mm.c

ReactOS是一些高手根据Windows XP的内核编写出的类XP。内核实现机理和API函数调用几乎相同。甚至可以兼容XP的程序。喜欢研究系统内核的人可以看一看。

/*
 *  FreeLoader
 *  Copyright (C) 1998-2003  Brian Palmer  <[e-mail]>
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include <freeldr.h>
#include <debug.h>

ULONG			AllocationCount = 0;

#ifdef DBG
VOID		VerifyHeap(VOID);
VOID		DumpMemoryAllocMap(VOID);
VOID		IncrementAllocationCount(VOID);
VOID		DecrementAllocationCount(VOID);
VOID		MemAllocTest(VOID);
#endif // DBG

/*
 * Hack alert
 * Normally, we allocate whole pages. This is ofcourse wastefull for small
 * allocations (a few bytes). So, for small allocations (smaller than a page)
 * we sub-allocate. When the first small allocation is done, a page is
 * requested. We keep a pointer to that page in SubAllocationPage. The alloc
 * is satisfied by returning a pointer to the beginning of the page. We also
 * keep track of how many bytes are still available in the page in SubAllocationRest.
 * When the next small request comes in, we try to allocate it just after the
 * memory previously allocated. If it won't fit, we allocate a new page and
 * the whole process starts again.
 * Note that suballocations are done back-to-back, there's no bookkeeping at all.
 * That also means that we cannot really free suballocations. So, when a free is
 * done and it is determined that this might be a free of a sub-allocation, we
 * just no-op the free.
 * Perhaps we should use the heap routines from ntdll here.
 */
static PVOID    SubAllocationPage = NULL;
static unsigned SubAllocationRest = 0;

BOOLEAN AllocateFromEnd = TRUE;

VOID MmChangeAllocationPolicy(BOOLEAN PolicyAllocatePagesFromEnd)
{
	AllocateFromEnd = PolicyAllocatePagesFromEnd;
}

PVOID MmAllocateMemory(ULONG MemorySize)
{
	ULONG	PagesNeeded;
	ULONG	FirstFreePageFromEnd;
	PVOID	MemPointer;

	if (MemorySize == 0)
	{
		DbgPrint((DPRINT_MEMORY, "MmAllocateMemory() called for 0 bytes. Returning NULL.\n"));
		UiMessageBoxCritical("Memory allocation failed: MmAllocateMemory() called for 0 bytes.");
		return NULL;
	}

	MemorySize = ROUND_UP(MemorySize, 4);
	if (MemorySize <= SubAllocationRest)
	{
		MemPointer = (PVOID)((ULONG_PTR)SubAllocationPage + MM_PAGE_SIZE - SubAllocationRest);
		SubAllocationRest -= MemorySize;
		return MemPointer;
	}

	// Find out how many blocks it will take to
	// satisfy this allocation
	PagesNeeded = ROUND_UP(MemorySize, MM_PAGE_SIZE) / MM_PAGE_SIZE;

	// If we don't have enough available mem
	// then return NULL
	if (FreePagesInLookupTable < PagesNeeded)
	{
		DbgPrint((DPRINT_MEMORY, "Memory allocation failed in MmAllocateMemory(). Not enough free memory to allocate %d bytes. AllocationCount: %d\n", MemorySize, AllocationCount));
		UiMessageBoxCritical("Memory allocation failed: out of memory.");
		return NULL;
	}

	FirstFreePageFromEnd = MmFindAvailablePages(PageLookupTableAddress, TotalPagesInLookupTable, PagesNeeded, AllocateFromEnd);

	if (FirstFreePageFromEnd == (ULONG)-1)
	{
		DbgPrint((DPRINT_MEMORY, "Memory allocation failed in MmAllocateMemory(). Not enough free memory to allocate %d bytes. AllocationCount: %d\n", MemorySize, AllocationCount));
		UiMessageBoxCritical("Memory allocation failed: out of memory.");
		return NULL;
	}

	MmAllocatePagesInLookupTable(PageLookupTableAddress, FirstFreePageFromEnd, PagesNeeded);

	FreePagesInLookupTable -= PagesNeeded;
	MemPointer = (PVOID)(FirstFreePageFromEnd * MM_PAGE_SIZE);

	if (MemorySize < MM_PAGE_SIZE)
	{
		SubAllocationPage = MemPointer;
		SubAllocationRest = MM_PAGE_SIZE - MemorySize;
	}
		

#ifdef DBG
	IncrementAllocationCount();
	DbgPrint((DPRINT_MEMORY, "Allocated %d bytes (%d pages) of memory starting at page %d. AllocCount: %d\n", MemorySize, PagesNeeded, FirstFreePageFromEnd, AllocationCount));
	DbgPrint((DPRINT_MEMORY, "Memory allocation pointer: 0x%x\n", MemPointer));
	//VerifyHeap();
#endif // DBG

	// Now return the pointer
	return MemPointer;
}

PVOID MmAllocateMemoryAtAddress(ULONG MemorySize, PVOID DesiredAddress)
{
	ULONG		PagesNeeded;
	ULONG		StartPageNumber;
	PVOID	MemPointer;

	if (MemorySize == 0)
	{
		DbgPrint((DPRINT_MEMORY, "MmAllocateMemoryAtAddress() called for 0 bytes. Returning NULL.\n"));
		UiMessageBoxCritical("Memory allocation failed: MmAllocateMemoryAtAddress() called for 0 bytes.");
		return NULL;
	}

