From: H. Peter Anvin
Date: Wed Feb 27 2013 - 17:55:45 EST

On 02/27/2013 02:52 PM, Stephen Boyd wrote:
> On 02/27/13 14:19, H. Peter Anvin wrote:
>> On 02/27/2013 12:42 PM, Stephen Boyd wrote:
>>>> It's fine to do your patch as a first step though, which would not
>>>> change the behavior.
>>> A lot of arches seem to not want to enable it because false positives
>>> are everywhere. It really depends on how good the compiler is at doing
>>> constant propagation and dead code removal.
>> Although some of the cases I have seen being flagged as "false
>> positives" have been real bugs.
> There were so many false-positives on x86_64 that Andrew eventually
> dropped my patch to add support for this option to the copy_from_user()
> function there.

I would probably have taken it, especially if it came with more x86-64
to i386 unification.

It's an option, though.


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