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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15 * This product includes software developed by the University of
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24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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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, svn 114625 2003/05/04 obrien Exp $
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>
56 #include <sys/param.h>
59 #define MAP_COPY MAP_PRIVATE
64 #ifndef BSD /* Need do better than this */
65 #define NEED_DEV_ZERO 1
68 static void morecore();
69 static int findbucket();
70 static void xprintf(const char *, ...) __printflike(1, 2);
73 * Pre-allocate mmap'ed pages
75 #define NPOOLPAGES (32*1024/pagesz)
76 static caddr_t pagepool_start, pagepool_end;
77 static int morepages();
80 * The overhead on a block is at least 4 bytes. When free, this space
81 * contains a pointer to the next free block, and the bottom two bits must
82 * be zero. When in use, the first byte is set to MAGIC, and the second
83 * byte is the size index. The remaining bytes are for alignment.
84 * If range checking is enabled then a second word holds the size of the
85 * requested block, less 1, rounded up to a multiple of sizeof(RMAGIC).
86 * The order of elements is critical: ov_magic must overlay the low order
87 * bits of ov_next, and ov_magic can not be a valid ov_next bit pattern.
90 union overhead *ov_next; /* when free */
92 u_char ovu_magic; /* magic number */
93 u_char ovu_index; /* bucket # */
95 u_short ovu_rmagic; /* range magic number */
96 u_int ovu_size; /* actual block size */
99 #define ov_magic ovu.ovu_magic
100 #define ov_index ovu.ovu_index
101 #define ov_rmagic ovu.ovu_rmagic
102 #define ov_size ovu.ovu_size
105 #define MAGIC 0xef /* magic # on accounting info */
106 #define RMAGIC 0x5555 /* magic # on range info */
109 #define RSLOP sizeof (u_short)
115 * nextf[i] is the pointer to the next free block of size 2^(i+3). The
116 * smallest allocatable block is 8 bytes. The overhead information
117 * precedes the data area returned to the user.
120 static union overhead *nextf[NBUCKETS];
122 static int pagesz; /* page size */
123 static int pagebucket; /* page size bucket */
127 * nmalloc[i] is the difference between the number of mallocs and frees
128 * for a given block size.
130 static u_int nmalloc[NBUCKETS];
134 #if defined(MALLOC_DEBUG) || defined(RCHECK)
135 #define ASSERT(p) if (!(p)) botch("p")
141 fprintf(stderr, "\r\nassertion botched: %s\r\n", s);
142 (void) fflush(stderr); /* just in case user buffered it */
149 /* Debugging stuff */
150 static void xprintf(const char *, ...);
151 #define TRACE() xprintf("TRACE %s:%d\n", __FILE__, __LINE__)
157 register union overhead *op;
160 register unsigned amt;
163 * First time malloc is called, setup page size and
164 * align break pointer so all data will be page aligned.
167 pagesz = n = getpagesize();
168 if (morepages(NPOOLPAGES) == 0)
170 op = (union overhead *)(pagepool_start);
171 n = n - sizeof (*op) - ((long)op & (n - 1));
179 while ((unsigned)pagesz > amt) {
186 * Convert amount of memory requested into closest block size
187 * stored in hash buckets which satisfies request.
188 * Account for space used per block for accounting.
190 if (nbytes <= (unsigned long)(n = pagesz - sizeof (*op) - RSLOP)) {
192 amt = 8; /* size of first bucket */
195 amt = 16; /* size of first bucket */
198 n = -(sizeof (*op) + RSLOP);
203 while (nbytes > amt + n) {
210 * If nothing in hash bucket right now,
211 * request more memory from the system.
213 if ((op = nextf[bucket]) == NULL) {
215 if ((op = nextf[bucket]) == NULL)
218 /* remove from linked list */
219 nextf[bucket] = op->ov_next;
220 op->ov_magic = MAGIC;
221 op->ov_index = bucket;
227 * Record allocated size of block and
228 * bound space with magic numbers.
230 op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1);
231 op->ov_rmagic = RMAGIC;
232 *(u_short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC;
234 return ((char *)(op + 1));
238 * Used by rtld.c, if we don't override it here the calloc from
239 * libc may try to pull in the malloc/realloc/free from libc too.
242 calloc(size_t num, size_t size)
247 if ((p = malloc(size)) != NULL)
253 * Allocate more memory to the indicated bucket.
259 register union overhead *op;
260 register int sz; /* size of desired block */
261 int amt; /* amount to allocate */
262 int nblks; /* how many blocks we get */
265 * sbrk_size <= 0 only for big, FLUFFY, requests (about
266 * 2^30 bytes on a VAX, I think) or for a negative arg.
