/*
 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 "Bios.h"
#include "BootConsoleIo.h"
#include "BootConfig.h"
#include "BootDebug.h"
#include "BootDefs.h"
#include "BootDiskIo.h"
#include "BootStrings.h"


byte SectorBuffer[TC_LB_SIZE];

#ifdef TC_BOOT_DEBUG_ENABLED
static bool SectorBufferInUse = false;

void AcquireSectorBuffer ()
{
	if (SectorBufferInUse)
		TC_THROW_FATAL_EXCEPTION;

	SectorBufferInUse = true;
}


void ReleaseSectorBuffer ()
{
	SectorBufferInUse = false;
}

#endif


bool IsLbaSupported (byte drive)
{
	static byte CachedDrive = TC_INVALID_BIOS_DRIVE;
	static bool CachedStatus;
	uint16 result = 0;

	if (CachedDrive == drive)
		goto ret;

	__asm
	{
		mov bx, 0x55aa
		mov dl, drive
		mov ah, 0x41
		int 0x13
		jc err
		mov result, bx
	err:
	}

	CachedDrive = drive;
	CachedStatus = (result == 0xaa55);
ret:
	return CachedStatus;
}


void PrintDiskError (BiosResult error, bool write, byte drive, const uint64 *sector, const ChsAddress *chs)
{
	PrintEndl();
	Print (write ? "Write" : "Read"); Print (" error:");
	Print (error);
	Print (" Drive:");
	Print (drive ^ 0x80);

	if (sector)
	{
		Print (" Sector:");
		Print (*sector);
	}

	if (chs)
	{
		Print (" CHS:");
		Print (*chs);
	}

	PrintEndl();
	Beep();
}


void Print (const ChsAddress &chs)
{
	Print (chs.Cylinder);
	PrintChar ('/');
	Print (chs.Head);
	PrintChar ('/');
	Print (chs.Sector);
}


void PrintSectorCountInMB (const uint64 &sectorCount)
{
	Print (sectorCount >> (TC_LB_SIZE_BIT_SHIFT_DIVISOR + 2)); Print (" MB ");
}


BiosResult ReadWriteSectors (bool write, uint16 bufferSegment, uint16 bufferOffset, byte drive, const ChsAddress &chs, byte sectorCount, bool silent)
{
	CheckStack();

	byte cylinderLow = (byte) chs.Cylinder;
	byte sector = chs.Sector;
	sector |= byte (chs.Cylinder >> 2) & 0xc0;
	byte function = write ? 0x03 : 0x02;

	BiosResult result;
	byte tryCount = TC_MAX_BIOS_DISK_IO_RETRIES;

	do
	{
		result = BiosResultSuccess;

		__asm
		{
			push es
			mov ax, bufferSegment
			mov	es, ax
			mov	bx, bufferOffset
			mov dl, drive
			mov ch, cylinderLow
			mov si, chs
			mov dh, [si].Head
			mov cl, sector
			mov	al, sectorCount
			mov	ah, function
			int	0x13
			jnc ok				// If CF=0, ignore AH to prevent issues caused by potential bugs in BIOSes
			mov	result, ah
		ok:
			pop es
		}

		if (result == BiosResultEccCorrected)
			result = BiosResultSuccess;

	// Some BIOSes report I/O errors prematurely in some cases
	} while (result != BiosResultSuccess && --tryCount != 0);

	if (!silent && result != BiosResultSuccess)
		PrintDiskError (result, write, drive, nullptr, &chs);

	return result;
}


BiosResult ReadWriteSectors (bool write, byte *buffer, byte drive, const ChsAddress &chs, byte sectorCount, bool silent)
{
	uint16 codeSeg;
	__asm mov codeSeg, cs
	return ReadWriteSectors (write, codeSeg, (uint16) buffer, drive, chs, sectorCount, silent);
}


BiosResult ReadSectors (byte *buffer, byte drive, const ChsAddress &chs, byte sectorCount, bool silent)
{
	return ReadWriteSectors (false, buffer, drive, chs, sectorCount, silent);
}


BiosResult WriteSectors (byte *buffer, byte drive, const ChsAddress &chs, byte sectorCount, bool silent)
{
	return ReadWriteSectors (true, buffer, drive, chs, sectorCount, silent);
}


static BiosResult ReadWriteSectors (bool write, BiosLbaPacket &dapPacket, byte drive, const uint64 &sector, uint16 sectorCount, bool silent)
{
	CheckStack();

	if (!IsLbaSupported (drive))
	{
		DriveGeometry geometry;

		BiosResult result = GetDriveGeometry (drive, geometry, silent);
		if (result != BiosResultSuccess)
			return result;

		ChsAddress chs;
		LbaToChs (geometry, sector, chs);
		return ReadWriteSectors (write, (uint16) (dapPacket.Buffer >> 16), (uint16) dapPacket.Buffer, drive, chs, sectorCount, silent);
	}

	dapPacket.Size = sizeof (dapPacket);
	dapPacket.Reserved = 0;
	dapPacket.SectorCount = sectorCount;
	dapPacket.Sector = sector;

	byte function = write ? 0x43 : 0x42;

