39 lines
914 B
C
39 lines
914 B
C
|
#include <inc/x86.h>
|
||
|
|
#include <inc/lib.h>
|
||
|
|
|
||
|
|
char buf[512], buf2[512];
|
||
|
|
|
||
|
|
void
|
||
|
|
umain(int argc, char **argv)
|
||
|
|
{
|
||
|
|
int fd, r, n, n2;
|
||
|
|
|
||
|
|
if ((fd = open("motd", O_RDONLY)) < 0)
|
||
|
|
panic("open motd: %e", fd);
|
||
|
|
seek(fd, 0);
|
||
|
|
if ((n = readn(fd, buf, sizeof buf)) <= 0)
|
||
|
|
panic("readn: %e", n);
|
||
|
|
|
||
|
|
if ((r = fork()) < 0)
|
||
|
|
panic("fork: %e", r);
|
||
|
|
if (r == 0) {
|
||
|
|
seek(fd, 0);
|
||
|
|
cprintf("going to read in child (might page fault if your sharing is buggy)\n");
|
||
|
|
if ((n2 = readn(fd, buf2, sizeof buf2)) != n)
|
||
|
|
panic("read in parent got %d, read in child got %d", n, n2);
|
||
|
|
if (memcmp(buf, buf2, n) != 0)
|
||
|
|
panic("read in parent got different bytes from read in child");
|
||
|
|
cprintf("read in child succeeded\n");
|
||
|
|
seek(fd, 0);
|
||
|
|
close(fd);
|
||
|
|
exit();
|
||
|
|
}
|
||
|
|
wait(r);
|
||
|
|
if ((n2 = readn(fd, buf2, sizeof buf2)) != n)
|
||
|
|
panic("read in parent got %d, then got %d", n, n2);
|
||
|
|
cprintf("read in parent succeeded\n");
|
||
|
|
close(fd);
|
||
|
|
|
||
|
|
breakpoint();
|
||
|
|
}
|