linux-kernel - Re: [PATCH 1/3] powerpc: boot: include compiler

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Message-ID: <20201117030158.GA1340689@ubuntu-m3-large-x86>
Date:   Mon, 16 Nov 2020 20:01:58 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     "Gustavo A . R . Silva" <gustavoars@...nel.org>,
        Miguel Ojeda <miguel.ojeda.sandonis@...il.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        clang-built-linux@...glegroups.com, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] powerpc: boot: include compiler_attributes.h

On Sun, Nov 15, 2020 at 08:35:30PM -0800, