2 * SPDX-License-Identifier: BSD-3-Clause
4 * Copyright (c) 1983 Regents of the University of California.
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8 * modification, are permitted provided that the following conditions
10 * 1. Redistributions of source code must retain the above copyright
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16 * may be used to endorse or promote products derived from this software
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19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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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 */
38 * malloc.c (Caltech) 2/21/82
39 * Chris Kingsley, kingsley@cit-20.
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.
48 #include <sys/types.h>
49 #include <sys/sysctl.h>
57 #include <sys/param.h>
60 #include "rtld_printf.h"
64 * Pre-allocate mmap'ed pages
66 #define NPOOLPAGES (128*1024/pagesz)
67 static caddr_t pagepool_start, pagepool_end;
70 * The overhead on a block is at least 4 bytes. When free, this space
71 * contains a pointer to the next free block, and the bottom two bits must
72 * be zero. When in use, the first byte is set to MAGIC, and the second
73 * byte is the size index. The remaining bytes are for alignment.
74 * If range checking is enabled then a second word holds the size of the
75 * requested block, less 1, rounded up to a multiple of sizeof(RMAGIC).
76 * The order of elements is critical: ov_magic must overlay the low order
77 * bits of ov_next, and ov_magic can not be a valid ov_next bit pattern.
80 union overhead *ov_next; /* when free */
82 u_char ovu_magic; /* magic number */
83 u_char ovu_index; /* bucket # */
85 u_short ovu_rmagic; /* range magic number */
86 u_int ovu_size; /* actual block size */
89 #define ov_magic ovu.ovu_magic
90 #define ov_index ovu.ovu_index
91 #define ov_rmagic ovu.ovu_rmagic
92 #define ov_size ovu.ovu_size
95 static void morecore(int bucket);
96 static int morepages(int n);
97 static int findbucket(union overhead *freep, int srchlen);
100 #define MAGIC 0xef /* magic # on accounting info */
101 #define RMAGIC 0x5555 /* magic # on range info */
104 #define RSLOP sizeof (u_short)
110 * nextf[i] is the pointer to the next free block of size 2^(i+3). The
111 * smallest allocatable block is 8 bytes. The overhead information
112 * precedes the data area returned to the user.
115 static union overhead *nextf[NBUCKETS];
117 static int pagesz; /* page size */
118 static int pagebucket; /* page size bucket */
122 * nmalloc[i] is the difference between the number of mallocs and frees
123 * for a given block size.
125 static u_int nmalloc[NBUCKETS];
129 #if defined(MALLOC_DEBUG) || defined(RCHECK)
130 #define ASSERT(p) if (!(p)) botch("p")
136 fprintf(stderr, "\r\nassertion botched: %s\r\n", s);
137 (void) fflush(stderr); /* just in case user buffered it */
144 /* Debugging stuff */
145 #define TRACE() rtld_printf("TRACE %s:%d\n", __FILE__, __LINE__)
148 * The array of supported page sizes is provided by the user, i.e., the
149 * program that calls this storage allocator. That program must initialize
150 * the array before making its first call to allocate storage. The array
151 * must contain at least one page size. The page sizes must be stored in
156 __crt_malloc(size_t nbytes)
164 * First time malloc is called, setup page size and
165 * align break pointer so all data will be page aligned.
168 pagesz = n = pagesizes[0];
169 if (morepages(NPOOLPAGES) == 0)
171 op = (union overhead *)(pagepool_start);
172 n = n - sizeof (*op) - ((long)op & (n - 1));
180 while ((unsigned)pagesz > amt) {
187 * Convert amount of memory requested into closest block size
188 * stored in hash buckets which satisfies request.
189 * Account for space used per block for accounting.
191 if (nbytes <= (unsigned long)(n = pagesz - sizeof (*op) - RSLOP)) {
193 amt = 8; /* size of first bucket */
196 amt = 16; /* size of first bucket */
199 n = -(sizeof (*op) + RSLOP);
204 while (nbytes > amt + n) {
211 * If nothing in hash bucket right now,
212 * request more memory from the system.
214 if ((op = nextf[bucket]) == NULL) {
216 if ((op = nextf[bucket]) == NULL)
219 /* remove from linked list */
220 nextf[bucket] = op->ov_next;
221 op->ov_magic = MAGIC;
222 op->ov_index = bucket;
228 * Record allocated size of block and
229 * bound space with magic numbers.
