Re: [PATCH v21 1/2] signal: define the SA_EXPOSE_TAGBITS bit in sa_flags

From: ebiederm@xmission.com (Eric W. Biederman)
To: Catalin Marinas <catalin.marinas@arm.com>
Cc: Peter Collingbourne <pcc@google.com>,
	Helge Deller <deller@gmx.de>,
	Kevin Brodsky <kevin.brodsky@arm.com>,
	Oleg Nesterov <oleg@redhat.com>,
	linux-api@vger.kernel.org,
	"James E.J. Bottomley" <James.Bottomley@hansenpartnership.com>,
	Kostya Serebryany <kcc@google.com>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	Andrey Konovalov <andreyknvl@google.com>,
	David Spickett <david.spickett@linaro.org>,
	Vincenzo Frascino <vincenzo.frascino@arm.com>,
	Will Deacon <will@kernel.org>, Dave Martin <Dave.Martin@arm.com>,
	Evgenii Stepanov <eugenis@google.com>
Subject: Re: [PATCH v21 1/2] signal: define the SA_EXPOSE_TAGBITS bit in sa_flags
Date: Mon, 23 Nov 2020 09:53:13 -0600	[thread overview]
Message-ID: <87y2isysra.fsf@x220.int.ebiederm.org> (raw)
In-Reply-To: <20201123114935.GD17833@gaia> (Catalin Marinas's message of "Mon,  23 Nov 2020 11:49:36 +0000")

Catalin Marinas <catalin.marinas@arm.com> writes:

> On Fri, Nov 20, 2020 at 05:22:58PM -0600, Eric W. Biederman wrote:
>> Peter Collingbourne <pcc@google.com> writes:
>> 
>> > Architectures that support address tagging, such as arm64, may want to
>> > expose fault address tag bits to the signal handler to help diagnose
>> > memory errors. However, these bits have not been previously set,
>> > and their presence may confuse unaware user applications. Therefore,
>> > introduce a SA_EXPOSE_TAGBITS flag bit in sa_flags that a signal
>> > handler may use to explicitly request that the bits are set.
>> >
>> > The generic signal handler APIs expect to receive tagged addresses.
>> > Architectures may specify how to untag addresses in the case where
>> > SA_EXPOSE_TAGBITS is clear by defining the arch_untagged_si_addr
>> > function.
>> >
>> > Signed-off-by: Peter Collingbourne <pcc@google.com>
>> > Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
>> > Link: https://linux-review.googlesource.com/id/I16dd0ed2081f091fce97be0190cb8caa874c26cb
>> > ---
>> > To be applied on top of:
>> > https://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace.git signal-for-v5.11
>> 
>> I have merged this first patch into signal-for-v5.11 and pushed
>> everything out to linux-next.
>
> Thank you Eric. Assuming this branch won't be rebased, I'll apply the
> arm64 changes on top (well, if you rebase it, just let me know so that
> we don't end up with duplicate commits in mainline).

No.  I won't be rebasing it.  Not unless something serious problem shows
up, and at that point I will be more likely to apply a corrective change
on top that you can also grab.

Eric

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