132 lines
4.5 KiB
C
132 lines
4.5 KiB
C
/* Test that free preserves errno.
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Copyright (C) 2020-2022 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#include <errno.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include <fcntl.h>
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#include <stdint.h>
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#include <string.h>
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#include <sys/mman.h>
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#include <support/check.h>
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#include <support/support.h>
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#include <support/temp_file.h>
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#include <support/xunistd.h>
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/* The __attribute__ ((weak)) prevents a GCC optimization. Without
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it, GCC would "know" that errno is unchanged by calling free (ptr),
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when ptr was the result of a malloc call in the same function. */
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int __attribute__ ((weak))
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get_errno (void)
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{
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return errno;
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}
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static int
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do_test (void)
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{
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/* Check that free() preserves errno. */
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{
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errno = 1789; /* Liberté, égalité, fraternité. */
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free (NULL);
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TEST_VERIFY (get_errno () == 1789);
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}
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{ /* Large memory allocations, to force mmap. */
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enum { N = 2 };
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void * volatile ptrs[N];
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size_t i;
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for (i = 0; i < N; i++)
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ptrs[i] = xmalloc (5318153);
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for (i = 0; i < N; i++)
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{
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errno = 1789;
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free (ptrs[i]);
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TEST_VERIFY (get_errno () == 1789);
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}
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}
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/* Test a less common code path.
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When malloc() is based on mmap(), free() can sometimes call munmap().
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munmap() usually succeeds, but fails in a particular situation: when
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- it has to unmap the middle part of a VMA, and
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- the number of VMAs of a process is limited and the limit is
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already reached.
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The latter condition is fulfilled on Linux, when the file
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/proc/sys/vm/max_map_count exists. For all known Linux versions
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the default limit is at most 65536.
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*/
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#if defined __linux__
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if (xopen ("/proc/sys/vm/max_map_count", O_RDONLY, 0) >= 0)
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{
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/* Preparations. */
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size_t pagesize = getpagesize ();
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void *firstpage_backup = xmalloc (pagesize);
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void *lastpage_backup = xmalloc (pagesize);
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/* Allocate a large memory area, as a bumper, so that the MAP_FIXED
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allocation later will not overwrite parts of the memory areas
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allocated to ld.so or libc.so. */
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xmmap (NULL, 0x1000000, PROT_READ, MAP_ANONYMOUS | MAP_PRIVATE, -1);
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/* A file descriptor pointing to a regular file. */
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int fd = create_temp_file ("tst-free-errno", NULL);
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if (fd < 0)
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FAIL_EXIT1 ("cannot create temporary file");
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/* Do a large memory allocation. */
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size_t big_size = 0x1000000;
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void * volatile ptr = xmalloc (big_size - 0x100);
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char *ptr_aligned = (char *) ((uintptr_t) ptr & ~(pagesize - 1));
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/* This large memory allocation allocated a memory area
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from ptr_aligned to ptr_aligned + big_size.
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Enlarge this memory area by adding a page before and a page
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after it. */
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memcpy (firstpage_backup, ptr_aligned, pagesize);
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memcpy (lastpage_backup, ptr_aligned + big_size - pagesize,
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pagesize);
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xmmap (ptr_aligned - pagesize, pagesize + big_size + pagesize,
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PROT_READ | PROT_WRITE,
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MAP_ANONYMOUS | MAP_PRIVATE | MAP_FIXED, -1);
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memcpy (ptr_aligned, firstpage_backup, pagesize);
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memcpy (ptr_aligned + big_size - pagesize, lastpage_backup,
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pagesize);
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/* Now add as many mappings as we can.
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Stop at 65536, in order not to crash the machine (in case the
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limit has been increased by the system administrator). */
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for (int i = 0; i < 65536; i++)
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if (mmap (NULL, pagesize, PROT_READ, MAP_FILE | MAP_PRIVATE, fd, 0)
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== MAP_FAILED)
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break;
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/* Now the number of VMAs of this process has hopefully attained
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its limit. */
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errno = 1789;
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/* This call to free() is supposed to call
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munmap (ptr_aligned, big_size);
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which increases the number of VMAs by 1, which is supposed
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to fail. */
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free (ptr);
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TEST_VERIFY (get_errno () == 1789);
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}
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#endif
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return 0;
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}
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#include <support/test-driver.c>
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