drivemap.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>

#ifdef __i386__
BOOLEAN	DriveMapInstalled = FALSE;	// Tells us if we have already installed our drive map int 13h handler code
ULONG		OldInt13HandlerAddress = 0;	// Address of BIOS int 13h handler
ULONG		DriveMapHandlerAddress = 0;	// Linear address of our drive map handler
ULONG		DriveMapHandlerSegOff = 0;	// Segment:offset style address of our drive map handler

VOID DriveMapMapDrivesInSection(PCSTR SectionName)
{
	CHAR			SettingName[80];
	CHAR			SettingValue[80];
	CHAR			ErrorText[260];
	CHAR			Drive1[80];
	CHAR			Drive2[80];
	ULONG				SectionId;
	ULONG				SectionItemCount;
	ULONG				Index;
	ULONG				Index2;
	DRIVE_MAP_LIST	DriveMapList;

	RtlZeroMemory(&DriveMapList, sizeof(DRIVE_MAP_LIST));

	if (!IniOpenSection(SectionName, &SectionId))
	{
		return;
	}

	// Get the number of items in this section
	SectionItemCount = IniGetNumSectionItems(SectionId);

	// Loop through each one and check if its a DriveMap= setting
	for (Index=0; Index<SectionItemCount; Index++)
	{
		// Get the next setting from the .ini file section
		if (IniReadSettingByNumber(SectionId, Index, SettingName, sizeof(SettingName), SettingValue, sizeof(SettingValue)))
		{
			if (_stricmp(SettingName, "DriveMap") == 0)
			{
				// Make sure we haven't exceeded the drive map max count
				if (DriveMapList.DriveMapCount >= 4)
				{
					sprintf(ErrorText, "Max DriveMap count exceeded in section [%s]:\n\n%s=%s", SectionName, SettingName, SettingValue);
					UiMessageBox(ErrorText);
					continue;
				}

				RtlZeroMemory(Drive1, 80);
				RtlZeroMemory(Drive2, 80);

				strcpy(Drive1, SettingValue);

				// Parse the setting value and separate a string "hd0,hd1"
				// into two strings "hd0" and "hd1"
				for (Index2=0; Index2<strlen(Drive1); Index2++)
				{
					// Check if this character is the separater character (comma - ',')
					if (Drive1[Index2] == ',')
					{
						Drive1[Index2] = '\0';
						strcpy(Drive2, &Drive1[Index2+1]);
						break;
					}
				}

				// Make sure we got good values before we add them to the map
				if (!DriveMapIsValidDriveString(Drive1) || !DriveMapIsValidDriveString(Drive2))
				{
					sprintf(ErrorText, "Error in DriveMap setting in section [%s]:\n\n%s=%s", SectionName, SettingName, SettingValue);
					UiMessageBox(ErrorText);
					continue;
				}

				// Add them to the map
				DriveMapList.DriveMap[(DriveMapList.DriveMapCount * 2)] = DriveMapGetBiosDriveNumber(Drive1);
				DriveMapList.DriveMap[(DriveMapList.DriveMapCount * 2)+1] = DriveMapGetBiosDriveNumber(Drive2);
				DriveMapList.DriveMapCount++;

				DbgPrint((DPRINT_WARNING, "Mapping BIOS drive 0x%x to drive 0x%x\n", DriveMapGetBiosDriveNumber(Drive1), DriveMapGetBiosDriveNumber(Drive2)));
			}
		}
	}

	if (DriveMapList.DriveMapCount)
	{
		DbgPrint((DPRINT_WARNING, "Installing Int13 drive map for %d drives.\n", DriveMapList.DriveMapCount));
		DriveMapInstallInt13Handler(&DriveMapList);
	}
	else
	{
		DbgPrint((DPRINT_WARNING, "Removing any previously installed Int13 drive map.\n"));
		DriveMapRemoveInt13Handler();
	}
}

BOOLEAN DriveMapIsValidDriveString(PCSTR DriveString)
{
	ULONG		Index;

	// Now verify that the user has given us appropriate strings
	if ((strlen(DriveString) < 3) ||
		((DriveString[0] != 'f') && (DriveString[0] != 'F') && (DriveString[0] != 'h') && (DriveString[0] != 'H')) ||
		((DriveString[1] != 'd') && (DriveString[1] != 'D')))
	{
		return FALSE;
	}

	// Now verify that the user has given us appropriate numbers
	// Make sure that only numeric characters were given
	for (Index=2; Index<strlen(DriveString); Index++)
	{
		if (DriveString[Index] < '0' || DriveString[Index] > '9')
		{
			return FALSE;
		}
	}
	// Now make sure that they are not outrageous values (i.e. hd90874)
	if ((atoi(&DriveString[2]) < 0) || (atoi(&DriveString[2]) > 0xff))
	{
		return FALSE;
	}

	return TRUE;
}

ULONG DriveMapGetBiosDriveNumber(PCSTR DeviceName)
{
	ULONG		BiosDriveNumber = 0;

	// If they passed in a number string then just
	// convert it to decimal and return it
	if (DeviceName[0] >= '0' && DeviceName[0] <= '9')
	{
		return atoi(DeviceName);
	}

	// Convert the drive number string into a number
	// 'hd1' = 1
	BiosDriveNumber = atoi(&DeviceName[2]);

	// If it's a hard disk then set the high bit
	if ((DeviceName[0] == 'h' || DeviceName[0] == 'H') &&
		(DeviceName[1] == 'd' || DeviceName[1] == 'D'))
	{
		BiosDriveNumber |= 0x80;
	}

	return BiosDriveNumber;
}

VOID DriveMapInstallInt13Handler(PDRIVE_MAP_LIST DriveMap)
{
	ULONG*	RealModeIVT = (ULONG*)0x00000000;
	USHORT*	BiosLowMemorySize = (USHORT*)0x00000413;

	if (!DriveMapInstalled)
	{
		// Get the old INT 13h handler address from the vector table
		OldInt13HandlerAddress = RealModeIVT[0x13];

		// Decrease the size of low memory
		(*BiosLowMemorySize)--;

		// Get linear address for drive map handler
		DriveMapHandlerAddress = (ULONG)(*BiosLowMemorySize) << 10;

		// Convert to segment:offset style address
		DriveMapHandlerSegOff = (DriveMapHandlerAddress << 12) & 0xffff0000;
	}

	// Copy the drive map structure to the proper place
	RtlCopyMemory(&DriveMapInt13HandlerMapList, DriveMap, sizeof(DRIVE_MAP_LIST));

	// Set the address of the BIOS INT 13h handler
	DriveMapOldInt13HandlerAddress = OldInt13HandlerAddress;

	// Copy the code to our reserved area
	RtlCopyMemory((PVOID)DriveMapHandlerAddress, &DriveMapInt13HandlerStart, ((ULONG)&DriveMapInt13HandlerEnd - (ULONG)&DriveMapInt13HandlerStart));

	// Update the IVT
	RealModeIVT[0x13] = DriveMapHandlerSegOff;

	CacheInvalidateCacheData();
	DriveMapInstalled = TRUE;
}

VOID DriveMapRemoveInt13Handler(VOID)
{
	ULONG*	RealModeIVT = (ULONG*)0x00000000;
	USHORT*	BiosLowMemorySize = (USHORT*)0x00000413;

	if (DriveMapInstalled)
	{
		// Get the old INT 13h handler address from the vector table
		RealModeIVT[0x13] = OldInt13HandlerAddress;

		// Increase the size of low memory
		(*BiosLowMemorySize)++;

		CacheInvalidateCacheData();
		DriveMapInstalled = FALSE;
	}
}
#endif /* __i386__ */