[PATCH v12 04/11] tracing/wprobe: Add wprobe (watchpoint probe) trace event support

["Masami Hiramatsu (Google)" <mhiramat@kernel.org>]

From: Masami Hiramatsu (Google) <mhiramat@kernel.org>

Add hardware-breakpoint-based dynamic trace event support (wprobe).
Wprobe creates a dynamic event on data read/write accesses using
hardware breakpoints and logs the access context and fetchargs.

Link: https://lore.kernel.org/all/59637b96946653393a7ad3c7de094094796b39c2.1785067572.git.wangjinchao600@gmail.com/

Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
---
Changes in v12:
 - Fix syntax comment typo ('b' to 'w') and remove dead 'ret = 0'
   initialization in __trace_wprobe_create().
 - Fix documentation notation to SYMBOL[[+|-]OFFS].
Changes in v11:
 - Add trace_wprobe_is_busy() to prevent releasing busy events.
Changes in v9:
 - Use kzalloc_flex for alloc_trace_wprobe.
---
 Documentation/trace/index.rst       |    1 
 Documentation/trace/wprobetrace.rst |   70 +++
 include/linux/trace_events.h        |    2 
 kernel/trace/Kconfig                |   13 +
 kernel/trace/Makefile               |    1 
 kernel/trace/trace.c                |    9 
 kernel/trace/trace.h                |    5 
 kernel/trace/trace_probe.c          |   21 +
 kernel/trace/trace_probe.h          |   10 
 kernel/trace/trace_wprobe.c         |  765 +++++++++++++++++++++++++++++++++++
 10 files changed, 893 insertions(+), 4 deletions(-)
 create mode 100644 Documentation/trace/wprobetrace.rst
 create mode 100644 kernel/trace/trace_wprobe.c

diff --git a/Documentation/trace/index.rst b/Documentation/trace/index.rst
index 5d9bf4694d5d..2f04f32001ed 100644
--- a/Documentation/trace/index.rst
+++ b/Documentation/trace/index.rst
@@ -36,6 +36,7 @@ the Linux kernel.
    kprobes
    kprobetrace
    fprobetrace
+   wprobetrace
    eprobetrace
    fprobe
    ring-buffer-design
diff --git a/Documentation/trace/wprobetrace.rst b/Documentation/trace/wprobetrace.rst
new file mode 100644
index 000000000000..ad5f089b5ef5
--- /dev/null
+++ b/Documentation/trace/wprobetrace.rst
@@ -0,0 +1,70 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=======================================
+Watchpoint probe (wprobe) Event Tracing
+=======================================
+
+.. Author: Masami Hiramatsu <mhiramat@kernel.org>
+
+Overview
+--------
+
+Wprobe event is a dynamic event based on the hardware breakpoint, which is
+similar to other probe events, but it is for watching data access. It allows
+you to trace which code accesses a specified data.
+
+As same as other dynamic events, wprobe events are defined via
+`dynamic_events` interface file on tracefs.
+
+Synopsis of wprobe-events
+-------------------------
+::
+
+  w:[GRP/][EVENT] SPEC [FETCHARGS]                       : Probe on data access
+
+ GRP            : Group name for wprobe. If omitted, use "wprobes" for it.
+ EVENT          : Event name for wprobe. If omitted, an event name is
+                  generated based on the address or symbol.
+ SPEC           : Breakpoint specification.
+                  [r|w|rw]@<ADDRESS|SYMBOL[[+|-]OFFS]>[:LENGTH]
+
+   r|w|rw       : Access type, r for read, w for write, and rw for both.
+                  Default is rw if omitted.
+   ADDRESS      : Address to trace (hexadecimal). MUST be in kernel space.
+   SYMBOL       : Symbol name to trace.
+   LENGTH       : Length of the data to trace in bytes. (1, 2, 4, or 8)
+
+  FETCHARGS      : Arguments. Each probe can have up to 128 args.
+   $addr         : Fetch the accessing address.
+   $value        : Fetch the memory value at the accessing address (same as +0($addr)).
+   @ADDR         : Fetch memory at ADDR (ADDR should be in kernel)
+  @SYM[+|-offs] : Fetch memory at SYM +|- offs (SYM should be a data symbol)
+  +|-[u]OFFS(FETCHARG) : Fetch memory at FETCHARG +|- OFFS address.(\*1)(\*2)
+  \IMM          : Store an immediate value to the argument.
+  NAME=FETCHARG : Set NAME as the argument name of FETCHARG.
+  FETCHARG:TYPE : Set TYPE as the type of FETCHARG. Currently, basic types
+                  (u8/u16/u32/u64/s8/s16/s32/s64), hexadecimal types
+                  (x8/x16/x32/x64), "char", "string", "ustring", "symbol", "symstr"
+                  and bitfield are supported.
+
+  (\*1) this is useful for fetching a field of data structures.
+  (\*2) "u" means user-space dereference.
+
+For the details of TYPE, see :ref:`kprobetrace documentation <kprobetrace_types>`.
+
+Usage examples
+--------------
+Here is an example to add a wprobe event on a variable `jiffies`.
