1 /*-
2 * Copyright (c) 1983 Regents of the University of California.
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 * 3. Neither the name of the University nor the names of its contributors
14 * may be used to endorse or promote products derived from this software
15 * without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
28 */
29
30 #if defined(LIBC_SCCS) && !defined(lint)
31 /*static char *sccsid = "from: @(#)malloc.c 5.11 (Berkeley) 2/23/91";*/
32 static char *rcsid = "$FreeBSD$";
33 #endif /* LIBC_SCCS and not lint */
34
35 /*
36 * malloc.c (Caltech) 2/21/82
37 * Chris Kingsley, kingsley@cit-20.
38 *
39 * This is a very fast storage allocator. It allocates blocks of a small
40 * number of different sizes, and keeps free lists of each size. Blocks that
41 * don't exactly fit are passed up to the next larger size. In this
42 * implementation, the available sizes are 2^n-4 (or 2^n-10) bytes long.
43 * This is designed for use in a virtual memory environment.
44 */
45
46 #include <sys/types.h>
47 #include <sys/sysctl.h>
48 #include <stdarg.h>
49 #include <stddef.h>
50 #include <stdio.h>
51 #include <stdlib.h>
52 #include <string.h>
53 #include <unistd.h>
54 #include <sys/param.h>
55 #include <sys/mman.h>
56 #include "rtld_printf.h"
57
58 static void morecore();
59 static int findbucket();
60
61 /*
62 * Pre-allocate mmap'ed pages
63 */
64 #define NPOOLPAGES (32*1024/pagesz)
65 static caddr_t pagepool_start, pagepool_end;
66 static int morepages();
67
68 /*
69 * The overhead on a block is at least 4 bytes. When free, this space
70 * contains a pointer to the next free block, and the bottom two bits must
71 * be zero. When in use, the first byte is set to MAGIC, and the second
72 * byte is the size index. The remaining bytes are for alignment.
73 * If range checking is enabled then a second word holds the size of the
74 * requested block, less 1, rounded up to a multiple of sizeof(RMAGIC).
75 * The order of elements is critical: ov_magic must overlay the low order
76 * bits of ov_next, and ov_magic can not be a valid ov_next bit pattern.
77 */
78 union overhead {
79 union overhead *ov_next; /* when free */
80 struct {
81 u_char ovu_magic; /* magic number */
82 u_char ovu_index; /* bucket # */
83 #ifdef RCHECK
84 u_short ovu_rmagic; /* range magic number */
85 u_int ovu_size; /* actual block size */
86 #endif
87 } ovu;
88 #define ov_magic ovu.ovu_magic
89 #define ov_index ovu.ovu_index
90 #define ov_rmagic ovu.ovu_rmagic
91 #define ov_size ovu.ovu_size
92 };
93
94 #define MAGIC 0xef /* magic # on accounting info */
95 #define RMAGIC 0x5555 /* magic # on range info */
96
97 #ifdef RCHECK
98 #define RSLOP sizeof (u_short)
99 #else
100 #define RSLOP 0
101 #endif
102
103 /*
104 * nextf[i] is the pointer to the next free block of size 2^(i+3). The
105 * smallest allocatable block is 8 bytes. The overhead information
106 * precedes the data area returned to the user.
107 */
108 #define NBUCKETS 30
109 static union overhead *nextf[NBUCKETS];
110
111 static int pagesz; /* page size */
112 static int pagebucket; /* page size bucket */
113
114 #ifdef MSTATS
115 /*
116 * nmalloc[i] is the difference between the number of mallocs and frees
117 * for a given block size.
