2 * Copyright (c) 1983 Regents of the University of California.
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6 * modification, are permitted provided that the following conditions
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13 * 3. All advertising materials mentioning features or use of this software
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15 * This product includes software developed by the University of
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18 * may be used to endorse or promote products derived from this software
19 * without specific prior written permission.
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22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
33 * @(#)malloc.c 5.11 (Berkeley) 2/23/91
34 * $FreeBSD: src/libexec/rtld-elf/malloc.c,v 1.3.2.3 2003/02/20 20:42:46 kan Exp $
35 * $DragonFly: src/libexec/rtld-elf/malloc.c,v 1.2 2003/06/17 04:27:08 dillon Exp $
39 * malloc.c (Caltech) 2/21/82
40 * Chris Kingsley, kingsley@cit-20.
42 * This is a very fast storage allocator. It allocates blocks of a small
43 * number of different sizes, and keeps free lists of each size. Blocks that
44 * don't exactly fit are passed up to the next larger size. In this
45 * implementation, the available sizes are 2^n-4 (or 2^n-10) bytes long.
46 * This is designed for use in a virtual memory environment.
49 #include <sys/types.h>
57 #include <sys/param.h>
60 #define MAP_COPY MAP_PRIVATE
65 #ifndef BSD /* Need do better than this */
66 #define NEED_DEV_ZERO 1
71 static void morecore();
72 static int findbucket();
75 * Pre-allocate mmap'ed pages
77 #define NPOOLPAGES (32*1024/pagesz)
78 static caddr_t pagepool_start, pagepool_end;
79 static int morepages();
82 * The overhead on a block is at least 4 bytes. When free, this space
83 * contains a pointer to the next free block, and the bottom two bits must
84 * be zero. When in use, the first byte is set to MAGIC, and the second
85 * byte is the size index. The remaining bytes are for alignment.
86 * If range checking is enabled then a second word holds the size of the
87 * requested block, less 1, rounded up to a multiple of sizeof(RMAGIC).
88 * The order of elements is critical: ov_magic must overlay the low order
89 * bits of ov_next, and ov_magic can not be a valid ov_next bit pattern.
92 union overhead *ov_next; /* when free */
94 u_char ovu_magic; /* magic number */
95 u_char ovu_index; /* bucket # */
97 u_short ovu_rmagic; /* range magic number */
98 u_int ovu_size; /* actual block size */
101 #define ov_magic ovu.ovu_magic
102 #define ov_index ovu.ovu_index
103 #define ov_rmagic ovu.ovu_rmagic
104 #define ov_size ovu.ovu_size
107 #define MAGIC 0xef /* magic # on accounting info */
108 #define RMAGIC 0x5555 /* magic # on range info */
111 #define RSLOP sizeof (u_short)
117 * nextf[i] is the pointer to the next free block of size 2^(i+3). The
118 * smallest allocatable block is 8 bytes. The overhead information
119 * precedes the data area returned to the user.
122 static union overhead *nextf[NBUCKETS];
124 static int pagesz; /* page size */
125 static int pagebucket; /* page size bucket */
129 * nmalloc[i] is the difference between the number of mallocs and frees
130 * for a given block size.
132 static u_int nmalloc[NBUCKETS];
136 #if defined(MALLOC_DEBUG) || defined(RCHECK)
137 #define ASSERT(p) if (!(p)) botch("p")
143 fprintf(stderr, "\r\nassertion botched: %s\r\n", s);
144 (void) fflush(stderr); /* just in case user buffered it */
151 /* Debugging stuff */
152 static void xprintf(const char *, ...);
153 #define TRACE() xprintf("TRACE %s:%d\n", __FILE__, __LINE__)
159 register union overhead *op;
162 register unsigned amt;
165 * First time malloc is called, setup page size and
166 * align break pointer so all data will be page aligned.
169 pagesz = n = getpagesize();
170 if (morepages(NPOOLPAGES) == 0)
172 op = (union overhead *)(pagepool_start);
173 n = n - sizeof (*op) - ((long)op & (n - 1));
181 while (pagesz > amt) {
188 * Convert amount of memory requested into closest block size
189 * stored in hash buckets which satisfies request.
190 * Account for space used per block for accounting.
192 if (nbytes <= (n = pagesz - sizeof (*op) - RSLOP)) {
194 amt = 8; /* size of first bucket */
197 amt = 16; /* size of first bucket */
200 n = -(sizeof (*op) + RSLOP);
205 while (nbytes > amt + n) {
212 * If nothing in hash bucket right now,
213 * request more memory from the system.
215 if ((op = nextf[bucket]) == NULL) {
217 if ((op = nextf[bucket]) == NULL)
220 /* remove from linked list */
221 nextf[bucket] = op->ov_next;
222 op->ov_magic = MAGIC;
223 op->ov_index = bucket;
229 * Record allocated size of block and
230 * bound space with magic numbers.
232 op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1);
233 op->ov_rmagic = RMAGIC;
234 *(u_short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC;
236 return ((char *)(op + 1));
240 * Allocate more memory to the indicated bucket.
246 register union overhead *op;
247 register int sz; /* size of desired block */
248 int amt; /* amount to allocate */
249 int nblks; /* how many blocks we get */
252 * sbrk_size <= 0 only for big, FLUFFY, requests (about
253 * 2^30 bytes on a VAX, I think) or for a negative arg.
