fix minor issue in shift ops

contracts/MIPS.sol

@@ -94,7 +94,7 @@ contract MIPS {
   }
 
   // TODO: test ll and sc
-  function stepNextPC(bytes32 stateHash, uint32 pc, uint64 nextPC) public view returns (bytes32) {
+  function stepNextPC(bytes32 stateHash, uint32 pc, uint64 nextPC) internal view returns (bytes32) {
     uint32 insn = m.ReadMemory(stateHash, pc);
     uint32 opcode = insn >> 26; // 6-bits
     uint32 func = insn & 0x3f; // 6-bits
@@ -264,8 +264,8 @@ contract MIPS {
       if (func == 0x00) { return rt << shamt;      // sll
       } else if (func == 0x02) { return rt >> shamt;      // srl
       } else if (func == 0x03) { return SE(rt >> shamt, 32-shamt);      // sra
-      } else if (func == 0x04) { return rt << rs;         // sllv
-      } else if (func == 0x06) { return rt >> rs;         // srlv
+      } else if (func == 0x04) { return rt << (rs&0x1F);         // sllv
+      } else if (func == 0x06) { return rt >> (rs&0x1F);         // srlv
       } else if (func == 0x07) { return SE(rt >> rs, 32-rs);     // srav
       } else if (func >= 0x08 && func < 0x20) { return rs;  // jr/jalr/div + others
       // 0x10-0x13 = mfhi, mthi, mflo, mtlo

mipsevm/evm.sh

 #!/bin/bash -e
-(cd ../ && npx hardhat compile) && go build && ./mipsevm $1
+(cd ../ && npx hardhat compile > /dev/null)
+go build && ./mipsevm $1

mipsevm/main.go

@@ -126,7 +126,10 @@ func opStaticCall(pc *uint64, interpreter *vm.EVMInterpreter, scope *vm.ScopeCon
 			fmt.Println("HOOKED READ!   ", fmt.Sprintf("%x = %x", addr, nret))
 		}
 		if addr == 0xc0000080 && debug >= 1 {
-			fmt.Printf("%7d %8X %08X\n", pcCount, nret, ram[nret])
+			fmt.Printf("%7d %8X %08X : %08X %08X %08X %08X %08X %08X %08X %08X\n",
+				pcCount, nret, ram[nret],
+				ram[0xc0000008], ram[0xc000000c], ram[0xc0000010], ram[0xc0000014],
+				ram[0xc0000018], ram[0xc000001c], ram[0xc0000020], ram[0xc0000024])
 			pcCount += 1
 		}
 		scope.Memory.Set(retOffset.Uint64(), retSize.Uint64(), ret)
@@ -158,7 +161,7 @@ func runMinigeth(fn string, interpreter *vm.EVMInterpreter, bytecode []byte) {
 			uint32(dat[i+3])<<0
 	}
 
-	steps := 100000
+	steps := 10000
 	gas := 10000 * uint64(steps)
 
 	// 0xdb7df598
@@ -216,7 +219,7 @@ func runTest(fn string, steps int, interpreter *vm.EVMInterpreter, bytecode []by
 }
 
 func main() {
-	fmt.Println("hello")
+	//fmt.Println("hello")
 
 	/*var parent types.Header
 	database := state.NewDatabase(parent)

risc/simple.py

@@ -3,9 +3,12 @@ import os
 import sys
 import binascii
 import struct
+from termcolor import colored
 from unicorn import *
 from unicorn.mips_const import *
 mu = Uc(UC_ARCH_MIPS, UC_MODE_32 + UC_MODE_BIG_ENDIAN)
+from capstone import *
+md = Cs(CS_ARCH_MIPS, CS_MODE_32 + CS_MODE_BIG_ENDIAN)
 
 # heap (256 MB) @ 0x20000000
 heap_start = 0x20000000 # 0x20000000-0x30000000
@@ -80,24 +83,47 @@ def hook_mem_invalid(uc, access, address, size, value, user_data):
   return False
 mu.hook_add(UC_HOOK_MEM_FETCH_UNMAPPED, hook_mem_invalid)
 
+gt = open("/tmp/gethtrace").read().split("\n")
+
 # tracer
 STEP_COUNT = 10000
 step = 0
+is_bds = False
 def hook_code_simple(uc, address, size, user_data):
-  global step
+  global step, is_bds
+  if is_bds:
+    is_bds = False
+    return
   pc = uc.reg_read(UC_MIPS_REG_PC)
   assert address == pc
   assert size == 4
+
+  # check for BDS
+  dat = next(md.disasm(uc.mem_read(address, size), address))
+  if dat.insn_name() in ['jr', 'j', 'beqz', 'jal', 'bnez', 'b']:
+    is_bds = True
+
   inst = struct.unpack(">I", uc.mem_read(pc, 4))[0]
   regs = []
-  for i in range(2,10):
+  # starting at V0
+  for i in range(4,12):
     regs.append(uc.reg_read(i))
 
   rr = ' '.join(["%08X" % x for x in regs])
-  print("%7d %8X %08X : " % (step, pc, inst) + rr)
+  ss = "%7d %8X %08X : " % (step, pc, inst) + rr
+  if ss != gt[step]:
+    print(colored(ss, 'green'))
+    print(colored(gt[step], 'red'))
+    os._exit(0)
+  else:
+    print(ss)
+  print(dat)
+
   step += 1
-  if step > STEP_COUNT:
+  if step >= STEP_COUNT:
     os._exit(0)
+
 mu.hook_add(UC_HOOK_CODE, hook_code_simple)
 
+
 mu.emu_start(0, -1)