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]; }; 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
