linux-kernel - Re: [RFC] de-asmify the x86-64 system call slowpath

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Date:	Mon, 27 Jan 2014 18:39:31 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Al Viro <viro@...IV.linux.org.uk>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Peter Anvin <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	the arch/x86 maintainers <x86@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [RFC] de-asmify the x86-64 system call slowpath

On 01/27, Al Viro wrote:
>
> BTW, there's an additional pile of obfuscation:
> /* work to do on interrupt/exception return */
> #define _TIF_WORK_MASK                                                  \
>         (0x0000FFFF &                                                   \
>          ~(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT|                       \
>            _TIF_SINGLESTEP|_TIF_SECCOMP|_TIF_SYSCALL_EMU))
>
> /* work to do on any return to user space */
> #define _TIF_ALLWORK_MASK                                               \
>         ((0x0000FFFF & ~_TIF_SECCOMP) | _TIF_SYSCALL_TRACEPOINT |       \
>         _TIF_NOHZ)

Heh, yes ;)

> Why is _TIF_UPROBE *not* a part
> of _TIF_DO_NOTIFY_MASK, for example?

Yes, please see another email. That is why uprobe_deny_signal()
sets TIF_NOTIFY_RESUME along with TIF_UPROBE.

Oleg.

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