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semantic: 0.694
graphic: 0.050
device: 0.049
debug: 0.048
other: 0.028
permissions: 0.024
vnc: 0.021
boot: 0.016
PID: 0.015
performance: 0.014
socket: 0.014
files: 0.013
network: 0.010
KVM: 0.005
semantic: 0.759
debug: 0.145
other: 0.020
files: 0.017
performance: 0.012
PID: 0.009
device: 0.008
network: 0.007
permissions: 0.004
socket: 0.004
KVM: 0.004
graphic: 0.004
boot: 0.004
vnc: 0.003
x86 BEXTR semantic bug
Description of problem
The result of instruction BEXTR is different with from the CPU. The value of destination register is different. I think QEMU does not consider the operand size limit.
Steps to reproduce
Compile this code
void main() {
asm("mov rax, 0x17b3693f77fb6e9");
asm("mov rbx, 0x8f635a775ad3b9b4");
asm("mov rcx, 0xb717b75da9983018");
asm("bextr eax, ebx, ecx");
}
Execute and compare the result with the CPU.
CPU
RAX = 0x5a
QEMU
RAX = 0x635a775a
Additional information
This bug is discovered by research conducted by KAIST SoftSec.
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