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Message-ID: <175785897434.234168.6798590787777427098.stgit@devnote2>
Date: Sun, 14 Sep 2025 23:09:34 +0900
From: "Masami Hiramatsu (Google)" <mhiramat@...nel.org>
To: Steven Rostedt <rostedt@...dmis.org>,
Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...nel.org>,
x86@...nel.org
Cc: Jinchao Wang <wangjinchao600@...il.com>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
Masami Hiramatsu <mhiramat@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>,
Borislav Petkov <bp@...en8.de>,
Dave Hansen <dave.hansen@...ux.intel.com>,
"H . Peter Anvin" <hpa@...or.com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Ian Rogers <irogers@...gle.com>,
linux-kernel@...r.kernel.org,
linux-trace-kernel@...r.kernel.org,
linux-doc@...r.kernel.org,
linux-perf-users@...r.kernel.org
Subject: [PATCH v4 0/8] tracing: wprobe: Add wprobe for watchpoint
Hi,
Here is the 4th 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 a dynamically
allocated objects too.
The previous version is here:
https://lore.kernel.org/all/175755135002.153203.324836519360617091.stgit@devnote2/
In this version, I updated to use Jinchao's x86 HWBP patches[1][2]
as [2/8][3/8], and update the kerneldoc for
modify_wide_hw_breakpoint_local() [4/8] according to Randy's comment[3].
[1] https://lore.kernel.org/all/20250912101145.465708-2-wangjinchao600@gmail.com/
[2] https://lore.kernel.org/all/20250912101145.465708-3-wangjinchao600@gmail.com/
[3] https://lore.kernel.org/all/6b5e5d3e-5db8-44f2-8dca-42f317be8e0d@infradead.org/
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@...fies:8 value=+0($addr)' >> dynamic_events
echo 1 > events/wprobes/my_jiffies/enable
Moreover, this can be combined with event trigger to trace the memory
accecss on slab objects. The trigger syntax is;
set_wprobe:WPROBE_EVENT:FIELD[+OFFSET] [if FILTER]
clear_wprobe:WPROBE_EVENT[:FIELD[+OFFSET]] [if FILTER]
set_wprobe sets WPROBE_EVENT's watch address on FIELD[+OFFSET].
clear_wprobe clears WPROBE_EVENT's watch address if it is set to
FIELD[+OFFSET]. If FIELD is omitted, forcibly clear the watch address
when trigger event is hit.
For example, trace the first 8 byte of the dentry data structure passed
to do_truncate() until it is deleted by __dentry_kill().
(Note: all tracefs setup uses '>>' so that it does not kick do_truncate())
# echo 'w:watch rw@0:8 address=$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: 16/16 #P:8
#
# _-----=> irqs-off/BH-disabled
# / _----=> need-resched
# | / _---=> hardirq/softirq
# || / _--=> preempt-depth
# ||| / _-=> migrate-disable
# |||| / delay
# TASK-PID CPU# ||||| TIMESTAMP FUNCTION
# | | | ||||| | |
sh-113 [004] ..... 6.467444: truncate: (do_truncate+0x4/0x120) dentry=0xffff8880044f0fd8
sh-113 [004] ..Zff 6.468534: watch: (lookup_fast+0xaa/0x150) address=0xffff8880044f0fd8 value=0x200080
sh-113 [004] ..Zff 6.468542: watch: (step_into+0x82/0x360) address=0xffff8880044f0fd8 value=0x200080
sh-113 [004] ..Zff 6.468547: watch: (step_into+0x9f/0x360) address=0xffff8880044f0fd8 value=0x200080
sh-113 [004] ..Zff 6.468553: watch: (path_openat+0xb3a/0xe70) address=0xffff8880044f0fd8 value=0x200080
sh-113 [004] ..Zff 6.468557: watch: (path_openat+0xb9a/0xe70) address=0xffff8880044f0fd8 value=0x200080
sh-113 [004] ..... 6.468563: truncate: (do_truncate+0x4/0x120) dentry=0xffff8880044f0fd8
sh-113 [004] ...1. 6.469826: dentry_kill: (__dentry_kill+0x0/0x220) dentry=0xffff8880044f0ea0
