1 /*-
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright (c) 1983 Regents of the University of California.
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 * 3. Neither the name of the University nor the names of its contributors
16 * may be used to endorse or promote products derived from this software
17 * without specific prior written permission.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 * SUCH DAMAGE.
30 */
31
32 #if defined(LIBC_SCCS) && !defined(lint)
33 /*static char *sccsid = "from: @(#)malloc.c 5.11 (Berkeley) 2/23/91";*/
34 static char *rcsid = "$FreeBSD$";
35 #endif /* LIBC_SCCS and not lint */
36
37 /*
38 * malloc.c (Caltech) 2/21/82
39 * Chris Kingsley, kingsley@cit-20.
40 *
41 * This is a very fast storage allocator. It allocates blocks of a small
42 * number of different sizes, and keeps free lists of each size. Blocks that
43 * don't exactly fit are passed up to the next larger size. In this
44 * implementation, the available sizes are 2^n-4 (or 2^n-10) bytes long.
45 * This is designed for use in a virtual memory environment.
46 */
47
48 #include <sys/param.h>
49 #include <sys/sysctl.h>
50 #include <sys/mman.h>
51 #include <errno.h>
52 #include <stdarg.h>
53 #include <stddef.h>
54 #include <string.h>
55 #include <unistd.h>
56 #include "rtld.h"
57 #include "rtld_printf.h"
58 #include "paths.h"
59
60 /*
61 * Pre-allocate mmap'ed pages
62 */
63 #define NPOOLPAGES (128*1024/pagesz)
64 static caddr_t pagepool_start, pagepool_end;
65
66 /*
67 * The overhead on a block is at least 4 bytes. When free, this space
68 * contains a pointer to the next free block, and the bottom two bits must
69 * be zero. When in use, the first byte is set to MAGIC, and the second
70 * byte is the size index. The remaining bytes are for alignment.
71 * If range checking is enabled then a second word holds the size of the
72 * requested block, less 1, rounded up to a multiple of sizeof(RMAGIC).
73 * The order of elements is critical: ov_magic must overlay the low order
74 * bits of ov_next, and ov_magic can not be a valid ov_next bit pattern.
75 */
76 union overhead {
77 union overhead *ov_next; /* when free */
78 struct {
79 u_char ovu_magic; /* magic number */
80 u_char ovu_index; /* bucket # */
81 } ovu;
82 #define ov_magic ovu.ovu_magic
83 #define ov_index ovu.ovu_index
84 };
85
86 static void morecore(int bucket);
87 static int morepages(int n);
88 static int findbucket(union overhead *freep, int srchlen);
89
90 #define MAGIC 0xef /* magic # on accounting info */
91
92 /*
93 * nextf[i] is the pointer to the next free block of size 2^(i+3). The
94 * smallest allocatable block is 8 bytes. The overhead information
95 * precedes the data area returned to the user.
96 */
97 #define NBUCKETS 30
98 static union overhead *nextf[NBUCKETS];
99
100 static int pagesz; /* page size */
101 static int pagebucket; /* page size bucket */
102
103 /*
104 * The array of supported page sizes is provided by the user, i.e., the
105 * program that calls this storage allocator. That program must initialize
106 * the array before making its first call to allocate storage. The array
107 * must contain at least one page size. The page sizes must be stored in
108 * increasing order.
109 */
110
111 void *
__crt_malloc(size_t nbytes)112 __crt_malloc(size_t nbytes)
113 {
114 union overhead *op;
115 int bucket;
116 ssize_t n;
117 size_t amt;
118
119 /*
120 * First time malloc is called, setup page size and
121 * align break pointer so all data will be page aligned.
122 */
123 if (pagesz == 0) {
124 pagesz = n = pagesizes[0];
125 if (morepages(NPOOLPAGES) == 0)
126 return NULL;
127 op = (union overhead *)(pagepool_start);
128 n = n - sizeof (*op) - ((long)op & (n - 1));
129 if (n < 0)
130 n += pagesz;
131 if (n) {
132 pagepool_start += n;
133 }
134 bucket = 0;
135 amt = 8;
136 while ((unsigned)pagesz > amt) {
137 amt <<= 1;
138 bucket++;
139 }
140 pagebucket = bucket;
141 }
142 /*
143 * Convert amount of memory requested into closest block size
144 * stored in hash buckets which satisfies request.
