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powerpc: Fix build failure with clang due to BUILD_BUG_ON()

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Anton says: In commit 4db7327194 ("powerpc: Add option to use jump
label for cpu_has_feature()") and commit c12e6f24d4 ("powerpc: Add
option to use jump label for mmu_has_feature()") 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), which has happened
once in the past). 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).

For now just #ifdef it away for clang builds.

Fixes: 4db7327194 ("powerpc: Add option to use jump label for cpu_has_feature()")
Fixes: c12e6f24d4 ("powerpc: Add option to use jump label for mmu_has_feature()")
Cc: stable@vger.kernel.org # v4.8+
Reported-by: Anton Blanchard <anton@samba.org>
Tested-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Michael Ellerman 2017-01-24 16:36:57 +11:00
parent f2574030b0
commit b5fa0f7f88
2 changed files with 4 additions and 0 deletions
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2
arch/powerpc/include/asm/cpu_has_feature.h
View File

@ -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) {

2
arch/powerpc/include/asm/mmu.h
View File

@ -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) {