diff --git a/src/main.rs b/src/main.rs
index 882d1ad..f820a7c 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -21,14 +21,29 @@ fn get_input_string() -> io::Result<String> {
 }
 
 fn main() -> Result<()> {
-    use vm::obj::syn::{lexer, parser};
+    use vm::{
+        state::State,
+        obj::{
+            assemble::{Asm, Assemble},
+            syn::{lexer, parser},
+        }
+    };
     let text = get_input_string()?;
     let lexerdef = lexer::lexerdef();
     let lexer = lexerdef.lexer(&text);
     let (res, errors) = parser::parse(&lexer);
-    for err in errors {
+    for err in errors.iter() {
         println!("{}", err.pp(&lexer, &parser::token_epp));
     }
-    println!("{:?}", res);
+    if !errors.is_empty() {
+        return Ok(());
+    }
+    let res = res.unwrap();
+    let mut asm = Asm::default();
+    let object = res.assemble(&mut asm)?;
+    let mut state = State::new();
+    state.load_object(object, 64 * 1024 * 1024)?;
+    let status = state.exec()?;
+    println!("exit status: {}", status);
     Ok(())
 }
diff --git a/src/vm/addr.rs b/src/vm/addr.rs
index 0b102aa..e13ab95 100644
--- a/src/vm/addr.rs
+++ b/src/vm/addr.rs
@@ -4,7 +4,7 @@ use std::{
     ops::{Add, AddAssign},
 };
 
-#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
+#[derive(Debug, Default, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
 pub struct Addr(pub u64);
 
 impl LowerHex for Addr {
diff --git a/src/vm/error.rs b/src/vm/error.rs
index 9d5db5a..3eeb6fd 100644
--- a/src/vm/error.rs
+++ b/src/vm/error.rs
@@ -5,14 +5,21 @@ use snafu::Snafu;
 pub enum VmError {
     #[snafu(display("illegal register: 0x{:02x}", reg))]
     IllegalReg { reg: Reg },
+
     #[snafu(display("memory address out of bounds: 0x{:016x}", addr))]
     MemOutOfBounds { addr: Addr },
+
     #[snafu(display("illegal instruction opcode: 0x{:04x}", op))]
     IllegalOp { op: InstOp },
+
     #[snafu(display("illegal destination specification: 0b{:08b}", spec))]
     IllegalDestSpec { spec: u8 },
+
     #[snafu(display("illegal source specification: 0b{:08b}", spec))]
     IllegalSourceSpec { spec: u8 },
+
+    #[snafu(display("object to load spans too much memory"))]
+    ObjectTooLarge { object_size: usize, max_mem: usize },
 }
 
 pub type Result<T, E = VmError> = std::result::Result<T, E>;
diff --git a/src/vm/inst.rs b/src/vm/inst.rs
index 309f6c6..13539e3 100644
--- a/src/vm/inst.rs
+++ b/src/vm/inst.rs
@@ -46,6 +46,7 @@ instructions! {
     DUMP  = 0xF002,
 }
 
+#[derive(Debug, Clone, Copy)]
 pub enum Inst {
     Add(Dest, Source),
     Sub(Dest, Source),
@@ -98,6 +99,33 @@ impl Inst {
             Inst::Dump => DUMP,
         }
     }
+
+    pub fn len(&self) -> usize {
+        match self {
+            Inst::Add(dest, source)
+                | Inst::Sub(dest, source)
+                | Inst::Mul(dest, source)
+                | Inst::Div(dest, source)
+                | Inst::Mod(dest, source)
+                | Inst::And(dest, source)
+                | Inst::Or(dest, source)
+                | Inst::Xor(dest, source)
+                | Inst::Shl(dest, source)
+                | Inst::Shr(dest, source)
+                | Inst::INeg(dest, source)
+                | Inst::Inv(dest, source)
+                | Inst::Not(dest, source)
+                | Inst::Mov(dest, source) => { 3 + dest.len() + source.len() }
+            Inst::CmpEq(s1, s2)
+                | Inst::CmpLt(s1, s2) => { 3 + s1.len() + s2.len() }
+            Inst::Jmp(v)
+                | Inst::Jz(v)
+                | Inst::Jnz(v) => { 3 + v.len() }
+            Inst::Halt
+                | Inst::Nop
+                | Inst::Dump => { 2 }
+        }
+    }
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
@@ -110,6 +138,16 @@ pub enum Source {
     Imm(u64),
 }
 
+impl Source {
+    pub fn len(&self) -> usize {
+        match self {
+            Source::Addr64(_) | Source::Addr32(_) | Source::Addr16(_) | Source::Addr8(_) => 8,
+            Source::Reg(_) => 1,
+            Source::Imm(_) => 8,
+        }
+    }
+}
+
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum Dest {
     Addr64(Addr),
@@ -119,6 +157,15 @@ pub enum Dest {
     Reg(Reg),
 }
 