145 * Account for space used per block for accounting.
146 */
147 if (nbytes <= (unsigned long)(n = pagesz - sizeof(*op))) {
148 amt = 8; /* size of first bucket */
149 bucket = 0;
150 n = -sizeof(*op);
151 } else {
152 amt = pagesz;
153 bucket = pagebucket;
154 }
155 while (nbytes > amt + n) {
156 amt <<= 1;
157 if (amt == 0)
158 return (NULL);
159 bucket++;
160 }
161 /*
162 * If nothing in hash bucket right now,
163 * request more memory from the system.
164 */
165 if ((op = nextf[bucket]) == NULL) {
166 morecore(bucket);
167 if ((op = nextf[bucket]) == NULL)
168 return (NULL);
169 }
170 /* remove from linked list */
171 nextf[bucket] = op->ov_next;
172 op->ov_magic = MAGIC;
173 op->ov_index = bucket;
174 return ((char *)(op + 1));
175 }
176
177 void *
__crt_calloc(size_t num,size_t size)178 __crt_calloc(size_t num, size_t size)
179 {
180 void *ret;
181
182 if (size != 0 && (num * size) / size != num) {
183 /* size_t overflow. */
184 return (NULL);
185 }
186
187 if ((ret = __crt_malloc(num * size)) != NULL)
188 memset(ret, 0, num * size);
189
190 return (ret);
191 }
192
193 /*
194 * Allocate more memory to the indicated bucket.
195 */
196 static void
morecore(int bucket)197 morecore(int bucket)
198 {
199 union overhead *op;
200 int sz; /* size of desired block */
201 int amt; /* amount to allocate */
202 int nblks; /* how many blocks we get */
203
204 /*
205 * sbrk_size <= 0 only for big, FLUFFY, requests (about
206 * 2^30 bytes on a VAX, I think) or for a negative arg.
207 */
208 if ((unsigned)bucket >= NBBY * sizeof(int) - 4)
209 return;
210 sz = 1 << (bucket + 3);
211 if (sz < pagesz) {
212 amt = pagesz;
213 nblks = amt / sz;
214 } else {
215 amt = sz + pagesz;
216 nblks = 1;
217 }
218 if (amt > pagepool_end - pagepool_start)
219 if (morepages(amt/pagesz + NPOOLPAGES) == 0)
220 return;
221 op = (union overhead *)pagepool_start;
222 pagepool_start += amt;
223
224 /*
225 * Add new memory allocated to that on
226 * free list for this hash bucket.
227 */
228 nextf[bucket] = op;
229 while (--nblks > 0) {
230 op->ov_next = (union overhead *)((caddr_t)op + sz);
231 op = (union overhead *)((caddr_t)op + sz);
232 }
233 }
234
235 void
__crt_free(void * cp)236 __crt_free(void *cp)
237 {
238 int size;
239 union overhead *op;
240
241 if (cp == NULL)
242 return;
243 op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
244 if (op->ov_magic != MAGIC)
245 return; /* sanity */
246 size = op->ov_index;
247 op->ov_next = nextf[size]; /* also clobbers ov_magic */
248 nextf[size] = op;
249 }
250
251 /*
252 * When a program attempts "storage compaction" as mentioned in the
253 * old malloc man page, it realloc's an already freed block. Usually
254 * this is the last block it freed; occasionally it might be farther
255 * back. We have to search all the free lists for the block in order
256 * to determine its bucket: 1st we make one pass through the lists
257 * checking only the first block in each; if that fails we search
258 * ``realloc_srchlen'' blocks in each list for a match (the variable
259 * is extern so the caller can modify it). If that fails we just copy
260 * however many bytes was given to realloc() and hope it's not huge.
