summaryrefslogtreecommitdiffstats
path: root/lib/libstand/zalloc.c
blob: e83fccb8ced360b87f88ebda0eb3af16bc86a152 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
/*
 * This module derived from code donated to the FreeBSD Project by 
 * Matthew Dillon <dillon@backplane.com>
 *
 * Copyright (c) 1998 The FreeBSD Project
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");

/*
 * LIB/MEMORY/ZALLOC.C	- self contained low-overhead memory pool/allocation 
 *			  subsystem
 *
 *	This subsystem implements memory pools and memory allocation 
 *	routines.
 *
 *	Pools are managed via a linked list of 'free' areas.  Allocating
 *	memory creates holes in the freelist, freeing memory fills them.
 *	Since the freelist consists only of free memory areas, it is possible
 *	to allocate the entire pool without incuring any structural overhead.
 *
 *	The system works best when allocating similarly-sized chunks of
 *	memory.  Care must be taken to avoid fragmentation when 
 *	allocating/deallocating dissimilar chunks.
 *
 *	When a memory pool is first allocated, the entire pool is marked as
 *	allocated.  This is done mainly because we do not want to modify any
 *	portion of a pool's data area until we are given permission.  The
 *	caller must explicitly deallocate portions of the pool to make them
 *	available.
 *
 *	z[n]xalloc() works like z[n]alloc() but the allocation is made from
 *	within the specified address range.  If the segment could not be 
 *	allocated, NULL is returned.  WARNING!  The address range will be
 *	aligned to an 8 or 16 byte boundry depending on the cpu so if you
 *	give an unaligned address range, unexpected results may occur.
 *
 *	If a standard allocation fails, the reclaim function will be called
 *	to recover some space.  This usually causes other portions of the
 *	same pool to be released.  Memory allocations at this low level
 *	should not block but you can do that too in your reclaim function
 *	if you want.  Reclaim does not function when z[n]xalloc() is used,
 *	only for z[n]alloc().
 *
 *	Allocation and frees of 0 bytes are valid operations.
 */

#include "zalloc_defs.h"

/*
 * znalloc() -	allocate memory (without zeroing) from pool.  Call reclaim
 *		and retry if appropriate, return NULL if unable to allocate
 *		memory.
 */

void *
znalloc(MemPool *mp, iaddr_t bytes)
{
    /*
     * align according to pool object size (can be 0).  This is
     * inclusive of the MEMNODE_SIZE_MASK minimum alignment.
     *
     */
    bytes = (bytes + MEMNODE_SIZE_MASK) & ~MEMNODE_SIZE_MASK;

    if (bytes == 0)
	return((void *)-1);

    /*
     * locate freelist entry big enough to hold the object.  If all objects
     * are the same size, this is a constant-time function.
     */

    if (bytes <= mp->mp_Size - mp->mp_Used) {
	MemNode **pmn;
	MemNode *mn;

	for (pmn = &mp->mp_First; (mn=*pmn) != NULL; pmn = &mn->mr_Next) {
	    if (bytes > mn->mr_Bytes)
		continue;

	    /*
	     *  Cut a chunk of memory out of the beginning of this
	     *  block and fixup the link appropriately.
	     */

	    {
		char *ptr = (char *)mn;

		if (mn->mr_Bytes == bytes) {
		    *pmn = mn->mr_Next;
		} else {
		    mn = (MemNode *)((char *)mn + bytes);
		    mn->mr_Next  = ((MemNode *)ptr)->mr_Next;
		    mn->mr_Bytes = ((MemNode *)ptr)->mr_Bytes - bytes;
		    *pmn = mn;
		}
		mp->mp_Used += bytes;
		return(ptr);
	    }
	}
    }

    /*
     * Memory pool is full, return NULL.
     */

    return(NULL);
}

/*
 * zfree() - free previously allocated memory
 */

void
zfree(MemPool *mp, void *ptr, iaddr_t bytes)
{
    /*
     * align according to pool object size (can be 0).  This is
     * inclusive of the MEMNODE_SIZE_MASK minimum alignment.
     */
    bytes = (bytes + MEMNODE_SIZE_MASK) & ~MEMNODE_SIZE_MASK;

    if (bytes == 0)
	return;

    /*
     * panic if illegal pointer
     */

    if ((char *)ptr < (char *)mp->mp_Base || 
	(char *)ptr + bytes > (char *)mp->mp_End ||
	((iaddr_t)ptr & MEMNODE_SIZE_MASK) != 0)
	panic("zfree(%p,%d): wild pointer", ptr, bytes);

