GBA-Exploader/ndsbootloader/source/dldi_patcher.c

/*-----------------------------------------------------------------

 Copyright (C) 2005  Michael "Chishm" Chisholm

 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., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.

 If you use this code, please give due credit and email me about your
 project at chishm@hotmail.com
------------------------------------------------------------------*/
#ifndef NO_DLDI
#include <string.h>
#include <nds.h>
#include "dldi_patcher.h"

#define FIX_ALL	0x01
#define FIX_GLUE	0x02
#define FIX_GOT	0x04
#define FIX_BSS	0x08

enum DldiOffsets {
	DO_magicString = 0x00,			// "\xED\xA5\x8D\xBF Chishm"
	DO_magicToken = 0x00,			// 0xBF8DA5ED
	DO_magicShortString = 0x04,		// " Chishm"
	DO_version = 0x0C,
	DO_driverSize = 0x0D,
	DO_fixSections = 0x0E,
	DO_allocatedSpace = 0x0F,

	DO_friendlyName = 0x10,

	DO_text_start = 0x40,			// Data start
	DO_data_end = 0x44,				// Data end
	DO_glue_start = 0x48,			// Interworking glue start	-- Needs address fixing
	DO_glue_end = 0x4C,				// Interworking glue end
	DO_got_start = 0x50,			// GOT start					-- Needs address fixing
	DO_got_end = 0x54,				// GOT end
	DO_bss_start = 0x58,			// bss start					-- Needs setting to zero
	DO_bss_end = 0x5C,				// bss end

	// IO_INTERFACE data
	DO_ioType = 0x60,
	DO_features = 0x64,
	DO_startup = 0x68,	
	DO_isInserted = 0x6C,	
	DO_readSectors = 0x70,	
	DO_writeSectors = 0x74,
	DO_clearStatus = 0x78,
	DO_shutdown = 0x7C,
	DO_code = 0x80
};

static addr_t readAddr (data_t *mem, addr_t offset) {
	return ((addr_t*)mem)[offset/sizeof(addr_t)];
}

static void writeAddr (data_t *mem, addr_t offset, addr_t value) {
	((addr_t*)mem)[offset/sizeof(addr_t)] = value;
}


static addr_t quickFind (const data_t* data, const data_t* search, size_t dataLen, size_t searchLen) {
	const int* dataChunk = (const int*) data;
	int searchChunk = ((const int*)search)[0];
	addr_t i;
	addr_t dataChunkEnd = (addr_t)(dataLen / sizeof(int));

	for ( i = 0; i < dataChunkEnd; i++) {
		if (dataChunk[i] == searchChunk) {
			if ((i*sizeof(int) + searchLen) > dataLen) {
				return -1;
			}
			if (memcmp (&data[i*sizeof(int)], search, searchLen) == 0) {
				return i*sizeof(int);
			}
		}
	}

	return -1;
}

// Strings are stored with bit 0x20 flipped (case inverted) to prevent accidental DLDI patching of them
#define DLDI_MAGIC_LEN 12
#define DLDI_MAGIC_MANGLE_VALUE 0x20
static const data_t dldiMagicStringMangled[DLDI_MAGIC_LEN] = "\xCD\x85\xAD\x9F\0cHISHM";	// Normal DLDI file

// Demangle the magic string by XORing every byte with 0x20, except the NULL terminator
static void demangleMagicString(data_t *dest, const data_t *src) {
	int i;

	memcpy(dest, src, DLDI_MAGIC_LEN);
	for (i = 0; i < DLDI_MAGIC_LEN - 1; ++i) {
		dest[i] ^= DLDI_MAGIC_MANGLE_VALUE;
	}
}

#define DEVICE_TYPE_DLDI 0x49444C44

extern data_t _dldi_start[];

bool dldiPatchBinary (data_t *binData, u32 binSize) {

	addr_t memOffset;			// Offset of DLDI after the file is loaded into memory
	addr_t patchOffset;			// Position of patch destination in the file
	addr_t relocationOffset;	// Value added to all offsets within the patch to fix it properly
	addr_t ddmemOffset;			// Original offset used in the DLDI file
	addr_t ddmemStart;			// Start of range that offsets can be in the DLDI file
	addr_t ddmemEnd;			// End of range that offsets can be in the DLDI file
	addr_t ddmemSize;			// Size of range that offsets can be in the DLDI file
	addr_t addrIter;

	data_t *pDH;
	data_t *pAH;

	data_t dldiMagicString[DLDI_MAGIC_LEN];
	size_t dldiFileSize = 0;

