id = 1374
title = "x86 BZHI semantic bug"
state = "closed"
created_at = "2022-12-16T07:33:54.303Z"
closed_at = "2023-02-28T15:08:49.405Z"
labels = ["Closed::Fixed", "accel: TCG", "target: i386"]
url = "https://gitlab.com/qemu-project/qemu/-/issues/1374"
host-os = "Windows 10 20H2"
host-arch = "x86"
qemu-version = "7.1.90 (v7.2.0-rc0)"
guest-os = "None"
guest-arch = "x86"
description = """The result of instruction BZHI is different from the CPU. The value of destination register and SF of EFLAGS are different."""
reproduce = """1. Compile this code
```
void main() {
    asm("mov rax, 0xb1aa9da2fe33fe3");
    asm("mov rbx, 0x80000000ffffffff");
    asm("mov rcx, 0xf3fce8829b99a5c6");
    asm("bzhi rax, rbx, rcx");
}
```
2. Execute and compare the result with the CPU.
    - CPU
        - RAX = 0x0x80000000ffffffff
        - SF = 1
    - QEMU
        - RAX = 0xffffffff
        - SF = 0"""
additional = """This bug is discovered by research conducted by KAIST SoftSec."""