10 files changed, 375 insertions, 0 deletions
diff --git a/vm/go.mod b/vm/go.mod
new file mode 100644
index 0000000..725da6d
--- /dev/null
+++ b/vm/go.mod
@@ -0,0 +1,5 @@
+module s00.xyz/evm
+
+go 1.20
+
+require github.com/holiman/uint256 v1.2.2 // indirect
diff --git a/vm/go.sum b/vm/go.sum
new file mode 100644
index 0000000..e0f03a0
--- /dev/null
+++ b/vm/go.sum
@@ -0,0 +1,2 @@
+github.com/holiman/uint256 v1.2.2 h1:TXKcSGc2WaxPD2+bmzAsVthL4+pEN0YwXcL5qED83vk=
+github.com/holiman/uint256 v1.2.2/go.mod h1:SC8Ryt4n+UBbPbIBKaG9zbbDlp4jOru9xFZmPzLUTxw=
diff --git a/vm/instruction.go b/vm/instruction.go
new file mode 100644
index 0000000..5cd56e6
--- /dev/null
+++ b/vm/instruction.go
@@ -0,0 +1,147 @@
+package main
+
+import (
+	 "github.com/holiman/uint256"
+)
+
+type Handler func(vm *Evm)
+
+type Instruction struct {
+	name string
+	n    int // number of params
+	handler Handler  
+}
+
+type Inst Instruction // shorthand
+
+// i miss c macros :(
+var Instructions = [256]Instruction{
+	STOP: {
+        	name: "STOP",
+		n: 0,
+		handler: func(vm *Evm) { vm.stopped = true },
+	} ,
+	ADD: {
+		name: "ADD", 
+		n: 2, 
+		handler: func(vm *Evm) { 
+			o := uint256.NewInt(0)
+			vm.stack.Push(o.Add(vm.stack.Pop(), vm.stack.Pop()))
+		},
+	},
+	MUL: {
+		n: 2, 
+		name: "MUL",
+		handler: func(vm *Evm) {
+			o := uint256.NewInt(0)
+			vm.stack.Push(o.Mul(vm.stack.Pop(), vm.stack.Pop())) 
+		},
+	},
+	SUB: {
+		n: 2, 
+		name: "SUB",
+		handler: func(vm *Evm) {
+			o := uint256.NewInt(0)
+			vm.stack.Push(o.Sub(vm.stack.Pop(), vm.stack.Pop()))
+		},
+	},
+	DIV: {
+		n: 2, 
+		name: "DIV",
+		handler: func(vm *Evm) { 
+			o := uint256.NewInt(0)
+			vm.stack.Push(o.Div(vm.stack.Pop(), vm.stack.Pop()))
+		},	
+	},
+	SDIV: { 
+		n: 2, 
+		name: "SDIV", 
+		handler: func(vm *Evm) {
+			o := uint256.NewInt(0)
+			vm.stack.Push(o.SDiv(vm.stack.Pop(), vm.stack.Pop())) 
+		},
+	},
+	MOD: {
+		n: 2, 
+		name: "MOD",
+		handler: func(vm *Evm) { 
+			o := uint256.NewInt(0)
+			vm.stack.Push(o.Mod(vm.stack.Pop(), vm.stack.Pop())) 
+		},
+	},
+	SMOD: {
+		n: 2, 
+		name: "SMOD", 
+		handler: func(vm *Evm) { 
+			o := uint256.NewInt(0)
+			vm.stack.Push(o.SMod(vm.stack.Pop(), vm.stack.Pop())) 
+		},
+	},
+	ADDMOD: { 
+		n: 3, 
+		name: "ADDMOD",
+		handler: func(vm *Evm) { 
+			o := uint256.NewInt(0)
+			vm.stack.Push(o.AddMod(vm.stack.Pop(), vm.stack.Pop(), vm.stack.Pop())) 
+		},
+	},
+	MULMOD: {
+		n: 3, 
+		name: "MULMOD", 
+		handler: func(vm *Evm) {
+			o := uint256.NewInt(0)
+			vm.stack.Push(o.MulMod(vm.stack.Pop(), vm.stack.Pop(), vm.stack.Pop()))
