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

From: Catalin Marinas <catalin.marinas@arm.com>
To: "Eric W. Biederman" <ebiederm@xmission.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 16:23:30 +0000	[thread overview]
Message-ID: <20201123162329.GB2438@gaia> (raw)
In-Reply-To: <87sg90xd2n.fsf@x220.int.ebiederm.org>

On Mon, Nov 23, 2020 at 10:17:20AM -0600, Eric W. Biederman wrote:
> Catalin Marinas <catalin.marinas@arm.com> writes:
> > On Mon, Nov 23, 2020 at 09:53:13AM -0600, Eric W. Biederman wrote:
> >> 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.
> >
> > Thanks Eric. During the merging window, I'll probably wait for you to
> > send the pull request first just to keep the arm64 diffstat simpler.
> >
> > BTW, did you mean to base them on v5.10-rc3-391-g9cfd9c45994b or just
> > v5.10-rc3? It doesn't matter much as I'll generate the diffstat manually
> > anyway in my pull request as I have different bases in other branches.
> 
> Crap.  How did that happen?  I thought for certain I had based them on
> v5.10-rc3.  Some random git commit is not a good base.  I think the
> better part of valor is to just admit I goofed and not rebase even now.
> 
> It it would make your life easier I will be happy to rebase (onto
> v5.10-rc3?).  I just wanted to get these into my tree so that we could
> incremetnally commit to the changes that makes sense and be certain not
> to loose them.

Please rebase onto -rc3 if there's not much hassle.

Thanks.

-- 
Catalin

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