+::
+
+  # echo 'w:my_jiffies w@jiffies' >> dynamic_events
+  # cat dynamic_events
+  w:wprobes/my_jiffies w@jiffies
+  # echo 1 > events/wprobes/enable
+  # cat trace | head
+  #           TASK-PID     CPU#  |||||  TIMESTAMP  FUNCTION
+  #              | |         |   |||||     |         |
+           <idle>-0       [000] d.Z1.  717.026259: my_jiffies: (tick_do_update_jiffies64+0xbe/0x130)
+           <idle>-0       [000] d.Z1.  717.026373: my_jiffies: (tick_do_update_jiffies64+0xbe/0x130)
+
+You can see the code which writes to `jiffies` is `tick_do_update_jiffies64()`.
diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h
index 5cbd09c8be8d..43ffd9a76d88 100644
--- a/include/linux/trace_events.h
+++ b/include/linux/trace_events.h
@@ -337,6 +337,7 @@ enum {
 	TRACE_EVENT_FL_UPROBE_BIT,
 	TRACE_EVENT_FL_EPROBE_BIT,
 	TRACE_EVENT_FL_FPROBE_BIT,
+	TRACE_EVENT_FL_WPROBE_BIT,
 	TRACE_EVENT_FL_CUSTOM_BIT,
 	TRACE_EVENT_FL_TEST_STR_BIT,
 };
@@ -367,6 +368,7 @@ enum {
 	TRACE_EVENT_FL_UPROBE		= (1 << TRACE_EVENT_FL_UPROBE_BIT),
 	TRACE_EVENT_FL_EPROBE		= (1 << TRACE_EVENT_FL_EPROBE_BIT),
 	TRACE_EVENT_FL_FPROBE		= (1 << TRACE_EVENT_FL_FPROBE_BIT),
+	TRACE_EVENT_FL_WPROBE		= (1 << TRACE_EVENT_FL_WPROBE_BIT),
 	TRACE_EVENT_FL_CUSTOM		= (1 << TRACE_EVENT_FL_CUSTOM_BIT),
 	TRACE_EVENT_FL_TEST_STR		= (1 << TRACE_EVENT_FL_TEST_STR_BIT),
 };
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 0ab5916575a9..b58c2565024f 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -862,6 +862,19 @@ config EPROBE_EVENTS
 	  convert the type of an event field. For example, turn an
 	  address into a string.
 
+config WPROBE_EVENTS
+	bool "Enable wprobe-based dynamic events"
+	depends on TRACING
+	depends on HAVE_HW_BREAKPOINT
+	select PROBE_EVENTS
+	select DYNAMIC_EVENTS
+	help
+	  This allows the user to add watchpoint tracing events based on
+	  hardware breakpoints on the fly via the ftrace interface.
+
+	  Those events can be inserted wherever hardware breakpoints can be
+	  set, and record accessed memory address and values.
+
 config BPF_EVENTS
 	depends on BPF_SYSCALL
 	depends on (KPROBE_EVENTS || UPROBE_EVENTS) && PERF_EVENTS
diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile
index f934ff586bd4..141c8323de20 100644
--- a/kernel/trace/Makefile
+++ b/kernel/trace/Makefile
@@ -126,6 +126,7 @@ obj-$(CONFIG_FTRACE_RECORD_RECURSION) += trace_recursion_record.o
 obj-$(CONFIG_FPROBE) += fprobe.o
 obj-$(CONFIG_RETHOOK) += rethook.o
 obj-$(CONFIG_FPROBE_EVENTS) += trace_fprobe.o
+obj-$(CONFIG_WPROBE_EVENTS) += trace_wprobe.o
 
 obj-$(CONFIG_TRACEPOINT_BENCHMARK) += trace_benchmark.o
 obj-$(CONFIG_RV) += rv/
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 19cc07360005..4ebece96d8b7 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -4294,8 +4294,12 @@ static const char readme_msg[] =
 	"  uprobe_events\t\t- Create/append/remove/show the userspace dynamic events\n"
 	"\t\t\t  Write into this file to define/undefine new trace events.\n"
 #endif
+#ifdef CONFIG_WPROBE_EVENTS
+	"  wprobe_events\t\t- Create/append/remove/show the hardware breakpoint dynamic events\n"
+	"\t\t\t  Write into this file to define/undefine new trace events.\n"
+#endif
 #if defined(CONFIG_KPROBE_EVENTS) || defined(CONFIG_UPROBE_EVENTS) || \
-    defined(CONFIG_FPROBE_EVENTS)
+    defined(CONFIG_FPROBE_EVENTS) || defined(CONFIG_WPROBE_EVENTS)
 	"\t  accepts: event-definitions (one definition per line)\n"
 #if defined(CONFIG_KPROBE_EVENTS) || defined(CONFIG_UPROBE_EVENTS)
 	"\t   Format: p[:[<group>/][<event>]] <place> [<args>]\n"
@@ -4305,6 +4309,9 @@ static const char readme_msg[] =
 	"\t           f[:[<group>/][<event>]] <func-name>[%return] [<args>]\n"
 	"\t           t[:[<group>/][<event>]] <tracepoint> [<args>]\n"
