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6502bench/SourceGen/Tools/Omf/OmfReloc.cs
Andy McFadden 463a0cc561 Progress toward OMF file handling
Added generation of the relocation dictionary and constant body for
segments in Load files.

Also, don't reject files with v1 segments (whose length is specified
as a block count) just because the EOF isn't a multiple of 512 bytes.
Some executables don't pad out the last block.

Various tweaks to output formatting.
2020-06-28 21:10:53 -07:00

267 lines
10 KiB
C#

/*
* Copyright 2020 faddenSoft
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
using System;
using System.Collections.Generic;
using System.Diagnostics;
using CommonUtil;
namespace SourceGen.Tools.Omf {
/// <summary>
/// Apple IIgs OMF relocation entry. These are generated from OMF relocation records.
/// Note that SUPER records may generate multiple instances of these.
/// </summary>
public class OmfReloc {
/// <summary>
/// Number of bytes to be relocated.
/// </summary>
public int Width { get; private set; }
/// <summary>
/// Number of bits to shift the result before storing. Positive values shift left,
/// negative values shift right (unsigned).
/// </summary>
public int Shift { get; private set; }
/// <summary>
/// Offset within segment of bytes to rewrite.
/// </summary>
public int Offset { get; private set; }
/// <summary>
/// Relative offset of the thing being referenced. The segment's address in memory
/// is added to this to yield the final value.
/// </summary>
public int RelOffset { get; private set; }
/// <summary>
/// File number of target segment. Normally 1. Will be -1 for intra-segment relocs.
/// </summary>
public int FileNum { get; private set; }
/// <summary>
/// Segment number of target segment. Will be -1 for intra-segment relocs.
/// </summary>
public int SegNum { get; private set; }
/// <summary>
/// Set to the SUPER type, or -1 if this record was not from a SUPER.
/// </summary>
public int SuperType { get; private set; }
/// <summary>
/// Constructor for RELOC/cRELOC.
/// </summary>
/// <param name="width">Width in bytes of relocation.</param>
/// <param name="shift">Bit-shift amount.</param>
/// <param name="offset">Offset within segment of relocation.</param>
/// <param name="relOffset">Relative offset of relocation reference.</param>
/// <param name="fromSuper">True if generated from SUPER.</param>
private OmfReloc(int width, int shift, int offset, int relOffset, int superType) {
FileNum = SegNum = -1;
Width = width;
Shift = shift;
Offset = offset;
RelOffset = relOffset;
SuperType = superType;
}
/// <summary>
/// Constructor for INTERSEG/cINTERSEG.
/// </summary>
/// <param name="width">Width in bytes of relocation.</param>
/// <param name="shift">Bit-shift amount.</param>
/// <param name="offset">Offset within segment of relocation.</param>
/// <param name="relOffset">Relative offset of relocation reference.</param>
/// <param name="fileNum">File number.</param>
/// <param name="segNum">Segment number.</param>
/// <param name="fromSuper">True if generated from SUPER.</param>
private OmfReloc(int width, int shift, int offset, int relOffset, int fileNum,
int segNum, int superType) {
Width = width;
Shift = shift;
Offset = offset;
RelOffset = relOffset;
FileNum = fileNum;
SegNum = segNum;
SuperType = superType;
}
/// <summary>
/// Adds one or more OmfReloc instances to the list to represent the provided record.
/// </summary>
/// <param name="omfSeg">Segment that contains the record.</param>
/// <param name="omfRec">Record to add.</param>
/// <param name="data">File data.</param>
/// <param name="relocs">List of relocations. New entries will be appended.</param>
/// <returns>True on success.</returns>
public static bool GenerateRelocs(OmfSegment omfSeg, OmfRecord omfRec, byte[] data,
List<OmfReloc> relocs) {
try {
