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Implement traversing and enumeration of AIX minidisk partitions. Fixes #7
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286
Aaru.Partitions/AixMinidisk.cs
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286
Aaru.Partitions/AixMinidisk.cs
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// /***************************************************************************
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// Aaru Data Preservation Suite
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// ----------------------------------------------------------------------------
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//
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// Filename : AixMinidisk.cs
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// Author(s) : Natalia Portillo <claunia@claunia.com>
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//
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// Component : Partitioning scheme plugins.
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//
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// --[ Description ] ----------------------------------------------------------
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//
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// Manages AIX minidisk partitions (VTOC).
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//
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// --[ License ] --------------------------------------------------------------
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//
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// This library is free software; you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as
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// published by the Free Software Foundation; either version 2.1 of the
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// License, or (at your option) any later version.
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//
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// This library is distributed in the hope that it will be useful, but
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// WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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// Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public
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// License along with this library; if not, see <http://www.gnu.org/licenses/>.
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//
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// ----------------------------------------------------------------------------
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// Copyright © 2011-2026 Natalia Portillo
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// ****************************************************************************/
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using System;
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using System.Collections.Generic;
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using System.Diagnostics.CodeAnalysis;
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using System.Runtime.InteropServices;
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using System.Text;
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using Aaru.CommonTypes;
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using Aaru.CommonTypes.Enums;
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using Aaru.CommonTypes.Interfaces;
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using Aaru.Logging;
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using Marshal = Aaru.Helpers.Marshal;
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namespace Aaru.Partitions;
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/// <inheritdoc />
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/// <summary>Implements decoding of the AIX minidisk (VTOC) partitioning scheme</summary>
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[SuppressMessage("ReSharper", "InconsistentNaming")]
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public sealed class AixMinidisk : IPartition
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{
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const string MODULE_NAME = "AIX minidisk plugin";
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/// <summary>AIX VTOC magic string "VTOC"</summary>
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const uint VTOC_MAGIC = 0x56544F43; // "VTOC" in ASCII
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/// <summary>Block size for AIX minidisks</summary>
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const int BLOCKSIZE = 512;
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/// <summary>Maximum number of minidisks in VTOC</summary>
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const int MAX_MINIDISKS = 32;
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/// <inheritdoc />
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public string Name => "AIX minidisk";
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/// <inheritdoc />
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public Guid Id => new("25ED1C9A-0FF0-49FC-9F43-34844B8309B8");
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/// <inheritdoc />
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public string Author => Authors.NATALIA_PORTILLO;
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/// <inheritdoc />
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public bool GetInformation(IMediaImage imagePlugin, out List<Partition> partitions, ulong sectorOffset)
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{
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partitions = [];
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// VTOC is typically at sector 1 (after boot0)
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// But we need to find the AIX partition first if coming from MBR
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ulong vtocSector = sectorOffset + 1;
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ErrorNumber errno = imagePlugin.ReadSector(vtocSector, false, out byte[] sector, out _);
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if(errno != ErrorNumber.NoError || sector.Length < BLOCKSIZE)
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{
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AaruLogging.Debug(MODULE_NAME, "Error reading VTOC sector: {0}", errno);
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return false;
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}
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// Check for VTOC magic
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var magic = (uint)(sector[0] << 24 | sector[1] << 16 | sector[2] << 8 | sector[3]);
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AaruLogging.Debug(MODULE_NAME, "VTOC magic = 0x{0:X8}, expected 0x{1:X8}", magic, VTOC_MAGIC);
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if(magic != VTOC_MAGIC)
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{
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AaruLogging.Debug(MODULE_NAME, "VTOC magic not found at sector {0}", vtocSector);
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return false;
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}
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Vtoc1 vtoc = Marshal.ByteArrayToStructureLittleEndian<Vtoc1>(sector);
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AaruLogging.Debug(MODULE_NAME,
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"vtoc.magic_string = \"{0}\"",
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Encoding.ASCII.GetString(vtoc.magic_string).TrimEnd('\0'));
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AaruLogging.Debug(MODULE_NAME, "vtoc.version = {0}", vtoc.version);
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AaruLogging.Debug(MODULE_NAME, "vtoc.seq_num = {0}", vtoc.seq_num);
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AaruLogging.Debug(MODULE_NAME, "vtoc.bootsize = {0}", vtoc.bootsize);
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AaruLogging.Debug(MODULE_NAME, "vtoc.numbadblks = {0}", vtoc.numbadblks);
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AaruLogging.Debug(MODULE_NAME, "vtoc.badblkoff = {0}", vtoc.badblkoff);
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// Read VTOC2 and VTOC3 for mount string table
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errno = imagePlugin.ReadSector(vtocSector + 1, false, out byte[] vtoc2Sector, out _);
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if(errno != ErrorNumber.NoError)
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{
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AaruLogging.Debug(MODULE_NAME, "Error reading VTOC2 sector: {0}", errno);
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return false;
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}
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errno = imagePlugin.ReadSector(vtocSector + 2, false, out byte[] vtoc3Sector, out _);
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if(errno != ErrorNumber.NoError)
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{
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AaruLogging.Debug(MODULE_NAME, "Error reading VTOC3 sector: {0}", errno);
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return false;
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}
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// Build the string table from VTOC2 and VTOC3
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// VTOC2: byte 0 is seq_num, bytes 1-511 are first part of string table
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// VTOC3: bytes 0-506 are second part, byte 507 is seq_num, bytes 508-511 are checksum
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var stringTable = new byte[511 + 507]; // V2_STRTABLEN + V3_STRTABLEN
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Array.Copy(vtoc2Sector, 1, stringTable, 0, 511);
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Array.Copy(vtoc3Sector, 0, stringTable, 511, 507);