 #endif
+#ifdef CONFIG_WPROBE_EVENTS
+	"\t           w[:[<group>/][<event>]] [r|w|rw]@<addr>[:<len>]\n"
+#endif
 #ifdef CONFIG_HIST_TRIGGERS
 	"\t           s:[synthetic/]<event> <field> [<field>]\n"
 #endif
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index bf77331f56a4..64851a8d021f 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -179,6 +179,11 @@ struct fexit_trace_entry_head {
 	unsigned long		ret_ip;
 };
 
+struct wprobe_trace_entry_head {
+	struct trace_entry	ent;
+	unsigned long		ip;
+};
+
 #define TRACE_BUF_SIZE		1024
 
 struct trace_array;
diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
index 5552ce7af5a1..9f4cad18977a 100644
--- a/kernel/trace/trace_probe.c
+++ b/kernel/trace/trace_probe.c
@@ -1402,6 +1402,23 @@ static int parse_probe_vars(char *orig_arg, const struct fetch_type *t,
 			return 0;
 	}
 
+	/* wprobe only support "$addr" and "$value" variable */
+	if (ctx->flags & TPARG_FL_WPROBE) {
+		if (!strcmp(arg, "addr")) {
+			code->op = FETCH_OP_BADDR;
+			return 0;
+		}
+		if (!strcmp(arg, "value")) {
+			code->op = FETCH_OP_BADDR;
+			code++;
+			code->op = FETCH_OP_DEREF;
+			code->offset = 0;
+			*pcode = code;
+			return 0;
+		}
+		goto inval;
+	}
+
 	if (strcmp(arg, "comm") == 0 || strcmp(arg, "COMM") == 0) {
 		code->op = FETCH_OP_COMM;
 		return 0;
@@ -1461,8 +1478,8 @@ static int parse_probe_arg_register(char *arg, struct fetch_insn *code,
 {
 	int ret;
 
-	if (ctx->flags & (TPARG_FL_TEVENT | TPARG_FL_FPROBE)) {
-		/* eprobe and fprobe do not handle registers */
+	if (ctx->flags & (TPARG_FL_TEVENT | TPARG_FL_FPROBE | TPARG_FL_WPROBE)) {
+		/* eprobe, fprobe and wprobe do not handle registers */
 		trace_probe_log_err(ctx->offset, BAD_VAR);
 		return -EINVAL;
 	}
diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h
index fba1af092a9b..6543d4c2cda5 100644
--- a/kernel/trace/trace_probe.h
+++ b/kernel/trace/trace_probe.h
@@ -90,6 +90,7 @@ typedef int (*print_type_func_t)(struct trace_seq *, void *, void *);
 	FETCH_OP(STACK, param),		/* Stack: .param = index */	\
 	FETCH_OP(STACKP, none),		/* Stack pointer */		\
 	FETCH_OP(RETVAL, none),		/* Return value */		\
+	FETCH_OP(BADDR, none),		/* Break address */		\
 	FETCH_OP(IMM, imm),		/* Immediate: .immediate */	\
 	FETCH_OP(COMM, none),		/* Current comm */		\
 	FETCH_OP(CURRENT, none),	/* Current task_struct address */\
@@ -418,6 +419,7 @@ static inline int traceprobe_get_entry_data_size(struct trace_probe *tp)
 #define TPARG_FL_USER   BIT(4)
 #define TPARG_FL_FPROBE BIT(5)
 #define TPARG_FL_TPOINT BIT(6)
+#define TPARG_FL_WPROBE BIT(7)
 #define TPARG_FL_LOC_MASK	GENMASK(4, 0)
 
 static inline bool tparg_is_function_entry(unsigned int flags)
@@ -544,6 +546,10 @@ extern int traceprobe_define_arg_fields(struct trace_event_call *event_call,
 	C(ARG_TOO_LONG,		"Argument expression is too long"),		\
 	C(ARRAY_NO_CLOSE,	"Array is not closed"),		\
 	C(ARRAY_TOO_BIG,	"Array number is too big"),		\
+	C(BAD_ACCESS_ADDR,	"Invalid access memory address"),		\
+	C(BAD_ACCESS_FMT,	"Access memory address requires @"),		\
+	C(BAD_ACCESS_LEN,	"This memory access length is not supported"),	\
+	C(BAD_ACCESS_TYPE,	"Bad memory access type"),			\
 	C(BAD_ADDR_SUFFIX,	"Invalid probed address suffix"),		\
 	C(BAD_ARG_NAME,		"Argument name must follow the same rules as C identifiers"),	\
 	C(BAD_ARG_NUM,		"Invalid argument number"),		\
@@ -626,7 +632,9 @@ extern int traceprobe_define_arg_fields(struct trace_event_call *event_call,
 	C(TYPECAST_NOT_EVENT,	"Typecasts are only for eprobe fields"),	\
 	C(TYPECAST_REQ_FIELD,	"Typecast requires a field access"),	\
 	C(TYPECAST_SYM_OFFSET,	"@SYM+/-OFFSET with typecast needs parentheses"),	\
-	C(USED_ARG_NAME,	"This argument name is already used"),
