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  1. /*
  2.  * Copyright (C) 2001-2004 Jakub Jermar
  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.  *
  9.  * - Redistributions of source code must retain the above copyright
  10.  *   notice, this list of conditions and the following disclaimer.
  11.  * - Redistributions in binary form must reproduce the above copyright
  12.  *   notice, this list of conditions and the following disclaimer in the
  13.  *   documentation and/or other materials provided with the distribution.
  14.  * - The name of the author may not be used to endorse or promote products
  15.  *   derived from this software without specific prior written permission.
  16.  *
  17.  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  18.  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  19.  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  20.  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  21.  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  22.  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  23.  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  24.  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25.  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  26.  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27.  */
  28.  
  29. #include <mm/heap.h>
  30. #include <synch/spinlock.h>
  31. #include <func.h>
  32. #include <memstr.h>
  33. #include <arch/types.h>
  34.  
  35. /*
  36.  * First-fit algorithm.
  37.  * Simple, but hopefully correct.
  38.  * Chunks being freed are tested for mergability with their neighbours.
  39.  */
  40.  
  41. static chunk_t *chunk0;
  42. static spinlock_t heaplock;
  43.  
  44. void heap_init(__address heap, int size)
  45. {
  46.     spinlock_initialize(&heaplock);
  47.     memsetb(heap,size,0);
  48.     chunk0 = (chunk_t *) heap;
  49.     chunk0->used = 0;
  50.     chunk0->size = size - sizeof(chunk_t);
  51.     chunk0->next = NULL;
  52.     chunk0->prev = NULL;
  53. }
  54.  
  55. /*
  56.  * Uses first-fit algorithm.
  57.  */
  58. void *malloc(int size)
  59. {
  60.     pri_t pri;
  61.     chunk_t *x, *y, *z;
  62.  
  63.     if (size == 0)
  64.         panic("malloc: zero-size allocation request");
  65.        
  66.     x = chunk0;
  67.     pri = cpu_priority_high();
  68.     spinlock_lock(&heaplock);      
  69.     while (x) {
  70.         if (x->used || x->size < size) {
  71.             x = x->next;
  72.             continue;
  73.         }
  74.        
  75.         x->used = 1;
  76.    
  77.         /*
  78.          * If the chunk exactly matches required size or if truncating
  79.          * it would not provide enough space for storing a new chunk
  80.          * header plus at least one byte of data, we are finished.
  81.          */
  82.         if (x->size < size + sizeof(chunk_t) + 1) {
  83.             spinlock_unlock(&heaplock);
  84.             cpu_priority_restore(pri);
  85.             return &x->data[0];
  86.         }
  87.  
  88.         /*
  89.          * Truncate x and create a new chunk.
  90.          */
  91.         y = (chunk_t *) (((__address) x) + size + sizeof(chunk_t));
  92.         y->used = 0;
  93.         y->size = x->size - size - sizeof(chunk_t);
  94.         y->prev = x;
  95.         y->next = NULL;
  96.        
  97.         if (z = x->next) {
  98.             z->prev = y;
  99.             y->next = z;
  100.         }
  101.        
  102.         x->size = size;
  103.         x->next = y;
  104.         spinlock_unlock(&heaplock);
  105.         cpu_priority_restore(pri);
  106.  
  107.         return &x->data[0];
  108.     }
  109.     spinlock_unlock(&heaplock);
  110.     cpu_priority_restore(pri);
  111.     return NULL;
  112. }
  113.  
  114. void free(void *ptr)
  115. {
  116.     pri_t pri;
  117.     chunk_t *x, *y, *z;
  118.  
  119.     if (!ptr)
  120.         panic("free on NULL");
  121.  
  122.  
  123.     y = (chunk_t *) (((__u8 *) ptr) - sizeof(chunk_t));
  124.     if (y->used != 1)
  125.         panic("freeing unused/damaged chunk");
  126.  
  127.     pri = cpu_priority_high();
  128.     spinlock_lock(&heaplock);
  129.     x = y->prev;
  130.     z = y->next;
  131.     /* merge x and y */
  132.     if (x && !x->used) {
  133.         x->size += y->size + sizeof(chunk_t);
  134.         x->next = z;
  135.         if (z)
  136.             z->prev = x;
  137.         y = x;
  138.     }
  139.     /* merge y and z or merge (x merged with y) and z */
  140.     if (z && !z->used) {
  141.         y->size += z->size + sizeof(chunk_t);
  142.         y->next = z->next;
  143.         if (z->next)  {
  144.             /* y is either y or x */
  145.             z->next->prev = y;
  146.         }
  147.     }
  148.     y->used = 0;
  149.     spinlock_unlock(&heaplock);
  150.     cpu_priority_restore(pri);
  151. }
  152.