powerpc: Fix build failure with clang due to BUILD_BUG_ON()
authorMichael Ellerman <mpe@ellerman.id.au>
Tue, 24 Jan 2017 05:36:57 +0000 (16:36 +1100)
committerMichael Ellerman <mpe@ellerman.id.au>
Wed, 25 Jan 2017 02:36:10 +0000 (13:36 +1100)
commitb5fa0f7f88edcde37df1807fdf9ff10ec787a60e
tree3f0c8e6904907d51ccaf858963bb597970266d05
parentf2574030b0e33263b8a1c28fa3c4fa9292283799
powerpc: Fix build failure with clang due to BUILD_BUG_ON()

Anton says: In commit 4db7327194db ("powerpc: Add option to use jump
label for cpu_has_feature()") and commit c12e6f24d413 ("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: 4db7327194db ("powerpc: Add option to use jump label for cpu_has_feature()")
Fixes: c12e6f24d413 ("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>
arch/powerpc/include/asm/cpu_has_feature.h
arch/powerpc/include/asm/mmu.h