haiku/src/system/kernel/heap.cpp

/*
 * Copyright 2008, Michael Lotz, mmlr@mlotz.ch.
 * Distributed under the terms of the MIT License.
 *
 * Copyright 2002-2006, Axel Dörfler, axeld@pinc-software.de.
 * Distributed under the terms of the MIT License.
 *
 * Copyright 2001, Travis Geiselbrecht. All rights reserved.
 * Distributed under the terms of the NewOS License.
 */
#include <debug.h>
#include <heap.h>
#include <int.h>
#include <kernel.h>
#include <lock.h>
#include <malloc.h>
#include <signal.h>
#include <string.h>
#include <team.h>
#include <thread.h>
#include <tracing.h>
#include <vm.h>

//#define TRACE_HEAP
#ifdef TRACE_HEAP
#	define TRACE(x) dprintf x
#else
#	define TRACE(x) ;
#endif

// initialize newly allocated memory with something non zero
#define PARANOID_KMALLOC 1
// check for double free, and fill freed memory with 0xdeadbeef
#define PARANOID_KFREE 1
// validate sanity of the heap after each operation (slow!)
#define PARANOID_VALIDATION 0
// store size, thread and team info at the end of each allocation block
#define KERNEL_HEAP_LEAK_CHECK 0

#if KERNEL_HEAP_LEAK_CHECK
typedef struct heap_leak_check_info_s {
	size_t		size;
	thread_id	thread;
	team_id		team;
} heap_leak_check_info;
#endif

typedef struct heap_page_s {
	uint16			index;
	uint16			bin_index : 5;
	uint16			free_count : 10;
	uint16			in_use : 1;
	heap_page_s *	next;
	heap_page_s *	prev;
	uint16			empty_index;
	addr_t *		free_list;
} heap_page;

// used for bin == bin_count allocations
#define allocation_id free_count

typedef struct heap_bin_s {
	uint32		element_size;
	uint16		max_free_count;
	heap_page *	page_list; // sorted so that the desired page is always first
} heap_bin;

typedef struct heap_allocator_s {
	addr_t		base;
	size_t		size;
	mutex		lock;
	vint32		large_alloc_id;

	uint32		bin_count;
	uint32		page_count;
	heap_page *	free_pages;

	heap_bin *	bins;
	heap_page *	page_table;

	heap_allocator_s *	next;
} heap_allocator;

static heap_allocator *sHeapList = NULL;
static heap_allocator *sLastGrowRequest = NULL;
static sem_id sHeapGrowSem = -1;
static sem_id sHeapGrownNotify = -1;


// #pragma mark - Tracing

#ifdef KERNEL_HEAP_TRACING
namespace KernelHeapTracing {

class Allocate : public AbstractTraceEntry {
	public:
		Allocate(addr_t address, size_t size)
			:	fAddress(address),
				fSize(size)
		{
			Initialized();
		}

		virtual void AddDump(TraceOutput &out)
		{
			out.Print("heap allocate: 0x%08lx (%lu bytes)", fAddress, fSize);
		}

	private:
		addr_t	fAddress;
		size_t	fSize;
};


class Reallocate : public AbstractTraceEntry {
	public:
		Reallocate(addr_t oldAddress, addr_t newAddress, size_t newSize)
			:	fOldAddress(oldAddress),
				fNewAddress(newAddress),
				fNewSize(newSize)
		{
			Initialized();
		};

		virtual void AddDump(TraceOutput &out)
		{
			out.Print("heap reallocate: 0x%08lx -> 0x%08lx (%lu bytes)",
				fOldAddress, fNewAddress, fNewSize);
		}

	private:
		addr_t	fOldAddress;
		addr_t	fNewAddress;
		size_t	fNewSize;
};


class Free : public AbstractTraceEntry {
	public:
		Free(addr_t address)
			:	fAddress(address)
		{
			Initialized();
		};

		virtual void AddDump(TraceOutput &out)
		{
			out.Print("heap free: 0x%08lx", fAddress);
		}

	private:
		addr_t	fAddress;
};


