id = 1376
title = "x86 LSL and LAR fault"
state = "opened"
created_at = "2022-12-16T07:56:37.974Z"
closed_at = "n/a"
labels = ["accel: TCG", "target: i386"]
url = "https://gitlab.com/qemu-project/qemu/-/issues/1376"
host-os = "Windows 10 20H2"
host-arch = "x86"
qemu-version = "7.1.90 (v7.2.0-rc0)"
guest-os = "None"
guest-arch = "x86"
description = """From the description of LSL and LAR instructions in manual, `If the segment descriptor cannot be accessed or is an invalid type for the instruction, the ZF flag is cleared and no value is loaded in the destination operand.`. When it happens at the CPU, it seems they do nothing (nop). However, in QEMU, it crashes."""
reproduce = """1. Compile this code
```
void main() {
    asm("mov rax, 0xa02e698e741f5a6a");
    asm("mov rbx, 0x20959ddd7a0aef");
    asm("lsl ax, bx");
}
```
2. Execute. QEMU crashes but CPU does not. This problem happens with LAR, too."""
additional = """This bug is discovered by research conducted by KAIST SoftSec."""