Re: [tip:x86/mm] x86, mm: Redesign get_user with a __builtin_choose_expr hack
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- Subject: Re: [tip:x86/mm] x86, mm: Redesign get_user with a __builtin_choose_expr hack
- From: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
- Date: Tue, 12 Feb 2013 15:49:07 -0800
- Cc: Ingo Molnar <mingo@xxxxxxxxxx>, Linux Kernel Mailing List <linux-kernel@xxxxxxxxxxxxxxx>, Jamie Lokier <jamie@xxxxxxxxxxxxx>, ville.syrjala@xxxxxxxxxxxxxxx, Borislav Petkov <bp@xxxxxxxxx>, Russell King - ARM Linux <linux@xxxxxxxxxxxxxxxx>, Thomas Gleixner <tglx@xxxxxxxxxxxxx>, "H. Peter Anvin" <hpa@xxxxxxxxxxxxxxx>, "H.J. Lu" <hjl.tools@xxxxxxxxx>, linux-tip-commits@xxxxxxxxxxxxxxx
- In-reply-to: <511ACDFB.1050707@zytor.com>
On Tue, Feb 12, 2013 at 3:19 PM, H. Peter Anvin <hpa@xxxxxxxxx> wrote:
>
> Yes, but there doesn't seem to be any other way to do this. gcc won't
> even allow "=cd" even if we know the variable is 64 bits, even though
> "=A" is documented to be equivalent to "=da".
No, "=da" means value "in edx _or_ %eax". Not the same as "A".
But you're right, there's nothing similar for %ebx:%ecx. I thought
there was. I was really sure we did something special for 64-bit adc
etc.
> Let me know what you think.
I guess we don't have any choice. And the other cleanups certainly look good.
Linus
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