261 */
262 static int realloc_srchlen = 4; /* 4 should be plenty, -1 =>'s whole list */
263
264 void *
__crt_realloc(void * cp,size_t nbytes)265 __crt_realloc(void *cp, size_t nbytes)
266 {
267 u_int onb;
268 int i;
269 union overhead *op;
270 char *res;
271 int was_alloced = 0;
272
273 if (cp == NULL)
274 return (__crt_malloc(nbytes));
275 op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
276 if (op->ov_magic == MAGIC) {
277 was_alloced++;
278 i = op->ov_index;
279 } else {
280 /*
281 * Already free, doing "compaction".
282 *
283 * Search for the old block of memory on the
284 * free list. First, check the most common
285 * case (last element free'd), then (this failing)
286 * the last ``realloc_srchlen'' items free'd.
287 * If all lookups fail, then assume the size of
288 * the memory block being realloc'd is the
289 * largest possible (so that all "nbytes" of new
290 * memory are copied into). Note that this could cause
291 * a memory fault if the old area was tiny, and the moon
292 * is gibbous. However, that is very unlikely.
293 */
294 if ((i = findbucket(op, 1)) < 0 &&
295 (i = findbucket(op, realloc_srchlen)) < 0)
296 i = NBUCKETS;
297 }
298 onb = 1 << (i + 3);
299 if (onb < (u_int)pagesz)
300 onb -= sizeof(*op);
301 else
302 onb += pagesz - sizeof(*op);
303 /* avoid the copy if same size block */
304 if (was_alloced) {
305 if (i) {
306 i = 1 << (i + 2);
307 if (i < pagesz)
308 i -= sizeof(*op);
309 else
310 i += pagesz - sizeof(*op);
311 }
312 if (nbytes <= onb && nbytes > (size_t)i)
313 return (cp);
314 __crt_free(cp);
315 }
316 if ((res = __crt_malloc(nbytes)) == NULL)
317 return (NULL);
318 if (cp != res) /* common optimization if "compacting" */
319 bcopy(cp, res, (nbytes < onb) ? nbytes : onb);
320 return (res);
321 }
322
323 /*
324 * Search ``srchlen'' elements of each free list for a block whose
325 * header starts at ``freep''. If srchlen is -1 search the whole list.
326 * Return bucket number, or -1 if not found.
327 */
328 static int
findbucket(union overhead * freep,int srchlen)329 findbucket(union overhead *freep, int srchlen)
330 {
331 union overhead *p;
332 int i, j;
333
334 for (i = 0; i < NBUCKETS; i++) {
335 j = 0;
336 for (p = nextf[i]; p && j != srchlen; p = p->ov_next) {
337 if (p == freep)
338 return (i);
339 j++;
340 }
341 }
342 return (-1);
343 }
344
345 static int
morepages(int n)346 morepages(int n)
347 {
348 caddr_t addr;
349 int offset;
350
351 if (pagepool_end - pagepool_start > pagesz) {
352 addr = (caddr_t)roundup2((long)pagepool_start, pagesz);
353 if (munmap(addr, pagepool_end - addr) != 0) {
354 #ifdef IN_RTLD
355 rtld_fdprintf(STDERR_FILENO, _BASENAME_RTLD ": "
356 "morepages: cannot munmap %p: %s\n",
357 addr, rtld_strerror(errno));
358 #endif
359 }
360 }
361
362 offset = (long)pagepool_start - rounddown2((long)pagepool_start,
363 pagesz);
364
365 pagepool_start = mmap(0, n * pagesz, PROT_READ | PROT_WRITE,
366 MAP_ANON | MAP_PRIVATE, -1, 0);
367 if (pagepool_start == MAP_FAILED) {
368 #ifdef IN_RTLD
369 rtld_fdprintf(STDERR_FILENO, _BASENAME_RTLD ": morepages: "
370 "cannot mmap anonymous memory: %s\n",
371 rtld_strerror(errno));
372 #endif
373 return (0);
374 }
375 pagepool_end = pagepool_start + n * pagesz;
376 pagepool_start += offset;
377
378 return (n);
379 }
380