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, 319 insertions, 0 deletions

diff --git a/drivers/cpufreq/longrun.c b/drivers/cpufreq/longrun.c
new file mode 100644
index 000000000..82a7bb69c
--- /dev/null
+++ b/drivers/cpufreq/longrun.c
@@ -0,0 +1,319 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * (C) 2002 - 2003  Dominik Brodowski <linux@brodo.de>
+ *
+ *  BIG FAT DISCLAIMER: Work in progress code. Possibly *dangerous*
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/cpufreq.h>
+#include <linux/timex.h>
+
+#include <asm/msr.h>
+#include <asm/processor.h>
+#include <asm/cpu_device_id.h>
+#include <asm/cpuid/api.h>
+
+static struct cpufreq_driver	longrun_driver;
+
+/**
+ * longrun_{low,high}_freq is needed for the conversion of cpufreq kHz
+ * values into per cent values. In TMTA microcode, the following is valid:
+ * performance_pctg = (current_freq - low_freq)/(high_freq - low_freq)
+ */
+static unsigned int longrun_low_freq, longrun_high_freq;
+
+
+/**
+ * longrun_get_policy - get the current LongRun policy
+ * @policy: struct cpufreq_policy where current policy is written into
+ *
+ * Reads the current LongRun policy by access to MSR_TMTA_LONGRUN_FLAGS
+ * and MSR_TMTA_LONGRUN_CTRL
+ */
+static void longrun_get_policy(struct cpufreq_policy *policy)
+{
+	struct msr msr;
+
+	rdmsrq(MSR_TMTA_LONGRUN_FLAGS, msr.q);
+	pr_debug("longrun flags are %x - %x\n", msr.l, msr.h);
+	if (msr.l & 0x01)
+		policy->policy = CPUFREQ_POLICY_PERFORMANCE;
+	else
+		policy->policy = CPUFREQ_POLICY_POWERSAVE;
+
+	rdmsrq(MSR_TMTA_LONGRUN_CTRL, msr.q);
+	pr_debug("longrun ctrl is %x - %x\n", msr.l, msr.h);
+	msr.l &= 0x0000007F;
+	msr.h &= 0x0000007F;
+
+	if (longrun_high_freq <= longrun_low_freq) {
+		/* Assume degenerate Longrun table */
+		policy->min = policy->max = longrun_high_freq;
+	} else {
+		policy->min = longrun_low_freq + msr.l *
+			((longrun_high_freq - longrun_low_freq) / 100);
+		policy->max = longrun_low_freq + msr.h *
+			((longrun_high_freq - longrun_low_freq) / 100);
+	}
+	policy->cpu = 0;
+}
+
+
+/**
+ * longrun_set_policy - sets a new CPUFreq policy
+ * @policy: new policy
+ *
+ * Sets a new CPUFreq policy on LongRun-capable processors. This function
+ * has to be called with cpufreq_driver locked.
+ */
+static int longrun_set_policy(struct cpufreq_policy *policy)
+{
+	struct msr msr;
+	u32 pctg_lo, pctg_hi;
+
+	if (!policy)
+		return -EINVAL;
+
+	if (longrun_high_freq <= longrun_low_freq) {
+		/* Assume degenerate Longrun table */
+		pctg_lo = pctg_hi = 100;
+	} else {
+		pctg_lo = (policy->min - longrun_low_freq) /
+			((longrun_high_freq - longrun_low_freq) / 100);
+		pctg_hi = (policy->max - longrun_low_freq) /
+			((longrun_high_freq - longrun_low_freq) / 100);
+	}
+
+	if (pctg_hi > 100)
+		pctg_hi = 100;
+	if (pctg_lo > pctg_hi)
+		pctg_lo = pctg_hi;
+
+	/* performance or economy mode */
+	rdmsrq(MSR_TMTA_LONGRUN_FLAGS, msr.q);
+	msr.l &= 0xFFFFFFFE;
+	switch (policy->policy) {
+	case CPUFREQ_POLICY_PERFORMANCE:
+		msr.l |= 0x00000001;
+		break;
+	case CPUFREQ_POLICY_POWERSAVE:
+		break;
+	}
+	wrmsrq(MSR_TMTA_LONGRUN_FLAGS, msr.q);
+
+	/* lower and upper boundary */
+	rdmsrq(MSR_TMTA_LONGRUN_CTRL, msr.q);
+	msr.l &= 0xFFFFFF80;
+	msr.h &= 0xFFFFFF80;
+	msr.l |= pctg_lo;
+	msr.h |= pctg_hi;
+	wrmsrq(MSR_TMTA_LONGRUN_CTRL, msr.q);
+
+	return 0;
+}
+
+
+/**
+ * longrun_verify_poliy - verifies a new CPUFreq policy
+ * @policy: the policy to verify
+ *
+ * Validates a new CPUFreq policy. This function has to be called with
+ * cpufreq_driver locked.
