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, 142 insertions, 0 deletions

diff --git a/drivers/clk/tegra/cvb.c b/drivers/clk/tegra/cvb.c
new file mode 100644
index 000000000..a7fdc7622
--- /dev/null
+++ b/drivers/clk/tegra/cvb.c
@@ -0,0 +1,142 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Utility functions for parsing Tegra CVB voltage tables
+ *
+ * Copyright (C) 2012-2019 NVIDIA Corporation.  All rights reserved.
+ */
+#include <linux/err.h>
+#include <linux/kernel.h>
+#include <linux/pm_opp.h>
+
+#include "cvb.h"
+
+/* cvb_mv = ((c2 * speedo / s_scale + c1) * speedo / s_scale + c0) */
+static inline int get_cvb_voltage(int speedo, int s_scale,
+				  const struct cvb_coefficients *cvb)
+{
+	int mv;
+
+	/* apply only speedo scale: output mv = cvb_mv * v_scale */
+	mv = DIV_ROUND_CLOSEST(cvb->c2 * speedo, s_scale);
+	mv = DIV_ROUND_CLOSEST((mv + cvb->c1) * speedo, s_scale) + cvb->c0;
+	return mv;
+}
+
+static int round_cvb_voltage(int mv, int v_scale,
+			     const struct rail_alignment *align)
+{
+	/* combined: apply voltage scale and round to cvb alignment step */
+	int uv;
+	int step = (align->step_uv ? : 1000) * v_scale;
+	int offset = align->offset_uv * v_scale;
+
+	uv = max(mv * 1000, offset) - offset;
+	uv = DIV_ROUND_UP(uv, step) * align->step_uv + align->offset_uv;
+	return uv / 1000;
+}
+
+enum {
+	DOWN,
+	UP
+};
+
+static int round_voltage(int mv, const struct rail_alignment *align, int up)
+{
+	if (align->step_uv) {
+		int uv;
+
+		uv = max(mv * 1000, align->offset_uv) - align->offset_uv;
+		uv = (uv + (up ? align->step_uv - 1 : 0)) / align->step_uv;
+		return (uv * align->step_uv + align->offset_uv) / 1000;
+	}
+	return mv;
+}
+
+static int build_opp_table(struct device *dev, const struct cvb_table *table,
+			   struct rail_alignment *align,
+			   int speedo_value, unsigned long max_freq)
+{
+	int i, ret, dfll_mv, min_mv, max_mv;
+
+	min_mv = round_voltage(table->min_millivolts, align, UP);
+	max_mv = round_voltage(table->max_millivolts, align, DOWN);
+
+	for (i = 0; i < MAX_DVFS_FREQS; i++) {
+		const struct cvb_table_freq_entry *entry = &table->entries[i];
+
+		if (!entry->freq || (entry->freq > max_freq))
+			break;
+
+		dfll_mv = get_cvb_voltage(speedo_value, table->speedo_scale,
+					  &entry->coefficients);
+		dfll_mv = round_cvb_voltage(dfll_mv, table->voltage_scale,
+					    align);
+		dfll_mv = clamp(dfll_mv, min_mv, max_mv);
+
+		ret = dev_pm_opp_add(dev, entry->freq, dfll_mv * 1000);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+
+/**
+ * tegra_cvb_add_opp_table - build OPP table from Tegra CVB tables
+ * @dev: the struct device * for which the OPP table is built
+ * @tables: array of CVB tables
+ * @count: size of the previously mentioned array
+ * @align: parameters of the regulator step and offset
+ * @process_id: process id of the HW module
+ * @speedo_id: speedo id of the HW module
+ * @speedo_value: speedo value of the HW module
+ * @max_freq: highest safe clock rate
+ *
+ * On Tegra, a CVB table encodes the relationship between operating voltage
+ * and safe maximal frequency for a given module (e.g. GPU or CPU). This
+ * function calculates the optimal voltage-frequency operating points
+ * for the given arguments and exports them via the OPP library for the
+ * given @dev. Returns a pointer to the struct cvb_table that matched
+ * or an ERR_PTR on failure.
+ */
+const struct cvb_table *
+tegra_cvb_add_opp_table(struct device *dev, const struct cvb_table *tables,
+			size_t count, struct rail_alignment *align,
+			int process_id, int speedo_id, int speedo_value,
+			unsigned long max_freq)
+{
+	size_t i;
+	int ret;
+
+	for (i = 0; i < count; i++) {
+		const struct cvb_table *table = &tables[i];
+
+		if (table->speedo_id != -1 && table->speedo_id != speedo_id)
+			continue;
+
+		if (table->process_id != -1 && table->process_id != process_id)
+			continue;
+
+		ret = build_opp_table(dev, table, align, speedo_value,
+				      max_freq);
+		return ret ? ERR_PTR(ret) : table;
+	}
+
+	return ERR_PTR(-EINVAL);
+}
+
+void tegra_cvb_remove_opp_table(struct device *dev,
+				const struct cvb_table *table,
+				unsigned long max_freq)
+{
+	unsigned int i;
+
+	for (i = 0; i < MAX_DVFS_FREQS; i++) {
+		const struct cvb_table_freq_entry *entry = &table->entries[i];
+
+		if (!entry->freq || (entry->freq > max_freq))
+			break;
+
+		dev_pm_opp_remove(dev, entry->freq);
+	}
+}