hypervisor: x86: emulate MOVS instruction

Signed-off-by: Wei Liu <liuwe@microsoft.com>

hypervisor/src/arch/x86/emulator/instructions/mod.rs

@@ -13,6 +13,7 @@ use iced_x86::*;
 
 pub mod cmp;
 pub mod mov;
+pub mod movs;
 
 fn get_op<T: CpuStateManager>(
     insn: &Instruction,

hypervisor/src/arch/x86/emulator/instructions/movs.rs

@@ -0,0 +1,147 @@
+//
+// Copyright © 2021 Microsoft
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+
+#![allow(non_camel_case_types)]
+
+//
+// MOVS - Move Data from String to String
+//
+
+extern crate iced_x86;
+
+use crate::arch::emulator::{EmulationError, PlatformEmulator};
+use crate::arch::x86::emulator::instructions::*;
+use crate::arch::x86::regs::DF;
+use crate::arch::x86::Exception;
+
+pub struct Movsd_m32_m32;
+impl<T: CpuStateManager> InstructionHandler<T> for Movsd_m32_m32 {
+    fn emulate(
+        &self,
+        insn: &Instruction,
+        state: &mut T,
+        platform: &mut dyn PlatformEmulator<CpuState = T>,
+    ) -> Result<(), EmulationError<Exception>> {
+        let mut count: u64 = if insn.has_rep_prefix() {
+            state
+                .read_reg(Register::ECX)
+                .map_err(|e| EmulationError::InvalidOperand(anyhow!(e)))?
+        } else {
+            1
+        };
+
+        let mut rsi = state
+            .read_reg(Register::RSI)
+            .map_err(|e| EmulationError::InvalidOperand(anyhow!(e)))?;
+        let mut rdi = state
+            .read_reg(Register::RDI)
+            .map_err(|e| EmulationError::InvalidOperand(anyhow!(e)))?;
+
+        let df = (state.flags() & DF) != 0;
+        let len = std::mem::size_of::<u32>();
+
+        while count > 0 {
+            let mut memory: [u8; 4] = [0; 4];
+
+            let src = state
+                .linearize(Register::DS, rsi, false)
+                .map_err(|e| EmulationError::InvalidOperand(anyhow!(e)))?;
+            let dst = state
+                .linearize(Register::ES, rdi, true)
+                .map_err(|e| EmulationError::InvalidOperand(anyhow!(e)))?;
+
+            platform
+                .read_memory(src, &mut memory[0..len])
+                .map_err(EmulationError::PlatformEmulationError)?;
+            platform
+                .write_memory(dst, &memory[0..len])
+                .map_err(EmulationError::PlatformEmulationError)?;
+
+            if df {
+                rsi = rsi.wrapping_sub(len as u64);
+                rdi = rdi.wrapping_sub(len as u64);
+            } else {
+                rsi = rsi.wrapping_add(len as u64);
+                rdi = rdi.wrapping_add(len as u64);
+            }
+            count -= 1;
+        }
+
+        state
+            .write_reg(Register::RSI, rsi)
+            .map_err(|e| EmulationError::InvalidOperand(anyhow!(e)))?;
+        state
+            .write_reg(Register::RDI, rdi)
+            .map_err(|e| EmulationError::InvalidOperand(anyhow!(e)))?;
+        if insn.has_rep_prefix() {
+            state
+                .write_reg(Register::ECX, 0)
+                .map_err(|e| EmulationError::InvalidOperand(anyhow!(e)))?;
+        }
+
+        Ok(())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    #![allow(unused_mut)]
+    use super::*;
+    use crate::arch::x86::emulator::mock_vmm::*;
+
+    #[test]
+    fn test_rep_movsd_m32_m32() {
+        let ip: u64 = 0x1000;
+        let memory: [u8; 24] = [
+            0x78, 0x56, 0x34, 0x12, // 0x12345678
+            0xdd, 0xcc, 0xbb, 0xaa, // 0xaabbccdd
+            0xa5, 0x5a, 0xa5, 0x5a, // 0x5aa55aa5
+            0x00, 0x00, 0x00, 0x00, // 0x00000000
+            0x00, 0x00, 0x00, 0x00, // 0x00000000
+            0x00, 0x00, 0x00, 0x00, // 0x00000000
+        ];
+        let insn = [0xf3, 0xa5]; // rep movsd
+        let regs = vec![(Register::ECX, 3), (Register::ESI, 0), (Register::EDI, 0xc)];
+        let mut data = [0u8; 4];
+
+        let mut vmm = MockVMM::new(ip, regs, Some((0, &memory)));
+
+        assert!(vmm.emulate_first_insn(0, &insn).is_ok());
+
+        vmm.read_memory(0xc, &mut data).unwrap();
+        assert_eq!(0x12345678, <u32>::from_le_bytes(data));
+        vmm.read_memory(0xc + 4, &mut data).unwrap();
+        assert_eq!(0xaabbccdd, <u32>::from_le_bytes(data));
+        vmm.read_memory(0xc + 8, &mut data).unwrap();
+        assert_eq!(0x5aa55aa5, <u32>::from_le_bytes(data));
+        // The rest should be default value 0 from MockVMM
+        vmm.read_memory(0xc + 12, &mut data).unwrap();
+        assert_eq!(0x0, <u32>::from_le_bytes(data));
+    }
+
+    #[test]
+    fn test_movsd_m32_m32() {
+        let ip: u64 = 0x1000;
+        let memory: [u8; 4] = [
+            0x78, 0x56, 0x34, 0x12, // 0x12345678
+        ];
+        let insn = [0xa5]; // movsd
+        let regs = vec![(Register::ESI, 0), (Register::EDI, 0x8)];
+        let mut data = [0u8; 4];
+
+        let mut vmm = MockVMM::new(ip, regs, Some((0, &memory)));
+
+        assert!(vmm.emulate_first_insn(0, &insn).is_ok());
+
+        vmm.read_memory(0x8, &mut data).unwrap();
+        assert_eq!(0x12345678, <u32>::from_le_bytes(data));
+        // The rest should be default value 0 from MockVMM
+        vmm.read_memory(0x4, &mut data).unwrap();
+        assert_eq!(0x0, <u32>::from_le_bytes(data));
+        vmm.read_memory(0x8 + 8, &mut data).unwrap();
+        assert_eq!(0x0, <u32>::from_le_bytes(data));
+    }
+}

