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1 | /* $Header: malloc.c,v 3.0.1.2 89/11/11 04:36:37 lwall Locked $ |
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2 | * |
3 | * $Log: malloc.c,v $ |
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4 | * Revision 3.0.1.2 89/11/11 04:36:37 lwall |
5 | * patch2: malloc pointer corruption check made more portable |
6 | * |
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7 | * Revision 3.0.1.1 89/10/26 23:15:05 lwall |
8 | * patch1: some declarations were missing from malloc.c |
9 | * patch1: sparc machines had alignment problems in malloc.c |
10 | * |
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11 | * Revision 3.0 89/10/18 15:20:39 lwall |
12 | * 3.0 baseline |
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13 | * |
14 | */ |
15 | |
16 | #ifndef lint |
17 | static char sccsid[] = "@(#)malloc.c 4.3 (Berkeley) 9/16/83"; |
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18 | |
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19 | #ifdef DEBUGGING |
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20 | #define RCHECK |
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21 | #endif |
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22 | /* |
23 | * malloc.c (Caltech) 2/21/82 |
24 | * Chris Kingsley, kingsley@cit-20. |
25 | * |
26 | * This is a very fast storage allocator. It allocates blocks of a small |
27 | * number of different sizes, and keeps free lists of each size. Blocks that |
28 | * don't exactly fit are passed up to the next larger size. In this |
29 | * implementation, the available sizes are 2^n-4 (or 2^n-12) bytes long. |
30 | * This is designed for use in a program that uses vast quantities of memory, |
31 | * but bombs when it runs out. |
32 | */ |
33 | |
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34 | #include "EXTERN.h" |
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35 | #include "perl.h" |
36 | |
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37 | static findbucket(), morecore(); |
38 | |
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39 | /* I don't much care whether these are defined in sys/types.h--LAW */ |
40 | |
41 | #define u_char unsigned char |
42 | #define u_int unsigned int |
43 | #define u_short unsigned short |
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44 | |
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45 | /* |
46 | * The overhead on a block is at least 4 bytes. When free, this space |
47 | * contains a pointer to the next free block, and the bottom two bits must |
48 | * be zero. When in use, the first byte is set to MAGIC, and the second |
49 | * byte is the size index. The remaining bytes are for alignment. |
50 | * If range checking is enabled and the size of the block fits |
51 | * in two bytes, then the top two bytes hold the size of the requested block |
52 | * plus the range checking words, and the header word MINUS ONE. |
53 | */ |
54 | union overhead { |
55 | union overhead *ov_next; /* when free */ |
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56 | #if defined (mips) || defined (sparc) |
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57 | double strut; /* alignment problems */ |
58 | #endif |
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59 | struct { |
60 | u_char ovu_magic; /* magic number */ |
61 | u_char ovu_index; /* bucket # */ |
62 | #ifdef RCHECK |
63 | u_short ovu_size; /* actual block size */ |
64 | u_int ovu_rmagic; /* range magic number */ |
65 | #endif |
66 | } ovu; |
67 | #define ov_magic ovu.ovu_magic |
68 | #define ov_index ovu.ovu_index |
69 | #define ov_size ovu.ovu_size |
70 | #define ov_rmagic ovu.ovu_rmagic |
71 | }; |
72 | |
73 | #define MAGIC 0xff /* magic # on accounting info */ |
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74 | #define OLDMAGIC 0x7f /* same after a free() */ |
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75 | #define RMAGIC 0x55555555 /* magic # on range info */ |
76 | #ifdef RCHECK |
77 | #define RSLOP sizeof (u_int) |
78 | #else |
