new file mode 100644
@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0-only
+sigtrap_threads
new file mode 100644
@@ -0,0 +1,6 @@
+# SPDX-License-Identifier: GPL-2.0
+CFLAGS += -Wl,-no-as-needed -Wall -I../../../../usr/include
+LDFLAGS += -lpthread
+
+TEST_GEN_PROGS := sigtrap_threads
+include ../lib.mk
new file mode 100644
@@ -0,0 +1 @@
+CONFIG_PERF_EVENTS=y
new file mode 100644
@@ -0,0 +1 @@
+timeout=120
new file mode 100644
@@ -0,0 +1,202 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Test for perf events with SIGTRAP across all threads.
+ *
+ * Copyright (C) 2021, Google LLC.
+ */
+
+#define _GNU_SOURCE
+#include <sys/types.h>
+
+/* We need the latest siginfo from the kernel repo. */
+#include <asm/siginfo.h>
+#define __have_siginfo_t 1
+#define __have_sigval_t 1
+#define __have_sigevent_t 1
+
+#include <linux/hw_breakpoint.h>
+#include <linux/perf_event.h>
+#include <pthread.h>
+#include <signal.h>
+#include <stdatomic.h>
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <sys/ioctl.h>
+#include <sys/syscall.h>
+#include <unistd.h>
+
+#include "../kselftest_harness.h"
+
+#define NUM_THREADS 5
+
+/* Data shared between test body, threads, and signal handler. */
+static struct {
+ int tids_want_signal; /* Which threads still want a signal. */
+ int signal_count; /* Sanity check number of signals received. */
+ volatile int iterate_on; /* Variable to set breakpoint on. */
+ siginfo_t first_siginfo; /* First observed siginfo_t. */
+} ctx;
+
+static struct perf_event_attr make_event_attr(bool enabled, volatile void *addr)
+{
+ struct perf_event_attr attr = {
+ .type = PERF_TYPE_BREAKPOINT,
+ .size = sizeof(attr),
+ .sample_period = 1,
+ .disabled = !enabled,
+ .bp_addr = (long)addr,
+ .bp_type = HW_BREAKPOINT_RW,
+ .bp_len = HW_BREAKPOINT_LEN_1,
+ .inherit = 1, /* Children inherit events ... */
+ .inherit_thread = 1, /* ... but only cloned with CLONE_THREAD. */
+ .remove_on_exec = 1, /* Required by sigtrap. */
+ .sigtrap = 1, /* Request synchronous SIGTRAP on event. */
+ };
+ return attr;
+}
+
+static void sigtrap_handler(int signum, siginfo_t *info, void *ucontext)
+{
+ if (info->si_code != TRAP_PERF) {
+ fprintf(stderr, "%s: unexpected si_code %d\n", __func__, info->si_code);
+ return;
+ }
+
+ /*
+ * The data in siginfo_t we're interested in should all be the same
+ * across threads.
+ */
+ if (!__atomic_fetch_add(&ctx.signal_count, 1, __ATOMIC_RELAXED))
+ ctx.first_siginfo = *info;
+ __atomic_fetch_sub(&ctx.tids_want_signal, syscall(__NR_gettid), __ATOMIC_RELAXED);
+}
+
+static void *test_thread(void *arg)
+{
+ pthread_barrier_t *barrier = (pthread_barrier_t *)arg;
+ pid_t tid = syscall(__NR_gettid);
+ int iter;
+ int i;
+
+ pthread_barrier_wait(barrier);
+
+ __atomic_fetch_add(&ctx.tids_want_signal, tid, __ATOMIC_RELAXED);
+ iter = ctx.iterate_on; /* read */
+ for (i = 0; i < iter - 1; i++) {
+ __atomic_fetch_add(&ctx.tids_want_signal, tid, __ATOMIC_RELAXED);
+ ctx.iterate_on = iter; /* idempotent write */
+ }
+
+ return NULL;
+}
+
+FIXTURE(sigtrap_threads)
+{
+ struct sigaction oldact;
+ pthread_t threads[NUM_THREADS];
+ pthread_barrier_t barrier;
+ int fd;
+};
+
+FIXTURE_SETUP(sigtrap_threads)
+{
+ struct perf_event_attr attr = make_event_attr(false, &ctx.iterate_on);
+ struct sigaction action = {};
+ int i;
+
+ memset(&ctx, 0, sizeof(ctx));
+
+ /* Initialize sigtrap handler. */
+ action.sa_flags = SA_SIGINFO | SA_NODEFER;
+ action.sa_sigaction = sigtrap_handler;
+ sigemptyset(&action.sa_mask);
+ ASSERT_EQ(sigaction(SIGTRAP, &action, &self->oldact), 0);
+
+ /* Initialize perf event. */
+ self->fd = syscall(__NR_perf_event_open, &attr, 0, -1, -1, PERF_FLAG_FD_CLOEXEC);
