[PATCH v15 00/12] tracing: wprobe: x86: Add wprobe for watchpoint

[PATCH v15 00/12] tracing: wprobe: x86: Add wprobe for watchpoint

[Masami Hiramatsu (Google)]

Hi,

Here is the 15th version of the series for adding new wprobe (watch probe)
which provides memory access tracing event. Moreover, this can be used
via event trigger. Thus it can trace memory access on dynamically
allocated objects too.
The previous version is here:

  https://lore.kernel.org/all/178810001186.64882.2161016469449127450.stgit@devnote2/

In this version, previous bugfix patches for BTF kflag resolution and
RCU-protected kprobe blacklist were sent to Linus via probe/fixes, reducing
the series to 12 patches. This version addresses feedbacks from Sashiko on
v14[1], and more local fixes such as x86 debug register manipulation, validates
watched address and natural alignment, tracks missed events on SMP update
failures(*), prevents in-place command string modification during trigger
parsing, adds explicit failure checks in selftests, and documents BTF
typecast and struct offset syntax. I also added Assited-by: tags for this
update.

[1] https://sashiko.dev/#/patchset/178810001186.64882.2161016469449127450.stgit%40devnote2
(*) currently it just increase a missed counter.

Detailed changes are here.

Changes in v15:
 - x86/mce: Move local_db_save() to entry of exc_machine_check_kernel()
   and restore it on early return from mce_check_crashing_cpu() to
   prevent nested #DB on watched variables.
 - x86/hw_breakpoints: Always preserve DR7_FIXED_1 in
   arch_install_hw_breakpoint(), arch_uninstall_hw_breakpoint(), and
   hw_breakpoint_restore() for architectural compliance.
 - x86/hw_breakpoints: Wrap local_db_save() in a cpu_dr7_seq loop to
   detect NMI breakpoint updates and ensure DR7 is disabled before entry.
 - x86/hw_breakpoints: In local_db_restore(), restore DR7_FIXED_1 if
   saved dr7 is 0 and an NMI updated breakpoints, preserving KVM guest
   isolation.
 - x86/hw_breakpoints: Always write "val | DR7_FIXED_1" to hardware DR7
   in local_db_restore() for architectural compliance.
 - x86/hw_breakpoints: Avoid modifying saved dr7 in-place across retry
   loops.
 - x86/hw_breakpoints: Temporarily clear breakpoint enable bit in DR7
   before updating debug address register and re-enable it afterward to
   comply with x86 specification and avoid spurious #DBs.
 - HWBP: Annotate counter_arch_bp(bp)->address and bp->attr.bp_addr with
   WRITE_ONCE() in both update and rollback paths to prevent data races
   with concurrent readers (e.g. NMI handlers).
 - tracing/wprobe: Introduce trace_wprobe_is_valid_addr() to validate
   target address and natural alignment for wprobe length during event
   creation and trigger setup.
 - tracing/wprobe: Initialize irq_work and work immediately after
   allocation in alloc_trace_wprobe() and check tw->work.func in
   free_trace_wprobe() to prevent WARN_ON(!work->func) on early failures.
 - tracing/wprobe: Record SMP local update failures in tw->missed counter
   and expose missed event count as a trailing comment in trigger file.
 - tracing/wprobe: Duplicate field string in wprobe_trigger_typecast_parse()
   to avoid modifying glob in place so tracing_log_err() logs the pristine
   command string.
 - tracing/wprobe: Remove leftover offset and adjust debug print in
   wprobe_trigger_print().
 - tracing/wprobe: Add set_wprobe and clear_wprobe triggers to readme_msg
   in trace.c.
 - tracing/wprobe: Move variable declarations to function entry in
   trace_wprobe_show(), fix tab indentation in trace.c, and wrap lines
   exceeding 100 columns.
 - Documentation: Document BTF typecast in fetchargs and BTF struct
   offset resolution in set_wprobe trigger in wprobetrace.rst.
 - selftests/ftrace: Add explicit failure checks with fail helper across
   trigger-wprobe.tc, trigger-wprobe-btf-typecast.tc, and
   trigger-wprobe-btf-offset.tc.
 - selftests/ftrace: Declare fprobe README requirement in trigger tests
   and trigger file check in trigger-wprobe-syntax-errors.tc requires line.


Public branch
-------------
I will push this branch as topic/wprobe-v2 to my tree so that it
can be easily tested.

https://git.kernel.org/pub/scm/linux/kernel/git/mhiramat/linux.git/log/?h=topic/wprobe-v2

This is based on linux-trace tree's linux-trace/probes/fixes.

Usage
-----

The basic usage of this wprobe is similar to other probes;

  w:[GRP/][EVENT] [r|w|rw]@<ADDRESS|SYMBOL[+|-OFFS]>[:LEN] [FETCHARGS]

This defines a new wprobe event. For example, to trace jiffies update,
you can do;

 echo 'w:my_jiffies w@jiffies:8 value=+0($addr)' >> dynamic_events
 echo 1 > events/wprobes/my_jiffies/enable

Moreover, this can be combined with event trigger to trace the memory
access on slab objects. The trigger syntax is;

  set_wprobe:WPROBE_EVENT:FIELD[+|-OFFSET][:COUNT] [if FILTER]
  clear_wprobe:WPROBE_EVENT[:FIELD[+|-OFFSET][:COUNT]] [if FILTER]

set_wprobe sets WPROBE_EVENT's watch address on FIELD[+|-OFFSET].
clear_wprobe clears WPROBE_EVENT's watch address if it is set to
FIELD[+|-OFFSET]. If FIELD is omitted, forcibly clear the watch address
when trigger event is hit.

For example, trace the first 8 byte of the dentry data structure passed
to do_truncate() until it is deleted by dentry_kill().
(Note: all tracefs setup uses '>>' so that it does not kick do_truncate())

  # echo 'w:watch rw@-1:8 address=$addr value=+0($addr)' > dynamic_events

  # echo 'f:truncate do_truncate dentry=$arg2' >> dynamic_events
  # echo 'set_wprobe:watch:dentry' >> events/fprobes/truncate/trigger

  # echo 'f:dentry_kill dentry_kill dentry=$arg1' >> dynamic_events
  # echo 'clear_wprobe:watch:dentry' >> events/fprobes/dentry_kill/trigger

  # echo 1 >> events/fprobes/truncate/enable
  # echo 1 >> events/fprobes/dentry_kill/enable

  # echo aaa > /tmp/hoge
  # echo bbb > /tmp/hoge
  # echo ccc > /tmp/hoge
  # rm /tmp/hoge

Then, the trace data will show;

 # tracer: nop
 #
 # entries-in-buffer/entries-written: 32/32   #P:8
 #
 #                                _-----=> irqs-off/BH-disabled
 #                               / _----=> need-resched
 #                              | / _---=> hardirq/softirq
 #                              || / _--=> preempt-depth
 #                              ||| / _-=> migrate-disable
 #                              |||| /     delay
 #           TASK-PID     CPU#  |||||  TIMESTAMP  FUNCTION
 #              | |         |   |||||     |         |
               sh-107     [004] ...1.     9.990418: dentry_kill: (dentry_kill+0x0/0x2c0) dentry=0xffff888004ad6618
               sh-107     [004] ...1.     9.990914: dentry_kill: (dentry_kill+0x0/0x2c0) dentry=0xffff888004b3de78
               sh-107     [004] ...1.     9.993175: dentry_kill: (dentry_kill+0x0/0x2c0) dentry=0xffff8880049ddd40
               sh-107     [004] .....     9.995198: truncate: (do_truncate+0x4/0x120) dentry=0xffff8880048083a8
               sh-107     [004] ...1.     9.995389: dentry_kill: (dentry_kill+0x0/0x2c0) dentry=0xffff8880049db998
               sh-107     [004] ..Zff     9.997503: watch: (lookup_fast+0xaa/0x150) address=0xffff8880048083a8 value=0x8200080
               sh-107     [004] ..Zff     9.997509: watch: (path_openat+0x211/0xda0) address=0xffff8880048083a8 value=0x8200080
               sh-107     [004] ..Zff     9.997514: watch: (path_openat+0xa56/0xda0) address=0xffff8880048083a8 value=0x8200080
               sh-107     [004] ..Zff     9.997518: watch: (path_openat+0xae2/0xda0) address=0xffff8880048083a8 value=0x8200080
               sh-107     [004] .....     9.997521: truncate: (do_truncate+0x4/0x120) dentry=0xffff8880048083a8
               sh-107     [004] ...1.     9.997582: dentry_kill: (dentry_kill+0x0/0x2c0) dentry=0xffff888004808270
               sh-107     [004] ...1.     9.999365: dentry_kill: (dentry_kill+0x0/0x2c0) dentry=0xffff8880049db728
               sh-107     [004] ...1.     9.999388: dentry_kill: (dentry_kill+0x0/0x2c0) dentry=0xffff888004b1c000
               rm-113     [005] ..Zff    10.000965: watch: (lookup_fast+0xaa/0x150) address=0xffff8880048083a8 value=0x8200080
               rm-113     [005] ..Zff    10.000971: watch: (path_lookupat+0x97/0x1e0) address=0xffff8880048083a8 value=0x8200080
               rm-113     [005] ..Zff    10.000984: watch: (lookup_fast+0xaa/0x150) address=0xffff8880048083a8 value=0x8200080
               rm-113     [005] ..Zff    10.000988: watch: (path_lookupat+0x97/0x1e0) address=0xffff8880048083a8 value=0x8200080
               rm-113     [005] ..Zff    10.001010: watch: (lookup_one_qstr_excl+0x28/0x140) address=0xffff8880048083a8 value=0x8200080
               rm-113     [005] ..Zff    10.001014: watch: (lookup_one_qstr_excl+0xd1/0x140) address=0xffff8880048083a8 value=0x8200080
               rm-113     [005] ..Zff    10.001018: watch: (may_delete_dentry+0x1c/0x200) address=0xffff8880048083a8 value=0x8200080
               rm-113     [005] ..Zff    10.001021: watch: (may_delete_dentry+0x195/0x200) address=0xffff8880048083a8 value=0x8200080
               rm-113     [005] ..Zff    10.001031: watch: (vfs_unlink+0x5e/0x260) address=0xffff8880048083a8 value=0x8200080
               rm-113     [005] d.Z..    10.001067: watch: (d_make_discardable+0x1b/0x40) address=0xffff8880048083a8 value=0x8200080
               rm-113     [005] d.Z..    10.001071: watch: (d_make_discardable+0x29/0x40) address=0xffff8880048083a8 value=0x200080
               rm-113     [005] ...1.    10.001072: dentry_kill: (dentry_kill+0x0/0x2c0) dentry=0xffff8880048083a8
               rm-113     [005] ...1.    10.001218: dentry_kill: (dentry_kill+0x0/0x2c0) dentry=0xffff8880048083a8
               sh-107     [004] ...1.    10.001416: dentry_kill: (dentry_kill+0x0/0x2c0) dentry=0xffff8880049db110
               sh-107     [004] ...1.    10.001444: dentry_kill: (dentry_kill+0x0/0x2c0) dentry=0xffff8880049db248
               sh-107     [004] ...1.    10.001500: dentry_kill: (dentry_kill+0x0/0x2c0) dentry=0xffff888004ad6618
               sh-107     [004] ...1.    10.002067: dentry_kill: (dentry_kill+0x0/0x2c0) dentry=0xffff888004b41e78
               sh-107     [004] ...1.    10.904920: dentry_kill: (dentry_kill+0x0/0x2c0) dentry=0xffff888004b41e78
               sh-107     [004] ...1.    10.905129: dentry_kill: (dentry_kill+0x0/0x2c0) dentry=0xffff888004ad6618


Thank you,

---
base-commit: 0c4256196b3a105307e2235fbfd85e768bbcdd0f

Jinchao Wang (2):
      x86/hw_breakpoints: Make DR7 updates NMI safe
      x86/hw_breakpoints: Add arch_modify_local_hw_breakpoint_addr() API

Masami Hiramatsu (Google) (10):
      x86/mce: Fix hardware debug register corruption on task migration
      HWBP: Add modify_local_hw_breakpoint_addr() API
      tracing/wprobe: Add wprobe (watchpoint probe) trace event support
      x86: hw_breakpoint: Add a kconfig to clarify when a breakpoint fires
      selftests: tracing: Add a basic testcase for wprobe
      selftests: tracing: Add syntax testcase for wprobe
      tracing/wprobe: Add set_wprobe and clear_wprobe event triggers
      selftests: tracing: Add wprobe trigger testcase
      tracing/wprobe: Support BTF typecast in fetchargs
      tracing/wprobe: Support BTF struct offset resolution in set_wprobe trigger


 Documentation/trace/index.rst                      |    1 
 Documentation/trace/wprobetrace.rst                |  200 +++
 arch/Kconfig                                       |   18 
 arch/x86/Kconfig                                   |    2 
 arch/x86/include/asm/debugreg.h                    |   67 +
 arch/x86/include/asm/hw_breakpoint.h               |    2 
 arch/x86/kernel/cpu/mce/core.c                     |   29 
 arch/x86/kernel/hw_breakpoint.c                    |  151 +-
 arch/x86/kernel/nmi.c                              |    7 
 arch/x86/kernel/traps.c                            |   10 
 include/linux/hw_breakpoint.h                      |    6 
 include/linux/trace_events.h                       |    3 
 kernel/events/hw_breakpoint.c                      |   48 +
 kernel/trace/Kconfig                               |   24 
 kernel/trace/Makefile                              |    1 
 kernel/trace/trace.c                               |   13 
 kernel/trace/trace.h                               |    6 
 kernel/trace/trace_events_trigger.c                |    2 
 kernel/trace/trace_probe.c                         |   36 
 kernel/trace/trace_probe.h                         |   22 
 kernel/trace/trace_wprobe.c                        | 1522 ++++++++++++++++++++
 tools/testing/selftests/ftrace/config              |    3 
 .../ftrace/test.d/dynevent/add_remove_wprobe.tc    |   63 +
 .../test.d/dynevent/wprobes_syntax_errors.tc       |   23 
 .../test.d/trigger/trigger-wprobe-btf-offset.tc    |   85 +
 .../test.d/trigger/trigger-wprobe-btf-typecast.tc  |   85 +
 .../test.d/trigger/trigger-wprobe-syntax-errors.tc |   37 
 .../ftrace/test.d/trigger/trigger-wprobe.tc        |  107 +
 28 files changed, 2476 insertions(+), 97 deletions(-)
 create mode 100644 Documentation/trace/wprobetrace.rst
 create mode 100644 kernel/trace/trace_wprobe.c
 create mode 100644 tools/testing/selftests/ftrace/test.d/dynevent/add_remove_wprobe.tc
 create mode 100644 tools/testing/selftests/ftrace/test.d/dynevent/wprobes_syntax_errors.tc
 create mode 100644 tools/testing/selftests/ftrace/test.d/trigger/trigger-wprobe-btf-offset.tc
 create mode 100644 tools/testing/selftests/ftrace/test.d/trigger/trigger-wprobe-btf-typecast.tc
 create mode 100644 tools/testing/selftests/ftrace/test.d/trigger/trigger-wprobe-syntax-errors.tc
 create mode 100644 tools/testing/selftests/ftrace/test.d/trigger/trigger-wprobe.tc

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

[PATCH v15 01/12] x86/mce: Fix hardware debug register corruption on task migration

[Masami Hiramatsu (Google)]

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

In exc_machine_check_user(), local_db_save() and local_db_restore() are
invoked in the outer entry stubs (DEFINE_IDTENTRY_MCE_USER,
DEFINE_FREDENTRY_MCE, and DEFINE_IDTENTRY_RAW), surrounding
exc_machine_check_user().

However, exc_machine_check_user() calls irqentry_exit_to_user_mode(),
which handles pending thread work and may schedule() if TIF_NEED_RESCHED
is set. If the task migrates to another CPU during schedule(),
local_db_restore() runs on the new CPU with the dr7 state saved from the
old CPU. This corrupts the new CPU's DR7 hardware debug register and
leaves the old CPU's DR7 disabled.
In short, local_db_save() and local_db_restore() pair must be run
on the same CPU.

To fix this, move local_db_save() and local_db_restore() inside
exc_machine_check_user() and exc_machine_check_kernel(). In
exc_machine_check_user(), DR7 is saved and restored strictly around
do_machine_check() to avoid schedule() during migration. In
exc_machine_check_kernel(), local_db_save() is called at the entry point
to prevent early memory accesses from triggering nested #DB exceptions,
and restored on all exits.

Fixes: cd840e424f27 ("x86/entry, mce: Disallow #DB during #MC")
Assisted-by: Antigravity:gemini-3.8-flash
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
---
Changes in v15:
 - Move local_db_save() to the entry of exc_machine_check_kernel() and
   restore it on early return from mce_check_crashing_cpu() to prevent
   nested #DB on watched variables.
Changes in v14:
 - Newly added.
---
 arch/x86/kernel/cpu/mce/core.c |   27 ++++++++++-----------------
 1 file changed, 10 insertions(+), 17 deletions(-)

diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
index ab469605fc89..39f238952e14 100644
--- a/arch/x86/kernel/cpu/mce/core.c
+++ b/arch/x86/kernel/cpu/mce/core.c
@@ -2108,6 +2108,9 @@ bool filter_mce(struct mce *m)
 static __always_inline void exc_machine_check_kernel(struct pt_regs *regs)
 {
 	irqentry_state_t irq_state;
+	unsigned long dr7;
+
+	dr7 = local_db_save();
 
 	WARN_ON_ONCE(user_mode(regs));
 
@@ -2116,20 +2119,26 @@ static __always_inline void exc_machine_check_kernel(struct pt_regs *regs)
 	 * mce_check_crashing_cpu() for details.
 	 */
 	if (mca_cfg.initialized && mce_check_crashing_cpu())
-		return;
+		goto out;
 
 	irq_state = irqentry_nmi_enter(regs);
 
 	do_machine_check(regs);
 
 	irqentry_nmi_exit(regs, irq_state);
+out:
+	local_db_restore(dr7);
 }
 
 static __always_inline void exc_machine_check_user(struct pt_regs *regs)
 {
+	unsigned long dr7;
+
 	irqentry_enter_from_user_mode(regs);
 
+	dr7 = local_db_save();
 	do_machine_check(regs);
+	local_db_restore(dr7);
 
 	irqentry_exit_to_user_mode(regs);
 }
@@ -2138,21 +2147,13 @@ static __always_inline void exc_machine_check_user(struct pt_regs *regs)
 /* MCE hit kernel mode */
 DEFINE_IDTENTRY_MCE(exc_machine_check)
 {
-	unsigned long dr7;
-
-	dr7 = local_db_save();
 	exc_machine_check_kernel(regs);
-	local_db_restore(dr7);
 }
 
 /* The user mode variant. */
 DEFINE_IDTENTRY_MCE_USER(exc_machine_check)
 {
-	unsigned long dr7;
-
-	dr7 = local_db_save();
 	exc_machine_check_user(regs);
-	local_db_restore(dr7);
 }
 
 #ifdef CONFIG_X86_FRED
@@ -2169,28 +2170,20 @@ DEFINE_IDTENTRY_MCE_USER(exc_machine_check)
  */
 DEFINE_FREDENTRY_MCE(exc_machine_check)
 {
-	unsigned long dr7;
-
-	dr7 = local_db_save();
 	if (user_mode(regs))
 		exc_machine_check_user(regs);
 	else
 		exc_machine_check_kernel(regs);
-	local_db_restore(dr7);
 }
 #endif
 #else
 /* 32bit unified entry point */
 DEFINE_IDTENTRY_RAW(exc_machine_check)
 {
-	unsigned long dr7;
-
-	dr7 = local_db_save();
 	if (user_mode(regs))
 		exc_machine_check_user(regs);
 	else
 		exc_machine_check_kernel(regs);
-	local_db_restore(dr7);
 }
 #endif
 

[PATCH v15 02/12] x86/hw_breakpoints: Make DR7 updates NMI safe

[Masami Hiramatsu (Google)]

From: Jinchao Wang <wangjinchao600@gmail.com>

Hardware breakpoint installation and removal run with IRQs disabled, but
an NMI can still enter the same code through KGDB. The interrupted
operation and the NMI can consequently claim the same slot or overwrite
each other's DR7 state.

Claim and release per-CPU slots with cmpxchg. Update cpu_dr7 with
single-instruction per-CPU operations, and preserve hardware-first
disable and hardware-last enable ordering. Add a per-CPU sequence number
so interrupted DR7 writers and restore paths detect an NMI update and
retry from the latest shadow state.

