From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5843337882A; Fri, 17 Jul 2026 14:19:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784297978; cv=none; b=Ewp4WqBhKl+UhKkq0FDHWiVi9GXEKtt0W//HK3pQ1dRriN2m1SiqXpCTm/OlwxicPjgnCO9xrjobjY9yBdweWDHqaI/tKgslcmUJhwsCHOyNlgzm/3QlsaHx6/u3ds3KKBBR4SqGxQpUYs1SZpVoID8gr650HMjQqQADUsdndjM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784297978; c=relaxed/simple; bh=MiiJjSGhj0f7Ddd8V6wAisG9FoBPJG6SHqKrqnTk6SQ=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version:Content-Type; b=EYRDbZxn2l3CWe5hTadNDncI230dJdaL1kqkeoPCC99HtsJZjJ6zPqvaCMOpykZSdpYDm+h2nOPLALBiqtbo6yH/JycsCgHKGAJPT4fKXJrfkAI8rlZLspiwEvWn/TiBbGGHTrWQyATlHDQkWCe0Yfvyt67uL+hB1crQg23ayjA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=YPHSsnfy; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="YPHSsnfy" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 05C681F000E9; Fri, 17 Jul 2026 14:19:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1784297976; bh=pnb+PmHU+eYWA/ewAFyGJG8G3iSSppjHq+JlExi3Jrw=; h=From:To:Cc:Subject:Date; b=YPHSsnfy5wiXdjFYDGm9up/9X82XHVLA66F4rGlMJ9Nr1JNtfSp4i4m8gB84wBd06 6v7jZ/LGlAr7AppN3Lnxz1T6y5ky3RY9Wapv1A85G+jLXC2cLreH8GOGcjAmNwRzB3 spM+dTCOVy/W+slj8MxlU0jZI+KZoneu1jzlCOHpA/UQkQ6/nHfAR2mZAk9r+FSI9S j4VgCWdIGmvo5Wc9KDc19gEyHmqR8DqLbGRrQPkW376j1sAB1SM8jykkSFG0AsycNI fywSNDbAPrWkOMeqbVxbBVEi+4+59+zdtzz+w5kFtJKvFk68kv+hHq14DeNLGCVHcJ 8pvXTgZYRXZKQ== From: "Masami Hiramatsu (Google)" To: Steven Rostedt , Peter Zijlstra , Ingo Molnar , x86@kernel.org Cc: Jinchao Wang , Mathieu Desnoyers , Masami Hiramatsu , Thomas Gleixner , Borislav Petkov , Dave Hansen , "H . Peter Anvin" , Alexander Shishkin , Ian Rogers , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-perf-users@vger.kernel.org Subject: [PATCH v9 00/10] tracing: wprobe: x86: Add wprobe for watchpoint Date: Fri, 17 Jul 2026 23:19:30 +0900 Message-ID: <178429796992.157981.3393977217853767915.stgit@devnote2> X-Mailer: git-send-email 2.43.0 User-Agent: StGit/0.19 Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit Hi, Here is the 9th 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/178417033089.209165.16717079876036408877.stgit@devnote2/ This version fixes issues commented by Sashiko[1] and add BTF typecast support [10/10]. Let me list it up. [1] https://sashiko.dev/#/patchset/178417033089.209165.16717079876036408877.stgit%40devnote2 [PATCH 1/10] - Rebased on probes/for-next branch. - Add WPROBE_NO_SIBLING error log to explicitly reject sibling probes since event triggers identify the target wprobe by event name. - Use traceprobe_parse_event_name() to properly validate group/event names instead of using the raw command string directly. - Generate unique event name (w_0x) for anonymous address-based watchpoints to avoid naming collisions. - Call traceprobe_update_arg() in __register_trace_wprobe() to resolve @symbol fetch arguments, consistent with kprobe and fprobe. [PATCH 3/10] - Fix command check logic to prevent early exit under 'set -e' (errexit) when grep or test fails. - Simplify enable/disable status checks by removing cat pipes. [PATCH 5/10] - Define DR_LEN_MASK and DR_TYPE_MASK locally to eliminate magic numbers in decode_dr7() and setup_hwbp(). - Temporarily disable the active slot in setup_hwbp() before updating the address register to avoid spurious debug exceptions. [PATCH 6/10] - Update commit message. [PATCH 7/10] - Add lockdep_assert_irqs_disabled() to enforce and document the interrupt-disabled calling context requirement. - Implement state rollback logic in modify_wide_hw_breakpoint_local() to prevent inconsistent state on architecture update failure. [PATCH 8/10] - Make event_trigger_free() non-static to solve build dependency. - Sync irq_work and work inside __unregister_trace_wprobe() before clearing tw->bp_event to prevent concurrent NULL pointer dereference. - Introduce private_free destructor in struct event_trigger_data to safely release wprobe_trigger_data after tracepoint readers exit. - Fix filter memory leak in wprobe_trigger_cmd_parse() on the error handling path of trace_event_try_get_ref() failure. - Avoid overwriting tw->addr on clear_wprobe trigger registration to prevent active watchpoint corruption and hardware breakpoint leak. [PATCH 9/10] - Drop dentry cache after removing tempfile for on-disk filesystem. 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. Usage ----- The basic usage of this wprobe is similar to other probes; w:[GRP/][EVENT] [r|w|rw]@ [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, --- Jinchao Wang (2): x86/hw_breakpoint: Unify breakpoint install/uninstall x86/hw_breakpoint: Add arch_reinstall_hw_breakpoint Masami Hiramatsu (Google) (8): 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 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 | 1185 ++++++++++++++++++++ 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-typecast.tc | 80 + .../ftrace/test.d/trigger/trigger-wprobe.tc | 70 + 22 files changed, 1868 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-typecast.tc create mode 100644 tools/testing/selftests/ftrace/test.d/trigger/trigger-wprobe.tc -- Masami Hiramatsu (Google)