// 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>
#include <util/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 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(btf, 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(btf, 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/e368f2c848d77fbc8d259f44e2055fe469c219cf.camel@gmx.de/\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);