} // namespace KernelHeapTracing

#	define T(x)	if (!kernel_startup) new(std::nothrow) KernelHeapTracing::x;
#else
#	define T(x)	;
#endif


// #pragma mark - Debug functions


static void
dump_page(heap_page *page)
{
	uint32 count = 0;
	for (addr_t *temp = page->free_list; temp != NULL; temp = (addr_t *)*temp)
		count++;

	dprintf("\t\tpage %p: bin_index: %u; free_count: %u; empty_index: %u; free_list %p (%lu entr%s)\n",
		page, page->bin_index, page->free_count, page->empty_index,
		page->free_list, count, count == 1 ? "y" : "ies");
}


static void
dump_bin(heap_bin *bin)
{
	dprintf("\telement_size: %lu; max_free_count: %u; page_list %p;\n",
		bin->element_size, bin->max_free_count, bin->page_list);

	for (heap_page *temp = bin->page_list; temp != NULL; temp = temp->next)
		dump_page(temp);
}


static void
dump_allocator(heap_allocator *heap)
{
	uint32 count = 0;
	for (heap_page *page = heap->free_pages; page != NULL; page = page->next)
		count++;

	dprintf("allocator %p: base: 0x%08lx; size: %lu; bin_count: %lu; free_pages: %p (%lu entr%s)\n", heap,
		heap->base, heap->size, heap->bin_count, heap->free_pages, count,
		count == 1 ? "y" : "ies");

	for (uint32 i = 0; i < heap->bin_count; i++)
		dump_bin(&heap->bins[i]);

	dprintf("\n");
}


static int
dump_heap_list(int argc, char **argv)
{
	heap_allocator *heap = sHeapList;
	while (heap) {
		dump_allocator(heap);
		heap = heap->next;
	}

	return 0;
}


#if KERNEL_HEAP_LEAK_CHECK
static int
dump_allocations(int argc, char **argv)
{
	team_id team = -1;
	thread_id thread = -1;
	if (argc == 3) {
		if (strcmp(argv[1], "team") == 0)
			team = strtoul(argv[2], NULL, 0);
		else if (strcmp(argv[1], "thread") == 0)
			thread = strtoul(argv[2], NULL, 0);
		else {
			print_debugger_command_usage(argv[0]);
			return 0;
		}
	} else if (argc != 1) {
		print_debugger_command_usage(argv[0]);
		return 0;
	}

	size_t totalSize = 0;
	uint32 totalCount = 0;
	heap_allocator *heap = sHeapList;
	while (heap) {
		// go through all the pages
		heap_leak_check_info *info = NULL;
		for (uint32 i = 0; i < heap->page_count; i++) {
			heap_page *page = &heap->page_table[i];
			if (!page->in_use)
				continue;

			addr_t base = heap->base + i * B_PAGE_SIZE;
			if (page->bin_index < heap->bin_count) {
				// page is used by a small allocation bin
				uint32 elementCount = page->empty_index;
				size_t elementSize = heap->bins[page->bin_index].element_size;
				for (uint32 j = 0; j < elementCount; j++, base += elementSize) {
					// walk the free list to see if this element is in use
					bool elementInUse = true;
					for (addr_t *temp = page->free_list; temp != NULL; temp = (addr_t *)*temp) {
						if ((addr_t)temp == base) {
							elementInUse = false;
							break;
						}
					}

					if (!elementInUse)
						continue;

					info = (heap_leak_check_info *)(base + elementSize
						- sizeof(heap_leak_check_info));

					if ((team == -1 && thread == -1)
						|| (team == -1 && info->thread == thread)
						|| (thread == -1 && info->team == team)) {
						// interesting...
						dprintf("team: % 6ld; thread: % 6ld; address: 0x%08lx; size: %lu bytes\n",
							info->team, info->thread, base, info->size);
						totalSize += info->size;
						totalCount++;
					}
				}
			} else {
				// page is used by a big allocation, find the page count
				uint32 pageCount = 1;
				while (i + pageCount < heap->page_count
					&& heap->page_table[i + pageCount].in_use
					&& heap->page_table[i + pageCount].bin_index == heap->bin_count
					&& heap->page_table[i + pageCount].allocation_id == page->allocation_id)
					pageCount++;

				info = (heap_leak_check_info *)(base + pageCount * B_PAGE_SIZE
					- sizeof(heap_leak_check_info));

				if ((team == -1 && thread == -1)
					|| (team == -1 && info->thread == thread)
					|| (thread == -1 && info->team == team)) {
					// interesting...
					dprintf("team: % 6ld; thread: % 6ld; address: 0x%08lx; size: %lu bytes\n",
						info->team, info->thread, base, info->size);
					totalSize += info->size;
					totalCount++;
				}

