linux-kernel - Re: [PATCH v4 1/6] x86-64: Clean up vdso/kernel shared variables

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Date:	Mon, 16 May 2011 19:23:38 +0200
From:	Borislav Petkov <bp@...64.org>
To:	Andy Lutomirski <luto@....EDU>
Cc:	"x86@...nel.org" <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>, Andi Kleen <andi@...stfloor.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Thomas Gleixner <tglx@...utronix.de>,
	Borislav Petkov <bp@...64.org>
Subject: Re: [PATCH v4 1/6] x86-64: Clean up vdso/kernel shared variables

On Mon, May 16, 2011 at 12:00:58PM -0400, Andy Lutomirski wrote:
> Variables that are shared between the vdso and the kernel are
> currently a bit of a mess.  They are each defined with their own
> magic, they are accessed differently in the kernel, the vsyscall page,
> and the vdso, and one of them (vsyscall_clock) doesn't even really
> exist.
> 
> This changes them all to use a common mechanism.  All of them are
> delcared in vvar.h with a fixed address (validated by the linker
> script).  In the kernel (as before), they look like ordinary
> read-write variables.  In the vsyscall page and the vdso, they are
> accessed through a new macro VVAR, which gives read-only access.
> 
> The vdso is now loaded verbatim into memory without any fixups.  As a
> side bonus, access from the vdso is faster because a level of
> indirection is removed.
> 
> While we're at it, pack jiffies and vgetcpu_mode into the same
> cacheline.

How about

Signed-off-by:...

or you don't wanna? :)

> ---
>  arch/x86/include/asm/vdso.h     |   14 ----------
>  arch/x86/include/asm/vgtod.h    |    2 -
>  arch/x86/include/asm/vsyscall.h |   12 +-------
>  arch/x86/include/asm/vvar.h     |   52 +++++++++++++++++++++++++++++++++++++++
>  arch/x86/kernel/time.c          |    2 +-
>  arch/x86/kernel/tsc.c           |    4 +-
>  arch/x86/kernel/vmlinux.lds.S   |   34 ++++++++-----------------
>  arch/x86/kernel/vsyscall_64.c   |   46 +++++++++++++++-------------------
>  arch/x86/vdso/Makefile          |    2 +-
>  arch/x86/vdso/vclock_gettime.c  |    3 +-
>  arch/x86/vdso/vdso.lds.S        |    7 -----
>  arch/x86/vdso/vextern.h         |   16 ------------
>  arch/x86/vdso/vgetcpu.c         |    3 +-
>  arch/x86/vdso/vma.c             |   27 --------------------
>  arch/x86/vdso/vvar.c            |   12 ---------
>  15 files changed, 91 insertions(+), 145 deletions(-)
>  create mode 100644 arch/x86/include/asm/vvar.h
>  delete mode 100644 arch/x86/vdso/vextern.h
>  delete mode 100644 arch/x86/vdso/vvar.c
> 

-- 
Regards/Gruss,
Boris.

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