	BiosResult result;
	byte tryCount = TC_MAX_BIOS_DISK_IO_RETRIES;

	do
	{
		result = BiosResultSuccess;

		__asm
		{
			mov	bx, 0x55aa
			mov	dl, drive
			mov si, [dapPacket]
			mov	ah, function
			xor al, al
			int	0x13
			jnc ok				// If CF=0, ignore AH to prevent issues caused by potential bugs in BIOSes
			mov	result, ah
		ok:
		}

		if (result == BiosResultEccCorrected)
			result = BiosResultSuccess;

	// Some BIOSes report I/O errors prematurely in some cases
	} while (result != BiosResultSuccess && --tryCount != 0);

	if (!silent && result != BiosResultSuccess)
		PrintDiskError (result, write, drive, &sector);

	return result;
}


static BiosResult ReadWriteSectors (bool write, byte *buffer, byte drive, const uint64 &sector, uint16 sectorCount, bool silent)
{
	BiosLbaPacket dapPacket;
	dapPacket.Buffer = (uint32) buffer;
	return ReadWriteSectors (write, dapPacket, drive, sector, sectorCount, silent);
}


BiosResult ReadWriteSectors (bool write, uint16 bufferSegment, uint16 bufferOffset, byte drive, const uint64 &sector, uint16 sectorCount, bool silent)
{
	BiosLbaPacket dapPacket;
	dapPacket.Buffer = ((uint32) bufferSegment << 16) | bufferOffset;
	return ReadWriteSectors (write, dapPacket, drive, sector, sectorCount, silent);
}

BiosResult ReadSectors (uint16 bufferSegment, uint16 bufferOffset, byte drive, const uint64 &sector, uint16 sectorCount, bool silent)
{
	return ReadWriteSectors (false, bufferSegment, bufferOffset, drive, sector, sectorCount, silent);
}


BiosResult ReadSectors (byte *buffer, byte drive, const uint64 &sector, uint16 sectorCount, bool silent)
{
	BiosResult result;
	uint16 codeSeg;
	__asm mov codeSeg, cs

	result = ReadSectors (BootStarted ? codeSeg : TC_BOOT_LOADER_ALT_SEGMENT, (uint16) buffer, drive, sector, sectorCount, silent);

	// Alternative segment is used to prevent memory corruption caused by buggy BIOSes
	if (!BootStarted)
		CopyMemory (TC_BOOT_LOADER_ALT_SEGMENT, (uint16) buffer, buffer, sectorCount * TC_LB_SIZE);

	return result;
}


BiosResult WriteSectors (byte *buffer, byte drive, const uint64 &sector, uint16 sectorCount, bool silent)
{
	return ReadWriteSectors (true, buffer, drive, sector, sectorCount, silent);
}


BiosResult GetDriveGeometry (byte drive, DriveGeometry &geometry, bool silent)
{
	CheckStack();

	byte maxCylinderLow, maxHead, maxSector;
	BiosResult result;
	__asm
	{
		push es
		mov dl, drive
		mov ah, 0x08
		int	0x13

		mov	result, ah
		mov maxCylinderLow, ch
		mov maxSector, cl
		mov maxHead, dh
		pop es
	}

	if (result == BiosResultSuccess)
	{
		geometry.Cylinders = (maxCylinderLow | (uint16 (maxSector & 0xc0) << 2)) + 1;
		geometry.Heads = maxHead + 1;
		geometry.Sectors = maxSector & ~0xc0;
	}
	else if (!silent)
	{
		Print ("Drive ");
		Print (drive ^ 0x80);
		Print (" not found: ");
		PrintErrorNoEndl ("");
		Print (result);
		PrintEndl();
	}

	return result;
}


void ChsToLba (const DriveGeometry &geometry, const ChsAddress &chs, uint64 &lba)
{
	lba.HighPart = 0;
	lba.LowPart = (uint32 (chs.Cylinder) * geometry.Heads + chs.Head) * geometry.Sectors + chs.Sector - 1;
}


void LbaToChs (const DriveGeometry &geometry, const uint64 &lba, ChsAddress &chs)
{
	chs.Sector = (byte) ((lba.LowPart % geometry.Sectors) + 1);
	uint32 ch = lba.LowPart / geometry.Sectors;
	chs.Head = (byte) (ch % geometry.Heads);
	chs.Cylinder = (uint16) (ch / geometry.Heads);
}


void PartitionEntryMBRToPartition (const PartitionEntryMBR &partEntry, Partition &partition)
{
	partition.Active = partEntry.BootIndicator == 0x80;
	partition.EndSector.HighPart = 0;
	partition.EndSector.LowPart = partEntry.StartLBA + partEntry.SectorCountLBA - 1;
	partition.SectorCount.HighPart = 0;
	partition.SectorCount.LowPart = partEntry.SectorCountLBA;
	partition.StartSector.HighPart = 0;
	partition.StartSector.LowPart = partEntry.StartLBA;
	partition.Type = partEntry.Type;
}


