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Re: [PATCH 2/5] powerpc/mm: split store_updates_sp() in two parts in do_page_fault()

From Benjamin Herrenschmidt <benh@kernel.crashing.org>
Newsgroups linux.kernel
Subject Re: [PATCH 2/5] powerpc/mm: split store_updates_sp() in two parts in do_page_fault()
Date 2017-06-02 14:20 +0200
Message-ID <tNTIC-Vj-5@gated-at.bofh.it> (permalink)
References <txXnb-3yQ-11@gated-at.bofh.it> <txXnb-3yQ-19@gated-at.bofh.it> <tNR46-7yN-31@gated-at.bofh.it> <tNRns-7G9-31@gated-at.bofh.it>
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On Fri, 2017-06-02 at 11:39 +0200, Christophe LEROY wrote:
> The difference between get_user() and __get_user() is that get_user() 
> performs an access_ok() in addition.
> 
> Doesn't access_ok() only checks whether addr is below TASK_SIZE to 
> ensure it is a valid user address ?

Do you have a measurable improvement by skipping that check ? I agree
with your reasoning but I'm also paranoid and so I wouldn't change it
unless it's really worth it.

Cheers,
Ben.

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Re: [PATCH 2/5] powerpc/mm: split store_updates_sp() in two parts in do_page_fault() Michael Ellerman <mpe@ellerman.id.au> - 2017-06-02 11:30 +0200
  Re: [PATCH 2/5] powerpc/mm: split store_updates_sp() in two parts in  do_page_fault() Christophe LEROY <christophe.leroy@c-s.fr> - 2017-06-02 11:50 +0200
    Re: [PATCH 2/5] powerpc/mm: split store_updates_sp() in two parts  in do_page_fault() Benjamin Herrenschmidt <benh@kernel.crashing.org> - 2017-06-02 14:20 +0200
      Re: [PATCH 2/5] powerpc/mm: split store_updates_sp() in two parts in  do_page_fault() Christophe LEROY <christophe.leroy@c-s.fr> - 2017-06-02 14:40 +0200
        Re: [PATCH 2/5] powerpc/mm: split store_updates_sp() in two parts in do_page_fault() Michael Ellerman <mpe@ellerman.id.au> - 2017-06-05 12:50 +0200
    Re: [PATCH 2/5] powerpc/mm: split store_updates_sp() in two parts in do_page_fault() Michael Ellerman <mpe@ellerman.id.au> - 2017-06-05 12:50 +0200
      Re: [PATCH 2/5] powerpc/mm: split store_updates_sp() in two parts in  do_page_fault() christophe leroy <christophe.leroy@c-s.fr> - 2017-06-05 19:50 +0200
        Re: [PATCH 2/5] powerpc/mm: split store_updates_sp() in two parts in do_page_fault() Michael Ellerman <mpe@ellerman.id.au> - 2017-06-06 13:10 +0200
          Re: [PATCH 2/5] powerpc/mm: split store_updates_sp() in two parts in  do_page_fault() Christophe LEROY <christophe.leroy@c-s.fr> - 2017-06-06 15:40 +0200

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