linux-kernel - Re: [PATCH] ptrace/x86: introduce TS_COMPAT_RESTART to fix get_nr_restart

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Date:   Tue, 26 Nov 2019 12:07:58 +0100
From:   Oleg Nesterov <oleg@...hat.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Andy Lutomirski <luto@...nel.org>, Borislav Petkov <bp@...en8.de>,
        Ingo Molnar <mingo@...nel.org>,
        Jan Kratochvil <jan.kratochvil@...hat.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Pedro Alves <palves@...hat.com>, Peter Anvin <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH] ptrace/x86: introduce TS_COMPAT_RESTART to fix
 get_nr_restart_syscall()

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,

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

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

but this patch looks simpler to me.

Oleg.