Re: [PATCH] x86: make DR*_RESERVED unsigned long

From: Oleg Nesterov
Date: Thu Apr 25 2013 - 10:51:38 EST

On 04/24, H. Peter Anvin wrote:
> On 04/24/2013 10:07 AM, Oleg Nesterov wrote:
> > DR6_RESERVED and DR_CONTROL_RESERVED are used to clear the set
> > bits in the "unsigned long" data, make them long to ensure that
> > "&~" doesn't clear the upper bits.
> >
> > do_debug() and ptrace_write_dr7() which use DR*_RESERVED look
> > safe, but probably it makes sense to cleanup anyway.
> >
> > Reported-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> > Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
> Can you please put in the description if this is a manifest or
> non-manifest bug and, if manifest, what the issues are? It greatly
> affects what we otherwise have to do to address the bug.

Sorry if it was not clear, I tried to explain in the changelog that
this is only cleanup. Yes, dr6 should have all zeroes in 32-64 so
the usage of DR6_RESERVED is safe.

> Also, the -UL suffix is usually capitalized in our codebase.

OK, iiuc otherwise you agree with this change. I'll send v2.


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