= GIET-VM / Kernel Malloc functions =

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The [source:soft/giet_vm/giet_common/kernel_malloc.c kernel_malloc.c] and [source:soft/giet_vm/giet_common/kernel_malloc.h kernel_malloc.h] files define the functions used by the kernel to dynamically allocate virtual memory from the kernel heaps distributed in each cluster. 

The '''kernel_heap[x][y]''' descriptors array is stored in the kernel_data segment in cluster[0][0]. Each entry [x][y] contains a heap descriptor (kernel_heap_t), defining the current heap state in cluster[x][y].
 * All kernel_heap[x][y) descriptors are initialized by the '''_heap_init()''' function, called by the '''_kernel_init()''' function.
 * All allocated blocks have a size that is a power of 2, larger or equal to MIN_BLOCK_SIZE (typically 64 bytes), and are aligned.
 * The memory allocation is done by the '''_remote_malloc()''' function, and there is no free mechanism.
 * Concurrent dynamic allocation is possible, as each kernel_heap[x][y] descriptor is protected by a specific queuing spin-lock. 


=== void '''_heap_init'''( ) ===
This function initialises the kernel_heap[x][y] descriptors array.
It must exist one heap vseg in each cluster. The vseg length must be a power of 2, and the vseg base address must be aligned.

=== void* '''_remote_malloc'''( unsigned int size, unsigned int x, unsigned int y ) === 
This function uses and updates the '''kernel_heap[x][y]''' array, and returns a pointer (virtual address) on a physical memory block located in cluster[x][y].
 * '''size''' : number of requested bytes
 * '''x''' : cluster X coordinate
 * '''y''' : cluster Y coordinate
The block size required can be any value, but the allocated block can be larger: the actual size is the smallest power of 2 value larger or equal to the requested size. The base address is always aligned. 
If no block satisfying the request is available it returns a NULL pointer.