orion_old/kernel/kernel/kheap.c

#include "ordered_map.c"

extern uint32_t page_directory[1024];

#define KHEAP_START         0xC0000000
#define KHEAP_INITIAL_SIZE  0x100000
#define HEAP_INDEX_SIZE   0x20000
#define HEAP_MAGIC        0x123890AB
#define HEAP_MIN_SIZE     0x70000

typedef struct
{
   uint32_t magic;   // Magic number, used for error checking and identification.
   uint8_t is_hole;   // 1 if this is a hole. 0 if this is a block.
   uint32_t size;    // size of the block, including the end footer.
} header_t;

typedef struct
{
   uint32_t magic;     // Magic number, same as in header_t.
   header_t *header; // Pointer to the block header.
} footer_t;

typedef struct
{
   ordered_array_t index;
   uint32_t start_address; // The start of our allocated space.
   uint32_t end_address;   // The end of our allocated space. May be expanded up to max_address.
   uint32_t max_address;   // The maximum address the heap can be expanded to.
   uint8_t supervisor;     // Should extra pages requested by us be mapped as supervisor-only?
   uint8_t readonly;       // Should extra pages requested by us be mapped as read-only?
} heap_t;

heap_t *kheap;

static int32_t find_smallest_hole(uint32_t size, uint8_t page_align, heap_t *heap)
{
   // Find the smallest hole that will fit.
   uint32_t iterator = 0;
   while (iterator < heap->index.size)
   {
       header_t *header = (header_t *)lookup_ordered_array(iterator, &heap->index);
       // If the user has requested the memory be page-aligned
       if (page_align > 0)
       {
           // Page-align the starting point of this header.
           uint32_t location = (uint32_t)header;
           int32_t offset = 0;
           if (((location+sizeof(header_t)) & 0xFFFFF000) != 0)
               offset = 0x1000 /* page size */  - (location+sizeof(header_t))%0x1000;
           int32_t hole_size = (int32_t)header->size - offset;
           // Can we fit now?
           if (hole_size >= (int32_t)size)
               break;
       }
       else if (header->size >= size)
           break;
       iterator++;
   }
   // Why did the loop exit?
   if (iterator == heap->index.size)
       return -1; // We got to the end and didn't find anything.
   else
       return iterator;
}


static int8_t header_t_less_than(void*a, void *b)
{
   return (((header_t*)a)->size < ((header_t*)b)->size)?1:0;
}

heap_t *create_heap(uint32_t start, uint32_t end_addr, uint32_t max, uint8_t supervisor, uint8_t readonly)
{
   heap_t *heap = (heap_t*)kmalloc(sizeof(heap_t));

   // All our assumptions are made on startAddress and endAddress being page-aligned.
   assert(start%0x1000 == 0);
   assert(end_addr%0x1000 == 0);

   // Initialise the index.
   heap->index = place_ordered_array( (void*)start, HEAP_INDEX_SIZE, &header_t_less_than);

   // Shift the start address forward to resemble where we can start putting data.
   start += sizeof(type_t)*HEAP_INDEX_SIZE;

   // Make sure the start address is page-aligned.
   if ((start & 0xFFFFF000) != 0)
   {
       start &= 0xFFFFF000;
       start += 0x1000;
   }
   // Write the start, end and max addresses into the heap structure.
   heap->start_address = start;
   heap->end_address = end_addr;
   heap->max_address = max;
   heap->supervisor = supervisor;
   heap->readonly = readonly;

   // We start off with one large hole in the index.
   header_t *hole = (header_t *)start;
   hole->size = end_addr-start;
   hole->magic = HEAP_MAGIC;
   hole->is_hole = 1;
   insert_ordered_array((void*)hole, &heap->index);

   return heap;
}

static void expand(uint32_t new_size, heap_t *heap)
{
   // Sanity check.
   assert(new_size > heap->end_address - heap->start_address);
   // Get the nearest following page boundary.
   if ((new_size&0xFFFFF000) != 0)
   {
       new_size &= 0xFFFFF000;
       new_size += 0x1000;
   }
   // Make sure we are not overreaching ourselves.
   assert(heap->start_address+new_size <= heap->max_address);

