On Tue, 18 Aug 2026 17:22:27 +0800 Jinchao Wang <[email protected]> wrote:
> On 8/7/2026 11:34 PM, Masami Hiramatsu (Google) wrote: > > From: Masami Hiramatsu (Google) <[email protected]> > > > > 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. Oops, thanks for testing! Let me fix it. > > > Link: > > https://lore.kernel.org/all/59637b96946653393a7ad3c7de094094796b39c2.1785067572.git.wangjinchao...@gmail.com/ > > > > Signed-off-by: Masami Hiramatsu (Google) <[email protected]> > > --- > > 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`. > > <idle>-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. Ah, indeed. > > > + > > +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 OK. [+ADJUST|-ADJUST] is correct form. > > > > + > > +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. Ah, good catch! > > > > > 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 <linux/atomic.h> > > #include <linux/compiler.h> > > +#include <linux/errno.h> > > #include <linux/hw_breakpoint.h> > > #include <linux/kallsyms.h> > > #include <linux/list.h> > > @@ -15,11 +17,16 @@ > > #include <linux/perf_event.h> > > #include <linux/rculist.h> > > #include <linux/security.h> > > +#include <linux/spinlock.h> > > #include <linux/tracepoint.h> > > #include <linux/uaccess.h> > > +#include <linux/workqueue.h> > > +#include <linux/irq_work.h> > > +#include <linux/preempt.h> > > > > #include <asm/ptrace.h> > > > > +#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. No, it just count the missed. I'm considering to expose it via new `wprobe_profile`. Thanks, -- Masami Hiramatsu (Google) <[email protected]>
