Re: [PATCH v4] ELF: AT_PAGE_SHIFT_MASK -- supply userspace with available page shifts

[Alexey Dobriyan]

On Mon, Feb 05, 2024 at 04:48:08AM -0800, Kees Cook wrote:
> On Mon, Feb 05, 2024 at 12:51:43PM +0300, Alexey Dobriyan wrote:
> > +#define ARCH_AT_PAGE_SHIFT_MASK					\
> > +	do {							\
> > +		u32 val = 1 << 12;				\
> > +		if (boot_cpu_has(X86_FEATURE_PSE)) {		\
> > +			val |= 1 << 21;				\
> > +		}						\
> > +		if (boot_cpu_has(X86_FEATURE_GBPAGES)) {	\
> > +			val |= 1 << 30;				\
> > +		}						\
> 
> Can we use something besides literal "12", "21", and "30" values here?

Ehh, no, why? Inside x86_64 the page shifts are very specific numbers,
they won't change.