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
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19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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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/param.h>
49 #include <sys/sysctl.h>
57 #include "rtld_printf.h"
61 * Pre-allocate mmap'ed pages
63 #define NPOOLPAGES (128*1024/pagesz)
64 static caddr_t pagepool_start, pagepool_end;
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.
77 union overhead *ov_next; /* when free */
79 u_char ovu_magic; /* magic number */
80 u_char ovu_index; /* bucket # */
82 #define ov_magic ovu.ovu_magic
83 #define ov_index ovu.ovu_index
86 static void morecore(int bucket);
87 static int morepages(int n);
89 #define MAGIC 0xef /* magic # on accounting info */
92 * nextf[i] is the pointer to the next free block of size 2^(i+3). The
93 * smallest allocatable block is 8 bytes. The overhead information
94 * precedes the data area returned to the user.
97 static union overhead *nextf[NBUCKETS];
99 static int pagesz; /* page size */
100 static int pagebucket; /* page size bucket */
103 * The array of supported page sizes is provided by the user, i.e., the
104 * program that calls this storage allocator. That program must initialize
105 * the array before making its first call to allocate storage. The array
106 * must contain at least one page size. The page sizes must be stored in
111 __crt_malloc(size_t nbytes)
119 * First time malloc is called, setup page size and
120 * align break pointer so all data will be page aligned.
123 pagesz = n = pagesizes[0];
124 if (morepages(NPOOLPAGES) == 0)
126 op = (union overhead *)(pagepool_start);
127 n = n - sizeof (*op) - ((long)op & (n - 1));
135 while ((unsigned)pagesz > amt) {
142 * Convert amount of memory requested into closest block size
143 * stored in hash buckets which satisfies request.
144 * Account for space used per block for accounting.
146 if (nbytes <= (unsigned long)(n = pagesz - sizeof(*op))) {
147 amt = 8; /* size of first bucket */
154 while (nbytes > amt + n) {
161 * If nothing in hash bucket right now,
162 * request more memory from the system.
164 if ((op = nextf[bucket]) == NULL) {
166 if ((op = nextf[bucket]) == NULL)
169 /* remove from linked list */
170 nextf[bucket] = op->ov_next;
171 op->ov_magic = MAGIC;
172 op->ov_index = bucket;
173 return ((char *)(op + 1));
177 __crt_calloc(size_t num, size_t size)
181 if (size != 0 && (num * size) / size != num) {
182 /* size_t overflow. */
186 if ((ret = __crt_malloc(num * size)) != NULL)
187 memset(ret, 0, num * size);
193 * Allocate more memory to the indicated bucket.
199 int sz; /* size of desired block */
200 int amt; /* amount to allocate */
201 int nblks; /* how many blocks we get */
204 * sbrk_size <= 0 only for big, FLUFFY, requests (about
205 * 2^30 bytes on a VAX, I think) or for a negative arg.
207 if ((unsigned)bucket >= NBBY * sizeof(int) - 4)
209 sz = 1 << (bucket + 3);
217 if (amt > pagepool_end - pagepool_start)
218 if (morepages(amt/pagesz + NPOOLPAGES) == 0)
220 op = (union overhead *)pagepool_start;
221 pagepool_start += amt;
224 * Add new memory allocated to that on
225 * free list for this hash bucket.
228 while (--nblks > 0) {
229 op->ov_next = (union overhead *)((caddr_t)op + sz);
230 op = (union overhead *)((caddr_t)op + sz);
242 op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
243 if (op->ov_magic != MAGIC)
246 op->ov_next = nextf[size]; /* also clobbers ov_magic */
251 __crt_realloc(void *cp, size_t nbytes)
259 return (__crt_malloc(nbytes));
260 op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
261 if (op->ov_magic != MAGIC)
262 return (NULL); /* Double-free or bad argument */
265 if (onb < (u_int)pagesz)
268 onb += pagesz - sizeof(*op);
269 /* avoid the copy if same size block */
275 i += pagesz - sizeof(*op);
277 if (nbytes <= onb && nbytes > (size_t)i)
279 if ((res = __crt_malloc(nbytes)) == NULL)
281 bcopy(cp, res, (nbytes < onb) ? nbytes : onb);
292 if (pagepool_end - pagepool_start > pagesz) {
293 addr = (caddr_t)roundup2((long)pagepool_start, pagesz);
294 if (munmap(addr, pagepool_end - addr) != 0) {
296 rtld_fdprintf(STDERR_FILENO, _BASENAME_RTLD ": "
297 "morepages: cannot munmap %p: %s\n",
298 addr, rtld_strerror(errno));
303 offset = (long)pagepool_start - rounddown2((long)pagepool_start,
306 pagepool_start = mmap(0, n * pagesz, PROT_READ | PROT_WRITE,
307 MAP_ANON | MAP_PRIVATE, -1, 0);
308 if (pagepool_start == MAP_FAILED) {
310 rtld_fdprintf(STDERR_FILENO, _BASENAME_RTLD ": morepages: "
311 "cannot mmap anonymous memory: %s\n",
312 rtld_strerror(errno));
316 pagepool_end = pagepool_start + n * pagesz;
317 pagepool_start += offset;