				// skip the allocated pages
				i += pageCount - 1;
			}
		}

		heap = heap->next;
	}

	dprintf("total allocations: %lu; total bytes: %lu\n", totalCount, totalSize);
	return 0;
}
#endif // KERNEL_HEAP_LEAK_CHECK


#if PARANOID_VALIDATION
static void
heap_validate_heap(heap_allocator *heap)
{
	mutex_lock(&heap->lock);

	// validate the free pages list
	uint32 freePageCount = 0;
	heap_page *lastPage = NULL;
	heap_page *page = heap->free_pages;
	while (page) {
		if ((addr_t)page < (addr_t)&heap->page_table[0]
			|| (addr_t)page >= (addr_t)&heap->page_table[heap->page_count])
			panic("free page is not part of the page table\n");

		if (page->index >= heap->page_count)
			panic("free page has invalid index\n");

		if ((addr_t)&heap->page_table[page->index] != (addr_t)page)
			panic("free page index does not lead to target page\n");

		if (page->prev != lastPage)
			panic("free page entry has invalid prev link\n");

		if (page->in_use)
			panic("free page marked as in use\n");

		lastPage = page;
		page = page->next;
		freePageCount++;
	}

	// validate the page table
	uint32 usedPageCount = 0;
	for (uint32 i = 0; i < heap->page_count; i++) {
		if (heap->page_table[i].in_use)
			usedPageCount++;
	}

	if (freePageCount + usedPageCount != heap->page_count) {
		panic("free pages and used pages do not add up (%lu + %lu != %lu)\n",
			freePageCount, usedPageCount, heap->page_count);
	}

	// validate the bins
	for (uint32 i = 0; i < heap->bin_count; i++) {
		heap_bin *bin = &heap->bins[i];

		lastPage = NULL;
		page = bin->page_list;
		int32 lastFreeCount = 0;
		while (page) {
			if ((addr_t)page < (addr_t)&heap->page_table[0]
				|| (addr_t)page >= (addr_t)&heap->page_table[heap->page_count])
				panic("used page is not part of the page table\n");

			if (page->index >= heap->page_count)
				panic("used page has invalid index\n");

			if ((addr_t)&heap->page_table[page->index] != (addr_t)page)
				panic("used page index does not lead to target page\n");

			if (page->prev != lastPage)
				panic("used page entry has invalid prev link (%p vs %p bin %lu)\n",
					page->prev, lastPage, i);

			if (!page->in_use)
				panic("used page marked as not in use\n");

			if (page->bin_index != i)
				panic("used page with bin index %u in page list of bin %lu\n",
					page->bin_index, i);

			if (page->free_count < lastFreeCount)
				panic("ordering of bin page list broken\n");

			// validate the free list
			uint32 freeSlotsCount = 0;
			addr_t *element = page->free_list;
			addr_t pageBase = heap->base + page->index * B_PAGE_SIZE;
			while (element) {
				if ((addr_t)element < pageBase
					|| (addr_t)element >= pageBase + B_PAGE_SIZE)
					panic("free list entry out of page range\n");

				if (((addr_t)element - pageBase) % bin->element_size != 0)
					panic("free list entry not on a element boundary\n");

				element = (addr_t *)*element;
				freeSlotsCount++;
			}

			uint32 slotCount = bin->max_free_count;
			if (page->empty_index > slotCount)
				panic("empty index beyond slot count (%u with %lu slots)\n",
					page->empty_index, slotCount);

			freeSlotsCount += (slotCount - page->empty_index);
			if (freeSlotsCount > slotCount)
				panic("more free slots than fit into the page\n");

			lastPage = page;
			lastFreeCount = page->free_count;
			page = page->next;
		}
	}

	mutex_unlock(&heap->lock);
}
#endif // PARANOID_VALIDATION


// #pragma mark - Heap functions


heap_allocator *
heap_attach(addr_t base, size_t size, bool postSem)
{
	heap_allocator *heap = (heap_allocator *)base;
	base += sizeof(heap_allocator);
	size -= sizeof(heap_allocator);

	size_t binSizes[] = { 16, 32, 64, 96, 128, 192, 256, 384, 512, 1024, 2048, B_PAGE_SIZE };
	uint32 binCount = sizeof(binSizes) / sizeof(binSizes[0]);
	heap->bin_count = binCount;
	heap->bins = (heap_bin *)base;
	base += binCount * sizeof(heap_bin);
	size -= binCount * sizeof(heap_bin);

	for (uint32 i = 0; i < binCount; i++) {
		heap_bin *bin = &heap->bins[i];
		bin->element_size = binSizes[i];
		bin->max_free_count = B_PAGE_SIZE / binSizes[i];
		bin->page_list = NULL;
	}

	uint32 pageCount = size / B_PAGE_SIZE;
	size_t pageTableSize = pageCount * sizeof(heap_page);
	heap->page_table = (heap_page *)base;
	base += pageTableSize;
	size -= pageTableSize;

