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

[Mark Brown]

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.
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