// SPDX-License-Identifier: GPL-2.0
/*
 * Test for remove_on_exec.
 *
 * 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/perf_event.h>
#include <pthread.h>
#include <signal.h>
#include <sys/ioctl.h>
#include <sys/syscall.h>
#include <unistd.h>

#include "kselftest_harness.h"

static volatile int signal_count;

static struct perf_event_attr make_event_attr(void)
{
        struct perf_event_attr attr = {
                .type           = PERF_TYPE_HARDWARE,
                .size           = sizeof(attr),
                .config         = PERF_COUNT_HW_INSTRUCTIONS,
                .sample_period  = 1000,
                .exclude_kernel = 1,
                .exclude_hv     = 1,
                .disabled       = 1,
                .inherit        = 1,
                /*
                 * Children normally retain their inherited event on exec; with
                 * remove_on_exec, we'll remove their event, but the parent and
                 * any other non-exec'd children will keep their events.
                 */
                .remove_on_exec = 1,
                .sigtrap        = 1,
        };
        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;
        }

        signal_count++;
}

FIXTURE(remove_on_exec)
{
        struct sigaction oldact;
        int fd;
};

FIXTURE_SETUP(remove_on_exec)
{
        struct perf_event_attr attr = make_event_attr();
        struct sigaction action = {};

        signal_count = 0;

        /* 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);
}

FIXTURE_TEARDOWN(remove_on_exec)
{
        close(self->fd);
        sigaction(SIGTRAP, &self->oldact, NULL);
}

/* Verify event propagates to fork'd child. */
TEST_F(remove_on_exec, fork_only)
{
        int status;
        pid_t pid = fork();

        if (pid == 0) {
                ASSERT_EQ(signal_count, 0);
                ASSERT_EQ(ioctl(self->fd, PERF_EVENT_IOC_ENABLE, 0), 0);
                while (!signal_count);
                _exit(42);
        }

        while (!signal_count); /* Child enables event. */
        EXPECT_EQ(waitpid(pid, &status, 0), pid);
        EXPECT_EQ(WEXITSTATUS(status), 42);
}

/*
 * Verify that event does _not_ propagate to fork+exec'd child; event enabled
 * after fork+exec.
 */
TEST_F(remove_on_exec, fork_exec_then_enable)
{
        pid_t pid_exec, pid_only_fork;
        int pipefd[2];
        int tmp;

        /*
         * Non-exec child, to ensure exec does not affect inherited events of
         * other children.
         */
        pid_only_fork = fork();
        if (pid_only_fork == 0) {
                /* Block until parent enables event. */
                while (!signal_count);
                _exit(42);
        }

        ASSERT_NE(pipe(pipefd), -1);
        pid_exec = fork();
        if (pid_exec == 0) {
                ASSERT_NE(dup2(pipefd[1], STDOUT_FILENO), -1);
                close(pipefd[0]);
                execl("/proc/self/exe", "exec_child", NULL);
                _exit((perror("exec failed"), 1));
        }
        close(pipefd[1]);

        ASSERT_EQ(waitpid(pid_exec, &tmp, WNOHANG), 0); /* Child is running. */
        /* Wait for exec'd child to start spinning. */
        EXPECT_EQ(read(pipefd[0], &tmp, sizeof(int)), sizeof(int));
        EXPECT_EQ(tmp, 42);
        close(pipefd[0]);
        /* Now we can enable the event, knowing the child is doing work. */
        EXPECT_EQ(ioctl(self->fd, PERF_EVENT_IOC_ENABLE, 0), 0);
        /* If the event propagated to the exec'd child, it will exit normally... */
        usleep(100000); /* ... give time for event to trigger (in case of bug). */
        EXPECT_EQ(waitpid(pid_exec, &tmp, WNOHANG), 0); /* Should still be running. */
        EXPECT_EQ(kill(pid_exec, SIGKILL), 0);

        /* Verify removal from child did not affect this task's event. */
        tmp = signal_count;
        while (signal_count == tmp); /* Should not hang! */
        /* Nor should it have affected the first child. */
        EXPECT_EQ(waitpid(pid_only_fork, &tmp, 0), pid_only_fork);
        EXPECT_EQ(WEXITSTATUS(tmp), 42);
}

/*
 * Verify that event does _not_ propagate to fork+exec'd child; event enabled
 * before fork+exec.
 */
TEST_F(remove_on_exec, enable_then_fork_exec)
{
        pid_t pid_exec;
        int tmp;

        EXPECT_EQ(ioctl(self->fd, PERF_EVENT_IOC_ENABLE, 0), 0);

        pid_exec = fork();
        if (pid_exec == 0) {
                execl("/proc/self/exe", "exec_child", NULL);
                _exit((perror("exec failed"), 1));
        }

        /*
         * The child may exit abnormally at any time if the event propagated and
         * a SIGTRAP is sent before the handler was set up.
         */
        usleep(100000); /* ... give time for event to trigger (in case of bug). */
        EXPECT_EQ(waitpid(pid_exec, &tmp, WNOHANG), 0); /* Should still be running. */
        EXPECT_EQ(kill(pid_exec, SIGKILL), 0);

        /* Verify removal from child did not affect this task's event. */
        tmp = signal_count;
        while (signal_count == tmp); /* Should not hang! */
}

TEST_F(remove_on_exec, exec_stress)
{
        pid_t pids[30];
        int i, tmp;

        for (i = 0; i < sizeof(pids) / sizeof(pids[0]); i++) {
                pids[i] = fork();
                if (pids[i] == 0) {
                        execl("/proc/self/exe", "exec_child", NULL);
                        _exit((perror("exec failed"), 1));
                }

                /* Some forked with event disabled, rest with enabled. */
                if (i > 10)
                        EXPECT_EQ(ioctl(self->fd, PERF_EVENT_IOC_ENABLE, 0), 0);
        }

        usleep(100000); /* ... give time for event to trigger (in case of bug). */

        for (i = 0; i < sizeof(pids) / sizeof(pids[0]); i++) {
                /* All children should still be running. */
                EXPECT_EQ(waitpid(pids[i], &tmp, WNOHANG), 0);
                EXPECT_EQ(kill(pids[i], SIGKILL), 0);
        }

        /* Verify event is still alive. */
        tmp = signal_count;
        while (signal_count == tmp);
}

/* For exec'd child. */
static void exec_child(void)
{
        struct sigaction action = {};
        const int val = 42;

        /* Set up sigtrap handler in case we erroneously receive a trap. */
        action.sa_flags = SA_SIGINFO | SA_NODEFER;
        action.sa_sigaction = sigtrap_handler;
        sigemptyset(&action.sa_mask);
        if (sigaction(SIGTRAP, &action, NULL))
                _exit((perror("sigaction failed"), 1));

        /* Signal parent that we're starting to spin. */
        if (write(STDOUT_FILENO, &val, sizeof(int)) == -1)
                _exit((perror("write failed"), 1));

        /* Should hang here until killed. */
        while (!signal_count);
}

#define main test_main
TEST_HARNESS_MAIN
#undef main
int main(int argc, char *argv[])
{
        if (!strcmp(argv[0], "exec_child")) {
                exec_child();
                return 1;
        }

        return test_main(argc, argv);
}