scx200_cb_base + SCx200_TIMER_OFFSET);
+}
+
+static struct clocksource cs_hrt = {
+	.name		= "scx200_hrt",
+	.rating		= 250,
+	.read		= read_hrt,
+	.mask		= CLOCKSOURCE_MASK(32),
+	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
+	/* mult, shift are set based on mhz27 flag */
+	.owner		= THIS_MODULE,
+};
+
+static int __init init_hrt_clocksource(void)
+{
+	u32 freq;
+	/* Make sure scx200 has initialized the configuration block */
+	if (!scx200_cb_present())
+		return -ENODEV;
+
+	/* Reserve the timer's ISA io-region for ourselves */
+	if (!request_region(scx200_cb_base + SCx200_TIMER_OFFSET,
+			    SCx200_TIMER_SIZE,
+			    "NatSemi SCx200 High-Resolution Timer")) {
+		pr_warn("unable to lock timer region\n");
+		return -ENODEV;
+	}
+
+	/* write timer config */
+	outb(HR_TMEN | (mhz27 ? HR_TMCLKSEL : 0),
+	     scx200_cb_base + SCx200_TMCNFG_OFFSET);
+
+	freq = (HRT_FREQ + ppm);
+	if (mhz27)
+		freq *= 27;
+
+	pr_info("enabling scx200 high-res timer (%s MHz +%d ppm)\n", mhz27 ? "27":"1", ppm);
+
+	return clocksource_register_hz(&cs_hrt, freq);
+}
+
+module_init(init_hrt_clocksource);
+
+MODULE_AUTHOR("Jim Cromie <jim.cromie@gmail.com>");
+MODULE_DESCRIPTION("clocksource on SCx200 HiRes Timer");
+MODULE_LICENSE("GPL");