Link: https://lore.kernel.org/all/4ee0a2efc9e8387af83286b8495b7d490247e165.1785067572.git.wangjinchao600@gmail.com/

Assisted-by: Antigravity:gemini-3.8-flash
Signed-off-by: Jinchao Wang <wangjinchao600@gmail.com>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
---
Changes in v15:
 - Always preserve DR7_FIXED_1 in arch_install_hw_breakpoint(),
   arch_uninstall_hw_breakpoint(), and hw_breakpoint_restore() to comply
   with the x86 architectural specification.
 - Wrap local_db_save() in a cpu_dr7_seq loop to detect NMI breakpoint
   updates and ensure DR7 is disabled before entry.
 - In local_db_restore(), if dr7 is 0 and an NMI modified breakpoints,
   restore DR7_FIXED_1 to undo the NMI's overwrite and preserve KVM
   guest isolation.
 - Always write "val | DR7_FIXED_1" to hardware DR7 in local_db_restore()
   to ensure architectural compliance.
 - Avoid modifying the saved dr7 argument in-place across retry loops.
Changes in v14:
 - In local_db_restore(), return immediately if saved dr7 is 0 to avoid
   overwriting intentionally cleared hardware DR7 state (e.g. KVM guest
   entry) with cpu_dr7 when an NMI increments cpu_dr7_seq.
Changes in v13:
 - Add compiler barriers (barrier()) before checking cpu_dr7_seq to
   prevent the compiler from hoisting the sequence check before debug
   register updates or shadow state modifications.
Changes in v12:
 - Use stack variables dr7 and dr7_seq directly in exc_nmi() and remove
   unnecessary per-CPU nmi_dr7 and nmi_dr7_seq variables.
---
 arch/x86/include/asm/debugreg.h |   67 ++++++++++++++++++--------
 arch/x86/kernel/cpu/mce/core.c  |   10 ++--
 arch/x86/kernel/hw_breakpoint.c |  101 ++++++++++++++++++++-------------------
 arch/x86/kernel/nmi.c           |    7 ++-
 arch/x86/kernel/traps.c         |   10 +++-
 5 files changed, 115 insertions(+), 80 deletions(-)

diff --git a/arch/x86/include/asm/debugreg.h b/arch/x86/include/asm/debugreg.h
index 854d82b88ff4..3399e166d304 100644
--- a/arch/x86/include/asm/debugreg.h
+++ b/arch/x86/include/asm/debugreg.h
@@ -18,6 +18,7 @@
 #define DR7_FIXED_1	0x00000400
 
 DECLARE_PER_CPU(unsigned long, cpu_dr7);
+DECLARE_PER_CPU(unsigned int, cpu_dr7_seq);
 
 #ifndef CONFIG_PARAVIRT_XXL
 /*
@@ -125,40 +126,66 @@ static __always_inline bool hw_breakpoint_active(void)
 
 extern void hw_breakpoint_restore(void);
 
-static __always_inline unsigned long local_db_save(void)
+static __always_inline void local_db_save(unsigned long *dr7,
+					  unsigned int *dr7_seq)
 {
-	unsigned long dr7;
+	do {
+		*dr7_seq = this_cpu_read(cpu_dr7_seq);
+		*dr7 = 0;
 
-	if (cpu_feature_enabled(X86_FEATURE_HYPERVISOR) && !hw_breakpoint_active())
-		return 0;
-
-	get_debugreg(dr7, 7);
+		if (cpu_feature_enabled(X86_FEATURE_HYPERVISOR) &&
+		    !hw_breakpoint_active())
+			return;
 
-	/* Architecturally set bit */
-	dr7 &= ~DR7_FIXED_1;
-	if (dr7)
-		set_debugreg(DR7_FIXED_1, 7);
+		get_debugreg(*dr7, 7);
 
-	/*
-	 * Ensure the compiler doesn't lower the above statements into
-	 * the critical section; disabling breakpoints late would not
-	 * be good.
-	 */
-	barrier();
+		/* Architecturally set bit */
+		*dr7 &= ~DR7_FIXED_1;
+		if (*dr7)
+			set_debugreg(DR7_FIXED_1, 7);
 
-	return dr7;
+		/*
+		 * Ensure the compiler doesn't lower the above statements into
+		 * the critical section; disabling breakpoints late would not
+		 * be good.
+		 */
+		barrier();
+	} while (unlikely(*dr7_seq != this_cpu_read(cpu_dr7_seq)));
 }
 
-static __always_inline void local_db_restore(unsigned long dr7)
+static __always_inline void local_db_restore(unsigned long dr7,
+					     unsigned int dr7_seq)
 {
+	unsigned long val;
+	unsigned int seq;
+
 	/*
 	 * Ensure the compiler doesn't raise this statement into
 	 * the critical section; enabling breakpoints early would
 	 * not be good.
 	 */
 	barrier();
-	if (dr7)
-		set_debugreg(dr7, 7);
+
+	do {
+		seq = this_cpu_read(cpu_dr7_seq);
+		if (seq == dr7_seq) {
+			if (!dr7)
+				return;
+			val = dr7;
+		} else {
+			/*
+			 * If an NMI modified breakpoints while DR7 was saved as 0
+			 * (e.g. KVM guest entry), arch_install_hw_breakpoint()
+			 * clobbered hardware DR7. Restore val = 0 (DR7_FIXED_1)
+			 * to clean up the NMI's write and preserve guest isolation.
+			 * Otherwise, load the latest cpu_dr7 state.
+			 */
+			val = dr7 ? this_cpu_read(cpu_dr7) : 0;
+		}
+
+		set_debugreg(val | DR7_FIXED_1, 7);
+		barrier();
+	} while (unlikely(seq != this_cpu_read(cpu_dr7_seq)));
 }
 
 #ifdef CONFIG_CPU_SUP_AMD
diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
index 39f238952e14..b3669d6f88d4 100644
--- a/arch/x86/kernel/cpu/mce/core.c
+++ b/arch/x86/kernel/cpu/mce/core.c
@@ -2109,8 +2109,9 @@ static __always_inline void exc_machine_check_kernel(struct pt_regs *regs)
 {
 	irqentry_state_t irq_state;
 	unsigned long dr7;
+	unsigned int dr7_seq;
 
-	dr7 = local_db_save();
+	local_db_save(&dr7, &dr7_seq);
 
 	WARN_ON_ONCE(user_mode(regs));
 
@@ -2127,18 +2128,19 @@ static __always_inline void exc_machine_check_kernel(struct pt_regs *regs)
 
 	irqentry_nmi_exit(regs, irq_state);
 out:
-	local_db_restore(dr7);
+	local_db_restore(dr7, dr7_seq);
 }
 
 static __always_inline void exc_machine_check_user(struct pt_regs *regs)
 {
 	unsigned long dr7;
+	unsigned int dr7_seq;
 
 	irqentry_enter_from_user_mode(regs);
 
-	dr7 = local_db_save();
+	local_db_save(&dr7, &dr7_seq);
 	do_machine_check(regs);
-	local_db_restore(dr7);
+	local_db_restore(dr7, dr7_seq);
 
 	irqentry_exit_to_user_mode(regs);
 }
diff --git a/arch/x86/kernel/hw_breakpoint.c b/arch/x86/kernel/hw_breakpoint.c
index f846c15f21ca..312550be3ad2 100644
--- a/arch/x86/kernel/hw_breakpoint.c
+++ b/arch/x86/kernel/hw_breakpoint.c
@@ -40,6 +40,9 @@
 DEFINE_PER_CPU(unsigned long, cpu_dr7);
 EXPORT_PER_CPU_SYMBOL(cpu_dr7);
 
+/* Sequence number of the per-CPU DR7 state. */
+DEFINE_PER_CPU(unsigned int, cpu_dr7_seq);
+
 /* Per cpu debug address registers values */
 static DEFINE_PER_CPU(unsigned long, cpu_debugreg[HBP_NUM]);
 
@@ -97,38 +100,31 @@ int decode_dr7(unsigned long dr7, int bpnum, unsigned *len, unsigned *type)
 int arch_install_hw_breakpoint(struct perf_event *bp)
 {
 	struct arch_hw_breakpoint *info = counter_arch_bp(bp);
-	unsigned long *dr7;
+	unsigned int seq;
 	int i;
 
 	lockdep_assert_irqs_disabled();
 
 	for (i = 0; i < HBP_NUM; i++) {
-		struct perf_event **slot = this_cpu_ptr(&bp_per_reg[i]);
-
-		if (!*slot) {
-			*slot = bp;
+		if (!this_cpu_cmpxchg(bp_per_reg[i], NULL, bp))
 			break;
-		}
 	}
 
 	if (WARN_ONCE(i == HBP_NUM, "Can't find any breakpoint slot"))
 		return -EBUSY;
 
-	set_debugreg(info->address, i);
-	__this_cpu_write(cpu_debugreg[i], info->address);
-
-	dr7 = this_cpu_ptr(&cpu_dr7);
-	*dr7 |= encode_dr7(i, info->len, info->type);
-
-	/*
-	 * Ensure we first write cpu_dr7 before we set the DR7 register.
-	 * This ensures an NMI never see cpu_dr7 0 when DR7 is not.
-	 */
-	barrier();
-
-	set_debugreg(*dr7, 7);
-	if (info->mask)
-		amd_set_dr_addr_mask(info->mask, i);
+	do {
+		seq = this_cpu_inc_return(cpu_dr7_seq);
+		this_cpu_write(cpu_debugreg[i], info->address);
+		barrier();
+		set_debugreg(info->address, i);
+		if (info->mask)
+			amd_set_dr_addr_mask(info->mask, i);
+		this_cpu_or(cpu_dr7, encode_dr7(i, info->len, info->type));
+		barrier();
+		set_debugreg(this_cpu_read(cpu_dr7) | DR7_FIXED_1, 7);
+		barrier();
+	} while (seq != this_cpu_read(cpu_dr7_seq));
 
 	return 0;
 }
@@ -146,36 +142,34 @@ void arch_uninstall_hw_breakpoint(struct perf_event *bp)
 {
 	struct arch_hw_breakpoint *info = counter_arch_bp(bp);
 	unsigned long dr7;
+	unsigned int seq;
 	int i;
 
 	lockdep_assert_irqs_disabled();
 
 	for (i = 0; i < HBP_NUM; i++) {
-		struct perf_event **slot = this_cpu_ptr(&bp_per_reg[i]);
-
-		if (*slot == bp) {
-			*slot = NULL;
+		if (this_cpu_read(bp_per_reg[i]) == bp)
 			break;
-		}
 	}
 
 	if (WARN_ONCE(i == HBP_NUM, "Can't find any breakpoint slot"))
 		return;
 
-	dr7 = this_cpu_read(cpu_dr7);
-	dr7 &= ~__encode_dr7(i, info->len, info->type);
-
-	set_debugreg(dr7, 7);
-	if (info->mask)
-		amd_set_dr_addr_mask(0, i);
-
-	/*
-	 * Ensure the write to cpu_dr7 is after we've set the DR7 register.
-	 * This ensures an NMI never see cpu_dr7 0 when DR7 is not.
-	 */
-	barrier();
-
-	this_cpu_write(cpu_dr7, dr7);
+	do {
+		seq = this_cpu_inc_return(cpu_dr7_seq);
+		dr7 = this_cpu_read(cpu_dr7);
+		dr7 &= ~__encode_dr7(i, info->len, info->type);
+		set_debugreg(dr7 | DR7_FIXED_1, 7);
+		if (info->mask)
+			amd_set_dr_addr_mask(0, i);
+		barrier();
+		this_cpu_and(cpu_dr7,
+			     ~__encode_dr7(i, info->len, info->type));
+		barrier();
+	} while (seq != this_cpu_read(cpu_dr7_seq));
+
+	WARN_ONCE(this_cpu_cmpxchg(bp_per_reg[i], bp, NULL) != bp,
+		  "Can't release breakpoint slot");
 }
 
 static int arch_bp_generic_len(int x86_len)
@@ -309,13 +303,14 @@ static inline bool within_cpu_entry(unsigned long addr, unsigned long end)
 				sizeof(struct tlb_state)))
 			return true;
 
-		/*
-		 * When in guest (X86_FEATURE_HYPERVISOR), local_db_save()
-		 * will read per-cpu cpu_dr7 before clear dr7 register.
-		 */
+		/* local_db_save() reads this state before clearing DR7. */
 		if (within_area(addr, end, (unsigned long)&per_cpu(cpu_dr7, cpu),
 				sizeof(cpu_dr7)))
 			return true;
+		if (within_area(addr, end,
+				(unsigned long)&per_cpu(cpu_dr7_seq, cpu),
+				sizeof(cpu_dr7_seq)))
+			return true;
 	}
 
 	return false;
@@ -483,12 +478,18 @@ void flush_ptrace_hw_breakpoint(struct task_struct *tsk)
 
 void hw_breakpoint_restore(void)
 {
-	set_debugreg(__this_cpu_read(cpu_debugreg[0]), 0);
-	set_debugreg(__this_cpu_read(cpu_debugreg[1]), 1);
-	set_debugreg(__this_cpu_read(cpu_debugreg[2]), 2);
-	set_debugreg(__this_cpu_read(cpu_debugreg[3]), 3);
-	set_debugreg(DR6_RESERVED, 6);
-	set_debugreg(__this_cpu_read(cpu_dr7), 7);
+	unsigned int seq;
+
+	do {
+		seq = this_cpu_inc_return(cpu_dr7_seq);
+		set_debugreg(this_cpu_read(cpu_debugreg[0]), 0);
+		set_debugreg(this_cpu_read(cpu_debugreg[1]), 1);
+		set_debugreg(this_cpu_read(cpu_debugreg[2]), 2);
+		set_debugreg(this_cpu_read(cpu_debugreg[3]), 3);
+		set_debugreg(DR6_RESERVED, 6);
+		set_debugreg(this_cpu_read(cpu_dr7) | DR7_FIXED_1, 7);
+		barrier();
+	} while (seq != this_cpu_read(cpu_dr7_seq));
 }
 EXPORT_SYMBOL_FOR_KVM(hw_breakpoint_restore);
 
diff --git a/arch/x86/kernel/nmi.c b/arch/x86/kernel/nmi.c
index 3c9f60d6ca5a..c3806f7bd3e8 100644
--- a/arch/x86/kernel/nmi.c
+++ b/arch/x86/kernel/nmi.c
@@ -531,11 +531,12 @@ enum nmi_states {
 };
 static DEFINE_PER_CPU(enum nmi_states, nmi_state);
 static DEFINE_PER_CPU(unsigned long, nmi_cr2);
-static DEFINE_PER_CPU(unsigned long, nmi_dr7);
 
 DEFINE_IDTENTRY_RAW(exc_nmi)
 {
 	irqentry_state_t irq_state;
+	unsigned long dr7;
+	unsigned int dr7_seq;
 	struct nmi_stats *nsp = this_cpu_ptr(&nmi_stats);
 
 	/*
@@ -572,7 +573,7 @@ DEFINE_IDTENTRY_RAW(exc_nmi)
 	 */
 	sev_es_ist_enter(regs);
 
-	this_cpu_write(nmi_dr7, local_db_save());
+	local_db_save(&dr7, &dr7_seq);
 
 	irq_state = irqentry_nmi_enter(regs);
 
@@ -594,7 +595,7 @@ DEFINE_IDTENTRY_RAW(exc_nmi)
 
 	irqentry_nmi_exit(regs, irq_state);
 
-	local_db_restore(this_cpu_read(nmi_dr7));
+	local_db_restore(dr7, dr7_seq);
 
 	sev_es_ist_exit();
 
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 30aa8369957e..018abe736285 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -1231,8 +1231,12 @@ static noinstr void exc_debug_kernel(struct pt_regs *regs, unsigned long dr6)
 	 * it results in an endless recursion and stack overflow. Thus we stay
 	 * with the IDT approach, i.e., save DR7 and disable #DB.
 	 */
-	unsigned long dr7 = local_db_save();
-	irqentry_state_t irq_state = irqentry_nmi_enter(regs);
+	unsigned long dr7;
+	unsigned int dr7_seq;
+	irqentry_state_t irq_state;
+
+	local_db_save(&dr7, &dr7_seq);
+	irq_state = irqentry_nmi_enter(regs);
 	instrumentation_begin();
 
 	/*
@@ -1289,7 +1293,7 @@ static noinstr void exc_debug_kernel(struct pt_regs *regs, unsigned long dr6)
 	instrumentation_end();
 	irqentry_nmi_exit(regs, irq_state);
 
-	local_db_restore(dr7);
+	local_db_restore(dr7, dr7_seq);
 }
 
 static noinstr void exc_debug_user(struct pt_regs *regs, unsigned long dr6)

[PATCH v15 03/12] x86/hw_breakpoints: Add arch_modify_local_hw_breakpoint_addr() API

[Masami Hiramatsu (Google)]

From: Jinchao Wang <wangjinchao600@gmail.com>

Wprobe needs to move an active per-CPU watchpoint without releasing and
reserving its hardware slot.

Add arch_modify_local_hw_breakpoint_addr() as the architecture backend for
modify_local_hw_breakpoint_addr(). It validates the new address, finds the
installed local slot, and updates the hardware debug register and per-CPU
shadow register. The core layer (modify_local_hw_breakpoint_addr()) handles
updating bp->attr.bp_addr and counter_arch_bp(bp)->address.

The caller must provide an installed local event and a valid address.
Slot ownership, breakpoint type, length, mask and DR7 remain unchanged.

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

Assisted-by: Antigravity:gemini-3.8-flash
Signed-off-by: Jinchao Wang <wangjinchao600@gmail.com>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
---
Changes in v15:
 - Temporarily clear the breakpoint enable bit in DR7 before updating the
   debug address register, and re-enable it afterward, to comply with the
   x86 hardware specification and avoid spurious #DB exceptions.
Changes in v13:
 - Add compiler barrier (barrier()) before checking cpu_dr7_seq to
   prevent hoisting the sequence check before set_debugreg().
 - Clarify in commit log and code comment that the core layer manages
   updating bp->attr.bp_addr and counter_arch_bp(bp)->address.
Changes in v11:
 - Return int error code instead of void.
 - Validate the new address using hw_breakpoint_arch_parse() before
   updating registers.
 - Increment cpu_dr7_seq in a sequence loop for NMI protection.
 - Return -ENOENT if the breakpoint slot is not found on the local CPU.
---
 arch/x86/include/asm/hw_breakpoint.h |    2 +
 arch/x86/kernel/hw_breakpoint.c      |   56 ++++++++++++++++++++++++++++++++++
 2 files changed, 58 insertions(+)

diff --git a/arch/x86/include/asm/hw_breakpoint.h b/arch/x86/include/asm/hw_breakpoint.h
index 0bc931cd0698..f35ec491f6dd 100644
--- a/arch/x86/include/asm/hw_breakpoint.h
+++ b/arch/x86/include/asm/hw_breakpoint.h
@@ -59,6 +59,8 @@ extern int hw_breakpoint_exceptions_notify(struct notifier_block *unused,
 
 
 int arch_install_hw_breakpoint(struct perf_event *bp);
+int arch_modify_local_hw_breakpoint_addr(struct perf_event *bp,
+					 unsigned long addr);
 void arch_uninstall_hw_breakpoint(struct perf_event *bp);
 void hw_breakpoint_pmu_read(struct perf_event *bp);
 void hw_breakpoint_pmu_unthrottle(struct perf_event *bp);
diff --git a/arch/x86/kernel/hw_breakpoint.c b/arch/x86/kernel/hw_breakpoint.c
index 312550be3ad2..99f0926298a8 100644
--- a/arch/x86/kernel/hw_breakpoint.c
+++ b/arch/x86/kernel/hw_breakpoint.c
@@ -129,6 +129,62 @@ int arch_install_hw_breakpoint(struct perf_event *bp)
 	return 0;
 }
 
+/*
+ * Modify the address of an installed perf counter breakpoint on local CPU.
+ *
+ * This updates the debug address register and per-CPU shadow state without
+ * changing slot allocation or DR7. The core layer (modify_local_hw_breakpoint_addr())
+ * manages updating bp->attr.bp_addr and counter_arch_bp(bp)->address.
+ *
+ * Atomic: called with IRQs disabled and handles variables and registers
+ * local to this CPU.
+ */
+int arch_modify_local_hw_breakpoint_addr(struct perf_event *bp,
+					 unsigned long addr)
+{
+	struct arch_hw_breakpoint *info = counter_arch_bp(bp);
+	struct arch_hw_breakpoint hw;
+	struct perf_event_attr attr = bp->attr;
+	unsigned long dr7;
+	unsigned int seq;
+	int i, ret;
+
+	lockdep_assert_irqs_disabled();
+
+	attr.bp_addr = addr;
+	ret = hw_breakpoint_arch_parse(bp, &attr, &hw);
+	if (ret)
+		return ret;
+
+	for (i = 0; i < HBP_NUM; i++) {
+		if (this_cpu_read(bp_per_reg[i]) == bp)
+			break;
+	}
+
+	if (WARN_ONCE(i == HBP_NUM, "Can't find any breakpoint slot"))
+		return -ENOENT;
+
+	do {
+		seq = this_cpu_inc_return(cpu_dr7_seq);
+
+		/* Disable breakpoint in DR7 before updating address register */
+		dr7 = this_cpu_read(cpu_dr7);
+		set_debugreg((dr7 & ~__encode_dr7(i, info->len, info->type)) | DR7_FIXED_1, 7);
+		barrier();
+
+		this_cpu_write(cpu_debugreg[i], addr);
+		barrier();
+		set_debugreg(addr, i);
+		barrier();
+
+		/* Re-enable breakpoint in DR7 */
+		set_debugreg(this_cpu_read(cpu_dr7) | DR7_FIXED_1, 7);
+		barrier();
+	} while (seq != this_cpu_read(cpu_dr7_seq));
+
+	return 0;
+}
+
 /*
  * Uninstall the breakpoint contained in the given counter.
  *

[PATCH v15 04/12] HWBP: Add modify_local_hw_breakpoint_addr() API

[Masami Hiramatsu (Google)]

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

Add modify_local_hw_breakpoint_addr() to update only the watched
address of an installed hardware breakpoint on the local CPU without
releasing and reserving its hardware slot. This is available when the
architecture selects CONFIG_HAVE_MODIFY_LOCAL_HW_BREAKPOINT_ADDR.

The caller must provide an installed local event and a valid address,
and update other CPUs separately.

Link: https://lore.kernel.org/all/f9c49dfa49bdc57ba8c0574bc9981c1e581acf92.1785067572.git.wangjinchao600@gmail.com/

Assisted-by: Antigravity:gemini-3.8-flash
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Jinchao Wang <wangjinchao600@gmail.com>
---
Changes in v15:
 - Use WRITE_ONCE() for counter_arch_bp(bp)->address and bp->attr.bp_addr
   in both update and rollback paths to prevent data races with concurrent
   readers (e.g. NMI handlers).
Changes in v13:
 - Add comment to modify_local_hw_breakpoint_addr() clarifying the early
   update behavior of bp->attr.bp_addr during the NMI race window.
Changes in v12:
 - Update bp->attr.bp_addr and counter_arch_bp(bp)->address before
   calling arch_modify_local_hw_breakpoint_addr() to prevent race
   conditions during interrupt handling.
 - Restore counter_arch_bp(bp)->address and bp->attr.bp_addr if
   arch_modify_local_hw_breakpoint_addr() fails.
Changes in v11:
 - Check return value of arch_modify_local_hw_breakpoint_addr() and
   return error on failure.
 - Update bp->attr.bp_addr and counter_arch_bp(bp)->address only after
   arch modification succeeds.
---
 arch/Kconfig                  |    8 +++++++
 arch/x86/Kconfig              |    1 +
 include/linux/hw_breakpoint.h |    6 +++++
 kernel/events/hw_breakpoint.c |   48 +++++++++++++++++++++++++++++++++++++++++
 4 files changed, 63 insertions(+)

diff --git a/arch/Kconfig b/arch/Kconfig
index 45c657772362..d021bc31ef14 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -474,6 +474,14 @@ config HAVE_MIXED_BREAKPOINTS_REGS
 	  Select this option if your arch implements breakpoints under the
 	  latter fashion.
 
