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https://github.com/mii443/nel_os.git
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syscall emulation
This commit is contained in:
Masato Imai
1
src/vmm/emulation/mod.rs
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1
src/vmm/emulation/mod.rs
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@ -0,0 +1 @@
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pub mod opcode;
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156
src/vmm/emulation/opcode.rs
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156
src/vmm/emulation/opcode.rs
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@ -0,0 +1,156 @@
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use crate::{
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info,
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vmm::{
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vcpu::VCpu,
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vmcs::{DescriptorType, EntryControls, Granularity, SegmentRights},
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},
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};
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use x86::current::vmx::{vmread, vmwrite};
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use x86::vmx::vmcs;
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const OPCODE_TWO_BYTE_ESCAPE: u8 = 0x0F;
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const OPCODE_GROUP_7: u8 = 0x01;
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const OPCODE_CLAC: u8 = 0xCA;
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const OPCODE_STAC: u8 = 0xCB;
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const OPCODE_SYSCALL: u8 = 0x05;
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const RFLAGS_AC_BIT: u64 = 1 << 18;
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pub fn emulate_opcode(vcpu: &mut VCpu, instruction_bytes: [u8; 16], valid_bytes: u64) -> bool {
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if instruction_bytes[0] != OPCODE_TWO_BYTE_ESCAPE || valid_bytes < 2 {
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return false;
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}
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match instruction_bytes[1] {
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OPCODE_SYSCALL => {
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return emulate_syscall(vcpu);
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}
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_ => {}
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}
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match (instruction_bytes[1], instruction_bytes[2]) {
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(OPCODE_GROUP_7, OPCODE_CLAC) => emulate_clac(vcpu),
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(OPCODE_GROUP_7, OPCODE_STAC) => emulate_stac(vcpu),
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_ => false,
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}
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}
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fn emulate_syscall(vcpu: &mut VCpu) -> bool {
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let current_rip = unsafe { vmread(vmcs::guest::RIP).unwrap() };
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let return_address = current_rip + 2;
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let rflags = unsafe { vmread(vmcs::guest::RFLAGS).unwrap() };
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vcpu.guest_registers.rcx = return_address;
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vcpu.guest_registers.r11 = rflags;
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let lstar = vcpu.guest_msr.find(0xc0000082).unwrap().data;
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let star = vcpu.guest_msr.find(0xc0000081).unwrap().data;
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let sfmask = vcpu.guest_msr.find(0xc0000084).unwrap().data;
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let cs_selector = (star >> 32) as u16;
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let ss_selector = cs_selector + 8;
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let cs_rights = {
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let mut rights = SegmentRights::default();
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rights.set_rw(true);
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rights.set_dc(false);
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rights.set_executable(true);
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rights.set_desc_type_raw(DescriptorType::Code as u8);
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rights.set_dpl(0);
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rights.set_granularity_raw(Granularity::KByte as u8);
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rights.set_long(true);
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rights.set_db(false);
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rights
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};
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let ss_rights = {
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let mut rights = SegmentRights::default();
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rights.set_rw(true);
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rights.set_dc(false);
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rights.set_executable(false);
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rights.set_desc_type_raw(DescriptorType::Code as u8);
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rights.set_dpl(0);
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rights.set_granularity_raw(Granularity::KByte as u8);
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rights.set_long(false);
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rights.set_db(true);
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rights
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};
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info!("Setting RIP:{:x} to {:x}", current_rip, lstar);
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unsafe {
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// Set segment registers for kernel mode
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vmwrite(vmcs::guest::RIP, lstar).unwrap();
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vmwrite(vmcs::guest::CS_SELECTOR, cs_selector as u64).unwrap();
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vmwrite(vmcs::guest::SS_SELECTOR, ss_selector as u64).unwrap();
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vmwrite(vmcs::guest::CS_BASE, 0).unwrap();
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vmwrite(vmcs::guest::SS_BASE, 0).unwrap();
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vmwrite(vmcs::guest::CS_LIMIT, 0xFFFFFFFF).unwrap();
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vmwrite(vmcs::guest::SS_LIMIT, 0xFFFFFFFF).unwrap();
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vmwrite(vmcs::guest::CS_ACCESS_RIGHTS, cs_rights.0 as u64).unwrap();
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vmwrite(vmcs::guest::SS_ACCESS_RIGHTS, ss_rights.0 as u64).unwrap();
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// Set CR0 and CR4 for Long Mode
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let mut cr0 = vmread(vmcs::guest::CR0).unwrap();
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cr0 |= (1 << 31) | (1 << 0); // Set PG (Paging) and PE (Protection Enable)
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vmwrite(vmcs::guest::CR0, cr0).unwrap();
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let mut cr4 = vmread(vmcs::guest::CR4).unwrap();
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cr4 |= 1 << 5; // Set PAE (Physical Address Extension)
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vmwrite(vmcs::guest::CR4, cr4).unwrap();
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// Set EFER for Long Mode
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let mut efer = vmread(vmcs::guest::IA32_EFER_FULL).unwrap();
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efer |= (1 << 8) | (1 << 10); // Set LME (Long Mode Enable) and LMA (Long Mode Active)
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vmwrite(vmcs::guest::IA32_EFER_FULL, efer).unwrap();
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// Set VM-Entry controls for Long Mode
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let mut entry_ctrls = EntryControls::read();
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entry_ctrls.set_ia32e_mode_guest(true);
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entry_ctrls.write();
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}
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let new_rflags = rflags & !sfmask;
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unsafe {
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vmwrite(vmcs::guest::RFLAGS, new_rflags).unwrap();
