[PATCH 2/5 v16] ARM: Replace string mem* functions for KASan

[Ard Biesheuvel]

On Thu, 12 Nov 2020 at 18:52, Nathan Chancellor
<natechancellor at gmail.com> wrote:
>
> On Thu, Nov 12, 2020 at 04:05:52PM +0100, Ard Biesheuvel wrote:
> > On Thu, 12 Nov 2020 at 14:51, Linus Walleij <linus.walleij at linaro.org> wrote:
> > >
> > > On Tue, Nov 10, 2020 at 1:05 PM Ard Biesheuvel <ardb at kernel.org> wrote:
> > > > On Mon, 9 Nov 2020 at 17:07, Russell King - ARM Linux admin
> > > > <linux at armlinux.org.uk> wrote:
> > > > >
> > > > > On Mon, Nov 09, 2020 at 05:02:09PM +0100, Linus Walleij wrote:
> > > > > > On Fri, Nov 6, 2020 at 4:16 PM Russell King - ARM Linux admin
> > > > > > <linux at armlinux.org.uk> wrote:
> > > > > > > On Fri, Nov 06, 2020 at 02:37:21PM +0100, Linus Walleij wrote:
> > > > > >
> > > > > > > > Aha. So shall we submit this to Russell? I figure that his git will not
> > > > > > > > build *without* the changes from mmotm?
> > > > > > > >
> > > > > > > > That tree isn't using git either is it?
> > > > > > > >
> > > > > > > > Is this one of those cases where we should ask Stephen R
> > > > > > > > to carry this patch on top of -next until the merge window?
> > > > > > >
> > > > > > > Another solution would be to drop 9017/2 ("Enable KASan for ARM")
> > > > > > > until the following merge window, and queue up the non-conflicing
> > > > > > > ARM KASan fixes in my "misc" branch along with the rest of KASan,
> > > > > > > and the conflicting patches along with 9017/2 in the following
> > > > > > > merge window.
> > > > > > >
> > > > > > > That means delaying KASan enablement another three months or so,
> > > > > > > but should result in less headaches about how to avoid build
> > > > > > > breakage with different bits going through different trees.
> > > > > > >
> > > > > > > Comments?
> > > > > >
> > > > > > I suppose I would survive deferring it. Or we could merge the
> > > > > > smaller enablement patch towards the end of the merge
> > > > > > window once the MM changes are in.
> > > > > >
> > > > > > If it is just *one* patch in the MM tree I suppose we could also
> > > > > > just apply that one patch also to the ARM tree, and then this
> > > > > > fixup on top. It does look a bit convoluted in the git history with
> > > > > > two hashes and the same patch twice, but it's what I've done
> > > > > > at times when there was no other choice that doing that or
> > > > > > deferring development. It works as long as the patches are
> > > > > > textually identical: git will cope.
> > > > >
> > > > > I thought there was a problem that if I applied the fix then my tree
> > > > > no longer builds without the changes in -mm?
> > > > >
> > > >
> > > > Indeed. Someone is changing the __alias() wrappers [for no good reason
> > > > afaict] in a way that does not allow for new users of those wrappers
> > > > to come in concurrently.
> > > >
> > > > Hency my suggestion to switch to the raw __attribute__((alias("..")))
> > > > notation for the time being, and switch back to __alias() somewhere
> > > > after v5.11-rc1.
> > > >
> > > > Or we might add this to the file in question
> > > >
> > > > #undef __alias
> > > > #define __alias(symbol) __attribute__((__alias__(symbol)))
> > > >
> > > > and switch to the quoted versions of the identifier. Then we can just
> > > > drop these two lines again later, after v5.11-rc1
> > >
> > > I was under the impression that there was some "post-next"
> > > trick that mmot apply this patch after -next has been merged
> > > so it's solved now?
> > >
> >
> > Yes, it appears that [0] has been picked up, I guess we weren't cc'ed
> > on the version that was sent to akpm [which is fine btw, although a
> > followup reply here that things are all good now would have been
> > appreciated]
> >
> >
> > https://lore.kernel.org/linux-arm-kernel/20201109001712.3384097-1-natechancellor@gmail.com/
>
> Hi Ard,
>
> Odd, you were on the list of people to receive that patch and you acked
> it but it seems that Andrew did not CC you when he actually applied the
> patch:
>
> https://lore.kernel.org/mm-commits/20201110212436.yGYhesom8%25akpm@linux-foundation.org/
>
> My apologies for not following up, we appear to be all good now for the
> time being (aside from the futex issue that I reported earlier).
>

No worries - at least it is fixed now. And KASAN is already shaking
out bugs, so it is great that we finally managed to enable this for
ARM.