	// the rest is now actually usable memory (rounded to the next page)
	heap->base = (addr_t)(base + B_PAGE_SIZE - 1) / B_PAGE_SIZE * B_PAGE_SIZE;
	heap->size = (size_t)(size / B_PAGE_SIZE) * B_PAGE_SIZE;

	// now we know the real page count
	pageCount = heap->size / B_PAGE_SIZE;
	heap->page_count = pageCount;

	// zero out the heap alloc table at the base of the heap
	memset((void *)heap->page_table, 0, pageTableSize);
	for (uint32 i = 0; i < pageCount; i++)
		heap->page_table[i].index = i;

	// add all pages up into the free pages list
	for (uint32 i = 1; i < pageCount; i++) {
		heap->page_table[i - 1].next = &heap->page_table[i];
		heap->page_table[i].prev = &heap->page_table[i - 1];
	}
	heap->free_pages = &heap->page_table[0];
	heap->page_table[0].prev = NULL;

	if (postSem) {
		if (mutex_init(&heap->lock, "heap_mutex") < 0) {
			panic("heap_attach(): error creating heap mutex\n");
			return NULL;
		}
	} else {
		// pre-init the mutex to at least fall through any semaphore calls
		heap->lock.sem = -1;
		heap->lock.holder = -1;
	}

	heap->next = NULL;
	dprintf("heap_attach: attached to %p - usable range 0x%08lx - 0x%08lx\n",
		heap, heap->base, heap->base + heap->size);
	return heap;
}


static inline uint32
heap_next_alloc_id(heap_allocator *heap)
{
	return atomic_add(&heap->large_alloc_id, 1) & ((1 << 9) - 1);
}


static inline void
heap_link_page(heap_page *page, heap_page **list)
{
	page->prev = NULL;
	page->next = *list;
	if (page->next)
		page->next->prev = page;
	*list = page;
}


static inline void
heap_unlink_page(heap_page *page, heap_page **list)
{
	if (page->prev)
		page->prev->next = page->next;
	if (page->next)
		page->next->prev = page->prev;
	if (list && *list == page) {
		*list = page->next;
		if (page->next)
			page->next->prev = NULL;
	}
}


static void *
heap_raw_alloc(heap_allocator *heap, size_t size, uint32 binIndex)
{
	heap_bin *bin = NULL;
	if (binIndex < heap->bin_count)
		bin = &heap->bins[binIndex];

	if (bin && bin->page_list != NULL) {
		// we have a page where we have a free slot
		void *address = NULL;
		heap_page *page = bin->page_list;
		if (page->free_list) {
			// there's a previously freed entry we can use
			address = page->free_list;
			page->free_list = (addr_t *)*page->free_list;
		} else {
			// the page hasn't been fully allocated so use the next empty_index
			address = (void *)(heap->base + page->index * B_PAGE_SIZE
				+ page->empty_index * bin->element_size);
			page->empty_index++;
		}

		page->free_count--;
		if (page->free_count == 0) {
			// the page is now full so we remove it from the page_list
			bin->page_list = page->next;
			if (page->next)
				page->next->prev = NULL;
			page->next = page->prev = NULL;
		}

#if KERNEL_HEAP_LEAK_CHECK
		heap_leak_check_info *info = (heap_leak_check_info *)((addr_t)address
			+ bin->element_size - sizeof(heap_leak_check_info));
		info->size = size - sizeof(heap_leak_check_info);
		info->thread = (kernel_startup ? 0 : thread_get_current_thread_id());
		info->team = (kernel_startup ? 0 : team_get_current_team_id());
#endif
		return address;
	}

	// we don't have anything free right away, we must allocate a new page
	if (heap->free_pages == NULL) {
		// there are no free pages anymore, we ran out of memory
		TRACE(("heap %p: no free pages to allocate %lu bytes\n", heap, size));
		return NULL;
	}

	if (bin) {
		// small allocation, just grab the next free page
		heap_page *page = heap->free_pages;
		heap->free_pages = page->next;
		if (page->next)
			page->next->prev = NULL;

		page->in_use = 1;
		page->bin_index = binIndex;
		page->free_count = bin->max_free_count - 1;
		page->empty_index = 1;
		page->free_list = NULL;
		page->next = page->prev = NULL;

		if (page->free_count > 0) {
			// by design there are no other pages in the bins page list
			bin->page_list = page;
		}