return DoGenerateRelocs(omfSeg, omfRec, data, relocs);
} catch (IndexOutOfRangeException ioore) {
Debug.WriteLine("Caught IOORE during reloc gen (" + omfRec.Op + "): " +
ioore.Message);
return false;
}
}
/// <summary>
/// Adds one or more OmfReloc instances to the list to represent the provided record.
/// </summary>
private static bool DoGenerateRelocs(OmfSegment omfSeg, OmfRecord omfRec, byte[] data,
List<OmfReloc> relocs) {
int offset = omfRec.FileOffset;
Debug.Assert(data[offset] == (int)omfRec.Op);
switch (omfRec.Op) {
case OmfRecord.Opcode.RELOC: {
byte width = data[offset + 1];
sbyte shift = (sbyte)data[offset + 2];
int off = RawData.GetWord(data, offset + 3, 4, false);
int relOff = RawData.GetWord(data, offset + 7, 4, false);
relocs.Add(new OmfReloc(width, shift, off, relOff, -1));
}
break;
case OmfRecord.Opcode.cRELOC: {
byte width = data[offset + 1];
sbyte shift = (sbyte)data[offset + 2];
int off = RawData.GetWord(data, offset + 3, 2, false);
int relOff = RawData.GetWord(data, offset + 5, 2, false);
relocs.Add(new OmfReloc(width, shift, off, relOff, -1));
}
break;
case OmfRecord.Opcode.INTERSEG: {
byte width = data[offset + 1];
sbyte shift = (sbyte)data[offset + 2];
int off = RawData.GetWord(data, offset + 3, 4, false);
int fileNum = RawData.GetWord(data, offset + 7, 2, false);
int segNum = RawData.GetWord(data, offset + 9, 2, false);
int relOff = RawData.GetWord(data, offset + 11, 4, false);
relocs.Add(new OmfReloc(width, shift, off, relOff, fileNum, segNum, -1));
}
break;
case OmfRecord.Opcode.cINTERSEG: {
byte width = data[offset + 1];
sbyte shift = (sbyte)data[offset + 2];
int off = RawData.GetWord(data, offset + 3, 2, false);
int fileNum = 1;
int segNum = data[offset + 5];
int relOff = RawData.GetWord(data, offset + 6, 2, false);
relocs.Add(new OmfReloc(width, shift, off, relOff, fileNum, segNum, -1));
}
break;
case OmfRecord.Opcode.SUPER:
if (!GenerateRelocForSuper(omfSeg, omfRec, data, relocs)) {
return false;
}
break;
default:
Debug.Assert(false);
return false;
}
return true;
}
/// <summary>
/// Generates a series of relocation items for a SUPER record.
/// </summary>
private static bool GenerateRelocForSuper(OmfSegment omfSeg, OmfRecord omfRec, byte[] data,
List<OmfReloc> relocs) {
int offset = omfRec.FileOffset;
int remaining = RawData.GetWord(data, offset + 1, 4, false);
int type = data[offset + 5];
offset += 6; // we've consumed 6 bytes
remaining--; // ...but only 1 counts against the SUPER length
int width, shift, fileNum, segNum;
bool needSegNum = false;
if (type == 0) {
// SUPER RELOC2
width = 2;
shift = 0;
fileNum = segNum = -1;
} else if (type == 1) {
// SUPER RELOC3
width = 3;
shift = 0;
fileNum = segNum = -1;
} else if (type >= 2 && type <= 13) {
// SUPER INTERSEG1 - SUPER INTERSEG12
width = 3;
shift = 0;
fileNum = type - 1;
segNum = -100;
needSegNum = true;
} else if (type >= 14 && type <= 25) {
// SUPER INTERSEG13 - SUPER INTERSEG24
width = 2;
shift = 0;
fileNum = 1;
segNum = type - 13;
} else if (type >= 26 && type <= 37) {
// SUPER INTERSEG25 - SUPER INTERSEG36
width = 2;
shift = -16; // right shift
fileNum = 1;
segNum = type - 25;
} else {
return false;
}
int page = 0;
while (remaining > 0) {
int patchCount = data[offset++];
remaining--;
if ((patchCount & 0x80) != 0) {
// high bit set, this is a skip-count
page += (patchCount & 0x7f);
continue;
}
patchCount++; // zero means one patch
while (patchCount-- != 0) {
int patchOff = data[offset++];
remaining--;
int relocOff = page * 256 + patchOff;
byte[] constData = omfSeg.GetConstData();
int relocRelOff = RawData.GetWord(constData, relocOff, 2, false);
if (needSegNum) {
segNum = constData[relocOff + 2];
}
relocs.Add(new OmfReloc(width, shift, relocOff, relocRelOff,
fileNum, segNum, type));
}
page++;
}
if (remaining < 0) {
Debug.WriteLine("Ran off end of SUPER record");
Debug.Assert(false);
return false;
}
return true;
}
}
}