Re: [PATCH] compiler-intel: fix wrong compiler barrier() macro

From: mancha security
Date: Wed Apr 29 2015 - 11:00:35 EST

On Wed, Apr 29, 2015 at 10:51:40AM -0400, Pranith Kumar wrote:
> Hi Daniel,
> On Wed, Apr 29, 2015 at 10:42 AM, Daniel Borkmann <daniel@xxxxxxxxxxxxx> wrote:
> > Cleanup commit 23ebdedc67e ("compiler-intel.h: Remove duplicate
> > definition") removed the double definition of __memory_barrier()
> > intrinsics.
> >
> > However, in doing so, it also removed the preceding #undef barrier,
> > meaning, the actual barrier() macro from compiler-gcc.h with inline
> > asm is still in place when __GNUC__ is provided.
> When you use the Intel compilers, the barrier() definition will come
> from compiler.h and not compiler-gcc.h. That is what the commit
> message says in 73679e508201(your commit message has the wrong hash).
> I don't understand what problem you are seeing with this, can you
> please explain?
> Thanks!

Hi Pranith.

The problem is that ICC defines __GNUC__ so barrier() gets defined
in compiler-gcc.h. Your commit removed an #undef from compiler-intel.h
so compiler.h will never define barrier to __memory_barrier().


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