From mboxrd@z Thu Jan  1 00:00:00 1970
From: Stafford Horne <shorne@gmail.com>
Subject: Re: architectures that still need to remove set_fs()
Date: Tue, 18 Jan 2022 20:48:17 +0900
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To: Christoph Hellwig <hch@lst.de>
Cc: Richard Henderson <rth@twiddle.net>, Ivan Kokshaysky <ink@jurassic.park.msu.ru>, Matt Turner <mattst88@gmail.com>, Vineet Gupta <vgupta@kernel.org>, Guo Ren <guoren@kernel.org>, Brian Cain <bcain@codeaurora.org>, Michal Simek <monstr@monstr.eu>, Nick Hu <nickhu@andestech.com>, Greentime Hu <green.hu@gmail.com>, Vincent Chen <deanbo422@gmail.com>, Dinh Nguyen <dinguyen@kernel.org>, Jonas Bonn <jonas@southpole.se>, Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>, Yoshinori Sato <ysato@users.sourceforge.jp>, Rich Felker <dalias@libc.org>, "David S. Miller" <davem@davemloft.net>, Chris Zankel <chris@zankel.net>, Max Filippov <jcmvbkbc@gmail.com>, linux-alpha@vger.kernel.org, linux-snps-arc@lists.infradead.org, linux-csky@vger.kernel.org

Hi,

On Tue, Jan 18, 2022 at 08:48:36AM +0100, Christoph Hellwig wrote:
> Hi all,
> 
> you are in this list because your architecture still implements and
> uses address space overrides using set_fs(), which are deprecated and
> have been removed from all mainstream architecture ports.  To help
> cleanup the core kernel it would be great to make progress on removing
> set_fs entirely.
> 
> The following steps are required:
> 
>  (1) implement the __get_kernel_nofault and __put_kernel_nofault
>      helper to access kernel memory without page faults, replacing
>      the get/put_user under set_fs(KERNEL_DS) abuse.  Mips has a good
>      example for a trivial implementation for architectures that use
>      a common address space in commit 04324f44cb69

Also see commit 08ee3a009f49a which is preparation for removing set_fs/get_fs
this commit implements __get_kernel_nofault/__put_kernel_nofault for mips.

>  (2) remove any architecture specific use of such constructs.  This
>      only affects ia64 and sh.
>  (3) stop selecting the SET_FS and remove all the set_fs-related
>      infrastructure.  The above mips commit is a good guide once again.
> 
> Thanks!

I will look into this for OpenRISC.

-Stafford