255 sz = 1 << (bucket + 3);
269 if (amt > pagepool_end - pagepool_start)
270 if (morepages(amt/pagesz + NPOOLPAGES) == 0)
272 op = (union overhead *)pagepool_start;
273 pagepool_start += amt;
276 * Add new memory allocated to that on
277 * free list for this hash bucket.
280 while (--nblks > 0) {
281 op->ov_next = (union overhead *)((caddr_t)op + sz);
282 op = (union overhead *)((caddr_t)op + sz);
291 register union overhead *op;
295 op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
297 ASSERT(op->ov_magic == MAGIC); /* make sure it was in use */
299 if (op->ov_magic != MAGIC)
303 ASSERT(op->ov_rmagic == RMAGIC);
304 ASSERT(*(u_short *)((caddr_t)(op + 1) + op->ov_size) == RMAGIC);
307 ASSERT(size < NBUCKETS);
308 op->ov_next = nextf[size]; /* also clobbers ov_magic */
316 * When a program attempts "storage compaction" as mentioned in the
317 * old malloc man page, it realloc's an already freed block. Usually
318 * this is the last block it freed; occasionally it might be farther
319 * back. We have to search all the free lists for the block in order
320 * to determine its bucket: 1st we make one pass thru the lists
321 * checking only the first block in each; if that fails we search
322 * ``realloc_srchlen'' blocks in each list for a match (the variable
323 * is extern so the caller can modify it). If that fails we just copy
324 * however many bytes was given to realloc() and hope it's not huge.
326 int realloc_srchlen = 4; /* 4 should be plenty, -1 =>'s whole list */
340 return (malloc(nbytes));
341 op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
342 if (op->ov_magic == MAGIC) {
347 * Already free, doing "compaction".
349 * Search for the old block of memory on the
350 * free list. First, check the most common
351 * case (last element free'd), then (this failing)
352 * the last ``realloc_srchlen'' items free'd.
353 * If all lookups fail, then assume the size of
354 * the memory block being realloc'd is the
355 * largest possible (so that all "nbytes" of new
356 * memory are copied into). Note that this could cause
357 * a memory fault if the old area was tiny, and the moon
358 * is gibbous. However, that is very unlikely.
360 if ((i = findbucket(op, 1)) < 0 &&
361 (i = findbucket(op, realloc_srchlen)) < 0)
366 onb -= sizeof (*op) + RSLOP;
368 onb += pagesz - sizeof (*op) - RSLOP;
369 /* avoid the copy if same size block */
374 i -= sizeof (*op) + RSLOP;
376 i += pagesz - sizeof (*op) - RSLOP;
378 if (nbytes <= onb && nbytes > i) {
380 op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1);
381 *(u_short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC;
387 if ((res = malloc(nbytes)) == NULL)
389 if (cp != res) /* common optimization if "compacting" */
390 bcopy(cp, res, (nbytes < onb) ? nbytes : onb);
395 * Search ``srchlen'' elements of each free list for a block whose
396 * header starts at ``freep''. If srchlen is -1 search the whole list.
397 * Return bucket number, or -1 if not found.
400 findbucket(freep, srchlen)
401 union overhead *freep;
404 register union overhead *p;
407 for (i = 0; i < NBUCKETS; i++) {
409 for (p = nextf[i]; p && j != srchlen; p = p->ov_next) {
420 * mstats - print out statistics about malloc
422 * Prints two lines of numbers, one showing the length of the free list
423 * for each size category, the second showing the number of mallocs -
424 * frees for each size category.
430 register union overhead *p;
434 fprintf(stderr, "Memory allocation statistics %s\nfree:\t", s);
435 for (i = 0; i < NBUCKETS; i++) {
436 for (j = 0, p = nextf[i]; p; p = p->ov_next, j++)
438 fprintf(stderr, " %d", j);
439 totfree += j * (1 << (i + 3));
441 fprintf(stderr, "\nused:\t");
442 for (i = 0; i < NBUCKETS; i++) {
443 fprintf(stderr, " %d", nmalloc[i]);
444 totused += nmalloc[i] * (1 << (i + 3));
446 fprintf(stderr, "\n\tTotal in use: %d, total free: %d\n",
460 fd = open(_PATH_DEVZERO, O_RDWR, 0);
462 perror(_PATH_DEVZERO);
465 if (pagepool_end - pagepool_start > pagesz) {
466 caddr_t addr = (caddr_t)
467 (((long)pagepool_start + pagesz - 1) & ~(pagesz - 1));
468 if (munmap(addr, pagepool_end - addr) != 0)
469 warn("morepages: munmap %p", addr);
472 offset = (long)pagepool_start - ((long)pagepool_start & ~(pagesz - 1));
474 if ((pagepool_start = mmap(0, n * pagesz,
475 PROT_READ|PROT_WRITE,
476 MAP_ANON|MAP_COPY, fd, 0)) == (caddr_t)-1) {
477 xprintf("Cannot map anonymous memory");
480 pagepool_end = pagepool_start + n * pagesz;
481 pagepool_start += offset;
490 * Non-mallocing printf, for use by malloc itself.
493 xprintf(const char *fmt, ...)
499 vsprintf(buf, fmt, ap);
500 (void)write(STDOUT_FILENO, buf, strlen(buf));