Kbuild: do not emit debug info for assembly with LLVM_IAS=1

Clang's integrated assembler produces the warning for assembly files:

warning: DWARF2 only supports one section per compilation unit

If -Wa,-gdwarf-* is unspecified, then debug info is not emitted for
assembly sources (it is still emitted for C sources).  This will be
re-enabled for newer DWARF versions in a follow up patch.

Enables defconfig+CONFIG_DEBUG_INFO to build cleanly with
LLVM=1 LLVM_IAS=1 for x86_64 and arm64.

Cc: <stable@vger.kernel.org>
Link: https://github.com/ClangBuiltLinux/linux/issues/716
Reported-by: Dmitry Golovin <dima@golovin.in>
Reported-by: Nathan Chancellor <natechancellor@gmail.com>
Suggested-by: Dmitry Golovin <dima@golovin.in>
Suggested-by: Nathan Chancellor <natechancellor@gmail.com>
Suggested-by: Sedat Dilek <sedat.dilek@gmail.com>
Reviewed-by: Fangrui Song <maskray@google.com>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

diff --git a/Makefile b/Makefile
index 87d659d3c8de9784703329dfa48afbf7e74b919f..ae1592c1f5d6feb3afdd20c4bd77e2d560c6f4b0 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -828,7 +828,9 @@ else
 DEBUG_CFLAGS   += -g
 endif
 
+ifneq ($(LLVM_IAS),1)
 KBUILD_AFLAGS  += -Wa,-gdwarf-2
+endif
 
 ifdef CONFIG_DEBUG_INFO_DWARF4
 DEBUG_CFLAGS   += -gdwarf-4