Module disk

Post-EBS Disk Operations

Allocation-free disk I/O for post-ExitBootServices environment. All operations use fixed-size stack buffers and the VirtIO-blk BlockIo adapter.

Architecture

┌────────────────────────────────────────────────────────────┐
│                  IsoWriter (streaming)                     │
│            Coordinates GPT + FAT32 + data writes           │
└──────────────────────────┬─────────────────────────────────┘
                           │
         ┌─────────────────┼─────────────────┐
         ▼                 ▼                 ▼
┌──────────────┐  ┌──────────────┐  ┌──────────────┐
│  GptOps      │  │  Fat32Fmt    │  │  Manifest    │
│  (partition) │  │  (format)    │  │  (tracking)  │
└──────────────┘  └──────────────┘  └──────────────┘
         │                 │                 │
         └─────────────────┼─────────────────┘
                           ▼
┌────────────────────────────────────────────────────────────┐
│               VirtioBlkBlockIo (driver adapter)            │
└────────────────────────────────────────────────────────────┘

Design Principles

1. No heap allocations - All buffers are stack-allocated or DMA regions
2. Streaming writes - Data written as it arrives from HTTP download
3. Chunk partitions - ISO split across FAT32 partitions (4GB limit each)
4. Manifest tracking - Binary manifest for bootloader to find chunks

Modules

• fat32 🔒
  FAT32 formatter for post-EBS.
• gpt 🔒
  GPT partition operations for post-EBS.
• manifest 🔒
  Manifest writer for post-EBS.
• types 🔒
  Shared types for post-EBS disk operations.
• writer 🔒
  Streaming ISO writer for post-EBS.

Structs

• ChunkPartition
  Chunk partition for ISO storage
• ChunkSet
  Collection of chunk partitions for an ISO
• Fat32Formatter
  FAT32 filesystem formatter
• Fat32Info
  Information about formatted FAT32 filesystem
• GptOps
  GPT operations helper
• IsoManifestInfo
  Parsed manifest information
• IsoWriter
  Streaming ISO writer
• ManifestReader
  Manifest reader for loading existing manifests
• ManifestWriter
  Binary manifest for ISO chunks
• PartitionInfo
  Information about a partition

Enums

• DiskError
  Disk operation error types

Constants

• MAX_CHUNK_PARTITIONS
  Maximum number of chunk partitions for an ISO
• SECTOR_SIZE
  Sector size in bytes (standard 512-byte sectors)

Type Aliases

• DiskResult
  Result type for disk operations