[PATCH 3/3] mm: Care about shadow stack guard gap when getting an unmapped area

[Deepak Gupta]

On Tue, Sep 03, 2024 at 08:57:20PM +0100, Mark Brown wrote:
>On Tue, Sep 03, 2024 at 03:41:49PM -0400, Liam R. Howlett wrote:
>> * Mark Brown <broonie at kernel.org> [240902 15:09]:
>
>> > +static inline unsigned long stack_guard_placement(vm_flags_t vm_flags)
>> > +{
>> > +	if (vm_flags & VM_SHADOW_STACK)
>> > +		return PAGE_SIZE;
>
>> Is PAGE_SIZE is enough?
>
>It's what x86 currently uses so it'll be no worse off if it gets moved
>to the generic code (there's a comment in the arch code explaing what's
>needed there) and it's enough for arm64, we only do single record
>pushes/pops or (optionally) writes to unconstrained addresses.

It's enough for RISC-V too.