mirror of
git://sourceware.org/git/glibc.git
synced 2024-12-21 04:31:04 +08:00
94 lines
3.0 KiB
C
94 lines
3.0 KiB
C
|
/* brk -- Adjust the "break" at the end of initial data. NaCl version.
|
||
|
|
Copyright (C) 2015 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 <libc-internal.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)
|