+ */
+static int longrun_verify_policy(struct cpufreq_policy_data *policy)
+{
+	if (!policy)
+		return -EINVAL;
+
+	policy->cpu = 0;
+	cpufreq_verify_within_cpu_limits(policy);
+
+	return 0;
+}
+
+static unsigned int longrun_get(unsigned int cpu)
+{
+	u32 eax, ebx, ecx, edx;
+
+	if (cpu)
+		return 0;
+
+	cpuid(0x80860007, &eax, &ebx, &ecx, &edx);
+	pr_debug("cpuid eax is %u\n", eax);
+
+	return eax * 1000;
+}
+
+/**
+ * longrun_determine_freqs - determines the lowest and highest possible core frequency
+ * @low_freq: an int to put the lowest frequency into
+ * @high_freq: an int to put the highest frequency into
+ *
+ * Determines the lowest and highest possible core frequencies on this CPU.
+ * This is necessary to calculate the performance percentage according to
+ * TMTA rules:
+ * performance_pctg = (target_freq - low_freq)/(high_freq - low_freq)
+ */
+static int longrun_determine_freqs(unsigned int *low_freq,
+						      unsigned int *high_freq)
+{
+	struct msr msr, save;
+	u32 eax, ebx, ecx, edx;
+	u32 try_hi;
+	struct cpuinfo_x86 *c = &cpu_data(0);
+
+	if (!low_freq || !high_freq)
+		return -EINVAL;
+
+	if (cpu_has(c, X86_FEATURE_LRTI)) {
+		/* if the LongRun Table Interface is present, the
+		 * detection is a bit easier:
+		 * For minimum frequency, read out the maximum
+		 * level (msr_hi), write that into "currently
+		 * selected level", and read out the frequency.
+		 * For maximum frequency, read out level zero.
+		 */
+		/* minimum */
+		rdmsrq(MSR_TMTA_LRTI_READOUT, msr.q);
+		msr.l = msr.h;
+		wrmsrq(MSR_TMTA_LRTI_READOUT, msr.q);
+		rdmsrq(MSR_TMTA_LRTI_VOLT_MHZ, msr.q);
+		*low_freq = msr.l * 1000; /* to kHz */
+
+		/* maximum */
+		msr.l = 0;
+		wrmsrq(MSR_TMTA_LRTI_READOUT, msr.q);
+		rdmsrq(MSR_TMTA_LRTI_VOLT_MHZ, msr.q);
+		*high_freq = msr.l * 1000; /* to kHz */
+
+		pr_debug("longrun table interface told %u - %u kHz\n",
+				*low_freq, *high_freq);
+
+		if (*low_freq > *high_freq)
+			*low_freq = *high_freq;
+		return 0;
+	}
+
+	/* set the upper border to the value determined during TSC init */
+	*high_freq = (cpu_khz / 1000);
+	*high_freq = *high_freq * 1000;
+	pr_debug("high frequency is %u kHz\n", *high_freq);
+
+	/* get current borders */
+	rdmsrq(MSR_TMTA_LONGRUN_CTRL, msr.q);
+	save.l = msr.l & 0x0000007F;
+	save.h = msr.h & 0x0000007F;
+
+	/* if current perf_pctg is larger than 90%, we need to decrease the
+	 * upper limit to make the calculation more accurate.
