lib/heap/heap.c - kernel/lk - Gitiles

 /*
  * Copyright (c) 2008-2009 Travis Geiselbrecht
  * Copyright (c) 2009 Corey Tabaka
  *
  * Permission is hereby granted, free of charge, to any person obtaining
  * a copy of this software and associated documentation files
  * (the "Software"), to deal in the Software without restriction,
  * including without limitation the rights to use, copy, modify, merge,
  * publish, distribute, sublicense, and/or sell copies of the Software,
  * and to permit persons to whom the Software is furnished to do so,
  * subject to the following conditions:
  *
  * The above copyright notice and this permission notice shall be
  * included in all copies or substantial portions of the Software.
  *
  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
  * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
  * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
  * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
  * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  */
 #include <debug.h>
 #include <err.h>
 #include <list.h>
 #include <rand.h>
 #include <string.h>
 #include <kernel/thread.h>
 #include <lib/heap.h>

 #define LOCAL_TRACE 0

 #define DEBUG_HEAP 0
 #define ALLOC_FILL 0x99
 #define FREE_FILL 0x77
 #define PADDING_FILL 0x55
 #define PADDING_SIZE 64

 #define ROUNDUP(a, b) (((a) + ((b)-1)) & ~((b)-1))

 #define HEAP_MAGIC 'HEAP'

 #if WITH_STATIC_HEAP

 #if !defined(HEAP_START) || !defined(HEAP_LEN)
 #error WITH_STATIC_HEAP set but no HEAP_START or HEAP_LEN defined
 #endif

 #else
 // end of the binary
 extern int _end;

 // end of memory
 extern int _end_of_ram;

 #define HEAP_START ((unsigned long)&_end)
 #define HEAP_LEN ((size_t)&_end_of_ram - (size_t)&_end)
 #endif

 struct free_heap_chunk {
 	struct list_node node;
 	size_t len;
 };

 struct heap {
 	void *base;
 	size_t len;
 	struct list_node free_list;
 };

 // heap static vars
 static struct heap theheap;

 // structure placed at the beginning every allocation
 struct alloc_struct_begin {
 	unsigned int magic;
 	void *ptr;
 	size_t size;
 #if DEBUG_HEAP
 	void *padding_start;
 	size_t padding_size;
 #endif
 };

 static void dump_free_chunk(struct free_heap_chunk *chunk)
 {
 	dprintf(INFO, "\t\tbase %p, end 0x%lx, len 0x%zx\n", chunk, (vaddr_t)chunk + chunk->len, chunk->len);
 }

 static void heap_dump(void)
 {
 	dprintf(INFO, "Heap dump:\n");
 	dprintf(INFO, "\tbase %p, len 0x%zx\n", theheap.base, theheap.len);
 	dprintf(INFO, "\tfree list:\n");

 	struct free_heap_chunk *chunk;
 	list_for_every_entry(&theheap.free_list, chunk, struct free_heap_chunk, node) {
 		dump_free_chunk(chunk);
 	}
 }

 static void heap_test(void)
 {
 	void *ptr[16];

 	ptr[0] = heap_alloc(8, 0);
 	ptr[1] = heap_alloc(32, 0);
 	ptr[2] = heap_alloc(7, 0);
 	ptr[3] = heap_alloc(0, 0);
 	ptr[4] = heap_alloc(98713, 0);
 	ptr[5] = heap_alloc(16, 0);

 	heap_free(ptr[5]);
 	heap_free(ptr[1]);
 	heap_free(ptr[3]);
 	heap_free(ptr[0]);
 	heap_free(ptr[4]);
 	heap_free(ptr[2]);

 	heap_dump();

 	int i;
 	for (i=0; i < 16; i++)
 		ptr[i] = 0;

 	for (i=0; i < 32768; i++) {
 		unsigned int index = (unsigned int)rand() % 16;

 		if ((i % (16*1024)) == 0)
 			printf("pass %d\n", i);