   // This should always be on a page boundary.
   uint32_t old_size = heap->end_address-heap->start_address;
   uint32_t i = old_size;
   while (i < new_size)
   {
       alloc_frame( get_page(heap->start_address+i, 1, /*kernel*/page_directory),
                    (heap->supervisor)?1:0, (heap->readonly)?0:1);
       i += 0x1000 /* page size */;
   }
   heap->end_address = heap->start_address+new_size;
}

static uint32_t contract(uint32_t new_size, heap_t *heap)
{
   // Sanity check.
   assert(new_size < heap->end_address-heap->start_address);
   // Get the nearest following page boundary.
   if (new_size&0x1000)
   {
       new_size &= 0x1000;
       new_size += 0x1000;
   }
   // Don't contract too far!
   if (new_size < HEAP_MIN_SIZE)
       new_size = HEAP_MIN_SIZE;
   uint32_t old_size = heap->end_address-heap->start_address;
   uint32_t i = old_size - 0x1000;
   while (new_size < i)
   {
       free_frame(get_page(heap->start_address+i, 0, /*kernel*/page_directory)); 
       i -= 0x1000;
   }
   heap->end_address = heap->start_address + new_size;
   return new_size;
}

void *alloc(uint32_t size, uint8_t page_align, heap_t *heap)
{

   // Make sure we take the size of header/footer into account.
   uint32_t new_size = size + sizeof(header_t) + sizeof(footer_t);
   // Find the smallest hole that will fit.
   int32_t iterator = find_smallest_hole(new_size, page_align, heap);
   
   if (iterator == -1) // If we didn't find a suitable hole
   {
	// Save some previous data.
       uint32_t old_length = heap->end_address - heap->start_address;
       uint32_t old_end_address = heap->end_address;

       // We need to allocate some more space.
       expand(old_length+new_size, heap);
       uint32_t new_length = heap->end_address-heap->start_address;

       // Find the endmost header. (Not endmost in size, but in location).
       iterator = 0;
       // Vars to hold the index of, and value of, the endmost header found so far.
       uint32_t idx = -1; uint32_t value = 0x0;
       while (iterator < heap->index.size)
       {
           uint32_t tmp = (uint32_t)lookup_ordered_array(iterator, &heap->index);
           if (tmp > value)
           {
               value = tmp;
               idx = iterator;
           }
           iterator++;
       }

       // If we didn't find ANY headers, we need to add one.
       if (idx == -1)
       {
           header_t *header = (header_t *)old_end_address;
           header->magic = HEAP_MAGIC;
           header->size = new_length - old_length;
           header->is_hole = 1;
           footer_t *footer = (footer_t *) (old_end_address + header->size - sizeof(footer_t));
           footer->magic = HEAP_MAGIC;
           footer->header = header;
           insert_ordered_array((void*)header, &heap->index);
       }
       else
       {
           // The last header needs adjusting.
           header_t *header = lookup_ordered_array(idx, &heap->index);
           header->size += new_length - old_length;
           // Rewrite the footer.
           footer_t *footer = (footer_t *) ( (uint32_t)header + header->size - sizeof(footer_t) );
           footer->header = header;
           footer->magic = HEAP_MAGIC;
       }
       // We now have enough space. Recurse, and call the function again.
       return alloc(size, page_align, heap);
   }
   header_t *orig_hole_header = (header_t *)lookup_ordered_array(iterator, &heap->index);
   uint32_t orig_hole_pos = (uint32_t)orig_hole_header;
   uint32_t orig_hole_size = orig_hole_header->size;
   // Here we work out if we should split the hole we found into two parts.
   // Is the original hole size - requested hole size less than the overhead for adding a new hole?
   if (orig_hole_size-new_size < sizeof(header_t)+sizeof(footer_t))
   {
       // Then just increase the requested size to the size of the hole we found.
       size += orig_hole_size-new_size;
       new_size = orig_hole_size;
   }
   
   // If we need to page-align the data, do it now and make a new hole in front of our block.
   if (page_align && orig_hole_pos & 0xFFFFF000)
   {
       uint32_t new_location   = orig_hole_pos + 0x1000 /* page size */ - (orig_hole_pos&0xFFF) - sizeof(header_t);
       header_t *hole_header = (header_t *)orig_hole_pos;
       hole_header->size     = 0x1000 /* page size */ - (orig_hole_pos&0xFFF) - sizeof(header_t);
       hole_header->magic    = HEAP_MAGIC;
       hole_header->is_hole  = 1;
       footer_t *hole_footer = (footer_t *) ( (uint32_t)new_location - sizeof(footer_t) );
       hole_footer->magic    = HEAP_MAGIC;
       hole_footer->header   = hole_header;
       orig_hole_pos         = new_location;
       orig_hole_size        = orig_hole_size - hole_header->size;
   }
   else
   {
       // Else we don't need this hole any more, delete it from the index.
       remove_ordered_array(iterator, &heap->index);
   }

