From: Nathan Chancellor nathan@kernel.org
commit 015d98149b326e0f1f02e44413112ca8b4330543 upstream.
A change in clang 13 results in the __lwsync macro being defined as __builtin_ppc_lwsync, which emits 'lwsync' or 'msync' depending on what the target supports. This breaks the build because of -Werror in arch/powerpc, along with thousands of warnings:
In file included from arch/powerpc/kernel/pmc.c:12: In file included from include/linux/bug.h:5: In file included from arch/powerpc/include/asm/bug.h:109: In file included from include/asm-generic/bug.h:20: In file included from include/linux/kernel.h:12: In file included from include/linux/bitops.h:32: In file included from arch/powerpc/include/asm/bitops.h:62: arch/powerpc/include/asm/barrier.h:49:9: error: '__lwsync' macro redefined [-Werror,-Wmacro-redefined] #define __lwsync() __asm__ __volatile__ (stringify_in_c(LWSYNC) : : :"memory") ^ <built-in>:308:9: note: previous definition is here #define __lwsync __builtin_ppc_lwsync ^ 1 error generated.
Undefine this macro so that the runtime patching introduced by commit 2d1b2027626d ("powerpc: Fixup lwsync at runtime") continues to work properly with clang and the build no longer breaks.
Cc: stable@vger.kernel.org Signed-off-by: Nathan Chancellor nathan@kernel.org Reviewed-by: Nick Desaulniers ndesaulniers@google.com Signed-off-by: Michael Ellerman mpe@ellerman.id.au Link: https://github.com/ClangBuiltLinux/linux/issues/1386 Link: https://github.com/llvm/llvm-project/commit/62b5df7fe2b3fda1772befeda15598fb... Link: https://lore.kernel.org/r/20210528182752.1852002-1-nathan@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/powerpc/include/asm/barrier.h | 2 ++ 1 file changed, 2 insertions(+)
--- a/arch/powerpc/include/asm/barrier.h +++ b/arch/powerpc/include/asm/barrier.h @@ -42,6 +42,8 @@ # define SMPWMB eieio #endif
+/* clang defines this macro for a builtin, which will not work with runtime patching */ +#undef __lwsync #define __lwsync() __asm__ __volatile__ (stringify_in_c(LWSYNC) : : :"memory") #define dma_rmb() __lwsync() #define dma_wmb() __asm__ __volatile__ (stringify_in_c(SMPWMB) : : :"memory")