src/util/vma.c

   1 /*
   2  * Copyright © 2018 Intel Corporation
   3  *
   4  * Permission is hereby granted, free of charge, to any person obtaining a
   5  * copy of this software and associated documentation files (the "Software"),
   6  * to deal in the Software without restriction, including without limitation
   7  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
   8  * and/or sell copies of the Software, and to permit persons to whom the
   9  * Software is furnished to do so, subject to the following conditions:
  10  *
  11  * The above copyright notice and this permission notice (including the next
  12  * paragraph) shall be included in all copies or substantial portions of the
  13  * Software.
  14  *
  15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  16  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  18  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  19  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  20  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  21  * IN THE SOFTWARE.
  22  */
  23
  24 #include <stdlib.h>
  25
  26 #include "util/u_math.h"
  27 #include "util/vma.h"
  28
  29 struct util_vma_hole {
  30    struct list_head link;
  31    uint64_t offset;
  32    uint64_t size;
  33 };
  34
  35 #define util_vma_foreach_hole(_hole, _heap) \
  36    list_for_each_entry(struct util_vma_hole, _hole, &(_heap)->holes, link)
  37
  38 #define util_vma_foreach_hole_safe(_hole, _heap) \
  39    list_for_each_entry_safe(struct util_vma_hole, _hole, &(_heap)->holes, link)
  40
  41 void
  42 util_vma_heap_init(struct util_vma_heap *heap,
  43                    uint64_t start, uint64_t size)
  44 {
  45    list_inithead(&heap->holes);
  46    util_vma_heap_free(heap, start, size);
  47 }
  48
  49 void
  50 util_vma_heap_finish(struct util_vma_heap *heap)
  51 {
  52    util_vma_foreach_hole_safe(hole, heap)
  53       free(hole);
  54 }
  55
  56 #ifndef NDEBUG
  57 static void
  58 util_vma_heap_validate(struct util_vma_heap *heap)
  59 {
  60    uint64_t prev_offset = 0;
  61    util_vma_foreach_hole(hole, heap) {
  62       assert(hole->offset > 0);
  63       assert(hole->size > 0);
  64
  65       if (&hole->link == heap->holes.next) {
  66          /* This must be the top-most hole.  Assert that, if it overflows, it
  67           * overflows to 0, i.e. 2^64.
  68           */
  69          assert(hole->size + hole->offset == 0 ||
  70                 hole->size + hole->offset > hole->offset);
  71       } else {
  72          /* This is not the top-most hole so it must not overflow and, in
  73           * fact, must be strictly lower than the top-most hole.  If
  74           * hole->size + hole->offset == prev_offset, then we failed to join
  75           * holes during a util_vma_heap_free.
  76           */
  77          assert(hole->size + hole->offset > hole->offset &&
  78                 hole->size + hole->offset < prev_offset);
  79       }
  80       prev_offset = hole->offset;
  81    }
  82 }
  83 #else
  84 #define util_vma_heap_validate(heap)
  85 #endif
  86
  87 static void
  88 util_vma_hole_alloc(struct util_vma_hole *hole,
  89                     uint64_t offset, uint64_t size)
  90 {
  91    assert(hole->offset <= offset);
  92    assert(hole->size >= offset - hole->offset + size);
  93
  94    if (offset == hole->offset && size == hole->size) {
  95       /* Just get rid of the hole. */
  96       list_del(&hole->link);
  97       free(hole);
  98       return;
  99    }
 100
 101    assert(offset - hole->offset <= hole->size - size);
 102    uint64_t waste = (hole->size - size) - (offset - hole->offset);
 103    if (waste == 0) {
 104       /* We allocated at the top.  Shrink the hole down. */
 105       hole->size -= size;
 106       return;
 107    }
 108
 109    if (offset == hole->offset) {
 110       /* We allocated at the bottom. Shrink the hole up. */
 111       hole->offset += size;
 112       hole->size -= size;
 113       return;
 114    }
 115
 116    /* We allocated in the middle.  We need to split the old hole into two
 117     * holes, one high and one low.
 118     */
 119    struct util_vma_hole *high_hole = calloc(1, sizeof(*hole));
 120    high_hole->offset = offset + size;
 121    high_hole->size = waste;
 122
 123    /* Adjust the hole to be the amount of space left at he bottom of the
 124     * original hole.
 125     */
 126    hole->size = offset - hole->offset;
 127
 128    /* Place the new hole before the old hole so that the list is in order
 129     * from high to low.
 130     */
 131    list_addtail(&high_hole->link, &hole->link);
 132 }
 133
 134 uint64_t
 135 util_vma_heap_alloc(struct util_vma_heap *heap,
 136                     uint64_t size, uint64_t alignment)
 137 {
 138    /* The caller is expected to reject zero-size allocations */
 139    assert(size > 0);
 140    assert(alignment > 0);
 141
 142    util_vma_heap_validate(heap);
 143
 144    util_vma_foreach_hole_safe(hole, heap) {
 145       if (size > hole->size)
 146          continue;
 147
 148       /* Compute the offset as the highest address where a chunk of the given
 149        * size can be without going over the top of the hole.
