A mirror of the assembler from the Go compiler, with import paths re-written for the assembler to be functional as a standalone library.
License as per the Go project.
Works, but expect to dig into the assembler godoc's to work out what to set different parameters of obj.Prog to get it to generate specific instructions.
Demonstrates assembly of a NOP & an ADD instruction on x86-64.
package main
import (
"fmt"
asm "github.com/twitchyliquid64/golang-asm"
"github.com/twitchyliquid64/golang-asm/obj"
"github.com/twitchyliquid64/golang-asm/obj/x86"
)
func noop(builder *asm.Builder) *obj.Prog {
prog := builder.NewProg()
prog.As = x86.ANOPL
prog.From.Type = obj.TYPE_REG
prog.From.Reg = x86.REG_AX
return prog
}
func addImmediateByte(builder *asm.Builder, in int32) *obj.Prog {
prog := builder.NewProg()
prog.As = x86.AADDB
prog.To.Type = obj.TYPE_REG
prog.To.Reg = x86.REG_AL
prog.From.Type = obj.TYPE_CONST
prog.From.Offset = int64(in)
return prog
}
func movImmediateByte(builder *asm.Builder, reg int16, in int32) *obj.Prog {
prog := builder.NewProg()
prog.As = x86.AMOVB
prog.To.Type = obj.TYPE_REG
prog.To.Reg = reg
prog.From.Type = obj.TYPE_CONST
prog.From.Offset = int64(in)
return prog
}
func main() {
b, _ := asm.NewBuilder("amd64", 64)
b.AddInstruction(noop(b))
b.AddInstruction(movImmediateByte(b, x86.REG_AL, 16))
b.AddInstruction(addImmediateByte(b, 16))
fmt.Printf("Bin: %x\n", b.Assemble())
}This took me some time to work out, so I'll write a bit here.
-
obj.Prog- godoc -
Some instructions (like NOP, JMP) are abstract per-platform & can be found here
-
(for amd64)
x86 pkg-constants- registers & instructions
Instructions are defined as constants in the package for the relavant architecture, and have an 'A' prefix and a size suffix.
For example, the MOV instruction for 64 bits of data is AMOVQ (well, at least in amd64).
For example, if I wanted to work out how to emit the MOV instruction for 64bits, I would search the go source on github for AMOVQ or x86.AMOVQ. Normally, you see find a few examples where the compiler backend fills in a obj.Prog structure, and you follow it's lead.