1 // Test program which explores whether mmap's ofs parameter
2 // is 64-bit, and whether it needs to be shifted << PAGE_SHIFT.
3 // Apparently it is 64-bit and isn't shifted.
4 //
5 // Build: x86_64-gcc -static -Wall -ox32_mmap x32_mmap.c
6 // Typical output:
7 // 7f9390696000-7f93906a6000 r--s 12345670000 08:06 2224545 /etc/passwd
8 // ^^^^^^^^^^^
9 #define _GNU_SOURCE
10 #include <sys/types.h>
11 #include <stdlib.h>
12 #include <unistd.h>
13 #include <errno.h>
14 #include <sys/mman.h>
15 #include <sys/stat.h>
16 #include <fcntl.h>
17 #include <stdio.h>
18 #include <sys/syscall.h>
19 // Ensure we are compiling to 64 bits
20 struct bug { int t[sizeof(long) > 4 ? 1 : -1]; };
main(int argc,char ** argv)21 int main(int argc, char **argv)
22 {
23 long ofs = 0x12345670000; // fails if not page-aligned
24 errno = 0;
25 close(0);
26 if (open("/etc/passwd", O_RDONLY))
27 return 1;
28 long r = syscall(
29 (long) (__NR_mmap | 0x40000000), // make x32 call
30 (long) (0), // start
31 (long) (0x10000), // len
32 (long) (PROT_READ), // prot
33 (long) (MAP_SHARED), // flags
34 (long) (0), // fd
35 (long) (ofs) // ofs
36 );
37 printf("ret:0x%lx errno:%m\n", r);
38
39 char buf[16*1024];
40 sprintf(buf, "/proc/%d/maps", getpid());
41 int fd = open(buf, O_RDONLY);
42 if (fd > 0) {
43 int sz = read(fd, buf, sizeof(buf));
44 if (sz > 0)
45 write(1, buf, sz);
46 }
47
48 return 0;
49 }
50