+impl Dest {
+    pub fn len(&self) -> usize {
+        match self {
+            Dest::Addr64(_) | Dest::Addr32(_) | Dest::Addr16(_) | Dest::Addr8(_) => 8,
+            Dest::Reg(_) => 1,
+        }
+    }
+}
+
 pub const DEST_ADDR64: u8 = 0b0000;
 pub const DEST_ADDR32: u8 = 0b0001;
 pub const DEST_ADDR16: u8 = 0b0010;
diff --git a/src/vm/mem.rs b/src/vm/mem.rs
index 9071a58..79fcb15 100644
--- a/src/vm/mem.rs
+++ b/src/vm/mem.rs
@@ -1,78 +1,65 @@
 use crate::vm::{addr::*, error::*, inst::*, reg::*};
-use std::{convert::TryInto, ops::Index, mem};
+use byteorder::{ReadBytesExt, WriteBytesExt, LE};
+use std::io::Cursor;
 
 pub struct MemCursor<T> {
-    pos: Addr,
-    mem: T,
+    cursor: Cursor<T>,
 }
 
 impl<T> MemCursor<T>
-    where T: AsRef<[u8]>
+    where Cursor<T>: ReadBytesExt,
+          T: AsRef<[u8]>
 {
     pub fn new(mem: T) -> Self {
-        MemCursor { pos: Addr(0), mem }
+        MemCursor { cursor: Cursor::new(mem) }
     }
 
-    pub fn position(&self) -> Addr {
-        self.pos
+    pub fn position(&self) -> u64 {
+        self.cursor.position()
     }
 
     pub fn set_position<P: Into<Addr>>(&mut self, position: P) {
-        self.pos = position.into();
+        self.cursor.set_position((position.into()).0)
     }
 
     pub fn next_u8_unchecked(&mut self) -> u8 {
-        let val = self[self.pos];
-        self.pos += 1u64;
-        val
+        self.cursor.read_u8().unwrap()
     }
 
     pub fn next_u8(&mut self) -> Result<u8> {
-        self.check_addr(self.pos)
+        self.check_addr(self.position())
             .map(|_| self.next_u8_unchecked())
     }
 
     pub fn next_u16_unchecked(&mut self) -> u16 {
-        let (int_bytes, _) = self.mem.as_ref()
-            .split_at(mem::size_of::<u16>());
-        let val = u16::from_le_bytes(int_bytes.try_into().unwrap());
-        self.pos += 2u64;
-        val
+        self.cursor.read_u16::<LE>().unwrap()
     }
 
     pub fn next_u16(&mut self) -> Result<u16> {
-        self.check_addr(self.pos)
+        self.check_addr(self.position())
             .map(|_| self.next_u16_unchecked())
     }
 
     pub fn next_u32_unchecked(&mut self) -> u32 {
-        let (int_bytes, _) = self.mem.as_ref()
-            .split_at(mem::size_of::<u32>());
-        let val = u32::from_le_bytes(int_bytes.try_into().unwrap());
-        self.pos += 4u64;
-        val
+        self.cursor.read_u32::<LE>().unwrap()
     }
 
     pub fn next_u32(&mut self) -> Result<u32> {
-        self.check_addr(self.pos)
+        self.check_addr(self.position())
             .map(|_| self.next_u32_unchecked())
     }
     
     pub fn next_u64_unchecked(&mut self) -> u64 {
-        let (int_bytes, _) = self.mem.as_ref()
-            .split_at(mem::size_of::<u64>());
-        let val = u64::from_le_bytes(int_bytes.try_into().unwrap());
-        self.pos += 8u64;
-        val
+        self.cursor.read_u64::<LE>().unwrap()
     }
 
     pub fn next_u64(&mut self) -> Result<u64> {
-        self.check_addr(self.pos)
+        self.check_addr(self.position())
             .map(|_| self.next_u64_unchecked())
     }
 
     pub fn next_addr(&mut self) -> Result<Addr> {
-        self.check_addr(self.pos)
+        self.check_addr(self.position())
             .map(|_| self.next_addr_unchecked())
     }
 
@@ -81,6 +68,7 @@ impl<T> MemCursor<T>
     }
 
     pub fn next_inst(&mut self) -> Result<Inst> {
+        let start = self.position();
         let op = self.next_u16()?;
 
         macro_rules! dest_source {
@@ -102,7 +90,7 @@ impl<T> MemCursor<T>
                 Ok(Inst::$variant(source))
             }};
         }
-        match op {
+        let inst = match op {
             ADD => dest_source!(Add),
             SUB => dest_source!(Sub),
             MUL => dest_source!(Mul),
@@ -126,7 +114,11 @@ impl<T> MemCursor<T>
             NOP => Ok(Inst::Nop),
             DUMP => Ok(Inst::Dump),
             _ => Err(VmError::IllegalOp { op }),
-        }
+        }?;
+        let end = self.position();
+        let len = (end - start) as usize;
+        assert_eq!(len, inst.len());
+        Ok(inst)
     }
 
     fn next_source_source(&mut self) -> Result<(Source, Source)> {
@@ -181,16 +173,62 @@ impl<T> MemCursor<T>
             Ok(reg)
         }
     }
+}
 
-    fn check_addr(&self, addr: Addr) -> Result<()> {
-        if addr > self.mem.as_ref().len() {
-            Err(VmError::MemOutOfBounds { addr })
+impl<T> MemCursor<T>
+    where T: AsRef<[u8]>
+{
+    fn check_addr(&self, addr: u64) -> Result<()> {
+        if addr > (self.cursor.get_ref().as_ref().len() as u64) {
+            Err(VmError::MemOutOfBounds { addr: Addr(addr) })
         } else {
             Ok(())
         }
     }
 }
 
