/*
 * \brief  Fiasco(x86)-specific helper functions for GDB server
 * \author Christian Prochaska
 * \date   2011-05-06
 */

/*
 * Copyright (C) 2011-2012 Genode Labs GmbH
 *
 * This file is part of the Genode OS framework, which is distributed
 * under the terms of the GNU General Public License version 2.
 */

extern "C" {
#define private _private
#include "genode-low.h"
#define _private private
}

#include <base/printf.h>
#include "i386.h"
#include "cpu_session_component.h"
#include "gdbserver_platform_helper.h"
#include "gdb_stub_thread.h"

using namespace Genode;

extern "C" int genode_fetch_register(int regno, unsigned long *reg_content)
{
	Thread_state thread_state;

	try { thread_state = get_current_thread_state(); }
	catch (...) { return 0; }

	switch((enum reg_index)regno)
	{
		/* TODO: implement the backend function that tells gdbserver that these registers cannot be fetched */
		case EAX: PDBG("cannot determine contents of register EAX"); return -1;
		case ECX: PDBG("cannot determine contents of register ECX"); return -1;
		case EDX: PDBG("cannot determine contents of register EDX"); return -1;
		case EBX: PDBG("cannot determine contents of register EBX"); return -1;
		case UESP: *reg_content = thread_state.sp; PDBG("ESP = %8lx", *reg_content); return 0;
		case EBP:

			/*
			 * When in a syscall, the user EBP has been pushed onto the stack at address ESP+0
			 *
			 * looking for syscall pattern:
			 * EIP-2:  cd 30  int $30
			 */
			if ((genode_read_memory_byte((void*)(thread_state.ip - 1)) == 0x30) &&
				(genode_read_memory_byte((void*)(thread_state.ip - 2)) == 0xcd)) {
				*reg_content = genode_read_memory_byte((void*)(thread_state.sp + 0)) +
				               (genode_read_memory_byte((void*)(thread_state.sp + 1)) << 8) +
				               (genode_read_memory_byte((void*)(thread_state.sp + 2)) << 16) +
				               (genode_read_memory_byte((void*)(thread_state.sp + 3)) << 24);
				PDBG("ESP = %8lx", *reg_content);
				return 0;
			} else {
				PDBG("cannot determine contents of register EBP"); return -1;
			}
		case ESI: PDBG("cannot determine contents of register ESI"); return -1;
		case EDI: PDBG("cannot determine contents of register EDI"); return -1;
		case EIP: *reg_content = thread_state.ip; PDBG("EIP = %8lx", *reg_content); return 0;
		case EFL: PDBG("cannot determine contents of register EFLAGS"); return -1;
		case CS: PDBG("cannot determine contents of register CS"); return -1;
		case SS: PDBG("cannot determine contents of register SS"); return -1;
		case DS: PDBG("cannot determine contents of register DS"); return -1;
		case ES: PDBG("cannot determine contents of register ES"); return -1;
		case FS: PDBG("cannot determine contents of register FS"); return -1;
		case GS: PDBG("cannot determine contents of register GS"); return -1;
	}

	return -1;
}