mipsevm: fix initial heap, set initial PC to entrypoint

mipsevm/patch.go

@@ -9,7 +9,17 @@ import (
 )
 
 func LoadELF(f *elf.File) (*State, error) {
-	s := &State{}
+	s := &State{
+		PC:        uint32(f.Entry),
+		Hi:        0,
+		Lo:        0,
+		Heap:      1 << 20, // start heap at 1 GiB offset for now
+		Registers: [32]uint32{},
+		Memory:    nil,
+		Exit:      0,
+		Exited:    false,
+		Step:      0,
+	}
 
 	for i, prog := range f.Progs {
 		if prog.Type == 0x70000003 { // MIPS_ABIFLAGS

mipsevm/unicorn.go

@@ -42,7 +42,7 @@ func LoadUnicorn(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)
+			log.Fatal("invalid interrupt ", intno, " at step ", st.Step)
 		}
 		syscallNum, _ := mu.RegRead(uc.MIPS_REG_V0)
 
@@ -64,7 +64,7 @@ func HookUnicorn(st *State, mu uc.Unicorn, stdOut, stdErr io.Writer) error {
 			a0, _ := mu.RegRead(uc.MIPS_REG_A0)
 			sz, _ := mu.RegRead(uc.MIPS_REG_A1)
 			if a0 == 0 {
-				v0 = 0x20000000 + heap_start
+				v0 = uint64(st.Heap)
 				st.Heap += uint32(sz)
 			} else {
 				v0 = a0