pushpopseg.c revision d651d1fe2c2dae5606626445c5a189233afae43e 
1#include <stdio.h>
2#include <stdlib.h>
3
4int main(int argc, char **argv)
5{
6  unsigned long  sp1;
7  unsigned long  sp2;
8  unsigned long  sp3;
9  unsigned short fs1;
10  unsigned short fs2;
11
12  fs1 = 0x0003;
13
14  asm("movw %4, %%fs\n"
15      "movl %%esp, %0\n"
16      "pushw %%fs\n"
17      "movl %%esp, %1\n"
18      "popw %%fs\n"
19      "movl %%esp, %2\n"
20      "movw %%fs, %3\n"
21      : "=r" (sp1), "=r" (sp2), "=r" (sp3), "=r" (fs2)
22      : "r" (fs1)
23      : "ax"
24      );
25
26  printf("sp change after push = %ld\n", sp2 - sp1);
27  printf("sp change after pop = %ld\n", sp3 - sp2);
28  printf("fs after push and pop = %04x\n", fs1);
29
30  asm("movw %4, %%fs\n"
31      "movl %%esp, %0\n"
32      "pushl %%fs\n"
33      "movl %%esp, %1\n"
34      "popl %%fs\n"
35      "movl %%esp, %2\n"
36      "movw %%fs, %3\n"
37      : "=r" (sp1), "=r" (sp2), "=r" (sp3), "=r" (fs2)
38      : "r" (fs1)
39      : "ax"
40      );
41
42  printf("sp change after push = %ld\n", sp2 - sp1);
43  printf("sp change after pop = %ld\n", sp3 - sp2);
44  printf("fs after push and pop = %04x\n", fs1);
45
46  exit(0);
47}
48