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