1 /*
2 * Copyright (C) 2008 The Android Open Source Project
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * * Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * * Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in
12 * the documentation and/or other materials provided with the
13 * distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
16 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
17 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
18 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
19 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
21 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
22 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
23 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
24 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
25 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28
29 #include "linker.h"
30 #include "linker_debug.h"
31 #include "ba.h"
32
33 struct ba_bits {
34 unsigned allocated:1; /* 1 if allocated, 0 if free */
35 unsigned order:7; /* size of the region in ba space */
36 };
37
38 struct ba_info {
39 /* start address of the ba space */
40 unsigned long base;
41 /* total size of the ba space */
42 unsigned long size;
43 /* number of entries in the ba space */
44 int num_entries;
45 /* the bitmap for the region indicating which entries are allocated
46 * and which are free */
47 struct ba_bits *bitmap;
48 };
49
50 #undef min
51 #define min(a,b) ((a)<(b)?(a):(b))
52
53 #define BA_MIN_ALLOC LIBINC
54 #define BA_MAX_ORDER 128
55 #define BA_START LIBBASE
56 #define BA_SIZE (LIBLAST - LIBBASE)
57
58 #define BA_IS_FREE(index) (!(ba.bitmap[index].allocated))
59 #define BA_ORDER(index) ba.bitmap[index].order
60 #define BA_BUDDY_INDEX(index) ((index) ^ (1 << BA_ORDER(index)))
61 #define BA_NEXT_INDEX(index) ((index) + (1 << BA_ORDER(index)))
62 #define BA_OFFSET(index) ((index) * BA_MIN_ALLOC)
63 #define BA_START_ADDR(index) (BA_OFFSET(index) + ba.base)
64 #define BA_LEN(index) ((1 << BA_ORDER(index)) * BA_MIN_ALLOC)
65
66 static struct ba_bits ba_bitmap[BA_SIZE / BA_MIN_ALLOC];
67
68 static struct ba_info ba = {
69 .base = BA_START,
70 .size = BA_SIZE,
71 .bitmap = ba_bitmap,
72 .num_entries = sizeof(ba_bitmap)/sizeof(ba_bitmap[0]),
73 };
74
ba_init(void)75 void ba_init(void)
76 {
77 int i, index = 0;
78 for (i = sizeof(ba.num_entries) * 8 - 1; i >= 0; i--) {
79 if (ba.num_entries & 1<<i) {
80 BA_ORDER(index) = i;
81 index = BA_NEXT_INDEX(index);
82 }
83 }
84 }
85
ba_free(int index)86 int ba_free(int index)
87 {
88 int buddy, curr = index;
89
90 /* clean up the bitmap, merging any buddies */
91 ba.bitmap[curr].allocated = 0;
92 /* find a slots buddy Buddy# = Slot# ^ (1 << order)
93 * if the buddy is also free merge them
94 * repeat until the buddy is not free or end of the bitmap is reached
95 */
96 do {
97 buddy = BA_BUDDY_INDEX(curr);
98 if (BA_IS_FREE(buddy) &&
99 BA_ORDER(buddy) == BA_ORDER(curr)) {
100 BA_ORDER(buddy)++;
101 BA_ORDER(curr)++;
102 curr = min(buddy, curr);
103 } else {
104 break;
105 }
106 } while (curr < ba.num_entries);
107
108 return 0;
109 }
110
ba_order(unsigned long len)111 static unsigned long ba_order(unsigned long len)
112 {
113 unsigned long i;
114
115 len = (len + BA_MIN_ALLOC - 1) / BA_MIN_ALLOC;
116 len--;
117 for (i = 0; i < sizeof(len)*8; i++)
118 if (len >> i == 0)
119 break;
120 return i;
121 }
122
ba_allocate(unsigned long len)123 int ba_allocate(unsigned long len)
124 {
125 int curr = 0;
126 int end = ba.num_entries;
127 int best_fit = -1;
128 unsigned long order = ba_order(len);
129
130 if (order > BA_MAX_ORDER)
131 return -1;
132
133 /* look through the bitmap:
134 * if you find a free slot of the correct order use it
135 * otherwise, use the best fit (smallest with size > order) slot
136 */
137 while (curr < end) {
138 if (BA_IS_FREE(curr)) {
139 if (BA_ORDER(curr) == (unsigned char)order) {
140 /* set the not free bit and clear others */
141 best_fit = curr;
142 break;
143 }
144 if (BA_ORDER(curr) > (unsigned char)order &&
145 (best_fit < 0 ||
146 BA_ORDER(curr) < BA_ORDER(best_fit)))
147 best_fit = curr;
148 }
149 curr = BA_NEXT_INDEX(curr);
150 }
151
152 /* if best_fit < 0, there are no suitable slots,
153 * return an error
154 */
155 if (best_fit < 0)
156 return -1;
157
158 /* now partition the best fit:
159 * split the slot into 2 buddies of order - 1
160 * repeat until the slot is of the correct order
161 */
162 while (BA_ORDER(best_fit) > (unsigned char)order) {
163 int buddy;
164 BA_ORDER(best_fit) -= 1;
165 buddy = BA_BUDDY_INDEX(best_fit);
166 BA_ORDER(buddy) = BA_ORDER(best_fit);
167 }
168 ba.bitmap[best_fit].allocated = 1;
169 return best_fit;
170 }
171
ba_start_addr(int index)172 unsigned long ba_start_addr(int index)
173 {
174 return BA_START_ADDR(index);
175 }
176
ba_len(int index)177 unsigned long ba_len(int index)
178 {
179 return BA_LEN(index);
180 }
181