linux-kernel - [PATCH 3.16 344/346] compiler-gcc: disable -ftracer for _

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Date:   Mon, 14 Nov 2016 00:14:21 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Linda Walsh" <lkml@...nx.org>,
        "Philip Müller" <philm@...jaro.org>,
        "Paolo Bonzini" <pbonzini@...hat.com>, kvm@...r.kernel.org,
        "Michal Marek" <mmarek@...e.cz>
Subject: [PATCH 3.16 344/346] compiler-gcc: disable -ftracer for __noclone
 functions

3.16.39-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>
Cc: Philip Müller <philm@...jaro.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 include/linux/compiler-gcc.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -177,7 +177,7 @@
 #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 */