examples/C/getpid-asm.c

   1 /*
   2  * Calls getpid() by hand (linux-only probably)
   3  *
   4  * 1- Store the system call number in %eax
   5  * 2- Executes int 0x80
   6  * 3- Store the return code in 'ret'
   7  *
   8  * Luiz Fernando N. Capitulino <lcapitulino@mandriva.com.br>
   9  */
  10
  11 #include <stdio.h>
  12 #include <unistd.h>
  13
  14 int main(void)
  15 {
  16
  17         int ret, num;
  18
  19         num = 20; /* gerpid()'s number */
  20
  21         asm("movl %1, %%eax\n\t"
  22             "int $0x80\n\t"
  23             "movl %%eax, %0"
  24             : "=r" (ret)
  25             : "r" (num)
  26             : "%eax");
  27
  28         printf("PID: %d\n", ret);
  29         return 0;
  30 }