+	C(USED_ARG_NAME,	"This argument name is already used"),		\
+	C(WPROBE_NO_MAXACT,	"Watchpoint probe does not support maxactive"),	\
+	C(WPROBE_NO_SIBLING,	"Watchpoint probe does not support sibling probes"),
 
 #undef C
 #define C(a, b)		TP_ERR_##a
diff --git a/kernel/trace/trace_wprobe.c b/kernel/trace/trace_wprobe.c
new file mode 100644
index 000000000000..df592d9280a4
--- /dev/null
+++ b/kernel/trace/trace_wprobe.c
@@ -0,0 +1,765 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Hardware-breakpoint-based tracing events
+ *
+ * Copyright (C) 2023, Masami Hiramatsu <mhiramat@kernel.org>
+ */
+#define pr_fmt(fmt)	"trace_wprobe: " fmt
+
+#include <linux/compiler.h>
+#include <linux/hw_breakpoint.h>
+#include <linux/kallsyms.h>
+#include <linux/list.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/perf_event.h>
+#include <linux/rculist.h>
+#include <linux/security.h>
+#include <linux/tracepoint.h>
+#include <linux/uaccess.h>
+
+#include <asm/ptrace.h>
+
+#include "trace_dynevent.h"
+#include "trace_probe.h"
+#include "trace_probe_kernel.h"
+#include "trace_probe_tmpl.h"
+#include "trace_output.h"
+
+#define WPROBE_EVENT_SYSTEM "wprobes"
+
+static int trace_wprobe_create(const char *raw_command);
+static int trace_wprobe_show(struct seq_file *m, struct dyn_event *ev);
+static int trace_wprobe_release(struct dyn_event *ev);
+static bool trace_wprobe_is_busy(struct dyn_event *ev);
+static bool trace_wprobe_match(const char *system, const char *event,
+			       int argc, const char **argv, struct dyn_event *ev);
+
+static struct dyn_event_operations trace_wprobe_ops = {
+	.create = trace_wprobe_create,
+	.show = trace_wprobe_show,
+	.is_busy = trace_wprobe_is_busy,
+	.free = trace_wprobe_release,
+	.match = trace_wprobe_match,
+};
+
+struct trace_wprobe {
+	struct dyn_event	devent;
+	struct perf_event * __percpu *bp_event;
+	unsigned long		addr;
+	int			len;
+	int			type;
+	const char		*symbol;
+	struct trace_probe	tp;
+};
+
+static bool is_trace_wprobe(struct dyn_event *ev)
+{
+	return ev->ops == &trace_wprobe_ops;
+}
+
+static struct trace_wprobe *to_trace_wprobe(struct dyn_event *ev)
+{
+	return container_of(ev, struct trace_wprobe, devent);
+}
+
+#define for_each_trace_wprobe(pos, dpos)			\
+	for_each_dyn_event(dpos)				\
+		if (is_trace_wprobe(dpos) && (pos = to_trace_wprobe(dpos)))
+
+static bool trace_wprobe_is_busy(struct dyn_event *ev)
+{
+	struct trace_wprobe *tw = to_trace_wprobe(ev);
+
+	return trace_probe_is_enabled(&tw->tp);
+}
+
+static bool trace_wprobe_match(const char *system, const char *event,
+			       int argc, const char **argv, struct dyn_event *ev)
+{
+	struct trace_wprobe *tw = to_trace_wprobe(ev);
+
+	if (event[0] != '\0' && strcmp(trace_probe_name(&tw->tp), event))
+		return false;
+
+	if (system && strcmp(trace_probe_group_name(&tw->tp), system))
+		return false;
+
+	return trace_probe_match_command_args(&tw->tp, argc, argv);
+}
+
+/*
+ * Note that we don't verify the fetch_insn code, since it does not come
+ * from user space.
+ */
+static int
+process_fetch_insn(struct fetch_insn *code, void *rec, void *edata,
+		   void *dest, void *base)
+{
+	void *baddr = rec;
+	unsigned long val;
+	int ret;
+
+retry:
+	/* 1st stage: get value from context */
+	switch (code->op) {
+	case FETCH_OP_BADDR:
+		val = (unsigned long)baddr;
+		break;
+	case FETCH_NOP_SYMBOL:	/* Ignore a place holder */
+		code++;
+		goto retry;
+	default:
+		ret = process_common_fetch_insn(code, &val);
+		if (ret < 0)
+			return ret;
+	}
+	code++;
+
+	return process_fetch_insn_bottom(code, val, dest, base);
+}
+NOKPROBE_SYMBOL(process_fetch_insn)
+
+static void wprobe_trace_handler(struct trace_wprobe *tw,
+				 unsigned long addr,
+				 struct pt_regs *regs,
+				 struct trace_event_file *trace_file)
