Re: [PATCH RFC/RFT v2 2/2] kernel: converge common shadow stack flow agnostic to arch

[Deepak Gupta <debug@rivosinc.com>]

On Fri, Nov 01, 2024 at 10:39:15PM +0000, Mark Brown wrote:
>On Fri, Nov 01, 2024 at 09:50:27PM +0000, Edgecombe, Rick P wrote:
>> On Wed, 2024-10-16 at 14:57 -0700, Deepak Gupta wrote:
>
>> > - * The maximum distance INCSSP can move the SSP is 2040 bytes, before
>> > - * it would read the memory. Therefore a single page gap will be enough
>> > - * to prevent any operation from shifting the SSP to an adjacent stack,
>> > - * since it would have to land in the gap at least once, causing a
>> > - * fault.
>
>> I want to take a deeper look at this series once I can apply and test it, but
>> can we maybe make this comment more generic and keep it? I think it is similar
>> reasoning for arm (?), is there anything situation like this for risc-v? Or
>> rather, why does risc-v have the guard gaps?
>
>Yes, for arm64 you can only move the pointer in single frames so a
>single page is enough.

Yeah on risc-v as well guard gap is expected and single page is enough.

I removed this comment from here because of x86 specifics. I can make it
generic, do you think it belongs here or the place where we define
VM_SHADOW_STACK?