/*
 Derived from source code of TrueCrypt 7.1a, which is
 Copyright (c) 2008-2012 TrueCrypt Developers Association and which is governed
 by the TrueCrypt License 3.0.

 Modifications and additions to the original source code (contained in this file)
 and all other portions of this file are Copyright (c) 2013-2017 IDRIX
 and are governed by the Apache License 2.0 the full text of which is
 contained in the file License.txt included in VeraCrypt binary and source
 code distribution packages.
*/

#include "BootDefs.h"
#include "BootMemory.h"

static uint32 MemoryMapContValue;

static bool GetMemoryMapEntry (BiosMemoryMapEntry &entry)
{
	static const uint32 function = 0x0000E820UL;
	static const uint32 magic = 0x534D4150UL;
	static const uint32 bufferSize = sizeof (BiosMemoryMapEntry);

	bool carry = false;
	uint32 resultMagic;
	uint32 resultSize;

	__asm
	{
		push es

		lea di, function
		TC_ASM_MOV_EAX_DI
		lea di, MemoryMapContValue
		TC_ASM_MOV_EBX_DI
		lea di, bufferSize
		TC_ASM_MOV_ECX_DI
		lea di, magic
		TC_ASM_MOV_EDX_DI
		lea di, MemoryMapContValue
		TC_ASM_MOV_DI_ECX

		// Use alternative segment to prevent memory corruption caused by buggy BIOSes
		push TC_BOOT_LOADER_ALT_SEGMENT
		pop es
		mov di, 0

		int 0x15
		jnc no_carry
		mov carry, true
	no_carry:

		lea di, resultMagic
		TC_ASM_MOV_DI_EAX
		lea di, MemoryMapContValue
		TC_ASM_MOV_DI_EBX
		lea di, resultSize
		TC_ASM_MOV_DI_ECX

		pop es
	}

	CopyMemory (TC_BOOT_LOADER_ALT_SEGMENT, 0, &entry, sizeof (entry));

	// BIOS may set CF at the end of the list
	if (carry)
		MemoryMapContValue = 0;

	return resultMagic == magic && resultSize == bufferSize;
}


bool GetFirstBiosMemoryMapEntry (BiosMemoryMapEntry &entry)
{
	MemoryMapContValue = 0;
	return GetMemoryMapEntry (entry);
}


bool GetNextBiosMemoryMapEntry (BiosMemoryMapEntry &entry)
{
	if (MemoryMapContValue == 0)
		return false;

	return GetMemoryMapEntry (entry);
}