268 sz = 1 << (bucket + 3);
282 if (amt > pagepool_end - pagepool_start)
283 if (morepages(amt/pagesz + NPOOLPAGES) == 0)
285 op = (union overhead *)pagepool_start;
286 pagepool_start += amt;
289 * Add new memory allocated to that on
290 * free list for this hash bucket.
293 while (--nblks > 0) {
294 op->ov_next = (union overhead *)((caddr_t)op + sz);
295 op = (union overhead *)((caddr_t)op + sz);
304 register union overhead *op;
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 thru 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 int realloc_srchlen = 4; /* 4 should be plenty, -1 =>'s whole list */
353 return (malloc(nbytes));
354 op = (union overhead *)((caddr_t)cp - sizeof (union overhead));
355 if (op->ov_magic == MAGIC) {
360 * Already free, doing "compaction".
362 * Search for the old block of memory on the
363 * free list. First, check the most common
364 * case (last element free'd), then (this failing)
365 * the last ``realloc_srchlen'' items free'd.
366 * If all lookups fail, then assume the size of
367 * the memory block being realloc'd is the
368 * largest possible (so that all "nbytes" of new
369 * memory are copied into). Note that this could cause
370 * a memory fault if the old area was tiny, and the moon
371 * is gibbous. However, that is very unlikely.
373 if ((i = findbucket(op, 1)) < 0 &&
374 (i = findbucket(op, realloc_srchlen)) < 0)
378 if (onb < (u_int)pagesz)
379 onb -= sizeof (*op) + RSLOP;
381 onb += pagesz - sizeof (*op) - RSLOP;
382 /* avoid the copy if same size block */
387 i -= sizeof (*op) + RSLOP;
389 i += pagesz - sizeof (*op) - RSLOP;
391 if (nbytes <= onb && nbytes > (size_t)i) {
393 op->ov_size = (nbytes + RSLOP - 1) & ~(RSLOP - 1);
394 *(u_short *)((caddr_t)(op + 1) + op->ov_size) = RMAGIC;
400 if ((res = malloc(nbytes)) == NULL)
402 if (cp != res) /* common optimization if "compacting" */
403 bcopy(cp, res, (nbytes < onb) ? nbytes : onb);
408 * Search ``srchlen'' elements of each free list for a block whose
409 * header starts at ``freep''. If srchlen is -1 search the whole list.
410 * Return bucket number, or -1 if not found.
413 findbucket(freep, srchlen)
414 union overhead *freep;
417 register union overhead *p;
420 for (i = 0; i < NBUCKETS; i++) {
422 for (p = nextf[i]; p && j != srchlen; p = p->ov_next) {
433 * mstats - print out statistics about malloc
435 * Prints two lines of numbers, one showing the length of the free list
436 * for each size category, the second showing the number of mallocs -
437 * frees for each size category.
443 register union overhead *p;
447 fprintf(stderr, "Memory allocation statistics %s\nfree:\t", s);
448 for (i = 0; i < NBUCKETS; i++) {
449 for (j = 0, p = nextf[i]; p; p = p->ov_next, j++)
451 fprintf(stderr, " %d", j);
452 totfree += j * (1 << (i + 3));
454 fprintf(stderr, "\nused:\t");
455 for (i = 0; i < NBUCKETS; i++) {
456 fprintf(stderr, " %d", nmalloc[i]);
457 totused += nmalloc[i] * (1 << (i + 3));
459 fprintf(stderr, "\n\tTotal in use: %d, total free: %d\n",
473 fd = open(_PATH_DEVZERO, O_RDWR, 0);
475 perror(_PATH_DEVZERO);
478 if (pagepool_end - pagepool_start > pagesz) {
479 caddr_t addr = (caddr_t)
480 (((long)pagepool_start + pagesz - 1) & ~(pagesz - 1));
481 if (munmap(addr, pagepool_end - addr) != 0)
482 warn("morepages: munmap %p", addr);
485 offset = (long)pagepool_start - ((long)pagepool_start & ~(pagesz - 1));
487 if ((pagepool_start = mmap(0, n * pagesz,
488 PROT_READ|PROT_WRITE,
489 MAP_ANON|MAP_COPY, fd, 0)) == (caddr_t)-1) {
490 xprintf("Cannot map anonymous memory");
493 pagepool_end = pagepool_start + n * pagesz;
494 pagepool_start += offset;
503 * Non-mallocing printf, for use by malloc itself.
506 xprintf(const char *fmt, ...)
512 vsprintf(buf, fmt, ap);
513 (void)write(STDOUT_FILENO, buf, strlen(buf));