// SPDX-License-Identifier: GPL-2.0
/*
* Basic test for sigtrap support.
*
* Copyright (C) 2021, Google LLC.
*/
#include <errno.h>
#include <stdint.h>
#include <stdlib.h>
#include <linux/hw_breakpoint.h>
#include <linux/string.h>
#include <pthread.h>
#include <signal.h>
#include <sys/ioctl.h>
#include <sys/syscall.h>
#include <unistd.h>
#include "cloexec.h"
#include "debug.h"
#include "event.h"
#include "tests.h"
#include "../perf-sys.h"
#define NUM_THREADS 5
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;
#define TEST_SIG_DATA (~(unsigned long)(&ctx.iterate_on))
static struct perf_event_attr make_event_attr(void)
{
struct perf_event_attr attr = {
.type = PERF_TYPE_BREAKPOINT,
.size = sizeof(attr),
.sample_period = 1,
.disabled = 1,
.bp_addr = (unsigned long)&ctx.iterate_on,
.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,
.exclude_kernel = 1, /* To allow */
.exclude_hv = 1, /* running as !root */
};
return attr;
}
#ifdef HAVE_BPF_SKEL
#include <bpf/btf.h>
static struct btf *btf;
static bool btf__available(void)
{
if (btf == NULL)
btf = btf__load_vmlinux_btf();
return btf != NULL;
}
static void btf__exit(void)
{
btf__free(btf);
btf = NULL;
}
static const struct btf_member *__btf_type__find_member_by_name(int type_id, const char *member_name)
{
const struct btf_type *t = btf__type_by_id(btf, type_id);
const struct btf_member *m;
int i;
for (i = 0, m = btf_members(t); i < btf_vlen(t); i++, m++) {
const char *current_member_name = btf__name_by_offset(btf, m->name_off);
if (!strcmp(current_member_name, member_name))
return m;
}
return NULL;
}
static bool attr_has_sigtrap(void)
{
int id;
if (!btf__available()) {
/* should be an old kernel */
return false;
}
id = btf__find_by_name_kind(btf, "perf_event_attr", BTF_KIND_STRUCT);
if (id < 0)
return false;
return __btf_type__find_member_by_name(id, "sigtrap") != NULL;
}
static bool kernel_with_sleepable_spinlocks(void)
{
const struct btf_member *member;
const struct btf_type *type;
const char *type_name;
int id;
if (!btf__available())
return false;
id = btf__find_by_name_kind(btf, "spinlock", BTF_KIND_STRUCT);
if (id < 0)
return false;
// Only RT has a "lock" member for "struct spinlock"
member = __btf_type__find_member_by_name(id, "lock");
if (member == NULL)
return false;
// But check its type as well
type = btf__type_by_id(btf, member->type);
if (!type || !btf_is_struct(type))
return false;
type_name = btf__name_by_offset(btf, type->name_off);
return type_name && !strcmp(type_name, "rt_mutex_base");
}
#else /* !HAVE_BPF_SKEL */
static bool attr_has_sigtrap(void)
{
struct perf_event_attr attr = {
.type = PERF_TYPE_SOFTWARE,
.config = PERF_COUNT_SW_DUMMY,
.size = sizeof(attr),
.remove_on_exec = 1, /* Required by sigtrap. */
.sigtrap = 1, /* Request synchronous SIGTRAP on event. */
};
int fd;
bool ret = false;
fd = sys_perf_event_open(&attr, 0, -1, -1, perf_event_open_cloexec_flag());
if (fd >= 0) {
ret = true;
close(fd);
}
return ret;
}
static bool kernel_with_sleepable_spinlocks(void)
{
return false;
}
static void btf__exit(void)
{
}
#endif /* HAVE_BPF_SKEL */
static void
sigtrap_handler(int signum __maybe_unused, siginfo_t *info, void *ucontext __maybe_unused)
{
if (!__atomic_fetch_add(&ctx.signal_count, 1, __ATOMIC_RELAXED))
ctx.first_siginfo = *info;
__atomic_fetch_sub(&ctx.tids_want_signal, syscall(SYS_gettid), __ATOMIC_RELAXED);
}
static void *test_thread(void *arg)
