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https://github.com/DQNEO/goas
port of GNU Assembler written in go
https://github.com/DQNEO/goas
assembler golang x86-64
Last synced: about 2 months ago
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port of GNU Assembler written in go
- Host: GitHub
- URL: https://github.com/DQNEO/goas
- Owner: DQNEO
- License: mit
- Created: 2021-09-07T03:49:01.000Z (about 3 years ago)
- Default Branch: main
- Last Pushed: 2023-07-13T02:38:51.000Z (about 1 year ago)
- Last Synced: 2024-06-20T15:02:39.765Z (3 months ago)
- Topics: assembler, golang, x86-64
- Language: Assembly
- Homepage:
- Size: 1.02 MB
- Stars: 65
- Watchers: 3
- Forks: 2
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
README
# goas - a port of GNU Assembler written in go
`goas` is an assembler that behaves like `as`, GNU Assembler.
This is just a toy program to illustrate how an assembler works. Actually I learned how an assembler works by writing this program :).
It does not mean to support all syntax or instructions, but Linux x86-64 AT&T syntax only.
However, for any input it supports, it behaves exactly the same as `as`,
which means it produces the very same binary files (*.o) as `as` does.
The most interesting thing is that it can assemble my Go compiler [babygo](https://github.com/DQNEO/babygo). (You can see it by running `make babygo`.)
# Requirements
You need a linux with gcc installed.
If you are using MacOS or Windows, you can use my docker image to run `goas`.
```
$ docker run --rm -it -v `pwd`:/mnt/goas -w /mnt/goas dqneo/ubuntu-compiler-go bash
```
# How to build
```
$ go build
```
# How to use
Prepare a small assembly file `test.s`
```asm
.text
.global _start
_start:
movq $42, %rdi # status
movq $60, %rax # sys_exit
syscall
```
And you can assemble it
```terminal
$ ./goas -o test.o test.s
$ ld -o test test.o
$ ./test; echo $?
42
```
## Demo
# Supported Instructions
See test files under `/t` and `/t2` directory to know what syntax it can assemble.
# Design
`goas` is composed of 4 files.
File|Role
---|---
parser.go | parser
encoder.go | instruction encoder
elf_writer.go | ELF format writer
main.go | miscellaneous tasks
### Parser
`parser.go` is a simple recursive descent parser. The boundary between lexer nd parser are not clearly separated.
Each line of source code is converted into a statement object.
It produces a list of statements in the end.
### Instruction encoder
`encoder.go` translates an instruction with operands into a piece of x86-64 binary machine code.
### ELF format Writer
`elf_writer.go` composes an object which represents ELF file format and write it into a binary object file.
# Test
```
$ docker run --rm -it -v `pwd`:/mnt/goas -w /mnt/goas dqneo/ubuntu-compiler-go make test
```
# References
## ELF
* https://refspecs.linuxfoundation.org/elf/elf.pdf ELF Specification
* https://man7.org/linux/man-pages/man5/elf.5.html ELF man
* https://sourceware.org/git/?p=glibc.git;a=blob;f=elf/elf.h;h=4738dfa28f6549fc11654996a15659dc8007e686;hb=HEAD libc elf.h
## GNU Assembler
* https://sourceware.org/binutils/docs-2.37/as.html Manual of GNU Assembler
## X86-64 Instruction set and encoding
* https://software.intel.com/content/www/us/en/develop/articles/intel-sdm.html Intel® 64 and IA-32 Architectures Software Developer Manuals
* https://hikalium.github.io/opv86/ Opcode/Instruction finder for x86_64
# License
MIT
# Author
[@DQNEO](https://twitter.com/DQNEO)