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hypervisor: x86: emulator: accept empty instruction stream input

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The emulator should fetch from memory just fine.

Signed-off-by: Wei Liu <liuwe@microsoft.com>
This commit is contained in:
Wei Liu 2024-06-27 22:38:55 +00:00 committed by Bo Chen
parent 3ad8d24943
commit 7c608f6380
1 changed files with 64 additions and 3 deletions
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67
hypervisor/src/arch/x86/emulator/mod.rs
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@ -561,7 +561,7 @@ impl<'a, T: CpuStateManager> Emulator<'a, T> {
decoder.set_ip(state.ip());
while decoder.can_decode() && !stop_emulation {
while !stop_emulation {
decoder.decode_out(&mut insn);
if decoder.last_error() == DecoderError::NoMoreBytes {
@ -595,8 +595,6 @@ impl<'a, T: CpuStateManager> Emulator<'a, T> {
insn_format!(insn)
)));
}
stop_emulation = true;
}
// Emulate the decoded instruction
@ -771,6 +769,69 @@ mod tests {
use super::*;
use crate::arch::x86::emulator::mock_vmm::*;
#[test]
// Emulate executing an empty stream. Instructions should be fetched from
// memory.
//
// mov rax, 0x1000
// mov rbx, qword ptr [rax+10h]
fn test_empty_instruction_stream() {
let target_rax: u64 = 0x1000;
let target_rbx: u64 = 0x1234567812345678;
let ip: u64 = 0x1000;
let cpu_id = 0;
let memory = [
// Code at IP
0x48, 0xc7, 0xc0, 0x00, 0x10, 0x00, 0x00, // mov rax, 0x1000
0x48, 0x8b, 0x58, 0x10, // mov rbx, qword ptr [rax+10h]
// Padding
0x00, 0x00, 0x00, 0x00, 0x00, // Padding is all zeroes
// Data at IP + 0x10 (0x1234567812345678 in LE)
0x78, 0x56, 0x34, 0x12, 0x78, 0x56, 0x34, 0x12,
];
let mut vmm = MockVmm::new(ip, vec![], Some((ip, &memory)));
assert!(vmm.emulate_insn(cpu_id, &[], Some(2)).is_ok());
let rax: u64 = vmm
.cpu_state(cpu_id)
.unwrap()
.read_reg(Register::RAX)
.unwrap();
assert_eq!(rax, target_rax);
let rbx: u64 = vmm
.cpu_state(cpu_id)
.unwrap()
.read_reg(Register::RBX)
.unwrap();
assert_eq!(rbx, target_rbx);
}
#[test]
// Emulate executing an empty stream. Instructions should be fetched from
// memory. The emulation should abort.
//
// mov rax, 0x1000
// mov rbx, qword ptr [rax+10h]
// ... garbage ...
fn test_empty_instruction_stream_bad() {
let ip: u64 = 0x1000;
let cpu_id = 0;
let memory = [
// Code at IP
0x48, 0xc7, 0xc0, 0x00, 0x10, 0x00, 0x00, // mov rax, 0x1000
0x48, 0x8b, 0x58, 0x10, // mov rbx, qword ptr [rax+10h]
// Padding
0xff, 0xff, 0xff, 0xff, 0xff, // Garbage
// Data at IP + 0x10 (0x1234567812345678 in LE)
0x78, 0x56, 0x34, 0x12, 0x78, 0x56, 0x34, 0x12,
];
let mut vmm = MockVmm::new(ip, vec![], Some((ip, &memory)));
assert!(vmm.emulate_insn(cpu_id, &[], None).is_err());
}
#[test]
// Emulate truncated instruction stream, which should cause a fetch.
//