sh-113 [004] ...1. 6.469859: dentry_kill: (__dentry_kill+0x0/0x220) dentry=0xffff8880044f0d68
rm-118 [001] ..Zff 6.472360: watch: (lookup_fast+0xaa/0x150) address=0xffff8880044f0fd8 value=0x200080
rm-118 [001] ..Zff 6.472366: watch: (step_into+0x82/0x360) address=0xffff8880044f0fd8 value=0x200080
rm-118 [001] ..Zff 6.472370: watch: (step_into+0x9f/0x360) address=0xffff8880044f0fd8 value=0x200080
rm-118 [001] ..Zff 6.472386: watch: (lookup_fast+0xaa/0x150) address=0xffff8880044f0fd8 value=0x200080
rm-118 [001] ..Zff 6.472390: watch: (step_into+0x82/0x360) address=0xffff8880044f0fd8 value=0x200080
rm-118 [001] ..Zff 6.472394: watch: (step_into+0x9f/0x360) address=0xffff8880044f0fd8 value=0x200080
rm-118 [001] ..Zff 6.472415: watch: (lookup_one_qstr_excl+0x2c/0x150) address=0xffff8880044f0fd8 value=0x200080
rm-118 [001] ..Zff 6.472419: watch: (lookup_one_qstr_excl+0xd5/0x150) address=0xffff8880044f0fd8 value=0x200080
rm-118 [001] ..Zff 6.472424: watch: (may_delete+0x18/0x200) address=0xffff8880044f0fd8 value=0x200080
rm-118 [001] ..Zff 6.472428: watch: (may_delete+0x194/0x200) address=0xffff8880044f0fd8 value=0x200080
rm-118 [001] ..Zff 6.472446: watch: (vfs_unlink+0x63/0x1c0) address=0xffff8880044f0fd8 value=0x200080
rm-118 [001] d.Z.. 6.472528: watch: (dont_mount+0x19/0x30) address=0xffff8880044f0fd8 value=0x200180
rm-118 [001] ..Zff 6.472533: watch: (vfs_unlink+0x11a/0x1c0) address=0xffff8880044f0fd8 value=0x200180
rm-118 [001] ..Zff 6.472538: watch: (vfs_unlink+0x12e/0x1c0) address=0xffff8880044f0fd8 value=0x200180
rm-118 [001] d.Z1. 6.472543: watch: (d_delete+0x61/0xa0) address=0xffff8880044f0fd8 value=0x200080
rm-118 [001] d.Z1. 6.472547: watch: (dentry_unlink_inode+0x14/0x110) address=0xffff8880044f0fd8 value=0x200080
rm-118 [001] d.Z1. 6.472551: watch: (dentry_unlink_inode+0x1e/0x110) address=0xffff8880044f0fd8 value=0x80
rm-118 [001] d.Z.. 6.472563: watch: (fast_dput+0x8d/0x120) address=0xffff8880044f0fd8 value=0x80
rm-118 [001] ...1. 6.472567: dentry_kill: (__dentry_kill+0x0/0x220) dentry=0xffff8880044f0fd8
sh-113 [004] ...2. 6.473049: dentry_kill: (__dentry_kill+0x0/0x220) dentry=0xffff888006e383a8
Thank you,
---
Jinchao Wang (2):
x86/hw_breakpoint: Unify breakpoint install/uninstall
x86/hw_breakpoint: Add arch_reinstall_hw_breakpoint
Masami Hiramatsu (Google) (6):
tracing: wprobe: Add watchpoint probe event based on hardware breakpoint
HWBP: Add modify_wide_hw_breakpoint_local() API
tracing: wprobe: Add wprobe event trigger
selftests: tracing: Add a basic testcase for wprobe
selftests: tracing: Add syntax testcase for wprobe
selftests: ftrace: Add wprobe trigger testcase
Documentation/trace/index.rst | 1
Documentation/trace/wprobetrace.rst | 157 +++
arch/Kconfig | 10
arch/x86/Kconfig | 1
arch/x86/include/asm/hw_breakpoint.h | 8
arch/x86/kernel/hw_breakpoint.c | 148 ++-
include/linux/hw_breakpoint.h | 6
include/linux/trace_events.h | 3
kernel/events/hw_breakpoint.c | 37 +
kernel/trace/Kconfig | 24
kernel/trace/Makefile | 1
kernel/trace/trace.c | 9
kernel/trace/trace.h | 5
kernel/trace/trace_probe.c | 22
kernel/trace/trace_probe.h | 8
kernel/trace/trace_wprobe.c | 1115 ++++++++++++++++++++
.../ftrace/test.d/dynevent/add_remove_wprobe.tc | 68 +
.../test.d/dynevent/wprobes_syntax_errors.tc | 20
.../ftrace/test.d/trigger/trigger-wprobe.tc | 48 +
19 files changed, 1626 insertions(+), 65 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.tc
--
Masami Hiramatsu (Google) <mhiramat@...nel.org>
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