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[PATCH] compiler-gcc: disable -ftracer for __noclone functions

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  [PATCH] compiler-gcc: disable -ftracer for __noclone functions Paolo Bonzini <pbonzini@redhat.com> - 2016-03-31 09:50 +0200
    Re: [PATCH] compiler-gcc: disable -ftracer for __noclone functions kbuild test robot <lkp@intel.com> - 2016-03-31 10:40 +0200

#1367921 — [PATCH] compiler-gcc: disable -ftracer for __noclone functions

-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@linux-foundation.org>
Cc: Michal Marek <mmarek@suse.cz>
Cc: stable@vger.kernel.org
Cc: kvm@vger.kernel.org
Reported-by: Linda Walsh <lkml@tlinx.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 include/linux/compiler-gcc.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index 22ab246feed3..eeae401a2412 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -199,7 +199,7 @@
 #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 */
 
-- 
2.5.5

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#1367984

Hi Paolo,

[auto build test WARNING on v4.6-rc1]
[also build test WARNING on next-20160331]
[if your patch is applied to the wrong git tree, please drop us a note to help improving the system]

url:    https://github.com/0day-ci/linux/commits/Paolo-Bonzini/compiler-gcc-disable-ftracer-for-__noclone-functions/20160331-154556
reproduce:
        # apt-get install sparse
        make ARCH=x86_64 allmodconfig
        make C=1 CF=-D__CHECK_ENDIAN__


sparse warnings: (new ones prefixed by >>)

   include/linux/compiler.h:232:8: sparse: attribute 'no_sanitize_address': unknown attribute
>> arch/x86/kvm/vmx.c:8610:13: sparse: attribute '__optimize__': unknown attribute

vim +/__optimize__ +8610 arch/x86/kvm/vmx.c

d7cd9796 arch/x86/kvm/vmx.c Gleb Natapov    2011-10-05  8594  	int i, nr_msrs;
d7cd9796 arch/x86/kvm/vmx.c Gleb Natapov    2011-10-05  8595  	struct perf_guest_switch_msr *msrs;
d7cd9796 arch/x86/kvm/vmx.c Gleb Natapov    2011-10-05  8596  
d7cd9796 arch/x86/kvm/vmx.c Gleb Natapov    2011-10-05  8597  	msrs = perf_guest_get_msrs(&nr_msrs);
d7cd9796 arch/x86/kvm/vmx.c Gleb Natapov    2011-10-05  8598  
d7cd9796 arch/x86/kvm/vmx.c Gleb Natapov    2011-10-05  8599  	if (!msrs)
d7cd9796 arch/x86/kvm/vmx.c Gleb Natapov    2011-10-05  8600  		return;
d7cd9796 arch/x86/kvm/vmx.c Gleb Natapov    2011-10-05  8601  
d7cd9796 arch/x86/kvm/vmx.c Gleb Natapov    2011-10-05  8602  	for (i = 0; i < nr_msrs; i++)
d7cd9796 arch/x86/kvm/vmx.c Gleb Natapov    2011-10-05  8603  		if (msrs[i].host == msrs[i].guest)
d7cd9796 arch/x86/kvm/vmx.c Gleb Natapov    2011-10-05  8604  			clear_atomic_switch_msr(vmx, msrs[i].msr);
d7cd9796 arch/x86/kvm/vmx.c Gleb Natapov    2011-10-05  8605  		else
d7cd9796 arch/x86/kvm/vmx.c Gleb Natapov    2011-10-05  8606  			add_atomic_switch_msr(vmx, msrs[i].msr, msrs[i].guest,
d7cd9796 arch/x86/kvm/vmx.c Gleb Natapov    2011-10-05  8607  					msrs[i].host);
d7cd9796 arch/x86/kvm/vmx.c Gleb Natapov    2011-10-05  8608  }
d7cd9796 arch/x86/kvm/vmx.c Gleb Natapov    2011-10-05  8609  
a3b5ba49 arch/x86/kvm/vmx.c Lai Jiangshan   2011-02-11 @8610  static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu)
6aa8b732 drivers/kvm/vmx.c  Avi Kivity      2006-12-10  8611  {
a2fa3e9f drivers/kvm/vmx.c  Gregory Haskins 2007-07-27  8612  	struct vcpu_vmx *vmx = to_vmx(vcpu);
d974baa3 arch/x86/kvm/vmx.c Andy Lutomirski 2014-10-08  8613  	unsigned long debugctlmsr, cr4;
104f226b arch/x86/kvm/vmx.c Avi Kivity      2010-11-18  8614  
104f226b arch/x86/kvm/vmx.c Avi Kivity      2010-11-18  8615  	/* Record the guest's net vcpu time for enforced NMI injections. */
104f226b arch/x86/kvm/vmx.c Avi Kivity      2010-11-18  8616  	if (unlikely(!cpu_has_virtual_nmis() && vmx->soft_vnmi_blocked))
104f226b arch/x86/kvm/vmx.c Avi Kivity      2010-11-18  8617  		vmx->entry_time = ktime_get();
104f226b arch/x86/kvm/vmx.c Avi Kivity      2010-11-18  8618  

:::::: The code at line 8610 was first introduced by commit
:::::: a3b5ba49a8c58d9a578e016523b047467a41e047 KVM: VMX: add the __noclone attribute to vmx_vcpu_run

:::::: TO: Lai Jiangshan <laijs@cn.fujitsu.com>
:::::: CC: Marcelo Tosatti <mtosatti@redhat.com>

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

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