mipsevm: syscall unicorn hook, state mem reader util func

mipsevm/run_unicorn.go

@@ -2,13 +2,11 @@ package main
 
 import (
 	"bytes"
-	"encoding/binary"
 	"fmt"
 	"io/ioutil"
 	"log"
 	"os"
 
-	"github.com/ethereum/go-ethereum/common"
 	"github.com/fatih/color"
 	uc "github.com/unicorn-engine/unicorn/bindings/go/unicorn"
 )
@@ -80,51 +78,7 @@ func GetHookedUnicorn(root string, ram map[uint32](uint32), callback func(int, u
 			log.Fatal("invalid interrupt ", intno, " at step ", steps)
 		}
 		syscall_no, _ := mu.RegRead(uc.MIPS_REG_V0)
-		v0 := uint64(0)
-		if syscall_no == 4020 {
-			oracle_hash, _ := mu.MemRead(0x30001000, 0x20)
-			hash := common.BytesToHash(oracle_hash)
-			key := fmt.Sprintf("%s/%s", root, hash)
-			value, err := ioutil.ReadFile(key)
-			check(err)
-
-			tmp := []byte{0, 0, 0, 0}
-			binary.BigEndian.PutUint32(tmp, uint32(len(value)))
-			mu.MemWrite(0x31000000, tmp)
-			mu.MemWrite(0x31000004, value)
-
-			WriteRam(ram, 0x31000000, uint32(len(value)))
-			value = append(value, 0, 0, 0)
-			for i := uint32(0); i < ram[0x31000000]; i += 4 {
-				WriteRam(ram, 0x31000004+i, binary.BigEndian.Uint32(value[i:i+4]))
-			}
-		} else if syscall_no == 4004 {
-			fd, _ := mu.RegRead(uc.MIPS_REG_A0)
-			buf, _ := mu.RegRead(uc.MIPS_REG_A1)
-			count, _ := mu.RegRead(uc.MIPS_REG_A2)
-			bytes, _ := mu.MemRead(buf, count)
-			WriteBytes(int(fd), bytes)
-		} else if syscall_no == 4090 {
-			a0, _ := mu.RegRead(uc.MIPS_REG_A0)
-			sz, _ := mu.RegRead(uc.MIPS_REG_A1)
-			if a0 == 0 {
-				v0 = 0x20000000 + heap_start
-				heap_start += sz
-			} else {
-				v0 = a0
-			}
-		} else if syscall_no == 4045 {
-			v0 = 0x40000000
-		} else if syscall_no == 4120 {
-			v0 = 1
-		} else if syscall_no == 4246 {
-			// exit group
-			mu.RegWrite(uc.MIPS_REG_PC, 0x5ead0000)
-		} else {
-			//fmt.Println("syscall", syscall_no)
-		}
-		mu.RegWrite(uc.MIPS_REG_V0, v0)
-		mu.RegWrite(uc.MIPS_REG_A3, 0)
+
 	}, 0, 0)
 
 	if callback != nil {

mipsevm/state.go

@@ -3,6 +3,7 @@ package main
 import (
 	"encoding/hex"
 	"fmt"
+	"io"
 )
 
 const (
@@ -73,6 +74,43 @@ func (s *State) SetMemory(addr uint32, v uint32, size uint32) {
 	}
 }
 
+type memReader struct {
+	state *State
+	addr  uint32
+	count uint32
+}
+
+func (r *memReader) Read(dest []byte) (n int, err error) {
+	if r.count == 0 {
+		return 0, io.EOF
+	}
+
+	// Keep iterating over memory until we have all our data.
+	// It may wrap around the address range, and may not be aligned
+	endAddr := r.addr + r.count
+
+	pageIndex := r.addr >> pageAddrSize
+	start := r.addr & pageAddrMask
+	end := uint32(pageSize)
+
+	if pageIndex == (endAddr >> pageAddrSize) {
+		end = endAddr & pageAddrMask
+	}
+	p, ok := r.state.Memory[pageIndex]
+	if ok {
+		n = copy(dest, p[start:end])
+	} else {
+		n = copy(dest, make([]byte, end-start)) // default to zeroes
+	}
+	r.addr += uint32(n)
+	r.count -= uint32(n)
+	return n, nil
+}
+
+func (s *State) ReadMemory(addr uint32, count uint32) io.Reader {
+	return &memReader{state: s, addr: addr, count: count}
+}
+
 // TODO merkleization
 
 // TODO convert access-list to calldata and state-sets for EVM

mipsevm/unicorn.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"fmt"
+	"io"
 	"log"
 
 	uc "github.com/unicorn-engine/unicorn/bindings/go/unicorn"
@@ -17,16 +18,44 @@ func LoadUnicorn(st *State, mu uc.Unicorn) error {
 	return nil
 }
 
-func HookUnicorn(st *State, mu uc.Unicorn) error {
+func HookUnicorn(st *State, mu uc.Unicorn, stdOut, stdErr io.Writer) error {
 	_, err := mu.HookAdd(uc.HOOK_INTR, func(mu uc.Unicorn, intno uint32) {
 		if intno != 17 {
 			log.Fatal("invalid interrupt ", intno, " at step ", steps)
 		}
 		syscallNum, _ := mu.RegRead(uc.MIPS_REG_V0)
-		// TODO process syscalls
+
+		v0 := uint64(0)
 		switch syscallNum {
-		// TODO mmap
+		case 4004: // write
+			fd, _ := mu.RegRead(uc.MIPS_REG_A0)
+			addr, _ := mu.RegRead(uc.MIPS_REG_A1)
+			count, _ := mu.RegRead(uc.MIPS_REG_A2)
+			switch fd {
+			case 1:
+				_, _ = io.Copy(stdOut, st.ReadMemory(uint32(addr), uint32(count)))
+			case 2:
+				_, _ = io.Copy(stdErr, st.ReadMemory(uint32(addr), uint32(count)))
+			default:
+				// ignore other output data
+			}
+		case 4090: // mmap
+			a0, _ := mu.RegRead(uc.MIPS_REG_A0)
+			sz, _ := mu.RegRead(uc.MIPS_REG_A1)
+			if a0 == 0 {
+				v0 = 0x20000000 + heap_start
+				st.Heap += uint32(sz)
+			} else {
+				v0 = a0
+			}
+			// TODO mmap
+		case 4045: // brk
+			v0 = 0x40000000
+		case 4246: // exit_group
+			mu.RegWrite(uc.MIPS_REG_PC, 0x5ead0000)
 		}
+		mu.RegWrite(uc.MIPS_REG_V0, v0)
+		mu.RegWrite(uc.MIPS_REG_A3, 0)
 	}, 0, 0)
 	if err != nil {
 		return fmt.Errorf("failed to set up interrupt/syscall hook: %w", err)