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Subject[PATCH 4.14 26/54] x86/oprofile: Fix bogus GCC-8 warning in nmi_setup()
4.14-stable review patch.  If anyone has any objections, please let me know.


From: Arnd Bergmann <>

commit 85c615eb52222bc5fab6c7190d146bc59fac289e upstream.

GCC-8 shows a warning for the x86 oprofile code that copies per-CPU
data from CPU 0 to all other CPUs, which when building a non-SMP
kernel turns into a memcpy() with identical source and destination

arch/x86/oprofile/nmi_int.c: In function 'mux_clone':
arch/x86/oprofile/nmi_int.c:285:2: error: 'memcpy' source argument is the same as destination [-Werror=restrict]
memcpy(per_cpu(cpu_msrs, cpu).multiplex,
per_cpu(cpu_msrs, 0).multiplex,
sizeof(struct op_msr) * model->num_virt_counters);
arch/x86/oprofile/nmi_int.c: In function 'nmi_setup':
arch/x86/oprofile/nmi_int.c:466:3: error: 'memcpy' source argument is the same as destination [-Werror=restrict]
arch/x86/oprofile/nmi_int.c:470:3: error: 'memcpy' source argument is the same as destination [-Werror=restrict]

I have analyzed a number of such warnings now: some are valid and the
GCC warning is welcome. Others turned out to be false-positives, and
GCC was changed to not warn about those any more. This is a corner case
that is a false-positive but the GCC developers feel it's better to keep
warning about it.

In this case, it seems best to work around it by telling GCC
a little more clearly that this code path is never hit with
an IS_ENABLED() configuration check.

Cc:stable as we also want old kernels to build cleanly with GCC-8.

Signed-off-by: Arnd Bergmann <>
Cc: Jessica Yu <>
Cc: Kees Cook <>
Cc: Linus Torvalds <>
Cc: Martin Sebor <>
Cc: Peter Zijlstra <>
Cc: Robert Richter <>
Cc: Thomas Gleixner <>
Signed-off-by: Ingo Molnar <>
Signed-off-by: Greg Kroah-Hartman <>

arch/x86/oprofile/nmi_int.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/x86/oprofile/nmi_int.c
+++ b/arch/x86/oprofile/nmi_int.c
@@ -460,7 +460,7 @@ static int nmi_setup(void)
goto fail;

for_each_possible_cpu(cpu) {
- if (!cpu)
+ if (!IS_ENABLED(CONFIG_SMP) || !cpu)

memcpy(per_cpu(cpu_msrs, cpu).counters,

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