amiga-bootcamp/04_linking_and_libraries

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Linking & Library Integration

Overview

This section documents how AmigaOS shared libraries work at the binary level — how compilers produce library call stubs, how the linker wires them up, and how to reconstruct this mechanism during reverse engineering.

Contents

File	Topic
library_structure.md	Library memory layout, JMP table encoding, MakeLibrary construction, complete library creation example
shared_libraries_runtime.md	OpenLibrary resolution path, ramlib disk loader, version negotiation, expunge mechanics
register_conventions.md	Register ABI: integer, FPU, varargs/TagItem, small-data model, __saveds, inter-library calls
fd_files.md	Function Definition files — the library ABI source of truth, LVO calculation
lvo_table.md	JMP table layout, complete exec.library LVO table, IDA reconstruction script
compiler_stubs.md	How SAS/C, GCC, VBCC call libraries — compiler signature identification
inline_stubs.md	Compiler inline stubs: pragma (SAS/C), inline asm (GCC), __reg (VBCC), stub generation tools
link_libraries.md	Static linking: amiga.lib, sc.lib, libnix, auto.lib, WBStartup glue, stack cookie
startup_code.md	c.o / gcrt0.S: entry contract, CLI vs WB detection, argument parsing, WBStartup message
setfunction.md	Runtime function patching: canonical pattern, chaining, removal, RE detection heuristics

The Library ABI Model

Every AmigaOS shared library exposes its functions through a negative-offset JMP table relative to the library base pointer:

Library base:  LIB+0    → Library node (struct Library)
               LIB-6    → JMP _Open        (mandatory)
               LIB-12   → JMP _Close       (mandatory)
               LIB-18   → JMP _Expunge     (mandatory)
               LIB-24   → JMP _Reserved    (mandatory)
               LIB-30   → JMP _func1       (first user function)
               LIB-36   → JMP _func2
               ...

A C call like OpenLibrary("graphics.library", 0) compiles to:

MOVE.L  4.W, A6          ; A6 = SysBase (exec)
JSR     -552(A6)          ; LVO for OpenLibrary = -552

The negative offset (-552) is the Library Vector Offset (LVO) — a fixed ABI value defined in the library's .fd file and proto/ include.

References

• NDK39: fd/ directory, proto/ includes, inline/ inline stubs
• ADCD 2.1: Library writing guide, ROM Kernel Manual
• http://amigadev.elowar.com/read/ADCD_2.1/Libraries_Manual_guide/node0000.html