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

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Message-ID: <YFtF8tEPHrXnw7cX@hirez.programming.kicks-ass.net>
Date:   Wed, 24 Mar 2021 15:00:18 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Marco Elver <elver@...gle.com>
Cc:     alexander.shishkin@...ux.intel.com, acme@...nel.org,
        mingo@...hat.com, jolsa@...hat.com, mark.rutland@....com,
        namhyung@...nel.org, tglx@...utronix.de, glider@...gle.com,
        viro@...iv.linux.org.uk, arnd@...db.de, christian@...uner.io,
        dvyukov@...gle.com, jannh@...gle.com, axboe@...nel.dk,
        mascasa@...gle.com, pcc@...gle.com, irogers@...gle.com,
        kasan-dev@...glegroups.com, linux-arch@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        x86@...nel.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH v3 07/11] perf: Add breakpoint information to siginfo on
 SIGTRAP



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

--- 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;