1 /* This test file is part of GDB, the GNU debugger. 2 3 Copyright 2021-2023 Free Software Foundation, Inc. 4 5 This program is free software; you can redistribute it and/or modify 6 it under the terms of the GNU General Public License as published by 7 the Free Software Foundation; either version 3 of the License, or 8 (at your option) any later version. 9 10 This program 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 13 GNU General Public License for more details. 14 15 You should have received a copy of the GNU General Public License 16 along with this program. If not, see <http://www.gnu.org/licenses/>. 17 */ 18 19 #include <stdlib.h> 20 #include <assert.h> 21 #include <string.h> 22 #include <stdint.h> 23 24 /* Return true if address P is ALIGNMENT-byte aligned. */ 25 26 static int 27 is_aligned (void *p, size_t alignment) 28 { 29 size_t mask = (alignment - 1); 30 return ((uintptr_t)p & mask) == 0; 31 } 32 33 /* Allocate SIZE memory with ALIGNMENT, and return it. If FREE_POINTER, 34 return in it the corresponding pointer to be passed to free. 35 36 Do the alignment precisely, in other words, if an alignment of 4 is 37 requested, make sure the pointer is 4-byte aligned, but not 8-byte 38 aligned. In other words, make sure the pointer is not overaligned. 39 40 The benefit of using precise alignment is that accidentally specifying 41 a too low alignment will not be compensated by accidental 42 overalignment. */ 43 44 static void * 45 precise_aligned_alloc (size_t alignment, size_t size, void **free_pointer) 46 { 47 /* Allocate extra to compensate for "p += alignment". */ 48 size_t alloc_size = size + alignment; 49 50 /* Align extra, to be able to do precise align. */ 51 void *p = aligned_alloc (alignment * 2, alloc_size); 52 assert (p != NULL); 53 void *p_orig = p; 54 void *p_end = p + alloc_size; 55 56 /* Make p precisely aligned. */ 57 p += alignment; 58 59 /* Verify p is without bounds, and points to large enough area. */ 60 assert (p >= p_orig); 61 assert (p + size <= p_end); 62 63 /* Verify required alignment. */ 64 assert (is_aligned (p, alignment)); 65 66 /* Verify required alignment is precise. */ 67 assert (! is_aligned (p, 2 * alignment)); 68 69 if (free_pointer != NULL) 70 *free_pointer = p_orig; 71 72 return p; 73 } 74 75 /* Duplicate data SRC of size SIZE to a newly allocated, precisely aligned 76 location with alignment ALIGNMENT. */ 77 78 static void * 79 precise_aligned_dup (size_t alignment, size_t size, void **free_pointer, 80 void *src) 81 { 82 void *p = precise_aligned_alloc (alignment, size, free_pointer); 83 84 memcpy (p, src, size); 85 86 return p; 87 } 88