linux-kernel - RE: [RFC][PATCH 01/22] x86 user stack frame reads: switch to explicit __get

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Date:   Sun, 29 Mar 2020 18:03:49 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Linus Torvalds' <torvalds@...ux-foundation.org>
CC:     Andy Lutomirski <luto@...capital.net>,
        Ingo Molnar <mingo@...nel.org>,
        "Al Viro" <viro@...iv.linux.org.uk>,
        Thomas Gleixner <tglx@...utronix.de>, X86 ML <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Borislav Petkov <bp@...en8.de>
Subject: RE: [RFC][PATCH 01/22] x86 user stack frame reads: switch to explicit
 __get_user()

From: Linus Torvalds
> Sent: 29 March 2020 18:57
> On Sun, Mar 29, 2020 at 10:41 AM David Laight <David.Laight@...lab.com> wrote:
> >
> > It may be worth implementing get_user() as an inline
> > function that writes the result of access_ok() to a
> > 'by reference' parameter and then returns the value
> > from an 'real' __get_user() function.
> 
> That's how get_user() already works.
> 
> It is a polymorphic function (done using macros, sizeof() and ugly
> compiler tricks) that generates a call, yes. But it's not a normal C
> call. On x86-64, it returns the error code in %rax, and the value in
> %rdx

I must be mis-remembering the object code from last time
I looked at it.

	David

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