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Date:   Tue, 26 Nov 2019 12:07:58 +0100
From:   Oleg Nesterov <oleg@redhat.com>
To:     Andrew Morton <akpm@linux-foundation.org>
Cc:     Andy Lutomirski <luto@kernel.org>, Borislav Petkov <bp@alien8.de>,
        Ingo Molnar <mingo@kernel.org>,
        Jan Kratochvil <jan.kratochvil@redhat.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Pedro Alves <palves@redhat.com>, Peter Anvin <hpa@zytor.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        linux-kernel@vger.kernel.org, x86@kernel.org
Subject: Re: [PATCH] ptrace/x86: introduce TS_COMPAT_RESTART to fix
 get_nr_restart_syscall()
Message-ID: <20191126110758.GA14051@redhat.com>
References: <20191126110659.GA14042@redhat.com>
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On 11/26, Oleg Nesterov wrote:
>
> This patch adds the sticky TS_COMPAT_RESTART flag which survives after
> return to user mode, hopefully it allows us to kill TS_I386_REGS_POKED
> but this needs another patch.

Alternatively we could add ->compat_restart into struct restart_block,
logically this is the same thing.

Rather than changing syscall_return_slowpath() we could introduce a new
helper, say,

=09void set_restart_block_fn(struct restart_block *restart, fn)
=09{
=09=09restart->fn =3D fn;

=09=09set/clear TS_COMPAT_RESTART or restart->compat_restart
=09=09depending on TS_COMPAT
=09}

but this patch looks simpler to me.

Oleg.