Re: the x86 sysret_rip test fails on the Intel FRED architecture

H. Peter Anvin
2023-01-24T00:01:00Z

On 1/23/23 15:43, Ammar Faizi wrote:
>
> Align them to spot differences:
>
> 0x200893 = 0b1000000000100010010011
> 0x200a93 = 0b1000000000101010010011
> ^
>
> Or just xor them to find the differences:
>
> (gdb) p/x 0x200893 ^ 0x200a93
> $3 = 0x200
>
> ** Checks my Intel SDM cheat sheets. **
>
> Then, I was like "Oh, that's (1 << 9) a.k.a. IF. Of course we can't
> change rflags[IF] from userspace!!!".
>
> In short, we can't use 0x200893 as the rflags_sentinel value because it
> clears the interrupt flag.
>

Right, my mistake.

-hpa