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#include <sys/types.h>
#include <sys/mman.h>
#include <unistd.h>
#include <fcntl.h>
#include <signal.h>
#include <setjmp.h>
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
sigset_t unblock_sigsegv;
jmp_buf r;
size_t pg;
int fd;
/* Checks behaviour of anonymous mmap.
test_1: If we map a 2-page region and unmap its second page, the first page
must remain.
test_2: If we map a 2-page region and unmap its first page, the second
page must remain.
test_3: If we map two consecutive 1-page regions and unmap them both with
one munmap, both must go away.
*/
void
perror_exit (const char *str, int code)
{
printf ("%s: %s\n", str, strerror (errno));
exit (code);
}
void
anonmap_init ()
{
sigemptyset (&unblock_sigsegv);
sigaddset (&unblock_sigsegv, SIGSEGV);
pg = getpagesize ();
fd = open ("/dev/zero", O_RDWR);
}
char *
anonmap (size_t size)
{
return (char *) mmap (0, size, PROT_READ|PROT_WRITE, MAP_PRIVATE, fd, 0);
}
void
anonfree (char *loc, size_t size)
{
munmap (loc, size);
}
void
sigsegv (int unused)
{
sigprocmask (SIG_UNBLOCK, &unblock_sigsegv, 0);
longjmp (r, 1);
}
int
compare_pointers (const void *a, const void *b)
{
const char *x = *(const char *const *)a;
const char *y = *(const char *const *)b;
if (x > y)
return 1;
if (x < y)
return -1;
return 0;
}
void
test_1 ()
{
char *x = anonmap (pg * 2);
if (x == (char *)MAP_FAILED)
perror_exit ("test 1 mmap", 1);
signal (SIGSEGV, sigsegv);
if (setjmp (r))
perror_exit ("test 1 fault", 2);
x[0] = 1;
x[pg] = 1;
anonfree (x + pg, pg);
x[0] = 2;
if (setjmp (r) == 0)
{
x[pg] = 1;
perror_exit ("test 1 no fault", 3);
}
}
void
test_2 ()
{
char *x = anonmap (pg * 2);
if (x == (char *)MAP_FAILED)
perror_exit ("test 2 mmap", 4);
signal (SIGSEGV, sigsegv);
if (setjmp (r))
perror_exit ("test 2 fault", 5);
x[0] = 1;
x[pg] = 1;
anonfree (x, pg);
x[pg] = 2;
if (setjmp (r) == 0)
{
x[0] = 1;
perror_exit ("test 2 no fault", 6);
}
}
void
test_3 ()
{
char *x[10];
char *y;
int i;
/* There's no way to guarantee we get consecutive pages from the OS. The
approach taken here is to allocate ten of them, sort the list, and
look for consecutive pages. */
for (i = 0; i < 10; i++)
{
x[i] = anonmap (pg);
if (x[i] == (char *)MAP_FAILED)
perror_exit ("test 3 mmap 1", 7);
}
qsort (x, 10, sizeof (char *), compare_pointers);
y = 0;
for (i = 0; i < 9; i++)
if (x[i] + pg == x[i+1])
{
y = x[i];
break;
}
if (y == 0)
{
fputs ("test 3: couldn't get two consecutive pages, giving up\n", stdout);
exit (65);
}
signal (SIGSEGV, sigsegv);
if (setjmp (r))
perror_exit ("test 3 fault", 8);
y[0] = 1;
y[pg] = 1;
anonfree (y, pg * 2);
if (setjmp (r) == 0)
{
y[0] = 1;
perror_exit ("test 3 no fault 1", 9);
}
signal (SIGSEGV, sigsegv);
if (setjmp (r) == 0)
{
y[pg] = 1;
perror_exit ("test 3 no fault 2", 10);
}
}
int
main ()
{
anonmap_init();
test_1();
test_2();
test_3();
exit(0);
}
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