From: Nick Desaulniers <ndesaulniers@google.com>
To: yamada.masahiro@socionext.com
Cc: keescook@chromium.org, clang-built-linux@googlegroups.com,
Nick Desaulniers <ndesaulniers@google.com>,
Nathan Chancellor <natechancellor@gmail.com>,
Michal Marek <michal.lkml@markovi.net>,
linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH v4] Makefile: lld: tell clang to use lld
Date: Tue, 2 Apr 2019 00:33:17 -0700 [thread overview]
Message-ID: <20190402073317.56529-1-ndesaulniers@google.com> (raw)
In-Reply-To: <20190402072726.GA16650@archlinux-ryzen>
This is needed because clang doesn't select which linker to use based on
$LD but rather -fuse-ld={bfd,gold,lld,<absolute path to linker>}. 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 <natechancellor@gmail.com>
Suggested-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
---
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
next prev parent reply other threads:[~2019-04-02 7:33 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-11 19:30 [PATCH v2 1/4] init/Kconfig: add config support for detecting linker ndesaulniers
2019-02-11 19:30 ` [PATCH v2 2/4] Makefile: clang: choose GCC_TOOLCHAIN_DIR not on LD ndesaulniers
2019-02-16 3:02 ` Masahiro Yamada
2019-02-11 19:30 ` [PATCH v2 3/4] Makefile: lld: tell clang to use lld ndesaulniers
2019-02-13 14:58 ` Masahiro Yamada
2019-02-13 17:41 ` Nick Desaulniers
2019-02-16 3:07 ` Masahiro Yamada
2019-04-02 3:54 ` Nick Desaulniers
2019-04-02 4:49 ` Masahiro Yamada
2019-04-02 7:08 ` [PATCH v3] " Nick Desaulniers
2019-04-02 7:27 ` Nathan Chancellor
2019-04-02 7:33 ` Nick Desaulniers [this message]
2019-04-02 7:57 ` [PATCH v4] " Nathan Chancellor
2019-04-02 7:52 ` [PATCH v3] " Sedat Dilek
2019-04-02 7:56 ` Nathan Chancellor
2019-04-05 10:16 ` Masahiro Yamada
2019-04-05 16:11 ` Kees Cook
2019-04-05 16:52 ` Nick Desaulniers
2019-04-07 2:20 ` Masahiro Yamada
2019-02-11 19:30 ` [PATCH v2 4/4] Makefile: lld: set -O2 linker flag when linking with LLD ndesaulniers
2019-02-12 12:22 ` Peter Zijlstra
2019-02-16 2:55 ` Masahiro Yamada
2019-02-11 19:30 ` [PATCH v2 0/4] Improve kernel LLD support ndesaulniers
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