/** \file
 * Reboot into the hacked firmware.
 *
 * This program is very simple: attempt to reboot into the normal
 * firmware RAM image after startup.
 */
/*
 * Copyright (C) 2009 Trammell Hudson <hudson+ml@osresearch.net>
 * 
 * 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.
 */

#include "arm-mcr.h"

#undef RESTARTSTART
#define RESTARTSTART_550 0x8B000
#define RESTARTSTART_60  0x5f000
#define RESTARTSTART_600 0x82000
#define RESTARTSTART_50  0x4b000
#define RESTARTSTART_500 0x4d000

#define SIG_LEN 0x10000

#define SIG_60D_110  0xac958a1e // from FF010000
#define SIG_550D_109 0x851320e6 // from FF010000
#define SIG_600D_101 0x290106d8 // from FF010000
#define SIG_500D_110 0x4c0e5a7e // from FF010000
#define SIG_50D_108  0xb2311152 // from FF010000
#define SIG_50D_107  0x20e3a085 // from FF810000
#define SIG_5D2_204  0x41d8373d // from FF810000
#define SIG_500D_111 0x44f49aef // from FF010000

asm(
".text\n"
".globl _start\n"
"_start:\n"
"	b 1f\n"
".ascii \"gaonisoy\"\n"		// 0x124, 128
"1:\n"
"MRS     R0, CPSR\n"
"BIC     R0, R0, #0x3F\n"	// Clear I,F,T
"ORR     R0, R0, #0xD3\n"	// Set I,T, M=10011 == supervisor
"MSR     CPSR, R0\n"
"	ldr sp, =0x1900\n"	// 0x130
"	mov fp, #0\n"
"	b cstart\n"
);

static void busy_wait(int n)
{
	int i,j;
	static volatile int k = 0;
	for (i = 0; i < n; i++)
		for (j = 0; j < 100000; j++)
			k++;
}

static void blink(int n)
{
	while (1)
	{
		*(int*)0xC0220134 |= 2;  // SD card LED on
		*(int*)0xC02200BC |= 2;  // CF card LED on
		busy_wait(n);
		*(int*)0xC0220134 &= ~2;  // SD card LED off
		*(int*)0xC02200BC &= ~2;  // CF card LED off
		busy_wait(n);
	}
}

static void fail()
{
	blink(50);
}

static int compute_signature(int* start, int num)
{
	int c = 0;
	int* p;
	for (p = start; p < start + num; p++)
	{
		c += *p;
	}
	//~ return SIG_60D_110;
	return c;
}

/** Include the relocatable shim code */
extern uint8_t blob_start_550;
extern uint8_t blob_end_550;
extern uint8_t blob_start_60;
extern uint8_t blob_end_60;
extern uint8_t blob_start_600;
extern uint8_t blob_end_600;
extern uint8_t blob_start_50;
extern uint8_t blob_end_50;
extern uint8_t blob_start_500;
extern uint8_t blob_end_500;
void* blob_start = 0;
void* blob_end = 0;
void* RESTARTSTART = 0;
void* ROMSTART = (void *)0xFF010000;

static int guess_firmware_version()
{
	int s = compute_signature((int*)0xFF010000, SIG_LEN);
	switch(s)
	{
		case SIG_550D_109:
			blob_start = &blob_start_550;
			blob_end = &blob_end_550;
			RESTARTSTART = (void*)RESTARTSTART_550;
			return 1;
		case SIG_60D_110:
			blob_start = &blob_start_60;
			blob_end = &blob_end_60;
			RESTARTSTART = (void*)RESTARTSTART_60;
			return 1;
		case SIG_600D_101:
			blob_start = &blob_start_600;
			blob_end = &blob_end_600;
			RESTARTSTART = (void*)RESTARTSTART_600;
			return 1;
		case SIG_50D_108:
			blob_start = &blob_start_50;
			blob_end = &blob_end_50;
			RESTARTSTART = (void*)RESTARTSTART_50;
			ROMSTART = (void *)0xFF810000;
			return 1;
		case SIG_500D_111:
			blob_start = &blob_start_500;
			blob_end = &blob_end_500;
			RESTARTSTART = (void*)RESTARTSTART_500;
			return 1;
		default:
			fail();
	}
	return 0;
}

asm(
	".text\n"
	".align 12\n" // 2^12 == 4096 bytes

	".globl blob_start_550\n"
	"blob_start_550:\n"
	".incbin \"../550D.109/magiclantern.bin\"\n" // 
	".align 12\n"
	"blob_end_550:\n"
	".globl blob_end_550\n"

	".globl blob_start_60\n"
	"blob_start_60:\n"
	".incbin \"../60D.110/magiclantern.bin\"\n" // 
	".align 12\n"
	"blob_end_60:"
	".globl blob_end_60\n"

	".globl blob_start_600\n"
	"blob_start_600:\n"
	".incbin \"../600D.101/magiclantern.bin\"\n" // 
	".align 12\n"
	"blob_end_600:"
	".globl blob_end_600\n"

	".globl blob_start_50\n"
	"blob_start_50:\n"
	".incbin \"../50D.108/magiclantern.bin\"\n" // 
	".align 12\n"
	"blob_end_50:"
	".globl blob_end_50\n"

	".globl blob_start_500\n"
	"blob_start_500:\n"
	".incbin \"../500D.111/magiclantern.bin\"\n" // 
	".align 12\n"
	"blob_end_500:"
	".globl blob_end_500\n"
);


/** Determine the in-memory offset of the code.
 * If we are autobooting, there is no offset (code is loaded at
 * 0x800000).  If we are loaded via a firmware file then there
 * is a 0x120 byte header infront of our code.
 *
 * Note that mov r0, pc puts pc+8 into r0.
 */
static int
__attribute__((noinline))
find_offset( void )
{
	uintptr_t pc;
	asm __volatile__ (
		"mov %0, %%pc"
		: "=&r"(pc)
	);

	return pc - 8 - (uintptr_t) find_offset;
}

void
__attribute__((noreturn))
cstart( void )
{
	//~ fail();
	// Compute a checksum from ROM, compare it with known values,
	// identify camera and firmware version, 
	// and set RESTARTSTART, blob_start and blob_end.
	// If the firmware is not correct, it should not boot (and blink a LED).
	int x = guess_firmware_version();

	if (x != 1)
		while(1); // should be unreachable
	
	// Copy the copy-and-restart blob somewhere
	// there is a bug in that we are 0x120 bytes off from
	// where we should be, so we must offset the blob start.
	ssize_t offset = find_offset();

	blob_memcpy(
		(void*) RESTARTSTART,
		blob_start + offset,
		blob_end + offset
	);
	clean_d_cache();
	flush_caches();

	// Jump into the newly relocated code
	void __attribute__((noreturn))(*copy_and_restart)(int)
		= (void*) RESTARTSTART;

	void __attribute__((noreturn))(*firmware_start)(void)
		= (void*) ROMSTART;

	if( 1 )
		copy_and_restart(offset);
	else
		firmware_start();

	// Unreachable
	while(1)
		;
}