linux-kernel - Re: futex: Switch to USER_DS for futex test (was: Re: linux-next: manual merge of the akpm-current tree with the tip tree)

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Message-ID: <CAMuHMdUJhjtogAPKzN6cua1KdtMbhZ1U0MBt6QaD6t3e_BMCMQ@mail.gmail.com>
Date:	Wed, 15 Jan 2014 20:59:31 +0100
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>,
	Linux-Next <linux-next@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Davidlohr Bueso <davidlohr@...com>,
	Linux-Arch <linux-arch@...r.kernel.org>,
	Andreas Schwab <schwab@...ux-m68k.org>,
	Heiko Carstens <heiko.carstens@...ibm.com>
Subject: Re: futex: Switch to USER_DS for futex test (was: Re: linux-next:
 manual merge of the akpm-current tree with the tip tree)

On Tue, Jan 14, 2014 at 5:32 PM, Geert Uytterhoeven
<geert@...ux-m68k.org> wrote:
> https://lkml.org/lkml/2013/12/11/141
>
> On Tue, Jan 14, 2014 at 5:19 PM, H. Peter Anvin <hpa@...or.com> wrote:
>> On 01/14/2014 05:17 AM, Geert Uytterhoeven wrote:
>>>>
>>>> This seems terribly broken, the *futex_value*() ops should not need
>>>> that; they are supposed to access userspace without any of that.
>>>
>>> Why don't they need set_fs(USER_DS)?
>>
>> Because USER_DS is the normal operating state?  It would appear m68k is
>
> Is it?
>
>> the only(?) arch that calls initcalls with get_fs() == KERNEL_DS...
>
> On ARM:
>
> fs = 0x0, USER_DS = 0xbf000000, KERNEL_DS = 0x0
>
> Presumably also on s390, as the fix for m68k broke s390. That's why it's still
> in -mm and not yet in mainline.

On uml/amd64:

fs = 0xffffffff, USER_DS = 0x7fc0000000, KERNEL_DS = 0xffffffff

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
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