#if KERNEL_HEAP_LEAK_CHECK
		heap_leak_check_info *info = (heap_leak_check_info *)(heap->base
			+ page->index * B_PAGE_SIZE + bin->element_size
			- sizeof(heap_leak_check_info));
		info->size = size - sizeof(heap_leak_check_info);
		info->thread = (kernel_startup ? 0 : thread_get_current_thread_id());
		info->team = (kernel_startup ? 0 : team_get_current_team_id());
#endif

		// we return the first slot in this page
		return (void *)(heap->base + page->index * B_PAGE_SIZE);
	}

	// large allocation, we must search for contiguous slots
	bool found = false;
	int32 first = -1;
	for (uint32 i = 0; i < heap->page_count; i++) {
		if (heap->page_table[i].in_use) {
			first = -1;
			continue;
		}

		if (first > 0) {
			if ((1 + i - first) * B_PAGE_SIZE >= size) {
				found = true;
				break;
			}
		} else
			first = i;
	}

	if (!found) {
		TRACE(("heap %p: found no contiguous pages to allocate %ld bytes\n", heap, size));
		return NULL;
	}

	uint32 allocationID = heap_next_alloc_id(heap);
	uint32 pageCount = (size + B_PAGE_SIZE - 1) / B_PAGE_SIZE;
	for (uint32 i = first; i < first + pageCount; i++) {
		heap_page *page = &heap->page_table[i];
		page->in_use = 1;
		page->bin_index = binIndex;

		heap_unlink_page(page, &heap->free_pages);

		page->next = page->prev = NULL;
		page->free_list = NULL;
		page->allocation_id = allocationID;
	}

#if KERNEL_HEAP_LEAK_CHECK
	heap_leak_check_info *info = (heap_leak_check_info *)(heap->base
		+ (first + pageCount) * B_PAGE_SIZE - sizeof(heap_leak_check_info));
	info->size = size - sizeof(heap_leak_check_info);
	info->thread = (kernel_startup ? 0 : thread_get_current_thread_id());
	info->team = (kernel_startup ? 0 : team_get_current_team_id());
#endif
	return (void *)(heap->base + first * B_PAGE_SIZE);
}


#if DEBUG
static bool
is_valid_alignment(size_t number)
{
	// this cryptic line accepts zero and all powers of two
	return ((~number + 1) | ((number << 1) - 1)) == ~0UL;
}
#endif


static void *
heap_memalign(heap_allocator *heap, size_t alignment, size_t size,
	bool *shouldGrow)
{
	TRACE(("memalign(alignment = %lu, size = %lu)\n", alignment, size));

#if DEBUG
	if (!is_valid_alignment(alignment))
		panic("memalign() with an alignment which is not a power of 2\n");
#endif

	mutex_lock(&heap->lock);

#if KERNEL_HEAP_LEAK_CHECK
	size += sizeof(heap_leak_check_info);
#endif

	// ToDo: that code "aligns" the buffer because the bins are always
	//	aligned on their bin size
	if (size < alignment)
		size = alignment;

	uint32 binIndex;
	for (binIndex = 0; binIndex < heap->bin_count; binIndex++) {
		if (size <= heap->bins[binIndex].element_size)
			break;
	}

	void *address = heap_raw_alloc(heap, size, binIndex);

	TRACE(("memalign(): asked to allocate %lu bytes, returning pointer %p\n", size, address));

	if (heap->next == NULL) {
		// suggest growing if we are the last heap and we have
		// less than three free pages left
		*shouldGrow = (heap->free_pages == NULL
			|| heap->free_pages->next == NULL
			|| heap->free_pages->next->next == NULL);
	}

#if KERNEL_HEAP_LEAK_CHECK
	size -= sizeof(heap_leak_check_info);
#endif

	T(Allocate((addr_t)address, size));
	mutex_unlock(&heap->lock);
	if (address == NULL)
		return address;

#if PARANOID_KFREE
	// make sure 0xdeadbeef is cleared if we do not overwrite the memory
	// and the user does not clear it
	if (((uint32 *)address)[1] == 0xdeadbeef)
		((uint32 *)address)[1] = 0xcccccccc;
#endif

