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 uint64_t
  88 util_vma_heap_alloc(struct util_vma_heap *heap,
  89                     uint64_t size, uint64_t alignment)
  90 {
  91    /* The caller is expected to reject zero-size allocations */
  92    assert(size > 0);
  93    assert(alignment > 0);
  94
  95    util_vma_heap_validate(heap);
  96
  97    util_vma_foreach_hole_safe(hole, heap) {
  98       if (size > hole->size)
  99          continue;
 100
 101       /* Compute the offset as the highest address where a chunk of the given
 102        * size can be without going over the top of the hole.
 103        *
 104        * This calculation is known to not overflow because we know that
 105        * hole->size + hole->offset can only overflow to 0 and size > 0.
 106        */
 107       uint64_t offset = (hole->size - size) + hole->offset;
 108
 109       /* Align the offset.  We align down and not up because we are allocating
 110        * from the top of the hole and not the bottom.
 111        */
 112       offset = (offset / alignment) * alignment;
 113
 114       if (offset < hole->offset)
 115          continue;
 116
 117       if (offset == hole->offset && size == hole->size) {
 118          /* Just get rid of the hole. */
 119          list_del(&hole->link);
 120          free(hole);
 121          util_vma_heap_validate(heap);
 122          return offset;
 123       }
 124
 125       assert(offset - hole->offset <= hole->size - size);
 126       uint64_t waste = (hole->size - size) - (offset - hole->offset);
 127       if (waste == 0) {
 128          /* We allocated at the top.  Shrink the hole down. */
 129          hole->size -= size;
 130          util_vma_heap_validate(heap);
 131          return offset;
 132       }
 133
 134       if (offset == hole->offset) {
 135          /* We allocated at the bottom. Shrink the hole up. */
 136          hole->offset += size;
 137          hole->size -= size;
 138          util_vma_heap_validate(heap);
 139          return offset;
 140       }
 141
 142       /* We allocated in the middle.  We need to split the old hole into two
 143        * holes, one high and one low.
 144        */
 145       struct util_vma_hole *high_hole = calloc(1, sizeof(*hole));
 146       high_hole->offset = offset + size;
 147       high_hole->size = waste;
 148
 149       /* Adjust the hole to be the amount of space left at he bottom of the
 150        * original hole.
 151        */
 152       hole->size = offset - hole->offset;
 153
 154       /* Place the new hole before the old hole so that the list is in order
 155        * from high to low.
 156        */
 157       list_addtail(&high_hole->link, &hole->link);
 158
 159       util_vma_heap_validate(heap);
 160
 161       return offset;
 162    }
 163
 164    /* Failed to allocate */
 165    return 0;
 166 }
 167
 168 void
 169 util_vma_heap_free(struct util_vma_heap *heap,
 170                    uint64_t offset, uint64_t size)
 171 {
 172    /* An offset of 0 is reserved for allocation failure.  It is not a valid
 173     * address and cannot be freed.
 174     */
 175    assert(offset > 0);
 176
 177    /* Freeing something with a size of 0 is also not valid. */
 178    assert(size > 0);
 179
 180    /* It's possible for offset + size to wrap around if we touch the top of
 181     * the 64-bit address space, but we cannot go any higher than 2^64.
 182     */
 183    assert(offset + size == 0 || offset + size > offset);
 184
 185    util_vma_heap_validate(heap);
 186
 187    /* Find immediately higher and lower holes if they exist. */
 188    struct util_vma_hole *high_hole = NULL, *low_hole = NULL;
 189    util_vma_foreach_hole(hole, heap) {
 190       if (hole->offset <= offset) {
 191          low_hole = hole;
 192          break;
 193       }
 194       high_hole = hole;
 195    }
 196
 197    if (high_hole)
 198       assert(offset + size <= high_hole->offset);
 199    bool high_adjacent = high_hole && offset + size == high_hole->offset;
 200
 201    if (low_hole) {
 202       assert(low_hole->offset + low_hole->size > low_hole->offset);
 203       assert(low_hole->offset + low_hole->size <= offset);
 204    }
 205    bool low_adjacent = low_hole && low_hole->offset + low_hole->size == offset;
 206
 207    if (low_adjacent && high_adjacent) {
 208       /* Merge the two holes */
 209       low_hole->size += size + high_hole->size;
 210       list_del(&high_hole->link);
 211       free(high_hole);
 212    } else if (low_adjacent) {
 213       /* Merge into the low hole */
 214       low_hole->size += size;
 215    } else if (high_adjacent) {
 216       /* Merge into the high hole */
 217       high_hole->offset = offset;
 218       high_hole->size += size;
 219    } else {
 220       /* Neither hole is adjacent; make a new one */
 221       struct util_vma_hole *hole = calloc(1, sizeof(*hole));
 222
 223       hole->offset = offset;
 224       hole->size = size;
 225
 226       /* Add it after the high hole so we maintain high-to-low ordering */
 227       if (high_hole)
 228          list_add(&hole->link, &high_hole->link);
 229       else
 230          list_add(&hole->link, &heap->holes);
 231    }
 232
 233    util_vma_heap_validate(heap);
 234 }