 //		printf("index 0x%x\n", index);
 		if (ptr[index]) {
 //			printf("freeing ptr[0x%x] = %p\n", index, ptr[index]);
 			heap_free(ptr[index]);
 			ptr[index] = 0;
 		}
 		unsigned int align = 1 << ((unsigned int)rand() % 8);
 		ptr[index] = heap_alloc((unsigned int)rand() % 32768, align);
 //		printf("ptr[0x%x] = %p, align 0x%x\n", index, ptr[index], align);

 		DEBUG_ASSERT(((addr_t)ptr[index] % align) == 0);
 //		heap_dump();
 	}

 	for (i=0; i < 16; i++) {
 		if (ptr[i])
 			heap_free(ptr[i]);
 	}

 	heap_dump();
 }

 // try to insert this free chunk into the free list, consuming the chunk by merging it with
 // nearby ones if possible. Returns base of whatever chunk it became in the list.
 static struct free_heap_chunk *heap_insert_free_chunk(struct free_heap_chunk *chunk)
 {
 #if DEBUG_HEAP
 	vaddr_t chunk_end = (vaddr_t)chunk + chunk->len;
 	dprintf(CRITICAL,"%s: chunk ptr %p, size 0x%lx, chunk_end 0x%x\n",
 				__FUNCTION__, chunk, chunk->len, chunk_end);
 #endif

 	struct free_heap_chunk *next_chunk;
 	struct free_heap_chunk *last_chunk;

 	// walk through the list, finding the node to insert before
 	list_for_every_entry(&theheap.free_list, next_chunk, struct free_heap_chunk, node) {
 		if (chunk < next_chunk) {
 			DEBUG_ASSERT(((vaddr_t)chunk + chunk->len) <= (vaddr_t)next_chunk);

 			list_add_before(&next_chunk->node, &chunk->node);

 			goto try_merge;
 		}
 	}

 	// walked off the end of the list, add it at the tail
 	list_add_tail(&theheap.free_list, &chunk->node);

 	// try to merge with the previous chunk
 try_merge:
 	last_chunk = list_prev_type(&theheap.free_list, &chunk->node, struct free_heap_chunk, node);
 	if (last_chunk) {
 		if ((vaddr_t)last_chunk + last_chunk->len == (vaddr_t)chunk) {
 			// easy, just extend the previous chunk
 			last_chunk->len += chunk->len;

 			// remove ourself from the list
 			list_delete(&chunk->node);

 			// set the chunk pointer to the newly extended chunk, in case
 			// it needs to merge with the next chunk below
 			chunk = last_chunk;
 		}
 	}

 	// try to merge with the next chunk
 	if (next_chunk) {
 		if ((vaddr_t)chunk + chunk->len == (vaddr_t)next_chunk) {
 			// extend our chunk
 			chunk->len += next_chunk->len;

 			// remove them from the list
 			list_delete(&next_chunk->node);
 		}
 	}

 	return chunk;
 }

 struct free_heap_chunk *heap_create_free_chunk(void *ptr, size_t len)
 {
 	DEBUG_ASSERT((len % sizeof(void *)) == 0); // size must be aligned on pointer boundary

 #if DEBUG_HEAP
 	memset(ptr, FREE_FILL, len);
 #endif

 	struct free_heap_chunk *chunk = (struct free_heap_chunk *)ptr;
 	chunk->len = len;

 	return chunk;
 }

 void *heap_alloc(size_t size, unsigned int alignment)
 {
 	void *ptr;
 #if DEBUG_HEAP
 	size_t original_size = size;
 #endif

 	LTRACEF("size %zd, align %d\n", size, alignment);

 	// alignment must be power of 2
 	if (alignment & (alignment - 1))
 		return NULL;

 	if(size > (size + sizeof(struct alloc_struct_begin)))
 	{
 		dprintf(CRITICAL, "invalid input size\n");
 		return NULL;
 	}
 	// we always put a size field + base pointer + magic in front of the allocation
 	size += sizeof(struct alloc_struct_begin);
 #if DEBUG_HEAP
 	size += PADDING_SIZE;
 #endif