#if PARANOID_KMALLOC
	memset(address, 0xcc, size);
#endif

	return address;
}


static status_t
heap_free(heap_allocator *heap, void *address)
{
	if (address == NULL)
		return B_OK;

	if ((addr_t)address < heap->base
		|| (addr_t)address >= heap->base + heap->size) {
		// this address does not belong to us
		return B_ENTRY_NOT_FOUND;
	}

	mutex_lock(&heap->lock);

	TRACE(("free(): asked to free at ptr = %p\n", address));

	heap_page *page = &heap->page_table[((addr_t)address - heap->base) / B_PAGE_SIZE];

	TRACE(("free(): page %p: bin_index %d, free_count %d\n", page, page->bin_index, page->free_count));

	if (page->bin_index > heap->bin_count) {
		panic("free(): page %p: invalid bin_index %d\n", page, page->bin_index);
		mutex_unlock(&heap->lock);
		return B_ERROR;
	}

	if (page->bin_index < heap->bin_count) {
		// small allocation
		heap_bin *bin = &heap->bins[page->bin_index];
		if (((addr_t)address - heap->base - page->index * B_PAGE_SIZE) % bin->element_size != 0) {
			panic("free(): passed invalid pointer %p supposed to be in bin for element size %ld\n", address, bin->element_size);
			mutex_unlock(&heap->lock);
			return B_ERROR;
		}

#if PARANOID_KFREE
		if (((uint32 *)address)[1] == 0xdeadbeef) {
			// This block looks like it was freed already, walk the free list
			// on this page to make sure this address doesn't exist.
			for (addr_t *temp = page->free_list; temp != NULL; temp = (addr_t *)*temp) {
				if (temp == address) {
					panic("free(): address %p already exists in page free list\n", address);
					mutex_unlock(&heap->lock);
					return B_ERROR;
				}
			}
		}

		uint32 *dead = (uint32 *)address;
		if (bin->element_size % 4 != 0) {
			panic("free(): didn't expect a bin element size that is not a multiple of 4\n");
			mutex_unlock(&heap->lock);
			return B_ERROR;
		}

		// the first 4 bytes are overwritten with the next free list pointer later
		for (uint32 i = 1; i < bin->element_size / sizeof(uint32); i++)
			dead[i] = 0xdeadbeef;
#endif

		// add the address to the page free list
		*(addr_t *)address = (addr_t)page->free_list;
		page->free_list = (addr_t *)address;
		page->free_count++;

		if (page->free_count == bin->max_free_count) {
			// we are now empty, remove the page from the bin list
			heap_unlink_page(page, &bin->page_list);
			page->in_use = 0;
			heap_link_page(page, &heap->free_pages);
		} else if (page->free_count == 1) {
			// we need to add ourselfs to the page list of the bin
			heap_link_page(page, &bin->page_list);
		} else {
			// we might need to move back in the free pages list
			if (page->next && page->next->free_count < page->free_count) {
				// move ourselfs so the list stays ordered
				heap_page *insert = page->next;
				while (insert->next
					&& insert->next->free_count < page->free_count)
					insert = insert->next;

				heap_unlink_page(page, &bin->page_list);

				page->prev = insert;
				page->next = insert->next;
				if (page->next)
					page->next->prev = page;
				insert->next = page;
			}
		}
	} else {
		// large allocation, just return the pages to the page free list
		uint32 allocationID = page->allocation_id;
		uint32 maxPages = heap->page_count - page->index;
		for (uint32 i = 0; i < maxPages; i++) {
			// loop until we find the end of this allocation
			if (!page[i].in_use || page[i].bin_index != heap->bin_count
				|| page[i].allocation_id != allocationID)
				break;

			// this page still belongs to the same allocation
			page[i].in_use = 0;
			page[i].allocation_id = 0;

			// return it to the free list
			heap_link_page(&page[i], &heap->free_pages);
		}
	}

	T(Free((addr_t)address));
	mutex_unlock(&heap->lock);
	return B_OK;
}


static status_t
heap_realloc(heap_allocator *heap, void *address, void **newAddress,
	size_t newSize)
{
	if ((addr_t)address < heap->base
		|| (addr_t)address >= heap->base + heap->size) {
		// this address does not belong to us
		return B_ENTRY_NOT_FOUND;
	}

	mutex_lock(&heap->lock);
	TRACE(("realloc(address = %p, newSize = %lu)\n", address, newSize));

	heap_page *page = &heap->page_table[((addr_t)address - heap->base) / B_PAGE_SIZE];
	if (page->bin_index > heap->bin_count) {
		panic("realloc(): page %p: invalid bin_index %d\n", page, page->bin_index);
		mutex_unlock(&heap->lock);
		return B_ERROR;
	}

