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/* Allocate a memory region shared across processes.
Copyright (C) 2017-2020 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <errno.h>
#include <stddef.h>
#include <support/support.h>
#include <support/xunistd.h>
#include <sys/mman.h>
/* Header for the allocation. It contains the size of the allocation
for subsequent unmapping. */
struct header
{
size_t total_size;
char data[] __attribute__ ((aligned (__alignof__ (max_align_t))));
};
void *
support_shared_allocate (size_t size)
{
size_t total_size = size + offsetof (struct header, data);
if (total_size < size)
{
errno = ENOMEM;
oom_error (__func__, size);
return NULL;
}
else
{
struct header *result = xmmap (NULL, total_size, PROT_READ | PROT_WRITE,
MAP_ANONYMOUS | MAP_SHARED, -1);
result->total_size = total_size;
return &result->data;
}
}
void
support_shared_free (void *data)
{
struct header *header = data - offsetof (struct header, data);
xmunmap (header, header->total_size);
}
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