   // Overwrite the original header...
   header_t *block_header  = (header_t *)orig_hole_pos;
   block_header->magic     = HEAP_MAGIC;
   block_header->is_hole   = 0;
   block_header->size      = new_size;
   // ...And the footer
   footer_t *block_footer  = (footer_t *) (orig_hole_pos + sizeof(header_t) + size);
   block_footer->magic     = HEAP_MAGIC;
   block_footer->header    = block_header;

   // We may need to write a new hole after the allocated block.
   // We do this only if the new hole would have positive size...
   if (orig_hole_size - new_size > 0)
   {
       header_t *hole_header = (header_t *) (orig_hole_pos + sizeof(header_t) + size + sizeof(footer_t));
       hole_header->magic    = HEAP_MAGIC;
       hole_header->is_hole  = 1;
       hole_header->size     = orig_hole_size - new_size;
       footer_t *hole_footer = (footer_t *) ( (uint32_t)hole_header + orig_hole_size - new_size - sizeof(footer_t) );
       if ((uint32_t)hole_footer < heap->end_address)
       {
           hole_footer->magic = HEAP_MAGIC;
           hole_footer->header = hole_header;
       }
       // Put the new hole in the index;
       insert_ordered_array((void*)hole_header, &heap->index);
   }
	
   return (void *) ( (uint32_t)block_header+sizeof(header_t) );
}

void free(void *p, heap_t *heap)
{
   // Exit gracefully for null pointers.
   if (p == 0)
       return;

   // Get the header and footer associated with this pointer.
   header_t *header = (header_t*) ( (uint32_t)p - sizeof(header_t) );
   footer_t *footer = (footer_t*) ( (uint32_t)header + header->size - sizeof(footer_t) );

   // Sanity checks.
   assert(header->magic == HEAP_MAGIC);
   assert(footer->magic == HEAP_MAGIC);

   // Make us a hole.
   header->is_hole = 1;

   // Do we want to add this header into the 'free holes' index?
   char do_add = 1;

   // Unify left
   // If the thing immediately to the left of us is a footer...
   footer_t *test_footer = (footer_t*) ( (uint32_t)header - sizeof(footer_t) );
   if (test_footer->magic == HEAP_MAGIC &&
       test_footer->header->is_hole == 1)
   {
       uint32_t cache_size = header->size; // Cache our current size.
       header = test_footer->header;     // Rewrite our header with the new one.
       footer->header = header;          // Rewrite our footer to point to the new header.
       header->size += cache_size;       // Change the size.
       do_add = 0;                       // Since this header is already in the index, we don't want to add it again.
   }

   // Unify right
   // If the thing immediately to the right of us is a header...
   header_t *test_header = (header_t*) ( (uint32_t)footer + sizeof(footer_t) );
   if (test_header->magic == HEAP_MAGIC &&
       test_header->is_hole)
   {
       header->size += test_header->size; // Increase our size.
       test_footer = (footer_t*) ( (uint32_t)test_header + // Rewrite it's footer to point to our header.
                                   test_header->size - sizeof(footer_t) );
       footer = test_footer;
       // Find and remove this header from the index.
       uint32_t iterator = 0;
       while ( (iterator < heap->index.size) &&
               (lookup_ordered_array(iterator, &heap->index) != (void*)test_header) )
           iterator++;

       // Make sure we actually found the item.
       assert(iterator < heap->index.size);
       // Remove it.
       remove_ordered_array(iterator, &heap->index);
   }

      // If the footer location is the end address, we can contract.
   if ( (uint32_t)footer+sizeof(footer_t) == heap->end_address)
   {
       uint32_t old_length = heap->end_address-heap->start_address;
       uint32_t new_length = contract( (uint32_t)header - heap->start_address, heap);
       // Check how big we will be after resizing.
       if (header->size - (old_length-new_length) > 0)
       {
           // We will still exist, so resize us.
           header->size -= old_length-new_length;
           footer = (footer_t*) ( (uint32_t)header + header->size - sizeof(footer_t) );
           footer->magic = HEAP_MAGIC;
           footer->header = header;
       }
       else
       {
           // We will no longer exist :(. Remove us from the index.
           uint32_t iterator = 0;
           while ( (iterator < heap->index.size) &&
                   (lookup_ordered_array(iterator, &heap->index) != (void*)test_header) )
               iterator++;
           // If we didn't find ourselves, we have nothing to remove.
           if (iterator < heap->index.size)
               remove_ordered_array(iterator, &heap->index);
       }
   }
   if (do_add == 1)
   	insert_ordered_array((void*) header, &heap->index);
}