From: Dave Martin <Dave.Martin@arm.com>
To: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: linux-arch@vger.kernel.org, linux-doc@vger.kernel.org,
Szabolcs Nagy <szabolcs.nagy@arm.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will.deacon@arm.com>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
Alexander Viro <viro@zeniv.linux.org.uk>,
linux-kselftest@vger.kernel.org,
Andrey Konovalov <andreyknvl@google.com>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v4 1/2] arm64: Define Documentation/arm64/tagged-address-abi.txt
Date: Thu, 13 Jun 2019 12:37:32 +0100 [thread overview]
Message-ID: <20190613113731.GY28398@e103592.cambridge.arm.com> (raw)
In-Reply-To: <141c740a-94c2-2243-b6d1-b44ffee43791@arm.com>
On Thu, Jun 13, 2019 at 11:15:34AM +0100, Vincenzo Frascino wrote:
> Hi Catalin,
>
> On 12/06/2019 16:35, Catalin Marinas wrote:
> > Hi Vincenzo,
> >
> > Some minor comments below but it looks fine to me overall. Cc'ing
> > Szabolcs as well since I'd like a view from the libc people.
> >
>
> Thanks for this, I saw Szabolcs comments.
>
> > On Wed, Jun 12, 2019 at 03:21:10PM +0100, Vincenzo Frascino wrote:
> >> diff --git a/Documentation/arm64/tagged-address-abi.txt b/Documentation/arm64/tagged-address-abi.txt
> >> new file mode 100644
> >> index 000000000000..96e149e2c55c
> >> --- /dev/null
> >> +++ b/Documentation/arm64/tagged-address-abi.txt
[...]
> >> +Since it is not desirable to relax the ABI to allow tagged user addresses
> >> +into the kernel indiscriminately, arm64 provides a new sysctl interface
> >> +(/proc/sys/abi/tagged_addr) that is used to prevent the applications from
> >> +enabling the relaxed ABI and a new prctl() interface that can be used to
> >> +enable or disable the relaxed ABI.
> >> +
> >> +The sysctl is meant also for testing purposes in order to provide a simple
> >> +way for the userspace to verify the return error checking of the prctl()
> >> +command without having to reconfigure the kernel.
> >> +
> >> +The ABI properties are inherited by threads of the same application and
> >> +fork()'ed children but cleared when a new process is spawn (execve()).
> >
> > "spawned".
I'd just say "cleared by execve()."
"Spawn" suggests (v)fork+exec to me (at least, what's what "spawn" means on
certain other OSes).
> >
> > I guess you could drop these three paragraphs here and mention the
> > inheritance properties when introducing the prctl() below. You can also
> > mention the global sysctl switch after the prctl() was introduced.
> >
>
> I will move the last two (rewording them) to the _section_ 2, but I would still
> prefer the Introduction to give an overview of the solution as well.
>
> >> +
> >> +2. ARM64 Tagged Address ABI
> >> +---------------------------
> >> +
> >> +From the kernel syscall interface prospective, we define, for the purposes
> >> +of this document, a "valid tagged pointer" as a pointer that either it has
> >
> > "either has" (no 'it') sounds slightly better but I'm not a native
> > English speaker either.
> >
> >> +a zero value set in the top byte or it has a non-zero value, it is in memory
> >> +ranges privately owned by a userspace process and it is obtained in one of
> >> +the following ways:
> >> + - mmap() done by the process itself, where either:
> >> + * flags = MAP_PRIVATE | MAP_ANONYMOUS
> >> + * flags = MAP_PRIVATE and the file descriptor refers to a regular
> >> + file or "/dev/zero"
> >> + - a mapping below sbrk(0) done by the process itself
> >> + - any memory mapped by the kernel in the process's address space during
> >> + creation and following the restrictions presented above (i.e. data, bss,
> >> + stack).
