/****************************************************************
 *								*
 *	Copyright 2001, 2010 Fidelity Information Services, Inc	*
 *								*
 *	This source code contains the intellectual property	*
 *	of its copyright holder(s), and is made available	*
 *	under a license.  If you do not know the terms of	*
 *	the license, please stop and do not read further.	*
 *								*
 ****************************************************************/

#include "mdef.h"

#include "gtm_string.h"

#include "i386.h"
#include "urx.h"
#include "rtnhdr.h"
#include "op.h"
#include "auto_zlink.h"

#define PEA_SZ		5
#define XFER_BYTE_SZ	3
#define XFER_LONG_SZ	6
#define INST_SZ		1

rhdtyp *auto_zlink (unsigned char *pc, int4 **line)
{
	char		*adj_pc;	/* address of PEA rtnref offset */
	mstr		rname;
	mident_fixed	rname_local;
	urx_rtnref	*rtnurx;
	mval		rtn;
	rhdtyp		*rhead;
	error_def	(ERR_ROUTINEUNKNOWN);
	error_def	(ERR_LABELUNKNOWN);
	union
	{
		ModR_M		modrm;
		unsigned char	byte;
	} modrm_byte_byte, modrm_byte_long;

/* ASSUMPTION -- The instruction previous to the current mpc is a transfer table jump.
 *		This is either a byte or a int4 displacement off of ebx, instruction
 *		size either 3 or 6 (prefix byte, ModR/M byte, 8- or 32-bit offset).
 */

	modrm_byte_byte.modrm.reg_opcode = I386_INS_CALL_Ev;
	modrm_byte_byte.modrm.mod = I386_MOD32_BASE_DISP_8;
	modrm_byte_byte.modrm.r_m = I386_REG_EBX;

	modrm_byte_long.modrm.reg_opcode = I386_INS_CALL_Ev;
	modrm_byte_long.modrm.mod = I386_MOD32_BASE_DISP_32;
	modrm_byte_long.modrm.r_m = I386_REG_EBX;

	if (*(pc - XFER_BYTE_SZ) == I386_INS_Grp5_Prefix  &&  *(pc - XFER_BYTE_SZ + 1) == modrm_byte_byte.byte)
	{
		assert (*(pc - XFER_BYTE_SZ - PEA_SZ) == I386_INS_PUSH_Iv);
		adj_pc = (char *)pc - XFER_BYTE_SZ - PEA_SZ;
	}
	else if (*(pc - XFER_LONG_SZ) == I386_INS_Grp5_Prefix  &&  *(pc - XFER_LONG_SZ + 1) == modrm_byte_long.byte)
	{
		assert (*(pc - XFER_LONG_SZ - PEA_SZ) == I386_INS_PUSH_Iv);
		adj_pc = (char *)pc - XFER_LONG_SZ - PEA_SZ;
	}
	else
		GTMASSERT;

	if (azl_geturxrtn (adj_pc + INST_SZ, &rname, &rtnurx))
	{
		assert (0 <= rname.len && rname.len <= MAX_MIDENT_LEN);
		assert (rname.addr);
		/* Copy rname into local storage because azl_geturxrtn sets
			rname.addr to an address that is freed during op_zlink
			and before the call to find_rtn_hdr.
		*/
		memcpy(rname_local.c, rname.addr, rname.len);
		rname.addr = rname_local.c;
		assert (rtnurx);
		assert (*(adj_pc - PEA_SZ) == I386_INS_PUSH_Iv);
		assert (azl_geturxlab (adj_pc - PEA_SZ + INST_SZ, rtnurx));
		assert (!find_rtn_hdr (&rname));
		rtn.mvtype = MV_STR;
		rtn.str.len = rname.len;
		rtn.str.addr = rname.addr;
		op_zlink (&rtn, 0);
		if (0 != (rhead = find_rtn_hdr (&rname)))
		{
			*line = *(int4 **) (adj_pc - PEA_SZ + INST_SZ);
			if (!(*line))
				rts_error(VARLSTCNT(1) ERR_LABELUNKNOWN);
			return rhead;
		}
	}
	rts_error(VARLSTCNT(1) ERR_ROUTINEUNKNOWN);
	return NULL;
}