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ulong counter = 0;
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for(var i = 0; i < MAX_MINIDISKS; i++)
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{
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Minidisk md = vtoc.mini[i];
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// Check for end marker
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if(md.type == MD_END)
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{
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AaruLogging.Debug(MODULE_NAME, "End of minidisk table at entry {0}", i);
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break;
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}
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AaruLogging.Debug(MODULE_NAME, "vtoc.mini[{0}].s_block = {1}", i, md.s_block);
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AaruLogging.Debug(MODULE_NAME, "vtoc.mini[{0}].num_blks = {1}", i, md.num_blks);
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AaruLogging.Debug(MODULE_NAME, "vtoc.mini[{0}].type = {1} ({2})", i, md.type, TypeToString(md.type));
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AaruLogging.Debug(MODULE_NAME, "vtoc.mini[{0}].mdisk_id = {1}", i, md.mdisk_id);
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AaruLogging.Debug(MODULE_NAME, "vtoc.mini[{0}].str_index = {1}", i, md.str_index);
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// Skip entries with no blocks
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if(md.num_blks == 0) continue;
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// Skip reserved and bad block entries
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if(md.type is MD_BAD_BLOCK or MD_UNALLOC) continue;
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// Get mount point string from string table
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var mountPoint = "";
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if(md.str_index > 0 && md.str_index < stringTable.Length)
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{
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int strEnd = Array.IndexOf<byte>(stringTable, 0, md.str_index);
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int strLen = strEnd >= 0 ? strEnd - md.str_index : stringTable.Length - md.str_index;
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mountPoint = Encoding.ASCII.GetString(stringTable, md.str_index, strLen);
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}
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var part = new Partition
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{
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Start = md.s_block * BLOCKSIZE / imagePlugin.Info.SectorSize,
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Offset = md.s_block * BLOCKSIZE,
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Length = md.num_blks * BLOCKSIZE / imagePlugin.Info.SectorSize,
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Size = md.num_blks * BLOCKSIZE,
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Type = TypeToString(md.type),
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Sequence = counter,
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Scheme = Name,
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Name = string.IsNullOrEmpty(mountPoint) ? $"hd{md.mdisk_id & 0x1F}" : mountPoint
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};
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AaruLogging.Debug(MODULE_NAME,
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"Partition {0}: start={1}, length={2}, type={3}, name={4}",
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counter,
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part.Start,
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part.Length,
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part.Type,
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part.Name);
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partitions.Add(part);
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counter++;
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}
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return partitions.Count > 0;
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}
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static string TypeToString(byte type) => type switch
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{
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MD_END => "End marker",
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MD_PAGE => "AIX paging space",
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MD_DUMP => "AIX dump space",
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MD_UNALLOC => "Unallocated",
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MD_AIX_BOOT => "AIX boot",
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MD_AIX_NOBOOT => "AIX filesystem",
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MD_BAD_BLOCK => "Bad block table",
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_ => $"Unknown (0x{type:X2})"
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};
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#region Constants
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/// <summary>End of VTOC table marker</summary>
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const byte MD_END = 0;
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/// <summary>Page space minidisk</summary>
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const byte MD_PAGE = 1;
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/// <summary>Dump space minidisk</summary>
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const byte MD_DUMP = 2;
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/// <summary>Free space for AIX</summary>
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const byte MD_UNALLOC = 3;
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/// <summary>AIX minidisk containing /unixtext</summary>
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const byte MD_AIX_BOOT = 8;
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/// <summary>Any other AIX minidisk</summary>
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const byte MD_AIX_NOBOOT = 9;
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/// <summary>Bad block table minidisk</summary>
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const byte MD_BAD_BLOCK = 0x0E;
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#endregion
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#region Nested type: Minidisk
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/// <summary>AIX minidisk entry structure</summary>
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[StructLayout(LayoutKind.Sequential, Pack = 1)]
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struct Minidisk
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{
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/// <summary>Starting block number</summary>
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public readonly uint s_block;
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/// <summary>Length of minidisk in blocks</summary>
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public readonly uint num_blks;
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/// <summary>Type of minidisk</summary>
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public readonly byte type;
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/// <summary>Minidisk ID number</summary>
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public readonly byte mdisk_id;
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/// <summary>Index into string table</summary>
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public readonly ushort str_index;
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}
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#endregion
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#region Nested type: Vtoc1
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/// <summary>AIX VTOC sector 1 structure</summary>
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[StructLayout(LayoutKind.Sequential, Pack = 1)]
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struct Vtoc1
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{
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/// <summary>"VTOC" magic string</summary>
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[MarshalAs(UnmanagedType.ByValArray, SizeConst = 4)]
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public readonly byte[] magic_string;
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/// <summary>Version number</summary>
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public readonly byte version;
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/// <summary>Sequence number (must match others)</summary>
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public readonly byte seq_num;
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/// <summary>Max length of boot 1 in disk blocks</summary>
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public readonly ushort bootsize;
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/// <summary>Number of bad blocks (ST506 only)</summary>
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public readonly ushort numbadblks;
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/// <summary>Offset within the bad block minidisk</summary>
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public readonly ushort badblkoff;
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/// <summary>Spare (to put mini[] on 8 byte boundary)</summary>
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public readonly int vt_spare;
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/// <summary>Minidisk entries</summary>
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[MarshalAs(UnmanagedType.ByValArray, SizeConst = MAX_MINIDISKS)]
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public readonly Minidisk[] mini;
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}
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#endregion
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}
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