view lwasm/os9.c @ 556:928c033c0cd0

Allow MOD directive to accept only the standard base header parameters There are cases where only the standard OS9 module header fields are to be provided. This could be, for instance, in the case of a nonstandard user type module. So allow the execution offset and data size fields to be omitted entirely and handle the module length correctly as well.
author William Astle <lost@l-w.ca>
date Fri, 08 Sep 2023 00:32:40 -0600
parents 8764142b3192
children dba08c7dff96
line wrap: on
line source

/*
os9.c
Copyright © 2009 William Astle

This file is part of LWASM.

LWASM 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 3 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, see <http://www.gnu.org/licenses/>.


This file implements the various pseudo operations related to OS9 target
*/
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <lw_expr.h>

#include "lwasm.h"
#include "instab.h"


// OS9 syscall
PARSEFUNC(pseudo_parse_os9)
{
	lw_expr_t e;
	
	if (as -> output_format != OUTPUT_OS9 && as -> output_format != OUTPUT_OBJ)
	{
		lwasm_register_error2(as, l, E_DIRECTIVE_OS9_ONLY, "%s", "os9");
		return;
	}
	
	// fetch immediate value
	e = lwasm_parse_expr(as, p);
	if (!e)
	{
		lwasm_register_error(as, l, E_OPERAND_BAD);
		return;
	}
	lwasm_save_expr(l, 0, e);
	l -> len = 3;
}

EMITFUNC(pseudo_emit_os9)
{
	lw_expr_t e;
	
	e = lwasm_fetch_expr(l, 0);

	lwasm_emitop(l, 0x103f);
	lwasm_emitexpr(l, e, 1);
}

PARSEFUNC(pseudo_parse_mod)
{
	lw_expr_t e;
	int i;
	
	if (as -> output_format != OUTPUT_OS9)
	{
		lwasm_register_error2(as, l, E_DIRECTIVE_OS9_ONLY, "%s", "mod");
		skip_operand(p);
		return;
	}
	
	if (as -> inmod)
	{
		lwasm_register_error(as, l, E_MODULE_IN);
		skip_operand(p);
		return;
	}

	// parse 6 (or 4) expressions...
	for (i = 0; i < 5; i++)
	{
		e = lwasm_parse_expr(as, p);
		if (!e)
		{
			lwasm_register_error(as, l, E_OPERAND_BAD);
			return;
		}

		lwasm_save_expr(l, i, e);

		if (**p != ',')
		{
			if (i == 3)
			{
				// we don't have the extra items; flag it and don't bother
				// with them later; goto is to short circuit the rest of
				// the expression parsing
				l -> lint = 4;
				goto doneexpr;
			}
			lwasm_register_error(as, l, E_OPERAND_BAD);
			return;
		}
		(*p)++;
	}
	e = lwasm_parse_expr(as, p);
	if (!e)
	{
		lwasm_register_error(as, l, E_OPERAND_BAD);
		return;
	}
	lwasm_save_expr(l, 5, e);
	l -> lint = 6;

doneexpr:
	l -> inmod = 1;
	
	// we have an implicit ORG 0 with "mod"
	lw_expr_destroy(l -> addr);
	l -> addr = lw_expr_build(lw_expr_type_int, 0);

	// likewise for data pointer
	lw_expr_destroy(l -> daddr);
	l -> daddr = lw_expr_build(lw_expr_type_int, 0);

	// init crc
	as -> inmod = 1;
	
	l -> len = (i == 6) ? 13 : 9;
}

EMITFUNC(pseudo_emit_mod)
{
	lw_expr_t e1, e2, e3, e4;
	int csum;
	
	as -> crc[0] = 0xff;
	as -> crc[1] = 0xff;
	as -> crc[2] = 0xff;

	// sync bytes
	lwasm_emit(l, 0x87);
	lwasm_emit(l, 0xcd);
	
	// mod length
	lwasm_emitexpr(l, e1 = lwasm_fetch_expr(l, 0), 2);
	
	// name offset
	lwasm_emitexpr(l, e2 = lwasm_fetch_expr(l, 1), 2);
	
	// type
	lwasm_emitexpr(l, e3 = lwasm_fetch_expr(l, 2), 1);
	
	// flags/rev
	lwasm_emitexpr(l, e4 = lwasm_fetch_expr(l, 3), 1);
	
	// header check
	csum = ~(0x87 ^ 0xCD ^(lw_expr_intval(e1) >> 8) ^ (lw_expr_intval(e1) & 0xff)
		^ (lw_expr_intval(e2) >> 8) ^ (lw_expr_intval(e2) & 0xff)
		^ lw_expr_intval(e3) ^ lw_expr_intval(e4));
	lwasm_emit(l, csum);

	if (l -> lint == 6)
	{
		// module type specific output, if provided
		// note that these are handled the same for all so
		// there need not be any special casing

		// exec offset or fmgr name offset
		lwasm_emitexpr(l, lwasm_fetch_expr(l, 4), 2);

		// data size or drvr name offset
		lwasm_emitexpr(l, lwasm_fetch_expr(l, 5), 2);
	}
}

PARSEFUNC(pseudo_parse_emod)
{
	skip_operand(p);
	if (as -> output_format != OUTPUT_OS9)
	{
		lwasm_register_error2(as, l, E_DIRECTIVE_OS9_ONLY, "%s", "emod");
		return;
	}
	
	if (!(as -> inmod))
	{
		lwasm_register_error(as, l, E_MODULE_NOTIN);
		return;
	}
	
	as -> inmod = 0;
	l -> len = 3;
}

EMITFUNC(pseudo_emit_emod)
{
	unsigned char tcrc[3];
	
	// don't mess with CRC!
	tcrc[0] = as -> crc[0] ^ 0xff;
	tcrc[1] = as -> crc[1] ^ 0xff;
	tcrc[2] = as -> crc[2] ^ 0xff;
	lwasm_emit(l, tcrc[0]);
	lwasm_emit(l, tcrc[1]);
	lwasm_emit(l, tcrc[2]);
}