On Sun, 2 Aug 2026 17:18:25 +0900 "Masami Hiramatsu (Google)" <[email protected]> wrote:
> 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, > > --- Oops, I found I missed base-commit: tag here... I'll update my tool to add it automatically. Thanks, > > 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) <[email protected]> -- Masami Hiramatsu (Google) <[email protected]>
