[PATCH RFC 4/4] perf/core: Add breakpoint information to siginfo on SIGTRAP

From: Marco Elver <elver@google.com>
To: elver@google.com, peterz@infradead.org,
	alexander.shishkin@linux.intel.com, acme@kernel.org,
	mingo@redhat.com, jolsa@redhat.com, mark.rutland@arm.com,
	namhyung@kernel.org, tglx@linutronix.de
Cc: glider@google.com, viro@zeniv.linux.org.uk, arnd@arndb.de,
	christian@brauner.io, dvyukov@google.com, jannh@google.com,
	axboe@kernel.dk, mascasa@google.com, pcc@google.com,
	irogers@google.com, kasan-dev@googlegroups.com,
	linux-arch@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-m68k@lists.linux-m68k.org,
	x86@kernel.org
Subject: [PATCH RFC 4/4] perf/core: Add breakpoint information to siginfo on SIGTRAP
Date: Tue, 23 Feb 2021 15:34:26 +0100	[thread overview]
Message-ID: <20210223143426.2412737-5-elver@google.com> (raw)
In-Reply-To: <20210223143426.2412737-1-elver@google.com>

Encode information from breakpoint attributes into siginfo_t, which
helps disambiguate which breakpoint fired.

Note, providing the event fd may be unreliable, since the event may have
been modified (via PERF_EVENT_IOC_MODIFY_ATTRIBUTES) between the event
triggering and the signal being delivered to user space.

Signed-off-by: Marco Elver <elver@google.com>
---
 kernel/events/core.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 8718763045fd..d7908322d796 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -6296,6 +6296,17 @@ static void perf_sigtrap(struct perf_event *event)
 	info.si_signo = SIGTRAP;
 	info.si_code = TRAP_PERF;
 	info.si_errno = event->attr.type;
+
+	switch (event->attr.type) {
+	case PERF_TYPE_BREAKPOINT:
+		info.si_addr = (void *)(unsigned long)event->attr.bp_addr;
+		info.si_perf = (event->attr.bp_len << 16) | (u64)event->attr.bp_type;
+		break;
+	default:
+		/* No additional info set. */
+		break;
+	}
+
 	force_sig_info(&info);
 }
 
-- 
2.30.0.617.g56c4b15f3c-goog