+impl<T> MemCursor<T>
+    where Cursor<T>: WriteBytesExt,
+          T: AsRef<[u8]>
+{
+    pub fn write_u8_unchecked(&mut self, value: u8) {
+        self.cursor.write_u8(value).unwrap();
+    }
+
+    pub fn write_u8(&mut self, value: u8) -> Result<()> {
+        self.check_addr(self.position())
+            .map(|_| self.write_u8_unchecked(value))
+    }
+
+    pub fn write_u16_unchecked(&mut self, value: u16) {
+        self.cursor.write_u16::<LE>(value).unwrap();
+    }
+
+    pub fn write_u16(&mut self, value: u16) -> Result<()> {
+        self.check_addr(self.position())
+            .map(|_| self.write_u16_unchecked(value))
+    }
+
+    pub fn write_u32_unchecked(&mut self, value: u32) {
+        self.cursor.write_u32::<LE>(value).unwrap();
+    }
+
+    pub fn write_u32(&mut self, value: u32) -> Result<()> {
+        self.check_addr(self.position())
+            .map(|_| self.write_u32_unchecked(value))
+    }
+
+    pub fn write_u64_unchecked(&mut self, value: u64) {
+        self.cursor.write_u64::<LE>(value).unwrap();
+    }
+
+    pub fn write_u64(&mut self, value: u64) -> Result<()> {
+        self.check_addr(self.position())
+            .map(|_| self.write_u64_unchecked(value))
+    }
+}
+
+/*
 ////////////////////////////////////////////////////////////////////////////////
 // Index impl
 ////////////////////////////////////////////////////////////////////////////////
@@ -217,3 +255,4 @@ impl<T: AsRef<[u8]>> Index<Addr> for MemCursor<T> {
         self.index(addr.0)
     }
 }
+*/
diff --git a/src/vm/obj/assemble.rs b/src/vm/obj/assemble.rs
new file mode 100644
index 0000000..b59a352
--- /dev/null
+++ b/src/vm/obj/assemble.rs
@@ -0,0 +1,325 @@
+use crate::vm::{
+    addr::*,
+    inst,
+    obj::{obj::*, syn::ast::*},
+};
+use byteorder::{WriteBytesExt, LE};
+use snafu::Snafu;
+use std::collections::HashMap;
+
+pub trait Assemble {
+    type Out;
+    fn assemble(&self, asm: &mut Asm) -> Result<Self::Out>;
+}
+
+#[derive(Debug, Default)]
+pub struct Asm {
+    names: Vec<HashMap<String, Addr>>,
+    pos: Addr,
+}
+
+impl Asm {
+    /// Gets all names defined in a data section, their positions, and puts them into a hashmap.
+    fn gather_names(&self, section: &DataSection) -> Result<HashMap<String, Addr>> {
+        let mut names = HashMap::new();
+        let mut addr = Addr(0);
+        for line in section.lines.iter() {
+            match line {
+                DataLine::ValueDef(v) => addr += v.len(),
+                DataLine::Inst(inst) => addr += inst.len(),
+                DataLine::Export(_) => {}
+                DataLine::Label(label) => {
+                    if let Some(_) = names.insert(label.to_string(), addr) {
+                        return Err(AssembleError::DuplicateLabel {
+                            name: label.to_string(),
+                        });
+                    }
+                }
+            }
+        }
+        assert_eq!(addr, section.len());
+        Ok(names)
+    }
+
+    /// Gets an address value from a name, if it exists. Searches local -> global.
+    fn lookup_name(&self, name: &str) -> Result<Addr> {
+        self.names
+            .iter()
+            .rev()
+            .filter_map(|names| names.get(name).copied())
+            .next()
+            .ok_or_else(|| AssembleError::UnknownName { name: name.to_string() })
+    }
+}
+
+impl Assemble for Vec<SectionDef> {
+    type Out = Object;
+    fn assemble(&self, asm: &mut Asm) -> Result<Self::Out> {
+        // collect globals
+        let mut globals = HashMap::new();
+        for section in self.iter() {
+            let section = if let SectionDef::Data(d) = section {
+                d
+            } else {
+                continue;
+            };
+            let names = asm.gather_names(section)?;
+            for export in section.exports() {
+                let addr = *names
+                    .get(export)
+                    .ok_or_else(|| AssembleError::UnknownExport {
+                        name: export.to_string(),
+                    })?;
+                if globals.contains_key(export) {
+                    return Err(AssembleError::DuplicateExport {
+                        name: export.to_string(),
+                    })?;
+                }
+                globals.insert(export.to_string(), addr);
+            }
+        }
+        // TODO : detect section overlap
+        // TODO : single meta section
+        asm.names.clear();
+        asm.names.push(globals);
+
+        let sections = self.iter()
+            .map(|section| section.assemble(asm))
+            .collect::<Result<_>>()?;