+config HAVE_MODIFY_LOCAL_HW_BREAKPOINT_ADDR
+	bool
+	depends on HAVE_HW_BREAKPOINT
+	help
+	  Select this if the architecture can modify the address of an
+	  installed hardware breakpoint on the local CPU without releasing
+	  and reserving its hardware slot.
+
 config HAVE_USER_RETURN_NOTIFIER
 	bool
 
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 15fd9ec5ecac..38e29e465022 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -249,6 +249,7 @@ config X86
 	select HAVE_FUNCTION_TRACER
 	select HAVE_GCC_PLUGINS
 	select HAVE_HW_BREAKPOINT
+	select HAVE_MODIFY_LOCAL_HW_BREAKPOINT_ADDR
 	select HAVE_IOREMAP_PROT
 	select HAVE_IRQ_EXIT_ON_IRQ_STACK	if X86_64
 	select HAVE_IRQ_TIME_ACCOUNTING
diff --git a/include/linux/hw_breakpoint.h b/include/linux/hw_breakpoint.h
index db199d653dd1..bf65c7fffd99 100644
--- a/include/linux/hw_breakpoint.h
+++ b/include/linux/hw_breakpoint.h
@@ -81,6 +81,9 @@ register_wide_hw_breakpoint(struct perf_event_attr *attr,
 			    perf_overflow_handler_t triggered,
 			    void *context);
 
+int modify_local_hw_breakpoint_addr(struct perf_event *bp,
+				    unsigned long addr);
+
 extern int register_perf_hw_breakpoint(struct perf_event *bp);
 extern void unregister_hw_breakpoint(struct perf_event *bp);
 extern void unregister_wide_hw_breakpoint(struct perf_event * __percpu *cpu_events);
@@ -124,6 +127,9 @@ register_wide_hw_breakpoint(struct perf_event_attr *attr,
 			    perf_overflow_handler_t triggered,
 			    void *context)		{ return NULL; }
 static inline int
+modify_local_hw_breakpoint_addr(struct perf_event *bp,
+				unsigned long addr) { return -EOPNOTSUPP; }
+static inline int
 register_perf_hw_breakpoint(struct perf_event *bp)	{ return -ENOSYS; }
 static inline void unregister_hw_breakpoint(struct perf_event *bp)	{ }
 static inline void
diff --git a/kernel/events/hw_breakpoint.c b/kernel/events/hw_breakpoint.c
index 789add0c185a..69bfb17b87c4 100644
--- a/kernel/events/hw_breakpoint.c
+++ b/kernel/events/hw_breakpoint.c
@@ -888,6 +888,54 @@ void unregister_wide_hw_breakpoint(struct perf_event * __percpu *cpu_events)
 }
 EXPORT_SYMBOL_GPL(unregister_wide_hw_breakpoint);
 
+/**
+ * modify_local_hw_breakpoint_addr - update a local breakpoint address
+ * @bp: the hwbp perf event for this CPU
+ * @addr: the new address for @bp
+ *
+ * Update only the address of an installed breakpoint on the local CPU without
+ * releasing and reserving its hardware slot. The caller must update other CPUs.
+ * Return 0, or -EOPNOTSUPP if the architecture does not support this operation.
+ *
+ * Note: bp->attr.bp_addr and counter_arch_bp(bp)->address are updated before
+ * modifying hardware registers so that interrupt/NMI handlers and CPU entry
+ * paths observe the new address during the transition. If an NMI hits the old
+ * breakpoint address before the hardware register update finishes, the event
+ * handler will see bp->attr.bp_addr already pointing to @addr. If the
+ * architecture update fails, both are rolled back to the previous address.
+ * Callers must be prepared for this behavior.
+ */
+#ifdef CONFIG_HAVE_MODIFY_LOCAL_HW_BREAKPOINT_ADDR
+int modify_local_hw_breakpoint_addr(struct perf_event *bp,
+				    unsigned long addr)
+{
+	unsigned long old_addr;
+	int ret;
+
+	lockdep_assert_irqs_disabled();
+
+	old_addr = bp->attr.bp_addr;
+	WRITE_ONCE(counter_arch_bp(bp)->address, addr);
+	WRITE_ONCE(bp->attr.bp_addr, addr);
+
+	ret = arch_modify_local_hw_breakpoint_addr(bp, addr);
+	if (ret) {
+		WRITE_ONCE(counter_arch_bp(bp)->address, old_addr);
+		WRITE_ONCE(bp->attr.bp_addr, old_addr);
+		return ret;
+	}
+
+	return 0;
+}
+#else
+int modify_local_hw_breakpoint_addr(struct perf_event *bp,
+				    unsigned long addr)
+{
+	return -EOPNOTSUPP;
+}
+#endif
+EXPORT_SYMBOL_GPL(modify_local_hw_breakpoint_addr);
+
 /**
  * hw_breakpoint_is_used - check if breakpoints are currently used
  *

[PATCH v15 05/12] tracing/wprobe: Add wprobe (watchpoint probe) trace event support

[Masami Hiramatsu (Google)]

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/

Assisted-by: Antigravity:gemini-3.8-flash
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
---
Changes in v15:
 - Introduce trace_wprobe_is_valid_addr() to validate target address
   and natural alignment for wprobe length during event creation.
 - Move local variable declarations to function entry in
   trace_wprobe_show() to comply with kernel C coding standards.
 - Fix indentation in kernel/trace/trace.c to use tabs instead of spaces.
Changes in v14:
 - In parse_address_spec(), reject address 0 and user-space addresses
   by changing the check to '_addr < TASK_SIZE'.
 - In trace_wprobe_show(), format symbol and offset explicitly instead
   of using '%pS' to ensure dynamic event restoration works properly.
 - Add offset field to struct trace_wprobe and pass it to
   alloc_trace_wprobe().
Changes in v13:
 - Fix documentation notation to SYMBOL[+|-OFFS] as same as others.
 - Fix documentation indents and add default value.
 - Fix README file to add [<args>].
 - Add a note about module unloading.
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 |   78 ++++
 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         |  775 +++++++++++++++++++++++++++++++++++
 10 files changed, 911 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 f4058e8e92e3..4f3fa60e4ecd 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..31cc68b464e9
--- /dev/null
+++ b/Documentation/trace/wprobetrace.rst
@@ -0,0 +1,78 @@
+.. 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 watch (hexadecimal). MUST be in kernel space.
+   SYMBOL[+|-OFFS] : Symbol name to watch. (Optional positive/negative offset)
+   LENGTH       : Length of the data to watch in bytes. (1, 2, 4, or 8)
+                  Default is 4.
+
+  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()`.
+
+Notes
+-----
+Wprobe event does not disable itself even if the module is unloaded.
+For example, if you add a wprobe event on a module variable, and then
+unload the module, the wprobe event will still be enabled. This is for
+watching the address is used unexpectedly after the module is unloaded.
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 a946e0183fd1..40c3e1543f6e 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>] [<args>]\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 74a7a50d1e78..18588c550a98 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 804442b2f7d2..64e7e363e8e2 100644
--- a/kernel/trace/trace_probe.c
+++ b/kernel/trace/trace_probe.c
@@ -1403,6 +1403,23 @@ 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;
@@ -1462,8 +1479,8 @@ 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 d1fb3520700f..f20cafb87cc6 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 */\
@@ -420,6 +421,7 @@ 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)
@@ -546,6 +548,10 @@ 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"),		\
@@ -628,7 +634,9 @@ 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..9c6100b63e8d
--- /dev/null
+++ b/kernel/trace/trace_wprobe.c
@@ -0,0 +1,775 @@
+// 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			offset;
+	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,
+					       int offset,
+					       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->offset = offset;
+	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 bool trace_wprobe_is_valid_addr(unsigned long addr, int len)
+{
+	if (addr < TASK_SIZE)
+		return false;
+
+	if (addr & (len - 1))
+		return false;
+
+	return true;
+}
+
+static int parse_address_spec(const char *spec, unsigned long *addr, int *type,
+			      int *len, char **symbol, int *offset)
+{
+	char *_spec __free(kfree) = NULL;
+	int _len = HW_BREAKPOINT_LEN_4;
+	int _type = HW_BREAKPOINT_RW;
+	unsigned long _addr = 0;
+	int _offset = 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, "+-");
+
+		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 (!trace_wprobe_is_valid_addr(_addr, _len)) {
+		trace_probe_log_err(at + 1 - _spec, BAD_ACCESS_ADDR);
+		return -EINVAL;
+	}
+
+	*addr = _addr;
+	*offset = _offset;
+	*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, offset, 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, &offset);
+	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, offset, 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);
+	const char *type_str;
+	int i, len;
+
+	seq_printf(m, "w:%s/%s", trace_probe_group_name(&tw->tp),
+		   trace_probe_name(&tw->tp));
+
+	if (tw->type == HW_BREAKPOINT_R)
+		type_str = "r";
+	else if (tw->type == HW_BREAKPOINT_W)
+		type_str = "w";
+	else
+		type_str = "rw";
+
+	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) {
+		if (tw->offset)
+			seq_printf(m, " %s@%s%+d:%d", type_str, tw->symbol,
+				   tw->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);
+

[PATCH v15 06/12] x86: hw_breakpoint: Add a kconfig to clarify when a breakpoint fires

[Masami Hiramatsu (Google)]

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

Add CONFIG_HAVE_POST_BREAKPOINT_HOOK which indicates the hw_breakpoint
on that architecture fires after the target memory has been modified.
This is currently x86 only behavior.

Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Reviewed-by: Jinchao Wang <wangjinchao600@gmail.com>
---
 Changes in v11:
  - Move select to alphabetically sorted place.
---
 arch/Kconfig         |   10 ++++++++++
 arch/x86/Kconfig     |    1 +
 kernel/trace/Kconfig |    1 +
 3 files changed, 12 insertions(+)

diff --git a/arch/Kconfig b/arch/Kconfig
index d021bc31ef14..5292bd05d5d4 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -474,6 +474,16 @@ config HAVE_MIXED_BREAKPOINTS_REGS
 	  Select this option if your arch implements breakpoints under the
 	  latter fashion.
 
+config HAVE_POST_BREAKPOINT_HOOK
+	bool
+	depends on HAVE_HW_BREAKPOINT
+	help
+	  Depending on the arch implementation of hardware breakpoints,
+	  some of them provide breakpoint hook after the target memory
+	  is modified.
+	  Select this option if your arch implements breakpoints overflow
+	  handler hooks after the target memory is modified.
+
 config HAVE_MODIFY_LOCAL_HW_BREAKPOINT_ADDR
 	bool
 	depends on HAVE_HW_BREAKPOINT
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 38e29e465022..e4eaf0b607d3 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -289,6 +289,7 @@ config X86
 	select MMU_GATHER_RCU_TABLE_FREE
 	select MMU_GATHER_MERGE_VMAS
 	select HAVE_POSIX_CPU_TIMERS_TASK_WORK
+	select HAVE_POST_BREAKPOINT_HOOK
 	select HAVE_REGS_AND_STACK_ACCESS_API
 	select HAVE_RELIABLE_STACKTRACE		if UNWINDER_ORC || STACK_VALIDATION
 	select HAVE_FUNCTION_ARG_ACCESS_API
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index b58c2565024f..d9b6fa5c35d9 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -866,6 +866,7 @@ config WPROBE_EVENTS
 	bool "Enable wprobe-based dynamic events"
 	depends on TRACING
 	depends on HAVE_HW_BREAKPOINT
+	depends on HAVE_POST_BREAKPOINT_HOOK
 	select PROBE_EVENTS
 	select DYNAMIC_EVENTS
 	help

[PATCH v15 07/12] selftests: tracing: Add a basic testcase for wprobe

[Masami Hiramatsu (Google)]

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

Add 'add_remove_wprobe.tc' testcase for testing wprobe event that
tests adding and removing operations of the wprobe event.

Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
---
 Changes in v9:
  - Fix command check logic to prevent early exit under 'set -e'
    (errexit) when grep or test fails.
  - Simplify enable/disable status checks by removing cat pipes.
 Changes in v8:
  - Fixed silently test failure path.
---
 tools/testing/selftests/ftrace/config              |    1 
 .../ftrace/test.d/dynevent/add_remove_wprobe.tc    |   63 ++++++++++++++++++++
 2 files changed, 64 insertions(+)
 create mode 100644 tools/testing/selftests/ftrace/test.d/dynevent/add_remove_wprobe.tc

diff --git a/tools/testing/selftests/ftrace/config b/tools/testing/selftests/ftrace/config
index 544de0db5f58..d2f503722020 100644
--- a/tools/testing/selftests/ftrace/config
+++ b/tools/testing/selftests/ftrace/config
@@ -27,3 +27,4 @@ CONFIG_STACK_TRACER=y
 CONFIG_TRACER_SNAPSHOT=y
 CONFIG_UPROBES=y
 CONFIG_UPROBE_EVENTS=y
+CONFIG_WPROBE_EVENTS=y
diff --git a/tools/testing/selftests/ftrace/test.d/dynevent/add_remove_wprobe.tc b/tools/testing/selftests/ftrace/test.d/dynevent/add_remove_wprobe.tc
new file mode 100644
index 000000000000..647c37d5e4c8
--- /dev/null
+++ b/tools/testing/selftests/ftrace/test.d/dynevent/add_remove_wprobe.tc
@@ -0,0 +1,63 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+# description: Generic dynamic event - add/remove wprobe events
+# requires: dynamic_events "w[:[<group>/][<event>]] [r|w|rw]@<addr>[:<len>]":README
+
+echo 0 > events/enable
+echo > dynamic_events
+
+# Use jiffies as a variable that is frequently written to.
+TARGET=jiffies
+
+echo "w:my_wprobe w@$TARGET" >> dynamic_events
+
+if ! grep -q my_wprobe dynamic_events; then
+    echo "Failed to create wprobe event"
+    exit_fail
+fi
+
+if [ ! -d events/wprobes/my_wprobe ]; then
+    echo "Failed to create wprobe event directory"
+    exit_fail
+fi
+
+echo 1 > events/wprobes/my_wprobe/enable
+
+# Check if the event is enabled
+if ! grep -q 1 events/wprobes/my_wprobe/enable; then
+    echo "Failed to enable wprobe event"
+    exit_fail
+fi
+
+# Let some time pass to trigger the breakpoint
+sleep 1
+
+# Check if we got any trace output
+if ! grep -q my_wprobe trace; then
+    echo "wprobe event was not triggered"
+    exit_fail
+fi
+
+echo 0 > events/wprobes/my_wprobe/enable
+
+# Check if the event is disabled
+if ! grep -q 0 events/wprobes/my_wprobe/enable; then
+    echo "Failed to disable wprobe event"
+    exit_fail
+fi
+
+echo "-:my_wprobe" >> dynamic_events
+
+if grep -q my_wprobe dynamic_events; then
+    echo "Failed to remove wprobe event"
+    exit_fail
+fi
+
+if [ -d events/wprobes/my_wprobe ]; then
+    echo "Failed to remove wprobe event directory"
+    exit_fail
+fi
+
+clear_trace
+
+exit 0

[PATCH v15 08/12] selftests: tracing: Add syntax testcase for wprobe

[Masami Hiramatsu (Google)]

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

Add "wprobe_syntax_errors.tc" testcase for testing syntax errors
of the watch probe events.

Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
---
Changes in v14:
 - Update comment for invalid offset syntax check to BAD_PROBE_ADDR.
 - Add testcase for invalid address 0 error check (BAD_ACCESS_ADDR).
Changes in v12:
 - Add NO_ARG_BODY error case.
Changes in v11:
 - Add WPROBE_NO_MAXACT syntax error case.
---
 .../test.d/dynevent/wprobes_syntax_errors.tc       |   23 ++++++++++++++++++++
 1 file changed, 23 insertions(+)
 create mode 100644 tools/testing/selftests/ftrace/test.d/dynevent/wprobes_syntax_errors.tc

diff --git a/tools/testing/selftests/ftrace/test.d/dynevent/wprobes_syntax_errors.tc b/tools/testing/selftests/ftrace/test.d/dynevent/wprobes_syntax_errors.tc
new file mode 100644
index 000000000000..e0df58fe7aa3
--- /dev/null
+++ b/tools/testing/selftests/ftrace/test.d/dynevent/wprobes_syntax_errors.tc
@@ -0,0 +1,23 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+# description: Watch probe event parser error log check
+# requires: dynamic_events "w[:[<group>/][<event>]] [r|w|rw]@<addr>[:<len>]":README
+
+check_error() { # command-with-error-pos-by-^
+    ftrace_errlog_check 'wprobe' "$1" 'dynamic_events'
+}
+
+check_error '^w'			# NO_ARG_BODY
+check_error 'w^10 w@jiffies'		# WPROBE_NO_MAXACT
+check_error 'w ^symbol'			# BAD_ACCESS_FMT
+check_error 'w ^a@symbol'		# BAD_ACCESS_TYPE
+check_error 'w w@^symbol'		# BAD_ACCESS_ADDR
+check_error 'w w@^0:4'			# BAD_ACCESS_ADDR
+check_error 'w w@jiffies^+offset'	# BAD_PROBE_ADDR
+check_error 'w w@jiffies:^100'		# BAD_ACCESS_LEN
+check_error 'w w@jiffies ^$arg1'	# BAD_VAR
+check_error 'w w@jiffies ^$retval'	# BAD_VAR
+check_error 'w w@jiffies ^$stack'	# BAD_VAR
+check_error 'w w@jiffies ^%ax'		# BAD_VAR
+
+exit 0

[PATCH v15 09/12] tracing/wprobe: Add set_wprobe and clear_wprobe event triggers

[Masami Hiramatsu (Google)]

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

Add set_wprobe and clear_wprobe event triggers to dynamically attach
and detach hardware breakpoint address monitoring based on event field
contents.

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

Assisted-by: Antigravity:gemini-3.8-flash
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
---
Changes in v15:
 - Use trace_wprobe_is_valid_addr() in wprobe_trigger() to validate
   address and natural alignment for wprobe length.
 - Record SMP local update failures in tw->missed counter.
 - Expose missed event count as a trailing comment in trigger file.
 - Add set_wprobe and clear_wprobe triggers to readme_msg in trace.c.
 - Fix line length exceeding 100 columns in wprobe_trigger_log_err macro.
 - Initialize irq_work and work structs immediately after allocation
   in alloc_trace_wprobe() and check tw->work.func in free_trace_wprobe()
   to prevent WARN_ON(!work->func) on early allocation failure.
Changes in v14:
 - Allow '-1' as a dummy address in parse_address_spec() to set initial
   address to WPROBE_DEFAULT_CLEAR_ADDRESS for trigger-only wprobes.
 - In trace_wprobe_show(), format WPROBE_DEFAULT_CLEAR_ADDRESS as '-1'.
 - Update documentation and examples to use '-1' instead of '0'.
 - Skip field parsing in clear_wprobe if parameter is a count keyword.
 - Set tw->addr to WPROBE_DEFAULT_CLEAR_ADDRESS before soft-enabling event
   and roll back on failure.
 - Fix memory and refcount leak of trigger_data/wprobe_data on error path.
Changes in v13:
 - Align WPROBE_DEFAULT_CLEAR_ADDRESS to 8 bytes using dedicated u64.
 - Remove manual count decrement to rely on core event_trigger_count().
 - Parse optional FIELD argument in clear_wprobe command.
 - Fix trigger reference count leak and error cleanup in command parsing.
 - Update document to add [:COUNT] to trigger syntax and fix adjust forms.
 - Add notes about the exclusive trigger setting behavior.
 - Remove unused dyn_event_ops_mutex.
Changes in v12:
 - Decrement trigger data->count only when watchpoint state is actually
   changed.
 - Remove dyn_event_ops_mutex to fix lockdep circular dependency deadlock.
 - Add event_trigger_init() call to prevent premature freeing of trigger_data.
---
 Documentation/trace/wprobetrace.rst |  107 ++++++
 include/linux/trace_events.h        |    1 
 kernel/trace/Kconfig                |   10 +
 kernel/trace/trace.c                |    4 
 kernel/trace/trace.h                |    1 
 kernel/trace/trace_events_trigger.c |    2 
 kernel/trace/trace_probe.c          |    2 
 kernel/trace/trace_probe.h          |    9 -
 kernel/trace/trace_wprobe.c         |  609 +++++++++++++++++++++++++++++++++++
 9 files changed, 742 insertions(+), 3 deletions(-)

