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 B366E30ACEE; Tue, 22 Sep 2026 04:24:50 +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=1790051092; cv=none; b=axuLl9lBnQ+eqFx4Hzwwg7KsfzS4KFUAAqgBnDA8s61VGTBgDlHDNIjW1qYnRcUpLBWY2B0pqydxVSUuMPSEChCarF3gd4LBhBL64DVhdp+5KvU93iWdepbYT+RUIb3XnQwwlUlASNBChWoJz3eh9ZMD+eaVgQ7wwTboy3fTz6Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790051092; c=relaxed/simple; bh=i4MkXm/yV1H7XWzWv4Q5RGrm4Zfxy7GnBIxBDDXo1q0=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version:Content-Type; b=pwr+eXGbk/4b/WpZvT3iQu5X5fvi/VcsvlLcztVVWUHZDuzDloKl4IUJRJ6q2RzH6LsjkViD1+DffPLVQQw5Kz4BZTUAiHYRb9NlB7WZbSePK2N11WZR2ri2wtTEGblRhzX1aM/EEdAkTq3zcoe520j49I3WHOfxAYnotPsdV64= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=RYDthqLD; 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="RYDthqLD" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 058DE1F000FF; Tue, 22 Sep 2026 04:24:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1790051090; bh=n+bBSkNpi/kRS/hZysyRlmZaIh8zDYpB3ak/PpuETes=; h=From:To:Cc:Subject:Date; b=RYDthqLDkeCIqovfS0Gk0fcOkqxyxPMgPP/e7rViG1Bo47PJa4sdGKgT8EP+hS1/U Bwp+F82cFsR+CcLTrFcW5b1QCrDqRFyQAYp7kQ+OtoV2LNj8MpN/X1uG3vBmCEvL5L eN0ryc60F7DQSfjCG7ZD/QUlCtcV7ia1t8DhIPH6lnI2hAdTJONpXyFj/k5UX1t0YJ V3Nl4F2VTY9vnIRyNFflWlYWjqjcoDP5RWWXp6sbAJzyNLi/aViMIkh/xLFleAs6J1 qMz8hQ2UwnJcxSixRXrFkxTrog/FCe4OgDIH2mQw4J6JPAodDplXImtRC4PCuAh3f1 h/sNzQyzmZuDw== From: "Masami Hiramatsu (Google)" To: Steven Rostedt , Peter Zijlstra , Ingo Molnar , Sean Christopherson 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, Paolo Bonzini , kvm@vger.kernel.org Subject: [PATCH v17 00/13] tracing: wprobe: x86: Add wprobe for watchpoint Date: Tue, 22 Sep 2026 13:24:43 +0900 Message-ID: <179005108298.388919.4535333252892590932.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 17th 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/178939017565.94750.9431053336761330458.stgit@devnote2/ In this version, we address review feedback on KVM x86 debug register isolation and wprobe triggers: - Replaced the ad-hoc cpu_dr_in_guest flag with a generic perf_guest_in_guest() helper by adding an .in_guest callback to perf_guest_info_callbacks. KVM implements this using its existing vcpu->mode (IN_GUEST_MODE / EXITING_GUEST_MODE), requiring zero additional per-entry/exit state writes. (Sean, is this what you meant? I think we can also update the perf_guest_state() to check a new state flag, but that may need to update other callers.) - Added dynamic CPU hotplug callbacks to handle CPU offline and online events so breakpoints are cleanly unregistered and reinstalled on hotplugged CPUs, serialized with cpus_read_lock(). Added a selftest (trigger-wprobe-hotplug.tc) to verify this behavior. - Handled environmental watchpoint exhaustion in add_remove_wprobe.tc using exit_unresolved. - Restored EVENT_FILE_FL_SOFT_DISABLED_BIT in wprobe_trigger_free() to prevent wprobe tracepoint leaks upon trigger unregistration. - Checked trace_find_event_field() before skipping fields named "unlimited" in clear_wprobe trigger parsing. - Added tracepoint_synchronize_unregister() before freeing trigger data. - Implemented __wprobe_count_func() and wprobe_count_func() wrapper to consolidate precondition checks, update tw->missed on failure, and update the local hardware breakpoint before updating tw->addr. Detailed changes are here. Changes in v17: [02/13] - Drop changes to local_db_save() and local_db_restore(). - Drop cpu_dr_in_guest per-CPU flag. - Introduce .in_guest callback in perf_guest_info_callbacks and perf_guest_in_guest() helper to query vcpu->mode. - In arch_install_hw_breakpoint(), check perf_guest_in_guest(). [03/13] - Drop cpu_dr_in_guest checks in local_db_save(), local_db_restore(), and within_cpu_entry(). [04/13] - In arch_modify_local_hw_breakpoint_addr(), check perf_guest_in_guest() instead of cpu_dr_in_guest. [08/13] - Catch failures when enabling wprobe and call exit_unresolved in case hardware watchpoints are exhausted. [10/13] - Add dynamic CPU hotplug callbacks to handle CPU offline/online events and serialize wprobe_work_func() with cpus_read_lock(). - Restore EVENT_FILE_FL_SOFT_DISABLED_BIT in wprobe_trigger_free() to prevent wprobe event leaks when triggers are removed. - Check whether trigger event has "unlimited" field before skipping "unlimited" in clear_wprobe trigger parsing. - Call tracepoint_synchronize_unregister() before freeing trigger data via data->cmd_ops->free() on registration failure. - Implement __wprobe_count_func() helper to consolidate precondition checks, optimize shared work_pending logic, and update tw->missed when trigger preconditions fail in wprobe_count_func(). - In wprobe_trigger(), only check __wprobe_count_func() if trigger is uncounted, and update local breakpoint before committing tw->addr. [11/13] - Add trigger-wprobe-hotplug.tc to verify wprobe triggers across CPU offline and online transitions. 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 (2): x86/hw_breakpoints: Make DR7 updates NMI safe x86/hw_breakpoints: Add arch_modify_local_hw_breakpoint_addr() API Masami Hiramatsu (Google) (11): x86/mce: Fix hardware debug register corruption on task migration perf/x86, KVM: Prevent host debug register leak into guest OS on NMI HWBP: Add modify_local_hw_breakpoint_addr() 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/debugreg.h | 68 + arch/x86/include/asm/hw_breakpoint.h | 2 arch/x86/kernel/cpu/mce/core.c | 29 arch/x86/kernel/hw_breakpoint.c | 158 +- arch/x86/kernel/nmi.c | 7 arch/x86/kernel/traps.c | 10 include/linux/hw_breakpoint.h | 6 include/linux/perf_event.h | 9 include/linux/trace_events.h | 3 kernel/events/core.c | 5 kernel/events/hw_breakpoint.c | 48 + 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 | 1668 ++++++++++++++++++++ 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 | 150 ++ .../test.d/trigger/trigger-wprobe-syntax-errors.tc | 37 .../ftrace/test.d/trigger/trigger-wprobe.tc | 107 + virt/kvm/kvm_main.c | 12 32 files changed, 2805 insertions(+), 97 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)