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/* Test of free() function.
Copyright (C) 2020-2024 Free Software Foundation, Inc.
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>. */
/* Written by Bruno Haible <bruno@clisp.org>, 2020. */
#include <config.h>
/* Specification. */
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>
#if defined __linux__
# include <fcntl.h>
# include <stdint.h>
# include <string.h>
# include <sys/mman.h>
#endif
#include "macros.h"
/* The indirection through a volatile function pointer is necessary to prevent
a GCC optimization. Without it, when optimizing, GCC would "know" that errno
is unchanged by calling free(ptr), when ptr was the result of a malloc(...)
call in the same function. */
static int
get_errno (void)
{
volatile int err = errno;
return err;
}
static int (* volatile get_errno_func) (void) = get_errno;
int
main ()
{
/* Check that free() preserves errno. */
{
errno = 1789; /* Liberté, égalité, fraternité. */
free (NULL);
ASSERT_NO_STDIO (get_errno_func () == 1789);
}
{ /* Small memory allocations. */
#define N 10000
void * volatile ptrs[N];
size_t i;
for (i = 0; i < N; i++)
ptrs[i] = malloc (15);
for (i = 0; i < N; i++)
{
errno = 1789;
free (ptrs[i]);
ASSERT_NO_STDIO (get_errno_func () == 1789);
}
#undef N
}
{ /* Medium memory allocations. */
#define N 1000
void * volatile ptrs[N];
size_t i;
for (i = 0; i < N; i++)
ptrs[i] = malloc (729);
for (i = 0; i < N; i++)
{
errno = 1789;
free (ptrs[i]);
ASSERT_NO_STDIO (get_errno_func () == 1789);
}
#undef N
}
{ /* Large memory allocations. */
#define N 10
void * volatile ptrs[N];
size_t i;
for (i = 0; i < N; i++)
ptrs[i] = malloc (5318153);
for (i = 0; i < N; i++)
{
errno = 1789;
free (ptrs[i]);
ASSERT_NO_STDIO (get_errno_func () == 1789);
}
#undef N
}
/* Test a less common code path.
When malloc() is based on mmap(), free() can sometimes call munmap().
munmap() usually succeeds, but fails in a particular situation: when
- it has to unmap the middle part of a VMA, and
- the number of VMAs of a process is limited and the limit is
already reached.
The latter condition is fulfilled on Linux, when the file
/proc/sys/vm/max_map_count exists. This file contains the limit
- for Linux >= 2.4.19: 65536 (DEFAULT_MAX_MAP_COUNT in linux/include/linux/sched.h)
- for Linux >= 2.6.31: 65530 (DEFAULT_MAX_MAP_COUNT in linux/include/linux/mm.h).
But do not test it with glibc < 2.15, since that triggers a glibc internal
abort: "malloc.c:3551: munmap_chunk: Assertion `ret == 0' failed."
*/
#if defined __linux__ && !(__GLIBC__ == 2 && __GLIBC_MINOR__ < 15)
if (open ("/proc/sys/vm/max_map_count", O_RDONLY) >= 0)
{
/* Preparations. */
size_t pagesize = getpagesize ();
void *firstpage_backup = malloc (pagesize);
void *lastpage_backup = malloc (pagesize);
/* Allocate a large memory area, as a bumper, so that the MAP_FIXED
allocation later will not overwrite parts of the memory areas
allocated to ld.so or libc.so. */
void *bumper_region =
mmap (NULL, 0x1000000, PROT_READ, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
/* A file descriptor pointing to a regular file. */
int fd = open ("test-free", O_RDONLY);
if (firstpage_backup != NULL && lastpage_backup != NULL
&& bumper_region != (void *)(-1)
&& fd >= 0)
{
/* Do a large memory allocation. */
size_t big_size = 0x1000000;
void * volatile ptr = malloc (big_size - 0x100);
char *ptr_aligned = (char *) ((uintptr_t) ptr & ~(pagesize - 1));
/* This large memory allocation allocated a memory area
from ptr_aligned to ptr_aligned + big_size.
Enlarge this memory area by adding a page before and a page
after it. */
memcpy (firstpage_backup, ptr_aligned, pagesize);
memcpy (lastpage_backup, ptr_aligned + big_size - pagesize, pagesize);
if (mmap (ptr_aligned - pagesize, pagesize + big_size + pagesize,
PROT_READ | PROT_WRITE,
MAP_ANONYMOUS | MAP_PRIVATE | MAP_FIXED, -1, 0)
!= (void *)(-1))
{
memcpy (ptr_aligned, firstpage_backup, pagesize);
memcpy (ptr_aligned + big_size - pagesize, lastpage_backup, pagesize);
/* Now add as many mappings as we can.
Stop at 65536, in order not to crash the machine (in case the
limit has been increased by the system administrator). */
size_t i;
for (i = 0; i < 65536; i++)
if (mmap (NULL, pagesize, PROT_READ, MAP_FILE | MAP_PRIVATE, fd, 0)
== (void *)(-1))
break;
/* Now the number of VMAs of this process has hopefully attained
its limit. */
errno = 1789;
/* This call to free() is supposed to call
munmap (ptr_aligned, big_size);
which increases the number of VMAs by 1, which is supposed
to fail. */
free (ptr);
ASSERT_NO_STDIO (get_errno_func () == 1789);
}
}
}
#endif
return 0;
}
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