| /* brk -- Adjust the "break" at the end of initial data. NaCl version. |
| Copyright (C) 2015-2016 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) |