 	// make sure we allocate at least the size of a struct free_heap_chunk so that
 	// when we free it, we can create a struct free_heap_chunk struct and stick it
 	// in the spot
 	if (size < sizeof(struct free_heap_chunk))
 		size = sizeof(struct free_heap_chunk);

 	// round up size to a multiple of native pointer size
 	size = ROUNDUP(size, sizeof(void *));

 	// deal with nonzero alignments
 	if (alignment > 0) {
 		if (alignment < 16)
 			alignment = 16;

 		// add alignment for worst case fit
 		if(size > (size + alignment))
 		{
 			dprintf(CRITICAL, "invalid input alignment\n");
 			return NULL;
 		}
 		size += alignment;
 	}

 	// critical section
 	enter_critical_section();

 	// walk through the list
 	ptr = NULL;
 	struct free_heap_chunk *chunk;
 	list_for_every_entry(&theheap.free_list, chunk, struct free_heap_chunk, node) {
 		DEBUG_ASSERT((chunk->len % sizeof(void *)) == 0); // len should always be a multiple of pointer size

 		// is it big enough to service our allocation?
 		if (chunk->len >= size) {
 			ptr = chunk;

 			// remove it from the list
 			struct list_node *next_node = list_next(&theheap.free_list, &chunk->node);
 			list_delete(&chunk->node);

 			if (chunk->len > size + sizeof(struct free_heap_chunk)) {
 				// there's enough space in this chunk to create a new one after the allocation
 				struct free_heap_chunk *newchunk = heap_create_free_chunk((uint8_t *)ptr + size, chunk->len - size);

 				// truncate this chunk
 				chunk->len -= chunk->len - size;

 				// add the new one where chunk used to be
 				if (next_node)
 					list_add_before(next_node, &newchunk->node);
 				else
 					list_add_tail(&theheap.free_list, &newchunk->node);
 			}

 			// the allocated size is actually the length of this chunk, not the size requested
 			DEBUG_ASSERT(chunk->len >= size);
 			size = chunk->len;

 #if DEBUG_HEAP
 			memset(ptr, ALLOC_FILL, size);
 #endif

 			ptr = (void *)((addr_t)ptr + sizeof(struct alloc_struct_begin));

 			// align the output if requested
 			if (alignment > 0) {
 				ptr = (void *)ROUNDUP((addr_t)ptr, alignment);
 			}

 			struct alloc_struct_begin *as = (struct alloc_struct_begin *)ptr;
 			as--;
 			as->magic = HEAP_MAGIC;
 			as->ptr = (void *)chunk;
 			as->size = size;
 #if DEBUG_HEAP
 			as->padding_start = ((uint8_t *)ptr + original_size);
 			as->padding_size = (((addr_t)chunk + size) - ((addr_t)ptr + original_size));
 //			printf("padding start %p, size %u, chunk %p, size %u\n", as->padding_start, as->padding_size, chunk, size);

 			memset(as->padding_start, PADDING_FILL, as->padding_size);
 #endif

 			break;
 		}
 	}

 	LTRACEF("returning ptr %p\n", ptr);

 //	heap_dump();

 	exit_critical_section();

 	return ptr;
 }

 void *heap_realloc(void *ptr, size_t size)
 {
 	void * tmp_ptr = NULL;
 	size_t min_size;
 	struct alloc_struct_begin *as = (struct alloc_struct_begin *)ptr;
 	as--;

 	if (size != 0){
 		tmp_ptr = heap_alloc(size, 0);
 		if (ptr != NULL && tmp_ptr != NULL){
 			min_size = (size < as->size) ? size : as->size;
 			memcpy(tmp_ptr, ptr, min_size);
 			heap_free(ptr);
 		}
 	} else {
 		if (ptr != NULL)
 			heap_free(ptr);
 	}
 	return(tmp_ptr);
 }


 void heap_free(void *ptr)
 {
 	if (ptr == 0)
 		return;