+        Ok(Object { version: OBJ_VERSION, sections, })
+    }
+}
+
+impl Assemble for SectionDef {
+    type Out = Section;
+
+    fn assemble(&self, asm: &mut Asm) -> Result<Self::Out> {
+        match self {
+            SectionDef::Data(section) => section.assemble(asm),
+            SectionDef::Meta(section) => section.assemble(asm),
+        }
+    }
+}
+
+impl Assemble for DataSection {
+    type Out = Section;
+
+    fn assemble(&self, asm: &mut Asm) -> Result<Self::Out> {
+        let names = asm.gather_names(self)?;
+        asm.names.push(names);
+        asm.pos = Addr(0);
+        let section_len = self.len() as u64;
+        let (start, end) = match self.org {
+            SectionOrg::Start(start) => (start, start + (section_len as u64)),
+            SectionOrg::StartEnd(start, end) => (start, end),
+        };
+        if start > end {
+            return Err(AssembleError::StartGreaterThanEnd { start, end, });
+        }
+        let len = end - start - 1;
+        if len > section_len {
+            return Err(AssembleError::SectionTooShort {
+                section_end: end,
+                section_size: start + section_len,
+            });
+        }
+
+        let mut contents = Vec::with_capacity(section_len as usize);
+        for line in self.lines.iter() {
+            contents.extend(line.assemble(asm)?);
+            asm.pos += line.len();
+        }
+        assert_eq!(contents.len() as u64, section_len, "in section {}", self.name);
+        asm.names.pop();
+        Ok(Section::Data {
+            start,
+            len: section_len,
+            contents,
+        })
+    }
+}
+
+impl Assemble for MetaSection {
+    type Out = Section;
+
+    fn assemble(&self, asm: &mut Asm) -> Result<Self::Out> {
+        let mut entries = HashMap::new();
+        for line in self.lines.iter() {
+            if entries.contains_key(&line.name) {
+                return Err(AssembleError::DuplicateMetaName { name: line.name.to_string() });
+            }
+            let value = match &line.value {
+                Value::Int(i) => *i,
+                Value::Name(s) => asm.lookup_name(s.as_str())?.0,
+                Value::Reg(_) | Value::Here => return Err(AssembleError::IllegalMetaValue {
+                    name: line.name.to_string(),
+                    value: line.value.clone(),
+                }),
+            };
+            entries.insert(line.name.to_string(), value);
+        }
+        Ok(Section::Meta { entries })
+    }
+}
+
+impl Assemble for DataLine {
+    type Out = Vec<u8>;
+
+    fn assemble(&self, asm: &mut Asm) -> Result<Self::Out> {
+        match self {
+            DataLine::ValueDef(v) => v.assemble(asm),
+            DataLine::Inst(i) => i.assemble(asm),
+            DataLine::Export(_) | DataLine::Label(_) => Ok(Vec::new()),
+        }
+    }
+}
+
+impl Assemble for ValueDef {
+    type Out = Vec<u8>;
+
+    fn assemble(&self, _: &mut Asm) -> Result<Self::Out> {
+        match self {
+            ValueDef::Int(x) => Ok(x.to_le_bytes().to_vec()),
+            ValueDef::String(s) => {
+                let bytes = s.bytes();
+                let mut out = s.len().to_le_bytes().to_vec();
+                out.extend(bytes);
+                Ok(out)
+            }
+            ValueDef::ZString(z) => {
+                let bytes = z.bytes();
+                let mut out = z.len().to_le_bytes().to_vec();
+                out.extend(bytes);
+                Ok(out)
+            }
+        }
+    }
+}
+
+impl Assemble for Inst {
+    type Out = Vec<u8>;
+
+    fn assemble(&self, asm: &mut Asm) -> Result<Self::Out> {
+        let len = self.len();
+
+        macro_rules! map_inst {
+            ($op:expr, $dest:expr, $source:expr) => {{
+                let mut bytes = Vec::with_capacity(len);
+                bytes.write_u16::<LE>($op).unwrap();
+                let dest = $dest;
+                let dest_encoding = dest.dest_encoding()
+                    .ok_or_else(|| AssembleError::IllegalDestValue { value: dest.clone(), })?;
+                let source = $source;
+                let source_encoding = source.source_encoding();
+                bytes.write_u8((dest_encoding << 4) | source_encoding).unwrap();
+                bytes.extend(dest.assemble(asm)?);
+                bytes.extend(source.assemble(asm)?);
+                assert_eq!(
+                    self.len(), bytes.len(),
+                    "instruction size mismatch in {} instruction - {:?} produces these bytes {:?}",
+                    stringify!($op), self, bytes
+                );
+                Ok(bytes)
+            }};
+