diff --git a/Documentation/trace/wprobetrace.rst b/Documentation/trace/wprobetrace.rst
index 31cc68b464e9..df8985283312 100644
--- a/Documentation/trace/wprobetrace.rst
+++ b/Documentation/trace/wprobetrace.rst
@@ -76,3 +76,110 @@ Wprobe event does not disable itself even if the module is unloaded.
 For example, if you add a wprobe event on a module variable, and then
 unload the module, the wprobe event will still be enabled. This is for
 watching the address is used unexpectedly after the module is unloaded.
+
+Combination with trigger action
+-------------------------------
+The event trigger action can extend the utilization of this wprobe.
+
+- set_wprobe:WPEVENT:FIELD[+|-ADJUST][:COUNT]
+- clear_wprobe:WPEVENT[:FIELD[+|-ADJUST][:COUNT]]
+
+Set these triggers to the target event, then the WPROBE event will be
+setup to trace the memory access at FIELD[+|-ADJUST] address.
+When clear_wprobe is hit, if FIELD is NOT specified, the WPEVENT is
+forcibly cleared. If FIELD[+|-ADJUST] is set, it clears WPEVENT only
+if its watching address is the same as the FIELD[+|-ADJUST] value.
+If COUNT is specified, it will set/clear WPEVENT only if it hits COUNT
+times.
+
+Notes:
+- set_wprobe only works on the wprobe which is NOT set a valid address yet,
+  and it must be enabled after the trigger is set.
+- clear_wprobe only works on the wprobe which is set a valid address, and it
+  will be soft-disabled after the trigger is cleared.
+- Therefore, if a trigger sets/clears a wprobe, other/same trigger events
+  will not work (on the same event) while the wprobe is set.
+
+The set_wprobe trigger does not change the type and length, these
+must be set when creating a new wprobe.
+
+The WPROBE event must be disabled when setting the new trigger
+and it will be busy afterwards. Recommended usage is to add a new
+wprobe at invalid dummy address (-1) and keep disabled.
+
+Wprobe triggers only support target addresses in kernel memory. If a
+set_wprobe trigger evaluates to a user-space memory address or NULL
+pointer, the trigger action ignores the update and skips setting the
+watchpoint.
+
+Wprobe triggers are not supported on kprobe_events, because kprobes
+themselves can use software breakpoints which conflicts with wprobe
+operation.
+
+
+For example, trace the first 8 bytes of the dentry data structure passed
+to do_truncate() until it is deleted by dentry_kill().
+(Note: all tracefs setup uses '>>' so that it does not kick do_truncate())
+::
+
+  # echo 'w:watch rw@-1:8 address=$addr value=+0($addr)' >> dynamic_events
+  # echo 'f:truncate do_truncate dentry=$arg2' >> dynamic_events
+  # echo 'set_wprobe:watch:dentry' >> events/fprobes/truncate/trigger
+  # echo 'f:dentry_kill dentry_kill dentry=$arg1' >> dynamic_events
+  # echo 'clear_wprobe:watch:dentry' >> events/fprobes/dentry_kill/trigger
+  # echo 1 >> events/fprobes/truncate/enable
+  # echo 1 >> events/fprobes/dentry_kill/enable
+
+  # echo aaa > /tmp/hoge
+  # echo bbb > /tmp/hoge
+  # echo ccc > /tmp/hoge
+  # rm /tmp/hoge
+
+Then, the trace data will show::
+
+ # tracer: nop
+ #
+ # entries-in-buffer/entries-written: 32/32   #P:8
+ #
+ #                                _-----=> irqs-off/BH-disabled
+ #                               / _----=> need-resched
+ #                              | / _---=> hardirq/softirq
+ #                              || / _--=> preempt-depth
+ #                              ||| / _-=> migrate-disable
+ #                              |||| /     delay
+ #           TASK-PID     CPU#  |||||  TIMESTAMP  FUNCTION
+ #              | |         |   |||||     |         |
+               sh-107     [004] ...1.     9.990418: dentry_kill: (dentry_kill+0x0/0x2c0) dentry=0xffff888004ad6618
+               sh-107     [004] ...1.     9.990914: dentry_kill: (dentry_kill+0x0/0x2c0) dentry=0xffff888004b3de78
+               sh-107     [004] ...1.     9.993175: dentry_kill: (dentry_kill+0x0/0x2c0) dentry=0xffff8880049ddd40
+               sh-107     [004] .....     9.995198: truncate: (do_truncate+0x4/0x120) dentry=0xffff8880048083a8
+               sh-107     [004] ...1.     9.995389: dentry_kill: (dentry_kill+0x0/0x2c0) dentry=0xffff8880049db998
+               sh-107     [004] ..Zff     9.997503: watch: (lookup_fast+0xaa/0x150) address=0xffff8880048083a8 value=0x8200080
+               sh-107     [004] ..Zff     9.997509: watch: (path_openat+0x211/0xda0) address=0xffff8880048083a8 value=0x8200080
+               sh-107     [004] ..Zff     9.997514: watch: (path_openat+0xa56/0xda0) address=0xffff8880048083a8 value=0x8200080
+               sh-107     [004] ..Zff     9.997518: watch: (path_openat+0xae2/0xda0) address=0xffff8880048083a8 value=0x8200080
+               sh-107     [004] .....     9.997521: truncate: (do_truncate+0x4/0x120) dentry=0xffff8880048083a8
+               sh-107     [004] ...1.     9.997582: dentry_kill: (dentry_kill+0x0/0x2c0) dentry=0xffff888004808270
+               sh-107     [004] ...1.     9.999365: dentry_kill: (dentry_kill+0x0/0x2c0) dentry=0xffff8880049db728
+               sh-107     [004] ...1.     9.999388: dentry_kill: (dentry_kill+0x0/0x2c0) dentry=0xffff888004b1c000
+               rm-113     [005] ..Zff    10.000965: watch: (lookup_fast+0xaa/0x150) address=0xffff8880048083a8 value=0x8200080
+               rm-113     [005] ..Zff    10.000971: watch: (path_lookupat+0x97/0x1e0) address=0xffff8880048083a8 value=0x8200080
+               rm-113     [005] ..Zff    10.000984: watch: (lookup_fast+0xaa/0x150) address=0xffff8880048083a8 value=0x8200080
+               rm-113     [005] ..Zff    10.000988: watch: (path_lookupat+0x97/0x1e0) address=0xffff8880048083a8 value=0x8200080
+               rm-113     [005] ..Zff    10.001010: watch: (lookup_one_qstr_excl+0x28/0x140) address=0xffff8880048083a8 value=0x8200080
+               rm-113     [005] ..Zff    10.001014: watch: (lookup_one_qstr_excl+0xd1/0x140) address=0xffff8880048083a8 value=0x8200080
+               rm-113     [005] ..Zff    10.001018: watch: (may_delete_dentry+0x1c/0x200) address=0xffff8880048083a8 value=0x8200080
+               rm-113     [005] ..Zff    10.001021: watch: (may_delete_dentry+0x195/0x200) address=0xffff8880048083a8 value=0x8200080
+               rm-113     [005] ..Zff    10.001031: watch: (vfs_unlink+0x5e/0x260) address=0xffff8880048083a8 value=0x8200080
+               rm-113     [005] d.Z..    10.001067: watch: (d_make_discardable+0x1b/0x40) address=0xffff8880048083a8 value=0x8200080
+               rm-113     [005] d.Z..    10.001071: watch: (d_make_discardable+0x29/0x40) address=0xffff8880048083a8 value=0x200080
+               rm-113     [005] ...1.    10.001072: dentry_kill: (dentry_kill+0x0/0x2c0) dentry=0xffff8880048083a8
+               rm-113     [005] ...1.    10.001218: dentry_kill: (dentry_kill+0x0/0x2c0) dentry=0xffff8880048083a8
+               sh-107     [004] ...1.    10.001416: dentry_kill: (dentry_kill+0x0/0x2c0) dentry=0xffff8880049db110
+               sh-107     [004] ...1.    10.001444: dentry_kill: (dentry_kill+0x0/0x2c0) dentry=0xffff8880049db248
+               sh-107     [004] ...1.    10.001500: dentry_kill: (dentry_kill+0x0/0x2c0) dentry=0xffff888004ad6618
+               sh-107     [004] ...1.    10.002067: dentry_kill: (dentry_kill+0x0/0x2c0) dentry=0xffff888004b41e78
+               sh-107     [004] ...1.    10.904920: dentry_kill: (dentry_kill+0x0/0x2c0) dentry=0xffff888004b41e78
+               sh-107     [004] ...1.    10.905129: dentry_kill: (dentry_kill+0x0/0x2c0) dentry=0xffff888004ad6618
+
+You can see the watch event is correctly configured on the dentry.
diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h
index 43ffd9a76d88..f81a5308c116 100644
--- a/include/linux/trace_events.h
+++ b/include/linux/trace_events.h
@@ -738,6 +738,7 @@ enum event_trigger_type {
 	ETT_EVENT_HIST		= (1 << 4),
 	ETT_HIST_ENABLE		= (1 << 5),
 	ETT_EVENT_EPROBE	= (1 << 6),
+	ETT_EVENT_WPROBE	= (1 << 7),
 };
 
 extern int filter_match_preds(struct event_filter *filter, void *rec);
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index d9b6fa5c35d9..5fd8ed63c516 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -876,6 +876,16 @@ config WPROBE_EVENTS
 	  Those events can be inserted wherever hardware breakpoints can be
 	  set, and record accessed memory address and values.
 
+config WPROBE_TRIGGERS
+	depends on WPROBE_EVENTS
+	depends on HAVE_MODIFY_LOCAL_HW_BREAKPOINT_ADDR
+	bool
+	default y
+	help
+	  This adds an event trigger which will set the wprobe on a specific
+	  field of an event. This allows user to trace the memory access of
+	  an address pointed by the event field.
+
 config BPF_EVENTS
 	depends on BPF_SYSCALL
 	depends on (KPROBE_EVENTS || UPROBE_EVENTS) && PERF_EVENTS
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 40c3e1543f6e..0a38eda359c1 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -4366,6 +4366,10 @@ static const char readme_msg[] =
 	"\t   trigger: traceon, traceoff\n"
 	"\t            enable_event:<system>:<event>\n"
 	"\t            disable_event:<system>:<event>\n"
+#ifdef CONFIG_WPROBE_TRIGGERS
+	"\t            set_wprobe:<wprobe-event>:<field>[+|-<offset>]\n"
+	"\t            clear_wprobe:<wprobe-event>[:<field>[+|-<offset>]]\n"
+#endif
 #ifdef CONFIG_HIST_TRIGGERS
 	"\t            enable_hist:<system>:<event>\n"
 	"\t            disable_hist:<system>:<event>\n"
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 18588c550a98..a61f840b18bd 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -1983,6 +1983,7 @@ trigger_data_alloc(struct event_command *cmd_ops, char *cmd, char *param,
 		   void *private_data);
 extern void trigger_data_free(struct event_trigger_data *data);
 extern int event_trigger_init(struct event_trigger_data *data);
+extern void event_trigger_free(struct event_trigger_data *data);
 extern int trace_event_trigger_enable_disable(struct trace_event_file *file,
 					      int trigger_enable);
 extern void update_cond_flag(struct trace_event_file *file);
diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c
index 149300cc5e8a..120e6ec634b7 100644
--- a/kernel/trace/trace_events_trigger.c
+++ b/kernel/trace/trace_events_trigger.c
@@ -589,7 +589,7 @@ int event_trigger_init(struct event_trigger_data *data)
  * Usually used directly as the @free method in event trigger
  * implementations.
  */
-static void
+void
 event_trigger_free(struct event_trigger_data *data)
 {
 	if (WARN_ON_ONCE(data->ref <= 0))
diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
index 64e7e363e8e2..77266e042418 100644
--- a/kernel/trace/trace_probe.c
+++ b/kernel/trace/trace_probe.c
@@ -20,7 +20,7 @@
 #undef C
 #define C(a, b)		b
 
-static const char *trace_probe_err_text[] = { ERRORS };
+const char *trace_probe_err_text[] = { ERRORS };
 
 static const char *reserved_field_names[] = {
 	"common_type",
diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h
index f20cafb87cc6..1e11077ead67 100644
--- a/kernel/trace/trace_probe.h
+++ b/kernel/trace/trace_probe.h
@@ -636,7 +636,12 @@ extern int traceprobe_define_arg_fields(struct trace_event_call *event_call,
 	C(TYPECAST_SYM_OFFSET,	"@SYM+/-OFFSET with typecast needs parentheses"),	\
 	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"),
+	C(WPROBE_NO_SIBLING,	"Watchpoint probe does not support sibling probes"), \
+	C(WPROBE_ON_KPROBE,	"Wprobe trigger is not supported on kprobe event"), \
+	C(WPROBE_NOT_FOUND,	"Target wprobe event is not found"),		\
+	C(WPROBE_BUSY,		"Target wprobe event is already enabled"),	\
+	C(WPROBE_NEED_FIELD,	"Wprobe trigger requires a target field"),	\
+	C(WPROBE_BAD_FIELD,	"Target field must be pointer size"),
 
 #undef C
 #define C(a, b)		TP_ERR_##a
@@ -660,6 +665,8 @@ void __trace_probe_log_err(int offset, int err);
 
 DEFINE_FREE(trace_probe_log_clear, const char *, if (_T) trace_probe_log_clear())
 
+extern const char *trace_probe_err_text[];
+
 #define trace_probe_log_err(offs, err)	\
 	__trace_probe_log_err(offs, TP_ERR_##err)
 
diff --git a/kernel/trace/trace_wprobe.c b/kernel/trace/trace_wprobe.c
index 9c6100b63e8d..3cf8786ef0ee 100644
--- a/kernel/trace/trace_wprobe.c
+++ b/kernel/trace/trace_wprobe.c
@@ -6,7 +6,9 @@
  */
 #define pr_fmt(fmt)	"trace_wprobe: " fmt
 
+#include <linux/atomic.h>
 #include <linux/compiler.h>
+#include <linux/errno.h>
 #include <linux/hw_breakpoint.h>
 #include <linux/kallsyms.h>
 #include <linux/list.h>
@@ -15,11 +17,16 @@
 #include <linux/perf_event.h>
 #include <linux/rculist.h>
 #include <linux/security.h>
+#include <linux/spinlock.h>
 #include <linux/tracepoint.h>
 #include <linux/uaccess.h>
+#include <linux/workqueue.h>
+#include <linux/irq_work.h>
+#include <linux/preempt.h>
 
 #include <asm/ptrace.h>
 
+#include "trace.h"
 #include "trace_dynevent.h"
 #include "trace_probe.h"
 #include "trace_probe_kernel.h"
@@ -51,6 +58,17 @@ struct trace_wprobe {
 	int			len;
 	int			type;
 	const char		*symbol;
+	raw_spinlock_t		lock;
+	struct irq_work		irq_work;
+	struct work_struct	work;
+	atomic_t		missed;
+	/*
+	 * work_pending is set to 1 before irq_work_queue() and cleared to 0
+	 * after wprobe_work_func() finishes on_each_cpu(). This prevents a
+	 * new trigger from overwriting tw->addr while the work is propagating
+	 * the old address to per-CPU debug registers via IPI.
+	 */
+	atomic_t		work_pending;
 	struct trace_probe	tp;
 };
 
@@ -199,14 +217,65 @@ static int __register_trace_wprobe(struct trace_wprobe *tw)
 static void __unregister_trace_wprobe(struct trace_wprobe *tw)
 {
 	if (tw->bp_event) {
+		irq_work_sync(&tw->irq_work);
+		cancel_work_sync(&tw->work);
 		unregister_wide_hw_breakpoint(tw->bp_event);
 		tw->bp_event = NULL;
 	}
 }
 
+static int trace_wprobe_update_local(struct trace_wprobe *tw, unsigned long addr)
+{
+	struct perf_event * __percpu *pevent;
+	struct perf_event *bp;
+
+	pevent = tw->bp_event;
+	if (!pevent)
+		return -EINVAL;
+
+	bp = *this_cpu_ptr(pevent);
+	if (!bp)
+		return -EINVAL;
+
+	return modify_local_hw_breakpoint_addr(bp, addr);
+}
+
+static void wprobe_smp_update_func(void *info)
+{
+	struct trace_wprobe *tw = info;
+	unsigned long addr = READ_ONCE(tw->addr);
+
+	if (trace_wprobe_update_local(tw, addr))
+		atomic_inc(&tw->missed);
+}
+
+static void wprobe_work_func(struct work_struct *work)
+{
+	struct trace_wprobe *tw = container_of(work, struct trace_wprobe, work);
+
+	on_each_cpu(wprobe_smp_update_func, tw, true);
+	/*
+	 * Clear work_pending after all CPUs have updated their local debug
+	 * registers.  A new trigger may now update tw->addr and queue a new
+	 * irq_work.
+	 */
+	atomic_set(&tw->work_pending, 0);
+}
+
+static void wprobe_irq_work_func(struct irq_work *irq_work)
+{
+	struct trace_wprobe *tw = container_of(irq_work, struct trace_wprobe, irq_work);
+
+	schedule_work(&tw->work);
+}
+
 static void free_trace_wprobe(struct trace_wprobe *tw)
 {
 	if (tw) {
+		if (tw->work.func) {
+			irq_work_sync(&tw->irq_work);
+			cancel_work_sync(&tw->work);
+		}
 		trace_probe_cleanup(&tw->tp);
 		kfree(tw->symbol);
 		kfree(tw);
@@ -231,6 +300,12 @@ static struct trace_wprobe *alloc_trace_wprobe(const char *group,
 	if (!tw)
 		return ERR_PTR(-ENOMEM);
 
+	raw_spin_lock_init(&tw->lock);
+	init_irq_work(&tw->irq_work, wprobe_irq_work_func);
+	INIT_WORK(&tw->work, wprobe_work_func);
+	atomic_set(&tw->missed, 0);
+	atomic_set(&tw->work_pending, 0);
+
 	if (symbol) {
 		tw->symbol = kstrdup(symbol, GFP_KERNEL);
 		if (!tw->symbol)
@@ -509,6 +584,11 @@ static bool trace_wprobe_is_valid_addr(unsigned long addr, int len)
 	return true;
 }
 
+#ifdef CONFIG_WPROBE_TRIGGERS
+static u64 wprobe_trigger_clear_target __aligned(8);
+#define WPROBE_DEFAULT_CLEAR_ADDRESS ((unsigned long)&wprobe_trigger_clear_target)
+#endif
+
 static int parse_address_spec(const char *spec, unsigned long *addr, int *type,
 			      int *len, char **symbol, int *offset)
 {
@@ -572,7 +652,13 @@ static int parse_address_spec(const char *spec, unsigned long *addr, int *type,
 		}
 	}
 
+#ifdef CONFIG_WPROBE_TRIGGERS
+	if (strcmp(at + 1, "-1") == 0) {
+		_addr = WPROBE_DEFAULT_CLEAR_ADDRESS;
+	} else if (kstrtoul(at + 1, 0, &_addr) != 0) {
+#else
 	if (kstrtoul(at + 1, 0, &_addr) != 0) {
+#endif
 		char *off_str = strpbrk(at + 1, "+-");
 
 		if (off_str) {
@@ -756,6 +842,10 @@ static int trace_wprobe_show(struct seq_file *m, struct dyn_event *ev)
 				   tw->offset, len);
 		else
 			seq_printf(m, " %s@%s:%d", type_str, tw->symbol, len);
+#ifdef CONFIG_WPROBE_TRIGGERS
+	} else if (tw->addr == WPROBE_DEFAULT_CLEAR_ADDRESS) {
+		seq_printf(m, " %s@-1:%d", type_str, len);
+#endif
 	} else {
 		seq_printf(m, " %s@0x%lx:%d", type_str, tw->addr, len);
 	}
@@ -773,3 +863,522 @@ static __init int init_wprobe_trace(void)
 }
 fs_initcall(init_wprobe_trace);
 
