1/*
 2 * Copyright © 2018 Alexey Dobriyan <adobriyan@gmail.com>
 3 *
 4 * Permission to use, copy, modify, and distribute this software for any
 5 * purpose with or without fee is hereby granted, provided that the above
 6 * copyright notice and this permission notice appear in all copies.
 7 *
 8 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 9 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
10 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
11 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
12 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
13 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
14 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
15 */
16#define _GNU_SOURCE
17#include <unistd.h>
18#include <sys/syscall.h>
19#include <sys/types.h>
20#include <sys/stat.h>
21#include <fcntl.h>
22#include <errno.h>
23#include <string.h>
24#include <stdio.h>
25
26static inline ssize_t sys_read(int fd, void *buf, size_t len)
27{
28	return syscall(SYS_read, fd, buf, len);
29}
30
31int main(void)
32{
33	char buf1[64];
34	char buf2[64];
35	int fd;
36	ssize_t rv;
37
38	fd = open("/proc/self/syscall", O_RDONLY);
39	if (fd == -1) {
40		if (errno == ENOENT)
41			return 4;
42		return 1;
43	}
44
45	/* Do direct system call as libc can wrap anything. */
46	snprintf(buf1, sizeof(buf1), "%ld 0x%lx 0x%lx 0x%lx",
47		 (long)SYS_read, (long)fd, (long)buf2, (long)sizeof(buf2));
48
49	memset(buf2, 0, sizeof(buf2));
50	rv = sys_read(fd, buf2, sizeof(buf2));
51	if (rv < 0)
52		return 1;
53	if (rv < strlen(buf1))
54		return 1;
55	if (strncmp(buf1, buf2, strlen(buf1)) != 0)
56		return 1;
57
58	return 0;
59}