minix/tests/test62.c

   1 /* FPU state corruption test. This used to be able to crash the kernel. */
   2 #include <stdlib.h>
   3 #include <stdio.h>
   4 #include <string.h>
   5 #include <signal.h>
   6 #include <sys/wait.h>
   7 #include <machine/fpu.h>
   8
   9 int max_error = 1;
  10 #include "common.h"
  11
  12
  13 double state = 2.0;
  14 static int count;
  15
  16 static void use_fpu(int n)
  17 {
  18   state += (double) n * 0.5;
  19 }
  20
  21 static void crashed(int sig)
  22 {
  23   exit(EXIT_SUCCESS);
  24 }
  25
  26 static void handler(int sig, int code, struct sigcontext *sc)
  27 {
  28   memset(&sc->sc_fpu_state, count, sizeof(sc->sc_fpu_state));
  29 }
  30
  31 int main(void)
  32 {
  33   int status;
  34
  35   start(62);
  36   subtest = 0;
  37
  38   signal(SIGUSR1, (void (*)(int)) handler);
  39
  40   /* Initialize the FPU state. This state is inherited, too. */
  41   use_fpu(-1);
  42
  43   for (count = 0; count <= 255; count++) {
  44         switch (fork()) {
  45         case -1:
  46                 e(1);
  47
  48                 break;
  49
  50         case 0:
  51                 signal(SIGFPE, crashed);
  52
  53                 /* Load bad state into the kernel. */
  54                 if (kill(getpid(), SIGUSR1)) e(2);
  55
  56                 /* Let the kernel restore the state. */
  57                 use_fpu(count);
  58
  59                 exit(EXIT_SUCCESS);
  60
  61         default:
  62                 /* We cannot tell exactly whether what happened is correct or
  63                  * not -- certainly not in a platform-independent way. However,
  64                  * if the whole system keeps running, that's good enough.
  65                  */
  66                 (void) wait(&status);
  67         }
  68   }
  69
  70   if (state <= 1.4 || state >= 1.6) e(3);
  71
  72   quit();
  73
  74   return 0;
  75 }