linux-kernel - Re: [PATCH v2 0/3] x86: PER

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Message-ID: <CALCETrW9uC25yCMHSGYag=52DH363T=ThRCdKPETfYou2boGRA@mail.gmail.com>
Date:	Fri, 22 Aug 2014 18:15:39 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	"H. Peter Anvin" <hpa@...or.com>, X86 ML <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Cc:	Andy Lutomirski <luto@...capital.net>
Subject: Re: [PATCH v2 0/3] x86: PER_CPU segment improvements

On Wed, Jul 30, 2014 at 3:07 PM, Andy Lutomirski <luto@...capital.net> wrote:
> x86 sets up a per-cpu GDT entry so that vgetcpu can use LSL on it
> to determine the CPU number and node.

hpa, if/when you apply this, can you put it onto a fresh branch based
on something at least as new as 3.17-rc1?  It should apply cleanly
regardless, but the nine followup patches that I want to send also
depend on cleanup that isn't in tip/x86/vdso.

Thanks,
Andy

>
> This series, in little baby steps, cleans up that code and sets
> the accessed and 32-bit flags on the segment.
>
> The accessed bit prevents user code from setting the accessed bit
> on its own, and making the segment 32-bit prevents concerns about
> shenanigans involving CPU oddities with 16-bit data segments.
>
> The latter isn't a real problem -- if it were a 16-bit read/write
> segment, it could be used to bypass espfix64, but fortunately
> RO segments can't be loaded into SS.
>
> Changes from v1:
>  - Fix patch 2's changelog.
>  - Learn to spell "Not a system segment".
>
> Andy Lutomirski (3):
>   x86,vdso: Change the PER_CPU segment to use struct desc_struct
>   x86,vdso: Make the PER_CPU segment start out accessed
>   x86,vdso: Make the PER_CPU segment 32 bits
>
>  arch/x86/kernel/vsyscall_64.c | 19 ++++++++++++-------
>  1 file changed, 12 insertions(+), 7 deletions(-)
>
> --
> 1.9.3
>



-- 
Andy Lutomirski
AMA Capital Management, LLC
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