+{
+	struct wprobe_trace_entry_head *entry;
+	struct trace_event_call *call = trace_probe_event_call(&tw->tp);
+	struct trace_event_buffer fbuffer;
+	int dsize;
+
+	if (WARN_ON_ONCE(call != trace_file->event_call))
+		return;
+
+	if (trace_trigger_soft_disabled(trace_file))
+		return;
+
+	if (READ_ONCE(tw->addr) != addr)
+		return;
+
+	dsize = __get_data_size(&tw->tp, (void *)addr, NULL);
+
+	entry = trace_event_buffer_reserve(&fbuffer, trace_file,
+					   sizeof(*entry) + tw->tp.size + dsize);
+	if (!entry)
+		return;
+
+	entry->ip = instruction_pointer(regs);
+	store_trace_args(&entry[1], &tw->tp, (void *)addr, NULL, sizeof(*entry), dsize);
+
+	fbuffer.regs = regs;
+	trace_event_buffer_commit(&fbuffer);
+}
+
+static void wprobe_perf_handler(struct perf_event *bp,
+			      struct perf_sample_data *data,
+			      struct pt_regs *regs)
+{
+	struct trace_wprobe *tw = bp->overflow_handler_context;
+	struct event_file_link *link;
+	unsigned long addr = bp->attr.bp_addr;
+
+	trace_probe_for_each_link_rcu(link, &tw->tp)
+		wprobe_trace_handler(tw, addr, regs, link->file);
+}
+
+static int __register_trace_wprobe(struct trace_wprobe *tw)
+{
+	struct perf_event_attr attr;
+	int i, ret;
+
+	if (tw->bp_event)
+		return -EINVAL;
+
+	for (i = 0; i < tw->tp.nr_args; i++) {
+		ret = traceprobe_update_arg(&tw->tp.args[i]);
+		if (ret)
+			return ret;
+	}
+
+	hw_breakpoint_init(&attr);
+	attr.bp_addr = tw->addr;
+	attr.bp_len = tw->len;
+	attr.bp_type = tw->type;
+
+	tw->bp_event = register_wide_hw_breakpoint(&attr, wprobe_perf_handler, tw);
+	if (IS_ERR_PCPU(tw->bp_event)) {
+		int ret = PTR_ERR_PCPU(tw->bp_event);
+
+		tw->bp_event = NULL;
+		return ret;
+	}
+
+	return 0;
+}
+
+static void __unregister_trace_wprobe(struct trace_wprobe *tw)
+{
+	if (tw->bp_event) {
+		unregister_wide_hw_breakpoint(tw->bp_event);
+		tw->bp_event = NULL;
+	}
+}
+
+static void free_trace_wprobe(struct trace_wprobe *tw)
+{
+	if (tw) {
+		trace_probe_cleanup(&tw->tp);
+		kfree(tw->symbol);
+		kfree(tw);
+	}
+}
+DEFINE_FREE(free_trace_wprobe, struct trace_wprobe *,
+	if (!IS_ERR_OR_NULL(_T))
+		free_trace_wprobe(_T))
+
+
+static struct trace_wprobe *alloc_trace_wprobe(const char *group,
+					       const char *event,
+					       const char *symbol,
+					       unsigned long addr,
+					       int len, int type, int nargs)
+{
+	struct trace_wprobe *tw __free(free_trace_wprobe) = NULL;
+	int ret;
+
+	tw = kzalloc_flex(*tw, tp.args, nargs);
+	if (!tw)
+		return ERR_PTR(-ENOMEM);
+
+	if (symbol) {
+		tw->symbol = kstrdup(symbol, GFP_KERNEL);
+		if (!tw->symbol)
+			return ERR_PTR(-ENOMEM);
+	}
+	tw->addr = addr;
+	tw->len = len;
+	tw->type = type;
+
+	ret = trace_probe_init(&tw->tp, event, group, false, nargs);
+	if (ret < 0)
+		return ERR_PTR(ret);
+
+	dyn_event_init(&tw->devent, &trace_wprobe_ops);
+	return_ptr(tw);
+}
+
+static struct trace_wprobe *find_trace_wprobe(const char *event,
+					      const char *group)
+{
+	struct dyn_event *pos;
+	struct trace_wprobe *tw;
+
+	for_each_trace_wprobe(tw, pos)
+		if (strcmp(trace_probe_name(&tw->tp), event) == 0 &&
+		    strcmp(trace_probe_group_name(&tw->tp), group) == 0)
+			return tw;
+	return NULL;
+}
+
+static enum print_line_t
+print_wprobe_event(struct trace_iterator *iter, int flags,
+		   struct trace_event *event)
+{
+	struct wprobe_trace_entry_head *field;
+	struct trace_seq *s = &iter->seq;
+	struct trace_probe *tp;
+
+	field = (struct wprobe_trace_entry_head *)iter->ent;
+	tp = trace_probe_primary_from_call(
+		container_of(event, struct trace_event_call, event));
+	if (WARN_ON_ONCE(!tp))
+		goto out;
+
+	trace_seq_printf(s, "%s: (", trace_probe_name(tp));
+
+	if (!seq_print_ip_sym_offset(s, field->ip, flags))
+		goto out;
+
+	trace_seq_putc(s, ')');