118 */
119 static u_int nmalloc[NBUCKETS];
120 #include <stdio.h>
121 #endif
122
123 #if defined(MALLOC_DEBUG) || defined(RCHECK)
124 #define ASSERT(p) if (!(p)) botch("p")
125 #include <stdio.h>
126 static void
botch(s)127 botch(s)
128 char *s;
129 {
130 fprintf(stderr, "\r\nassertion botched: %s\r\n", s);
131 (void) fflush(stderr); /* just in case user buffered it */
132 abort();
133 }
134 #else
135 #define ASSERT(p)
136 #endif
137
138 /* Debugging stuff */
139 #define TRACE() rtld_printf("TRACE %s:%d\n", __FILE__, __LINE__)
140
141 /*
142 * The array of supported page sizes is provided by the user, i.e., the
143 * program that calls this storage allocator. That program must initialize
144 * the array before making its first call to allocate storage. The array
145 * must contain at least one page size. The page sizes must be stored in
146 * increasing order.
147 */
148 extern size_t *pagesizes;
149
150 void *
malloc(nbytes)151 malloc(nbytes)
152 size_t nbytes;
153 {
154 register union overhead *op;
155 register int bucket;
156 register long n;
157 register unsigned amt;
158
159 /*
160 * First time malloc is called, setup page size and
161 * align break pointer so all data will be page aligned.
162 */
163 if (pagesz == 0) {
164 pagesz = n = pagesizes[0];
165 if (morepages(NPOOLPAGES) == 0)
166 return NULL;
167 op = (union overhead *)(pagepool_start);
168 n = n - sizeof (*op) - ((long)op & (n - 1));
169 if (n < 0)
170 n += pagesz;
171 if (n) {
172 pagepool_start += n;
173 }
174 bucket = 0;
175 amt = 8;
176 while ((unsigned)pagesz > amt) {
177 amt <<= 1;
178 bucket++;
179 }
180 pagebucket = bucket;
181 }
182 /*
183 * Convert amount of memory requested into closest block size
184 * stored in hash buckets which satisfies request.
185 * Account for space used per block for accounting.
186 */
187 if (nbytes <= (unsigned long)(n = pagesz - sizeof (*op) - RSLOP)) {
188 #ifndef RCHECK
189 amt = 8; /* size of first bucket */
190 bucket = 0;
191 #else
192 amt = 16; /* size of first bucket */
193 bucket = 1;
194 #endif
195 n = -(sizeof (*op) + RSLOP);
196 } else {
197 amt = pagesz;
198 bucket = pagebucket;
199 }
200 while (nbytes > amt + n) {
201 amt <<= 1;
202 if (amt == 0)
203 return (NULL);
204 bucket++;
205 }
206 /*
207 * If nothing in hash bucket right now,
208 * request more memory from the system.
209 */
210 if ((op = nextf[bucket]) == NULL) {
211 morecore(bucket);
212 if ((op = nextf[bucket]) == NULL)
213 return (NULL);
214 }
215 /* remove from linked list */
216 nextf[bucket] = op->ov_next;
217 op->ov_magic = MAGIC;
218 op->ov_index = bucket;
219 #ifdef MSTATS
220 nmalloc[bucket]++;
221 #endif
222 #ifdef RCHECK
223 /*
224 * Record allocated size of block and
225 * bound space with magic numbers.
226 */
227 op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1);
228 op->ov_rmagic = RMAGIC;
229 *(u_short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC;
230 #endif
231 return ((char *)(op + 1));
232 }
233
234 void *
calloc(size_t num,size_t size)235 calloc(size_t num, size_t size)
236 {
237 void *ret;
238
239 if (size != 0 && (num * size) / size != num) {
240 /* size_t overflow. */
241 return (NULL);
242 }
243
244 if ((ret = malloc(num * size)) != NULL)
245 memset(ret, 0, num * size);
246
247 return (ret);
248 }
249
250 /*
251 * Allocate more memory to the indicated bucket.
252 */
253 static void
morecore(bucket)254 morecore(bucket)
255 int bucket;
256 {
257 register union overhead *op;
258 register int sz; /* size of desired block */
259 int amt; /* amount to allocate */
260 int nblks; /* how many blocks we get */
261
262 /*
263 * sbrk_size <= 0 only for big, FLUFFY, requests (about
264 * 2^30 bytes on a VAX, I think) or for a negative arg.