{
pthread_barrier_t *barrier = (pthread_barrier_t *)arg;
pid_t tid = syscall(SYS_gettid);
int i;
pthread_barrier_wait(barrier);
__atomic_fetch_add(&ctx.tids_want_signal, tid, __ATOMIC_RELAXED);
for (i = 0; i < ctx.iterate_on - 1; i++)
__atomic_fetch_add(&ctx.tids_want_signal, tid, __ATOMIC_RELAXED);
return NULL;
}
static int run_test_threads(pthread_t *threads, pthread_barrier_t *barrier)
{
int i;
pthread_barrier_wait(barrier);
for (i = 0; i < NUM_THREADS; i++)
TEST_ASSERT_EQUAL("pthread_join() failed", pthread_join(threads[i], NULL), 0);
return TEST_OK;
}
static int run_stress_test(int fd, pthread_t *threads, pthread_barrier_t *barrier)
{
int ret, expected_sigtraps;
ctx.iterate_on = 3000;
TEST_ASSERT_EQUAL("misfired signal?", ctx.signal_count, 0);
TEST_ASSERT_EQUAL("enable failed", ioctl(fd, PERF_EVENT_IOC_ENABLE, 0), 0);
ret = run_test_threads(threads, barrier);
TEST_ASSERT_EQUAL("disable failed", ioctl(fd, PERF_EVENT_IOC_DISABLE, 0), 0);
expected_sigtraps = NUM_THREADS * ctx.iterate_on;
if (ctx.signal_count < expected_sigtraps && kernel_with_sleepable_spinlocks()) {
pr_debug("Expected %d sigtraps, got %d, running on a kernel with sleepable spinlocks.\n",
expected_sigtraps, ctx.signal_count);
pr_debug("See https://lore.kernel.org/all/[email protected]/\n");
return TEST_SKIP;
} else
TEST_ASSERT_EQUAL("unexpected sigtraps", ctx.signal_count, expected_sigtraps);
TEST_ASSERT_EQUAL("missing signals or incorrectly delivered", ctx.tids_want_signal, 0);
TEST_ASSERT_VAL("unexpected si_addr", ctx.first_siginfo.si_addr == &ctx.iterate_on);
#if 0 /* FIXME: enable when libc's signal.h has si_perf_{type,data} */
TEST_ASSERT_EQUAL("unexpected si_perf_type", ctx.first_siginfo.si_perf_type,
PERF_TYPE_BREAKPOINT);
TEST_ASSERT_EQUAL("unexpected si_perf_data", ctx.first_siginfo.si_perf_data,
TEST_SIG_DATA);
#endif
return ret;
}
static int test__sigtrap(struct test_suite *test __maybe_unused, int subtest __maybe_unused)
{
struct perf_event_attr attr = make_event_attr();
struct sigaction action = {};
struct sigaction oldact;
pthread_t threads[NUM_THREADS];
pthread_barrier_t barrier;
char sbuf[STRERR_BUFSIZE];
int i, fd, ret = TEST_FAIL;
if (!BP_SIGNAL_IS_SUPPORTED) {
pr_debug("Test not supported on this architecture");
return TEST_SKIP;
}
pthread_barrier_init(&barrier, NULL, NUM_THREADS + 1);
action.sa_flags = SA_SIGINFO | SA_NODEFER;
action.sa_sigaction = sigtrap_handler;
sigemptyset(&action.sa_mask);
if (sigaction(SIGTRAP, &action, &oldact)) {
pr_debug("FAILED sigaction(): %s\n", str_error_r(errno, sbuf, sizeof(sbuf)));
goto out;
}
fd = sys_perf_event_open(&attr, 0, -1, -1, perf_event_open_cloexec_flag());
if (fd < 0) {
if (attr_has_sigtrap()) {
pr_debug("FAILED sys_perf_event_open(): %s\n",
str_error_r(errno, sbuf, sizeof(sbuf)));
} else {
pr_debug("perf_event_attr doesn't have sigtrap\n");
ret = TEST_SKIP;
}
goto out_restore_sigaction;
}
for (i = 0; i < NUM_THREADS; i++) {
if (pthread_create(&threads[i], NULL, test_thread, &barrier)) {
pr_debug("FAILED pthread_create(): %s\n", str_error_r(errno, sbuf, sizeof(sbuf)));
goto out_close_perf_event;
}
}
ret = run_stress_test(fd, threads, &barrier);
out_close_perf_event:
close(fd);
out_restore_sigaction:
sigaction(SIGTRAP, &oldact, NULL);
out:
pthread_barrier_destroy(&barrier);
btf__exit();
return ret;
}
DEFINE_SUITE("Sigtrap", sigtrap);
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