> >> +
> >> +The ARM64 Tagged Address ABI is an opt-in feature, and an application can
> >> +control it using the following prctl()s:
> >> + - PR_SET_TAGGED_ADDR_CTRL: can be used to enable the Tagged Address ABI.
> >
> > enable or disable (not sure we need the latter but it doesn't heart).
> >
> > I'd add the arg2 description here as well.
> >
>
> Good point I missed this.
>
> >> + - PR_GET_TAGGED_ADDR_CTRL: can be used to check the status of the Tagged
> >> + Address ABI.
For both prctls, you should also document the zeroed arguments up to
arg5 (unless we get rid of the enforcement and just ignore them).
Is there a canonical way to detect whether this whole API/ABI is
available? (i.e., try to call this prctl / check for an HWCAP bit,
etc.)
[...]
Cheers
---Dave
_______________________________________________
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:[~2019-06-13 11:37 UTC|newest]
Thread overview: 78+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-12 11:43 [PATCH v17 00/15] arm64: untag user pointers passed to the kernel Andrey Konovalov
2019-06-12 11:43 ` [PATCH v17 01/15] arm64: untag user pointers in access_ok and __uaccess_mask_ptr Andrey Konovalov
2019-06-12 14:26 ` Vincenzo Frascino
2019-06-12 11:43 ` [PATCH v17 02/15] lib, arm64: untag user pointers in strn*_user Andrey Konovalov
2019-06-12 14:28 ` Vincenzo Frascino
2019-06-12 11:43 ` [PATCH v17 03/15] arm64: Introduce prctl() options to control the tagged user addresses ABI Andrey Konovalov
2019-06-12 14:30 ` Vincenzo Frascino
2019-06-12 14:55 ` Catalin Marinas
2019-06-13 11:02 ` Dave Martin
2019-06-13 15:26 ` Catalin Marinas
2019-06-14 5:13 ` Kees Cook
2019-06-18 9:18 ` Dave Martin
2019-06-13 11:16 ` Dave Martin
2019-06-13 15:35 ` Catalin Marinas
2019-06-13 15:45 ` Vincenzo Frascino
2019-06-13 15:57 ` Catalin Marinas
2019-06-13 16:15 ` Vincenzo Frascino
2019-06-17 13:56 ` Catalin Marinas
2019-06-17 16:56 ` Szabolcs Nagy
2019-06-17 16:57 ` Evgenii Stepanov
2019-06-17 17:18 ` Catalin Marinas
2019-06-17 21:59 ` Evgenii Stepanov
2019-06-19 14:45 ` Andrey Konovalov
2019-06-19 15:29 ` Catalin Marinas
2019-06-12 11:43 ` [PATCH v17 04/15] mm, arm64: untag user pointers passed to memory syscalls Andrey Konovalov
2019-06-12 14:31 ` Vincenzo Frascino
2019-06-19 15:55 ` Khalid Aziz
2019-06-19 16:46 ` Khalid Aziz
2019-06-24 14:22 ` Andrey Konovalov
2019-06-12 11:43 ` [PATCH v17 05/15] mm, arm64: untag user pointers in mm/gup.c Andrey Konovalov
2019-06-12 14:33 ` Vincenzo Frascino
2019-06-19 16:41 ` Khalid Aziz
2019-06-12 11:43 ` [PATCH v17 06/15] mm, arm64: untag user pointers in get_vaddr_frames Andrey Konovalov
2019-06-12 14:34 ` Vincenzo Frascino
2019-06-19 16:48 ` Khalid Aziz
2019-06-12 11:43 ` [PATCH v17 07/15] fs, arm64: untag user pointers in copy_mount_options Andrey Konovalov
2019-06-12 14:35 ` Vincenzo Frascino
2019-06-19 20:01 ` Khalid Aziz
2019-06-12 11:43 ` [PATCH v17 08/15] userfaultfd, arm64: untag user pointers Andrey Konovalov