 	LTRACEF("ptr %p\n", ptr);

 	// check for the old allocation structure
 	struct alloc_struct_begin *as = (struct alloc_struct_begin *)ptr;
 	as--;

 	DEBUG_ASSERT(as->magic == HEAP_MAGIC);

 #if DEBUG_HEAP
 	{
 		uint i;
 		uint8_t *pad = (uint8_t *)as->padding_start;

 		for (i = 0; i < as->padding_size; i++) {
 			if (pad[i] != PADDING_FILL) {
 				printf("free at %p scribbled outside the lines:\n", ptr);
 				hexdump(pad, as->padding_size);
 				panic("die\n");
 			}
 		}
 	}
 #endif

 	LTRACEF("allocation was %zd bytes long at ptr %p\n", as->size, as->ptr);

 	// looks good, create a free chunk and add it to the pool
 	enter_critical_section();
 	heap_insert_free_chunk(heap_create_free_chunk(as->ptr, as->size));
 	exit_critical_section();

 //	heap_dump();
 }

 void heap_init(void)
 {
 	LTRACE_ENTRY;

 	// set the heap range
 	theheap.base = (void *)HEAP_START;
 	theheap.len = HEAP_LEN;

 	LTRACEF("base %p size %zd bytes\n", theheap.base, theheap.len);

 	// initialize the free list
 	list_initialize(&theheap.free_list);

 	// create an initial free chunk
 	heap_insert_free_chunk(heap_create_free_chunk(theheap.base, theheap.len));

 	// dump heap info
 //	heap_dump();

 //	dprintf(INFO, "running heap tests\n");
 //	heap_test();
 }

 #if DEBUGLEVEL > 1
 #if WITH_LIB_CONSOLE

 #include <lib/console.h>

 static int cmd_heap(int argc, const cmd_args *argv);

 STATIC_COMMAND_START
 STATIC_COMMAND("heap", "heap debug commands", &cmd_heap)
 STATIC_COMMAND_END(heap);

 static int cmd_heap(int argc, const cmd_args *argv)
 {
 	if (argc < 2) {
 		printf("not enough arguments\n");
 		return -1;
 	}

 	if (strcmp(argv[1].str, "info") == 0) {
 		heap_dump();
 	} else {
 		printf("unrecognized command\n");
 		return -1;
 	}

 	return 0;
 }

 #endif
 #endif
	/*
	* Copyright (c) 2008-2009 Travis Geiselbrecht
	* Copyright (c) 2009 Corey Tabaka
	*
	* Permission is hereby granted, free of charge, to any person obtaining
	* a copy of this software and associated documentation files
	* (the "Software"), to deal in the Software without restriction,
	* including without limitation the rights to use, copy, modify, merge,
	* publish, distribute, sublicense, and/or sell copies of the Software,
	* and to permit persons to whom the Software is furnished to do so,
	* subject to the following conditions:
	*
	* The above copyright notice and this permission notice shall be
	* included in all copies or substantial portions of the Software.
	*
	* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
	* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
	* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
	* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
	* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
	* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
	* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
	*/
	#include <debug.h>
	#include <err.h>
	#include <list.h>
	#include <rand.h>
	#include <string.h>
	#include <kernel/thread.h>
	#include <lib/heap.h>

	#define LOCAL_TRACE 0

	#define DEBUG_HEAP 0
	#define ALLOC_FILL 0x99
	#define FREE_FILL 0x77
	#define PADDING_FILL 0x55
	#define PADDING_SIZE 64

	#define ROUNDUP(a, b) (((a) + ((b)-1)) & ~((b)-1))

	#define HEAP_MAGIC 'HEAP'

	#if WITH_STATIC_HEAP

	#if !defined(HEAP_START) \|\| !defined(HEAP_LEN)
	#error WITH_STATIC_HEAP set but no HEAP_START or HEAP_LEN defined
	#endif

	#else
	// end of the binary
	extern int _end;

	// end of memory
	extern int _end_of_ram;

