From 8cc4fd73501d9f1370c3eebb70cfe8cc9e24062b Mon Sep 17 00:00:00 2001 From: Masahiro Yamada Date: Tue, 10 Mar 2020 19:12:49 +0900 Subject: kconfig: introduce m32-flag and m64-flag When a compiler supports multiple architectures, some compiler features can be dependent on the target architecture. This is typical for Clang, which supports multiple LLVM backends. Even for GCC, we need to take care of biarch compiler cases. It is not a problem when we evaluate cc-option in Makefiles because cc-option is tested against the flag in question + $(KBUILD_CFLAGS). The cc-option in Kconfig, on the other hand, does not accumulate tested flags. Due to this simplification, it could potentially test cc-option against a different target. At first, Kconfig always evaluated cc-option against the host architecture. Since commit e8de12fb7cde ("kbuild: Check for unknown options with cc-option usage in Kconfig and clang"), in case of cross-compiling with Clang, the target triple is correctly passed to Kconfig. The case with biarch GCC (and native build with Clang) is still not handled properly. We need to pass some flags to specify the target machine bit. Due to the design, all the macros in Kconfig are expanded in the parse stage, where we do not know the target bit size yet. For example, arch/x86/Kconfig allows a user to toggle CONFIG_64BIT. If a compiler flag -foo depends on the machine bit, it must be tested twice, one with -m32 and the other with -m64. However, -m32/-m64 are not always recognized. So, this commits adds m64-flag and m32-flag macros. They expand to -m32, -m64, respectively if supported. Or, they expand to an empty string if unsupported. The typical usage is like this: config FOO bool default $(cc-option,$(m64-flag) -foo) if 64BIT default $(cc-option,$(m32-flag) -foo) This is clumsy, but there is no elegant way to handle this in the current static macro expansion. There was discussion for static functions vs dynamic functions. The consensus was to go as far as possible with the static functions. (https://lkml.org/lkml/2018/3/2/22) Signed-off-by: Masahiro Yamada Tested-by: George Spelvin Reviewed-by: Nathan Chancellor --- scripts/Kconfig.include | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'scripts/Kconfig.include') diff --git a/scripts/Kconfig.include b/scripts/Kconfig.include index 85334dc8c997..496d11c92c97 100644 --- a/scripts/Kconfig.include +++ b/scripts/Kconfig.include @@ -44,3 +44,10 @@ $(error-if,$(success, $(LD) -v | grep -q gold), gold linker '$(LD)' not supporte # gcc version including patch level gcc-version := $(shell,$(srctree)/scripts/gcc-version.sh $(CC)) + +# machine bit flags +# $(m32-flag): -m32 if the compiler supports it, or an empty string otherwise. +# $(m64-flag): -m64 if the compiler supports it, or an empty string otherwise. +cc-option-bit = $(if-success,$(CC) -Werror $(1) -E -x c /dev/null -o /dev/null,$(1)) +m32-flag := $(cc-option-bit,-m32) +m64-flag := $(cc-option-bit,-m64) -- cgit v1.2.3 From c2d920bf1fffc3a61cb77db24464caf39496b32d Mon Sep 17 00:00:00 2001 From: Vincenzo Frascino Date: Fri, 13 Mar 2020 14:35:02 +0530 Subject: kconfig: Add support for 'as-option' Currently kconfig does not have a feature that allows to detect if the used assembler supports a specific compilation option. Introduce 'as-option' to serve this purpose in the context of Kconfig: config X def_bool $(as-option,...) Signed-off-by: Amit Daniel Kachhap Signed-off-by: Vincenzo Frascino Acked-by: Masahiro Yamada Cc: linux-kbuild@vger.kernel.org Cc: Masahiro Yamada Signed-off-by: Catalin Marinas --- scripts/Kconfig.include | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'scripts/Kconfig.include') diff --git a/scripts/Kconfig.include b/scripts/Kconfig.include index 85334dc8c997..a1c19255a030 100644 --- a/scripts/Kconfig.include +++ b/scripts/Kconfig.include @@ -31,6 +31,12 @@ cc-option = $(success,$(CC) -Werror $(CLANG_FLAGS) $(1) -S -x c /dev/null -o /de # Return y if the linker supports , n otherwise ld-option = $(success,$(LD) -v $(1)) +# $(as-option,) +# /dev/zero is used as output instead of /dev/null as some assembler cribs when +# both input and output are same. Also both of them have same write behaviour so +# can be easily substituted. +as-option = $(success, $(CC) $(CLANG_FLAGS) $(1) -c -x assembler /dev/null -o /dev/zero) + # $(as-instr,) # Return y if the assembler supports , n otherwise as-instr = $(success,printf "%b\n" "$(1)" | $(CC) $(CLANG_FLAGS) -c -x assembler -o /dev/null -) -- cgit v1.2.3 From 77342a02ff6e14645916d85c8550dd1011c4f7d7 Mon Sep 17 00:00:00 2001 From: Masahiro Yamada Date: Sun, 29 Mar 2020 20:08:32 +0900 Subject: gcc-plugins: drop support for GCC <= 4.7 Nobody was opposed to raising minimum GCC version to 4.8 [1] So, we will drop GCC <= 4.7 support sooner or later. We always use C++ compiler for building plugins for GCC >= 4.8. This commit drops the plugin support for GCC <= 4.7 a bit earlier, which allows us to dump lots of code. [1] https://lkml.org/lkml/2020/1/23/545 Signed-off-by: Masahiro Yamada Acked-by: Kees Cook --- scripts/Kconfig.include | 3 --- 1 file changed, 3 deletions(-) (limited to 'scripts/Kconfig.include') diff --git a/scripts/Kconfig.include b/scripts/Kconfig.include index 8074f14d9d0d..c264da2b9b30 100644 --- a/scripts/Kconfig.include +++ b/scripts/Kconfig.include @@ -48,9 +48,6 @@ $(error-if,$(failure,command -v $(LD)),linker '$(LD)' not found) # Fail if the linker is gold as it's not capable of linking the kernel proper $(error-if,$(success, $(LD) -v | grep -q gold), gold linker '$(LD)' not supported) -# gcc version including patch level -gcc-version := $(shell,$(srctree)/scripts/gcc-version.sh $(CC)) - # machine bit flags # $(m32-flag): -m32 if the compiler supports it, or an empty string otherwise. # $(m64-flag): -m64 if the compiler supports it, or an empty string otherwise. -- cgit v1.2.3