]>
Commit | Line | Data |
---|---|---|
b05fae4d AZ |
1 | /* Minimal malloc implementation for dynamic linker and static |
2 | initialization. | |
581c785b | 3 | Copyright (C) 1995-2022 Free Software Foundation, Inc. |
b05fae4d AZ |
4 | This file is part of the GNU C Library. |
5 | ||
6 | The GNU C Library is free software; you can redistribute it and/or | |
7 | modify it under the terms of the GNU Lesser General Public | |
8 | License as published by the Free Software Foundation; either | |
9 | version 2.1 of the License, or (at your option) any later version. | |
10 | ||
11 | The GNU C Library is distributed in the hope that it will be useful, | |
12 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
13 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
14 | Lesser General Public License for more details. | |
15 | ||
16 | You should have received a copy of the GNU Lesser General Public | |
17 | License along with the GNU C Library; if not, see | |
18 | <https://www.gnu.org/licenses/>. */ | |
19 | ||
d8c2e8e0 AZ |
20 | /* Mark symbols hidden in static PIE for early self relocation to work. |
21 | Note: string.h may have ifuncs which cannot be hidden on i686. */ | |
22 | #if BUILD_PIE_DEFAULT | |
23 | # pragma GCC visibility push(hidden) | |
24 | #endif | |
b05fae4d AZ |
25 | #include <assert.h> |
26 | #include <string.h> | |
27 | #include <ldsodefs.h> | |
28 | #include <malloc/malloc-internal.h> | |
29 | ||
30 | static void *alloc_ptr, *alloc_end, *alloc_last_block; | |
31 | ||
32 | /* Allocate an aligned memory block. */ | |
33 | void * | |
34 | __minimal_malloc (size_t n) | |
35 | { | |
36 | if (alloc_end == 0) | |
37 | { | |
38 | /* Consume any unused space in the last page of our data segment. */ | |
39 | extern int _end attribute_hidden; | |
40 | alloc_ptr = &_end; | |
41 | alloc_end = (void *) 0 + (((alloc_ptr - (void *) 0) | |
42 | + GLRO(dl_pagesize) - 1) | |
43 | & ~(GLRO(dl_pagesize) - 1)); | |
44 | } | |
45 | ||
46 | /* Make sure the allocation pointer is ideally aligned. */ | |
47 | alloc_ptr = (void *) 0 + (((alloc_ptr - (void *) 0) + MALLOC_ALIGNMENT - 1) | |
48 | & ~(MALLOC_ALIGNMENT - 1)); | |
49 | ||
50 | if (alloc_ptr + n >= alloc_end || n >= -(uintptr_t) alloc_ptr) | |
51 | { | |
52 | /* Insufficient space left; allocate another page plus one extra | |
53 | page to reduce number of mmap calls. */ | |
54 | caddr_t page; | |
55 | size_t nup = (n + GLRO(dl_pagesize) - 1) & ~(GLRO(dl_pagesize) - 1); | |
56 | if (__glibc_unlikely (nup == 0 && n != 0)) | |
57 | return NULL; | |
58 | nup += GLRO(dl_pagesize); | |
59 | page = __mmap (0, nup, PROT_READ|PROT_WRITE, | |
60 | MAP_ANON|MAP_PRIVATE, -1, 0); | |
61 | if (page == MAP_FAILED) | |
62 | return NULL; | |
63 | if (page != alloc_end) | |
64 | alloc_ptr = page; | |
65 | alloc_end = page + nup; | |
66 | } | |
67 | ||
68 | alloc_last_block = (void *) alloc_ptr; | |
69 | alloc_ptr += n; | |
70 | return alloc_last_block; | |
71 | } | |
72 | ||
73 | /* We use this function occasionally since the real implementation may | |
74 | be optimized when it can assume the memory it returns already is | |
75 | set to NUL. */ | |
76 | void * | |
77 | __minimal_calloc (size_t nmemb, size_t size) | |
78 | { | |
79 | /* New memory from the trivial malloc above is always already cleared. | |
80 | (We make sure that's true in the rare occasion it might not be, | |
81 | by clearing memory in free, below.) */ | |
82 | size_t bytes = nmemb * size; | |
83 | ||
84 | #define HALF_SIZE_T (((size_t) 1) << (8 * sizeof (size_t) / 2)) | |
85 | if (__builtin_expect ((nmemb | size) >= HALF_SIZE_T, 0) | |
86 | && size != 0 && bytes / size != nmemb) | |
87 | return NULL; | |
88 | ||
89 | return malloc (bytes); | |
90 | } | |
91 | ||
92 | /* This will rarely be called. */ | |
93 | void | |
94 | __minimal_free (void *ptr) | |
95 | { | |
96 | /* We can free only the last block allocated. */ | |
97 | if (ptr == alloc_last_block) | |
98 | { | |
99 | /* Since this is rare, we clear the freed block here | |
100 | so that calloc can presume malloc returns cleared memory. */ | |
101 | memset (alloc_last_block, '\0', alloc_ptr - alloc_last_block); | |
102 | alloc_ptr = alloc_last_block; | |
103 | } | |
104 | } | |
105 | ||
106 | /* This is only called with the most recent block returned by malloc. */ | |
107 | void * | |
108 | __minimal_realloc (void *ptr, size_t n) | |
109 | { | |
110 | if (ptr == NULL) | |
111 | return malloc (n); | |
112 | assert (ptr == alloc_last_block); | |
113 | size_t old_size = alloc_ptr - alloc_last_block; | |
114 | alloc_ptr = alloc_last_block; | |
115 | void *new = malloc (n); | |
116 | return new != ptr ? memcpy (new, ptr, old_size) : new; | |
117 | } |