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 C14CD3DAAC5; Fri, 25 Sep 2026 11:10:56 +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=1790334658; cv=none; b=QUQwjvK1oskGmITffPCcdcZhj5gU8qQktitbawlQo56hiGdrcuR4rQu+tX+7iKSt7ERwGQ384b/1qtyqkzEyk/UshXNDZyqQxdLRCRDrLMLRAKqU4UnYWWf45oZnNXyrseu+WmFcKx8YQkAe06ryc64CY3HgOqh9cVCffaM521U= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790334658; c=relaxed/simple; bh=8UGOe1dKqaiVw06wc6DnRzu9DjCqbkBJJXWZeEoDB68=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version:Content-Type; b=krkgHjzM9eXsknJg4dWxmF5e/+Aiy5baykR7hK2f1TXih6XyXmbusQ0pw4g1wSxkX7iXuXu0k2vkYSK6qslBiNWo7pKlkP44qSBMRWM14VrIv2SmfFCgGuxtg8npu0u6XdfpAk6zTOJ7RdqE0euavQKETf47cy7xFRV83y+0fpQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=O5fMZbsu; 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="O5fMZbsu" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7AB571F000FF; Fri, 25 Sep 2026 11:10:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1790334656; bh=HqVuKM3tcsZDDJcHWCt7tUAlGuDXSt1QoovIwV67M24=; h=From:To:Cc:Subject:Date; b=O5fMZbsuW7tou8+IHgU6s1q9XBHk5fAqKUNdwgWCPtwSKT45m5G5FUl6pIEIx7gy9 3jXx+Wzov5zuR0OgLKctsU9BYMdKgaSaFmq+22LkDI6+MVPTX4DsXaagaMlIWOgvwB ZcHIXoc1DNMDVXq1tvdwLHC2SZk5oq2z5PIbD4xo5Jp6FE7TPr7i8iHBPQ2XeEBvBd CbiZl6PiQ9zZbwbErzHw92rjRkEq1NrAXC9XKV28Vn8NITPVpraLA9X6pfJlj2Buml oPlABmexf9Lm98DUaYz1H+IUJfU1b1aEzXyk82jMHQwAFQCTXmT0dluJfDHdjysb0c 7fhotJMWFwkFg== From: "Masami Hiramatsu (Google)" To: Steven Rostedt , Peter Zijlstra , Ingo Molnar 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, x86@kernel.org Subject: [PATCH v18 00/11] tracing: wprobe: x86: Add wprobe for watchpoint Date: Fri, 25 Sep 2026 20:10:44 +0900 Message-ID: <179033464327.136630.864883694296882051.stgit@devnote2> X-Mailer: git-send-email 2.43.0 User-Agent: StGit/0.19 Precedence: bulk X-Mailing-List: linux-kernel@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 18th 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/179005108298.388919.4535333252892590932.stgit@devnote2/ In this version: - Dropped MCE related fix because it is merged in -tip tree. - Dropped the patches related to making DR7 updates NMI-safe (and the associated KVM guest debug register isolation patch) because wprobe itself does not support updating DR7 in NMI context (wprobe explicitly rejects execution in NMI context via in_nmi()). Those patches are still valid for KGDB, but not related to wprobe. - Addressed review comments from Sashiko bot on wprobe triggers, selftests, and BTF struct offset resolution: - Add register_wide_hw_breakpoint_cpuslocked() API to hw_breakpoint and use it under cpus_read_lock() in __register_trace_wprobe() to avoid both the CPU hotplug race and lockdep recursive locking warnings. - Added early check for in_nmi() in wprobe_trigger() before acquiring tw->lock to avoid deadlock if interrupted by an NMI. - Always evaluate __wprobe_count_func() under tw->lock in wprobe_trigger() to eliminate the TOCTOU race for counted triggers. - Added "set_wprobe:":README requirement to wprobe trigger selftests so they are gracefully skipped if CONFIG_WPROBE_TRIGGERS=n. - Added clear_trace in trigger-wprobe-hotplug.tc after taking CPU offline to avoid falsely matching events logged prior to offlining. - In get_offset_of_field(), clarified that the containing structure/union type is checked for kflag (renamed mtype to container with comments) and verified that the resolved bit offset is byte-aligned. - Updated all "Assisted-by:" tags across all commits to "Assisted-by: LLM". Detailed changes are here. Changes in v18: - Drop patch "x86/mce: Fix hardware debug register corruption on task migration" - Drop patch "perf/x86, KVM: Prevent host debug register leak into guest OS on NMI". - Drop patch "x86/hw_breakpoints: Make DR7 updates NMI safe". - Update "Assisted-by:" tags across all commits to "Assisted-by: LLM". [01/11] - Drop perf_guest_in_guest() check and cpu_dr7_seq sequence loop since wprobe does not support updating DR7 in NMI context. [03/11] - Add register_wide_hw_breakpoint_cpuslocked() API. [08/11] - Use register_wide_hw_breakpoint_cpuslocked() under cpus_read_lock() in __register_trace_wprobe() to avoid CPU hotplug