From: Will Deacon <will@kernel.org>
To: Peter Collingbourne <pcc@google.com>
Cc: Dave Martin <Dave.Martin@arm.com>,
Catalin Marinas <catalin.marinas@arm.com>,
linux-arch@vger.kernel.org, libc-alpha@sourceware.org,
Szabolcs Nagy <szabolcs.nagy@arm.com>,
Andrey Konovalov <andreyknvl@google.com>,
Kevin Brodsky <kevin.brodsky@arm.com>,
linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
Vincenzo Frascino <vincenzo.frascino@arm.com>,
Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH v9 29/29] arm64: mte: Add Memory Tagging Extension documentation
Date: Thu, 15 Oct 2020 09:57:59 +0100 [thread overview]
Message-ID: <20201015085759.GA4790@willie-the-truck> (raw)
In-Reply-To: <CAMn1gO76z7eLcuYg_PuWPCq7_N5p29518EGy-FdY9AvyY0fDgw@mail.gmail.com>
On Wed, Oct 14, 2020 at 04:43:23PM -0700, Peter Collingbourne wrote:
> On Fri, Sep 18, 2020 at 1:30 AM Will Deacon <will@kernel.org> wrote:
> > I think so, yes. I'm hoping to queue it for 5.10, once I have an Ack from
> > the Android tools side on the per-thread ABI.
>
> Our main requirement on the Android side is to provide an API for
> changing the tag checking mode in all threads in a process while
> multiple threads are running. I think we've been able to accomplish
> this [1] by using a libc private real-time signal which is sent to all
> threads. The implementation has been tested on FVP via the included
> unit tests. The code has also been tested on real hardware in a
> multi-threaded app process (of course we don't have MTE-enabled
> hardware, so the implementation was tested on hardware by hacking it
> to disable the tagged address ABI instead of changing the tag checking
> mode, and then verifying via ptrace(PTRACE_GETREGSET) that the tagged
> address ABI was disabled in all threads).
>
> That being said, as with any code at the nexus of concurrency and
> POSIX signals, the implementation is quite tricky so I would say it
> falls more into the category of "no obvious problems" than "obviously
> no problems". It also relies on changes to the implementations of
> pthread APIs so it wouldn't catch threads created directly via clone()
> rather than via pthread_create(). I think we would be able to ignore
> such threads on Android without causing compatibility issues because
> we can require the process to not create threads via clone() before
> calling the function. I imagine this may not necessarily work for
> other libcs like glibc, though, but as I understand it glibc has no
> plan to offer such an API.
>
> I feel confident enough in the kernel API though that I think that
> it's reasonable as a starting point at least, and that if a problem
> with the API is discovered I would expect it to be fixable by adding
> new APIs, so:
>
> Acked-by: Peter Collingbourne <pcc@google.com>
Thanks, Peter. This series has already landed upstream, so I'm unable to
add your Ack now, but the text above is very helpful.
Cheers,
Will
> [1] https://android-review.googlesource.com/c/platform/bionic/+/1427377
next prev parent reply other threads:[~2020-10-15 8:58 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20200904103029.32083-1-catalin.marinas@arm.com>
2020-09-04 10:30 ` Catalin Marinas
2020-09-17 8:11 ` Will Deacon
2020-09-17 9:02 ` Catalin Marinas
2020-09-17 16:15 ` Dave Martin
2020-09-18 8:30 ` Will Deacon
2020-10-14 23:43 ` Peter Collingbourne
2020-10-15 8:57 ` Will Deacon [this message]
2020-10-15 11:14 ` Szabolcs Nagy
2020-09-22 16:04 ` Catalin Marinas
2020-09-22 15:52 ` Szabolcs Nagy
2020-09-22 16:55 ` Catalin Marinas
2020-09-23 9:10 ` Szabolcs Nagy
2020-09-22 12:22 ` Andrey Konovalov
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