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/* brk -- Adjust the "break" at the end of initial data. NaCl version.
Copyright (C) 2015-2017 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
<http://www.gnu.org/licenses/>. */
#include <errno.h>
#include <stdint.h>
#include <sys/mman.h>
#include <sys/param.h>
#include <unistd.h>
/* sbrk.c expects this. */
void *__curbrk;
static uintptr_t
page_above (void *addr)
{
return ALIGN_UP ((uintptr_t) addr, EXEC_PAGESIZE);
}
/* Set the end of the process's data space to ADDR.
Return 0 if successful, -1 if not. */
int
__brk (void *addr)
{
/* The NaCl sysbrk call is deprecated, so we do not use it here. Other
libc code expects that __sbrk can be used at least a little bit, so
rather than a plain stub we have a minimal __brk implementation here.
It just uses mmap/munmap to grow or shrink the break area, punting as
soon as mmap fails to use the same contiguous area. */
if (__glibc_unlikely (__curbrk == NULL))
{
/* This is the first call. We must initialize the record
of the current position. It starts out at the end of the
main program's data segment. */
/* XXX dynamic case??? */
extern char _end[];
__curbrk = _end;
}
if (__glibc_unlikely (addr == NULL))
/* This is a call just to ensure that __curbrk is set up. */
return 0;
uintptr_t old_limit = page_above (__curbrk);
uintptr_t new_limit = page_above (addr);
if (old_limit > new_limit)
{
/* We're shrinking the old heap enough to release some pages. */
if (__munmap ((void *) new_limit, old_limit - new_limit) != 0)
return -1;
}
else if (old_limit < new_limit)
{
/* We're growing the old heap enough to need some more pages.
See if they are available. */
void *new_space = __mmap ((void *) old_limit, new_limit - old_limit,
PROT_READ | PROT_WRITE, MAP_ANON, -1, 0);
if (new_space != (void *) old_limit)
{
if (new_space != MAP_FAILED)
{
/* mmap chose some different place for the pages
because the contiguous area was not available.
Oh well. We can't use that. */
__munmap (new_space, new_limit - old_limit);
__set_errno (ENOMEM);
}
return -1;
}
}
__curbrk = addr;
return 0;
}
weak_alias (__brk, brk)
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