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, 136 insertions, 0 deletions

diff --git a/drivers/net/ipa/reg.h b/drivers/net/ipa/reg.h
new file mode 100644
index 000000000..53c16e594
--- /dev/null
+++ b/drivers/net/ipa/reg.h
@@ -0,0 +1,136 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+/* Copyright (C) 2022-2024 Linaro Ltd. */
+
+#ifndef _REG_H_
+#define _REG_H_
+
+#include <linux/array_size.h>
+#include <linux/bits.h>
+#include <linux/bug.h>
+#include <linux/log2.h>
+#include <linux/types.h>
+
+/**
+ * struct reg - A register descriptor
+ * @offset:	Register offset relative to base of register memory
+ * @stride:	Distance between two instances, if parameterized
+ * @fcount:	Number of entries in the @fmask array
+ * @fmask:	Array of mask values defining position and width of fields
+ * @name:	Upper-case name of the register
+ */
+struct reg {
+	u32 offset;
+	u32 stride;
+	u32 fcount;
+	const u32 *fmask;			/* BIT(nr) or GENMASK(h, l) */
+	const char *name;
+};
+
+/* Helper macro for defining "simple" (non-parameterized) registers */
+#define REG(__NAME, __reg_id, __offset)					\
+	REG_STRIDE(__NAME, __reg_id, __offset, 0)
+
+/* Helper macro for defining parameterized registers, specifying stride */
+#define REG_STRIDE(__NAME, __reg_id, __offset, __stride)		\
+	static const struct reg reg_ ## __reg_id = {			\
+		.name	= #__NAME,					\
+		.offset	= __offset,					\
+		.stride	= __stride,					\
+	}
+
+#define REG_FIELDS(__NAME, __name, __offset)				\
+	REG_STRIDE_FIELDS(__NAME, __name, __offset, 0)
+
+#define REG_STRIDE_FIELDS(__NAME, __name, __offset, __stride)		\
+	static const struct reg reg_ ## __name = {			\
+		.name   = #__NAME,					\
+		.offset = __offset,					\
+		.stride = __stride,					\
+		.fcount = ARRAY_SIZE(reg_ ## __name ## _fmask),		\
+		.fmask  = reg_ ## __name ## _fmask,			\
+	}
+
+/**
+ * struct regs - Description of registers supported by hardware
+ * @reg_count:	Number of registers in the @reg[] array
+ * @reg:	Array of register descriptors
+ */
+struct regs {
+	u32 reg_count;
+	const struct reg **reg;
+};
+
+static inline const struct reg *reg(const struct regs *regs, u32 reg_id)
+{
+	if (WARN(reg_id >= regs->reg_count,
+		 "reg out of range (%u > %u)\n", reg_id, regs->reg_count - 1))
+		return NULL;
+
+	return regs->reg[reg_id];
+}
+
+/* Return the field mask for a field in a register, or 0 on error */
+static inline u32 reg_fmask(const struct reg *reg, u32 field_id)
+{
+	if (!reg || WARN_ON(field_id >= reg->fcount))
+		return 0;
+
+	return reg->fmask[field_id];
+}
+
+/* Return the mask for a single-bit field in a register, or 0 on error  */
+static inline u32 reg_bit(const struct reg *reg, u32 field_id)
+{
+	u32 fmask = reg_fmask(reg, field_id);
+
+	if (WARN_ON(!is_power_of_2(fmask)))
+		return 0;
+
+	return fmask;
+}
+
+/* Return the maximum value representable by the given field; always 2^n - 1 */
+static inline u32 reg_field_max(const struct reg *reg, u32 field_id)
+{
+	u32 fmask = reg_fmask(reg, field_id);
+
+	return fmask ? fmask >> __ffs(fmask) : 0;
+}
+
+/* Encode a value into the given field of a register */
+static inline u32 reg_encode(const struct reg *reg, u32 field_id, u32 val)
+{
+	u32 fmask = reg_fmask(reg, field_id);
+
+	if (!fmask)
+		return 0;
+
+	val <<= __ffs(fmask);
+	if (WARN_ON(val & ~fmask))
+		return 0;
+
+	return val;
+}
+
+/* Given a register value, decode (extract) the value in the given field */
+static inline u32 reg_decode(const struct reg *reg, u32 field_id, u32 val)
+{
+	u32 fmask = reg_fmask(reg, field_id);
+
+	return fmask ? (val & fmask) >> __ffs(fmask) : 0;
+}
+
+/* Returns 0 for NULL reg; warning should have already been issued */
+static inline u32 reg_offset(const struct reg *reg)
+{
+	return reg ? reg->offset : 0;
+}
+
+/* Returns 0 for NULL reg; warning should have already been issued */
+static inline u32 reg_n_offset(const struct reg *reg, u32 n)
+{
+	return reg ? reg->offset + n * reg->stride : 0;
+}
+
+#endif /* _REG_H_ */