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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.
172 lines
4.1 KiB
Markdown
172 lines
4.1 KiB
Markdown
[← Home](../README.md) · [Linking & Libraries](README.md)
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# Function Definition (.fd) Files
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## Overview
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**Function Definition files** (`.fd`) are the authoritative source of truth for AmigaOS library ABIs. They define:
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- The **name** of every library function
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- The **LVO** (Library Vector Offset) — the negative offset used to call it
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- The **register parameters** — which M68k registers carry each argument
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- The **bias** (starting offset, always negative)
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Every AmigaOS library call ultimately traces back to an `.fd` file.
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---
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## File Location
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In the NDK39:
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```
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NDK39/fd/
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dos_lib.fd
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exec_lib.fd
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graphics_lib.fd
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intuition_lib.fd
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icon_lib.fd
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...
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```
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Also part of the AmigaOS developer CD (adjust to your NDK path):
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```
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NDK39/fd/
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```
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---
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## .fd File Format
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```
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##base _DOSBase ; library base variable name
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##bias 30 ; first LVO = -30 (4 mandatory: -6,-12,-18,-24)
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##public
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Open(name,accessMode)(D1,D2) ; LVO -30
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Close(file)(D1) ; LVO -36
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Read(file,buffer,length)(D1,D2,D3); LVO -42
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Write(file,buffer,length)(D1,D2,D3); LVO -48
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...
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##private
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_InternalOpen(...) ; private function, not in public ABI
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```
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### Grammar Rules
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| Directive | Meaning |
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|---|---|
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| `##base _LibBase` | Name of the library base global variable |
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| `##bias N` | Starting LVO magnitude; first public function is at `-N` |
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| `##public` | Following functions are part of the public ABI |
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| `##private` | Following functions are internal/private |
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| `FuncName(args)(regs)` | Function with argument names and register assignments |
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The LVO of function `n` (0-indexed from first public) is:
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```
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LVO = -(bias + n × 6)
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```
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---
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## Register Notation
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Register assignments are listed in order matching the argument list, using Amiga register names:
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```
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Open(name, accessMode)(D1, D2)
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```
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Means:
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- `name` → D1
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- `accessMode` → D2
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- Caller must put library base in A6 (by convention)
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Special register names:
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- `A6` — always the library base (implicit, not listed)
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- `A0`–`A3`, `D0`–`D7` — data and address registers
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- `D0` — return value (by convention)
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---
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## LVO Calculation Example
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For `dos_lib.fd` with `##bias 30`:
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| LVO | Function |
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|---|---|
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| -6 | `Open` (mandatory) |
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| -12 | `Close` (mandatory) |
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| -18 | `Expunge` (mandatory) |
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| -24 | `Reserved` (mandatory) |
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| -30 | first public function |
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| -36 | second public function |
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| ... | |
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| -144 | `SetComment` |
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| -150 | `SetProtection` |
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The actual LVOs match `dos/dos.h` defines:
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```c
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#define DOS_Open (-30)
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#define DOS_Close (-36)
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#define DOS_Read (-42)
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```
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---
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## Proto Includes (Generated from .fd)
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The `proto/` directory contains compiler-specific call wrappers generated from `.fd` files:
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```c
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/* proto/dos.h — generated automatically from dos_lib.fd */
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#ifndef PROTO_DOS_H
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#include <clib/dos_protos.h> /* function prototypes */
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#include <inline/dos.h> /* inline register call stubs */
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#endif
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```
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`inline/dos.h` contains:
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```c
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#define Open(name,accessMode) \
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({ ULONG _r; \
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__asm volatile("movea.l %1,a6; jsr -30(a6)" : "=r"(_r) : "r"(_DOSBase) : "a6"); \
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_r; })
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```
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---
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## .fd Files and Reverse Engineering
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When reversing an Amiga binary, `.fd` files give you the **complete function name and parameter register map** for every library call. If you see:
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```asm
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MOVEA.L $00BEEF04, A6 ; graphics.library base
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JSR -$114(A6) ; LVO -276
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```
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Look up `-276` in `graphics_lib.fd`:
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```
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-276 ÷ 6 = 46th function from start of table
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```
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Or directly look at `graphics/graphics.h` or `proto/graphics.h` for the constant:
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```c
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#define GFX_BltBitMap (-276)
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/* → JSR -276(A6) = BltBitMap() */
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```
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---
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## Full LVO Table Reconstruction
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See [lvo_table.md](lvo_table.md) for the complete process of reconstructing a library's JMP table from scratch during reverse engineering.
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---
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## References
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- NDK39: `fd/` directory — all `.fd` files
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- NDK39: `proto/` directory — generated call wrappers
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- NDK39: `clib/` directory — raw C prototypes
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- ADCD 2.1: library chapters reference LVOs
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- Community: `https://wiki.amigaos.net/wiki/Fd_Files`
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