	#define HEAP_START ((unsigned long)&_end)
	#define HEAP_LEN ((size_t)&_end_of_ram - (size_t)&_end)
	#endif

	struct free_heap_chunk {
	struct list_node node;
	size_t len;
	};

	struct heap {
	void *base;
	size_t len;
	struct list_node free_list;
	};

	// heap static vars
	static struct heap theheap;

	// structure placed at the beginning every allocation
	struct alloc_struct_begin {
	unsigned int magic;
	void *ptr;
	size_t size;
	#if DEBUG_HEAP
	void *padding_start;
	size_t padding_size;
	#endif
	};

	static void dump_free_chunk(struct free_heap_chunk *chunk)
	{
	dprintf(INFO, "\t\tbase %p, end 0x%lx, len 0x%zx\n", chunk, (vaddr_t)chunk + chunk->len, chunk->len);
	}

	static void heap_dump(void)
	{
	dprintf(INFO, "Heap dump:\n");
	dprintf(INFO, "\tbase %p, len 0x%zx\n", theheap.base, theheap.len);
	dprintf(INFO, "\tfree list:\n");

	struct free_heap_chunk *chunk;
	list_for_every_entry(&theheap.free_list, chunk, struct free_heap_chunk, node) {
	dump_free_chunk(chunk);
	}
	}

	static void heap_test(void)
	{
	void *ptr[16];

	ptr[0] = heap_alloc(8, 0);
	ptr[1] = heap_alloc(32, 0);
	ptr[2] = heap_alloc(7, 0);
	ptr[3] = heap_alloc(0, 0);
	ptr[4] = heap_alloc(98713, 0);
	ptr[5] = heap_alloc(16, 0);

	heap_free(ptr[5]);
	heap_free(ptr[1]);
	heap_free(ptr[3]);
	heap_free(ptr[0]);
	heap_free(ptr[4]);
	heap_free(ptr[2]);

	heap_dump();

	int i;
	for (i=0; i < 16; i++)
	ptr[i] = 0;

	for (i=0; i < 32768; i++) {
	unsigned int index = (unsigned int)rand() % 16;

	if ((i % (16*1024)) == 0)
	printf("pass %d\n", i);

	// printf("index 0x%x\n", index);
	if (ptr[index]) {
	// printf("freeing ptr[0x%x] = %p\n", index, ptr[index]);
	heap_free(ptr[index]);
	ptr[index] = 0;
	}
	unsigned int align = 1 << ((unsigned int)rand() % 8);
	ptr[index] = heap_alloc((unsigned int)rand() % 32768, align);
	// printf("ptr[0x%x] = %p, align 0x%x\n", index, ptr[index], align);

	DEBUG_ASSERT(((addr_t)ptr[index] % align) == 0);
	// heap_dump();
	}

	for (i=0; i < 16; i++) {
	if (ptr[i])
	heap_free(ptr[i]);
	}

	heap_dump();
	}

	// try to insert this free chunk into the free list, consuming the chunk by merging it with
	// nearby ones if possible. Returns base of whatever chunk it became in the list.
	static struct free_heap_chunk heap_insert_free_chunk(struct free_heap_chunk chunk)
	{
	#if DEBUG_HEAP
	vaddr_t chunk_end = (vaddr_t)chunk + chunk->len;
	dprintf(CRITICAL,"%s: chunk ptr %p, size 0x%lx, chunk_end 0x%x\n",
	__FUNCTION__, chunk, chunk->len, chunk_end);
	#endif

	struct free_heap_chunk *next_chunk;
	struct free_heap_chunk *last_chunk;

	// walk through the list, finding the node to insert before
	list_for_every_entry(&theheap.free_list, next_chunk, struct free_heap_chunk, node) {
	if (chunk < next_chunk) {
	DEBUG_ASSERT(((vaddr_t)chunk + chunk->len) <= (vaddr_t)next_chunk);

	list_add_before(&next_chunk->node, &chunk->node);

	goto try_merge;
	}
	}

	// walked off the end of the list, add it at the tail
	list_add_tail(&theheap.free_list, &chunk->node);

