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2b778ceb | 1 | /* Copyright (C) 1991-2021 Free Software Foundation, Inc. |
478b92f0 | 2 | This file is part of the GNU C Library. |
28f540f4 | 3 | |
478b92f0 | 4 | The GNU C Library is free software; you can redistribute it and/or |
41bdb6e2 AJ |
5 | modify it under the terms of the GNU Lesser General Public |
6 | License as published by the Free Software Foundation; either | |
7 | version 2.1 of the License, or (at your option) any later version. | |
28f540f4 | 8 | |
478b92f0 UD |
9 | The GNU C Library is distributed in the hope that it will be useful, |
10 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
11 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
41bdb6e2 | 12 | Lesser General Public License for more details. |
28f540f4 | 13 | |
41bdb6e2 | 14 | You should have received a copy of the GNU Lesser General Public |
59ba27a6 | 15 | License along with the GNU C Library; if not, see |
5a82c748 | 16 | <https://www.gnu.org/licenses/>. */ |
28f540f4 | 17 | |
683158e0 | 18 | #include <errno.h> |
e7570f41 FW |
19 | #include <libc-internal.h> |
20 | #include <stdbool.h> | |
1fdd89a7 UD |
21 | #include <stdint.h> |
22 | #include <unistd.h> | |
28f540f4 RM |
23 | |
24 | /* Defined in brk.c. */ | |
683158e0 RM |
25 | extern void *__curbrk; |
26 | extern int __brk (void *addr); | |
28f540f4 RM |
27 | |
28 | /* Extend the process's data space by INCREMENT. | |
29 | If INCREMENT is negative, shrink data space by - INCREMENT. | |
30 | Return start of new space allocated, or -1 for errors. */ | |
683158e0 | 31 | void * |
0ed99ce4 | 32 | __sbrk (intptr_t increment) |
28f540f4 | 33 | { |
e7570f41 FW |
34 | /* Controls whether __brk (0) is called to read the brk value from |
35 | the kernel. */ | |
36 | bool update_brk = __curbrk == NULL; | |
37 | ||
38 | #if defined (SHARED) && ! IS_IN (rtld) | |
39 | if (!__libc_initial) | |
40 | { | |
41 | if (increment != 0) | |
42 | { | |
43 | /* Do not allow changing the brk from an inner libc because | |
44 | it cannot be synchronized with the outer libc's brk. */ | |
45 | __set_errno (ENOMEM); | |
46 | return (void *) -1; | |
47 | } | |
48 | /* Querying the kernel's brk value from an inner namespace is | |
49 | fine. */ | |
50 | update_brk = true; | |
51 | } | |
52 | #endif | |
53 | ||
54 | if (update_brk) | |
14bab8de UD |
55 | if (__brk (0) < 0) /* Initialize the break. */ |
56 | return (void *) -1; | |
28f540f4 RM |
57 | |
58 | if (increment == 0) | |
59 | return __curbrk; | |
60 | ||
e7570f41 | 61 | void *oldbrk = __curbrk; |
c13e0783 CH |
62 | if (increment > 0 |
63 | ? ((uintptr_t) oldbrk + (uintptr_t) increment < (uintptr_t) oldbrk) | |
64 | : ((uintptr_t) oldbrk < (uintptr_t) -increment)) | |
65 | { | |
66 | __set_errno (ENOMEM); | |
67 | return (void *) -1; | |
68 | } | |
69 | ||
70 | if (__brk (oldbrk + increment) < 0) | |
683158e0 | 71 | return (void *) -1; |
28f540f4 RM |
72 | |
73 | return oldbrk; | |
74 | } | |
37ba7d66 | 75 | libc_hidden_def (__sbrk) |
28f540f4 | 76 | weak_alias (__sbrk, sbrk) |