linux-kernel - Re: [PATCH 7/7] clone3: ensure copy_thread

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Message-ID: <20200102180901.tgtl7wxtq434h5ny@wittgenstein>
Date:   Thu, 2 Jan 2020 19:09:02 +0100
From:   Christian Brauner <christian.brauner@...ntu.com>
To:     Amanieu d'Antras <amanieu@...il.com>
Cc:     linux-kernel@...r.kernel.org,
        Christian Brauner <christian@...uner.io>,
        stable@...r.kernel.org
Subject: Re: [PATCH 7/7] clone3: ensure copy_thread_tls is implemented

On Thu, Jan 02, 2020 at 06:24:13PM +0100, Amanieu d'Antras wrote:
> copy_thread implementations handle CLONE_SETTLS by reading the TLS
> value from the registers containing the syscall arguments for
> clone. This doesn't work with clone3 since the TLS value is passed
> in clone_args instead.
> 
> Signed-off-by: Amanieu d'Antras <amanieu@...il.com>
> Cc: <stable@...r.kernel.org> # 5.3.x

I'm in favor of this change. But we need to make sure that any arch
which now has ARCH_WANTS_SYS_CLONE3 set but doesn't implement
copy_thread_tls() is fixed.

Once all architectures have clone3() support - and there are
just a few by now (IA64 comes to mind) this means we should also be able
to get rid of of copy_thread() completely. That seems desirable to me as
it makes the codepaths easier to follow.

Reviewed-by: Christian Brauner <christian.brauner@...ntu.com>