+            ($op:expr, $source:expr) => {{
+                let mut bytes = Vec::with_capacity(len);
+                bytes.write_u16::<LE>($op).unwrap();
+                let source = $source;
+                let source_encoding = source.source_encoding();
+                bytes.write_u8(source_encoding).unwrap();
+                bytes.extend(source.assemble(asm)?);
+                assert_eq!(
+                    self.len(), bytes.len(),
+                    "instruction size mismatch in {} instruction - {:?} produces these bytes {:?}",
+                    stringify!($op), self, bytes
+                );
+                Ok(bytes)
+            }};
+
+            ($op:expr) => {{
+                let mut bytes = Vec::with_capacity(len);
+                bytes.write_u16::<LE>($op).unwrap();
+                assert_eq!(
+                    self.len(), bytes.len(),
+                    "instruction size mismatch in {} instruction - {:?} produces these bytes {:?}",
+                    stringify!($op), self, bytes
+                );
+                Ok(bytes)
+            }};
+        }
+        match self {
+            Inst::Add(v1, v2) => map_inst!(inst::ADD, v1, v2),
+            Inst::Sub(v1, v2) => map_inst!(inst::SUB, v1, v2),
+            Inst::Mul(v1, v2) => map_inst!(inst::MUL, v1, v2),
+            Inst::Div(v1, v2) => map_inst!(inst::DIV, v1, v2),
+            Inst::Mod(v1, v2) => map_inst!(inst::MOD, v1, v2),
+            Inst::And(v1, v2) => map_inst!(inst::AND, v1, v2),
+            Inst::Or(v1, v2) => map_inst!(inst::OR, v1, v2),
+            Inst::Xor(v1, v2) => map_inst!(inst::XOR, v1, v2),
+            Inst::Shl(v1, v2) => map_inst!(inst::SHL, v1, v2),
+            Inst::Shr(v1, v2) => map_inst!(inst::SHR, v1, v2),
+            Inst::INeg(v1, v2) => map_inst!(inst::INEG, v1, v2),
+            Inst::Inv(v1, v2) => map_inst!(inst::INV, v1, v2),
+            Inst::Not(v1, v2) => map_inst!(inst::NOT, v1, v2),
+            // TODO/BUG: CmpEq and CmpLt both take two sources instead of a source and destination
+            Inst::CmpEq(v1, v2) => map_inst!(inst::CMPEQ, v1, v2),
+            Inst::CmpLt(v1, v2) => map_inst!(inst::CMPLT, v1, v2),
+            Inst::Mov(v1, v2) => map_inst!(inst::MOV, v1, v2),
+            Inst::Jmp(v) => map_inst!(inst::JMP, v),
+            Inst::Jz(v) => map_inst!(inst::JZ, v),
+            Inst::Jnz(v) => map_inst!(inst::JNZ, v),
+            Inst::Halt => map_inst!(inst::HALT),
+            Inst::Nop => map_inst!(inst::NOP),
+            Inst::Dump => map_inst!(inst::DUMP),
+        }
+    }
+}
+
+impl Assemble for Value {
+    type Out = Vec<u8>;
+
+    fn assemble(&self, asm: &mut Asm) -> Result<Self::Out> {
+        match self {
+            Value::Int(i) => Ok(i.to_le_bytes().to_vec()),
+            Value::Reg(r) => Ok(vec![*r]),
+            Value::Name(name) => {
+                let value = asm.lookup_name(name.as_str())?;
+                Ok(value.0.to_le_bytes().to_vec())
+            }
+            Value::Here => Ok(asm.pos.0.to_le_bytes().to_vec()),
+        }
+    }
+}
+
+#[derive(Debug, Snafu)]
+pub enum AssembleError {
+    #[snafu(display("unknown name: {}", name))]
+    UnknownName { name: String },
+
+    #[snafu(display("unknown export name: {}", name))]
+    UnknownExport { name: String },
+
+    #[snafu(display("duplicate label definition: {}", name))]
+    DuplicateLabel { name: String },
+
+    #[snafu(display("duplicate meta entry name: {}", name))]
+    DuplicateMetaName { name: String },
+
+    #[snafu(display("illegal meta value for entry name {}: {:?}", name, value))]
+    IllegalMetaValue { name: String, value: Value },
+
+    #[snafu(display("duplicate exported name: {}", name))]
+    DuplicateExport { name: String },
+
+    #[snafu(display("section start ({:#x}) is greater than end ({:#x})", start, end))]
+    StartGreaterThanEnd { start: u64, end: u64 },
+
+    #[snafu(display("section end ({:#x}) too short for section content size ({:#x})", section_end, section_size))]
+    SectionTooShort { section_end: u64, section_size: u64 },
+
+    #[snafu(display("illegal instruction destination value: {:?}", value))]
+    IllegalDestValue { value: Value, },
+}
+
+pub type Result<T, E = AssembleError> = std::result::Result<T, E>;
diff --git a/src/vm/obj/mod.rs b/src/vm/obj/mod.rs
index 4f04478..b7c4760 100644
--- a/src/vm/obj/mod.rs
+++ b/src/vm/obj/mod.rs
@@ -1,3 +1,4 @@
+pub mod assemble;
 pub mod error;
 pub mod obj;
 pub mod syn;
diff --git a/src/vm/obj/obj.rs b/src/vm/obj/obj.rs
index 05a8ba8..b8138f1 100644
--- a/src/vm/obj/obj.rs
+++ b/src/vm/obj/obj.rs
@@ -8,6 +8,7 @@ use std::{
 };
 
