user/testfdsharing.c

   1 #include <inc/lib.h>
   2
   3 char buf[512], buf2[512];
   4
   5 void
   6 umain(void)
   7 {
   8         int fd, r, n, n2;
   9
  10         if ((fd = open("motd", O_RDONLY)) < 0)
  11                 panic("open motd: %e", fd);
  12         seek(fd, 0);
  13         if ((n = readn(fd, buf, sizeof buf)) <= 0)
  14                 panic("readn: %e", n);
  15
  16         if ((r = fork()) < 0)
  17                 panic("fork: %e", r);
  18         if (r == 0) {
  19                 seek(fd, 0);
  20                 cprintf("going to read in child (might page fault if your sharing is buggy)\n");
  21                 if ((n2 = readn(fd, buf2, sizeof buf2)) != n2)
  22                         panic("read in parent got %d, read in child got %d", n, n2);
  23                 if (memcmp(buf, buf2, n) != 0)
  24                         panic("read in parent got different bytes from read in child");
  25                 cprintf("read in child succeeded\n");
  26                 seek(fd, 0);
  27                 close(fd);
  28                 exit();
  29         }
  30         wait(r);
  31         if ((n2 = readn(fd, buf2, sizeof buf2)) != n)
  32                 panic("read in parent got %d, then got %d", n, n2);
  33         cprintf("read in parent succeeded\n");
  34 }