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#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include <setjmp.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <sys/mman.h>
#include <sys/wait.h>
#include <errno.h>
#include <string.h>
/* - Checks if mapping of already closed file survives fork()
- Checks if mapping the same region of the same file twice
is done correctly.
*/
sigset_t unblock_sigsegv;
jmp_buf r;
static const char *msg;
static const char *what;
/* filler for file */
char const line[] = "y1 y1 y1 y1 y1 y1 y1 y1 y1 y1 y1 y1 y1 y1 y1 y1 y1";
void
perror_exit (const char *str)
{
printf ("%s: %s\n", str, strerror (errno));
fflush (stdout);
exit (1);
}
void
sigsegv (int unused)
{
sigprocmask (SIG_UNBLOCK, &unblock_sigsegv, 0);
if (msg)
{
char buf[132];
sprintf (buf, "%s %s\n", what, msg);
write (1, buf, strlen (buf));
msg = NULL;
}
longjmp (r, 1);
}
int
main(int argc, char **argv)
{
int fd, status;
struct stat statbuf;
volatile char c, *buf1, *buf2;
pid_t pid;
/* Create data file */
if ((fd = open("y.txt", O_RDWR | O_CREAT | O_TRUNC, 0644)) == -1)
perror_exit ("Can't create data file");
write (fd, line, sizeof(line) - 1);
close (fd);
/* Open data file */
if ((fd = open("y.txt", O_RDONLY)) == -1)
perror_exit ("Can't open data file");
if (fstat(fd, &statbuf) < 0)
perror_exit ("fstat failed");
if (!statbuf.st_size)
perror_exit ("filesize is 0");
if ((buf1 = mmap(NULL, statbuf.st_size, PROT_READ, MAP_SHARED, fd, 0))
== MAP_FAILED)
perror_exit ("mmap 1 failed");
close(fd);
/* Open data file a second time */
if ((fd = open("y.txt", O_RDONLY)) == -1)
perror_exit ("Can't open data file in second run");
if ((buf2 = mmap(NULL, statbuf.st_size, PROT_READ, MAP_SHARED, fd, 0))
== MAP_FAILED)
perror_exit ("mmap 2 failed");
close(fd);
sigemptyset (&unblock_sigsegv);
sigaddset (&unblock_sigsegv, SIGSEGV);
signal (SIGSEGV, sigsegv);
if (setjmp (r))
perror_exit ("SEGV in fork");
if ((pid = fork()))
{
// write (1, "continuing in parent\n", strlen ("continuing in parent\n"));
what = "parent";
}
else
{
// write (1, "continuing in child\n", strlen ("continuing in child\n"));
what = "child";
}
if (pid == -1)
perror_exit ("fork failed");
if (setjmp (r))
perror_exit (pid ? "SEGV in parent" : "SEGV in child");
msg = "testing buf1";
c = buf1[0];
msg = "testing buf2";
c = buf2[0];
if (setjmp (r))
perror_exit (pid ? "SEGV in parent's munmap" : "SEGV in child's munmap");
if (munmap((void *) buf1, statbuf.st_size))
perror_exit (pid ? "munmap failed in parent" : "munmap failed in child");
if (setjmp (r) == 0)
{
msg = "testing buf1 after unmap";
c = buf1[0];
perror_exit (pid ? "no SEGV in parent after munmap" : "no SEGV in child after munmap");
}
if (setjmp (r))
perror_exit (pid ? "SEGV in parent after munmap" : "SEGV in child after munmap");
msg = "testing buf2 again";
c = buf2[0];
if (setjmp (r))
perror_exit (pid ? "SEGV in parent's munmap" : "SEGV in child's munmap");
if (munmap((void *) buf2, statbuf.st_size))
perror_exit (pid ? "munmap failed in parent" : "munmap failed in child");
if (pid)
{
waitpid (pid, &status, 0);
unlink ("y.txt");
if (!WIFEXITED (status) || WEXITSTATUS (status))
{
printf ("forked process exited with status %p\n", (char *) status);
return 1;
}
}
return 0;
}
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