79 | #define RSLOP 0 |
80 | #endif |
81 | |
82 | /* |
83 | * nextf[i] is the pointer to the next free block of size 2^(i+3). The |
84 | * smallest allocatable block is 8 bytes. The overhead information |
85 | * precedes the data area returned to the user. |
86 | */ |
87 | #define NBUCKETS 30 |
88 | static union overhead *nextf[NBUCKETS]; |
89 | extern char *sbrk(); |
90 | |
91 | #ifdef MSTATS |
92 | /* |
93 | * nmalloc[i] is the difference between the number of mallocs and frees |
94 | * for a given block size. |
95 | */ |
96 | static u_int nmalloc[NBUCKETS]; |
97 | #include <stdio.h> |
98 | #endif |
99 | |
100 | #ifdef debug |
101 | #define ASSERT(p) if (!(p)) botch("p"); else |
102 | static |
103 | botch(s) |
104 | char *s; |
105 | { |
106 | |
107 | printf("assertion botched: %s\n", s); |
108 | abort(); |
109 | } |
110 | #else |
111 | #define ASSERT(p) |
112 | #endif |
113 | |
114 | char * |
115 | malloc(nbytes) |
116 | register unsigned nbytes; |
117 | { |
118 | register union overhead *p; |
119 | register int bucket = 0; |
120 | register unsigned shiftr; |
121 | |
122 | /* |
123 | * Convert amount of memory requested into |
124 | * closest block size stored in hash buckets |
125 | * which satisfies request. Account for |
126 | * space used per block for accounting. |
127 | */ |
128 | nbytes += sizeof (union overhead) + RSLOP; |
129 | nbytes = (nbytes + 3) &~ 3; |
130 | shiftr = (nbytes - 1) >> 2; |
131 | /* apart from this loop, this is O(1) */ |
132 | while (shiftr >>= 1) |
133 | bucket++; |
134 | /* |
135 | * If nothing in hash bucket right now, |
136 | * request more memory from the system. |
137 | */ |
138 | if (nextf[bucket] == NULL) |
139 | morecore(bucket); |
140 | if ((p = (union overhead *)nextf[bucket]) == NULL) |
141 | return (NULL); |
142 | /* remove from linked list */ |
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143 | #ifdef RCHECK |
144 | if (*((int*)p) & (sizeof(union overhead) - 1)) |
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145 | #ifndef I286 |
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146 | fprintf(stderr,"Corrupt malloc ptr 0x%x at 0x%x\n",*((int*)p),p); |
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147 | #else |
148 | fprintf(stderr,"Corrupt malloc ptr 0x%lx at 0x%lx\n",*((int*)p),p); |
149 | #endif |
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150 | #endif |
151 | nextf[bucket] = p->ov_next; |
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152 | p->ov_magic = MAGIC; |
153 | p->ov_index= bucket; |
154 | #ifdef MSTATS |
155 | nmalloc[bucket]++; |
156 | #endif |
157 | #ifdef RCHECK |
158 | /* |
159 | * Record allocated size of block and |
160 | * bound space with magic numbers. |
161 | */ |
162 | if (nbytes <= 0x10000) |
163 | p->ov_size = nbytes - 1; |
164 | p->ov_rmagic = RMAGIC; |
165 | *((u_int *)((caddr_t)p + nbytes - RSLOP)) = RMAGIC; |
166 | #endif |
167 | return ((char *)(p + 1)); |
168 | } |
169 | |
170 | /* |
171 | * Allocate more memory to the indicated bucket. |
172 | */ |
173 | static |
174 | morecore(bucket) |
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175 | register int bucket; |
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176 | { |
177 | register union overhead *op; |
178 | register int rnu; /* 2^rnu bytes will be requested */ |
179 | register int nblks; /* become nblks blocks of the desired size */ |
180 | register int siz; |
181 | |
182 | if (nextf[bucket]) |
183 | return; |
184 | /* |
185 | * Insure memory is allocated |
186 | * on a page boundary. Should |
187 | * make getpageize call? |
188 | */ |
189 | op = (union overhead *)sbrk(0); |
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190 | #ifndef I286 |
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191 | if ((int)op & 0x3ff) |
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192 | (void)sbrk(1024 - ((int)op & 0x3ff)); |
193 | #else |
194 | /* The sbrk(0) call on the I286 always returns the next segment */ |
195 | #endif |
196 | |
197 | #ifndef I286 |
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198 | /* take 2k unless the block is bigger than that */ |