265 */
266 sz = 1 << (bucket + 3);
267 #ifdef MALLOC_DEBUG
268 ASSERT(sz > 0);
269 #else
270 if (sz <= 0)
271 return;
272 #endif
273 if (sz < pagesz) {
274 amt = pagesz;
275 nblks = amt / sz;
276 } else {
277 amt = sz + pagesz;
278 nblks = 1;
279 }
280 if (amt > pagepool_end - pagepool_start)
281 if (morepages(amt/pagesz + NPOOLPAGES) == 0)
282 return;
283 op = (union overhead *)pagepool_start;
284 pagepool_start += amt;
285
286 /*
287 * Add new memory allocated to that on
288 * free list for this hash bucket.
289 */
290 nextf[bucket] = op;
291 while (--nblks > 0) {
292 op->ov_next = (union overhead *)((caddr_t)op + sz);
293 op = (union overhead *)((caddr_t)op + sz);
294 }
295 }
296
297 void
free(cp)298 free(cp)
299 void *cp;
300 {
301 register int size;
302 register union overhead *op;
303
304 if (cp == NULL)
305 return;
306 op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
307 #ifdef MALLOC_DEBUG
308 ASSERT(op->ov_magic == MAGIC); /* make sure it was in use */
309 #else
310 if (op->ov_magic != MAGIC)
311 return; /* sanity */
312 #endif
313 #ifdef RCHECK
314 ASSERT(op->ov_rmagic == RMAGIC);
315 ASSERT(*(u_short *)((caddr_t)(op + 1) + op->ov_size) == RMAGIC);
316 #endif
317 size = op->ov_index;
318 ASSERT(size < NBUCKETS);
319 op->ov_next = nextf[size]; /* also clobbers ov_magic */
320 nextf[size] = op;
321 #ifdef MSTATS
322 nmalloc[size]--;
323 #endif
324 }
325
326 /*
327 * When a program attempts "storage compaction" as mentioned in the
328 * old malloc man page, it realloc's an already freed block. Usually
329 * this is the last block it freed; occasionally it might be farther
330 * back. We have to search all the free lists for the block in order
331 * to determine its bucket: 1st we make one pass thru the lists
332 * checking only the first block in each; if that fails we search
333 * ``realloc_srchlen'' blocks in each list for a match (the variable
334 * is extern so the caller can modify it). If that fails we just copy
335 * however many bytes was given to realloc() and hope it's not huge.
336 */
337 int realloc_srchlen = 4; /* 4 should be plenty, -1 =>'s whole list */
338
339 void *
realloc(cp,nbytes)340 realloc(cp, nbytes)
341 void *cp;
342 size_t nbytes;
343 {
344 register u_int onb;
345 register int i;
346 union overhead *op;
347 char *res;
348 int was_alloced = 0;
349
350 if (cp == NULL)
351 return (malloc(nbytes));
352 op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
353 if (op->ov_magic == MAGIC) {
354 was_alloced++;
355 i = op->ov_index;
356 } else {
357 /*
358 * Already free, doing "compaction".
359 *
360 * Search for the old block of memory on the
361 * free list. First, check the most common
362 * case (last element free'd), then (this failing)
363 * the last ``realloc_srchlen'' items free'd.
364 * If all lookups fail, then assume the size of
365 * the memory block being realloc'd is the
366 * largest possible (so that all "nbytes" of new
367 * memory are copied into). Note that this could cause
368 * a memory fault if the old area was tiny, and the moon
369 * is gibbous. However, that is very unlikely.
