From: Catalin Marinas <catalin.marinas@arm.com>
To: Ard Biesheuvel <ardb@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org, maz@kernel.org,
will@kernel.org, mark.rutland@arm.com, anshuman.khandual@arm.com,
qperret@google.com, kernel-team@android.com
Subject: Re: [PATCH 2/2] arm64: mm: use XN table mapping attributes for the linear region
Date: Fri, 5 Mar 2021 19:06:00 +0000 [thread overview]
Message-ID: <20210305190600.GK23855@arm.com> (raw)
In-Reply-To: <20210304171145.12281-3-ardb@kernel.org>
On Thu, Mar 04, 2021 at 06:11:45PM +0100, Ard Biesheuvel wrote:
> The way the arm64 kernel virtual address space is constructed guarantees
> that swapper PGD entries are never shared between the linear region on
> the one hand, and the vmalloc region on the other, which is where all
> kernel text, module text and BPF text mappings reside.
>
> This means that mappings in the linear region (which never require
> executable permissions) never share any table entries at any level with
> mappings that do require executable permissions, and so we can set the
> table-level PXN/UXN attributes for all table entries that are created
> while setting up mappings in the linear region. Since swapper's PGD
> level page table is mapped r/o itself, this adds another layer of
> robustness to the way the kernel manages its own page tables.
In ARMv8.1 the architecture added the possibility of disabling the
hierarchical page table permissions (FEAT_HPDS) so that we can use these
bits for software.
Is there any big advantage to using the hierarchical permissions vs
some sanity check in set_pte() for example?
--
Catalin
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2021-03-05 19:07 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-04 17:11 [PATCH 0/2] arm64: use XN table mappings for the linear region Ard Biesheuvel
2021-03-04 17:11 ` [PATCH 1/2] arm64: mm: add missing P4D definitions and use them consistently Ard Biesheuvel
2021-03-04 17:39 ` Mark Rutland
2021-03-08 9:06 ` Anshuman Khandual
2021-03-08 9:07 ` Ard Biesheuvel
2021-03-04 17:11 ` [PATCH 2/2] arm64: mm: use XN table mapping attributes for the linear region Ard Biesheuvel
2021-03-04 17:39 ` Mark Rutland
2021-03-05 8:13 ` Ard Biesheuvel
2021-03-05 19:06 ` Catalin Marinas [this message]
2021-03-05 19:17 ` Ard Biesheuvel
2021-03-05 20:37 ` Catalin Marinas
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20210305190600.GK23855@arm.com \
--to=catalin.marinas@arm.com \
--cc=anshuman.khandual@arm.com \
--cc=ardb@kernel.org \
--cc=kernel-team@android.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=mark.rutland@arm.com \
--cc=maz@kernel.org \
--cc=qperret@google.com \
--cc=will@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.