Hi, Here is the 10th 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/178429796992.157981.3393977217853767915.stgit@devnote2/ This version add BTF support in wprobe trigger command[11/11]. With this feature, user do not need to decode the offset of structure fields. (Since the previous version lacked base-commit tag, Sashiko failed to apply it for review. Thus this is just add a BTF support.) To support kprobe events, we need to check the previous NMI context or need to use an atomic refcount etc. But that should be another patch for review. To support arm64, we need to avoid major pagefault on single-stepping issue. I think we can solve it with checking whether the address is the kernel (which must not cause a major page fault), or not. 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($addr)' >> dynamic_events echo 1 > events/wprobes/my_jiffies/enable Moreover, this can be combined with event trigger to trace the memory accecss on slab objects. The trigger syntax is; set_wprobe:WPROBE_EVENT:FIELD[+OFFSET] [if FILTER] clear_wprobe:WPROBE_EVENT[:FIELD[+OFFSET]] [if FILTER] set_wprobe sets WPROBE_EVENT's watch address on FIELD[+OFFSET]. clear_wprobe clears WPROBE_EVENT's watch address if it is set to FIELD[+OFFSET]. If FIELD is omitted, forcibly clear the watch address when trigger event is hit. For example, trace the first 8 byte of the dentry data structure passed to do_truncate() until it is deleted by dentry_kill(). (Note: all tracefs setup uses '>>' so that it does not kick do_truncate()) # echo 'w:watch rw@0:8 address=$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: 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: 1a416ae446afa42d2d8500ce25bd61c564508721 Jinchao Wang (2): x86/hw_breakpoint: Unify breakpoint install/uninstall x86/hw_breakpoint: Add arch_reinstall_hw_breakpoint Masami Hiramatsu (Google) (9): 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 HWBP: Add modify_wide_hw_breakpoint_local() API 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 | 20 arch/x86/Kconfig | 2 arch/x86/include/asm/hw_breakpoint.h | 8 arch/x86/kernel/hw_breakpoint.c | 164 ++- include/linux/hw_breakpoint.h | 6 include/linux/trace_events.h | 3 kernel/events/hw_breakpoint.c | 61 + kernel/trace/Kconfig | 24 kernel/trace/Makefile | 1 kernel/trace/trace.c | 9 kernel/trace/trace.h | 7 kernel/trace/trace_events_trigger.c | 12 kernel/trace/trace_probe.c | 24 kernel/trace/trace_probe.h | 14 kernel/trace/trace_wprobe.c | 1300 ++++++++++++++++++++ tools/testing/selftests/ftrace/config | 2 .../ftrace/test.d/dynevent/add_remove_wprobe.tc | 63 + .../test.d/dynevent/wprobes_syntax_errors.tc | 20 .../test.d/trigger/trigger-wprobe-btf-offset.tc | 73 + .../test.d/trigger/trigger-wprobe-btf-typecast.tc | 80 + .../ftrace/test.d/trigger/trigger-wprobe.tc | 70 + 23 files changed, 2056 insertions(+), 71 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]>