	// Find the DLDI reserved space in the file
	demangleMagicString(dldiMagicString, dldiMagicStringMangled);
	patchOffset = quickFind (binData, dldiMagicString, binSize, sizeof(dldiMagicString));

	if (patchOffset < 0) {
		// does not have a DLDI section
		return false;
	}

	pDH = _dldi_start;
	pAH = &(binData[patchOffset]);

	if (*((u32*)(pDH + DO_ioType)) == DEVICE_TYPE_DLDI) {
		// No DLDI patch
		return false;
	}

	if (pDH[DO_driverSize] > pAH[DO_allocatedSpace]) {
		// Not enough space for patch
		return false;
	}
	
	dldiFileSize = 1 << pDH[DO_driverSize];

	memOffset = readAddr (pAH, DO_text_start);
	if (memOffset == 0) {
			memOffset = readAddr (pAH, DO_startup) - DO_code;
	}
	ddmemOffset = readAddr (pDH, DO_text_start);
	relocationOffset = memOffset - ddmemOffset;

	ddmemStart = readAddr (pDH, DO_text_start);
	ddmemSize = (1 << pDH[DO_driverSize]);
	ddmemEnd = ddmemStart + ddmemSize;

	// Remember how much space is actually reserved
	pDH[DO_allocatedSpace] = pAH[DO_allocatedSpace];
	// Copy the DLDI patch into the application
	memcpy (pAH, pDH, dldiFileSize);

	// Fix the section pointers in the header
	writeAddr (pAH, DO_text_start, readAddr (pAH, DO_text_start) + relocationOffset);
	writeAddr (pAH, DO_data_end, readAddr (pAH, DO_data_end) + relocationOffset);
	writeAddr (pAH, DO_glue_start, readAddr (pAH, DO_glue_start) + relocationOffset);
	writeAddr (pAH, DO_glue_end, readAddr (pAH, DO_glue_end) + relocationOffset);
	writeAddr (pAH, DO_got_start, readAddr (pAH, DO_got_start) + relocationOffset);
	writeAddr (pAH, DO_got_end, readAddr (pAH, DO_got_end) + relocationOffset);
	writeAddr (pAH, DO_bss_start, readAddr (pAH, DO_bss_start) + relocationOffset);
	writeAddr (pAH, DO_bss_end, readAddr (pAH, DO_bss_end) + relocationOffset);
	// Fix the function pointers in the header
	writeAddr (pAH, DO_startup, readAddr (pAH, DO_startup) + relocationOffset);
	writeAddr (pAH, DO_isInserted, readAddr (pAH, DO_isInserted) + relocationOffset);
	writeAddr (pAH, DO_readSectors, readAddr (pAH, DO_readSectors) + relocationOffset);
	writeAddr (pAH, DO_writeSectors, readAddr (pAH, DO_writeSectors) + relocationOffset);
	writeAddr (pAH, DO_clearStatus, readAddr (pAH, DO_clearStatus) + relocationOffset);
	writeAddr (pAH, DO_shutdown, readAddr (pAH, DO_shutdown) + relocationOffset);

	// Put the correct DLDI magic string back into the DLDI header
	memcpy (pAH, dldiMagicString, sizeof (dldiMagicString));

	if (pDH[DO_fixSections] & FIX_ALL) { 
		// Search through and fix pointers within the data section of the file
		for (addrIter = (readAddr(pDH, DO_text_start) - ddmemStart); addrIter < (readAddr(pDH, DO_data_end) - ddmemStart); addrIter++) {
			if ((ddmemStart <= readAddr(pAH, addrIter)) && (readAddr(pAH, addrIter) < ddmemEnd)) {
				writeAddr (pAH, addrIter, readAddr(pAH, addrIter) + relocationOffset);
			}
		}
	}

	if (pDH[DO_fixSections] & FIX_GLUE) { 
		// Search through and fix pointers within the glue section of the file
		for (addrIter = (readAddr(pDH, DO_glue_start) - ddmemStart); addrIter < (readAddr(pDH, DO_glue_end) - ddmemStart); addrIter++) {
			if ((ddmemStart <= readAddr(pAH, addrIter)) && (readAddr(pAH, addrIter) < ddmemEnd)) {
				writeAddr (pAH, addrIter, readAddr(pAH, addrIter) + relocationOffset);
			}
		}
	}

	if (pDH[DO_fixSections] & FIX_GOT) { 
		// Search through and fix pointers within the Global Offset Table section of the file
		for (addrIter = (readAddr(pDH, DO_got_start) - ddmemStart); addrIter < (readAddr(pDH, DO_got_end) - ddmemStart); addrIter++) {
			if ((ddmemStart <= readAddr(pAH, addrIter)) && (readAddr(pAH, addrIter) < ddmemEnd)) {
				writeAddr (pAH, addrIter, readAddr(pAH, addrIter) + relocationOffset);
			}
		}
	}

	if (pDH[DO_fixSections] & FIX_BSS) { 
		// Initialise the BSS to 0
		memset (&pAH[readAddr(pDH, DO_bss_start) - ddmemStart] , 0, readAddr(pDH, DO_bss_end) - readAddr(pDH, DO_bss_start));
	}

	return true;
}
#endif