2 * Copyright (c) 1983 Regents of the University of California.
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
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.
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)
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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 */
36 * malloc.c (Caltech) 2/21/82
37 * Chris Kingsley, kingsley@cit-20.
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.
46 #include <sys/types.h>
47 #include <sys/sysctl.h>
54 #include <sys/param.h>
56 #include "rtld_printf.h"
58 static void morecore();
59 static int findbucket();
62 * Pre-allocate mmap'ed pages
64 #define NPOOLPAGES (32*1024/pagesz)
65 static caddr_t pagepool_start, pagepool_end;
66 static int morepages();
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.
79 union overhead *ov_next; /* when free */
81 u_char ovu_magic; /* magic number */
82 u_char ovu_index; /* bucket # */
84 u_short ovu_rmagic; /* range magic number */
85 u_int ovu_size; /* actual block size */
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
94 #define MAGIC 0xef /* magic # on accounting info */
95 #define RMAGIC 0x5555 /* magic # on range info */
98 #define RSLOP sizeof (u_short)
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.
109 static union overhead *nextf[NBUCKETS];
111 static int pagesz; /* page size */
112 static int pagebucket; /* page size bucket */
116 * nmalloc[i] is the difference between the number of mallocs and frees
117 * for a given block size.
119 static u_int nmalloc[NBUCKETS];
123 #if defined(MALLOC_DEBUG) || defined(RCHECK)
124 #define ASSERT(p) if (!(p)) botch("p")
130 fprintf(stderr, "\r\nassertion botched: %s\r\n", s);
131 (void) fflush(stderr); /* just in case user buffered it */
138 /* Debugging stuff */
139 #define TRACE() rtld_printf("TRACE %s:%d\n", __FILE__, __LINE__)
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
148 extern size_t *pagesizes;
154 register union overhead *op;
157 register unsigned amt;
160 * First time malloc is called, setup page size and
161 * align break pointer so all data will be page aligned.
164 pagesz = n = pagesizes[0];
165 if (morepages(NPOOLPAGES) == 0)
167 op = (union overhead *)(pagepool_start);
168 n = n - sizeof (*op) - ((long)op & (n - 1));
176 while ((unsigned)pagesz > amt) {
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.
187 if (nbytes <= (unsigned long)(n = pagesz - sizeof (*op) - RSLOP)) {
189 amt = 8; /* size of first bucket */
192 amt = 16; /* size of first bucket */
195 n = -(sizeof (*op) + RSLOP);
200 while (nbytes > amt + n) {
207 * If nothing in hash bucket right now,
208 * request more memory from the system.
210 if ((op = nextf[bucket]) == NULL) {
212 if ((op = nextf[bucket]) == NULL)
215 /* remove from linked list */
216 nextf[bucket] = op->ov_next;
217 op->ov_magic = MAGIC;
218 op->ov_index = bucket;
224 * Record allocated size of block and
225 * bound space with magic numbers.
227 op->ov_size = roundup2(nbytes, RSLOP);
228 op->ov_rmagic = RMAGIC;
229 *(u_short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC;
231 return ((char *)(op + 1));
235 calloc(size_t num, size_t size)
239 if (size != 0 && (num * size) / size != num) {
240 /* size_t overflow. */
244 if ((ret = malloc(num * size)) != NULL)
245 memset(ret, 0, num * size);
251 * Allocate more memory to the indicated bucket.
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 */
263 * sbrk_size <= 0 only for big, FLUFFY, requests (about
264 * 2^30 bytes on a VAX, I think) or for a negative arg.
266 sz = 1 << (bucket + 3);
280 if (amt > pagepool_end - pagepool_start)
281 if (morepages(amt/pagesz + NPOOLPAGES) == 0)
283 op = (union overhead *)pagepool_start;
284 pagepool_start += amt;
287 * Add new memory allocated to that on
288 * free list for this hash bucket.
291 while (--nblks > 0) {
292 op->ov_next = (union overhead *)((caddr_t)op + sz);
293 op = (union overhead *)((caddr_t)op + sz);
302 register union overhead *op;
306 op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
308 ASSERT(op->ov_magic == MAGIC); /* make sure it was in use */
310 if (op->ov_magic != MAGIC)
314 ASSERT(op->ov_rmagic == RMAGIC);
315 ASSERT(*(u_short *)((caddr_t)(op + 1) + op->ov_size) == RMAGIC);
318 ASSERT(size < NBUCKETS);
319 op->ov_next = nextf[size]; /* also clobbers ov_magic */
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 through 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.
337 int realloc_srchlen = 4; /* 4 should be plenty, -1 =>'s whole list */
351 return (malloc(nbytes));
352 op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
353 if (op->ov_magic == MAGIC) {
358 * Already free, doing "compaction".
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.
371 if ((i = findbucket(op, 1)) < 0 &&
372 (i = findbucket(op, realloc_srchlen)) < 0)
376 if (onb < (u_int)pagesz)
377 onb -= sizeof (*op) + RSLOP;
379 onb += pagesz - sizeof (*op) - RSLOP;
380 /* avoid the copy if same size block */
385 i -= sizeof (*op) + RSLOP;
387 i += pagesz - sizeof (*op) - RSLOP;
389 if (nbytes <= onb && nbytes > (size_t)i) {
391 op->ov_size = roundup2(nbytes, RSLOP);
392 *(u_short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC;
398 if ((res = malloc(nbytes)) == NULL)
400 if (cp != res) /* common optimization if "compacting" */
401 bcopy(cp, res, (nbytes < onb) ? nbytes : onb);
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.
411 findbucket(freep, srchlen)
412 union overhead *freep;
415 register union overhead *p;
418 for (i = 0; i < NBUCKETS; i++) {
420 for (p = nextf[i]; p && j != srchlen; p = p->ov_next) {
431 * mstats - print out statistics about malloc
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.
441 register union overhead *p;
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++)
449 fprintf(stderr, " %d", j);
450 totfree += j * (1 << (i + 3));
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));
457 fprintf(stderr, "\n\tTotal in use: %d, total free: %d\n",
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",
478 offset = (long)pagepool_start - ((long)pagepool_start & ~(pagesz - 1));
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");
486 pagepool_end = pagepool_start + n * pagesz;
487 pagepool_start += offset;