231 op->ov_size = roundup2(nbytes, RSLOP);
232 op->ov_rmagic = RMAGIC;
233 *(u_short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC;
235 return ((char *)(op + 1));
239 __crt_calloc(size_t num, size_t size)
243 if (size != 0 && (num * size) / size != num) {
244 /* size_t overflow. */
248 if ((ret = __crt_malloc(num * size)) != NULL)
249 memset(ret, 0, num * size);
255 * Allocate more memory to the indicated bucket.
261 int sz; /* size of desired block */
262 int amt; /* amount to allocate */
263 int nblks; /* how many blocks we get */
266 * sbrk_size <= 0 only for big, FLUFFY, requests (about
267 * 2^30 bytes on a VAX, I think) or for a negative arg.
269 sz = 1 << (bucket + 3);
283 if (amt > pagepool_end - pagepool_start)
284 if (morepages(amt/pagesz + NPOOLPAGES) == 0)
286 op = (union overhead *)pagepool_start;
287 pagepool_start += amt;
290 * Add new memory allocated to that on
291 * free list for this hash bucket.
294 while (--nblks > 0) {
295 op->ov_next = (union overhead *)((caddr_t)op + sz);
296 op = (union overhead *)((caddr_t)op + sz);
308 op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
310 ASSERT(op->ov_magic == MAGIC); /* make sure it was in use */
312 if (op->ov_magic != MAGIC)
316 ASSERT(op->ov_rmagic == RMAGIC);
317 ASSERT(*(u_short *)((caddr_t)(op + 1) + op->ov_size) == RMAGIC);
320 ASSERT(size < NBUCKETS);
321 op->ov_next = nextf[size]; /* also clobbers ov_magic */
329 * When a program attempts "storage compaction" as mentioned in the
330 * old malloc man page, it realloc's an already freed block. Usually
331 * this is the last block it freed; occasionally it might be farther
332 * back. We have to search all the free lists for the block in order
333 * to determine its bucket: 1st we make one pass through the lists
334 * checking only the first block in each; if that fails we search
335 * ``realloc_srchlen'' blocks in each list for a match (the variable
336 * is extern so the caller can modify it). If that fails we just copy
337 * however many bytes was given to realloc() and hope it's not huge.
339 static int realloc_srchlen = 4; /* 4 should be plenty, -1 =>'s whole list */
342 __crt_realloc(void *cp, size_t nbytes)
351 return (__crt_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 = __crt_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(union overhead *freep, int srchlen)
416 for (i = 0; i < NBUCKETS; i++) {
418 for (p = nextf[i]; p && j != srchlen; p = p->ov_next) {
429 * mstats - print out statistics about malloc
431 * Prints two lines of numbers, one showing the length of the free list
432 * for each size category, the second showing the number of mallocs -
433 * frees for each size category.
442 fprintf(stderr, "Memory allocation statistics %s\nfree:\t", s);
443 for (i = 0; i < NBUCKETS; i++) {
444 for (j = 0, p = nextf[i]; p; p = p->ov_next, j++)
446 fprintf(stderr, " %d", j);
447 totfree += j * (1 << (i + 3));
449 fprintf(stderr, "\nused:\t");
450 for (i = 0; i < NBUCKETS; i++) {
451 fprintf(stderr, " %d", nmalloc[i]);
452 totused += nmalloc[i] * (1 << (i + 3));
454 fprintf(stderr, "\n\tTotal in use: %d, total free: %d\n",
466 if (pagepool_end - pagepool_start > pagesz) {
467 caddr_t addr = (caddr_t)
468 (((long)pagepool_start + pagesz - 1) & ~(pagesz - 1));
469 if (munmap(addr, pagepool_end - addr) != 0) {
471 rtld_fdprintf(STDERR_FILENO, _BASENAME_RTLD ": "
472 "morepages: cannot munmap %p: %s\n",
473 addr, rtld_strerror(errno));
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_PRIVATE, fd, 0)) == (caddr_t)-1) {
484 rtld_fdprintf(STDERR_FILENO, _BASENAME_RTLD ": morepages: "
485 "cannot mmap anonymous memory: %s\n",
486 rtld_strerror(errno));
490 pagepool_end = pagepool_start + n * pagesz;
491 pagepool_start += offset;