+
+	if (trace_probe_print_args(s, tp->args, tp->nr_args,
+			     (u8 *)&field[1], field) < 0)
+		goto out;
+
+	trace_seq_putc(s, '\n');
+out:
+	return trace_handle_return(s);
+}
+
+static int wprobe_event_define_fields(struct trace_event_call *event_call)
+{
+	int ret;
+	struct wprobe_trace_entry_head field;
+	struct trace_probe *tp;
+
+	tp = trace_probe_primary_from_call(event_call);
+	if (WARN_ON_ONCE(!tp))
+		return -ENOENT;
+
+	DEFINE_FIELD(unsigned long, ip, FIELD_STRING_IP, 0);
+
+	return traceprobe_define_arg_fields(event_call, sizeof(field), tp);
+}
+
+static struct trace_event_functions wprobe_funcs = {
+	.trace	= print_wprobe_event
+};
+
+static struct trace_event_fields wprobe_fields_array[] = {
+	{ .type = TRACE_FUNCTION_TYPE,
+	  .define_fields = wprobe_event_define_fields },
+	{}
+};
+
+static int wprobe_register(struct trace_event_call *event,
+			   enum trace_reg type, void *data);
+
+static inline void init_trace_event_call(struct trace_wprobe *tw)
+{
+	struct trace_event_call *call = trace_probe_event_call(&tw->tp);
+
+	call->event.funcs = &wprobe_funcs;
+	call->class->fields_array = wprobe_fields_array;
+	call->flags = TRACE_EVENT_FL_WPROBE;
+	call->class->reg = wprobe_register;
+}
+
+static int register_wprobe_event(struct trace_wprobe *tw)
+{
+	init_trace_event_call(tw);
+	return trace_probe_register_event_call(&tw->tp);
+}
+
+static int register_trace_wprobe_event(struct trace_wprobe *tw)
+{
+	struct trace_wprobe *old_tw;
+	int ret;
+
+	guard(mutex)(&event_mutex);
+
+	old_tw = find_trace_wprobe(trace_probe_name(&tw->tp),
+				   trace_probe_group_name(&tw->tp));
+	if (old_tw) {
+		/*
+		 * Wprobe does not support sibling probes because the event
+		 * trigger (set_wprobe/clear_wprobe) identifies the target
+		 * wprobe by its event name. Having multiple wprobes sharing
+		 * the same event name would make the target ambiguous.
+		 */
+		trace_probe_log_set_index(0);
+		trace_probe_log_err(0, WPROBE_NO_SIBLING);
+		return -EBUSY;
+	}
+
+	ret = register_wprobe_event(tw);
+	if (ret) {
+		trace_probe_log_set_index(0);
+		if (ret == -EEXIST)
+			trace_probe_log_err(0, EVENT_EXIST);
+		else if (ret != -ENOMEM)
+			trace_probe_log_err(0, FAIL_REG_PROBE);
+		return ret;
+	}
+
+	dyn_event_add(&tw->devent, trace_probe_event_call(&tw->tp));
+	return 0;
+}
+static int unregister_wprobe_event(struct trace_wprobe *tw)
+{
+	return trace_probe_unregister_event_call(&tw->tp);
+}
+
+static int unregister_trace_wprobe(struct trace_wprobe *tw)
+{
+	if (trace_probe_has_sibling(&tw->tp))
+		goto unreg;
+
+	if (trace_probe_is_enabled(&tw->tp))
+		return -EBUSY;
+
+	if (trace_event_dyn_busy(trace_probe_event_call(&tw->tp)))
+		return -EBUSY;
+
+	if (unregister_wprobe_event(tw))
+		return -EBUSY;
+
+unreg:
+	__unregister_trace_wprobe(tw);
+	dyn_event_remove(&tw->devent);
+	trace_probe_unlink(&tw->tp);
+
+	return 0;
+}
+
+static int enable_trace_wprobe(struct trace_event_call *call,
+			       struct trace_event_file *file)
+{
+	struct trace_probe *tp;
+	struct trace_wprobe *tw;
+	bool enabled;
+	int ret = 0;
+
+	tp = trace_probe_primary_from_call(call);
+	if (WARN_ON_ONCE(!tp))
+		return -ENODEV;
+	enabled = trace_probe_is_enabled(tp);
+
+	if (file) {
+		ret = trace_probe_add_file(tp, file);
+		if (ret)
+			return ret;
+	} else {
+		trace_probe_set_flag(tp, TP_FLAG_PROFILE);
+	}
+
+	if (!enabled) {
+		list_for_each_entry(tw, trace_probe_probe_list(tp), tp.list) {
+			ret = __register_trace_wprobe(tw);
+			if (ret < 0) {
+				struct trace_wprobe *tmp;
+
+				list_for_each_entry(tmp, trace_probe_probe_list(tp), tp.list) {
+					if (tmp == tw)
+						break;
+					__unregister_trace_wprobe(tmp);
+				}
+				if (file)
+					trace_probe_remove_file(tp, file);
+				else
