linux-kernel - Re: [PATCH] ARC: uaccess: get_user to zero out dest in cause of fault

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Date:   Sun, 21 Aug 2016 02:40:30 +0100
From:   Al Viro <viro@...IV.linux.org.uk>
To:     "H. Peter Anvin" <hpa@...or.com>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Jakub Jelinek <jakub@...hat.com>,
        Vineet Gupta <Vineet.Gupta1@...opsys.com>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH] ARC: uaccess: get_user to zero out dest in cause of fault

On Sat, Aug 20, 2016 at 06:09:15PM -0700, H. Peter Anvin wrote:

> >Sorry for the bogus noise. I don't know why I was so convinced setjmp
> >needed special gcc semantics.
> >
> >             Linus
> 
> I think the specific name setjmp() is magic in gcc.

It is; attribute equivalent is returns_twice.  I wonder if "explicitly
clobber everything if we got false" + asm volatile to prevent reordering
would suffice for our purposes, but that's really a question for gcc
folks...