linux-kernel - Re: [PATCH 2/7] arm64: Implement copy_thread

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Date:   Tue, 7 Jan 2020 20:30:03 +0100
From:   Christian Brauner <christian.brauner@...ntu.com>
To:     Will Deacon <will@...nel.org>
Cc:     Amanieu d'Antras <amanieu@...il.com>,
        Will Deacon <will.deacon@....com>,
        linux-kernel@...r.kernel.org,
        Christian Brauner <christian@...uner.io>,
        "# 3.4.x" <stable@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        keescook@...omium.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH 2/7] arm64: Implement copy_thread_tls

On Tue, Jan 07, 2020 at 05:45:09PM +0000, Will Deacon wrote:
> On Tue, Jan 07, 2020 at 10:02:27AM +0100, Christian Brauner wrote:
> > [Cc Kees in case he knows something about where arch specific tests live
> >  or whether we have a framework for this]
> > 
> > On Mon, Jan 06, 2020 at 07:03:32PM +0100, Amanieu d'Antras wrote:
> > > On Mon, Jan 6, 2020 at 6:39 PM Will Deacon <will@...nel.org> wrote:
> > > > I also ran the native and compat selftests but, unfortunately, they all
> > > > pass even without this patch. Do you reckon it would be possible to update
> > > > them to check the tls pointer?
> > > 
> > > Here's the program I used for testing on arm64. I considered adding it
> > > to the selftests but there is no portable way of reading the TLS
> > > register on all architectures.
> > 
> > I'm not saying you need to do this right now.
> 
> Agreed, these patches should be merged in their current state and my ack
> stands for that.

Oh yeah, that's how I took your Ack.
Thanks! :)

> 
> > It feels like we must've run into the "this is architecture
> > specific"-and-we-want-to-test-this issue before... Do we have a place
> > where architecture specific selftests live?
> 
> For arch-specific selftests there are tools/testing/selftests/$ARCH
> directories, although in this case maybe it's better to have an #ifdef
> in a header so that architectures with __builtin_thread_pointer can use
> that.

Yeah, I think the #ifdef approach might make the most sense.

Christian