	// Find out how many blocks it will take to
	// satisfy this allocation
	PagesNeeded = ROUND_UP(MemorySize, MM_PAGE_SIZE) / MM_PAGE_SIZE;

	// Get the starting page number
	StartPageNumber = MmGetPageNumberFromAddress(DesiredAddress);

	// If we don't have enough available mem
	// then return NULL
	if (FreePagesInLookupTable < PagesNeeded)
	{
		DbgPrint((DPRINT_MEMORY, "Memory allocation failed in MmAllocateMemoryAtAddress(). "
			"Not enough free memory to allocate %d bytes (requesting %d pages but have only %d). "
			"AllocationCount: %d\n", MemorySize, PagesNeeded, FreePagesInLookupTable, AllocationCount));
		UiMessageBoxCritical("Memory allocation failed: out of memory.");
		return NULL;
	}

	if (MmAreMemoryPagesAvailable(PageLookupTableAddress, TotalPagesInLookupTable, DesiredAddress, PagesNeeded) == FALSE)
	{
		DbgPrint((DPRINT_MEMORY, "Memory allocation failed in MmAllocateMemoryAtAddress(). "
			"Not enough free memory to allocate %d bytes at address %p. AllocationCount: %d\n",
			MemorySize, DesiredAddress, AllocationCount));

		// Don't tell this to user since caller should try to alloc this memory
		// at a different address
		//UiMessageBoxCritical("Memory allocation failed: out of memory.");
		return NULL;
	}

	MmAllocatePagesInLookupTable(PageLookupTableAddress, StartPageNumber, PagesNeeded);

	FreePagesInLookupTable -= PagesNeeded;
	MemPointer = (PVOID)(StartPageNumber * MM_PAGE_SIZE);

#ifdef DBG
	IncrementAllocationCount();
	DbgPrint((DPRINT_MEMORY, "Allocated %d bytes (%d pages) of memory starting at page %d. AllocCount: %d\n", MemorySize, PagesNeeded, StartPageNumber, AllocationCount));
	DbgPrint((DPRINT_MEMORY, "Memory allocation pointer: 0x%x\n", MemPointer));
	//VerifyHeap();
#endif // DBG

	// Now return the pointer
	return MemPointer;
}

PVOID MmAllocateHighestMemoryBelowAddress(ULONG MemorySize, PVOID DesiredAddress)
{
	ULONG		PagesNeeded;
	ULONG		FirstFreePageFromEnd;
	ULONG		DesiredAddressPageNumber;
	PVOID	MemPointer;

	if (MemorySize == 0)
	{
		DbgPrint((DPRINT_MEMORY, "MmAllocateHighestMemoryBelowAddress() called for 0 bytes. Returning NULL.\n"));
		UiMessageBoxCritical("Memory allocation failed: MmAllocateHighestMemoryBelowAddress() called for 0 bytes.");
		return NULL;
	}

	// Find out how many blocks it will take to
	// satisfy this allocation
	PagesNeeded = ROUND_UP(MemorySize, MM_PAGE_SIZE) / MM_PAGE_SIZE;

	// Get the page number for their desired address
	DesiredAddressPageNumber = (ULONG)DesiredAddress / MM_PAGE_SIZE;

	// If we don't have enough available mem
	// then return NULL
	if (FreePagesInLookupTable < PagesNeeded)
	{
		DbgPrint((DPRINT_MEMORY, "Memory allocation failed in MmAllocateHighestMemoryBelowAddress(). Not enough free memory to allocate %d bytes. AllocationCount: %d\n", MemorySize, AllocationCount));
		UiMessageBoxCritical("Memory allocation failed: out of memory.");
		return NULL;
	}

	FirstFreePageFromEnd = MmFindAvailablePagesBeforePage(PageLookupTableAddress, TotalPagesInLookupTable, PagesNeeded, DesiredAddressPageNumber);

	if (FirstFreePageFromEnd == 0)
	{
		DbgPrint((DPRINT_MEMORY, "Memory allocation failed in MmAllocateHighestMemoryBelowAddress(). Not enough free memory to allocate %d bytes. AllocationCount: %d\n", MemorySize, AllocationCount));
		UiMessageBoxCritical("Memory allocation failed: out of memory.");
		return NULL;
	}

	MmAllocatePagesInLookupTable(PageLookupTableAddress, FirstFreePageFromEnd, PagesNeeded);

	FreePagesInLookupTable -= PagesNeeded;
	MemPointer = (PVOID)(FirstFreePageFromEnd * MM_PAGE_SIZE);

#ifdef DBG
	IncrementAllocationCount();
	DbgPrint((DPRINT_MEMORY, "Allocated %d bytes (%d pages) of memory starting at page %d. AllocCount: %d\n", MemorySize, PagesNeeded, FirstFreePageFromEnd, AllocationCount));
	DbgPrint((DPRINT_MEMORY, "Memory allocation pointer: 0x%x\n", MemPointer));
	//VerifyHeap();
#endif // DBG

	// Now return the pointer
	return MemPointer;
}

VOID MmFreeMemory(PVOID MemoryPointer)
{
	ULONG							PageNumber;
	ULONG							PageCount;
	ULONG							Idx;
	PPAGE_LOOKUP_TABLE_ITEM		RealPageLookupTable = (PPAGE_LOOKUP_TABLE_ITEM)PageLookupTableAddress;

#ifdef DBG