370 */
371 if ((i = findbucket(op, 1)) < 0 &&
372 (i = findbucket(op, realloc_srchlen)) < 0)
373 i = NBUCKETS;
374 }
375 onb = 1 << (i + 3);
376 if (onb < (u_int)pagesz)
377 onb -= sizeof (*op) + RSLOP;
378 else
379 onb += pagesz - sizeof (*op) - RSLOP;
380 /* avoid the copy if same size block */
381 if (was_alloced) {
382 if (i) {
383 i = 1 << (i + 2);
384 if (i < pagesz)
385 i -= sizeof (*op) + RSLOP;
386 else
387 i += pagesz - sizeof (*op) - RSLOP;
388 }
389 if (nbytes <= onb && nbytes > (size_t)i) {
390 #ifdef RCHECK
391 op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1);
392 *(u_short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC;
393 #endif
394 return(cp);
395 } else
396 free(cp);
397 }
398 if ((res = malloc(nbytes)) == NULL)
399 return (NULL);
400 if (cp != res) /* common optimization if "compacting" */
401 bcopy(cp, res, (nbytes < onb) ? nbytes : onb);
402 return (res);
403 }
404
405 /*
406 * Search ``srchlen'' elements of each free list for a block whose
407 * header starts at ``freep''. If srchlen is -1 search the whole list.
408 * Return bucket number, or -1 if not found.
409 */
410 static int
findbucket(freep,srchlen)411 findbucket(freep, srchlen)
412 union overhead *freep;
413 int srchlen;
414 {
415 register union overhead *p;
416 register int i, j;
417
418 for (i = 0; i < NBUCKETS; i++) {
419 j = 0;
420 for (p = nextf[i]; p && j != srchlen; p = p->ov_next) {
421 if (p == freep)
422 return (i);
423 j++;
424 }
425 }
426 return (-1);
427 }
428
429 #ifdef MSTATS
430 /*
431 * mstats - print out statistics about malloc
432 *
433 * Prints two lines of numbers, one showing the length of the free list
434 * for each size category, the second showing the number of mallocs -
435 * frees for each size category.
436 */
mstats(s)437 mstats(s)
438 char *s;
439 {
440 register int i, j;
441 register union overhead *p;
442 int totfree = 0,
443 totused = 0;
444
445 fprintf(stderr, "Memory allocation statistics %s\nfree:\t", s);
446 for (i = 0; i < NBUCKETS; i++) {
447 for (j = 0, p = nextf[i]; p; p = p->ov_next, j++)
448 ;
449 fprintf(stderr, " %d", j);
450 totfree += j * (1 << (i + 3));
451 }
452 fprintf(stderr, "\nused:\t");
453 for (i = 0; i < NBUCKETS; i++) {
454 fprintf(stderr, " %d", nmalloc[i]);
455 totused += nmalloc[i] * (1 << (i + 3));
456 }
457 fprintf(stderr, "\n\tTotal in use: %d, total free: %d\n",
458 totused, totfree);
459 }
460 #endif
461
462
463 static int
morepages(n)464 morepages(n)
465 int n;
466 {
467 int fd = -1;
468 int offset;
469
470 if (pagepool_end - pagepool_start > pagesz) {
471 caddr_t addr = (caddr_t)
472 (((long)pagepool_start + pagesz - 1) & ~(pagesz - 1));
473 if (munmap(addr, pagepool_end - addr) != 0)
474 rtld_fdprintf(STDERR_FILENO, "morepages: munmap %p",
475 addr);
476 }
477
478 offset = (long)pagepool_start - ((long)pagepool_start & ~(pagesz - 1));
479
480 if ((pagepool_start = mmap(0, n * pagesz,
481 PROT_READ|PROT_WRITE,
482 MAP_ANON|MAP_COPY, fd, 0)) == (caddr_t)-1) {
483 rtld_printf("Cannot map anonymous memory\n");
484 return 0;
485 }
486 pagepool_end = pagepool_start + n * pagesz;
487 pagepool_start += offset;
488
489 return n;
490 }
491