linux-kernel - [PATCH 3.16 168/217] compiler-gcc: disable -ftracer for _

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Message-ID: <lsq.1461711741.993394016@decadent.org.uk>
Date:	Wed, 27 Apr 2016 01:02:21 +0200
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org, kvm@...r.kernel.org,
	"Linda Walsh" <lkml@...nx.org>,
	"Paolo Bonzini" <pbonzini@...hat.com>,
	"Michal Marek" <mmarek@...e.cz>
Subject: [PATCH 3.16 168/217] compiler-gcc: disable -ftracer for __noclone
 functions

3.16.35-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Paolo Bonzini <pbonzini@...hat.com>

commit 95272c29378ee7dc15f43fa2758cb28a5913a06d upstream.

-ftracer can duplicate asm blocks causing compilation to fail in
noclone functions.  For example, KVM declares a global variable
in an asm like

    asm("2: ... \n
         .pushsection data \n
         .global vmx_return \n
         vmx_return: .long 2b");

and -ftracer causes a double declaration.

Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Michal Marek <mmarek@...e.cz>
Cc: kvm@...r.kernel.org
Reported-by: Linda Walsh <lkml@...nx.org>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
[bwh: Backported to 3.16: apply to compiler-gcc{4,5}.h]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
--- a/include/linux/compiler-gcc4.h
+++ b/include/linux/compiler-gcc4.h
@@ -54,7 +54,7 @@
 #define unreachable() __builtin_unreachable()
 
 /* Mark a function definition as prohibited from being cloned. */
-#define __noclone	__attribute__((__noclone__))
+#define __noclone	__attribute__((__noclone__, __optimize__("no-tracer")))
 
 #endif /* GCC_VERSION >= 40500 */
 
--- a/include/linux/compiler-gcc5.h
+++ b/include/linux/compiler-gcc5.h
@@ -40,7 +40,7 @@
 #define unreachable() __builtin_unreachable()
 
 /* Mark a function definition as prohibited from being cloned. */
-#define __noclone	__attribute__((__noclone__))
+#define __noclone	__attribute__((__noclone__, __optimize__("no-tracer")))
 
 /*
  * Tell the optimizer that something else uses this function or variable.