2019-06-12 14:40 ` Vincenzo Frascino
2019-06-12 11:43 ` [PATCH v17 09/15] drm/amdgpu, " Andrey Konovalov
2019-06-12 11:43 ` [PATCH v17 10/15] drm/radeon, arm64: untag user pointers in radeon_gem_userptr_ioctl Andrey Konovalov
2019-06-12 11:43 ` [PATCH v17 11/15] IB/mlx4, arm64: untag user pointers in mlx4_get_umem_mr Andrey Konovalov
2019-06-12 11:43 ` [PATCH v17 12/15] media/v4l2-core, arm64: untag user pointers in videobuf_dma_contig_user_get Andrey Konovalov
2019-06-19 20:05 ` Khalid Aziz
2019-06-12 11:43 ` [PATCH v17 13/15] tee/shm, arm64: untag user pointers in tee_shm_register Andrey Konovalov
2019-06-12 11:43 ` [PATCH v17 14/15] vfio/type1, arm64: untag user pointers in vaddr_get_pfn Andrey Konovalov
2019-06-12 14:41 ` Vincenzo Frascino
2019-06-12 15:58 ` Auger Eric
2019-06-12 11:43 ` [PATCH v17 15/15] selftests, arm64: add a selftest for passing tagged pointers to kernel Andrey Konovalov
2019-06-12 12:30 ` Szabolcs Nagy
2019-06-12 15:00 ` Catalin Marinas
2019-06-19 14:42 ` Andrey Konovalov
2019-06-12 14:21 ` [PATCH v4 0/2] arm64 relaxed ABI Vincenzo Frascino
2019-06-12 14:21 ` [PATCH v4 1/2] arm64: Define Documentation/arm64/tagged-address-abi.txt Vincenzo Frascino
2019-06-12 15:35 ` Catalin Marinas
2019-06-13 10:15 ` Vincenzo Frascino
2019-06-13 11:37 ` Dave Martin [this message]
2019-06-13 12:28 ` Catalin Marinas
2019-06-13 13:23 ` Dave Martin
2019-06-13 15:39 ` Catalin Marinas
2019-06-12 16:30 ` Szabolcs Nagy
2019-06-13 9:20 ` Catalin Marinas
2019-06-13 10:14 ` Szabolcs Nagy
2019-06-13 11:16 ` Vincenzo Frascino
2019-06-13 12:28 ` Szabolcs Nagy
2019-06-13 14:03 ` Vincenzo Frascino
2019-06-13 15:32 ` Szabolcs Nagy
2019-06-13 15:35 ` Vincenzo Frascino
2019-06-12 14:21 ` [PATCH v4 2/2] arm64: Relax Documentation/arm64/tagged-pointers.txt Vincenzo Frascino
2019-06-12 15:56 ` Catalin Marinas
2019-06-12 16:37 ` Szabolcs Nagy
2019-06-13 15:51 ` [PATCH v5 0/2] arm64 relaxed ABI Vincenzo Frascino
2019-06-13 15:51 ` [PATCH v5 1/2] arm64: Define Documentation/arm64/tagged-address-abi.txt Vincenzo Frascino
2019-06-18 11:02 ` Szabolcs Nagy
2019-06-18 13:13 ` Kevin Brodsky
2019-06-21 15:16 ` Catalin Marinas
2019-06-13 15:51 ` [PATCH v5 2/2] arm64: Relax Documentation/arm64/tagged-pointers.txt Vincenzo Frascino
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=20190613113731.GY28398@e103592.cambridge.arm.com \
--to=dave.martin@arm.com \
--cc=andreyknvl@google.com \
--cc=catalin.marinas@arm.com \
--cc=linux-arch@vger.kernel.org \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-doc@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-kselftest@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=szabolcs.nagy@arm.com \
--cc=vincenzo.frascino@arm.com \
--cc=viro@zeniv.linux.org.uk \
--cc=will.deacon@arm.com \
/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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).