    /*
     * free the segment
     */

    {
	MemNode **pmn;
	MemNode *mn;

	mp->mp_Used -= bytes;

	for (pmn = &mp->mp_First; (mn = *pmn) != NULL; pmn = &mn->mr_Next) {
	    /*
	     * If area between last node and current node
	     *  - check range
	     *  - check merge with next area
	     *  - check merge with previous area
	     */
	    if ((char *)ptr <= (char *)mn) {
		/*
		 * range check
		 */
		if ((char *)ptr + bytes > (char *)mn)
		    panic("zfree(%p,%d): corrupt memlist1",ptr, bytes);

		/*
		 * merge against next area or create independant area
		 */

		if ((char *)ptr + bytes == (char *)mn) {
		    ((MemNode *)ptr)->mr_Next = mn->mr_Next;
		    ((MemNode *)ptr)->mr_Bytes= bytes + mn->mr_Bytes;
		} else {
		    ((MemNode *)ptr)->mr_Next = mn;
		    ((MemNode *)ptr)->mr_Bytes= bytes;
		}
		*pmn = mn = (MemNode *)ptr;

		/*
		 * merge against previous area (if there is a previous
		 * area).
		 */

		if (pmn != &mp->mp_First) {
		    if ((char*)pmn + ((MemNode*)pmn)->mr_Bytes == (char*)ptr) {
			((MemNode *)pmn)->mr_Next = mn->mr_Next;
			((MemNode *)pmn)->mr_Bytes += mn->mr_Bytes;
			mn = (MemNode *)pmn;
		    }
		}
		return;
		/* NOT REACHED */
	    }
	    if ((char *)ptr < (char *)mn + mn->mr_Bytes)
		panic("zfree(%p,%d): corrupt memlist2", ptr, bytes);
	}
	/*
	 * We are beyond the last MemNode, append new MemNode.  Merge against
	 * previous area if possible.
	 */
	if (pmn == &mp->mp_First || 
	    (char *)pmn + ((MemNode *)pmn)->mr_Bytes != (char *)ptr
	) {
	    ((MemNode *)ptr)->mr_Next = NULL;
	    ((MemNode *)ptr)->mr_Bytes = bytes;
	    *pmn = (MemNode *)ptr;
	    mn = (MemNode *)ptr;
	} else {
	    ((MemNode *)pmn)->mr_Bytes += bytes;
	    mn = (MemNode *)pmn;
	}
    }
}

/*
 * zextendPool() - extend memory pool to cover additional space.
 *
 *		   Note: the added memory starts out as allocated, you
 *		   must free it to make it available to the memory subsystem.
 *
 *		   Note: mp_Size may not reflect (mp_End - mp_Base) range
 *		   due to other parts of the system doing their own sbrk()
 *		   calls.
 */

void
zextendPool(MemPool *mp, void *base, iaddr_t bytes)
{
    if (mp->mp_Size == 0) {
	mp->mp_Base = base;
	mp->mp_Used = bytes;
	mp->mp_End = (char *)base + bytes;
    } else {
	void *pend = (char *)mp->mp_Base + mp->mp_Size;

	if (base < mp->mp_Base) {
	    /* mp->mp_Size += (char *)mp->mp_Base - (char *)base; */
	    mp->mp_Used += (char *)mp->mp_Base - (char *)base;
	    mp->mp_Base = base;
	}
	base = (char *)base + bytes;
	if (base > pend) {
	    /* mp->mp_Size += (char *)base - (char *)pend; */
	    mp->mp_Used += (char *)base - (char *)pend;
	    mp->mp_End = (char *)base;
	}
    }
    mp->mp_Size += bytes;
}

#ifdef ZALLOCDEBUG

void
zallocstats(MemPool *mp)
{
    int abytes = 0;
    int hbytes = 0;
    int fcount = 0;
    MemNode *mn;

    printf("%d bytes reserved", (int) mp->mp_Size);

    mn = mp->mp_First;

    if ((void *)mn != (void *)mp->mp_Base) {
	abytes += (char *)mn - (char *)mp->mp_Base;
    }

    while (mn) {
	if ((char *)mn + mn->mr_Bytes != mp->mp_End) {
	    hbytes += mn->mr_Bytes;
	    ++fcount;
	}
	if (mn->mr_Next)
	    abytes += (char *)mn->mr_Next - ((char *)mn + mn->mr_Bytes);
	mn = mn->mr_Next;
    }
    printf(" %d bytes allocated\n%d fragments (%d bytes fragmented)\n",
	abytes,
	fcount,
	hbytes
    );
}

#endif

OpenPOWER on IntegriCloud