Pure ASM / boot image (flat-bin + archive)

Minimal OS-dev style pipeline: assemble raw binaries with NASM, then pack a FAT floppy/image with an optional boot sector.

Project layout

myos/
  dcr.toml
  src/
    boot.asm      # boot sector (512 bytes)
    kernel.asm    # payload

For multiple flat artifacts, use a workspace (one member per binary) or separate packages; a single flat-bin package produces one binary per source stem.

Boot package (flat-bin)

[package]
name = "boot"
version = "0.1.0"

[build]
language = "asm"
compiler = "nasm"
kind = "flat-bin"
extension = "bin"
roots = ["src/boot.asm"]

dcr build
# → target/<…>/debug/boot.bin  (NASM -f bin, no link)

Disk image after build

[archive]
output = "target/{profile}/disk.img"
format = "fat12"
size = "1440K"
label = "MYOS"
bootsector = "target/{profile}/boot.bin"

[[archive.layout]]
from = "target/{profile}/kernel.bin"
to = "KERNEL.BIN"

• format: fat12, fat16, or fat32
• size: bytes or K/KB/M/MB/G/GB (default ~1.44 MiB)
• bootsector: written only when offset is omitted or 0
• from may be a glob; {profile} is substituted in paths

C kernel → flat binary

[build]
language = "c"
compiler = "clang"
kind = "flat-bin"
freestanding = true
filename = "kernel"
extension = "bin"
ldflags = ["-T", "linker.ld"]

Pipeline: objects → temporary linked ELF → objcopy -O binary → kernel.bin. Requires objcopy / llvm-objcopy in PATH.

Other assemblers

Tool	Notes
FASM	Write format binary in the source; DCR writes <stem>.bin directly
GAS	Assemble .s → obj → objcopy -O binary
LLC	language = "llvm_ir" → obj → objcopy
MASM	COFF obj → objcopy (needs binutils/LLVM objcopy)

Notes

• Single-file roots are supported: roots = ["src/boot.asm"].
• --force re-runs build.steps / build.post_steps as well as recompilation.
• Prefer kind = "elf" if you need a relocatable ELF kernel without stripping to raw binary.