+#ifdef CONFIG_WPROBE_TRIGGERS
+
+#define SET_WPROBE_STR		"set_wprobe"
+#define CLEAR_WPROBE_STR	"clear_wprobe"
+#define wprobe_trigger_log_err(file, glob, offs, err) \
+	tracing_log_err((file)->tr, "wprobe_trigger", glob, \
+			trace_probe_err_text, TP_ERR_##err, offs)
+
+struct wprobe_trigger_data {
+	struct rcu_head		rcu;
+	struct trace_event_file	*file;
+	struct trace_wprobe	*tw;
+	int			offset;
+	long			adjust;
+	const char		*field;
+	bool			clear;
+};
+
+static void wprobe_trigger(struct event_trigger_data *data,
+			   struct trace_buffer *buffer,  void *rec,
+			   struct ring_buffer_event *event)
+{
+	struct wprobe_trigger_data *wprobe_data = data->private_data;
+	struct trace_wprobe *tw = wprobe_data->tw;
+	unsigned long addr = 0, flags;
+	bool changed = false;
+
+	if (in_nmi()) {
+		atomic_inc(&tw->missed);
+		return;
+	}
+
+	if (wprobe_data->field) {
+		addr = *(unsigned long *)((char *)rec + wprobe_data->offset);
+		addr += wprobe_data->adjust;
+	}
+
+	raw_spin_lock_irqsave(&tw->lock, flags);
+
+	if (!wprobe_data->clear) {
+		if (!trace_wprobe_is_valid_addr(addr, tw->len)) {
+			atomic_inc(&tw->missed);
+			goto out;
+		}
+		if (tw->addr == WPROBE_DEFAULT_CLEAR_ADDRESS) {
+			/* Skip if a previous work is still propagating the address */
+			if (atomic_read(&tw->work_pending)) {
+				atomic_inc(&tw->missed);
+				goto out;
+			}
+			WRITE_ONCE(tw->addr, addr);
+			changed = true;
+			clear_bit(EVENT_FILE_FL_SOFT_DISABLED_BIT, &wprobe_data->file->flags);
+		}
+	} else {
+		if (tw->addr != WPROBE_DEFAULT_CLEAR_ADDRESS) {
+			/* Skip if a previous work is still propagating the address */
+			if (atomic_read(&tw->work_pending)) {
+				atomic_inc(&tw->missed);
+				goto out;
+			}
+			if (!wprobe_data->field || tw->addr == addr) {
+				WRITE_ONCE(tw->addr, WPROBE_DEFAULT_CLEAR_ADDRESS);
+				changed = true;
+				set_bit(EVENT_FILE_FL_SOFT_DISABLED_BIT, &wprobe_data->file->flags);
+			}
+		}
+	}
+
+	if (changed) {
+		/*
+		 * Mark the work as pending before queuing irq_work so that
+		 * subsequent triggers skip updating tw->addr until the work
+		 * has finished propagating the address to all CPUs.
+		 */
+		atomic_set(&tw->work_pending, 1);
+		irq_work_queue(&tw->irq_work);
+	}
+
+out:
+	raw_spin_unlock_irqrestore(&tw->lock, flags);
+}
+
+static void free_wprobe_trigger_data(struct wprobe_trigger_data *wprobe_data)
+{
+	if (wprobe_data) {
+		kfree(wprobe_data->field);
+		kfree(wprobe_data);
+	}
+}
+DEFINE_FREE(free_wprobe_trigger_data, struct wprobe_trigger_data *, free_wprobe_trigger_data(_T));
+
+static void free_private_wprobe_trigger_data(struct event_trigger_data *data)
+{
+	free_wprobe_trigger_data(data->private_data);
+}
+
+static int wprobe_trigger_print(struct seq_file *m,
+			       struct event_trigger_data *data)
+{
+	struct wprobe_trigger_data *wprobe_data = data->private_data;
+	int missed = atomic_read(&wprobe_data->tw->missed);
+
+	if (wprobe_data->clear) {
+		seq_printf(m, "%s:%s", CLEAR_WPROBE_STR,
+			   trace_event_name(wprobe_data->file->event_call));
+		if (wprobe_data->field) {
+			seq_printf(m, ":%s%+ld",
+				   wprobe_data->field, wprobe_data->adjust);
+		}
+	} else {
+		seq_printf(m, "%s:%s:%s%+ld", SET_WPROBE_STR,
+			   trace_event_name(wprobe_data->file->event_call),
+			   wprobe_data->field, wprobe_data->adjust);
+	}
+
+	if (data->count == -1)
+		seq_puts(m, ":unlimited");
+	else
+		seq_printf(m, ":count=%ld", data->count);
+
+	if (data->filter_str)
+		seq_printf(m, " if %s", data->filter_str);
+
+	if (missed)
+		seq_printf(m, " # missed: %d", missed);
+
+	seq_putc(m, '\n');
+
+	return 0;
+}
+
+static struct wprobe_trigger_data *
+wprobe_trigger_alloc(struct trace_wprobe *tw, struct trace_event_file *file,
+		     bool clear)
+{
+	struct wprobe_trigger_data *wprobe_data;
+
+	wprobe_data = kzalloc_obj(*wprobe_data);
+	if (!wprobe_data)
+		return NULL;
+
+	wprobe_data->tw = tw;
+	wprobe_data->clear = clear;
+	wprobe_data->file = file;
+
+	return wprobe_data;
+}
+
+static void wprobe_trigger_free(struct event_trigger_data *data)
+{
+	struct wprobe_trigger_data *wprobe_data = data->private_data;
+
+	if (WARN_ON_ONCE(data->ref <= 0))
+		return;
+
+	data->ref--;
+	if (!data->ref) {
+		/* Remove the SOFT_MODE flag */
+		trace_event_enable_disable(wprobe_data->file, 0, 1);
+		trace_event_put_ref(wprobe_data->file->event_call);
+		trigger_data_free(data);
+	}
+}
+
+static int wprobe_trigger_cmd_parse(struct event_command *cmd_ops,
+				    struct trace_event_file *file,
+				    char *glob, char *cmd,
+				    char *param_and_filter)
+{
+	/*
+	 * set_wprobe:EVENT:FIELD[+OFFS]
+	 * clear_wprobe:EVENT[:FIELD[+OFFS]]
+	 */
+	struct wprobe_trigger_data *wprobe_data = NULL;
+	struct event_trigger_data *trigger_data = NULL;
+	struct trace_event_file *wprobe_file;
+	struct trace_array *tr = file->tr;
+	char *event_str, *field_str, *comment;
+	struct ftrace_event_field *field;
+	struct trace_event_call *event;
+	bool remove, clear = false;
+	unsigned long orig_addr = 0;
+	struct trace_wprobe *tw;
+	char *param, *filter;
+	int ret;
+
+	remove = event_trigger_check_remove(glob);
+
+	if (!strcmp(cmd, CLEAR_WPROBE_STR))
+		clear = true;
+
+	if (param_and_filter) {
+		/* Recover original trigger string to show the error log correctly. */
+		if (*(param_and_filter - 1) == '\0')
+			*(param_and_filter - 1) = ':';
+		comment = strchr(param_and_filter, '#');
+		if (comment)
+			*comment = '\0';
+	}
+
+	if (event_trigger_empty_param(param_and_filter)) {
+		wprobe_trigger_log_err(file, glob, strlen(cmd) + 1, WPROBE_NOT_FOUND);
+		return -EINVAL;
+	}
+
+	ret = event_trigger_separate_filter(param_and_filter, &param, &filter, true);
+	if (ret)
+		return ret;
+
+	if (file->event_call->flags & TRACE_EVENT_FL_KPROBE) {
+		wprobe_trigger_log_err(file, glob, 0, WPROBE_ON_KPROBE);
+		return -EOPNOTSUPP;
+	}
+
+	event_str = strsep(&param, ":");
+
+	/* Find target wprobe */
+	tw = find_trace_wprobe(event_str, WPROBE_EVENT_SYSTEM);
+	if (!tw) {
+		wprobe_trigger_log_err(file, glob, event_str - glob, WPROBE_NOT_FOUND);
+		return -ENOENT;
+	}
+	/* The target wprobe must not be used (unless clear) */
+	if (!remove && !clear && trace_probe_is_enabled(&tw->tp)) {
+		wprobe_trigger_log_err(file, glob, event_str - glob, WPROBE_BUSY);
+		return -EBUSY;
+	}
+
+	wprobe_file = find_event_file(tr, WPROBE_EVENT_SYSTEM, event_str);
+	if (!wprobe_file) {
+		wprobe_trigger_log_err(file, glob, event_str - glob, WPROBE_NOT_FOUND);
+		return -EINVAL;
+	}
+
+	wprobe_data = wprobe_trigger_alloc(tw, wprobe_file, clear);
+	if (!wprobe_data)
+		return -ENOMEM;
+
+	/* clear_wprobe does not need field, but can have optional field. */
+	if (!clear) {
+		char *offs;
+
+		/* Find target field, which must be equivalent to "void *" */
+		field_str = strsep(&param, ":");
+		if (!field_str) {
+			wprobe_trigger_log_err(file, glob, strlen(glob), WPROBE_NEED_FIELD);
+			ret = -EINVAL;
+			goto out_free;
+		}
+
+		offs = strpbrk(field_str, "+-");
+		if (offs) {
+			long val;
+
+			if (kstrtol(offs, 0, &val) < 0) {
+				wprobe_trigger_log_err(file, glob, offs - glob, BAD_DEREF_OFFS);
+				ret = -EINVAL;
+				goto out_free;
+			}
+			wprobe_data->adjust = val;
+			*offs = '\0';
+		}
+
+		event = file->event_call;
+		field = trace_find_event_field(event, field_str);
+		if (!field) {
+			wprobe_trigger_log_err(file, glob, field_str - glob, NO_EVENT_FIELD);
+			ret = -ENOENT;
+			goto out_free;
+		}
+
+		if (field->size != sizeof(void *)) {
+			wprobe_trigger_log_err(file, glob, field_str - glob, WPROBE_BAD_FIELD);
+			ret = -ENOEXEC;
+			goto out_free;
+		}
+		wprobe_data->offset = field->offset;
+		wprobe_data->field = kstrdup(field_str, GFP_KERNEL);
+		if (!wprobe_data->field) {
+			ret = -ENOMEM;
+			goto out_free;
+		}
+	} else if (param && (isalpha(param[0]) || param[0] == '_')) {
+		if (strncmp(param, "count=", 6) != 0 &&
+		    strncmp(param, "unlimited", 9) != 0) {
+			char *offs;
+
+			field_str = strsep(&param, ":");
+			offs = strpbrk(field_str, "+-");
+			if (offs) {
+				long val;
+
+				if (kstrtol(offs, 0, &val) < 0) {
+					wprobe_trigger_log_err(file, glob,
+							       offs - glob,
+							       BAD_DEREF_OFFS);
+					ret = -EINVAL;
+					goto out_free;
+				}
+				wprobe_data->adjust = val;
+				*offs = '\0';
+			}
+
+			event = file->event_call;
+			field = trace_find_event_field(event, field_str);
+			if (!field) {
+				wprobe_trigger_log_err(file, glob,
+						       field_str - glob,
+						       NO_EVENT_FIELD);
+				ret = -ENOENT;
+				goto out_free;
+			}
+
+			if (field->size != sizeof(void *)) {
+				wprobe_trigger_log_err(file, glob,
+						       field_str - glob,
+						       WPROBE_BAD_FIELD);
+				ret = -ENOEXEC;
+				goto out_free;
+			}
+			wprobe_data->offset = field->offset;
+			wprobe_data->field = kstrdup(field_str, GFP_KERNEL);
+			if (!wprobe_data->field) {
+				ret = -ENOMEM;
+				goto out_free;
+			}
+		}
+	}
+
+	trigger_data = trigger_data_alloc(cmd_ops, cmd, param, wprobe_data);
+	if (!trigger_data) {
+		ret = -ENOMEM;
+		goto out_free;
+	}
+
+	trigger_data->private_data_free = free_private_wprobe_trigger_data;
+
+	if (remove) {
+		event_trigger_unregister(cmd_ops, file, glob+1, trigger_data);
+		trigger_data_free(trigger_data);
+		return 0;
+	}
+
+	/* Up the trigger_data count to make sure nothing frees it on failure */
+	event_trigger_init(trigger_data);
+
+	ret = event_trigger_parse_num(param, trigger_data);
+	if (ret) {
+		wprobe_trigger_log_err(file, glob, param - glob, BAD_IMM);
+		goto out_free_trigger;
+	}
+
+	ret = event_trigger_set_filter(cmd_ops, file, filter, trigger_data);
+	if (ret < 0)
+		goto out_free_trigger;
+
+	/* Soft-enable (register) wprobe event on WPROBE_DEFAULT_CLEAR_ADDRESS */
+	if (!trace_event_try_get_ref(wprobe_file->event_call)) {
+		ret = -ENODEV;
+		goto out_free_trigger;
+	}
+
+	if (!clear) {
+		orig_addr = tw->addr;
+		WRITE_ONCE(tw->addr, WPROBE_DEFAULT_CLEAR_ADDRESS);
+	}
+
+	ret = trace_event_enable_disable(wprobe_file, 1, 1);
+	if (ret < 0) {
+		if (!clear)
+			WRITE_ONCE(tw->addr, orig_addr);
+		goto out_put;
+	}
+
+	ret = event_trigger_register(cmd_ops, file, glob, trigger_data);
+	if (ret)
+		goto out_disable;
+
+	/* Balance the event_trigger_init() at registration start */
+	event_trigger_free(trigger_data);
+	return 0;
+
+out_disable:
+	if (!clear)
+		WRITE_ONCE(tw->addr, orig_addr);
+	trace_event_enable_disable(wprobe_file, 0, 1);
+out_put:
+	trace_event_put_ref(wprobe_file->event_call);
+out_free_trigger:
+	event_trigger_reset_filter(cmd_ops, trigger_data);
+	trigger_data_free(trigger_data);
+	return ret;
+
+out_free:
+	free_wprobe_trigger_data(wprobe_data);
+	return ret;
+}
+
+/* Return event_trigger_data if there is a trigger which points the same wprobe */
+static struct event_trigger_data *
+wprobe_trigger_find_same(struct event_trigger_data *test,
+			 struct trace_event_file *file)
+{
+	struct wprobe_trigger_data *test_wprobe_data = test->private_data;
+	struct wprobe_trigger_data *wprobe_data;
+	struct event_trigger_data *iter;
+
+	list_for_each_entry(iter, &file->triggers, list) {
+		wprobe_data = iter->private_data;
+		if (!wprobe_data ||
+		    iter->cmd_ops->trigger_type !=
+		    test->cmd_ops->trigger_type)
+			continue;
+		if (wprobe_data->tw == test_wprobe_data->tw &&
+		    wprobe_data->clear == test_wprobe_data->clear)
+			return iter;
+	}
+	return NULL;
+}
+
+static int wprobe_register_trigger(char *glob,
+				   struct event_trigger_data *data,
+				   struct trace_event_file *file)
+{
+	int ret = 0;
+
+	lockdep_assert_held(&event_mutex);
+
+	/* The same wprobe is not accept on the same file (event) */
+	if (wprobe_trigger_find_same(data, file))
+		return -EEXIST;
+
+	if (data->cmd_ops->init) {
+		ret = data->cmd_ops->init(data);
+		if (ret < 0)
+			return ret;
+	}
+
+	list_add_rcu(&data->list, &file->triggers);
+
+	update_cond_flag(file);
+	ret = trace_event_trigger_enable_disable(file, 1);
+	if (ret < 0) {
+		list_del_rcu(&data->list);
+		update_cond_flag(file);
+		if (data->cmd_ops->free)
+			data->cmd_ops->free(data);
+	}
+	return ret;
+}
+
+static void wprobe_unregister_trigger(char *glob,
+				      struct event_trigger_data *test,
+				      struct trace_event_file *file)
+{
+	struct event_trigger_data *data;
+
+	lockdep_assert_held(&event_mutex);
+
+	data = wprobe_trigger_find_same(test, file);
+	if (!data)
+		return;
+
+	list_del_rcu(&data->list);
+	trace_event_trigger_enable_disable(file, 0);
+	update_cond_flag(file);
+	tracepoint_synchronize_unregister();
+	if (data->cmd_ops->free)
+		data->cmd_ops->free(data);
+}
+
+static struct event_command trigger_wprobe_set_cmd = {
+	.name			= SET_WPROBE_STR,
+	.trigger_type		= ETT_EVENT_WPROBE,
+	/* This triggers after when the event is recorded. */
+	.flags			= EVENT_CMD_FL_NEEDS_REC,
+	.parse			= wprobe_trigger_cmd_parse,
+	.reg			= wprobe_register_trigger,
+	.unreg			= wprobe_unregister_trigger,
+	.set_filter		= set_trigger_filter,
+	.trigger		= wprobe_trigger,
+	.count_func		= event_trigger_count,
+	.print			= wprobe_trigger_print,
+	.init			= event_trigger_init,
+	.free			= wprobe_trigger_free,
+};
+
+static struct event_command trigger_wprobe_clear_cmd = {
+	.name			= CLEAR_WPROBE_STR,
+	.trigger_type		= ETT_EVENT_WPROBE,
+	/* This triggers after when the event is recorded. */
+	.flags			= EVENT_CMD_FL_NEEDS_REC,
+	.parse			= wprobe_trigger_cmd_parse,
+	.reg			= wprobe_register_trigger,
+	.unreg			= wprobe_unregister_trigger,
+	.set_filter		= set_trigger_filter,
+	.trigger		= wprobe_trigger,
+	.count_func		= event_trigger_count,
+	.print			= wprobe_trigger_print,
+	.init			= event_trigger_init,
+	.free			= wprobe_trigger_free,
+};
+
+static __init int init_trigger_wprobe_cmds(void)
+{
+	int ret;
+
+	ret = register_event_command(&trigger_wprobe_set_cmd);
+	if (WARN_ON(ret < 0))
+		return ret;
+	ret = register_event_command(&trigger_wprobe_clear_cmd);
+	if (WARN_ON(ret < 0))
+		unregister_event_command(&trigger_wprobe_set_cmd);
+
+	return ret;
+}
+fs_initcall(init_trigger_wprobe_cmds);
+#endif /* CONFIG_WPROBE_TRIGGERS */

[PATCH v15 10/12] selftests: tracing: Add wprobe trigger testcase

[Masami Hiramatsu (Google)]

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

Add a testcase for checking wprobe trigger. This sets set_wprobe and
clear_wprobe triggers on fprobe event and static trace event to
monitor memory accesses within the trace-events-sample kernel module.
Also add a testcase for verifying wprobe trigger syntax error logging.

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

Assisted-by: Antigravity:gemini-3.8-flash
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
---
Changes in v15:
 - Add explicit failure checks with fail helper in trigger-wprobe.tc.
 - Declare fprobe README requirement in trigger-wprobe.tc.
 - Add trigger file check to trigger-wprobe-syntax-errors.tc requires line.
 - Fix subject tag to tracing.
Changes in v14:
 - Update dummy wprobe event definition to use '-1' instead of '0'.
 - Add BTF argument dependency requirement in trigger-wprobe.tc.
 - Add delay before clear_trace in trigger-wprobe.tc to avoid race with
   clear_wprobe trigger execution.
Changes in v13:
 - Look up target function dynamically in trigger-wprobe-syntax-errors.tc.
 - Disable set_wprobe trigger before verifying clear_wprobe in
   trigger-wprobe.tc to avoid race condition with sample_timer_cb.
Changes in v12:
 - Add trigger-wprobe-syntax-errors.tc for verifying wprobe trigger syntax
   error logging.
 - Fix requires line in trigger-wprobe-syntax-errors.tc so test is not
   evaluated as unsupported prior to execution.
 - Define dfd=$arg1 fetcharg on testevent for trigger syntax checks.
Changes in v11:
 - Update testcase to use trace-events-sample kernel module instead of
   VFS file operations.
---
 tools/testing/selftests/ftrace/config              |    1 
 .../test.d/trigger/trigger-wprobe-syntax-errors.tc |   37 +++++++
 .../ftrace/test.d/trigger/trigger-wprobe.tc        |  107 ++++++++++++++++++++
 3 files changed, 145 insertions(+)
 create mode 100644 tools/testing/selftests/ftrace/test.d/trigger/trigger-wprobe-syntax-errors.tc
 create mode 100644 tools/testing/selftests/ftrace/test.d/trigger/trigger-wprobe.tc

diff --git a/tools/testing/selftests/ftrace/config b/tools/testing/selftests/ftrace/config
index d2f503722020..ecdee77f360f 100644
--- a/tools/testing/selftests/ftrace/config
+++ b/tools/testing/selftests/ftrace/config
@@ -28,3 +28,4 @@ CONFIG_TRACER_SNAPSHOT=y
 CONFIG_UPROBES=y
 CONFIG_UPROBE_EVENTS=y
 CONFIG_WPROBE_EVENTS=y
+CONFIG_WPROBE_TRIGGERS=y
diff --git a/tools/testing/selftests/ftrace/test.d/trigger/trigger-wprobe-syntax-errors.tc b/tools/testing/selftests/ftrace/test.d/trigger/trigger-wprobe-syntax-errors.tc
new file mode 100644
index 000000000000..dd1ce4baa62b
--- /dev/null
+++ b/tools/testing/selftests/ftrace/test.d/trigger/trigger-wprobe-syntax-errors.tc
@@ -0,0 +1,37 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+# description: event trigger - test wprobe trigger syntax errors
+# requires: dynamic_events error_log "w[:[<group>/][<event>]] [r|w|rw]@<addr>[:<len>]":README "f[:[<group>/][<event>]] <func-name>[%return] [<args>]":README events/sched/sched_process_fork/trigger
+
+check_error() { # command-with-error-pos-by-^
+    ftrace_errlog_check "wprobe_trigger" "$1" "events/fprobes/testevent/trigger"
+}
+
+TARGET_FUNC=$(grep -m 1 -E -w "[tT] (vfs_read|do_sys_openat2|do_sys_open)" /proc/kallsyms | awk '{print $3}')
+if [ -z "$TARGET_FUNC" ]; then
+    echo "UNRESOLVED: target function not found"
+    exit_unresolved
+fi
+
+# Add a dummy fprobe event to attach triggers to
+echo "f:fprobes/testevent $TARGET_FUNC dfd=\$arg1" > dynamic_events
+
+# Add a target wprobe event
+echo 'w:watch rw@-1:8' >> dynamic_events
+
+# Test errors on trigger syntax
+check_error 'set_wprobe:^non_exist_wprobe:dfd'	# WPROBE_NOT_FOUND
+check_error 'set_wprobe:^'				# WPROBE_NOT_FOUND
+check_error 'set_wprobe:watch^'				# WPROBE_NEED_FIELD
+check_error 'set_wprobe:watch:^non_exist_field'	# NO_EVENT_FIELD
+
+# Enable target wprobe event and test WPROBE_BUSY error
+echo 1 > events/wprobes/watch/enable
+check_error 'set_wprobe:^watch:dfd'			# WPROBE_BUSY
+echo 0 > events/wprobes/watch/enable
+
+# Cleanup
+echo '-:watch' >> dynamic_events
+echo '-:testevent' >> dynamic_events
+
+exit 0
diff --git a/tools/testing/selftests/ftrace/test.d/trigger/trigger-wprobe.tc b/tools/testing/selftests/ftrace/test.d/trigger/trigger-wprobe.tc
new file mode 100644
index 000000000000..043e1c915ccf
--- /dev/null
+++ b/tools/testing/selftests/ftrace/test.d/trigger/trigger-wprobe.tc
@@ -0,0 +1,107 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+# description: event trigger - test wprobe trigger
+# requires: dynamic_events "w[:[<group>/][<event>]] [r|w|rw]@<addr>[:<len>]":README "f[:[<group>/][<event>]] <func-name>[%return] [<args>]":README events/sched/sched_process_fork/trigger "[(structname[,field])]<argname>[->field[->field|.field...]]":README
+
+fail() { #msg
+  echo "$1"
+  exit_fail
+}
+
+rmmod trace-events-sample ||:
+if ! modprobe trace-events-sample ; then
+  echo "No trace-events sample module - please make CONFIG_SAMPLE_TRACE_EVENTS=m"
+  exit_unresolved
+fi
+
+cleanup_wprobe_triggers() {
+  if [ -f events/fprobes/testevent/trigger ]; then
+    reset_trigger_file events/fprobes/testevent/trigger || true
+  fi
+  if [ -f events/sample-trace/foo_bar_with_fn/trigger ]; then
+    reset_trigger_file events/sample-trace/foo_bar_with_fn/trigger || true
+  fi
+  echo 0 > events/enable 2>/dev/null || true
+  echo > dynamic_events 2>/dev/null || true
+  sleep 1
+  rmmod trace-events-sample 2>/dev/null || true
+  return 0
+}
+
+trap cleanup_wprobe_triggers EXIT
+
+echo 0 > tracing_on
+
+# we will skip this test if fprobe is not supported.
+if ! grep -Fq "f[:[<group>/][<event>]] <func-name>[%return] [<args>]" README; then
+    echo "UNRESOLVED: fprobe is not supported"
+    exit_unresolved
+fi
+
+# we will skip this test if the target function does not exist.
+if ! grep -wq "sample_timer_cb" /proc/kallsyms; then
+    echo "UNRESOLVED: sample_timer_cb not found"
+    exit_unresolved
+fi
+
+:;: "Add a wprobe event used by trigger" ;:
+echo 'w:watch rw@-1:8 address=$addr value=$value' > dynamic_events
+
+:;: "Add events for triggering wprobe" ;:
+echo 'f:fprobes/testevent sample_timer_cb timer=t' >> dynamic_events
+
+:;: "Enable all events before setting triggers" ;:
+echo 1 > tracing_on
+echo 1 >> events/fprobes/testevent/enable
+echo 1 >> events/sample-trace/foo_bar_with_fn/enable
+
+:;: "Set set_wprobe trigger on testevent" ;:
+echo 'set_wprobe:watch:timer' >> events/fprobes/testevent/trigger
+if ! grep -q ^set_wprobe events/fprobes/testevent/trigger; then
+  fail "Failed to set set_wprobe trigger"
+fi
+
+# Wait for sample_timer_cb to fire and set_wprobe trigger to activate
+sleep 2
+
+:;: "Check set_wprobe trigger activated the watchpoint" ;:
+if ! grep -q watch trace; then
+  fail "Failed to trigger watchpoint"
+fi
+
+:;: "Set clear_wprobe trigger on foo_bar_with_fn" ;:
+echo 'clear_wprobe:watch' >> events/sample-trace/foo_bar_with_fn/trigger
+if ! grep -q ^clear_wprobe events/sample-trace/foo_bar_with_fn/trigger; then
+  fail "Failed to set clear_wprobe trigger"
+fi
+
+# Disable set_wprobe to prevent sample_timer_cb from re-arming the watchpoint
+echo '!set_wprobe:watch:timer' >> events/fprobes/testevent/trigger
+
+# Wait for foo_bar_with_fn to fire and clear_wprobe trigger to deactivate watchpoint
+sleep 2
+
+# Clear trace and wait to ensure no new watchpoint events are generated
+clear_trace
+sleep 1
+
+:;: "Ensure clear_wprobe trigger deactivated the watchpoint" ;:
+if grep -q watch trace; then
+  fail "Failed to clear watchpoint"
+fi
+
+:;: "Remove wprobe triggers" ;:
+echo '!clear_wprobe:watch' >> events/sample-trace/foo_bar_with_fn/trigger
+if grep -q ^set_wprobe events/fprobes/testevent/trigger; then
+  fail "Failed to remove set_wprobe trigger"
+fi
+if grep -q ^clear_wprobe events/sample-trace/foo_bar_with_fn/trigger; then
+  fail "Failed to remove clear_wprobe trigger"
+fi
+
+:;: "Disable events and remove dynamic events" ;:
+echo 0 > events/enable
+echo > dynamic_events
+clear_trace
+
+exit 0

[PATCH v15 11/12] tracing/wprobe: Support BTF typecast in fetchargs

[Masami Hiramatsu (Google)]

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

Allow BTF typecast syntax (STRUCT)FETCHARG->MEMBER in wprobe event
fetchargs. Previously, handle_typecast() rejected any probe context
that was not a function entry/return or tracepoint event probe.

