1 /* Copyright (C) 1991-2022 Free Software Foundation, Inc. 2 This file is part of the GNU C Library. 3 4 The GNU C Library is free software; you can redistribute it and/or 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. 8 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 12 Lesser General Public License for more details. 13 14 You should have received a copy of the GNU Lesser General Public 15 License along with the GNU C Library; if not, see 16 <https://www.gnu.org/licenses/>. */ 17 18 /* Mark symbols hidden in static PIE for early self relocation to work. */ 19 #if BUILD_PIE_DEFAULT 20 # pragma GCC visibility push(hidden) 21 #endif 22 #include <errno.h> 23 #include <libc-internal.h> 24 #include <stdbool.h> 25 #include <stdint.h> 26 #include <unistd.h> 27 28 /* Defined in brk.c. */ 29 extern void *__curbrk; 30 extern int __brk (void *addr); 31 32 /* Extend the process's data space by INCREMENT. 33 If INCREMENT is negative, shrink data space by - INCREMENT. 34 Return start of new space allocated, or -1 for errors. */ 35 void * __sbrk(intptr_t increment)36__sbrk (intptr_t increment) 37 { 38 /* Controls whether __brk (0) is called to read the brk value from 39 the kernel. */ 40 bool update_brk = __curbrk == NULL; 41 42 #if defined (SHARED) && ! IS_IN (rtld) 43 if (!__libc_initial) 44 { 45 if (increment != 0) 46 { 47 /* Do not allow changing the brk from an inner libc because 48 it cannot be synchronized with the outer libc's brk. */ 49 __set_errno (ENOMEM); 50 return (void *) -1; 51 } 52 /* Querying the kernel's brk value from an inner namespace is 53 fine. */ 54 update_brk = true; 55 } 56 #endif 57 58 if (update_brk) 59 if (__brk (0) < 0) /* Initialize the break. */ 60 return (void *) -1; 61 62 if (increment == 0) 63 return __curbrk; 64 65 void *oldbrk = __curbrk; 66 if (increment > 0 67 ? ((uintptr_t) oldbrk + (uintptr_t) increment < (uintptr_t) oldbrk) 68 : ((uintptr_t) oldbrk < (uintptr_t) -increment)) 69 { 70 __set_errno (ENOMEM); 71 return (void *) -1; 72 } 73 74 if (__brk (oldbrk + increment) < 0) 75 return (void *) -1; 76 77 return oldbrk; 78 } 79 libc_hidden_def (__sbrk) 80 weak_alias (__sbrk, sbrk) 81