BiosResult ReadWriteMBR (bool write, byte drive, bool silent)
{
	uint64 mbrSector;
	mbrSector.HighPart = 0;
	mbrSector.LowPart = 0;

	if (write)
		return WriteSectors (SectorBuffer, drive, mbrSector, 1, silent);

	return ReadSectors (SectorBuffer, drive, mbrSector, 1, silent);		// Uses alternative segment
}


BiosResult GetDrivePartitions (byte drive, Partition *partitionArray, size_t partitionArrayCapacity, size_t &partitionCount, bool activeOnly, Partition *findPartitionFollowingThis, bool silent)
{
	Partition *followingPartition;
	Partition tmpPartition;

	if (findPartitionFollowingThis)
	{
		assert (partitionArrayCapacity == 1);
		partitionArrayCapacity = 0xff;
		followingPartition = partitionArray;
		partitionArray = &tmpPartition;

		followingPartition->Drive = TC_INVALID_BIOS_DRIVE;
		followingPartition->StartSector.LowPart = 0xFFFFffffUL;
	}

	AcquireSectorBuffer();
	BiosResult result = ReadWriteMBR (false, drive, silent);
	ReleaseSectorBuffer();

	partitionCount = 0;

	MBR *mbr = (MBR *) SectorBuffer;
	if (result != BiosResultSuccess || mbr->Signature != 0xaa55)
		return result;

	PartitionEntryMBR mbrPartitions[4];
	memcpy (mbrPartitions, mbr->Partitions, sizeof (mbrPartitions));
	size_t partitionArrayPos = 0, partitionNumber;

	for (partitionNumber = 0;
		partitionNumber < array_capacity (mbrPartitions) && partitionArrayPos < partitionArrayCapacity;
		++partitionNumber)
	{
		const PartitionEntryMBR &partEntry = mbrPartitions[partitionNumber];

		if (partEntry.SectorCountLBA > 0)
		{
			Partition &partition = partitionArray[partitionArrayPos];
			PartitionEntryMBRToPartition (partEntry, partition);

			if (activeOnly && !partition.Active)
				continue;

			partition.Drive = drive;
			partition.Number = partitionArrayPos;

			if (partEntry.Type == 0x5 || partEntry.Type == 0xf) // Extended partition
			{
				if (IsLbaSupported (drive))
				{
					// Find all extended partitions
					uint64 firstExtStartLBA = partition.StartSector;
					uint64 extStartLBA = partition.StartSector;
					MBR *extMbr = (MBR *) SectorBuffer;

					while (partitionArrayPos < partitionArrayCapacity &&
						(result = ReadSectors ((byte *) extMbr, drive, extStartLBA, 1, silent)) == BiosResultSuccess
						&& extMbr->Signature == 0xaa55)
					{
						if (extMbr->Partitions[0].SectorCountLBA > 0)
						{
							Partition &logPart = partitionArray[partitionArrayPos];
							PartitionEntryMBRToPartition (extMbr->Partitions[0], logPart);
							logPart.Drive = drive;

							logPart.Number = partitionArrayPos;
							logPart.Primary = false;

							logPart.StartSector.LowPart += extStartLBA.LowPart;
							logPart.EndSector.LowPart += extStartLBA.LowPart;

							if (findPartitionFollowingThis)
							{
								if (logPart.StartSector.LowPart > findPartitionFollowingThis->EndSector.LowPart
									&& logPart.StartSector.LowPart < followingPartition->StartSector.LowPart)
								{
									*followingPartition = logPart;
								}
							}
							else
								++partitionArrayPos;
						}

						// Secondary extended
						if (extMbr->Partitions[1].Type != 0x5 && extMbr->Partitions[1].Type == 0xf
							|| extMbr->Partitions[1].SectorCountLBA == 0)
							break;

						extStartLBA.LowPart = extMbr->Partitions[1].StartLBA + firstExtStartLBA.LowPart;
					}
				}
			}
			else
			{
				partition.Primary = true;

				if (findPartitionFollowingThis)
				{
					if (partition.StartSector.LowPart > findPartitionFollowingThis->EndSector.LowPart
						&& partition.StartSector.LowPart < followingPartition->StartSector.LowPart)
					{
						*followingPartition = partition;
					}
				}
				else
					++partitionArrayPos;
			}
		}
	}

	partitionCount = partitionArrayPos;
	return result;
}


bool GetActivePartition (byte drive)
{
	size_t partCount;

	if (GetDrivePartitions (drive, &ActivePartition, 1, partCount, true) != BiosResultSuccess || partCount < 1)
	{
		ActivePartition.Drive = TC_INVALID_BIOS_DRIVE;
		PrintError (TC_BOOT_STR_NO_BOOT_PARTITION);
		return false;
	}

	return true;
}