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Sections 03 and 04 augmented to bootcamp quality with targeted enrichment based on content analysis (not just file size). 03_loader_and_exec_format: - overlay_system.md: full rewrite — tree architecture diagram, HUNK_OVERLAY binary format, overlay manager runtime internals, worked binary example, linker support, modern alternatives - hunk_relocation.md: full rewrite — visual before/after diagram, patching algorithm with code, RELOC32SHORT and DREL32 formats, PC-relative impact comparison table, self-referencing relocs, error scenarios, Python reloc scanner tool 04_linking_and_libraries: - library_structure.md: full rewrite — ASCII memory layout diagram, JMP table encoding (why 6 bytes), MakeLibrary internals with both function array formats, complete library creation example with .fd file, checksum verification, lifecycle state diagram - shared_libraries_runtime.md: full rewrite — OpenLibrary 4-step resolution path, ramlib disk loader internals, disk search path, version negotiation table (v33-v47), CloseLibrary/Expunge deep dive, memory-low sweep, common pitfalls table - register_conventions.md: full rewrite — FPU register map, inter-library A6 save/restore pattern, small-data model with __saveds keyword, varargs/TagItem pattern deep dive, stack-based wrapper explanation, disassembly identification Updated indexes: - 03_loader_and_exec_format/README.md - 04_linking_and_libraries/README.md - Root README.md (sections 03 and 04)
51 lines
2.8 KiB
Markdown
51 lines
2.8 KiB
Markdown
[← Home](../README.md)
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# Executable Loader & HUNK Format
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## Overview
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This section covers the complete lifecycle of an AmigaOS executable:
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1. **HUNK file format** — the binary container for all AmigaOS executables, libraries, and object files
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2. **Loader pipeline** — how `dos.library` loads and relocates an executable into memory
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3. **Object files** — how compilers produce relocatable object files for the linker
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4. **Overlays** — how programs larger than available memory use the overlay system
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## Contents
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| File | Topic |
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|---|---|
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| [hunk_format.md](hunk_format.md) | Complete HUNK binary specification — all 22 hunk type codes with wire format, memory flags, advisory bits |
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| [hunk_ext_deep_dive.md](hunk_ext_deep_dive.md) | HUNK_EXT: exports (EXT_DEF), imports (EXT_REF32), commons, linker resolution |
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| [hunk_relocation.md](hunk_relocation.md) | Relocation mechanics: visual before/after, patching algorithm, RELOC32/SHORT/DREL32, PC-relative impact |
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| [hunk_debug_info.md](hunk_debug_info.md) | HUNK_SYMBOL and HUNK_DEBUG: stabs format (SAS/C, GCC), debugger consumption, stripping |
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| [exe_load_pipeline.md](exe_load_pipeline.md) | LoadSeg → AllocMem → relocation → segment chain → CreateProc → entry point |
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| [object_file_format.md](object_file_format.md) | Compiler object files (HUNK_UNIT), multi-section layout, HUNK_LIB archives, linker operation |
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| [overlay_system.md](overlay_system.md) | HUNK_OVERLAY: tree architecture, runtime overlay manager, worked binary example, modern alternatives |
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## Why HUNK?
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HUNK is the native AmigaOS executable format, used from AmigaOS 1.0 through 3.x. It predates ELF/COFF and has these key properties:
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- **Segmented**: separate code, data, and BSS hunks with independent memory allocation
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- **Relocatable**: all absolute references are patched at load time (no ASLR; base address changes each run)
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- **Typed memory**: each hunk can request `CHIP` or `FAST` memory independently
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- **Symbol-complete**: optional HUNK_SYMBOL and HUNK_DEBUG hunks carry debugging information
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## Key Concepts
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| Term | Meaning |
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|---|---|
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| **Hunk** | One contiguous block in the binary (code, data, BSS, etc.) |
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| **Segment** | A loaded hunk at runtime — a `BPTR`-linked list |
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| **Segment list** | Chain of loaded hunks returned by `LoadSeg()` |
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| **BPTR** | Amiga byte pointer — 32-bit value right-shifted by 2 (`ptr >> 2`) |
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| **Relocation** | Patching absolute addresses based on actual load address |
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| **LVO** | Library Vector Offset — negative offset from library base |
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## References
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- ADCD 2.1: `Includes_and_Autodocs_3._guide/` — dos.library LoadSeg autodoc
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- NDK39: `dos/dos.h` — BPTR, segment handling macros
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- *Amiga ROM Kernel Reference Manual: Libraries* — AmigaDOS chapter
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- http://amigadev.elowar.com/read/ADCD_2.1/Libraries_Manual_guide/node0150.html
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