 pub const MAGIC: u64 = 0xDEAD_BEA7_BA5E_BA11;
+pub const OBJ_VERSION: u32 = 0;
 const OBJECT_HEADER_LEN: usize = 16; // 8 + 4 + 4
 
 #[derive(Debug)]
@@ -20,7 +21,7 @@ impl Object {
     pub fn from_bytes(bytes: &[u8]) -> Result<Self> {
         let mut cursor = Cursor::new(bytes);
         let magic = cursor.read_u64::<LE>()?;
-        if magic != magic {
+        if magic != MAGIC {
             return Err(ParseError::WrongMagic);
         }
         let version = cursor.read_u32::<LE>()?;
@@ -33,6 +34,14 @@ impl Object {
         }
         Ok(Object { version, sections })
     }
+
+    pub fn virtual_len(&self) -> usize {
+        self.sections.iter()
+            .map(|s| match s {
+                Section::Data { start, len, .. } => { (start + len) as usize }
+                Section::Meta { .. } => { 0 }
+            }).max().unwrap_or(0)
+    }
 }
 
 macro_rules! section_kind {
@@ -66,7 +75,6 @@ macro_rules! section_kind {
 section_kind! {
     pub enum SectionKind {
         Data = 0x00,
-        Code = 0x10,
         Meta = 0xFF,
     }
 }
@@ -75,12 +83,7 @@ section_kind! {
 pub enum Section {
     Data {
         start: u64,
-        end: u64,
-        contents: Vec<u8>,
-    },
-    Code {
-        start: u64,
-        end: u64,
+        len: u64,
         contents: Vec<u8>,
     },
     Meta {
@@ -98,7 +101,6 @@ impl Section {
         let kind: SectionKind = cursor.read_u8()?.try_into()?;
         match kind {
             SectionKind::Data => Section::data_section_from_bytes(bytes),
-            SectionKind::Code => Section::code_section_from_bytes(bytes),
             SectionKind::Meta => Section::meta_section_from_bytes(bytes),
         }
     }
@@ -106,23 +108,11 @@ impl Section {
     fn data_section_from_bytes(bytes: &[u8]) -> Result<Self> {
         let mut cursor = Cursor::new(bytes);
         let start = cursor.read_u64::<LE>()?;
-        let end = cursor.read_u64::<LE>()?;
+        let len = cursor.read_u64::<LE>()?;
         let contents = &bytes[cursor.position() as usize..];
         Ok(Section::Data {
             start,
-            end,
-            contents: From::from(contents),
-        })
-    }
-
-    fn code_section_from_bytes(bytes: &[u8]) -> Result<Self> {
-        let mut cursor = Cursor::new(bytes);
-        let start = cursor.read_u64::<LE>()?;
-        let end = cursor.read_u64::<LE>()?;
-        let contents = &bytes[cursor.position() as usize..];
-        Ok(Section::Code {
-            start,
-            end,
+            len,
             contents: From::from(contents),
         })
     }
diff --git a/src/vm/obj/syn/ast.rs b/src/vm/obj/syn/ast.rs
index cef91f7..0a39693 100644
--- a/src/vm/obj/syn/ast.rs
+++ b/src/vm/obj/syn/ast.rs
@@ -1,4 +1,7 @@
-use crate::vm::reg::Reg;
+use crate::vm::{
+    inst,
+    reg::Reg,
+};
 
 #[derive(Debug, Clone)]
 pub enum SectionDef {
@@ -8,7 +11,7 @@ pub enum SectionDef {
 
 #[derive(Debug, Clone)]
 pub struct MetaSection {
-    pub values: Vec<MetaLine>,
+    pub lines: Vec<MetaLine>,
 }
 
 #[derive(Debug, Clone)]
@@ -20,10 +23,27 @@ pub struct MetaLine {
 #[derive(Debug, Clone)]
 pub struct DataSection {
     pub name: String,
-    pub org: Option<SectionOrg>,
+    pub org: SectionOrg,
     pub lines: Vec<DataLine>,
 }
 
+impl DataSection {
+    pub fn exports(&self) -> impl Iterator<Item=&str> {
+        self.lines.iter()
+            .filter_map(|line| if let DataLine::Export(s) = line {
+                Some(s.as_str())
+            } else {
+                None
+            })
+    }
+
+    pub fn len(&self) -> usize {
+        self.lines.iter()
+            .map(DataLine::len)
+            .sum()
+    }
+}
+
 #[derive(Debug, Clone)]
 pub enum SectionOrg {
     Start(u64),
@@ -38,6 +58,16 @@ pub enum DataLine {
     Label(String),
 }
 
+impl DataLine {
+    pub fn len(&self) -> usize {
+        match self {
+            DataLine::ValueDef(v) => v.len(),
+            DataLine::Inst(i) => i.len(),
+            DataLine::Export(_) | DataLine::Label(_) => 0,
+        }
+    }
+}
+
 #[derive(Debug, Clone)]
 pub enum ValueDef {
     Int(u64),
@@ -45,6 +75,16 @@ pub enum ValueDef {
     ZString(String),
 }
 
+impl ValueDef {
+    pub fn len(&self) -> usize {
+        match self {
+            ValueDef::Int(_) => 8,
+            ValueDef::String(s) => 8 + s.as_bytes().len(),
+            ValueDef::ZString(s) => s.as_bytes().len() + 1,
+        }
+    }
+}
+
 #[derive(Debug, Clone)]
 pub enum Value {
     Int(u64),
@@ -52,7 +92,34 @@ pub enum Value {
     Name(String),
     Here,
     //Array(Vec<Value>),
-    //Deref(Value, Size
+    //Deref(Value, IntSize),
+}
+
+impl Value {
+    pub fn len(&self) -> usize {
+        match self {
+            // TODO : immediate int sizes
+            Value::Int(_) => 8,
+            Value::Reg(_) => 1,
+            Value::Name(_) => 8,
+            Value::Here => 8,
+        }
+    }
+    
+    pub fn dest_encoding(&self) -> Option<u8> {
+        match self {
+            Value::Int(_) | Value::Name(_) | Value::Here => None,
+            Value::Reg(_) => Some(inst::DEST_REG),
+        }
+    }
+
+    pub fn source_encoding(&self) -> u8 {
+        match self {
+            Value::Int(_) => inst::SOURCE_IMM64,
+            Value::Reg(_) => inst::SOURCE_REG,
+            Value::Name(_) | Value::Here => inst::SOURCE_IMM64,
+        }
+    }
 }
 