	// find out the size of the old allocation first
	size_t minSize = 0;
	size_t maxSize = 0;
	if (page->bin_index < heap->bin_count) {
		// this was a small allocation
		heap_bin *bin = &heap->bins[page->bin_index];
		maxSize = bin->element_size;
		if (page->bin_index > 0)
			minSize = heap->bins[page->bin_index - 1].element_size + 1;
	} else {
		// this was a large allocation
		uint32 allocationID = page->allocation_id;
		uint32 maxPages = heap->page_count - page->index;
		maxSize = B_PAGE_SIZE;
		for (uint32 i = 1; i < maxPages; i++) {
			if (!page[i].in_use || page[i].bin_index != heap->bin_count
				|| page[i].allocation_id != allocationID)
				break;

			minSize += B_PAGE_SIZE;
			maxSize += B_PAGE_SIZE;
		}
	}

	mutex_unlock(&heap->lock);

#if KERNEL_HEAP_LEAK_CHECK
	newSize += sizeof(heap_leak_check_info);
#endif

	// does the new allocation simply fit in the old allocation?
	if (newSize > minSize && newSize <= maxSize) {
#if KERNEL_HEAP_LEAK_CHECK
		// update the size info (the info is at the end so stays where it is)
		heap_leak_check_info *info = (heap_leak_check_info *)((addr_t)address + maxSize);
		info->size = newSize - sizeof(heap_leak_check_info);
		newSize -= sizeof(heap_leak_check_info);
#endif

		T(Reallocate((addr_t)address, (addr_t)address, newSize));
		*newAddress = address;
		return B_OK;
	}

#if KERNEL_HEAP_LEAK_CHECK
	// new leak check info will be created with the malloc below
	newSize -= sizeof(heap_leak_check_info);
#endif

	// if not, allocate a new chunk of memory
	*newAddress = malloc(newSize);
	T(Reallocate((addr_t)address, (addr_t)*newAddress, newSize));
	if (*newAddress == NULL) {
		// we tried but it didn't work out, but still the operation is done
		return B_OK;
	}

	// copy the old data and free the old allocation
	memcpy(*newAddress, address, min_c(maxSize, newSize));
	free(address);
	return B_OK;
}


//	#pragma mark -


static int32
heap_grow_thread(void *)
{
	heap_allocator *heap = sHeapList;
	while (true) {
		// wait for a request to grow the heap list
		if (acquire_sem(sHeapGrowSem) < B_OK)
			continue;

		// find the last heap
		while (heap->next)
			heap = heap->next;

		if (sLastGrowRequest != heap) {
			// we have already grown since the latest request, just ignore
			continue;
		}

		TRACE(("heap_grower: kernel heap will run out of memory soon, allocating new one\n"));
		void *heapAddress = NULL;
		area_id heapArea = create_area("additional heap", &heapAddress,
			B_ANY_KERNEL_BLOCK_ADDRESS, HEAP_GROW_SIZE, B_FULL_LOCK,
			B_KERNEL_READ_AREA | B_KERNEL_WRITE_AREA);
		if (heapArea < B_OK) {
			panic("heap_grower: couldn't allocate additional heap area\n");
			continue;
		}

		heap_allocator *newHeap = heap_attach((addr_t)heapAddress,
			HEAP_GROW_SIZE, true);
		if (newHeap == NULL) {
			panic("heap_grower: could not attach additional heap!\n");
			delete_area(heapArea);
			continue;
		}

#if PARANOID_VALIDATION
		heap_validate_heap(newHeap);
#endif
		heap->next = newHeap;
		TRACE(("heap_grower: new heap linked in\n"));

		// notify anyone waiting for this request
		release_sem_etc(sHeapGrownNotify, -1, B_RELEASE_ALL);
	}

	return 0;
}


status_t
heap_init(addr_t base, size_t size)
{
	sHeapList = heap_attach(base, size, false);

