/*
 * Copyright (C) 2021 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#if !defined _GNU_SOURCE
#define _GNU_SOURCE
#endif

#include <err.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/uio.h>
#include <sys/wait.h>
#include <unistd.h>

#include "../includes/common.h"

#define SYSCHK(x)                                               \
    ({                                                          \
        typeof(x) __res = (x);                                  \
        if (__res == (typeof(x)) - 1) err(1, "SYSCHK(" #x ")"); \
        __res;                                                  \
    })

static char *data;

static int child_fn(void) {
    int pipe_fds[2];
    SYSCHK(pipe(pipe_fds));
    struct iovec iov = {.iov_base = data, .iov_len = 0x1000};
    SYSCHK(vmsplice(pipe_fds[1], &iov, 1, 0));
    SYSCHK(munmap(data, 0x1000));
    sleep(2);
    char buf[0x1000];
    SYSCHK(read(pipe_fds[0], buf, 0x1000));
    printf("read string from child: %s\n", buf);

    // check if buf has been altered by parent process
    if (strcmp("BORING DATA", buf) == 0) {
        return EXIT_SUCCESS;
    }
    if (strcmp("THIS IS SECRET", buf) == 0) {
        return EXIT_VULNERABLE;
    }
    return EXIT_FAILURE;
}

int main(void) {
    if (posix_memalign((void **)&data, 0x1000, 0x1000)) errx(1, "posix_memalign()");
    strcpy(data, "BORING DATA");

    pid_t child = SYSCHK(fork());
    if (child == 0) {
        exit(child_fn());
    }

    sleep(1);
    strcpy(data, "THIS IS SECRET");

    int status;
    SYSCHK(waitpid(child, &status, 0));
    printf("child WEXITSTATUS(status) => %d\n", WEXITSTATUS(status));
    return WEXITSTATUS(status);
}