+					trace_probe_clear_flag(tp, TP_FLAG_PROFILE);
+				return ret;
+			}
+		}
+	}
+
+	return 0;
+}
+
+static int disable_trace_wprobe(struct trace_event_call *call,
+				struct trace_event_file *file)
+{
+	struct trace_wprobe *tw;
+	struct trace_probe *tp;
+
+	tp = trace_probe_primary_from_call(call);
+	if (WARN_ON_ONCE(!tp))
+		return -ENODEV;
+
+	if (file) {
+		if (!trace_probe_get_file_link(tp, file))
+			return -ENOENT;
+		if (!trace_probe_has_single_file(tp))
+			goto out;
+		trace_probe_clear_flag(tp, TP_FLAG_TRACE);
+	} else {
+		trace_probe_clear_flag(tp, TP_FLAG_PROFILE);
+	}
+
+	if (!trace_probe_is_enabled(tp)) {
+		list_for_each_entry(tw, trace_probe_probe_list(tp), tp.list) {
+			__unregister_trace_wprobe(tw);
+		}
+	}
+
+out:
+	if (file)
+		trace_probe_remove_file(tp, file);
+
+	return 0;
+}
+
+static int wprobe_register(struct trace_event_call *event,
+			   enum trace_reg type, void *data)
+{
+	struct trace_event_file *file = data;
+
+	switch (type) {
+	case TRACE_REG_REGISTER:
+		return enable_trace_wprobe(event, file);
+	case TRACE_REG_UNREGISTER:
+		return disable_trace_wprobe(event, file);
+
+#ifdef CONFIG_PERF_EVENTS
+	case TRACE_REG_PERF_REGISTER:
+	case TRACE_REG_PERF_UNREGISTER:
+	case TRACE_REG_PERF_OPEN:
+	case TRACE_REG_PERF_CLOSE:
+	case TRACE_REG_PERF_ADD:
+	case TRACE_REG_PERF_DEL:
+		return -EOPNOTSUPP;
+#endif
+	}
+	return 0;
+}
+
+static int parse_address_spec(const char *spec, unsigned long *addr, int *type,
+			      int *len, char **symbol)
+{
+	char *_spec __free(kfree) = NULL;
+	int _len = HW_BREAKPOINT_LEN_4;
+	int _type = HW_BREAKPOINT_RW;
+	unsigned long _addr = 0;
+	char *at, *col;
+
+	_spec = kstrdup(spec, GFP_KERNEL);
+	if (!_spec)
+		return -ENOMEM;
+
+	at = strchr(_spec, '@');
+	col = strchr(_spec, ':');
+
+	if (!at) {
+		trace_probe_log_err(0, BAD_ACCESS_FMT);
+		return -EINVAL;
+	}
+
+	if (at != _spec) {
+		*at = '\0';
+
+		if (strcmp(_spec, "r") == 0)
+			_type = HW_BREAKPOINT_R;
+		else if (strcmp(_spec, "w") == 0)
+			_type = HW_BREAKPOINT_W;
+		else if (strcmp(_spec, "rw") == 0)
+			_type = HW_BREAKPOINT_RW;
+		else {
+			trace_probe_log_err(0, BAD_ACCESS_TYPE);
+			return -EINVAL;
+		}
+	}
+
+	if (col) {
+		*col = '\0';
+		if (kstrtoint(col + 1, 0, &_len)) {
+			trace_probe_log_err(col + 1 - _spec, BAD_ACCESS_LEN);
+			return -EINVAL;
+		}
+
+		switch (_len) {
+		case 1:
+			_len = HW_BREAKPOINT_LEN_1;
+			break;
+		case 2:
+			_len = HW_BREAKPOINT_LEN_2;
+			break;
+		case 4:
+			_len = HW_BREAKPOINT_LEN_4;
+			break;
+		case 8:
+			_len = HW_BREAKPOINT_LEN_8;
+			break;
+		default:
+			trace_probe_log_err(col + 1 - _spec, BAD_ACCESS_LEN);
+			return -EINVAL;
+		}
+	}
+
+	if (kstrtoul(at + 1, 0, &_addr) != 0) {
+		char *off_str = strpbrk(at + 1, "+-");
+		int offset = 0;
+
+		if (off_str) {
+			if (kstrtoint(off_str, 0, &offset) != 0) {
+				trace_probe_log_err(off_str - _spec, BAD_PROBE_ADDR);
+				return -EINVAL;
+			}
+			*off_str = '\0';
+		}
+		_addr = kallsyms_lookup_name(at + 1);
+		if (!_addr) {
+			trace_probe_log_err(at + 1 - _spec, BAD_ACCESS_ADDR);
+			return -ENOENT;
+		}
+		_addr += offset;
+		*symbol = kstrdup(at + 1, GFP_KERNEL);
+		if (!*symbol)
+			return -ENOMEM;
+	}
+
+	if (_addr != 0 && _addr < TASK_SIZE) {
+		trace_probe_log_err(at + 1 - _spec, BAD_ACCESS_ADDR);
+		return -EINVAL;
+	}
+
+	*addr = _addr;
+	*type = _type;
+	*len = _len;
+	return 0;
+}
+
+static int __trace_wprobe_create(int argc, const char *argv[])
+{
+	/*
+	 * Argument syntax:
+	 *  w[:[GRP/][EVENT]] SPEC
+	 *
+	 * SPEC:
+	 *  [r|w|rw]@[ADDR|SYMBOL[+OFFS]][:LEN]
+	 */
+	struct traceprobe_parse_context *ctx __free(traceprobe_parse_context) = NULL;
+	struct trace_wprobe *tw __free(free_trace_wprobe) = NULL;
+	const char *event = NULL, *group = WPROBE_EVENT_SYSTEM;