hypervisor/src/arch/x86/emulator/mod.rs

@@ -524,7 +524,9 @@ impl<'a, T: CpuStateManager> Emulator<'a, T> {
             (mov, Movzx_r32_rm8),
             (mov, Movzx_r64_rm8),
             (mov, Movzx_r32_rm16),
-            (mov, Movzx_r64_rm16)
+            (mov, Movzx_r64_rm16),
+            // MOVS
+            (movs, Movsd_m32_m32)
         );
 
         handler

hypervisor/src/arch/x86/regs.rs

@@ -22,6 +22,7 @@ pub const PF_SHIFT: usize = 2;
 pub const AF_SHIFT: usize = 4;
 pub const ZF_SHIFT: usize = 6;
 pub const SF_SHIFT: usize = 7;
+pub const DF_SHIFT: usize = 10;
 pub const OF_SHIFT: usize = 11;
 
 pub const CF: u64 = 1 << CF_SHIFT;
@@ -29,4 +30,5 @@ pub const PF: u64 = 1 << PF_SHIFT;
 pub const AF: u64 = 1 << AF_SHIFT;
 pub const ZF: u64 = 1 << ZF_SHIFT;
 pub const SF: u64 = 1 << SF_SHIFT;
+pub const DF: u64 = 1 << DF_SHIFT;
 pub const OF: u64 = 1 << OF_SHIFT;