Wprobe events use $addr (the accessed address) and $value (the value
at that address). By enabling BTF typecast, users can now cast these
to a concrete struct type and access its fields directly. For example:

  echo 'w:watch rw@-1:8 dflag=(dentry)$addr->d_flags' >> dynamic_events

With a set_wprobe trigger pointing the watchpoint at a dentry address,
the resulting trace shows d_flags being accessed at that location.

Note that $addr and $value are restricted to kernel-space memory,
which is consistent with the existing TPARG_FL_KERNEL flag used when
parsing wprobe fetchargs.

Assisted-by: Antigravity:gemini-3.8-flash
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
---
Changes in v15:
 - Document BTF typecast syntax for wprobe fetchargs in wprobetrace.rst.
 - Add explicit failure checks with fail helper in
   trigger-wprobe-btf-typecast.tc.
 - Declare fprobe README requirement in trigger-wprobe-btf-typecast.tc.
Changes in v14:
 - Update dummy wprobe event definition to use '-1' instead of '0'.
Changes in v11:
 - Update trigger-wprobe-btf-typecast.tc to use trace-events-sample
   kernel module.
 - Fix commit comment.
Changes in v9:
 - Newly added.
---
 Documentation/trace/wprobetrace.rst                |    8 ++
 kernel/trace/trace_probe.c                         |   13 +++
 kernel/trace/trace_probe.h                         |    5 +
 tools/testing/selftests/ftrace/config              |    1 
 .../test.d/trigger/trigger-wprobe-btf-typecast.tc  |   85 ++++++++++++++++++++
 5 files changed, 111 insertions(+), 1 deletion(-)
 create mode 100644 tools/testing/selftests/ftrace/test.d/trigger/trigger-wprobe-btf-typecast.tc

diff --git a/Documentation/trace/wprobetrace.rst b/Documentation/trace/wprobetrace.rst
index df8985283312..20a11443c6db 100644
--- a/Documentation/trace/wprobetrace.rst
+++ b/Documentation/trace/wprobetrace.rst
@@ -47,6 +47,14 @@ Synopsis of wprobe-events
                   (u8/u16/u32/u64/s8/s16/s32/s64), hexadecimal types
                   (x8/x16/x32/x64), "char", "string", "ustring", "symbol", "symstr"
                   and bitfield are supported.
+   (STRUCT[,ASGN])FETCHARG->MEMBER[->MEMBER] : If BTF is supported, typecast
+                  FETCHARG to a pointer to STRUCT and then dereference the
+                  pointer defined by ->MEMBER. ASGN can be specified optionally.
+                  If ASGN is specified, FETCHARG will be cast to the same offset
+                  position as the ASGN member, rather than to the beginning of
+                  the STRUCT.
+   (STRUCT[,ASGN])(FETCHARG)->MEMBER[->MEMBER] : typecast can nest, so the above
+                  can also be used with another FETCHARG.
 
    (\*1) This is useful for fetching a field of data structures.
    (\*2) "u" means user-space dereference.
diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
index 77266e042418..ccf489635ad7 100644
--- a/kernel/trace/trace_probe.c
+++ b/kernel/trace/trace_probe.c
@@ -890,6 +890,16 @@ static int query_btf_struct(const char *sname, struct traceprobe_parse_context *
 		ctx->struct_btf = NULL;
 	}
 
+	if (ctx->btf) {
+		id = btf_find_by_name_kind(ctx->btf, sname, BTF_KIND_STRUCT);
+		if (id > 0) {
+			btf_get(ctx->btf);
+			ctx->struct_btf = ctx->btf;
+			ctx->last_struct = btf_type_by_id(ctx->struct_btf, id);
+			return 0;
+		}
+	}
+
 	id = bpf_find_btf_id(sname, BTF_KIND_STRUCT, &btf);
 	if (id < 0)
 		return id;
@@ -965,7 +975,8 @@ static int handle_typecast(char *arg, struct traceprobe_parse_context *ctx)
 
 	if (!(tparg_is_event_probe(ctx->flags) ||
 	      tparg_is_function_entry(ctx->flags) ||
-	      tparg_is_function_return(ctx->flags))) {
+	      tparg_is_function_return(ctx->flags) ||
+	      tparg_is_wprobe(ctx->flags))) {
 		trace_probe_log_err(ctx->offset, NOSUP_BTFARG);
 		return -EOPNOTSUPP;
 	}
diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h
index 1e11077ead67..c54c554b1949 100644
--- a/kernel/trace/trace_probe.h
+++ b/kernel/trace/trace_probe.h
@@ -439,6 +439,11 @@ static inline bool tparg_is_event_probe(unsigned int flags)
 	return !!(flags & TPARG_FL_TEVENT);
 }
 
+static inline bool tparg_is_wprobe(unsigned int flags)
+{
+	return !!(flags & TPARG_FL_WPROBE);
+}
+
 /* Each typecast consumes nested level. So the max number of typecast is 8. */
 #define TRACEPROBE_MAX_NESTED_LEVEL 8
 
diff --git a/tools/testing/selftests/ftrace/config b/tools/testing/selftests/ftrace/config
index ecdee77f360f..f067874902ed 100644
--- a/tools/testing/selftests/ftrace/config
+++ b/tools/testing/selftests/ftrace/config
@@ -1,5 +1,6 @@
 CONFIG_BPF_SYSCALL=y
 CONFIG_DEBUG_INFO_BTF=y
+CONFIG_DEBUG_INFO_BTF_MODULES=y
 CONFIG_DEBUG_INFO_DWARF4=y
 CONFIG_EPROBE_EVENTS=y
 CONFIG_FPROBE=y
diff --git a/tools/testing/selftests/ftrace/test.d/trigger/trigger-wprobe-btf-typecast.tc b/tools/testing/selftests/ftrace/test.d/trigger/trigger-wprobe-btf-typecast.tc
new file mode 100644
index 000000000000..3d4c9fd6b8e2
--- /dev/null
+++ b/tools/testing/selftests/ftrace/test.d/trigger/trigger-wprobe-btf-typecast.tc
@@ -0,0 +1,85 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+# description: event trigger - test wprobe trigger with BTF typecast fetchargs
+# requires: dynamic_events "w[:[<group>/][<event>]] [r|w|rw]@<addr>[:<len>]":README "f[:[<group>/][<event>]] <func-name>[%return] [<args>]":README events/sched/sched_process_fork/trigger "[(structname[,field])]<argname>[->field[->field|.field...]]":README
+
+fail() { #msg
+  echo "$1"
+  exit_fail
+}
+
+rmmod trace-events-sample ||:
+if ! modprobe trace-events-sample ; then
+  echo "No trace-events sample module - please make CONFIG_SAMPLE_TRACE_EVENTS=m"
+  exit_unresolved
+fi
+
+cleanup_wprobe_triggers() {
+  if [ -f events/fprobes/testevent/trigger ]; then
+    reset_trigger_file events/fprobes/testevent/trigger || true
+  fi
+  echo 0 > events/enable 2>/dev/null || true
+  echo > dynamic_events 2>/dev/null || true
+  sleep 1
+  rmmod trace-events-sample 2>/dev/null || true
+  return 0
+}
+
+trap cleanup_wprobe_triggers EXIT
+
+echo 0 > tracing_on
+
+# we will skip this test if fprobe is not supported.
+if ! grep -Fq "f[:[<group>/][<event>]] <func-name>[%return] [<args>]" README; then
+    echo "UNRESOLVED: fprobe is not supported"
+    exit_unresolved
+fi
+
+# we will skip this test if the target function does not exist.
+if ! grep -wq "sample_timer_cb" /proc/kallsyms; then
+    echo "UNRESOLVED: sample_timer_cb not found"
+    exit_unresolved
+fi
+
+:;: "Add a wprobe event with BTF typecast fetchargs" ;:
+# (foo_timer_data,timer)$addr->counter reads counter from struct foo_timer_data via BTF typecast
+echo 'w:watch rw@-1:8 address=$addr counter=(foo_timer_data,timer)$addr->counter' >> dynamic_events
+
+:;: "Check the wprobe event is registered with counter field" ;:
+if ! grep -q "counter" dynamic_events; then
+  fail "Failed to register counter field in dynamic_events"
+fi
+
+:;: "Add fprobe event for sample_timer_cb" ;:
+echo 'f:fprobes/testevent sample_timer_cb timer=t' >> dynamic_events
+
+:;: "Enable all events before setting triggers" ;:
+echo 1 > tracing_on
+echo 1 >> events/fprobes/testevent/enable
+
+:;: "Set set_wprobe trigger on testevent" ;:
+echo 'set_wprobe:watch:timer' >> events/fprobes/testevent/trigger
+if ! grep -q ^set_wprobe events/fprobes/testevent/trigger; then
+  fail "Failed to set set_wprobe trigger"
+fi
+
+# Wait for sample_timer_cb to fire and set_wprobe trigger to activate
+sleep 3
+
+:;: "Check set_wprobe trigger activated the watchpoint" ;:
+if ! grep -q watch trace; then
+  fail "Failed to trigger watchpoint"
+fi
+
+:;: "Remove wprobe triggers" ;:
+echo '!set_wprobe:watch:timer' >> events/fprobes/testevent/trigger
+if grep -q ^set_wprobe events/fprobes/testevent/trigger; then
+  fail "Failed to remove set_wprobe trigger"
+fi
+
+:;: "Disable events and remove dynamic events" ;:
+echo 0 > events/enable
+echo > dynamic_events
+clear_trace
+
+exit 0

[PATCH v15 12/12] tracing/wprobe: Support BTF struct offset resolution in set_wprobe trigger

[Masami Hiramatsu (Google)]

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

Allow set_wprobe trigger to use BTF struct offset resolution to specify
the target address field.

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

Assisted-by: Antigravity:gemini-3.8-flash
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
---
Changes in v15:
 - Duplicate field string to avoid modifying glob in place in
   wprobe_trigger_typecast_parse() so tracing_log_err() prints pristine
   command string.
 - Remove leftover offset and adjust debug print in wprobe_trigger_print().
 - Document BTF struct offset resolution syntax in wprobetrace.rst.
 - Add explicit failure checks with fail helper in
   trigger-wprobe-btf-offset.tc.
 - Declare fprobe README requirement in trigger-wprobe-btf-offset.tc.
Changes in v14:
 - Update dummy wprobe event definition to use '-1' instead of '0'.
 - Pass member_type to btf_find_struct_member() and check its kflag in
   get_offset_of_field().
Changes in v13:
 - Check for field token before calling wprobe_trigger_field_parse() in
   clear_wprobe to avoid spurious error log entries on numeric counts.
Changes in v12:
 - Refactor field parsing logic into wprobe_trigger_field_parse().
 - Remove unused variable count_str in wprobe_trigger_cmd_parse().
---
 Documentation/trace/wprobetrace.rst                |    7 
 kernel/trace/trace_wprobe.c                        |  294 +++++++++++++++-----
 .../test.d/trigger/trigger-wprobe-btf-offset.tc    |   85 ++++++
 3 files changed, 308 insertions(+), 78 deletions(-)
 create mode 100644 tools/testing/selftests/ftrace/test.d/trigger/trigger-wprobe-btf-offset.tc

diff --git a/Documentation/trace/wprobetrace.rst b/Documentation/trace/wprobetrace.rst
index 20a11443c6db..1d9b32d02d53 100644
--- a/Documentation/trace/wprobetrace.rst
+++ b/Documentation/trace/wprobetrace.rst
@@ -90,10 +90,17 @@ Combination with trigger action
 The event trigger action can extend the utilization of this wprobe.
 
 - set_wprobe:WPEVENT:FIELD[+|-ADJUST][:COUNT]
+- set_wprobe:WPEVENT:(STRUCT[,ASGN])EVENT_FIELD->MEMBER[+|-ADJUST][:COUNT]
 - clear_wprobe:WPEVENT[:FIELD[+|-ADJUST][:COUNT]]
+- clear_wprobe:WPEVENT[:(STRUCT[,ASGN])EVENT_FIELD->MEMBER[+|-ADJUST][:COUNT]]
 
 Set these triggers to the target event, then the WPROBE event will be
 setup to trace the memory access at FIELD[+|-ADJUST] address.
+If BTF is supported, the target address can also be resolved using BTF
+struct offset resolution: `(STRUCT[,ASGN])EVENT_FIELD->MEMBER[+|-ADJUST]`.
+Here, EVENT_FIELD is an event field containing a pointer to STRUCT (or to
+the ASGN member if ASGN is specified), and MEMBER is the struct member whose
+offset is resolved automatically via BTF.
 When clear_wprobe is hit, if FIELD is NOT specified, the WPEVENT is
 forcibly cleared. If FIELD[+|-ADJUST] is set, it clears WPEVENT only
 if its watching address is the same as the FIELD[+|-ADJUST] value.
diff --git a/kernel/trace/trace_wprobe.c b/kernel/trace/trace_wprobe.c
index 3cf8786ef0ee..373cfd1640dd 100644
--- a/kernel/trace/trace_wprobe.c
+++ b/kernel/trace/trace_wprobe.c
@@ -27,6 +27,7 @@
 #include <asm/ptrace.h>
 
 #include "trace.h"
+#include "trace_btf.h"
 #include "trace_dynevent.h"
 #include "trace_probe.h"
 #include "trace_probe_kernel.h"
@@ -1028,6 +1029,213 @@ static void wprobe_trigger_free(struct event_trigger_data *data)
 	}
 }
 
+#ifdef CONFIG_PROBE_EVENTS_BTF_ARGS
+
+static int get_offset_of_field(struct btf *btf, const struct btf_type *type, char *field_name)
+{
+	const struct btf_member *field;
+	const struct btf_type *mtype;
+	int bitoffs = 0;
+	u32 anon_offs;
+	char *next;
+
+	do {
+		next = strchr(field_name, '.');
+		if (next)
+			*next++ = '\0';
+
+		field = btf_find_struct_member(btf, type, field_name, &anon_offs, &mtype);
+		if (IS_ERR_OR_NULL(field))
+			return -ENOENT;
+
+		if (btf_type_kflag(mtype)) {
+			/* Reject bitfield member access */
+			if (BTF_MEMBER_BITFIELD_SIZE(field->offset))
+				return -EINVAL;
+			bitoffs += anon_offs + BTF_MEMBER_BIT_OFFSET(field->offset);
+		} else {
+			bitoffs += anon_offs + field->offset;
+		}
+
+		field_name = next;
+		if (next) {
+			type = btf_type_skip_modifiers(btf, field->type, NULL);
+			if (!type)
+				return -ENOENT;
+		}
+	} while (next);
+	return bitoffs / BITS_PER_BYTE;
+}
+
+/* btf_put(NULL) is acceptable. */
+DEFINE_FREE(btf_put, struct btf *, btf_put(_T))
+
+/* parse typecast: (TYPE[,ASGN])EVENT_FIELD->FIELD[.SUBFIELD...][+-OFFS] and set adjust. */
+static int wprobe_trigger_typecast_parse(char *field_str,
+					 struct trace_event_file *file,
+					 struct wprobe_trigger_data *wprobe_data,
+					 const char *glob)
+{
+	struct btf *btf __free(btf_put) = NULL;
+	char *buf __free(kfree) = NULL;
+	struct ftrace_event_field *field;
+	const struct btf_type *type;
+	char *assign_field;
+	char *event_field;
+	char *type_field;
+	char *type_name;
+	char *offs;
+	long val = 0;
+	int base_offset = field_str - glob;
+	int event_field_offset;
+	int id, adjust;
+
+	buf = kstrdup(field_str, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	type_name = buf + 1;
+	event_field = strchr(type_name, ')');
+	if (!event_field) {
+		wprobe_trigger_log_err(file, glob,
+				       base_offset + (type_name - buf),
+				       DEREF_OPEN_BRACE);
+		return -EINVAL;
+	}
+	*event_field++ = '\0';
+
+	/* Check the optional assign field. */
+	assign_field = strchr(type_name, ',');
+	if (assign_field)
+		*assign_field++ = '\0';
+
+	/* Get the type field name. */
+	type_field = strstr(event_field, "->");
+	if (!type_field) {
+		wprobe_trigger_log_err(file, glob,
+				       base_offset + (event_field - buf),
+				       TYPECAST_REQ_FIELD);
+		return -EINVAL;
+	}
+	*type_field = '\0';
+	type_field += 2;
+
+	offs = strpbrk(type_field, "+-");
+	if (offs) {
+		if (kstrtol(offs, 0, &val) < 0) {
+			wprobe_trigger_log_err(file, glob,
+					       base_offset + (offs - buf),
+					       BAD_DEREF_OFFS);
+			return -EINVAL;
+		}
+		*offs = '\0';
+	}
+
+	/* find type from BTF */
+	id = bpf_find_btf_id(type_name, BTF_KIND_STRUCT, &btf);
+	if (id < 0) {
+		wprobe_trigger_log_err(file, glob,
+				       base_offset + (type_name - buf),
+				       BAD_BTF_TID);
+		return id;
+	}
+
+	type = btf_type_by_id(btf, id);
+	if (!type) {
+		wprobe_trigger_log_err(file, glob,
+				       base_offset + (type_name - buf),
+				       BAD_BTF_TID);
+		return -EINVAL;
+	}
+
+	adjust = get_offset_of_field(btf, type, type_field);
+	if (adjust < 0) {
+		wprobe_trigger_log_err(file, glob,
+				       base_offset + (type_field - buf),
+				       NO_BTF_FIELD);
+		return adjust;
+	}
+	wprobe_data->adjust = adjust + val;
+
+	if (assign_field) {
+		/* assign_field should be a struct field */
+		adjust = get_offset_of_field(btf, type, assign_field);
+		if (adjust < 0) {
+			wprobe_trigger_log_err(file, glob,
+					       base_offset + (assign_field - buf),
+					       NO_BTF_FIELD);
+			return adjust;
+		}
+		wprobe_data->adjust -= adjust;
+	}
+
+	event_field_offset = base_offset + (event_field - buf);
+	field = trace_find_event_field(file->event_call, event_field);
+	if (!field) {
+		wprobe_trigger_log_err(file, glob, event_field_offset, NO_EVENT_FIELD);
+		return -ENOENT;
+	}
+	if (field->size != sizeof(void *)) {
+		wprobe_trigger_log_err(file, glob, event_field_offset, WPROBE_BAD_FIELD);
+		return -ENOEXEC;
+	}
+	wprobe_data->offset = field->offset;
+	wprobe_data->field = kstrdup(event_field, GFP_KERNEL);
+	if (!wprobe_data->field)
+		return -ENOMEM;
+
+	return 0;
+}
+#else
+static int wprobe_trigger_typecast_parse(char *field_str,
+					 struct trace_event_file *file,
+					 struct wprobe_trigger_data *wprobe_data,
+					 const char *glob)
+{
+	wprobe_trigger_log_err(file, glob, field_str - glob, NOSUP_BTFARG);
+	return -EOPNOTSUPP;
+}
+#endif /* CONFIG_PROBE_EVENTS_BTF_ARGS */
+
+static int wprobe_trigger_field_parse(char *field_str, struct trace_event_file *file,
+					struct wprobe_trigger_data *wprobe_data,
+					const char *glob)
+{
+	struct ftrace_event_field *field;
+	char *offs;
+
+	if (field_str[0] == '(')
+		return wprobe_trigger_typecast_parse(field_str, file, wprobe_data, glob);
+
+	offs = strpbrk(field_str, "+-");
+	if (offs) {
+		long val;
+
+		if (kstrtol(offs, 0, &val) < 0) {
+			wprobe_trigger_log_err(file, glob, offs - glob, BAD_DEREF_OFFS);
+			return -EINVAL;
+		}
+		wprobe_data->adjust = val;
+		*offs = '\0';
+	}
+
+	field = trace_find_event_field(file->event_call, field_str);
+	if (!field) {
+		wprobe_trigger_log_err(file, glob, field_str - glob, NO_EVENT_FIELD);
+		return -ENOENT;
+	}
+	if (field->size != sizeof(void *)) {
+		wprobe_trigger_log_err(file, glob, field_str - glob, WPROBE_BAD_FIELD);
+		return -ENOEXEC;
+	}
+	wprobe_data->offset = field->offset;
+	wprobe_data->field = kstrdup(field_str, GFP_KERNEL);
+	if (!wprobe_data->field)
+		return -ENOMEM;
+
+	return 0;
+}
+
 static int wprobe_trigger_cmd_parse(struct event_command *cmd_ops,
 				    struct trace_event_file *file,
 				    char *glob, char *cmd,
@@ -1040,10 +1248,8 @@ static int wprobe_trigger_cmd_parse(struct event_command *cmd_ops,
 	struct wprobe_trigger_data *wprobe_data = NULL;
 	struct event_trigger_data *trigger_data = NULL;
 	struct trace_event_file *wprobe_file;
+	char *event_str, *comment;
 	struct trace_array *tr = file->tr;
-	char *event_str, *field_str, *comment;
-	struct ftrace_event_field *field;
-	struct trace_event_call *event;
 	bool remove, clear = false;
 	unsigned long orig_addr = 0;
 	struct trace_wprobe *tw;
@@ -1104,92 +1310,24 @@ static int wprobe_trigger_cmd_parse(struct event_command *cmd_ops,
 