 #[derive(Debug, Clone)]
@@ -80,3 +147,32 @@ pub enum Inst {
     Nop,
     Dump,
 }
+
+impl Inst {
+    pub fn len(&self) -> usize {
+        match self {
+            Inst::Add(v1, v2)
+                | Inst::Sub(v1, v2)
+                | Inst::Mul(v1, v2)
+                | Inst::Div(v1, v2)
+                | Inst::Mod(v1, v2)
+                | Inst::And(v1, v2)
+                | Inst::Or(v1, v2)
+                | Inst::Xor(v1, v2)
+                | Inst::Shl(v1, v2)
+                | Inst::Shr(v1, v2)
+                | Inst::INeg(v1, v2)
+                | Inst::Inv(v1, v2)
+                | Inst::Not(v1, v2)
+                | Inst::CmpEq(v1, v2)
+                | Inst::CmpLt(v1, v2)
+                | Inst::Mov(v1, v2) => { 3 + v1.len() + v2.len() }
+            Inst::Jmp(v)
+                | Inst::Jz(v)
+                | Inst::Jnz(v) => { 3 + v.len() }
+            Inst::Halt
+                | Inst::Nop
+                | Inst::Dump => { 2 }
+        }
+    }
+}
diff --git a/src/vm/obj/syn/parser.y b/src/vm/obj/syn/parser.y
index fd011dd..a151209 100644
--- a/src/vm/obj/syn/parser.y
+++ b/src/vm/obj/syn/parser.y
@@ -7,8 +7,8 @@ SectionDefs -> Vec<SectionDef>:
     ;
 
 SectionDef -> SectionDef:
-      'DIR_META' MetaBlock { SectionDef::Meta(MetaSection { values: $2 }) }
-    | 'DIR_SECTION' Name MaybeSectionOrg DataBlock {
+      'DIR_META' MetaBlock { SectionDef::Meta(MetaSection { lines: $2 }) }
+    | 'DIR_SECTION' Name SectionOrg DataBlock {
         SectionDef::Data(DataSection {
             name: $2,
             org: $3,
@@ -27,11 +27,6 @@ MetaLines -> Vec<MetaLine>:
 
 MetaLine -> MetaLine: Name 'COLON' Value { MetaLine { name: $1, value: $3 } };
 
-MaybeSectionOrg -> Option<SectionOrg>:
-      SectionOrg { Some($1) }
-    | { None }
-    ;
-
 SectionOrg -> SectionOrg:
       Int { SectionOrg::Start($1) }
     | Int 'DOTDOT' Int { SectionOrg::StartEnd($1, $3) }
diff --git a/src/vm/state.rs b/src/vm/state.rs
index c147b1f..0ce5cde 100644
--- a/src/vm/state.rs
+++ b/src/vm/state.rs
@@ -1,4 +1,4 @@
-use crate::vm::{addr::*, error::*, flags::*, mem::*, reg::*};
+use crate::vm::{addr::*, error::*, flags::*, inst::*, mem::*, obj::obj::*, reg::*};
 
 pub struct State {
     regs: [u64; NUM_REGS],
@@ -13,15 +13,49 @@ impl State {
         }
     }
 
+    pub fn load_object(&mut self, object: Object, max_mem: usize) -> Result<()> {
+        // TODO : detecting section overlap
+        let mem_len = object.virtual_len();
+        if mem_len > max_mem {
+            return Err(VmError::ObjectTooLarge {
+                object_size: mem_len,
+                max_mem,
+            });
+        }
+        let mut mem = vec![0u8; max_mem];
+        for section in object.sections {
+            match section {
+                Section::Data {
+                    start,
+                    len,
+                    contents,
+                } => {
+                    for offset in 0..len {
+                        mem[(start + offset) as usize] = contents[offset as usize];
+                    }
+                }
+                Section::Meta { entries } => {
+                    if let Some(addr) = entries.get("entry") {
+                        self.set_reg_unchecked(IP, *addr);
+                    }
+                }
+            }
+        }
+        self.mem = mem;
+
+        Ok(())
+    }
+
     pub fn mem_cursor(&self, addr: Addr) -> MemCursor<&[u8]> {
         let mut cursor = MemCursor::new(self.mem.as_slice());
         cursor.set_position(addr);
         cursor
     }
 
-    pub fn run(&mut self) -> Result<u64> {
-
-        Ok(self.get_reg_unchecked(STATUS))
+    pub fn mem_cursor_mut(&mut self, addr: Addr) -> MemCursor<&mut [u8]> {
+        let mut cursor = MemCursor::new(self.mem.as_mut_slice());
+        cursor.set_position(addr);
+        cursor
     }
 
     ////////////////////////////////////////////////////////////////////////////////
@@ -51,6 +85,10 @@ impl State {
         }
     }
 
+    pub fn ip(&self) -> u64 {
+        self.get_reg_unchecked(IP)
+    }
+
     ////////////////////////////////////////////////////////////////////////////////
     // Flags
     ////////////////////////////////////////////////////////////////////////////////
@@ -60,6 +98,10 @@ impl State {
         unsafe { Flags::from_bits_unchecked(self.get_reg_unchecked(FLAGS)) }
     }
 
