From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-it1-f202.google.com ([209.85.166.202]:35130 "EHLO mail-it1-f202.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728999AbfDBHd0 (ORCPT ); Tue, 2 Apr 2019 03:33:26 -0400 Received: by mail-it1-f202.google.com with SMTP id a64so2042159ith.0 for ; Tue, 02 Apr 2019 00:33:26 -0700 (PDT) Date: Tue, 2 Apr 2019 00:33:17 -0700 In-Reply-To: <20190402072726.GA16650@archlinux-ryzen> Message-Id: <20190402073317.56529-1-ndesaulniers@google.com> Mime-Version: 1.0 References: <20190402072726.GA16650@archlinux-ryzen> Subject: [PATCH v4] Makefile: lld: tell clang to use lld From: Nick Desaulniers Content-Type: text/plain; charset="UTF-8" Sender: linux-kbuild-owner@vger.kernel.org List-ID: To: yamada.masahiro@socionext.com Cc: keescook@chromium.org, clang-built-linux@googlegroups.com, Nick Desaulniers , Nathan Chancellor , Michal Marek , linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org This is needed because clang doesn't select which linker to use based on $LD but rather -fuse-ld={bfd,gold,lld,}. This is problematic especially for cc-ldoption, which checks for linker flag support via invoking the compiler, rather than the linker. Select the linker via absolute path from $PATH via `which`. This allows you to build with: $ make LD=ld.lld $ make LD=ld.lld-8 $ make LD=/path/to/ld.lld Add -Qunused-arguments to KBUILD_CPPFLAGS sooner, as otherwise Clang likes to complain about -fuse-lld= being unused when compiling but not linking (-c) such as when cc-option is used. There's no need to guard with cc-option. Link: https://github.com/ClangBuiltLinux/linux/issues/342 Link: https://github.com/ClangBuiltLinux/linux/issues/366 Link: https://github.com/ClangBuiltLinux/linux/issues/357 Suggested-by: Nathan Chancellor Suggested-by: Masahiro Yamada Signed-off-by: Nick Desaulniers --- Changes V3->V4: * Unconditionally add -Qunused-arguments sooners, as per Nathan. * Slight modification to commit message for that point. Changes V2->V3: * Use absolute path based on `which $LD` as per Masahiro. * Add -Qunused-arguments. * Drop tested-by/reviewed-by tags, since this patched has changed enough to warrant re-testing/re-review, IMO. * Add more info to the commit message. Changes V1->V2: * add reviewed and tested by tags. * move this addition up 2 statments so that it's properly added to KBUILD_*FLAGS as per Nathan. Makefile | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/Makefile b/Makefile index 026fbc450906..b290e76e1ca5 100644 --- a/Makefile +++ b/Makefile @@ -514,6 +514,10 @@ ifneq ($(GCC_TOOLCHAIN),) CLANG_FLAGS += --gcc-toolchain=$(GCC_TOOLCHAIN) endif CLANG_FLAGS += -no-integrated-as +ifneq ($(shell $(LD) --version 2>&1 | head -n 1 | grep LLD),) +CLANG_FLAGS += -fuse-ld=$(shell which $(LD)) +endif +KBUILD_CPPFLAGS += -Qunused-arguments KBUILD_CFLAGS += $(CLANG_FLAGS) KBUILD_AFLAGS += $(CLANG_FLAGS) export CLANG_FLAGS @@ -716,7 +720,6 @@ stackp-flags-$(CONFIG_STACKPROTECTOR_STRONG) := -fstack-protector-strong KBUILD_CFLAGS += $(stackp-flags-y) ifdef CONFIG_CC_IS_CLANG -KBUILD_CPPFLAGS += $(call cc-option,-Qunused-arguments,) KBUILD_CFLAGS += $(call cc-disable-warning, format-invalid-specifier) KBUILD_CFLAGS += $(call cc-disable-warning, gnu) KBUILD_CFLAGS += $(call cc-disable-warning, address-of-packed-member) -- 2.21.0.392.gf8f6787159e-goog