199 | rnu = (bucket <= 8) ? 11 : bucket + 3; |
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200 | #else |
201 | /* take 16k unless the block is bigger than that |
202 | (80286s like large segments!) */ |
203 | rnu = (bucket <= 11) ? 14 : bucket + 3; |
204 | #endif |
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205 | nblks = 1 << (rnu - (bucket + 3)); /* how many blocks to get */ |
206 | if (rnu < bucket) |
207 | rnu = bucket; |
208 | op = (union overhead *)sbrk(1 << rnu); |
209 | /* no more room! */ |
210 | if ((int)op == -1) |
211 | return; |
212 | /* |
213 | * Round up to minimum allocation size boundary |
214 | * and deduct from block count to reflect. |
215 | */ |
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216 | #ifndef I286 |
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217 | if ((int)op & 7) { |
218 | op = (union overhead *)(((int)op + 8) &~ 7); |
219 | nblks--; |
220 | } |
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221 | #else |
222 | /* Again, this should always be ok on an 80286 */ |
223 | #endif |
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224 | /* |
225 | * Add new memory allocated to that on |
226 | * free list for this hash bucket. |
227 | */ |
228 | nextf[bucket] = op; |
229 | siz = 1 << (bucket + 3); |
230 | while (--nblks > 0) { |
231 | op->ov_next = (union overhead *)((caddr_t)op + siz); |
232 | op = (union overhead *)((caddr_t)op + siz); |
233 | } |
234 | } |
235 | |
236 | free(cp) |
237 | char *cp; |
238 | { |
239 | register int size; |
240 | register union overhead *op; |
241 | |
242 | if (cp == NULL) |
243 | return; |
244 | op = (union overhead *)((caddr_t)cp - sizeof (union overhead)); |
245 | #ifdef debug |
246 | ASSERT(op->ov_magic == MAGIC); /* make sure it was in use */ |
247 | #else |
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248 | if (op->ov_magic != MAGIC) { |
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249 | warn("%s free() ignored", |
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250 | op->ov_magic == OLDMAGIC ? "Duplicate" : "Bad"); |
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251 | return; /* sanity */ |
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252 | } |
253 | op->ov_magic = OLDMAGIC; |
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254 | #endif |
255 | #ifdef RCHECK |
256 | ASSERT(op->ov_rmagic == RMAGIC); |
257 | if (op->ov_index <= 13) |
258 | ASSERT(*(u_int *)((caddr_t)op + op->ov_size + 1 - RSLOP) == RMAGIC); |
259 | #endif |
260 | ASSERT(op->ov_index < NBUCKETS); |
261 | size = op->ov_index; |
262 | op->ov_next = nextf[size]; |
263 | nextf[size] = op; |
264 | #ifdef MSTATS |
265 | nmalloc[size]--; |
266 | #endif |
267 | } |
268 | |
269 | /* |
270 | * When a program attempts "storage compaction" as mentioned in the |
271 | * old malloc man page, it realloc's an already freed block. Usually |
272 | * this is the last block it freed; occasionally it might be farther |
273 | * back. We have to search all the free lists for the block in order |
274 | * to determine its bucket: 1st we make one pass thru the lists |
275 | * checking only the first block in each; if that fails we search |
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276 | * ``reall_srchlen'' blocks in each list for a match (the variable |
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277 | * is extern so the caller can modify it). If that fails we just copy |
278 | * however many bytes was given to realloc() and hope it's not huge. |
279 | */ |
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280 | int reall_srchlen = 4; /* 4 should be plenty, -1 =>'s whole list */ |
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281 | |
282 | char * |
283 | realloc(cp, nbytes) |
284 | char *cp; |
285 | unsigned nbytes; |
286 | { |
287 | register u_int onb; |
288 | union overhead *op; |
289 | char *res; |
290 | register int i; |
291 | int was_alloced = 0; |
292 | |
293 | if (cp == NULL) |
294 | return (malloc(nbytes)); |