+	const char *tplog __free(trace_probe_log_clear) = NULL;
+	char *symbol __free(kfree) = NULL;
+	char *gbuf __free(kfree) = NULL;
+	char *ebuf __free(kfree) = NULL;
+	unsigned long addr;
+	int len, type, i;
+	int ret;
+
+	if (argv[0][0] != 'w')
+		return -ECANCELED;
+
+	tplog = trace_probe_log_init("wprobe", argc, argv);
+
+	if (argc < 2) {
+		trace_probe_log_set_index(0);
+		trace_probe_log_err(0, NO_ARG_BODY);
+		return -EINVAL;
+	}
+
+	if (argv[0][1] != '\0') {
+		if (argv[0][1] != ':') {
+			trace_probe_log_set_index(0);
+			trace_probe_log_err(1, WPROBE_NO_MAXACT);
+			return -EINVAL;
+		}
+		event = &argv[0][2];
+	}
+
+	trace_probe_log_set_index(1);
+	ret = parse_address_spec(argv[1], &addr, &type, &len, &symbol);
+	if (ret < 0)
+		return ret;
+
+	trace_probe_log_set_index(0);
+	if (event) {
+		gbuf = kmalloc(MAX_EVENT_NAME_LEN, GFP_KERNEL);
+		if (!gbuf)
+			return -ENOMEM;
+		ret = traceprobe_parse_event_name(&event, &group, gbuf,
+						  event - argv[0]);
+		if (ret)
+			return ret;
+	}
+
+	if (!event) {
+		/* Make a new event name */
+		ebuf = kmalloc(MAX_EVENT_NAME_LEN, GFP_KERNEL);
+		if (!ebuf)
+			return -ENOMEM;
+		if (symbol)
+			snprintf(ebuf, MAX_EVENT_NAME_LEN, "%s", symbol);
+		else
+			snprintf(ebuf, MAX_EVENT_NAME_LEN, "w_0x%lx", addr);
+		sanitize_event_name(ebuf);
+		event = ebuf;
+	}
+
+	argc -= 2; argv += 2;
+	if (argc > MAX_TRACE_ARGS) {
+		trace_probe_log_set_index(2);
+		trace_probe_log_err(0, TOO_MANY_ARGS);
+		return -E2BIG;
+	}
+	tw = alloc_trace_wprobe(group, event, symbol, addr, len, type, argc);
+	if (IS_ERR(tw))
+		return PTR_ERR(tw);
+
+	ctx = kzalloc_obj(*ctx);
+	if (!ctx)
+		return -ENOMEM;
+
+	ctx->flags = TPARG_FL_KERNEL | TPARG_FL_WPROBE;
+
+	/* parse arguments */
+	for (i = 0; i < argc; i++) {
+		trace_probe_log_set_index(i + 2);
+		ctx->offset = 0;
+		ret = traceprobe_parse_probe_arg(&tw->tp, i, argv[i], ctx);
+		if (ret)
+			return ret;	/* This can be -ENOMEM */
+	}
+
+	ret = traceprobe_set_print_fmt(&tw->tp, PROBE_PRINT_NORMAL);
+	if (ret < 0)
+		return ret;
+
+	ret = register_trace_wprobe_event(tw);
+	if (!ret)
+		tw = NULL; /* To avoid free */
+
+	return ret;
+}
+
+static int trace_wprobe_create(const char *raw_command)
+{
+	return trace_probe_create(raw_command, __trace_wprobe_create);
+}
+
+static int trace_wprobe_release(struct dyn_event *ev)
+{
+	struct trace_wprobe *tw = to_trace_wprobe(ev);
+	int ret = unregister_trace_wprobe(tw);
+
+	if (!ret)
+		free_trace_wprobe(tw);
+	return ret;
+}
+
+static int trace_wprobe_show(struct seq_file *m, struct dyn_event *ev)
+{
+	struct trace_wprobe *tw = to_trace_wprobe(ev);
+	int i;
+
+	seq_printf(m, "w:%s/%s", trace_probe_group_name(&tw->tp),
+		   trace_probe_name(&tw->tp));
+
+	const char *type_str;
+
+	if (tw->type == HW_BREAKPOINT_R)
+		type_str = "r";
+	else if (tw->type == HW_BREAKPOINT_W)
+		type_str = "w";
+	else
+		type_str = "rw";
+
+	int len;
+
+	if (tw->len == HW_BREAKPOINT_LEN_1)
+		len = 1;
+	else if (tw->len == HW_BREAKPOINT_LEN_2)
+		len = 2;
+	else if (tw->len == HW_BREAKPOINT_LEN_4)
+		len = 4;
+	else
+		len = 8;
+
+	if (tw->symbol) {
+		unsigned long sym_addr = kallsyms_lookup_name(tw->symbol);
+		long offset = sym_addr ? (long)(tw->addr - sym_addr) : 0;
+
+		if (offset)
+			seq_printf(m, " %s@%s%+ld:%d", type_str, tw->symbol, offset, len);
+		else
+			seq_printf(m, " %s@%s:%d", type_str, tw->symbol, len);
+	} else {
+		seq_printf(m, " %s@0x%lx:%d", type_str, tw->addr, len);
+	}
+
+	for (i = 0; i < tw->tp.nr_args; i++)
+		seq_printf(m, " %s=%s", tw->tp.args[i].name, tw->tp.args[i].comm);
+	seq_putc(m, '\n');
+
+	return 0;
+}
+
+static __init int init_wprobe_trace(void)
+{
+	return dyn_event_register(&trace_wprobe_ops);
+}
+fs_initcall(init_wprobe_trace);
+