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}
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return true;
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}
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fn emulate_clac(vcpu: &mut VCpu) -> bool {
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if let Err(_) = modify_rflags_ac(false) {
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return false;
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}
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if let Err(_) = vcpu.step_next_inst() {
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return false;
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}
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true
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}
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fn emulate_stac(vcpu: &mut VCpu) -> bool {
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if let Err(_) = modify_rflags_ac(true) {
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return false;
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}
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if let Err(_) = vcpu.step_next_inst() {
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return false;
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}
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true
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}
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fn modify_rflags_ac(set: bool) -> x86::vmx::Result<()> {
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unsafe {
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let rflags = vmread(vmcs::guest::RFLAGS)?;
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let new_rflags = if set {
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rflags | RFLAGS_AC_BIT
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} else {
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rflags & !RFLAGS_AC_BIT
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};
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vmwrite(vmcs::guest::RFLAGS, new_rflags)?;
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}
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Ok(())
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}
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@ -1,6 +1,7 @@
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pub mod asm;
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pub mod cpuid;
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pub mod cr;
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pub mod emulation;
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pub mod ept;
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pub mod error;
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pub mod fpu;
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@ -26,7 +26,9 @@ use crate::{
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memory::BootInfoFrameAllocator,
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subscribe_with_context,
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vmm::{
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cpuid, cr, fpu,
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cpuid, cr,
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emulation::opcode::emulate_opcode,
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fpu,
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io::{self, InitPhase, Serial, PIC},
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msr,
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qual::{QualCr, QualIo},
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@ -975,7 +977,7 @@ impl VCpu {
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vmwrite(vmcs::host::RSP, rsp).unwrap();
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}
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fn step_next_inst(&mut self) -> Result<(), VmFail> {
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pub fn step_next_inst(&mut self) -> Result<(), VmFail> {
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unsafe {
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let rip = vmread(vmcs::guest::RIP)?;
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vmwrite(
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@ -1158,60 +1160,12 @@ impl VCpu {
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}
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if valid_bytes > 0 {
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match instruction_bytes[0] {
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0x0F => {
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if valid_bytes > 1 {
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match instruction_bytes[1] {
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0x01 => match instruction_bytes[2] {
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0xCA => {
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unsafe {
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let rflags =
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vmread(vmcs::guest::RFLAGS).unwrap();
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vmwrite(
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vmcs::guest::RFLAGS,
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rflags & !(1 << 18),
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)
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.unwrap();
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}
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self.step_next_inst().unwrap();
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}
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0xCB => {
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unsafe {
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let rflags =
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vmread(vmcs::guest::RFLAGS).unwrap();
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vmwrite(
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vmcs::guest::RFLAGS,
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rflags | (1 << 18),
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)
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.unwrap();
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}
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self.step_next_inst().unwrap();
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}
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_ => {
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info!(
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"VMExit: Exception {} at RIP {:#x} with instruction bytes: {:?}",
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vector, rip, &instruction_bytes
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);
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self.inject_exception(vector, error_code).unwrap();
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}
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},
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_ => {
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info!(
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"VMExit: Exception {} at RIP {:#x} with instruction bytes: {:?}",
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vector, rip, &instruction_bytes
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);
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self.inject_exception(vector, error_code).unwrap();
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}
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}
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}
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}
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_ => {
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info!(
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"VMExit: Exception {} at RIP {:#x} with instruction bytes: {:?}",
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vector, rip, &instruction_bytes
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);
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self.inject_exception(vector, error_code).unwrap();
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}
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if !emulate_opcode(self, instruction_bytes, valid_bytes) {
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info!(
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"VMExit: Exception {} at RIP {:#x} with instruction bytes: {:?}",
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vector, rip, instruction_bytes
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);
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self.inject_exception(vector, error_code).unwrap();
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}
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}
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}
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