+		},
+	},
+	POP: { 
+		n: 1, 
+		name: "POP", 
+		handler: func(vm *Evm) { 
+			vm.stack.Pop() 
+		},
+	}, 
+	MLOAD: { 
+		n: 1, 
+		name: "MLOAD",
+	},
+	MSTORE: {
+		n: 2, 
+		name: "MSTORE", 
+	},
+	MSTORE8: { 
+		n: 2, 
+		name: "MSTORE8", 
+	},
+	PUSH1:  { name: "PUSH1" },
+	PUSH2:  { name: "PUSH2" },
+	PUSH3:  { name: "PUSH3" },
+	PUSH4:  { name: "PUSH4" },
+	PUSH5:  { name: "PUSH5" },
+	PUSH6:  { name: "PUSH6" },
+	PUSH7:  { name: "PUSH7" },
+	PUSH8:  { name: "PUSH8" },
+	PUSH9:  { name: "PUSH9" },
+	PUSH10: { name: "PUSH0" },
+	PUSH11: { name: "PUSH11" },
+	PUSH12: { name: "PUSH12" },
+	PUSH13: { name: "PUSH13" },
+	PUSH14: { name: "PUSH14" },
+	PUSH15: { name: "PUSH15" },
+	PUSH16: { name: "PUSH16" },
+	PUSH17: { name: "PUSH17" },
+	PUSH18: { name: "PUSH18" },
+	PUSH19: { name: "PUSH19" },
+	PUSH20: { name: "PUSH20" },
+	PUSH21: { name: "PUSH21" },
+	PUSH22: { name: "PUSH22" },
+	PUSH23: { name: "PUSH23" },
+	PUSH24: { name: "PUSH24" },
+	PUSH25: { name: "PUSH25" },
+	PUSH26: { name: "PUSH26" },
+	PUSH27: { name: "PUSH27" },
+	PUSH28: { name: "PUSH28" },
+	PUSH29: { name: "PUSH29" },
+	PUSH30: { name: "PUSH30" },
+	PUSH31: { name: "PUSH31" },
+	PUSH32: { name: "PUSH32" },
+}
diff --git a/vm/instructions.go b/vm/instructions.go
new file mode 100644
index 0000000..5a1220b
--- /dev/null
+++ b/vm/instructions.go
@@ -0,0 +1,3 @@
+package main
+
+type InstructionHandler func (vm *Evm)
diff --git a/vm/main.go b/vm/main.go
new file mode 100644
index 0000000..61aeebb
--- /dev/null
+++ b/vm/main.go
@@ -0,0 +1,26 @@
+package main
+
+import (
+	"fmt"
+	"os"
+)
+
+func main() {
+	
+	if (len(os.Args) != 2) {
+		fmt.Fprintf(os.Stderr, "usage: %s bytecode.bin\n")
+		os.Exit(1)
+	}
+
+	b, err := os.ReadFile(os.Args[1])
+
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "failed to open file: %s\n", os.Args[1])
+		os.Exit(1)
+	}
+
+	vm := NewEvm(b)
+
+	vm.Start()
+}
+
diff --git a/vm/memory.go b/vm/memory.go
new file mode 100644
index 0000000..0a9dd2c
--- /dev/null
+++ b/vm/memory.go
@@ -0,0 +1,39 @@
+package main
+
+import (
+	"github.com/holiman/uint256"
+	"log"
+)
+
+type Memory []byte
+
+// store 256b word at offset in memory
+func (m *Memory) sw(ost uint64, val *uint256.Int) {
+	if ost + 32 > uint64(len(*m)) {
+		*m = append(*m, make([]byte, ost + 32 - uint64(len(*m)))...)
+	}
+
+	bytes := val.Bytes32()
+	copy((*m)[ost:], bytes[:])
+}
+
+// store byte at offset in memory
+func (m *Memory) sb(ost uint64, val byte) {
+	if ost + 1 > uint64(len(*m)) {
+		*m = append(*m, make([]byte, ost + 1 - uint64(len(*m)))...)
