Message ID | 87sho99fye.fsf@concordia.ellerman.id.au (mailing list archive) |
---|---|
State | Accepted |
Headers | show |
On 2017/01/24 04:36PM, Michael Ellerman wrote: > Anton Blanchard <anton@samba.org> writes: > > We added: > > > > BUILD_BUG_ON(!__builtin_constant_p(feature)) > > > > to cpu_has_feature() and mmu_has_feature() in order to catch usage > > issues (such as cpu_has_feature(cpu_has_feature(X)). Unfortunately LLVM > > isn't smart enough to resolve this, and it errors out. > > > > I work around it in my clang/LLVM builds of the kernel, but I have just > > discovered that it causes a lot of issues for the bcc (eBPF) trace tool > > (which uses LLVM). > > I didn't understand that part, but Aneesh explained to me that it's > because bcc pulls in the kernel-internal headers. > > I guess as a quick fix we just have to #ifdef it, can you confirm this > works? This works and solves the issue for me. In the absence of a better approach, can you please push this for v4.10? Tested-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com> Thanks, Naveen > > > diff --git a/arch/powerpc/include/asm/cpu_has_feature.h b/arch/powerpc/include/asm/cpu_has_feature.h > index b312b152461b..6e834caa3720 100644 > --- a/arch/powerpc/include/asm/cpu_has_feature.h > +++ b/arch/powerpc/include/asm/cpu_has_feature.h > @@ -23,7 +23,9 @@ static __always_inline bool cpu_has_feature(unsigned long feature) > { > int i; > > +#ifndef __clang__ /* clang can't cope with this */ > BUILD_BUG_ON(!__builtin_constant_p(feature)); > +#endif > > #ifdef CONFIG_JUMP_LABEL_FEATURE_CHECK_DEBUG > if (!static_key_initialized) { > diff --git a/arch/powerpc/include/asm/mmu.h b/arch/powerpc/include/asm/mmu.h > index a34c764ca8dd..233a7e8cc8e3 100644 > --- a/arch/powerpc/include/asm/mmu.h > +++ b/arch/powerpc/include/asm/mmu.h > @@ -160,7 +160,9 @@ static __always_inline bool mmu_has_feature(unsigned long feature) > { > int i; > > +#ifndef __clang__ /* clang can't cope with this */ > BUILD_BUG_ON(!__builtin_constant_p(feature)); > +#endif > > #ifdef CONFIG_JUMP_LABEL_FEATURE_CHECK_DEBUG > if (!static_key_initialized) { > > > cheers >
diff --git a/arch/powerpc/include/asm/cpu_has_feature.h b/arch/powerpc/include/asm/cpu_has_feature.h index b312b152461b..6e834caa3720 100644 --- a/arch/powerpc/include/asm/cpu_has_feature.h +++ b/arch/powerpc/include/asm/cpu_has_feature.h @@ -23,7 +23,9 @@ static __always_inline bool cpu_has_feature(unsigned long feature) { int i; +#ifndef __clang__ /* clang can't cope with this */ BUILD_BUG_ON(!__builtin_constant_p(feature)); +#endif #ifdef CONFIG_JUMP_LABEL_FEATURE_CHECK_DEBUG if (!static_key_initialized) { diff --git a/arch/powerpc/include/asm/mmu.h b/arch/powerpc/include/asm/mmu.h index a34c764ca8dd..233a7e8cc8e3 100644 --- a/arch/powerpc/include/asm/mmu.h +++ b/arch/powerpc/include/asm/mmu.h @@ -160,7 +160,9 @@ static __always_inline bool mmu_has_feature(unsigned long feature) { int i; +#ifndef __clang__ /* clang can't cope with this */ BUILD_BUG_ON(!__builtin_constant_p(feature)); +#endif #ifdef CONFIG_JUMP_LABEL_FEATURE_CHECK_DEBUG if (!static_key_initialized) {