+ ASSERT_NE(self->fd, -1);
+
+ /* Spawn threads inheriting perf event. */
+ pthread_barrier_init(&self->barrier, NULL, NUM_THREADS + 1);
+ for (i = 0; i < NUM_THREADS; i++)
+ ASSERT_EQ(pthread_create(&self->threads[i], NULL, test_thread, &self->barrier), 0);
+}
+
+FIXTURE_TEARDOWN(sigtrap_threads)
+{
+ pthread_barrier_destroy(&self->barrier);
+ close(self->fd);
+ sigaction(SIGTRAP, &self->oldact, NULL);
+}
+
+static void run_test_threads(struct __test_metadata *_metadata,
+ FIXTURE_DATA(sigtrap_threads) *self)
+{
+ int i;
+
+ pthread_barrier_wait(&self->barrier);
+ for (i = 0; i < NUM_THREADS; i++)
+ ASSERT_EQ(pthread_join(self->threads[i], NULL), 0);
+}
+
+TEST_F(sigtrap_threads, remain_disabled)
+{
+ run_test_threads(_metadata, self);
+ EXPECT_EQ(ctx.signal_count, 0);
+ EXPECT_NE(ctx.tids_want_signal, 0);
+}
+
+TEST_F(sigtrap_threads, enable_event)
+{
+ EXPECT_EQ(ioctl(self->fd, PERF_EVENT_IOC_ENABLE, 0), 0);
+ run_test_threads(_metadata, self);
+
+ EXPECT_EQ(ctx.signal_count, NUM_THREADS);
+ EXPECT_EQ(ctx.tids_want_signal, 0);
+ EXPECT_EQ(ctx.first_siginfo.si_addr, &ctx.iterate_on);
+ EXPECT_EQ(ctx.first_siginfo.si_errno, PERF_TYPE_BREAKPOINT);
+ EXPECT_EQ(ctx.first_siginfo.si_perf, (HW_BREAKPOINT_LEN_1 << 16) | HW_BREAKPOINT_RW);
+
+ /* Check enabled for parent. */
+ ctx.iterate_on = 0;
+ EXPECT_EQ(ctx.signal_count, NUM_THREADS + 1);
+}
+
+/* Test that modification propagates to all inherited events. */
+TEST_F(sigtrap_threads, modify_and_enable_event)
+{
+ struct perf_event_attr new_attr = make_event_attr(true, &ctx.iterate_on);
+
+ EXPECT_EQ(ioctl(self->fd, PERF_EVENT_IOC_MODIFY_ATTRIBUTES, &new_attr), 0);
+ run_test_threads(_metadata, self);
+
+ EXPECT_EQ(ctx.signal_count, NUM_THREADS);
+ EXPECT_EQ(ctx.tids_want_signal, 0);
+ EXPECT_EQ(ctx.first_siginfo.si_addr, &ctx.iterate_on);
+ EXPECT_EQ(ctx.first_siginfo.si_errno, PERF_TYPE_BREAKPOINT);
+ EXPECT_EQ(ctx.first_siginfo.si_perf, (HW_BREAKPOINT_LEN_1 << 16) | HW_BREAKPOINT_RW);
+
+ /* Check enabled for parent. */
+ ctx.iterate_on = 0;
+ EXPECT_EQ(ctx.signal_count, NUM_THREADS + 1);
+}
+
+/* Stress test event + signal handling. */
+TEST_F(sigtrap_threads, signal_stress)
+{
+ ctx.iterate_on = 3000;
+
+ EXPECT_EQ(ioctl(self->fd, PERF_EVENT_IOC_ENABLE, 0), 0);
+ run_test_threads(_metadata, self);
+ EXPECT_EQ(ioctl(self->fd, PERF_EVENT_IOC_DISABLE, 0), 0);
+
+ EXPECT_EQ(ctx.signal_count, NUM_THREADS * ctx.iterate_on);
+ EXPECT_EQ(ctx.tids_want_signal, 0);
+ EXPECT_EQ(ctx.first_siginfo.si_addr, &ctx.iterate_on);
+ EXPECT_EQ(ctx.first_siginfo.si_errno, PERF_TYPE_BREAKPOINT);
+ EXPECT_EQ(ctx.first_siginfo.si_perf, (HW_BREAKPOINT_LEN_1 << 16) | HW_BREAKPOINT_RW);
+}
+
+TEST_HARNESS_MAIN
Add a kselftest for testing process-wide perf events with synchronous SIGTRAP on events (using breakpoints). In particular, we want to test that changes to the event propagate to all children, and the SIGTRAPs are in fact synchronously sent to the thread where the event occurred. Signed-off-by: Marco Elver <elver@google.com> --- v2: * Patch added to series. --- .../testing/selftests/perf_events/.gitignore | 2 + tools/testing/selftests/perf_events/Makefile | 6 + tools/testing/selftests/perf_events/config | 1 + tools/testing/selftests/perf_events/settings | 1 + .../selftests/perf_events/sigtrap_threads.c | 202 ++++++++++++++++++ 5 files changed, 212 insertions(+) create mode 100644 tools/testing/selftests/perf_events/.gitignore create mode 100644 tools/testing/selftests/perf_events/Makefile create mode 100644 tools/testing/selftests/perf_events/config create mode 100644 tools/testing/selftests/perf_events/settings create mode 100644 tools/testing/selftests/perf_events/sigtrap_threads.c