x86 ADOX and ADCX semantic bug
Description of problem
The result of instruction ADOX and ADCX are different from the CPU. The value of one of EFLAGS is different.

Steps to reproduce

Compile this code


void main() {
    asm("push 512; popfq;");
    asm("mov rax, 0xffffffff84fdbf24");
    asm("mov rbx, 0xb197d26043bec15d");
    asm("adox eax, ebx");
}



Execute and compare the result with the CPU. This problem happens with ADCX, too (with CF).

CPU

OF = 0


QEMU

OF = 1






Additional information
This bug is discovered by research conducted by KAIST SoftSec.