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 #include <unistd.h>
17 #include <sys/syscall.h>
18 #include <sys/types.h>
19 #include <sys/stat.h>
20 #include <fcntl.h>
21 #include <errno.h>
22 #include <string.h>
23 #include <stdio.h>
24 
sys_read(int fd,void * buf,size_t len)25 static inline ssize_t sys_read(int fd, void *buf, size_t len)
26 {
27 	return syscall(SYS_read, fd, buf, len);
28 }
29 
main(void)30 int main(void)
31 {
32 	char buf1[64];
33 	char buf2[64];
34 	int fd;
35 	ssize_t rv;
36 
37 	fd = open("/proc/self/syscall", O_RDONLY);
38 	if (fd == -1) {
39 		if (errno == ENOENT)
40 			return 4;
41 		return 1;
42 	}
43 
44 	/* Do direct system call as libc can wrap anything. */
45 	snprintf(buf1, sizeof(buf1), "%ld 0x%lx 0x%lx 0x%lx",
46 		 (long)SYS_read, (long)fd, (long)buf2, (long)sizeof(buf2));
47 
48 	memset(buf2, 0, sizeof(buf2));
49 	rv = sys_read(fd, buf2, sizeof(buf2));
50 	if (rv < 0)
51 		return 1;
52 	if (rv < strlen(buf1))
53 		return 1;
54 	if (strncmp(buf1, buf2, strlen(buf1)) != 0)
55 		return 1;
56 
57 	return 0;
58 }
59