	// try to merge with the previous chunk
	try_merge:
	last_chunk = list_prev_type(&theheap.free_list, &chunk->node, struct free_heap_chunk, node);
	if (last_chunk) {
	if ((vaddr_t)last_chunk + last_chunk->len == (vaddr_t)chunk) {
	// easy, just extend the previous chunk
	last_chunk->len += chunk->len;

	// remove ourself from the list
	list_delete(&chunk->node);

	// set the chunk pointer to the newly extended chunk, in case
	// it needs to merge with the next chunk below
	chunk = last_chunk;
	}
	}

	// try to merge with the next chunk
	if (next_chunk) {
	if ((vaddr_t)chunk + chunk->len == (vaddr_t)next_chunk) {
	// extend our chunk
	chunk->len += next_chunk->len;

	// remove them from the list
	list_delete(&next_chunk->node);
	}
	}

	return chunk;
	}

	struct free_heap_chunk heap_create_free_chunk(void ptr, size_t len)
	{
	DEBUG_ASSERT((len % sizeof(void *)) == 0); // size must be aligned on pointer boundary

	#if DEBUG_HEAP
	memset(ptr, FREE_FILL, len);
	#endif

	struct free_heap_chunk chunk = (struct free_heap_chunk )ptr;
	chunk->len = len;

	return chunk;
	}

	void *heap_alloc(size_t size, unsigned int alignment)
	{
	void *ptr;
	#if DEBUG_HEAP
	size_t original_size = size;
	#endif

	LTRACEF("size %zd, align %d\n", size, alignment);

	// alignment must be power of 2
	if (alignment & (alignment - 1))
	return NULL;

	if(size > (size + sizeof(struct alloc_struct_begin)))
	{
	dprintf(CRITICAL, "invalid input size\n");
	return NULL;
	}
	// we always put a size field + base pointer + magic in front of the allocation
	size += sizeof(struct alloc_struct_begin);
	#if DEBUG_HEAP
	size += PADDING_SIZE;
	#endif

	// make sure we allocate at least the size of a struct free_heap_chunk so that
	// when we free it, we can create a struct free_heap_chunk struct and stick it
	// in the spot
	if (size < sizeof(struct free_heap_chunk))
	size = sizeof(struct free_heap_chunk);

	// round up size to a multiple of native pointer size
	size = ROUNDUP(size, sizeof(void *));

	// deal with nonzero alignments
	if (alignment > 0) {
	if (alignment < 16)
	alignment = 16;

	// add alignment for worst case fit
	if(size > (size + alignment))
	{
	dprintf(CRITICAL, "invalid input alignment\n");
	return NULL;
	}
	size += alignment;
	}

	// critical section
	enter_critical_section();

	// walk through the list
	ptr = NULL;
	struct free_heap_chunk *chunk;
	list_for_every_entry(&theheap.free_list, chunk, struct free_heap_chunk, node) {
	DEBUG_ASSERT((chunk->len % sizeof(void *)) == 0); // len should always be a multiple of pointer size

	// is it big enough to service our allocation?
	if (chunk->len >= size) {
	ptr = chunk;

	// remove it from the list
	struct list_node *next_node = list_next(&theheap.free_list, &chunk->node);
	list_delete(&chunk->node);

	if (chunk->len > size + sizeof(struct free_heap_chunk)) {
	// there's enough space in this chunk to create a new one after the allocation
	struct free_heap_chunk newchunk = heap_create_free_chunk((uint8_t )ptr + size, chunk->len - size);

	// truncate this chunk
	chunk->len -= chunk->len - size;

	// add the new one where chunk used to be
	if (next_node)
	list_add_before(next_node, &newchunk->node);
	else
	list_add_tail(&theheap.free_list, &newchunk->node);
	}

	// the allocated size is actually the length of this chunk, not the size requested
	DEBUG_ASSERT(chunk->len >= size);
	size = chunk->len;