race and lockdep recursive locking warnings. - Return early on in_nmi() in wprobe_trigger() before taking tw->lock to prevent NMI deadlock. - Always evaluate __wprobe_count_func() under tw->lock in wprobe_trigger() to fix TOCTOU race for counted triggers. - Drop redundant in_nmi() check from __wprobe_count_func(). - Defer data->count decrement to wprobe_trigger() under tw->lock after successful hardware update to avoid consuming count on missed triggers and prevent counter underflow. [09/11] - Add "set_wprobe:":README to requires line in wprobe trigger tests so they are skipped if CONFIG_WPROBE_TRIGGERS is disabled. - Clear trace buffer after taking CPU offline in trigger-wprobe-hotplug.tc to avoid matching watchpoint events logged prior to offlining. [10/11] - Add "set_wprobe:":README to requires line in trigger-wprobe-btf-typecast.tc so the test is skipped if CONFIG_WPROBE_TRIGGERS is disabled. [11/11] - In get_offset_of_field(), rename mtype to container and document that it represents the containing structure/union type (handling anonymous structures/unions) rather than member's own type. - In get_offset_of_field(), verify bit offset is byte-aligned before returning byte offset. - Add "set_wprobe:":README to requires line in trigger-wprobe-btf-offset.tc so the test is skipped if CONFIG_WPROBE_TRIGGERS is disabled. 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 linux-trace/probes/fixes. Usage ----- The basic usage of this wprobe is similar to other probes; w:[GRP/][EVENT] [r|w|rw]@[:LEN] [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($addr)' >> dynamic_events echo 1 > events/wprobes/my_jiffies/enable Moreover, this can be combined with event trigger to trace the memory access on slab objects. The trigger syntax is; set_wprobe:WPROBE_EVENT:FIELD[+|-OFFSET][:COUNT] [if FILTER] clear_wprobe:WPROBE_EVENT[:FIELD[+|-OFFSET][:COUNT]] [if FILTER] set_wprobe sets WPROBE_EVENT's watch address on FIELD[+|-OFFSET]. clear_wprobe clears WPROBE_EVENT's watch address if it is set to FIELD[+|-OFFSET]. If FIELD is omitted, forcibly clear the watch address when trigger event is hit. For example, trace the first 8 byte of the dentry data structure passed to do_truncate() until it is deleted by dentry_kill(). (Note: all tracefs setup uses '>>' so that it does not kick do_truncate()) # echo 'w:watch rw@-1:8 address=$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: 0c4256196b3a105307e2235fbfd85e768bbcdd0f Jinchao Wang (1): x86/hw_breakpoints: Add arch_modify_local_hw_breakpoint_addr() API Masami Hiramatsu (Google) (10): HWBP: Add modify_local_hw_breakpoint_addr() API perf/hw_breakpoint: Add register_wide_hw_breakpoint_cpuslocked() API tracing/wprobe: Add wprobe (watchpoint probe) trace event support 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 set_wprobe and clear_wprobe event triggers selftests: tracing: Add wprobe trigger testcases tracing/wprobe: Support BTF typecast in fetchargs tracing/wprobe: Support BTF struct offset resolution in set_wprobe trigger Documentation/trace/index.rst | 1 Documentation/trace/wprobetrace.rst | 200 ++ arch/Kconfig | 18 arch/x86/Kconfig | 2 arch/x86/include/asm/hw_breakpoint.h | 2 arch/x86/kernel/hw_breakpoint.c | 51 + include/linux/hw_breakpoint.h | 15 include/linux/trace_events.h | 3 kernel/events/hw_breakpoint.c | 86 + 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 | 36 kernel/trace/trace_probe.h | 22 kernel/trace/trace_wprobe.c | 1707 ++++++++++++++++++++ tools/testing/selftests/ftrace/config | 3 .../ftrace/test.d/dynevent/add_remove_wprobe.tc | 66 + .../test.d/dynevent/wprobes_syntax_errors.tc | 23 .../test.d/trigger/trigger-wprobe-btf-offset.tc | 85 + .../test.d/trigger/trigger-wprobe-btf-typecast.tc | 85 + .../test.d/trigger/trigger-wprobe-hotplug.tc | 153 ++ .../test.d/trigger/trigger-wprobe-syntax-errors.tc | 37 .../ftrace/test.d/trigger/trigger-wprobe.tc | 107 + 25 files changed, 2731 insertions(+), 13 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-hotplug.tc create mode 100644 tools/testing/selftests/ftrace/test.d/trigger/trigger-wprobe-syntax-errors.tc create mode 100644 tools/testing/selftests/ftrace/test.d/trigger/trigger-wprobe.tc -- Masami Hiramatsu (Google)