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

H. Peter Anvin
2023-01-24T00:03:50Z

On 1/23/23 15:53, Andrew Cooper wrote:
>>
>> A simple workaround is: just compile it with "-mno-red-zone" flag.
>
> You can't compile userspace like that, unless you recompile and
> statically link everything including libc.
>
> The proper way to fix this is to add a "+r" constraint on the stack
> pointer, at which point the compiler will arrange for nothing in the
> redzone to be live around the asm block.
>

So you are of course right that that is The Right Way[TM] to fix this.

However, to be picky: since the redzone is not in use across function
calls, it is perfectly legitimate to inhibit the redzone for one
function only.

-hpa