	#if DEBUG_HEAP
	memset(ptr, ALLOC_FILL, size);
	#endif

	ptr = (void *)((addr_t)ptr + sizeof(struct alloc_struct_begin));

	// align the output if requested
	if (alignment > 0) {
	ptr = (void *)ROUNDUP((addr_t)ptr, alignment);
	}

	struct alloc_struct_begin as = (struct alloc_struct_begin )ptr;
	as--;
	as->magic = HEAP_MAGIC;
	as->ptr = (void *)chunk;
	as->size = size;
	#if DEBUG_HEAP
	as->padding_start = ((uint8_t *)ptr + original_size);
	as->padding_size = (((addr_t)chunk + size) - ((addr_t)ptr + original_size));
	// printf("padding start %p, size %u, chunk %p, size %u\n", as->padding_start, as->padding_size, chunk, size);

	memset(as->padding_start, PADDING_FILL, as->padding_size);
	#endif

	break;
	}
	}

	LTRACEF("returning ptr %p\n", ptr);

	// heap_dump();

	exit_critical_section();

	return ptr;
	}

	void heap_realloc(void ptr, size_t size)
	{
	void * tmp_ptr = NULL;
	size_t min_size;
	struct alloc_struct_begin as = (struct alloc_struct_begin )ptr;
	as--;

	if (size != 0){
	tmp_ptr = heap_alloc(size, 0);
	if (ptr != NULL && tmp_ptr != NULL){
	min_size = (size < as->size) ? size : as->size;
	memcpy(tmp_ptr, ptr, min_size);
	heap_free(ptr);
	}
	} else {
	if (ptr != NULL)
	heap_free(ptr);
	}
	return(tmp_ptr);
	}


	void heap_free(void *ptr)
	{
	if (ptr == 0)
	return;

	LTRACEF("ptr %p\n", ptr);

	// check for the old allocation structure
	struct alloc_struct_begin as = (struct alloc_struct_begin )ptr;
	as--;

	DEBUG_ASSERT(as->magic == HEAP_MAGIC);

	#if DEBUG_HEAP
	{
	uint i;
	uint8_t pad = (uint8_t )as->padding_start;

	for (i = 0; i < as->padding_size; i++) {
	if (pad[i] != PADDING_FILL) {
	printf("free at %p scribbled outside the lines:\n", ptr);
	hexdump(pad, as->padding_size);
	panic("die\n");
	}
	}
	}
	#endif

	LTRACEF("allocation was %zd bytes long at ptr %p\n", as->size, as->ptr);

	// looks good, create a free chunk and add it to the pool
	enter_critical_section();
	heap_insert_free_chunk(heap_create_free_chunk(as->ptr, as->size));
	exit_critical_section();

	// heap_dump();
	}

	void heap_init(void)
	{
	LTRACE_ENTRY;

	// set the heap range
	theheap.base = (void *)HEAP_START;
	theheap.len = HEAP_LEN;

	LTRACEF("base %p size %zd bytes\n", theheap.base, theheap.len);

	// initialize the free list
	list_initialize(&theheap.free_list);

	// create an initial free chunk
	heap_insert_free_chunk(heap_create_free_chunk(theheap.base, theheap.len));

	// dump heap info
	// heap_dump();

	// dprintf(INFO, "running heap tests\n");
	// heap_test();
	}

	#if DEBUGLEVEL > 1
	#if WITH_LIB_CONSOLE

	#include <lib/console.h>

	static int cmd_heap(int argc, const cmd_args *argv);

	STATIC_COMMAND_START
	STATIC_COMMAND("heap", "heap debug commands", &cmd_heap)
	STATIC_COMMAND_END(heap);

	static int cmd_heap(int argc, const cmd_args *argv)
	{
	if (argc < 2) {
	printf("not enough arguments\n");
	return -1;
	}

	if (strcmp(argv[1].str, "info") == 0) {
	heap_dump();
	} else {
	printf("unrecognized command\n");
	return -1;
	}

	return 0;
	}

	#endif
	#endif