 	/* clear_wprobe does not need field, but can have optional field. */
 	if (!clear) {
-		char *offs;
+		char *field_str = strsep(&param, ":");
 
-		/* Find target field, which must be equivalent to "void *" */
-		field_str = strsep(&param, ":");
 		if (!field_str) {
 			wprobe_trigger_log_err(file, glob, strlen(glob), WPROBE_NEED_FIELD);
 			ret = -EINVAL;
 			goto out_free;
 		}
-
-		offs = strpbrk(field_str, "+-");
-		if (offs) {
-			long val;
-
-			if (kstrtol(offs, 0, &val) < 0) {
-				wprobe_trigger_log_err(file, glob, offs - glob, BAD_DEREF_OFFS);
-				ret = -EINVAL;
-				goto out_free;
-			}
-			wprobe_data->adjust = val;
-			*offs = '\0';
-		}
-
-		event = file->event_call;
-		field = trace_find_event_field(event, field_str);
-		if (!field) {
-			wprobe_trigger_log_err(file, glob, field_str - glob, NO_EVENT_FIELD);
-			ret = -ENOENT;
-			goto out_free;
-		}
-
-		if (field->size != sizeof(void *)) {
-			wprobe_trigger_log_err(file, glob, field_str - glob, WPROBE_BAD_FIELD);
-			ret = -ENOEXEC;
-			goto out_free;
-		}
-		wprobe_data->offset = field->offset;
-		wprobe_data->field = kstrdup(field_str, GFP_KERNEL);
-		if (!wprobe_data->field) {
-			ret = -ENOMEM;
+		ret = wprobe_trigger_field_parse(field_str, file, wprobe_data, glob);
+		if (ret < 0)
 			goto out_free;
-		}
-	} else if (param && (isalpha(param[0]) || param[0] == '_')) {
+	} else if (param && (isalpha(param[0]) || param[0] == '_' || param[0] == '(')) {
 		if (strncmp(param, "count=", 6) != 0 &&
 		    strncmp(param, "unlimited", 9) != 0) {
-			char *offs;
-
-			field_str = strsep(&param, ":");
-			offs = strpbrk(field_str, "+-");
-			if (offs) {
-				long val;
-
-				if (kstrtol(offs, 0, &val) < 0) {
-					wprobe_trigger_log_err(file, glob,
-							       offs - glob,
-							       BAD_DEREF_OFFS);
-					ret = -EINVAL;
-					goto out_free;
-				}
-				wprobe_data->adjust = val;
-				*offs = '\0';
-			}
-
-			event = file->event_call;
-			field = trace_find_event_field(event, field_str);
-			if (!field) {
-				wprobe_trigger_log_err(file, glob,
-						       field_str - glob,
-						       NO_EVENT_FIELD);
-				ret = -ENOENT;
-				goto out_free;
-			}
+			char *field_str = strsep(&param, ":");
 
-			if (field->size != sizeof(void *)) {
-				wprobe_trigger_log_err(file, glob,
-						       field_str - glob,
-						       WPROBE_BAD_FIELD);
-				ret = -ENOEXEC;
+			ret = wprobe_trigger_field_parse(field_str, file, wprobe_data, glob);
+			if (ret < 0)
 				goto out_free;
-			}
-			wprobe_data->offset = field->offset;
-			wprobe_data->field = kstrdup(field_str, GFP_KERNEL);
-			if (!wprobe_data->field) {
-				ret = -ENOMEM;
-				goto out_free;
-			}
 		}
 	}
 
diff --git a/tools/testing/selftests/ftrace/test.d/trigger/trigger-wprobe-btf-offset.tc b/tools/testing/selftests/ftrace/test.d/trigger/trigger-wprobe-btf-offset.tc
new file mode 100644
index 000000000000..8bc8ca02a712
--- /dev/null
+++ b/tools/testing/selftests/ftrace/test.d/trigger/trigger-wprobe-btf-offset.tc
@@ -0,0 +1,85 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+# description: event trigger - test set_wprobe trigger with BTF struct offset
+# requires: dynamic_events "w[:[<group>/][<event>]] [r|w|rw]@<addr>[:<len>]":README "f[:[<group>/][<event>]] <func-name>[%return] [<args>]":README events/sched/sched_process_fork/trigger "[(structname[,field])]<argname>[->field[->field|.field...]]":README
+
+fail() { #msg
+  echo "$1"
+  exit_fail
+}
+
+rmmod trace-events-sample ||:
+if ! modprobe trace-events-sample ; then
+  echo "No trace-events sample module - please make CONFIG_SAMPLE_TRACE_EVENTS=m"
+  exit_unresolved
+fi
+
+cleanup_wprobe_triggers() {
+  if [ -f events/fprobes/testevent/trigger ]; then
+    reset_trigger_file events/fprobes/testevent/trigger || true
+  fi
+  echo 0 > events/enable 2>/dev/null || true
+  echo > dynamic_events 2>/dev/null || true
+  sleep 1
+  rmmod trace-events-sample 2>/dev/null || true
+  return 0
+}
+
+trap cleanup_wprobe_triggers EXIT
+
+echo 0 > tracing_on
+
+# we will skip this test if fprobe is not supported.
+if ! grep -Fq "f[:[<group>/][<event>]] <func-name>[%return] [<args>]" README; then
+    echo "UNRESOLVED: fprobe is not supported"
+    exit_unresolved
+fi
+
+# we will skip this test if the target function does not exist.
+if ! grep -wq "sample_timer_cb" /proc/kallsyms; then
+    echo "UNRESOLVED: sample_timer_cb not found"
+    exit_unresolved
+fi
+
+:;: "Add a wprobe event watching 8 bytes" ;:
+echo 'w:watch rw@-1:8 address=$addr value=$value' >> dynamic_events
+
+:;: "Add fprobe event for sample_timer_cb" ;:
+# sample_timer_cb(struct timer_list *t)
+# container_of(t, struct foo_timer_data, timer)
+echo 'f:fprobes/testevent sample_timer_cb timer=t' >> dynamic_events
+
+:;: "Enable all events before setting triggers" ;:
+echo 1 > tracing_on
+echo 1 >> events/fprobes/testevent/enable
+
+:;: "Set set_wprobe trigger using BTF struct offset resolution" ;:
+# Syntax: set_wprobe:WPEVENT:(STRUCT,FIELD)EVENT_FIELD->MEMBER
+# (foo_timer_data,timer) is the BTF struct type and field name
+# timer->expires is the struct member whose offset is resolved automatically via BTF
+echo 'set_wprobe:watch:(foo_timer_data,timer)timer->timer.expires' >> events/fprobes/testevent/trigger
+if ! grep -q ^set_wprobe events/fprobes/testevent/trigger; then
+  fail "Failed to set set_wprobe trigger"
+fi
+
+# Wait for sample_timer_cb to fire and set_wprobe trigger to activate
+sleep 3
+
+:;: "Check set_wprobe trigger activated the watchpoint" ;:
+if ! grep -q watch trace; then
+  fail "Failed to trigger watchpoint"
+fi
+
+:;: "Remove wprobe triggers" ;:
+# Since we don't know actual offset of timer->expires in foo_timer_data, we use reset_trigger_file
+reset_trigger_file events/fprobes/testevent/trigger
+if grep -q ^set_wprobe events/fprobes/testevent/trigger; then
+  fail "Failed to remove set_wprobe trigger"
+fi
+
+:;: "Disable events and remove dynamic events" ;:
+echo 0 > events/enable
+echo > dynamic_events
+clear_trace
+
+exit 0

Re: [PATCH v15 06/12] x86: hw_breakpoint: Add a kconfig to clarify when a breakpoint fires

[sashiko-bot]

> From: Masami Hiramatsu (Google) <mhiramat@kernel.org>
> 
> Add CONFIG_HAVE_POST_BREAKPOINT_HOOK which indicates the hw_breakpoint
> on that architecture fires after the target memory has been modified.
> This is currently x86 only behavior.
> 
> Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>

Sashiko has reviewed this patch and found no issues. It looks great!

-- 
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Re: [PATCH v15 07/12] selftests: tracing: Add a basic testcase for wprobe

[sashiko-bot]

> From: Masami Hiramatsu (Google) <mhiramat@kernel.org>
> 
> Add 'add_remove_wprobe.tc' testcase for testing wprobe event that
> tests adding and removing operations of the wprobe event.
> 
> Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>

Sashiko has reviewed this patch and found no issues. It looks great!

-- 
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Re: [PATCH v15 01/12] x86/mce: Fix hardware debug register corruption on task migration

[sashiko-bot]

> From: Masami Hiramatsu (Google) <mhiramat@kernel.org>
> 
> In exc_machine_check_user(), local_db_save() and local_db_restore() are
> invoked in the outer entry stubs (DEFINE_IDTENTRY_MCE_USER,
> DEFINE_FREDENTRY_MCE, and DEFINE_IDTENTRY_RAW), surrounding
> exc_machine_check_user().
> 
> However, exc_machine_check_user() calls irqentry_exit_to_user_mode(),
> which handles pending thread work and may schedule() if TIF_NEED_RESCHED
> is set. If the task migrates to another CPU during schedule(),
> local_db_restore() runs on the new CPU with the dr7 state saved from the
> old CPU. This corrupts the new CPU's DR7 hardware debug register and
> leaves the old CPU's DR7 disabled.
> In short, local_db_save() and local_db_restore() pair must be run
> on the same CPU.
> 
> To fix this, move local_db_save() and local_db_restore() inside
> exc_machine_check_user() and exc_machine_check_kernel(). In
> exc_machine_check_user(), DR7 is saved and restored strictly around
> do_machine_check() to avoid schedule() during migration. In
> exc_machine_check_kernel(), local_db_save() is called at the entry point
> to prevent early memory accesses from triggering nested #DB exceptions,
> and restored on all exits.
> 
> Fixes: cd840e424f27 ("x86/entry, mce: Disallow #DB during #MC")
> Assisted-by: Antigravity:gemini-3.8-flash
> Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>

Sashiko has reviewed this patch and found no issues. It looks great!

-- 
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Re: [PATCH v15 08/12] selftests: tracing: Add syntax testcase for wprobe

[sashiko-bot]

> From: Masami Hiramatsu (Google) <mhiramat@kernel.org>
> 
> Add "wprobe_syntax_errors.tc" testcase for testing syntax errors
> of the watch probe events.
> 
> Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>

Sashiko has reviewed this patch and found no issues. It looks great!

-- 
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Re: [PATCH v15 10/12] selftests: tracing: Add wprobe trigger testcase

[sashiko-bot]

> From: Masami Hiramatsu (Google) <mhiramat@kernel.org>
> 
> Add a testcase for checking wprobe trigger. This sets set_wprobe and
> clear_wprobe triggers on fprobe event and static trace event to
> monitor memory accesses within the trace-events-sample kernel module.
> Also add a testcase for verifying wprobe trigger syntax error logging.
> 
> Link: https://lore.kernel.org/all/59637b96946653393a7ad3c7de094094796b39c2.1785067572.git.wangjinchao600@gmail.com/
> 
> Assisted-by: Antigravity:gemini-3.8-flash
> Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>

Sashiko has reviewed this patch and found no issues. It looks great!

-- 
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Re: [PATCH v15 02/12] x86/hw_breakpoints: Make DR7 updates NMI safe

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 3 potential issue(s) to consider:

New issues:
- [High] local_db_restore() incorrectly uses dr7 == 0 to discard NMI-installed hardware breakpoints, permanently losing debug state and corrupting KVM guest debug registers.
- [High] local_db_save() destructively clears hardware DR7 inside its sequence retry loop, permanently corrupting the restored state if a retry occurs.

Pre-existing issues:
- [High] The early return in local_db_save() bypasses the sequence retry loop, leaving a race window where an NMI can leave hardware breakpoints enabled during critical exception handlers.
--

commit 48808d0a31b45134e9ef897c90c0f96bd987d9ce
Author: Jinchao Wang <wangjinchao600@gmail.com>

x86/hw_breakpoints: Make DR7 updates NMI safe

This commit introduces atomic per-CPU operations and sequence numbers to
make DR7 hardware breakpoint updates NMI safe. It updates local_db_save()
and local_db_restore() to use retry loops that detect NMI interruptions,
preventing state corruption.

Link: https://lore.kernel.org/all/4ee0a2efc9e8387af83286b8495b7d490247e165.1785067572.git.wangjinchao600@gmail.com/

> diff --git a/arch/x86/include/asm/debugreg.h b/arch/x86/include/asm/debugreg.h
> index 854d82b88ff4e..3399e166d3044 100644
> --- a/arch/x86/include/asm/debugreg.h
> +++ b/arch/x86/include/asm/debugreg.h
[ ... ]
> @@ -125,40 +126,66 @@ static __always_inline bool hw_breakpoint_active(void)
>  
>  extern void hw_breakpoint_restore(void);
>  
> -static __always_inline unsigned long local_db_save(void)
> +static __always_inline void local_db_save(unsigned long *dr7,
> +					  unsigned int *dr7_seq)
>  {
> -	unsigned long dr7;
> +	do {
> +		*dr7_seq = this_cpu_read(cpu_dr7_seq);
> +		*dr7 = 0;
>  
> -	if (cpu_feature_enabled(X86_FEATURE_HYPERVISOR) && !hw_breakpoint_active())
> -		return 0;
> -
> -	get_debugreg(dr7, 7);
> +		if (cpu_feature_enabled(X86_FEATURE_HYPERVISOR) &&
> +		    !hw_breakpoint_active())
> +			return;

[Severity: High]
This isn't a bug introduced by this patch, but could this early return
in local_db_save() bypass the sequence retry loop?

If an NMI hits exactly before the return instruction and installs a
breakpoint, the function exits immediately. This leaves the newly installed
hardware breakpoint active during exception handlers like MCE, which could
trigger a recursive #DB exception and lead to a kernel panic.

>  
> +		get_debugreg(*dr7, 7);
>  
> -	/* Architecturally set bit */
> -	dr7 &= ~DR7_FIXED_1;
> -	if (dr7)
> -		set_debugreg(DR7_FIXED_1, 7);
> +		/* Architecturally set bit */
> +		*dr7 &= ~DR7_FIXED_1;
> +		if (*dr7)
> +			set_debugreg(DR7_FIXED_1, 7);

[Severity: High]
Can this destructively overwrite the hardware DR7 state inside the sequence
retry loop?

If an NMI interrupts execution between reading and clearing DR7, installs a
breakpoint, and increments cpu_dr7_seq, this set_debugreg() call will
overwrite the NMI's new hardware state with 0x400.

When the loop detects the sequence mismatch and retries, the next
iteration's get_debugreg() will read this clobbered 0x400 value instead of
the state installed by the NMI, permanently corrupting the restored state.

>  
> -	/*
> -	 * Ensure the compiler doesn't lower the above statements into
> -	 * the critical section; disabling breakpoints late would not
> -	 * be good.
> -	 */
> -	barrier();
> +		/*
> +		 * Ensure the compiler doesn't lower the above statements into
> +		 * the critical section; disabling breakpoints late would not
> +		 * be good.
> +		 */
> +		barrier();
> +	} while (unlikely(*dr7_seq != this_cpu_read(cpu_dr7_seq)));
>  }
[ ... ]
> -static __always_inline void local_db_restore(unsigned long dr7)
> +static __always_inline void local_db_restore(unsigned long dr7,
> +					     unsigned int dr7_seq)
>  {
> +	unsigned long val;
> +	unsigned int seq;
> +
>  	/*
>  	 * Ensure the compiler doesn't raise this statement into
>  	 * the critical section; enabling breakpoints early would
>  	 * not be good.
>  	 */
>  	barrier();
> -	if (dr7)
> -		set_debugreg(dr7, 7);
> +
> +	do {
> +		seq = this_cpu_read(cpu_dr7_seq);
> +		if (seq == dr7_seq) {
> +			if (!dr7)
> +				return;
> +			val = dr7;
> +		} else {
> +			/*
> +			 * If an NMI modified breakpoints while DR7 was saved as 0
> +			 * (e.g. KVM guest entry), arch_install_hw_breakpoint()
> +			 * clobbered hardware DR7. Restore val = 0 (DR7_FIXED_1)
> +			 * to clean up the NMI's write and preserve guest isolation.
> +			 * Otherwise, load the latest cpu_dr7 state.
> +			 */
> +			val = dr7 ? this_cpu_read(cpu_dr7) : 0;

[Severity: High]
Does this logic permanently discard the hardware breakpoint installed by an
NMI if dr7 was initially 0?

If dr7 was saved as 0, which happens when no host breakpoints were active,
and an NMI subsequently installs a breakpoint, this logic evaluates to 0
and ignores the new cpu_dr7 state.

It will then write 0x400 to hardware DR7, completely overriding the NMI
update. Furthermore, if an NMI interrupts a KVM guest, the guest's DR7
state is completely destroyed and replaced with 0x400.

> +		}
> +
> +		set_debugreg(val | DR7_FIXED_1, 7);
> +		barrier();
> +	} while (unlikely(seq != this_cpu_read(cpu_dr7_seq)));
>  }

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/178875277830.93794.14247844688761142429.stgit@devnote2?part=2

Re: [PATCH v15 03/12] x86/hw_breakpoints: Add arch_modify_local_hw_breakpoint_addr() API

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] Modifying a debug address register while the breakpoint is enabled in DR7 violates the Intel SDM. This can occur due to a race condition with an NMI because the `cpu_dr7` shadow state is not temporarily updated.
--

commit ca38cc4e9ed0533dfe16175c78dba60903420a8b
Author: Jinchao Wang <wangjinchao600@gmail.com>

x86/hw_breakpoints: Add arch_modify_local_hw_breakpoint_addr() API

Wprobe needs to move an active per-CPU watchpoint without releasing and
reserving its hardware slot.

Add arch_modify_local_hw_breakpoint_addr() as the architecture backend for
modify_local_hw_breakpoint_addr(). It validates the new address, finds the
installed local slot, and updates the hardware debug register and per-CPU
shadow register.

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

> diff --git a/arch/x86/kernel/hw_breakpoint.c b/arch/x86/kernel/hw_breakpoint.c
> index 312550be3ad2b..99f0926298a85 100644
> --- a/arch/x86/kernel/hw_breakpoint.c
> +++ b/arch/x86/kernel/hw_breakpoint.c
[ ... ]
> @@ -129,6 +129,62 @@ int arch_install_hw_breakpoint(struct perf_event *bp)
[ ... ]
> +	do {
> +		seq = this_cpu_inc_return(cpu_dr7_seq);
> +
> +		/* Disable breakpoint in DR7 before updating address register */
> +		dr7 = this_cpu_read(cpu_dr7);
> +		set_debugreg((dr7 & ~__encode_dr7(i, info->len, info->type)) | DR7_FIXED_1, 7);

[Severity: High]
Does arch_modify_local_hw_breakpoint_addr() need to clear the breakpoint in
the shadow cpu_dr7 state as well?

Since the breakpoint isn't cleared in the cpu_dr7 shadow state, could an NMI
that interrupts execution here inadvertently re-enable the breakpoint
prematurely?

If an NMI handler (such as kgdb or perf) modifies breakpoints, it increments
cpu_dr7_seq and invokes local_db_save() and local_db_restore(). When the NMI
completes, local_db_restore() detects the sequence mismatch and restores
hardware DR7 using the cpu_dr7 shadow cache. Because cpu_dr7 still has this
breakpoint enabled, the target breakpoint gets re-enabled in hardware DR7
before the execution below resumes.

> +		barrier();
> +
> +		this_cpu_write(cpu_debugreg[i], addr);
> +		barrier();
> +		set_debugreg(addr, i);

[Severity: High]
If an NMI prematurely restored DR7 as described above, won't this modify the
debug address register while the breakpoint is enabled in DR7?

Modifying a debug address register while its corresponding DR7 enable bit is
set violates the Intel SDM and causes spurious #DB exceptions.

While the sequence loop retry mechanism will catch the mismatch, it only does
so after this instruction has already executed, which is too late to prevent
the spurious exception.

