ft: introduce modrm macro for leaner matching

All instructions which use a modrm instruction
for memory reads from or into a register can
make use of this macro

src/disasm.rs

@@ -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 => {
+                0x00 => modrm!(self, ADD_EbGb),
-                    let (idx, reg) = self.parse_modrm_byte_to_memindex();
+                0x01 => modrm!(self, ADD_EvGv),
-                    Opcode::ADD_EbGb(idx, reg)
+                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}'",

src/disasm_macros.rs

@@ -0,0 +1,8 @@
+#[macro_export]
+/// Generate an Opcode for 'normal' ModRM instructions with mem access and a reg
+macro_rules! modrm {
+    ($self:ident, $variant:ident) => {{
+        let (idx, reg) = $self.parse_modrm_byte();
+        Opcode::$variant(idx, Register::by_id(reg))
+    }};
+}

src/instructions.rs

@@ -43,10 +43,22 @@ pub enum Opcode {
     NOP(),
     // ADD
     ADD_EbGb(MemoryIndex, Register),
-    // MOV
+    ADD_EvGv(MemoryIndex, Register),
-    MOV_BXIv(Register, ImmediateWord),
+    ADD_GbEb(MemoryIndex, Register),
+    ADD_GvEv(MemoryIndex, Register),
+    ADD_ALIb(ImmediateByte),
+    ADD_AXIv(ImmediateWord),
+    // PUSH
+    PUSH(SegmentRegister),
+    // POP
+    POP(SegmentRegister),
+    // OR
+    OR_EbGb(MemoryIndex, Register),
+    OR_GbEb(MemoryIndex, Register),
     // INT
     INT(ImmediateByte),
+    // MOV
+    MOV_BXIv(ImmediateWord),
 }
 
 impl fmt::Display for Opcode {
@@ -54,7 +66,8 @@ impl fmt::Display for Opcode {
         match self {
             Self::INT(byte) => write!(f, "INT, {:x}", byte),
             Self::ADD_EbGb(mem, reg) => write!(f, "ADD {}, {}", mem, reg),
-            Self::MOV_BXIv(reg, word) => write!(f, "MOV {}, {:04x}", reg, word),
+            Self::ADD_GbEb(mem, reg) => write!(f, "ADD {}, {}", reg, mem),
+            Self::MOV_BXIv(word) => write!(f, "MOV BX, {:04x}", word),
             _ => write!(f, "display not yet implemented"),
         }
     }
@@ -83,10 +96,13 @@ pub enum Register {
     SP,
 }
 
+/// Selector for Register or Segment Register
+pub type RegisterId = u8;
+
 #[allow(dead_code)]
 impl Register {
     /// Find the register corresponding to the 8086 bytecode ID
-    pub fn by_id(id: u8) -> Self {
+    pub fn by_id(id: RegisterId) -> Self {
         match id {
             0x00 => Self::AL,
             0x01 => Self::CL,
@@ -133,7 +149,7 @@ impl fmt::Display for Register {
 }
 
 /// Segment Registers of a 8086 processor
-#[derive(Debug)]
+#[derive(Debug, Clone)]
 #[allow(dead_code)]
 pub enum SegmentRegister {
     DS,
@@ -213,13 +229,13 @@ impl fmt::Display for MemoryIndex {
                 },
                 None => match &self.displacement {
                     Some(displacement) => write!(f, "[{}+{}]", base, displacement),
-                    None => write!(f, "[{}]", base),
+                    None => write!(f, "{}", base),
                 },
             },
             None => match &self.index {
                 Some(index) => match &self.displacement {
                     Some(displacement) => write!(f, "{}+{}", index, displacement),
-                    None => write!(f, "[{}]", index),
+                    None => write!(f, "{}", index),
                 },
                 None => panic!("Invalid MemoryIndex encountered"),
             },

src/main.rs

@@ -2,6 +2,7 @@ use clap::{Parser, Subcommand};
 
 mod aout;
 mod disasm;
+mod disasm_macros;
 mod instructions;
 
 #[derive(Subcommand, Debug)]