From: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
To: Steven Rostedt <rostedt@goodmis.org>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>,
x86@kernel.org
Cc: Jinchao Wang <wangjinchao600@gmail.com>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Masami Hiramatsu <mhiramat@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
"H . Peter Anvin" <hpa@zytor.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Ian Rogers <irogers@google.com>,
linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org,
linux-doc@vger.kernel.org, linux-perf-users@vger.kernel.org
Subject: [PATCH v11 00/11] tracing: wprobe: x86: Add wprobe for watchpoint
Date: Sun, 2 Aug 2026 17:18:25 +0900 [thread overview]
Message-ID: <178565870538.714490.11309825813968306287.stgit@devnote2> (raw)
Hi,
Here is the 11th 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/178476134787.26117.10094977293012760490.stgit@devnote2/
The major changes in this version is to use Jinchao's new
modify_local_hw_breakpoint_addr() API, add count option support to
wprobe trigger, skip wprobe trigger during another wprobe trigger is
working and rewrite selftests for wprobe trigger with
trace-events-sample module.
Changes in v11:
- Updated hardware breakpoint modification API:
- Replaced arch_reinstall_hw_breakpoint() with
arch_modify_local_hw_breakpoint_addr() and
modify_local_hw_breakpoint_addr() API.
- Made DR7 updates NMI safe by using atomic cmpxchg for slot management
and per-CPU sequence number (cpu_dr7_seq) to detect concurrent NMI
updates.
- Refactored wprobe trigger implementation:
- Updated set_wprobe/clear_wprobe trigger to use
modify_local_hw_breakpoint_addr().
- Added tracepoint_synchronize_unregister() in wprobe_unregister_trigger()
and parse error path.
- Added NULL check for tw->bp_event in trace_wprobe_update_local() to
prevent race conditions.
- Switched trigger data freeing to use event_trigger_data::private_data_free.
- Added count option support (count=N) for wprobe triggers.
- Fixed trigger address calculation (cast rec to char *).
- Added work_pending flag to avoid update conflicts between CPUs.
- Fixed wprobe_trigger_find_same() to check wprobe_data->clear flag.
- Update trigger-wprobe*.tc to use trace-events-sample kernel module.
- Fixed selftest:
- Updated trigger-wprobe.tc assertion logic for clear_wprobe trigger
test to check trace log instead of sysfs enable file (which remains 1
under soft-disable).
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 probes/for-next.
Usage
-----
The basic usage of this wprobe is similar to other probes;
w:[GRP/][EVENT] [r|w|rw]@<ADDRESS|SYMBOL[+OFFS]> [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($addr)' >> dynamic_events
echo 1 > events/wprobes/my_jiffies/enable
Moreover, this can be combined with event trigger to trace the memory
access on slab objects. The trigger syntax is;
set_wprobe:WPROBE_EVENT:FIELD[+OFFSET] [if FILTER]
clear_wprobe:WPROBE_EVENT[:FIELD[+OFFSET]] [if FILTER]
set_wprobe sets WPROBE_EVENT's watch address on FIELD[+OFFSET].
clear_wprobe clears WPROBE_EVENT's watch address if it is set to
FIELD[+OFFSET]. If FIELD is omitted, forcibly clear the watch address
when trigger event is hit.
For example, trace the first 8 byte of the dentry data structure passed
to do_truncate() until it is deleted by dentry_kill().
(Note: all tracefs setup uses '>>' so that it does not kick do_truncate())
# echo 'w:watch rw@0:8 address=$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,
---
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) (9):
HWBP: Add modify_local_hw_breakpoint_addr() API
tracing: wprobe: Add watchpoint probe event based on hardware breakpoint
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 wprobe event trigger
selftests: ftrace: Add wprobe trigger testcase
tracing/wprobe: Support BTF typecast in fetchargs
tracing/wprobe: Support BTF typecast in wprobe trigger command
Documentation/trace/index.rst | 1
Documentation/trace/wprobetrace.rst | 163 ++
arch/Kconfig | 18
arch/x86/Kconfig | 2
arch/x86/include/asm/debugreg.h | 36 -
arch/x86/include/asm/hw_breakpoint.h | 2
arch/x86/kernel/cpu/mce/core.c | 20
arch/x86/kernel/hw_breakpoint.c | 125 +-
arch/x86/kernel/nmi.c | 10
arch/x86/kernel/traps.c | 10
include/linux/hw_breakpoint.h | 6
include/linux/trace_events.h | 3
kernel/events/hw_breakpoint.c | 35 +
kernel/trace/Kconfig | 24
kernel/trace/Makefile | 1
kernel/trace/trace.c | 9
kernel/trace/trace.h | 6
kernel/trace/trace_events_trigger.c | 2
kernel/trace/trace_probe.c | 34
kernel/trace/trace_probe.h | 15
kernel/trace/trace_wprobe.c | 1392 ++++++++++++++++++++
tools/testing/selftests/ftrace/config | 3
.../ftrace/test.d/dynevent/add_remove_wprobe.tc | 63 +
.../test.d/dynevent/wprobes_syntax_errors.tc | 21
.../test.d/trigger/trigger-wprobe-btf-offset.tc | 74 +
.../test.d/trigger/trigger-wprobe-btf-typecast.tc | 72 +
.../ftrace/test.d/trigger/trigger-wprobe.tc | 85 +
27 files changed, 2156 insertions(+), 76 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.tc
--
Masami Hiramatsu (Google) <mhiramat@kernel.org>
next reply other threads:[~2026-08-02 8:18 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-02 8:18 Masami Hiramatsu (Google) [this message]
2026-08-02 8:18 ` [PATCH v11 01/11] x86/hw_breakpoints: Make DR7 updates NMI safe Masami Hiramatsu (Google)
2026-08-02 8:18 ` [PATCH v11 02/11] x86/hw_breakpoints: Add arch_modify_local_hw_breakpoint_addr() API Masami Hiramatsu (Google)
2026-08-02 8:18 ` [PATCH v11 03/11] HWBP: Add modify_local_hw_breakpoint_addr() API Masami Hiramatsu (Google)
2026-08-02 8:19 ` [PATCH v11 04/11] tracing: wprobe: Add watchpoint probe event based on hardware breakpoint Masami Hiramatsu (Google)
2026-08-02 8:19 ` [PATCH v11 05/11] x86: hw_breakpoint: Add a kconfig to clarify when a breakpoint fires Masami Hiramatsu (Google)
2026-08-02 8:19 ` [PATCH v11 06/11] selftests: tracing: Add a basic testcase for wprobe Masami Hiramatsu (Google)
2026-08-02 8:19 ` [PATCH v11 07/11] selftests: tracing: Add syntax " Masami Hiramatsu (Google)
2026-08-02 8:19 ` [PATCH v11 08/11] tracing: wprobe: Add wprobe event trigger Masami Hiramatsu (Google)
2026-08-02 8:20 ` [PATCH v11 09/11] selftests: ftrace: Add wprobe trigger testcase Masami Hiramatsu (Google)
2026-08-02 8:20 ` [PATCH v11 10/11] tracing/wprobe: Support BTF typecast in fetchargs Masami Hiramatsu (Google)
2026-08-02 8:20 ` [PATCH v11 11/11] tracing/wprobe: Support BTF typecast in wprobe trigger command Masami Hiramatsu (Google)
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