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// SPDX-License-Identifier: GPL-2.0
/*
* Test for perf events with SIGTRAP across all threads.
*
* Copyright (C) 2021, Google LLC.
*/
#define _GNU_SOURCE
/* We need the latest siginfo from the kernel repo. */
#include <sys/types.h>
#include <asm/siginfo.h>
#define __have_siginfo_t 1
#define __have_sigval_t 1
#define __have_sigevent_t 1
#define __siginfo_t_defined
#define __sigval_t_defined
#define __sigevent_t_defined
#define _BITS_SIGINFO_CONSTS_H 1
#define _BITS_SIGEVENT_CONSTS_H 1
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <linux/hw_breakpoint.h>
#include <linux/perf_event.h>
#include <pthread.h>
#include <signal.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;
/* Unique value to check si_perf_data is correctly set from perf_event_attr::sig_data. */
#define TEST_SIG_DATA(addr, id) (~(unsigned long)(addr) + id)
static struct perf_event_attr make_event_attr(bool enabled, volatile void *addr,
unsigned long id)
{
struct perf_event_attr attr = {
.type = PERF_TYPE_BREAKPOINT,
.size = sizeof(attr),
.sample_period = 1,
.disabled = !enabled,
.bp_addr = (unsigned 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. */
.sig_data = TEST_SIG_DATA(addr, id),
.exclude_kernel = 1, /* To allow */
.exclude_hv = 1, /* running as !root */
};
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 */
if (iter >= 0) {
for (i = 0; i < iter - 1; i++) {
__atomic_fetch_add(&ctx.tids_want_signal, tid, __ATOMIC_RELAXED);
ctx.iterate_on = iter; /* idempotent write */
}
} else {
while (ctx.iterate_on);
}
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, 0);
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_perf_type, PERF_TYPE_BREAKPOINT);
EXPECT_EQ(ctx.first_siginfo.si_perf_data, TEST_SIG_DATA(&ctx.iterate_on, 0));
/* 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, 42);
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_perf_type, PERF_TYPE_BREAKPOINT);
EXPECT_EQ(ctx.first_siginfo.si_perf_data, TEST_SIG_DATA(&ctx.iterate_on, 42));
/* 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_perf_type, PERF_TYPE_BREAKPOINT);
EXPECT_EQ(ctx.first_siginfo.si_perf_data, TEST_SIG_DATA(&ctx.iterate_on, 0));
}
TEST_F(sigtrap_threads, signal_stress_with_disable)
{
const int target_count = NUM_THREADS * 3000;
int i;
ctx.iterate_on = -1;
EXPECT_EQ(ioctl(self->fd, PERF_EVENT_IOC_ENABLE, 0), 0);
pthread_barrier_wait(&self->barrier);
while (__atomic_load_n(&ctx.signal_count, __ATOMIC_RELAXED) < target_count) {
EXPECT_EQ(ioctl(self->fd, PERF_EVENT_IOC_DISABLE, 0), 0);
EXPECT_EQ(ioctl(self->fd, PERF_EVENT_IOC_ENABLE, 0), 0);
}
ctx.iterate_on = 0;
for (i = 0; i < NUM_THREADS; i++)
ASSERT_EQ(pthread_join(self->threads[i], NULL), 0);
EXPECT_EQ(ioctl(self->fd, PERF_EVENT_IOC_DISABLE, 0), 0);
EXPECT_EQ(ctx.first_siginfo.si_addr, &ctx.iterate_on);
EXPECT_EQ(ctx.first_siginfo.si_perf_type, PERF_TYPE_BREAKPOINT);
EXPECT_EQ(ctx.first_siginfo.si_perf_data, TEST_SIG_DATA(&ctx.iterate_on, 0));
}
TEST_HARNESS_MAIN
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