+	}
+	
+	(*m)[ost] = val
+}
+
+// loads 256b word fron offset in memory
+func (m *Memory) ld(ost uint64) []byte {
+	if ost + 32 > uint64(len(*m)) {
+		log.Fatal("trying to load out of memory")
+	}
+
+	r := make([]byte, 32)
+	copy(r, (*m)[ost:ost+32])
+	return r
+}
+
diff --git a/vm/opcodes.go b/vm/opcodes.go
new file mode 100644
index 0000000..b3d4229
--- /dev/null
+++ b/vm/opcodes.go
@@ -0,0 +1,57 @@
+package main
+
+type Opcode byte
+
+const (
+	STOP = iota
+	ADD 
+	MUL
+	SUB
+	DIV
+	SDIV
+	MOD
+	SMOD
+	ADDMOD
+	MULMOD
+	POP = 0x50
+	MLOAD = 0x51
+	MSTORE = 0x52
+	MSTORE8 = 0x53
+	PUSH1 = 0x60
+	PUSH2 = 0x61
+	PUSH3 = 0x62
+	PUSH4 = 0x63
+	PUSH5 = 0x64
+	PUSH6 = 0x65
+	PUSH7 = 0x66
+	PUSH8 = 0x67
+	PUSH9 = 0x68
+	PUSH10 = 0x69
+	PUSH11 = 0x6a
+	PUSH12 = 0x6b
+	PUSH13 = 0x6c
+	PUSH14 = 0x6d 
+	PUSH15 = 0x6e
+	PUSH16 = 0x6f
+	PUSH17 = 0x70
+	PUSH18 = 0x71
+	PUSH19 = 0x72
+	PUSH20 = 0x73
+	PUSH21 = 0x74
+	PUSH22 = 0x75
+	PUSH23 = 0x76
+	PUSH24 = 0x77
+	PUSH25 = 0x78
+	PUSH26 = 0x79
+	PUSH27 = 0x7a
+	PUSH28 = 0x7b
+	PUSH29 = 0x7c
+	PUSH30 = 0x7d
+	PUSH31 = 0x7e
+	PUSH32 = 0x7f
+	//...
+) 
+
+func (op *Opcode) String() string {
+	return Instructions[*op].name
+}
diff --git a/vm/rom.go b/vm/rom.go
new file mode 100644
index 0000000..958e70e
--- /dev/null
+++ b/vm/rom.go
@@ -0,0 +1,19 @@
+package main 
+
+import (
+	 "os"
+	 "fmt"
+)
+
+type Rom []byte
+
+func (r *Rom) Fetch(pc *uint64, n uint64) []byte {
+	if (*pc + n > uint64(len(*r)) - 1) {
+		fmt.Fprintf(os.Stderr, "error: trying to read outside of rom\n")
+		os.Exit(1)
+	}
+	x := make([]byte, n)
+	copy(x, (*r)[*pc:*pc + n])
+	*pc += n
+	return x
+}
diff --git a/vm/stack.go b/vm/stack.go
new file mode 100644
index 0000000..fc1cbd4
--- /dev/null
+++ b/vm/stack.go
@@ -0,0 +1,32 @@
+package main
+
+import (
+	"log"
+
+	 "github.com/holiman/uint256"
+)
+
+const STACK_CAP = (1 << 10)
+
+type Stack []uint256.Int
+
+func (s *Stack) Push(x *uint256.Int) {
+	*s = append(*s, *x)
+	if len(*s) + 1 > STACK_CAP {
+		log.Fatal("stack overflow")
+	}
+}
+
+func (s *Stack) Pop() *uint256.Int {
+	if len(*s) <= 0 {
+		log.Fatal("stack underflow")
+	}
+
+	r := (*s)[len(*s)-1]
+	*s = (*s)[:len(*s)-1]
+	return &r
+}
+
+func (s *Stack) Peek() *uint256.Int {
+	return &(*s)[len(*s)-1]	
+}
diff --git a/vm/vm.go b/vm/vm.go
new file mode 100644
index 0000000..209ab71
--- /dev/null
+++ b/vm/vm.go
@@ -0,0 +1,45 @@
+package main
+
+import (
+	"fmt"
+	"github.com/holiman/uint256"
+)
+
+type Evm struct {
+	code Rom
+	stack Stack
+	memory Memory
+	pc uint64
+	stopped bool
+}
+
+func NewEvm(_code []byte) *Evm {
+	return &Evm{
+		pc: 0,
+		stopped: true,
+		stack : Stack{},
+		code: _code,
+	}
+}
+
+func (vm *Evm) Start() {
+	vm.stopped = false
+	for !(vm.stopped) {
+		op := vm.code.Fetch(&(vm.pc), 1)[0] 
+		fmt.Printf("pc: %d | opcode: %x -> string: %s\n", vm.pc, op, Instructions[op].name)
+		if op >= PUSH1 && op <= PUSH32 {
+			nb := op - PUSH1 + 1
+			fmt.Printf("pushing %d byte value to the stack!\n", vm.pc, nb)
+			b := vm.code.Fetch(&(vm.pc), uint64(nb))
+		        x := uint256.NewInt(0)
+			x = x.SetBytes(b)
+			vm.stack.Push(x)
+		} else {
+			vm.Execute(op)
+		}
+	}
+}
+
+func (vm *Evm) Execute(op byte) { 
+	Instructions[op].handler(vm)
+}