+	 */
+	cpuid(0x80860007, &eax, &ebx, &ecx, &edx);
+	/* try decreasing in 10% steps, some processors react only
+	 * on some barrier values */
+	for (try_hi = 80; try_hi > 0 && ecx > 90; try_hi -= 10) {
+		/* set to 0 to try_hi perf_pctg */
+		msr.l &= 0xFFFFFF80;
+		msr.h &= 0xFFFFFF80;
+		msr.h |= try_hi;
+		wrmsrq(MSR_TMTA_LONGRUN_CTRL, msr.q);
+
+		/* read out current core MHz and current perf_pctg */
+		cpuid(0x80860007, &eax, &ebx, &ecx, &edx);
+
+		/* restore values */
+		wrmsrq(MSR_TMTA_LONGRUN_CTRL, save.q);
+	}
+	pr_debug("percentage is %u %%, freq is %u MHz\n", ecx, eax);
+
+	/* performance_pctg = (current_freq - low_freq)/(high_freq - low_freq)
+	 * eqals
+	 * low_freq * (1 - perf_pctg) = (cur_freq - high_freq * perf_pctg)
+	 *
+	 * high_freq * perf_pctg is stored tempoarily into "ebx".
+	 */
+	ebx = (((cpu_khz / 1000) * ecx) / 100); /* to MHz */
+
+	if ((ecx > 95) || (ecx == 0) || (eax < ebx))
+		return -EIO;
+
+	edx = ((eax - ebx) * 100) / (100 - ecx);
+	*low_freq = edx * 1000; /* back to kHz */
+
+	pr_debug("low frequency is %u kHz\n", *low_freq);
+
+	if (*low_freq > *high_freq)
+		*low_freq = *high_freq;
+
+	return 0;
+}
+
+
+static int longrun_cpu_init(struct cpufreq_policy *policy)
+{
+	int result = 0;
+
+	/* capability check */
+	if (policy->cpu != 0)
+		return -ENODEV;
+
+	/* detect low and high frequency */
+	result = longrun_determine_freqs(&longrun_low_freq, &longrun_high_freq);
+	if (result)
+		return result;
+
+	/* cpuinfo and default policy values */
+	policy->cpuinfo.min_freq = longrun_low_freq;
+	policy->cpuinfo.max_freq = longrun_high_freq;
+	longrun_get_policy(policy);
+
+	return 0;
+}
+
+
+static struct cpufreq_driver longrun_driver = {
+	.flags		= CPUFREQ_CONST_LOOPS,
+	.verify		= longrun_verify_policy,
+	.setpolicy	= longrun_set_policy,
+	.get		= longrun_get,
+	.init		= longrun_cpu_init,
+	.name		= "longrun",
+};
+
+static const struct x86_cpu_id longrun_ids[] = {
+	X86_MATCH_VENDOR_FEATURE(TRANSMETA, X86_FEATURE_LONGRUN, NULL),
+	{}
+};
+MODULE_DEVICE_TABLE(x86cpu, longrun_ids);
+
+/**
+ * longrun_init - initializes the Transmeta Crusoe LongRun CPUFreq driver
+ *
+ * Initializes the LongRun support.
+ */
+static int __init longrun_init(void)
+{
+	if (!x86_match_cpu(longrun_ids))
+		return -ENODEV;
+	return cpufreq_register_driver(&longrun_driver);
+}
+
+
+/**
+ * longrun_exit - unregisters LongRun support
+ */
+static void __exit longrun_exit(void)
+{
+	cpufreq_unregister_driver(&longrun_driver);
+}
+
+
+MODULE_AUTHOR("Dominik Brodowski <linux@brodo.de>");
+MODULE_DESCRIPTION("LongRun driver for Transmeta Crusoe and "
+		"Efficeon processors.");
+MODULE_LICENSE("GPL");
+
+module_init(longrun_init);
+module_exit(longrun_exit);