Re: [PATCH 06/16] x86/boot: Setup memory protection for bzImage code

[Andrew Cooper]

On 20/10/2022 14:30, Evgeniy Baskov wrote:
> On 2022-10-19 10:57, Andrew Cooper wrote:
>> On 06/09/2022 11:41, Evgeniy Baskov wrote:
>>> diff --git a/arch/x86/boot/compressed/head_64.S
>>> b/arch/x86/boot/compressed/head_64.S
>>> index 5273367283b7..889ca7176aa7 100644
>>> --- a/arch/x86/boot/compressed/head_64.S
>>> +++ b/arch/x86/boot/compressed/head_64.S
>>> @@ -602,6 +603,28 @@ SYM_FUNC_START_LOCAL_NOALIGN(.Lrelocated)
>>>      jmp    *%rax
>>>  SYM_FUNC_END(.Lrelocated)
>>>
>>> +SYM_FUNC_START_LOCAL_NOALIGN(startup32_enable_nx_if_supported)
>>> +    pushq    %rbx
>>> +
>>> +    leaq    has_nx(%rip), %rcx
>>> +
>>> +    mov    $0x80000001, %eax
>>> +    cpuid
>>> +    btl    $20, %edx
>>
>> btl $(X86_FEATURE_NX & 31), %edx
>>
>> But also need to check for the availability of the extended leaf in the
>> first place.
>
> Yes, thank you for suggestion, that looks more readable. I will
> also add the leaf node check. Is there any processor though that
> supports long mode and does not support 0x80000001 leaf node?

No, good point.  The Long Mode feature bit is in this leaf too.

~Andrew