Re: [PATCH v3 07/11] perf: Add breakpoint information to siginfo on SIGTRAP

On Wed, 24 Mar 2021 at 15:01, Peter Zijlstra peterz@infradead.org wrote:

One last try, I'll leave it alone now, I promise :-)

This looks like it does what you suggested, thanks! :-)

I'll still need to think about it, because of the potential problem with modify-signal-races and what the user's synchronization story would look like then.

--- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -778,6 +778,9 @@ struct perf_event { void *security; #endif struct list_head sb_list;

•   unsigned long                   si_uattr;
  

•   unsigned long                   si_data;
  

#endif /* CONFIG_PERF_EVENTS */ };

--- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -5652,13 +5652,17 @@ static long _perf_ioctl(struct perf_even return perf_event_query_prog_array(event, (void __user *)arg);

    case PERF_EVENT_IOC_MODIFY_ATTRIBUTES: {

•           struct perf_event_attr __user *uattr;
            struct perf_event_attr new_attr;
  

•           int err = perf_copy_attr((struct perf_event_attr __user *)arg,
  

•                                    &new_attr);
  

•           int err;
  
  

•           uattr = (struct perf_event_attr __user *)arg;
  

•           err = perf_copy_attr(uattr, &new_attr);
            if (err)
                    return err;
  
  

•           event->si_uattr = (unsigned long)uattr;
  

•           return perf_event_modify_attr(event,  &new_attr);
    }
    default:
  

@@ -6399,7 +6403,12 @@ static void perf_sigtrap(struct perf_eve clear_siginfo(&info); info.si_signo = SIGTRAP; info.si_code = TRAP_PERF;

•   info.si_errno = event->attr.type;
  

•   info.si_addr = (void *)event->si_data;
  

•   info.si_perf = event->si_uattr;
  

•   if (event->parent)
  

•           info.si_perf = event->parent->si_uattr;
  

•   force_sig_info(&info);
  

}

@@ -6414,8 +6423,8 @@ static void perf_pending_event_disable(s WRITE_ONCE(event->pending_disable, -1);

            if (event->attr.sigtrap) {

•                   atomic_set(&event->event_limit, 1); /* rearm event */
                    perf_sigtrap(event);
  

•                   atomic_set_release(&event->event_limit, 1); /* rearm event */
                    return;
            }
  
  

@@ -9121,6 +9130,7 @@ static int __perf_event_overflow(struct if (events && atomic_dec_and_test(&event->event_limit)) { ret = 1; event->pending_kill = POLL_HUP;

•           event->si_data = data->addr;
  
            perf_event_disable_inatomic(event);
    }
  

@@ -12011,6 +12021,8 @@ SYSCALL_DEFINE5(perf_event_open, goto err_task; }

•   event->si_uattr = (unsigned long)attr_uptr;
  

•   if (is_sampling_event(event)) {
            if (event->pmu->capabilities & PERF_PMU_CAP_NO_INTERRUPT) {
                    err = -EOPNOTSUPP;