marcothms/8086-rs
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

ft: introduce modrm macro for leaner matching

Browse Source 
All instructions which use a modrm instruction
for memory reads from or into a register can
make use of this macro
This commit is contained in:
Marco Thomas
2025-05-12 19:53:25 +09:00
parent 317b5e5db4
commit 51b28b3bac
4 changed files with 51 additions and 16 deletions
Download Patch File Download Diff File Expand all files Collapse all files

28
src/disasm.rs
View File

@@ -2,7 +2,8 @@ use core::fmt;
use std::{fs::File, io::Read, process::exit};
use crate::aout::Aout;
use crate::instructions::{Displacement, MemoryIndex};
use crate::instructions::{Displacement, MemoryIndex, RegisterId, SegmentRegister};
use crate::modrm;
use crate::{
Args,
instructions::{ImmediateByte, ImmediateWord, Instruction, Opcode, Register},
@@ -99,7 +100,7 @@ impl Disassembler {
/// Parse a single modrm byte, return the resulting MemoryIndex and advance the offset.
/// Returns the parsed modrm memory access and the source register
pub fn parse_modrm_byte_to_memindex(&mut self) -> (MemoryIndex, Register) {
pub fn parse_modrm_byte(&mut self) -> (MemoryIndex, RegisterId) {
// advance to operand
self.offset += 1;
let modrm = self.text[self.offset];
@@ -109,7 +110,7 @@ impl Disassembler {
// Calculate ModRM byte with bitmask
let modulo = modrm >> 6;
let reg = (modrm >> 3) & 7;
let reg_id = (modrm >> 3) & 7;
let rm = modrm & 7;
let displacement = match modulo {
@@ -183,7 +184,7 @@ impl Disassembler {
_ => panic!("Invalid ModRM byte encountered"),
};
(index, Register::by_id(reg))
(index, reg_id)
}
/// Decode instructions from the text section of the provided binary
@@ -205,14 +206,23 @@ impl Disassembler {
self.instruction.raw.push(opcode);
self.instruction.opcode = match opcode {
// ADD
0x00 => {
let (idx, reg) = self.parse_modrm_byte_to_memindex();
Opcode::ADD_EbGb(idx, reg)
}
0x00 => modrm!(self, ADD_EbGb),
0x01 => modrm!(self, ADD_EvGv),
0x02 => modrm!(self, ADD_GbEb),
0x03 => modrm!(self, ADD_GvEv),
0x04 => Opcode::ADD_ALIb(ImmediateByte(self.parse_byte())),
0x05 => Opcode::ADD_AXIv(ImmediateWord(self.parse_word())),
// PUSH
0x06 => Opcode::PUSH(SegmentRegister::by_id(self.parse_modrm_byte().1)),
// POP
0x07 => Opcode::POP(SegmentRegister::by_id(self.parse_modrm_byte().1)),
// OR
0x08 => modrm!(self, OR_EbGb),
0x0A => modrm!(self, OR_GbEb),
// INT
0xCD => Opcode::INT(ImmediateByte(self.parse_byte())),
// MOV
0xBB => Opcode::MOV_BXIv(Register::BX, ImmediateWord(self.parse_word())),
0xBB => Opcode::MOV_BXIv(ImmediateWord(self.parse_word())),
_ => {
eprintln!(
"Encountered unknown self.instructionuction '0x{:x}'",