From: Kees Cook <keescook@chromium.org>
To: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Florian Weimer <fweimer@redhat.com>,
linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
linux-api@vger.kernel.org, x86@kernel.org
Subject: Re: [PATCH v2] ELF: supply userspace with available page shifts (AT_PAGE_SHIFT_MASK)
Date: Fri, 8 Dec 2023 10:29:25 -0800 [thread overview]
Message-ID: <202312081027.BA44B7B3@keescook> (raw)
In-Reply-To: <4f5f29d4-9c50-453c-8ad3-03a92fed192e@p183>
On Thu, Dec 07, 2023 at 05:57:05PM +0300, Alexey Dobriyan wrote:
> On Wed, Dec 06, 2023 at 12:47:27PM -0800, Kees Cook wrote:
> > Can't we have a generic ARCH_AT_PAGE_SHIFT_MASK too? Something like:
> >
> > #ifndef ARCH_AT_PAGE_SHIFT_MASK
> > #define ARCH_AT_PAGE_SHIFT_MASK
> > NEW_AUX_ENT(AT_PAGE_SHIFT_MASK, 1 << PAGE_SHIFT)
> > #endif
> >
> > Or am I misunderstanding something here?
>
> 1) Arch maintainers can opt into this new way to report information at
> their own pace.
>
> 2) AT_PAGE_SHIFT_MASK is about _all_ pagesizes supported by CPU.
> Reporting just one is missing the point.
>
> I'll clarify comment: mmap() support require many things including
> tests for hugetlbfs being mounted, this is about CPU support.
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.
--
Kees Cook
next prev parent reply other threads:[~2023-12-08 18:29 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-12-04 17:18 [PATCH] ELF: supply userspace with available page shifts (AT_PAGE_SHIFT_LIST) Alexey Dobriyan
2023-12-05 9:51 ` Florian Weimer
2023-12-05 14:26 ` Alexey Dobriyan
2023-12-05 16:01 ` [PATCH v2] ELF: supply userspace with available page shifts (AT_PAGE_SHIFT_MASK) Alexey Dobriyan
2023-12-06 20:47 ` Kees Cook
2023-12-06 21:05 ` Florian Weimer
2023-12-06 21:09 ` Kees Cook
2023-12-07 15:04 ` Alexey Dobriyan
2023-12-07 14:57 ` Alexey Dobriyan
2023-12-07 15:32 ` Florian Weimer
2023-12-08 18:29 ` Kees Cook [this message]
2023-12-08 18:35 ` Florian Weimer
2023-12-08 18:38 ` Kees Cook
2023-12-09 9:44 ` Alexey Dobriyan
2023-12-07 18:44 ` [PATCH v3] ELF: AT_PAGE_SHIFT_MASK -- supply userspace with available page shifts Alexey Dobriyan
2023-12-12 21:09 ` Kees Cook
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