| xf.li | bdd93d5 | 2023-05-12 07:10:14 -0700 | [diff] [blame] | 1 | /* brk -- Adjust the "break" at the end of initial data. NaCl version. |
| 2 | Copyright (C) 2015-2016 Free Software Foundation, Inc. |
| 3 | This file is part of the GNU C Library. |
| 4 | |
| 5 | The GNU C Library is free software; you can redistribute it and/or |
| 6 | modify it under the terms of the GNU Lesser General Public |
| 7 | License as published by the Free Software Foundation; either |
| 8 | version 2.1 of the License, or (at your option) any later version. |
| 9 | |
| 10 | The GNU C Library is distributed in the hope that it will be useful, |
| 11 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| 13 | Lesser General Public License for more details. |
| 14 | |
| 15 | You should have received a copy of the GNU Lesser General Public |
| 16 | License along with the GNU C Library; if not, see |
| 17 | <http://www.gnu.org/licenses/>. */ |
| 18 | |
| 19 | #include <errno.h> |
| 20 | #include <libc-internal.h> |
| 21 | #include <stdint.h> |
| 22 | #include <sys/mman.h> |
| 23 | #include <sys/param.h> |
| 24 | #include <unistd.h> |
| 25 | |
| 26 | /* sbrk.c expects this. */ |
| 27 | void *__curbrk; |
| 28 | |
| 29 | static uintptr_t |
| 30 | page_above (void *addr) |
| 31 | { |
| 32 | return ALIGN_UP ((uintptr_t) addr, EXEC_PAGESIZE); |
| 33 | } |
| 34 | |
| 35 | /* Set the end of the process's data space to ADDR. |
| 36 | Return 0 if successful, -1 if not. */ |
| 37 | int |
| 38 | __brk (void *addr) |
| 39 | { |
| 40 | /* The NaCl sysbrk call is deprecated, so we do not use it here. Other |
| 41 | libc code expects that __sbrk can be used at least a little bit, so |
| 42 | rather than a plain stub we have a minimal __brk implementation here. |
| 43 | It just uses mmap/munmap to grow or shrink the break area, punting as |
| 44 | soon as mmap fails to use the same contiguous area. */ |
| 45 | |
| 46 | if (__glibc_unlikely (__curbrk == NULL)) |
| 47 | { |
| 48 | /* This is the first call. We must initialize the record |
| 49 | of the current position. It starts out at the end of the |
| 50 | main program's data segment. */ |
| 51 | |
| 52 | /* XXX dynamic case??? */ |
| 53 | extern char _end[]; |
| 54 | __curbrk = _end; |
| 55 | } |
| 56 | |
| 57 | if (__glibc_unlikely (addr == NULL)) |
| 58 | /* This is a call just to ensure that __curbrk is set up. */ |
| 59 | return 0; |
| 60 | |
| 61 | uintptr_t old_limit = page_above (__curbrk); |
| 62 | uintptr_t new_limit = page_above (addr); |
| 63 | |
| 64 | if (old_limit > new_limit) |
| 65 | { |
| 66 | /* We're shrinking the old heap enough to release some pages. */ |
| 67 | if (__munmap ((void *) new_limit, old_limit - new_limit) != 0) |
| 68 | return -1; |
| 69 | } |
| 70 | else if (old_limit < new_limit) |
| 71 | { |
| 72 | /* We're growing the old heap enough to need some more pages. |
| 73 | See if they are available. */ |
| 74 | void *new_space = __mmap ((void *) old_limit, new_limit - old_limit, |
| 75 | PROT_READ | PROT_WRITE, MAP_ANON, -1, 0); |
| 76 | if (new_space != (void *) old_limit) |
| 77 | { |
| 78 | if (new_space != MAP_FAILED) |
| 79 | { |
| 80 | /* mmap chose some different place for the pages |
| 81 | because the contiguous area was not available. |
| 82 | Oh well. We can't use that. */ |
| 83 | __munmap (new_space, new_limit - old_limit); |
| 84 | __set_errno (ENOMEM); |
| 85 | } |
| 86 | return -1; |
| 87 | } |
| 88 | } |
| 89 | |
| 90 | __curbrk = addr; |
| 91 | return 0; |
| 92 | } |
| 93 | weak_alias (__brk, brk) |