Re: [PATCH v2] ELF: supply userspace with available page shifts (AT_PAGE_SHIFT_MASK)

Kees Cook
2023-12-08T18:38:08Z

On Fri, Dec 08, 2023 at 07:35:25PM +0100, Florian Weimer wrote:
> * Kees Cook:
>
> > I significantly prefer APIs not being arch-specific, so I'd prefer we
> > always include AT_PAGE_SHIFT_MASK. For an architecture that doesn't
> > define its own ARCH_AT_PAGE_SHIFT_MASK, it's not _inaccurate_ to report
> > 1 << PAGE_SHIFT, but it might be incomplete.
>
> The downside is that as an application programmer, I have to go and
> chase for the information the legacy way if I encounter
> getauxval(AT_PAGE_SHIFT_MASK) == getpagesize() for a longer time
> because the interface does not signal the absence of any extended
> page sizes.

Are there architectures besides x86 where AT_PAGE_SHIFT_MASK isn't a
single bit? If so, let's get them added now along with x86.

--
Kees Cook