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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 References: <178611679753.237811.10190793347982785419.stgit@devnote2> <178611688737.237811.17143803996766057381.stgit@devnote2> Content-Language: en-US From: Jinchao Wang In-Reply-To: <178611688737.237811.17143803996766057381.stgit@devnote2> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 8/7/2026 11:34 PM, Masami Hiramatsu (Google) wrote: > From: Masami Hiramatsu (Google) > > Add set_wprobe and clear_wprobe event triggers to dynamically attach > and detach hardware breakpoint address monitoring based on event field > contents. > This patch does not build with wprobe enabled. > Link: https://lore.kernel.org/all/59637b96946653393a7ad3c7de094094796b39c2.1785067572.git.wangjinchao600@gmail.com/ > > Signed-off-by: Masami Hiramatsu (Google) > --- > Changes in v12: > - Decrement trigger data->count only when watchpoint state is actually changed. > - Remove dyn_event_ops_mutex to fix lockdep circular dependency deadlock. > - Add event_trigger_init() call to prevent premature freeing of trigger_data. > - Use WRITE_ONCE() when modifying tw->addr to pair with READ_ONCE(). > - Add missing braces to else-block in wprobe_trigger_print(). > - Initialize tw->addr only after trace_event_enable_disable() succeeds. > - Counter counts only if the trigger is actually working. > Changes in v11: > - Soft-enable (register) wprobe event on WPROBE_DEFAULT_CLEAR_ADDRESS. > - Add work_pending check before updating tw->addr. > --- > Documentation/trace/wprobetrace.rst | 98 +++++++ > include/linux/trace_events.h | 1 > kernel/trace/Kconfig | 10 + > kernel/trace/trace.h | 1 > kernel/trace/trace_dynevent.h | 1 > kernel/trace/trace_events_trigger.c | 2 > kernel/trace/trace_probe.c | 2 > kernel/trace/trace_probe.h | 9 + > kernel/trace/trace_wprobe.c | 527 +++++++++++++++++++++++++++++++++++ > 9 files changed, 648 insertions(+), 3 deletions(-) > > diff --git a/Documentation/trace/wprobetrace.rst b/Documentation/trace/wprobetrace.rst > index ad5f089b5ef5..a579347735d2 100644 > --- a/Documentation/trace/wprobetrace.rst > +++ b/Documentation/trace/wprobetrace.rst > @@ -68,3 +68,101 @@ Here is an example to add a wprobe event on a variable `jiffies`. > -0 [000] d.Z1. 717.026373: my_jiffies: (tick_do_update_jiffies64+0xbe/0x130) > > You can see the code which writes to `jiffies` is `tick_do_update_jiffies64()`. > + > +Combination with trigger action > +------------------------------- > +The event trigger action can extend the utilization of this wprobe. > + > +- set_wprobe:WPEVENT:FIELD[+|-ADJUST] > +- clear_wprobe:WPEVENT[:FIELD[+|-]ADJUST] Both forms accept an optional [:COUNT] which is not documented here. > + > +Set these triggers to the target event, then the WPROBE event will be > +setup to trace the memory access at FIELD[+|-ADJUST] address. > +When clear_wprobe is hit, if FIELD is NOT specified, the WPEVENT is > +forcibly cleared. If FIELD[[+|-]ADJUST] is set, it clears WPEVENT only > +if its watching address is the same as the FIELD[[+|-]ADJUST] value. Two forms of adjust: [+|-ADJUST] [+|-]ADJUST > + > +Notes: > +The set_wprobe trigger does not change the type and length, these > +must be set when creating a new wprobe. > + > +The WPROBE event must be disabled when setting the new trigger > +and it will be busy afterwards. Recommended usage is to add a new > +wprobe at NULL address and keep disabled. > + > diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig > index d9b6fa5c35d9..5fd8ed63c516 100644 > --- a/kernel/trace/Kconfig > +++ b/kernel/trace/Kconfig > @@ -876,6 +876,16 @@ config WPROBE_EVENTS > Those events can be inserted wherever hardware breakpoints can be > set, and record accessed memory address and values. > > +config WPROBE_TRIGGERS > + depends on WPROBE_EVENTS > + depends on HAVE_MODIFY_LOCAL_HW_BREAKPOINT_ADDR > + bool > + default y > + help > + This adds an event trigger which will set the wprobe on a specific > + field of an event. This allows user to trace the memory access of > + an address pointed by the event field. > + > config BPF_EVENTS > depends on BPF_SYSCALL > depends on (KPROBE_EVENTS || UPROBE_EVENTS) && PERF_EVENTS > diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h > index 64851a8d021f..a789a722bc8b 100644 > --- a/kernel/trace/trace.h > +++ b/kernel/trace/trace.h > @@ -1983,6 +1983,7 @@ trigger_data_alloc(struct event_command *cmd_ops, char *cmd, char *param, > void *private_data); > extern void trigger_data_free(struct event_trigger_data *data); > extern int event_trigger_init(struct event_trigger_data *data); > +extern void event_trigger_free(struct event_trigger_data *data); > extern int trace_event_trigger_enable_disable(struct trace_event_file *file, > int trigger_enable); > extern void update_cond_flag(struct trace_event_file *file); > diff --git a/kernel/trace/trace_dynevent.h b/kernel/trace/trace_dynevent.h > index beee3f8d7544..77c2c84dcdb5 100644 > --- a/kernel/trace/trace_dynevent.h > +++ b/kernel/trace/trace_dynevent.h > @@ -64,6 +64,7 @@ struct dyn_event { > }; > > extern struct list_head dyn_event_list; > +extern struct mutex dyn_event_ops_mutex; dyn_event_ops_mutex is not needed anymore. > > static inline > int dyn_event_init(struct dyn_event *ev, struct dyn_event_operations *ops) > diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c > index ad83419cb420..fa409ebd73c2 100644 > --- a/kernel/trace/trace_events_trigger.c > +++ b/kernel/trace/trace_events_trigger.c > @@ -589,7 +589,7 @@ int event_trigger_init(struct event_trigger_data *data) > * Usually used directly as the @free method in event trigger > * implementations. > */ > -static void > +void > event_trigger_free(struct event_trigger_data *data) > { > if (WARN_ON_ONCE(data->ref <= 0)) > diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c > index 9f4cad18977a..36e07275a04d 100644 > --- a/kernel/trace/trace_probe.c > +++ b/kernel/trace/trace_probe.c > @@ -20,7 +20,7 @@ > #undef C > #define C(a, b) b > > -static const char *trace_probe_err_text[] = { ERRORS }; > +const char *trace_probe_err_text[] = { ERRORS }; > > static const char *reserved_field_names[] = { > "common_type", > diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h > index 6543d4c2cda5..e08f17c99138 100644 > --- a/kernel/trace/trace_probe.h > +++ b/kernel/trace/trace_probe.h > @@ -634,7 +634,12 @@ extern int traceprobe_define_arg_fields(struct trace_event_call *event_call, > C(TYPECAST_SYM_OFFSET, "@SYM+/-OFFSET with typecast needs parentheses"), \ > C(USED_ARG_NAME, "This argument name is already used"), \ > C(WPROBE_NO_MAXACT, "Watchpoint probe does not support maxactive"), \ > - C(WPROBE_NO_SIBLING, "Watchpoint probe does not support sibling probes"), > + C(WPROBE_NO_SIBLING, "Watchpoint probe does not support sibling probes"), \ > + C(WPROBE_ON_KPROBE, "Wprobe trigger is not supported on kprobe event"), \ > + C(WPROBE_NOT_FOUND, "Target wprobe event is not found"), \ > + C(WPROBE_BUSY, "Target wprobe event is already enabled"), \ > + C(WPROBE_NEED_FIELD, "Wprobe trigger requires a target field"), \ > + C(WPROBE_BAD_FIELD, "Target field must be pointer size"), > > #undef C > #define C(a, b) TP_ERR_##a > @@ -658,6 +663,8 @@ void __trace_probe_log_err(int offset, int err); > > DEFINE_FREE(trace_probe_log_clear, const char *, if (_T) trace_probe_log_clear()) > > +extern const char *trace_probe_err_text[]; > + > #define trace_probe_log_err(offs, err) \ > __trace_probe_log_err(offs, TP_ERR_##err) > > diff --git a/kernel/trace/trace_wprobe.c b/kernel/trace/trace_wprobe.c > index df592d9280a4..c64bbdc90a40 100644 > --- a/kernel/trace/trace_wprobe.c > +++ b/kernel/trace/trace_wprobe.c > @@ -6,7 +6,9 @@ > */ > #define pr_fmt(fmt) "trace_wprobe: " fmt > > +#include > #include > +#include > #include > #include > #include > @@ -15,11 +17,16 @@ > #include > #include > #include > +#include > #include > #include > +#include > +#include > +#include > > #include > > +#include "trace.h" > #include "trace_dynevent.h" > #include "trace_probe.h" > #include "trace_probe_kernel.h" > @@ -50,6 +57,17 @@ struct trace_wprobe { > int len; > int type; > const char *symbol; > + raw_spinlock_t lock; > + struct irq_work irq_work; > + struct work_struct work; > + atomic_t missed; Is `missed` read somewhere? I searched this file, only found set and inc.