1 /* 2 * Copyright (c) 2009-2019 The DragonFly Project. All rights reserved. 3 * 4 * This code is derived from software contributed to The DragonFly Project 5 * by Alex Hornung <ahornung@gmail.com> 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in 15 * the documentation and/or other materials provided with the 16 * distribution. 17 * 3. Neither the name of The DragonFly Project nor the names of its 18 * contributors may be used to endorse or promote products derived 19 * from this software without specific, prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 22 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 23 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 24 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 25 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 26 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING, 27 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 28 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 29 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 30 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 31 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 */ 34 #include <sys/param.h> 35 #include <sys/systm.h> 36 #include <sys/kernel.h> 37 #include <sys/malloc.h> 38 #include <machine/limits.h> 39 #include <sys/devfs.h> 40 41 MALLOC_DECLARE(M_DEVFS); 42 43 /* 44 * Locallized lock to ensure the integrity of the bitmap/cloning 45 * code. Callers using chk/set sequences must still check for races 46 * or have their own locks. 47 * 48 * We use a recursive lock only to allow *_get() to call *_set(). 49 */ 50 static struct lock devfs_bitmap_lock = 51 LOCK_INITIALIZER("dbmap", 0, LK_CANRECURSE); 52 53 /* 54 * DEVFS clone bitmap functions 55 */ 56 void 57 devfs_clone_bitmap_init(struct devfs_bitmap *bitmap) 58 { 59 bitmap->chunks = DEVFS_BITMAP_INITIAL_SIZE; 60 bitmap->bitmap = kmalloc(bitmap->chunks * sizeof(u_long), 61 M_DEVFS, M_WAITOK); 62 memset(bitmap->bitmap, -1, bitmap->chunks * sizeof(u_long)); 63 } 64 65 66 void 67 devfs_clone_bitmap_uninit(struct devfs_bitmap *bitmap) 68 { 69 kfree(bitmap->bitmap, M_DEVFS); 70 } 71 72 /* 73 * Extend the bitmap past (not just up to) 'newchunks' chunks. While 74 * probably not necessary, we go a little further and give ourselves 75 * one extra chunk's worth of bitmap beyond what is required. 76 */ 77 static void 78 devfs_clone_bitmap_extend(struct devfs_bitmap *bitmap, int newchunks) 79 { 80 int oldchunks = bitmap->chunks; 81 82 bitmap->chunks = newchunks + 2; 83 bitmap->bitmap = krealloc(bitmap->bitmap, 84 sizeof(u_long) * bitmap->chunks, 85 M_DEVFS, M_WAITOK); 86 memset(bitmap->bitmap + oldchunks, -1, 87 sizeof(u_long) * (bitmap->chunks - oldchunks)); 88 } 89 90 /* 91 * This helper function determines the next available free unit in the 92 * bitmap, extending the bitmap if necessary. It cannot fail. 93 */ 94 static int 95 devfs_clone_bitmap_fff(struct devfs_bitmap *bitmap) 96 { 97 u_long curbitmap; 98 int bit, i; 99 int chunks; 100 101 chunks = bitmap->chunks; 102 103 for (i = 0; i < chunks + 1; i++) { 104 if (i == chunks) 105 devfs_clone_bitmap_extend(bitmap, i); 106 curbitmap = bitmap->bitmap[i]; 107 108 if (curbitmap) { 109 curbitmap &= (~curbitmap)+1; 110 for (bit = 1; curbitmap != 1; bit++) 111 curbitmap >>= 1; 112 113 return (bit - 1 + (i << 3) * sizeof(curbitmap)); 114 } 115 } 116 117 /* 118 * NOT REACHED 119 */ 120 panic("devfs_clone_bitmap_fff"); 121 return -1; 122 } 123 124 /* 125 * Caller wants to know if the specified unit has been allocated 126 * or not. Return 0, indicating that it has not been allocated. 