none/tests/x86/pushpopseg.c

   1 #include <stdio.h>
   2 #include <stdlib.h>
   3
   4 int 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 }