linux-kernel - [PATCH 4.1 222/267] compiler-intel: fix wrong compiler barrier() macro

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Date:	Fri, 31 Jul 2015 12:41:13 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Daniel Borkmann <daniel@...earbox.net>,
	Pranith Kumar <bobby.prani@...il.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	mancha security <mancha1@...o.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 4.1 222/267] compiler-intel: fix wrong compiler barrier() macro

4.1-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Daniel Borkmann <daniel@...earbox.net>

commit b86a50c3b5414eafdbee7f34af4a201a4a7817c2 upstream.

Cleanup commit 73679e508201 ("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 by
accident, meaning, the actual barrier() macro from compiler-gcc.h with
inline asm is still in place as __GNUC__ is provided.

Subsequently, barrier() can never be defined as __memory_barrier() from
compiler.h since it already has a definition in place and if we trust
the comment in compiler-intel.h, ecc doesn't support gcc specific asm
statements.

I don't have an ecc at hand (unsure if that's still used in the field?)
and only found this by accident during code review, a revert of that
cleanup would be simplest option.

Fixes: 73679e508201 ("compiler-intel.h: Remove duplicate definition")
Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
Reviewed-by: Pranith Kumar <bobby.prani@...il.com>
Cc: Pranith Kumar <bobby.prani@...il.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: mancha security <mancha1@...o.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 include/linux/compiler-intel.h |    2 ++
 1 file changed, 2 insertions(+)

--- a/include/linux/compiler-intel.h
+++ b/include/linux/compiler-intel.h
@@ -13,10 +13,12 @@
 /* Intel ECC compiler doesn't support gcc specific asm stmts.
  * It uses intrinsics to do the equivalent things.
  */
+#undef barrier
 #undef barrier_data
 #undef RELOC_HIDE
 #undef OPTIMIZER_HIDE_VAR

+#define barrier() __memory_barrier()
 #define barrier_data(ptr) barrier()

 #define RELOC_HIDE(ptr, off)					\

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