127 * 128 * Caller must hold a lock to prevent chk-to-set races. Devfs also 129 * obtains a temporary lock, juse in case, to ensure structural 130 * integrity. 131 * 132 * (the bitmap implements 0=allocated, 1=not-allocated but the 133 * return value is inverted). 134 */ 135 int 136 devfs_clone_bitmap_chk(struct devfs_bitmap *bitmap, int unit) 137 { 138 int chunk; 139 int res; 140 141 chunk = unit / (sizeof(u_long) * 8); 142 unit -= chunk * (sizeof(u_long) * 8); 143 144 lockmgr(&devfs_bitmap_lock, LK_EXCLUSIVE); 145 if (chunk >= bitmap->chunks) { 146 lockmgr(&devfs_bitmap_lock, LK_RELEASE); 147 return 0; /* device does not exist */ 148 } 149 res = !((bitmap->bitmap[chunk]) & (1UL << unit)); 150 lockmgr(&devfs_bitmap_lock, LK_RELEASE); 151 152 return res; 153 } 154 155 /* 156 * Unconditionally mark the specified unit as allocated in the bitmap. 157 * 158 * Caller must hold a lock to prevent chk-to-set races, or otherwise 159 * check for a return value < 0 from this routine. If the unit had 160 * never been allocated in the past, a token lock might not be sufficient 161 * to avoid races (if this function must extend the bitmap it could block 162 * temporary in kmalloc()). 163 * 164 * devfs acquires a temporary lock to ensure structural integrity. 165 * 166 * If the bit is already clear (indicating that the unit is already 167 * allocated), return -1. Otherwise return 0. 168 */ 169 int 170 devfs_clone_bitmap_set(struct devfs_bitmap *bitmap, int unit) 171 { 172 int chunk; 173 int res; 174 175 chunk = unit / (sizeof(u_long) * 8); 176 unit -= chunk * (sizeof(u_long) * 8); 177 178 lockmgr(&devfs_bitmap_lock, LK_EXCLUSIVE); 179 if (chunk >= bitmap->chunks) 180 devfs_clone_bitmap_extend(bitmap, chunk); 181 if (bitmap->bitmap[chunk] & (1UL << unit)) { 182 bitmap->bitmap[chunk] &= ~(1UL << unit); 183 res = 0; 184 } else { 185 res = -1; 186 } 187 lockmgr(&devfs_bitmap_lock, LK_RELEASE); 188 189 return res; 190 } 191 192 /* 193 * Unconditionally deallocate a unit number. Caller must synchronize any 194 * destroy_dev()'s the device called before clearing the bitmap bit to 195 * avoid races against a new clone. 196 */ 197 void 198 devfs_clone_bitmap_put(struct devfs_bitmap *bitmap, int unit) 199 { 200 int chunk; 201 202 devfs_config(); 203 204 chunk = unit / (sizeof(u_long) * 8); 205 unit -= chunk * (sizeof(u_long) * 8); 206 207 lockmgr(&devfs_bitmap_lock, LK_EXCLUSIVE); 208 if (chunk < bitmap->chunks) 209 bitmap->bitmap[chunk] |= (1UL << unit); 210 lockmgr(&devfs_bitmap_lock, LK_RELEASE); 211 } 212 213 /* 214 * Conditionally allocate a unit from the bitmap. Returns -1 if no 215 * more units are available. 216 * 217 * Caller must hold a lock to avoid bitmap races. Since *_fff() below 218 * pre-extends the bitmap as necessary, a token lock is sufficient. 219 */ 220 int 221 devfs_clone_bitmap_get(struct devfs_bitmap *bitmap, int limit) 222 { 223 int unit; 224 225 lockmgr(&devfs_bitmap_lock, LK_EXCLUSIVE); 226 unit = devfs_clone_bitmap_fff(bitmap); 227 if (limit > 0 && unit > limit) { 228 unit = -1; 229 } else { 230 devfs_clone_bitmap_set(bitmap, unit); 231 } 232 lockmgr(&devfs_bitmap_lock, LK_RELEASE); 233 234 return unit; 235 } 236