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amiga-bootcamp/03_loader_and_exec_format/README.md
Ilia Sharin 21751c0025 docs(amiga): complete AmigaOS 3.1/3.2 developer reference — 172 files across 17 sections 
Comprehensive technical documentation covering:
- Hardware: OCS/ECS/AGA custom chip registers, Copper & Blitter deep dives
- Boot sequence: cold boot through startup-sequence
- Binary format: HUNK executable spec, relocation, debug info
- Linking & ABI: .fd files, LVO tables, register calling conventions
- Exec kernel: tasks, interrupts, memory, signals, semaphores
- AmigaDOS: file I/O, FFS/OFS layout, CLI/Shell scripting
- Graphics: planar bitmaps, Copper programming, HAM/EHB modes
- Intuition: screens, windows, IDCMP, BOOPSI
- Devices: trackdisk, SCSI, serial, timer, audio, keyboard
- Libraries: utility, expansion, IFFParse, locale, ARexx
- Networking: bsdsocket API, SANA-II, TCP/IP stack comparison
- Toolchain: GCC, vasm/vlink, SAS/C, NDK, debugging
- Reverse engineering: IDA/Ghidra setup, compiler fingerprints, case studies
- CPU & MMU: 68040/060 emulation libs, PMMU, cache management
- Driver development: SANA-II, Picasso96/RTG, AHI audio

All files include breadcrumb navigation. No local paths or proprietary content.
2026-04-23 12:17:35 -04:00

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Executable Loader & HUNK Format

Overview

This section covers the complete lifecycle of an AmigaOS executable:

  1. HUNK file format — the binary container for all AmigaOS executables, libraries, and object files
  2. Loader pipeline — how dos.library loads and relocates an executable into memory
  3. Object files — how compilers produce relocatable object files for the linker
  4. Overlays — how programs larger than available memory use the overlay system

Contents

File Topic
hunk_format.md Complete HUNK binary specification
hunk_ext_deep_dive.md HUNK_EXT: exports, imports, commons
hunk_relocation.md HUNK_RELOC32/16/8 mechanics
hunk_debug_info.md HUNK_SYMBOL, HUNK_DEBUG (stabs)
exe_load_pipeline.md LoadSeg → Process creation
object_file_format.md Compiler object files (HUNK_UNIT)
overlay_system.md HUNK_OVERLAY memory segmentation

Why HUNK?

HUNK is the native AmigaOS executable format, used from AmigaOS 1.0 through 3.x. It predates ELF/COFF and has these key properties:

  • Segmented: separate code, data, and BSS hunks with independent memory allocation
  • Relocatable: all absolute references are patched at load time (no ASLR; base address changes each run)
  • Typed memory: each hunk can request CHIP or FAST memory independently
  • Symbol-complete: optional HUNK_SYMBOL and HUNK_DEBUG hunks carry debugging information

Key Concepts

Term Meaning
Hunk One contiguous block in the binary (code, data, BSS, etc.)
Segment A loaded hunk at runtime — a BPTR-linked list
Segment list Chain of loaded hunks returned by LoadSeg()
BPTR Amiga byte pointer — 32-bit value right-shifted by 2 (ptr >> 2)
Relocation Patching absolute addresses based on actual load address
LVO Library Vector Offset — negative offset from library base

References