> +		barrier();
> +
> +		/* Re-enable breakpoint in DR7 */
> +		set_debugreg(this_cpu_read(cpu_dr7) | DR7_FIXED_1, 7);
> +		barrier();
> +	} while (seq != this_cpu_read(cpu_dr7_seq));
> +
> +	return 0;
> +}

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/178875277830.93794.14247844688761142429.stgit@devnote2?part=3

Re: [PATCH v15 11/12] tracing/wprobe: Support BTF typecast in fetchargs

[sashiko-bot]

> From: Masami Hiramatsu (Google) <mhiramat@kernel.org>
> 
> Allow BTF typecast syntax (STRUCT)FETCHARG->MEMBER in wprobe event
> fetchargs. Previously, handle_typecast() rejected any probe context
> that was not a function entry/return or tracepoint event probe.
> 
> Wprobe events use $addr (the accessed address) and $value (the value
> at that address). By enabling BTF typecast, users can now cast these
> to a concrete struct type and access its fields directly. For example:
> 
>   echo 'w:watch rw@-1:8 dflag=(dentry)$addr->d_flags' >> dynamic_events
> 
> With a set_wprobe trigger pointing the watchpoint at a dentry address,
> the resulting trace shows d_flags being accessed at that location.
> 
> Note that $addr and $value are restricted to kernel-space memory,
> which is consistent with the existing TPARG_FL_KERNEL flag used when
> parsing wprobe fetchargs.
> 
> Assisted-by: Antigravity:gemini-3.8-flash
> Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>

Sashiko has reviewed this patch and found no issues. It looks great!

-- 
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Re: [PATCH v15 04/12] HWBP: Add modify_local_hw_breakpoint_addr() API

[sashiko-bot]

> From: Masami Hiramatsu (Google) <mhiramat@kernel.org>
> 
> Add modify_local_hw_breakpoint_addr() to update only the watched
> address of an installed hardware breakpoint on the local CPU without
> releasing and reserving its hardware slot. This is available when the
> architecture selects CONFIG_HAVE_MODIFY_LOCAL_HW_BREAKPOINT_ADDR.
> 
> The caller must provide an installed local event and a valid address,
> and update other CPUs separately.
> 
> Link: https://lore.kernel.org/all/f9c49dfa49bdc57ba8c0574bc9981c1e581acf92.1785067572.git.wangjinchao600@gmail.com/
> 
> Assisted-by: Antigravity:gemini-3.8-flash
> Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
> Signed-off-by: Jinchao Wang <wangjinchao600@gmail.com>

Sashiko has reviewed this patch and found no issues. It looks great!

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/178875277830.93794.14247844688761142429.stgit@devnote2?part=4

Re: [PATCH v15 12/12] tracing/wprobe: Support BTF struct offset resolution in set_wprobe trigger

[sashiko-bot]

> From: Masami Hiramatsu (Google) <mhiramat@kernel.org>
> 
> Allow set_wprobe trigger to use BTF struct offset resolution to specify
> the target address field.
> 
> Link: https://lore.kernel.org/all/59637b96946653393a7ad3c7de094094796b39c2.1785067572.git.wangjinchao600@gmail.com/
> 
> Assisted-by: Antigravity:gemini-3.8-flash
> Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>

Sashiko has reviewed this patch and found no issues. It looks great!

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/178875277830.93794.14247844688761142429.stgit@devnote2?part=12

Re: [PATCH v15 09/12] tracing/wprobe: Add set_wprobe and clear_wprobe event triggers

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] clear_wprobe incorrectly rejects legitimate fields starting with "unlimited"
--

commit f87f4797ae7a52cd2de4840afea59fb8bb8bbaf6
Author: Masami Hiramatsu (Google) <mhiramat@kernel.org>

tracing/wprobe: Add set_wprobe and clear_wprobe event triggers

This commit adds the set_wprobe and clear_wprobe event triggers to dynamically
attach and detach hardware breakpoint address monitoring based on event field
contents.

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

> diff --git a/kernel/trace/trace_wprobe.c b/kernel/trace/trace_wprobe.c
> --- a/kernel/trace/trace_wprobe.c
> +++ b/kernel/trace/trace_wprobe.c

[ ... ]

> +static int wprobe_trigger_cmd_parse(struct event_command *cmd_ops,
> +				    struct trace_event_file *file,
> +				    char *glob, char *cmd,
> +				    char *param_and_filter)
> +{

[ ... ]

> +	/* clear_wprobe does not need field, but can have optional field. */
> +	if (!clear) {

[ ... ]

> +	} else if (param && (isalpha(param[0]) || param[0] == '_')) {
> +		if (strncmp(param, "count=", 6) != 0 &&
> +		    strncmp(param, "unlimited", 9) != 0) {
[Severity: Medium]
Will this substring comparison mistakenly intercept legitimate C-identifier
field names that start with "unlimited"?

If a user passes a legitimate event field name like "unlimited_size" to
clear_wprobe, the strncmp(param, "unlimited", 9) != 0 check will evaluate
to false. The parsing logic in wprobe_trigger_cmd_parse() will mistakenly
assume it is a count parameter, skip the field parsing, and pass the string
to event_trigger_parse_num().

Since event_trigger_parse_num() attempts to parse "unlimited_size" using
kstrtoul(), it will fail and return -EINVAL. Could this prevent users from
using clear_wprobe on any valid field beginning with "unlimited"?

> +			char *offs;
> +
> +			field_str = strsep(&param, ":");
> +			offs = strpbrk(field_str, "+-");

[ ... ]

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/178875277830.93794.14247844688761142429.stgit@devnote2?part=9

Re: [PATCH v15 05/12] tracing/wprobe: Add wprobe (watchpoint probe) trace event support

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Low] The `readme_msg` in `trace.c` instructs users to write to `wprobe_events`, but this file is never created.
--

commit 5c44f59e0b2737617a0b5934e625357ecffcc63d
Author: Masami Hiramatsu (Google) <mhiramat@kernel.org>

tracing/wprobe: Add wprobe (watchpoint probe) trace event support

This commit introduces hardware-breakpoint-based dynamic trace event support
(wprobe). It creates dynamic events 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/

> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index a946e0183fd1e..40c3e1543f6e3 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"

[Severity: Low]
Does this advertise a non-existent interface file to the user?

The readme_msg instructs users to write to wprobe_events, but it appears
this file is never created by this patch.

> +#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"

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/178875277830.93794.14247844688761142429.stgit@devnote2?part=5

Re: [PATCH v15 00/12] tracing: wprobe: x86: Add wprobe for watchpoint

[Jinchao Wang]

On 9/7/2026 11:46 AM, Masami Hiramatsu (Google) wrote:
> Hi,
> 
> Here is the 15th version of the series for adding new wprobe (watch probe)
> which provides memory access tracing event. Moreover, this can be used
> via event trigger. Thus it can trace memory access on dynamically
> allocated objects too.
> The previous version is here:
> 
>   https://lore.kernel.org/all/178810001186.64882.2161016469449127450.stgit@devnote2/
> 
> In this version, previous bugfix patches for BTF kflag resolution and
> RCU-protected kprobe blacklist were sent to Linus via probe/fixes, reducing
> the series to 12 patches. This version addresses feedbacks from Sashiko on
> v14[1], and more local fixes such as x86 debug register manipulation, validates
> watched address and natural alignment, tracks missed events on SMP update
> failures(*), prevents in-place command string modification during trigger
> parsing, adds explicit failure checks in selftests, and documents BTF
> typecast and struct offset syntax. I also added Assited-by: tags for this
> update.
> 
> [1] https://sashiko.dev/#/patchset/178810001186.64882.2161016469449127450.stgit%40devnote2
> (*) currently it just increase a missed counter.
> 
> Detailed changes are here.
> 
> Changes in v15:
>  - x86/mce: Move local_db_save() to entry of exc_machine_check_kernel()
>    and restore it on early return from mce_check_crashing_cpu() to
>    prevent nested #DB on watched variables.
>  - x86/hw_breakpoints: Always preserve DR7_FIXED_1 in
>    arch_install_hw_breakpoint(), arch_uninstall_hw_breakpoint(), and
>    hw_breakpoint_restore() for architectural compliance.
>  - x86/hw_breakpoints: Wrap local_db_save() in a cpu_dr7_seq loop to
>    detect NMI breakpoint updates and ensure DR7 is disabled before entry.
>  - x86/hw_breakpoints: In local_db_restore(), restore DR7_FIXED_1 if
>    saved dr7 is 0 and an NMI updated breakpoints, preserving KVM guest
>    isolation.
>  - x86/hw_breakpoints: Always write "val | DR7_FIXED_1" to hardware DR7
>    in local_db_restore() for architectural compliance.
>  - x86/hw_breakpoints: Avoid modifying saved dr7 in-place across retry
>    loops.
>  - x86/hw_breakpoints: Temporarily clear breakpoint enable bit in DR7
>    before updating debug address register and re-enable it afterward to
>    comply with x86 specification and avoid spurious #DBs.
>  - HWBP: Annotate counter_arch_bp(bp)->address and bp->attr.bp_addr with
>    WRITE_ONCE() in both update and rollback paths to prevent data races
>    with concurrent readers (e.g. NMI handlers).
>  - tracing/wprobe: Introduce trace_wprobe_is_valid_addr() to validate
>    target address and natural alignment for wprobe length during event
>    creation and trigger setup.
>  - tracing/wprobe: Initialize irq_work and work immediately after
>    allocation in alloc_trace_wprobe() and check tw->work.func in
>    free_trace_wprobe() to prevent WARN_ON(!work->func) on early failures.
>  - tracing/wprobe: Record SMP local update failures in tw->missed counter
>    and expose missed event count as a trailing comment in trigger file.
>  - tracing/wprobe: Duplicate field string in wprobe_trigger_typecast_parse()
>    to avoid modifying glob in place so tracing_log_err() logs the pristine
>    command string.
>  - tracing/wprobe: Remove leftover offset and adjust debug print in
>    wprobe_trigger_print().
>  - tracing/wprobe: Add set_wprobe and clear_wprobe triggers to readme_msg
>    in trace.c.
>  - tracing/wprobe: Move variable declarations to function entry in
>    trace_wprobe_show(), fix tab indentation in trace.c, and wrap lines
>    exceeding 100 columns.
>  - Documentation: Document BTF typecast in fetchargs and BTF struct
>    offset resolution in set_wprobe trigger in wprobetrace.rst.
>  - selftests/ftrace: Add explicit failure checks with fail helper across
>    trigger-wprobe.tc, trigger-wprobe-btf-typecast.tc, and
>    trigger-wprobe-btf-offset.tc.
>  - selftests/ftrace: Declare fprobe README requirement in trigger tests
>    and trigger file check in trigger-wprobe-syntax-errors.tc requires line.
> 
> 
> Public branch
> -------------
> I will push this branch as topic/wprobe-v2 to my tree so that it
> can be easily tested.
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/mhiramat/linux.git/log/?h=topic/wprobe-v2
> 
> This is based on linux-trace tree's linux-trace/probes/fixes.
> 
> Usage
> -----
> 
> The basic usage of this wprobe is similar to other probes;
> 
>   w:[GRP/][EVENT] [r|w|rw]@<ADDRESS|SYMBOL[+|-OFFS]>[:LEN] [FETCHARGS]
> 
> This defines a new wprobe event. For example, to trace jiffies update,
> you can do;
> 
>  echo 'w:my_jiffies w@jiffies:8 value=+0($addr)' >> dynamic_events
>  echo 1 > events/wprobes/my_jiffies/enable
> 
> Moreover, this can be combined with event trigger to trace the memory
> access on slab objects. The trigger syntax is;
> 
>   set_wprobe:WPROBE_EVENT:FIELD[+|-OFFSET][:COUNT] [if FILTER]
>   clear_wprobe:WPROBE_EVENT[:FIELD[+|-OFFSET][:COUNT]] [if FILTER]
> 
> set_wprobe sets WPROBE_EVENT's watch address on FIELD[+|-OFFSET].
> clear_wprobe clears WPROBE_EVENT's watch address if it is set to
> FIELD[+|-OFFSET]. If FIELD is omitted, forcibly clear the watch address
> when trigger event is hit.
> 
> For example, trace the first 8 byte of the dentry data structure passed
> to do_truncate() until it is deleted by dentry_kill().
> (Note: all tracefs setup uses '>>' so that it does not kick do_truncate())
> 
>   # echo 'w:watch rw@-1:8 address=$addr value=+0($addr)' > dynamic_events
> 
>   # echo 'f:truncate do_truncate dentry=$arg2' >> dynamic_events
>   # echo 'set_wprobe:watch:dentry' >> events/fprobes/truncate/trigger
> 
>   # echo 'f:dentry_kill dentry_kill dentry=$arg1' >> dynamic_events
>   # echo 'clear_wprobe:watch:dentry' >> events/fprobes/dentry_kill/trigger
> 
>   # echo 1 >> events/fprobes/truncate/enable
>   # echo 1 >> events/fprobes/dentry_kill/enable
> 
>   # echo aaa > /tmp/hoge
>   # echo bbb > /tmp/hoge
>   # echo ccc > /tmp/hoge
>   # rm /tmp/hoge
> 
> Then, the trace data will show;
> 
>  # tracer: nop
>  #
>  # entries-in-buffer/entries-written: 32/32   #P:8
>  #
>  #                                _-----=> irqs-off/BH-disabled
>  #                               / _----=> need-resched
>  #                              | / _---=> hardirq/softirq
>  #                              || / _--=> preempt-depth
>  #                              ||| / _-=> migrate-disable
>  #                              |||| /     delay
>  #           TASK-PID     CPU#  |||||  TIMESTAMP  FUNCTION
>  #              | |         |   |||||     |         |
>                sh-107     [004] ...1.     9.990418: dentry_kill: (dentry_kill+0x0/0x2c0) dentry=0xffff888004ad6618
>                sh-107     [004] ...1.     9.990914: dentry_kill: (dentry_kill+0x0/0x2c0) dentry=0xffff888004b3de78
>                sh-107     [004] ...1.     9.993175: dentry_kill: (dentry_kill+0x0/0x2c0) dentry=0xffff8880049ddd40
>                sh-107     [004] .....     9.995198: truncate: (do_truncate+0x4/0x120) dentry=0xffff8880048083a8
>                sh-107     [004] ...1.     9.995389: dentry_kill: (dentry_kill+0x0/0x2c0) dentry=0xffff8880049db998
>                sh-107     [004] ..Zff     9.997503: watch: (lookup_fast+0xaa/0x150) address=0xffff8880048083a8 value=0x8200080
>                sh-107     [004] ..Zff     9.997509: watch: (path_openat+0x211/0xda0) address=0xffff8880048083a8 value=0x8200080
>                sh-107     [004] ..Zff     9.997514: watch: (path_openat+0xa56/0xda0) address=0xffff8880048083a8 value=0x8200080
>                sh-107     [004] ..Zff     9.997518: watch: (path_openat+0xae2/0xda0) address=0xffff8880048083a8 value=0x8200080
>                sh-107     [004] .....     9.997521: truncate: (do_truncate+0x4/0x120) dentry=0xffff8880048083a8
>                sh-107     [004] ...1.     9.997582: dentry_kill: (dentry_kill+0x0/0x2c0) dentry=0xffff888004808270
>                sh-107     [004] ...1.     9.999365: dentry_kill: (dentry_kill+0x0/0x2c0) dentry=0xffff8880049db728
>                sh-107     [004] ...1.     9.999388: dentry_kill: (dentry_kill+0x0/0x2c0) dentry=0xffff888004b1c000
>                rm-113     [005] ..Zff    10.000965: watch: (lookup_fast+0xaa/0x150) address=0xffff8880048083a8 value=0x8200080
>                rm-113     [005] ..Zff    10.000971: watch: (path_lookupat+0x97/0x1e0) address=0xffff8880048083a8 value=0x8200080
>                rm-113     [005] ..Zff    10.000984: watch: (lookup_fast+0xaa/0x150) address=0xffff8880048083a8 value=0x8200080
>                rm-113     [005] ..Zff    10.000988: watch: (path_lookupat+0x97/0x1e0) address=0xffff8880048083a8 value=0x8200080
>                rm-113     [005] ..Zff    10.001010: watch: (lookup_one_qstr_excl+0x28/0x140) address=0xffff8880048083a8 value=0x8200080
>                rm-113     [005] ..Zff    10.001014: watch: (lookup_one_qstr_excl+0xd1/0x140) address=0xffff8880048083a8 value=0x8200080
>                rm-113     [005] ..Zff    10.001018: watch: (may_delete_dentry+0x1c/0x200) address=0xffff8880048083a8 value=0x8200080
>                rm-113     [005] ..Zff    10.001021: watch: (may_delete_dentry+0x195/0x200) address=0xffff8880048083a8 value=0x8200080
>                rm-113     [005] ..Zff    10.001031: watch: (vfs_unlink+0x5e/0x260) address=0xffff8880048083a8 value=0x8200080
>                rm-113     [005] d.Z..    10.001067: watch: (d_make_discardable+0x1b/0x40) address=0xffff8880048083a8 value=0x8200080
>                rm-113     [005] d.Z..    10.001071: watch: (d_make_discardable+0x29/0x40) address=0xffff8880048083a8 value=0x200080
>                rm-113     [005] ...1.    10.001072: dentry_kill: (dentry_kill+0x0/0x2c0) dentry=0xffff8880048083a8
>                rm-113     [005] ...1.    10.001218: dentry_kill: (dentry_kill+0x0/0x2c0) dentry=0xffff8880048083a8
>                sh-107     [004] ...1.    10.001416: dentry_kill: (dentry_kill+0x0/0x2c0) dentry=0xffff8880049db110
>                sh-107     [004] ...1.    10.001444: dentry_kill: (dentry_kill+0x0/0x2c0) dentry=0xffff8880049db248
>                sh-107     [004] ...1.    10.001500: dentry_kill: (dentry_kill+0x0/0x2c0) dentry=0xffff888004ad6618
>                sh-107     [004] ...1.    10.002067: dentry_kill: (dentry_kill+0x0/0x2c0) dentry=0xffff888004b41e78
>                sh-107     [004] ...1.    10.904920: dentry_kill: (dentry_kill+0x0/0x2c0) dentry=0xffff888004b41e78
>                sh-107     [004] ...1.    10.905129: dentry_kill: (dentry_kill+0x0/0x2c0) dentry=0xffff888004ad6618
> 
> 
> Thank you,
> 
> ---
> base-commit: 0c4256196b3a105307e2235fbfd85e768bbcdd0f
> 
> Jinchao Wang (2):
>       x86/hw_breakpoints: Make DR7 updates NMI safe
>       x86/hw_breakpoints: Add arch_modify_local_hw_breakpoint_addr() API
> 
> Masami Hiramatsu (Google) (10):
>       x86/mce: Fix hardware debug register corruption on task migration
>       HWBP: Add modify_local_hw_breakpoint_addr() API
>       tracing/wprobe: Add wprobe (watchpoint probe) trace event support
>       x86: hw_breakpoint: Add a kconfig to clarify when a breakpoint fires
>       selftests: tracing: Add a basic testcase for wprobe
>       selftests: tracing: Add syntax testcase for wprobe
>       tracing/wprobe: Add set_wprobe and clear_wprobe event triggers
>       selftests: tracing: Add wprobe trigger testcase
>       tracing/wprobe: Support BTF typecast in fetchargs
>       tracing/wprobe: Support BTF struct offset resolution in set_wprobe trigger
> 
> 
>  Documentation/trace/index.rst                      |    1 
>  Documentation/trace/wprobetrace.rst                |  200 +++
>  arch/Kconfig                                       |   18 
>  arch/x86/Kconfig                                   |    2 
>  arch/x86/include/asm/debugreg.h                    |   67 +
>  arch/x86/include/asm/hw_breakpoint.h               |    2 
>  arch/x86/kernel/cpu/mce/core.c                     |   29 
>  arch/x86/kernel/hw_breakpoint.c                    |  151 +-
>  arch/x86/kernel/nmi.c                              |    7 
>  arch/x86/kernel/traps.c                            |   10 
>  include/linux/hw_breakpoint.h                      |    6 
>  include/linux/trace_events.h                       |    3 
>  kernel/events/hw_breakpoint.c                      |   48 +
>  kernel/trace/Kconfig                               |   24 
>  kernel/trace/Makefile                              |    1 
>  kernel/trace/trace.c                               |   13 
>  kernel/trace/trace.h                               |    6 
>  kernel/trace/trace_events_trigger.c                |    2 
>  kernel/trace/trace_probe.c                         |   36 
>  kernel/trace/trace_probe.h                         |   22 
>  kernel/trace/trace_wprobe.c                        | 1522 ++++++++++++++++++++
>  tools/testing/selftests/ftrace/config              |    3 
>  .../ftrace/test.d/dynevent/add_remove_wprobe.tc    |   63 +
>  .../test.d/dynevent/wprobes_syntax_errors.tc       |   23 
>  .../test.d/trigger/trigger-wprobe-btf-offset.tc    |   85 +
>  .../test.d/trigger/trigger-wprobe-btf-typecast.tc  |   85 +
>  .../test.d/trigger/trigger-wprobe-syntax-errors.tc |   37 
>  .../ftrace/test.d/trigger/trigger-wprobe.tc        |  107 +
>  28 files changed, 2476 insertions(+), 97 deletions(-)
>  create mode 100644 Documentation/trace/wprobetrace.rst
>  create mode 100644 kernel/trace/trace_wprobe.c
>  create mode 100644 tools/testing/selftests/ftrace/test.d/dynevent/add_remove_wprobe.tc
>  create mode 100644 tools/testing/selftests/ftrace/test.d/dynevent/wprobes_syntax_errors.tc
>  create mode 100644 tools/testing/selftests/ftrace/test.d/trigger/trigger-wprobe-btf-offset.tc
>  create mode 100644 tools/testing/selftests/ftrace/test.d/trigger/trigger-wprobe-btf-typecast.tc
>  create mode 100644 tools/testing/selftests/ftrace/test.d/trigger/trigger-wprobe-syntax-errors.tc
>  create mode 100644 tools/testing/selftests/ftrace/test.d/trigger/trigger-wprobe.tc
> 
> --
> Masami Hiramatsu (Google) <mhiramat@kernel.org>
Hi Masami,

I see the watch address update currently goes irq_work -> workqueue ->
on_each_cpu().  I would like to discuss that path.

The race window wprobe may be used to watch can be very narrow --
sometimes it lives entirely inside a single function -- and the trigger
does not always run in in_task() context.  The current path defers the
update to a work item, so by the time the debug registers are updated the
window may already be gone.

Now that we have modify_local_hw_breakpoint_addr(), the trigger could arm
the local CPU directly and use smp_call_function_single_async() for the
remote ones.  That should improve the overlap between the watch and the window.

What do you think?

Thanks,
Jinchao