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@xxxxxxxxx/ [2] https://lore.kernel.org/all/20250912101145.465708-3-wangjinchao600@xxxxxxxxx/ [3] https://lore.kernel.org/all/6b5e5d3e-5db8-44f2-8dca-42f317be8e0d@xxxxxxxxxxxxx/ 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($addr)' >> dynamic_events echo 1 > events/wprobes/my_jiffies/enable Moreover, this can be combined with event trigger to trace the memory accecss on slab objects. The trigger syntax is; set_wprobe:WPROBE_EVENT:FIELD[+OFFSET] [if FILTER] clear_wprobe:WPROBE_EVENT[:FIELD[+OFFSET]] [if FILTER] set_wprobe sets WPROBE_EVENT's watch address on FIELD[+OFFSET]. clear_wprobe clears WPROBE_EVENT's watch address if it is set to FIELD[+OFFSET]. If FIELD is omitted, forcibly clear the watch address when trigger event is hit. For example, trace the first 8 byte of the dentry data structure passed to do_truncate() until it is deleted by __dentry_kill(). (Note: all tracefs setup uses '>>' so that it does not kick do_truncate()) # echo 'w:watch rw@0:8 address=$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@xxxxxxxxxx>