+    pub fn contains_flags(&self, flags: Flags) -> bool {
+        self.flags().contains(flags)
+    }
+
     pub fn insert_flags(&mut self, flags: Flags) {
         let mut new_flags = self.flags();
         new_flags.insert(flags);
@@ -75,4 +117,157 @@ impl State {
     pub fn set_flags(&mut self, flags: Flags) {
         self.set_reg_unchecked(FLAGS, flags.bits());
     }
+
+    ////////////////////////////////////////////////////////////////////////////////
+    // Execution
+    ////////////////////////////////////////////////////////////////////////////////
+    pub fn is_halted(&self) -> bool {
+        self.contains_flags(Flags::HALT)
+    }
+
+    pub fn exec(&mut self) -> Result<u64> {
+        while !self.is_halted() {
+            self.tick()?;
+        }
+
+        Ok(self.get_reg_unchecked(STATUS))
+    }
+
+    fn tick(&mut self) -> Result<()> {
+        let mut cursor = self.mem_cursor(Addr(self.ip()));
+        let inst = cursor.next_inst()?;
+        let mut next_ip = self.ip() + (inst.len() as u64);
+        match inst {
+            Inst::Add(d, s) => {
+                let value = self.load_dest(d)?.wrapping_add(self.load_source(s)?);
+                self.store_dest(d, value)?;
+            }
+            Inst::Sub(d, s) => {
+                let value = self.load_dest(d)?.wrapping_sub(self.load_source(s)?);
+                self.store_dest(d, value)?;
+            }
+            Inst::Mul(d, s) => {
+                let value = self.load_dest(d)?.wrapping_mul(self.load_source(s)?);
+                self.store_dest(d, value)?;
+            }
+            Inst::Div(d, s) => {
+                // TODO : catch divide by zero
+                let value = self.load_dest(d)?.wrapping_div(self.load_source(s)?);
+                self.store_dest(d, value)?;
+            }
+            Inst::Mod(d, s) => {
+                let value = self.load_dest(d)? % self.load_source(s)?;
+                self.store_dest(d, value)?;
+            }
+            Inst::And(d, s) => {
+                let value = self.load_dest(d)? & self.load_source(s)?;
+                self.store_dest(d, value)?;
+            }
+            Inst::Or(d, s) => {
+                let value = self.load_dest(d)? | self.load_source(s)?;
+                self.store_dest(d, value)?;
+            }
+            Inst::Xor(d, s) => {
+                let value = self.load_dest(d)? ^ self.load_source(s)?;
+                self.store_dest(d, value)?;
+            }
+            Inst::Shl(d, s) => {
+                let value = self.load_dest(d)? << self.load_source(s)?;
+                self.store_dest(d, value)?;
+            }
+            Inst::Shr(d, s) => {
+                let value = self.load_dest(d)? >> self.load_source(s)?;
+                self.store_dest(d, value)?;
+            }
+            Inst::INeg(d, s) => {
+                let value = (!self.load_source(s)?).wrapping_add(1);
+                self.store_dest(d, value)?;
+            }
+            Inst::Inv(d, s) => {
+                let value = !self.load_source(s)?;
+                self.store_dest(d, value)?;
+            }
+            Inst::Not(d, s) => {
+                let value = (self.load_source(s)? == 0) as u64;
+                self.store_dest(d, value)?;
+            }
+            Inst::CmpEq(s1, s2) => {
+                let cmp = self.load_source(s1)? == self.load_source(s2)?;
+                if cmp {
+                    self.insert_flags(Flags::COMPARE);
+                } else {
+                    self.remove_flags(Flags::COMPARE);
+                }
+            }
+            Inst::CmpLt(s1, s2) => {
+                let cmp = self.load_source(s1)? < self.load_source(s2)?;
+                if cmp {
+                    self.insert_flags(Flags::COMPARE);
+                } else {
+                    self.remove_flags(Flags::COMPARE);
+                }
+            }
+            Inst::Jmp(s) => {
+                next_ip = self.load_source(s)?;
+            }
+            Inst::Jz(s) => {
+                if !self.contains_flags(Flags::COMPARE) {
+                    next_ip = self.load_source(s)?;
+                }
+            }
+            Inst::Jnz(s) => {
+                if self.contains_flags(Flags::COMPARE) {
+                    next_ip = self.load_source(s)?;
+                }
+            }
+            Inst::Mov(d, s) => {
+                let value = self.load_source(s)?;
+                self.store_dest(d, value)?;
+            }
+            Inst::Halt => {
+                self.insert_flags(Flags::HALT);
+            }
+            Inst::Nop => {}
+            Inst::Dump => {
+                // TODO - dump
+            }
+        }
+        self.set_reg_unchecked(IP, next_ip);
+        Ok(())
+    }
+
+    fn store_dest(&mut self, dest: Dest, value: u64) -> Result<()> {
+        match dest {
+            Dest::Addr64(a) => self.mem_cursor_mut(a).write_u64(value),
+            Dest::Addr32(a) => self
+                .mem_cursor_mut(a)
+                .write_u32((value & 0xffff_ffff) as u32),
+            Dest::Addr16(a) => self.mem_cursor_mut(a).write_u16((value & 0xffff) as u16),
+            Dest::Addr8(a) => self.mem_cursor_mut(a).write_u8((value & 0xff) as u8),
+            Dest::Reg(reg) => self.set_reg(reg, value),
+        }
+    }
+
+    fn load_source(&self, source: Source) -> Result<u64> {
+        let value = match source {
+            Source::Addr64(a) => self.mem_cursor(a).next_u64()?,
+            Source::Addr32(a) => self.mem_cursor(a).next_u32()? as u64,
+            Source::Addr16(a) => self.mem_cursor(a).next_u16()? as u64,
+            Source::Addr8(a) => self.mem_cursor(a).next_u8()? as u64,
+            Source::Reg(reg) => self.get_reg(reg)?,
+            Source::Imm(u) => u,
+        };
+        Ok(value)
+    }
+
+    fn load_dest(&self, dest: Dest) -> Result<u64> {
+        let value = match dest {
+            Dest::Addr64(a) => self.mem_cursor(a).next_u64()?,
+            Dest::Addr32(a) => self.mem_cursor(a).next_u32()? as u64,
+            Dest::Addr16(a) => self.mem_cursor(a).next_u16()? as u64,
+            Dest::Addr8(a) => self.mem_cursor(a).next_u8()? as u64,
+            Dest::Reg(reg) => self.get_reg(reg)?,
+        };
+        Ok(value)
+    }
 }