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

[Geert Uytterhoeven]

On Tue, Jan 14, 2014 at 5:32 PM, Geert Uytterhoeven
<geert@xxxxxxxxxxxxxx> wrote:
> https://lkml.org/lkml/2013/12/11/141
>
> On Tue, Jan 14, 2014 at 5:19 PM, H. Peter Anvin <hpa@xxxxxxxxx> 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@xxxxxxxxxxxxxx

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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