	// set up some debug commands
	add_debugger_command("heap", &dump_heap_list, "Dump stats about the kernel heap(s)");
#if KERNEL_HEAP_LEAK_CHECK
	add_debugger_command_etc("allocations", &dump_allocations,
		"Dump current allocations", "[(\"team\" | \"thread\") <id>]\n"
		"If no parameters are given, all current alloactions are dumped.\n"
		"If either \"team\" or \"thread\" is specified as the first argument,\n"
		"only allocations matching the team or thread id given in the second\n"
		"argument are printed.\n", 0);
#endif
	return B_OK;
}


status_t
heap_init_post_sem()
{
	// create the lock for the initial heap
	if (mutex_init(&sHeapList->lock, "heap_mutex") < B_OK) {
		panic("heap_init_post_sem(): error creating heap mutex\n");
		return B_ERROR;
	}

	sHeapGrowSem = create_sem(0, "heap_grow_sem");
	if (sHeapGrowSem < 0) {
		panic("heap_init_post_sem(): failed to create heap grow sem\n");
		return B_ERROR;
	}

	sHeapGrownNotify = create_sem(0, "heap_grown_notify");
	if (sHeapGrownNotify < 0) {
		panic("heap_init_post_sem(): failed to create heap grown notify sem\n");
		return B_ERROR;
	}

	return B_OK;
}


status_t
heap_init_post_thread()
{
	thread_id thread = spawn_kernel_thread(heap_grow_thread, "heap grower",
		B_URGENT_PRIORITY, NULL);
	if (thread < 0) {
		panic("heap_init_post_thread(): cannot create heap grow thread\n");
		return B_ERROR;
	}

	send_signal_etc(thread, SIGCONT, B_DO_NOT_RESCHEDULE);
	return B_OK;
}


//	#pragma mark - Public API


void *
memalign(size_t alignment, size_t size)
{
	if (!kernel_startup && !are_interrupts_enabled()) {
		panic("memalign(): called with interrupts disabled\n");
		return NULL;
	}

	if (size > (HEAP_GROW_SIZE * 3) / 4) {
		// don't even attempt such a huge allocation
		panic("heap: huge allocation of %lu bytes asked!\n", size);
		return NULL;
	}

	heap_allocator *heap = sHeapList;
	while (heap) {
		bool shouldGrow = false;
		void *result = heap_memalign(heap, alignment, size, &shouldGrow);
		if (heap->next == NULL && (shouldGrow || result == NULL)) {
			// the last heap will or has run out of memory, notify the grower
			sLastGrowRequest = heap;
			if (result == NULL) {
				// urgent request, do the request and wait for at max 250ms
				release_sem(sHeapGrowSem);
				acquire_sem_etc(sHeapGrownNotify, 1, B_RELATIVE_TIMEOUT, 250000);
			} else {
				// not so urgent, just notify the grower
				release_sem_etc(sHeapGrowSem, 1, B_DO_NOT_RESCHEDULE);
			}
		}

		if (result == NULL) {
			heap = heap->next;
			continue;
		}

#if PARANOID_VALIDATION
		heap_validate_heap(heap);
#endif

		return result;
	}

	panic("heap: kernel heap has run out of memory\n");
	return NULL;
}


void *
malloc(size_t size)
{
	return memalign(0, size);
}


void
free(void *address)
{
	if (!kernel_startup && !are_interrupts_enabled()) {
		panic("free(): called with interrupts disabled\n");
		return;
	}

	heap_allocator *heap = sHeapList;
	while (heap) {
		if (heap_free(heap, address) == B_OK) {
#if PARANOID_VALIDATION
			heap_validate_heap(heap);
#endif
			return;
		}

		heap = heap->next;
	}

	panic("free(): free failed for address %p\n", address);
}


void *
realloc(void *address, size_t newSize)
{
	if (!kernel_startup && !are_interrupts_enabled()) {
		panic("realloc(): called with interrupts disabled\n");
		return NULL;
	}

	if (address == NULL)
		return malloc(newSize);

	if (newSize == 0) {
		free(address);
		return NULL;
	}

	heap_allocator *heap = sHeapList;
	while (heap) {
		void *newAddress = NULL;
		if (heap_realloc(heap, address, &newAddress, newSize) == B_OK) {
#if PARANOID_VALIDATION
			heap_validate_heap(heap);
#endif
			return newAddress;
		}

		heap = heap->next;
	}

	panic("realloc(): failed to realloc address %p to size %lu\n", address, newSize);
	return NULL;
}


void *
calloc(size_t numElements, size_t size)
{
	void *address = memalign(0, numElements * size);
	if (address != NULL)
		memset(address, 0, numElements * size);

	return address;
}