linux-kernel - Re: [PATCH 02/34] AMD IOMMU: add header file for driver data structures and defines

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Thu, 10 Jul 2008 14:12:22 +0200
From:	Joerg Roedel <joerg.roedel@....com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	Arjan van de Ven <arjan@...radead.org>, tglx@...utronix.de,
	mingo@...hat.com, linux-kernel@...r.kernel.org,
	iommu@...ts.linux-foundation.org, bhavna.sarathy@....com,
	Sebastian.Biemueller@....com, robert.richter@....com,
	joro@...tes.org
Subject: Re: [PATCH 02/34] AMD IOMMU: add header file for driver data structures and defines

On Wed, Jul 09, 2008 at 07:36:01PM -0700, Andrew Morton wrote:
> On Wed, 9 Jul 2008 18:50:55 -0700 Arjan van de Ven <arjan@...radead.org> wrote:
> 
> > On Wed, 9 Jul 2008 18:38:23 -0700
> > Andrew Morton <akpm@...ux-foundation.org> wrote:
> > 
> > > On Thu, 26 Jun 2008 21:27:38 +0200 Joerg Roedel
> > > <joerg.roedel@....com> wrote:
> > > 
> > > > +/* helper macros */
> > > > +#define LOW_U32(x) ((x) & ((1ULL << 32)-1))
> > > > +#define HIGH_U32(x) (LOW_U32((x) >> 32))
> > > 
> > > Please avoid putting general-purpose helpers into private header
> > > files.
> > 
> > especially broken helpers.
> > 
> > A >> 32 on something that may be a 32 bit entry is bad; int32 >> 32...
> > gcc can (and does!) optimize that out.
> > 
> > (because it first gets translated into a SHR x86 instruction which then
> > notices it's encoded as a zero shift.. which then gets deleted)
> > 
> 
> Well yeah.  upper_32_bits() gets it all corect.  We could do a
> lower_32_bits() I suppose, if it's useful.

Ok cool, I agree. I will replace the HIGH_U32 macro with the
upper_32_bits() function and the other one with lower_32_bits() if it
exists. Who will take the patch for the introduction of that function?

Joerg

-- 
           |           AMD Saxony Limited Liability Company & Co. KG
 Operating |         Wilschdorfer Landstr. 101, 01109 Dresden, Germany
 System    |                  Register Court Dresden: HRA 4896
 Research  |              General Partner authorized to represent:
 Center    |             AMD Saxony LLC (Wilmington, Delaware, US)
           | General Manager of AMD Saxony LLC: Dr. Hans-R. Deppe, Thomas McCoy

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/