 150        *
 151        * This calculation is known to not overflow because we know that
 152        * hole->size + hole->offset can only overflow to 0 and size > 0.
 153        */
 154       uint64_t offset = (hole->size - size) + hole->offset;
 155
 156       /* Align the offset.  We align down and not up because we are allocating
 157        * from the top of the hole and not the bottom.
 158        */
 159       offset = (offset / alignment) * alignment;
 160
 161       if (offset < hole->offset)
 162          continue;
 163
 164       util_vma_hole_alloc(hole, offset, size);
 165       util_vma_heap_validate(heap);
 166       return offset;
 167    }
 168
 169    /* Failed to allocate */
 170    return 0;
 171 }
 172
 173 bool
 174 util_vma_heap_alloc_addr(struct util_vma_heap *heap,
 175                          uint64_t offset, uint64_t size)
 176 {
 177    /* An offset of 0 is reserved for allocation failure.  It is not a valid
 178     * address and cannot be allocated.
 179     */
 180    assert(offset > 0);
 181
 182    /* Allocating something with a size of 0 is also not valid. */
 183    assert(size > 0);
 184
 185    /* It's possible for offset + size to wrap around if we touch the top of
 186     * the 64-bit address space, but we cannot go any higher than 2^64.
 187     */
 188    assert(offset + size == 0 || offset + size > offset);
 189
 190    /* Find the hole if one exists. */
 191    util_vma_foreach_hole_safe(hole, heap) {
 192       if (hole->offset > offset)
 193          continue;
 194
 195       /* Holes are ordered high-to-low so the first hole we find with
 196        * hole->offset <= is our hole.  If it's not big enough to contain the
 197        * requested range, then the allocation fails.
 198        */
 199       assert(hole->offset <= offset);
 200       if (hole->size < offset - hole->offset + size)
 201          return false;
 202
 203       util_vma_hole_alloc(hole, offset, size);
 204       return true;
 205    }
 206
 207    /* We didn't find a suitable hole */
 208    return false;
 209 }
 210
 211 void
 212 util_vma_heap_free(struct util_vma_heap *heap,
 213                    uint64_t offset, uint64_t size)
 214 {
 215    /* An offset of 0 is reserved for allocation failure.  It is not a valid
 216     * address and cannot be freed.
 217     */
 218    assert(offset > 0);
 219
 220    /* Freeing something with a size of 0 is also not valid. */
 221    assert(size > 0);
 222
 223    /* It's possible for offset + size to wrap around if we touch the top of
 224     * the 64-bit address space, but we cannot go any higher than 2^64.
 225     */
 226    assert(offset + size == 0 || offset + size > offset);
 227
 228    util_vma_heap_validate(heap);
 229
 230    /* Find immediately higher and lower holes if they exist. */
 231    struct util_vma_hole *high_hole = NULL, *low_hole = NULL;
 232    util_vma_foreach_hole(hole, heap) {
 233       if (hole->offset <= offset) {
 234          low_hole = hole;
 235          break;
 236       }
 237       high_hole = hole;
 238    }
 239
 240    if (high_hole)
 241       assert(offset + size <= high_hole->offset);
 242    bool high_adjacent = high_hole && offset + size == high_hole->offset;
 243
 244    if (low_hole) {
 245       assert(low_hole->offset + low_hole->size > low_hole->offset);
 246       assert(low_hole->offset + low_hole->size <= offset);
 247    }
 248    bool low_adjacent = low_hole && low_hole->offset + low_hole->size == offset;
 249
 250    if (low_adjacent && high_adjacent) {
 251       /* Merge the two holes */
 252       low_hole->size += size + high_hole->size;
 253       list_del(&high_hole->link);
 254       free(high_hole);
 255    } else if (low_adjacent) {
 256       /* Merge into the low hole */
 257       low_hole->size += size;
 258    } else if (high_adjacent) {
 259       /* Merge into the high hole */
 260       high_hole->offset = offset;
 261       high_hole->size += size;
 262    } else {
 263       /* Neither hole is adjacent; make a new one */
 264       struct util_vma_hole *hole = calloc(1, sizeof(*hole));
 265
 266       hole->offset = offset;
 267       hole->size = size;
 268
 269       /* Add it after the high hole so we maintain high-to-low ordering */
 270       if (high_hole)
 271          list_add(&hole->link, &high_hole->link);
 272       else
 273          list_add(&hole->link, &heap->holes);
 274    }
 275
 276    util_vma_heap_validate(heap);
 277 }