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

On Wed, Mar 24, 2021 at 02:21:37PM +0100, Peter Zijlstra wrote:

--- 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->siginfo.si_perf = (unsigned long)uattr;
  

Oh bugger; that wants updating for all children too..

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

@@ -12011,6 +12010,11 @@ SYSCALL_DEFINE5(perf_event_open, goto err_task; }

• clear_siginfo(&event->siginfo);
• event->siginfo.si_signo = SIGTRAP;
• event->siginfo.si_code = TRAP_PERF;
• event->siginfo.si_perf = (unsigned long)attr_uptr;

And inherit_event() / perf_event_alloc() want to copy/propagate that.

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