295 | op = (union overhead *)((caddr_t)cp - sizeof (union overhead)); |
296 | if (op->ov_magic == MAGIC) { |
297 | was_alloced++; |
298 | i = op->ov_index; |
299 | } else { |
300 | /* |
301 | * Already free, doing "compaction". |
302 | * |
303 | * Search for the old block of memory on the |
304 | * free list. First, check the most common |
305 | * case (last element free'd), then (this failing) |
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306 | * the last ``reall_srchlen'' items free'd. |
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307 | * If all lookups fail, then assume the size of |
308 | * the memory block being realloc'd is the |
309 | * smallest possible. |
310 | */ |
311 | if ((i = findbucket(op, 1)) < 0 && |
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312 | (i = findbucket(op, reall_srchlen)) < 0) |
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313 | i = 0; |
314 | } |
315 | onb = (1 << (i + 3)) - sizeof (*op) - RSLOP; |
316 | /* avoid the copy if same size block */ |
317 | if (was_alloced && |
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318 | nbytes <= onb && nbytes > (onb >> 1) - sizeof(*op) - RSLOP) { |
319 | #ifdef RCHECK |
320 | /* |
321 | * Record new allocated size of block and |
322 | * bound space with magic numbers. |
323 | */ |
324 | if (op->ov_index <= 13) { |
325 | /* |
326 | * Convert amount of memory requested into |
327 | * closest block size stored in hash buckets |
328 | * which satisfies request. Account for |
329 | * space used per block for accounting. |
330 | */ |
331 | nbytes += sizeof (union overhead) + RSLOP; |
332 | nbytes = (nbytes + 3) &~ 3; |
333 | op->ov_size = nbytes - 1; |
334 | *((u_int *)((caddr_t)op + nbytes - RSLOP)) = RMAGIC; |
335 | } |
336 | #endif |
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337 | return(cp); |
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338 | } |
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339 | if ((res = malloc(nbytes)) == NULL) |
340 | return (NULL); |
341 | if (cp != res) /* common optimization */ |
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342 | (void)bcopy(cp, res, (int)((nbytes < onb) ? nbytes : onb)); |
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343 | if (was_alloced) |
344 | free(cp); |
345 | return (res); |
346 | } |
347 | |
348 | /* |
349 | * Search ``srchlen'' elements of each free list for a block whose |
350 | * header starts at ``freep''. If srchlen is -1 search the whole list. |
351 | * Return bucket number, or -1 if not found. |
352 | */ |
353 | static |
354 | findbucket(freep, srchlen) |
355 | union overhead *freep; |
356 | int srchlen; |
357 | { |
358 | register union overhead *p; |
359 | register int i, j; |
360 | |
361 | for (i = 0; i < NBUCKETS; i++) { |
362 | j = 0; |
363 | for (p = nextf[i]; p && j != srchlen; p = p->ov_next) { |
364 | if (p == freep) |
365 | return (i); |
366 | j++; |
367 | } |
368 | } |
369 | return (-1); |
370 | } |
371 | |
372 | #ifdef MSTATS |
373 | /* |
374 | * mstats - print out statistics about malloc |
375 | * |
376 | * Prints two lines of numbers, one showing the length of the free list |
377 | * for each size category, the second showing the number of mallocs - |
378 | * frees for each size category. |
379 | */ |
380 | mstats(s) |
381 | char *s; |
382 | { |
383 | register int i, j; |
384 | register union overhead *p; |
385 | int totfree = 0, |
386 | totused = 0; |
387 | |
388 | fprintf(stderr, "Memory allocation statistics %s\nfree:\t", s); |
389 | for (i = 0; i < NBUCKETS; i++) { |
390 | for (j = 0, p = nextf[i]; p; p = p->ov_next, j++) |
391 | ; |
392 | fprintf(stderr, " %d", j); |
393 | totfree += j * (1 << (i + 3)); |
394 | } |
395 | fprintf(stderr, "\nused:\t"); |
396 | for (i = 0; i < NBUCKETS; i++) { |
397 | fprintf(stderr, " %d", nmalloc[i]); |
398 | totused += nmalloc[i] * (1 << (i + 3)); |
399 | } |
400 | fprintf(stderr, "\n\tTotal in use: %d, total free: %d\n", |
401 | totused, totfree); |
402 | } |
403 | #endif |
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404 | #endif /* lint */ |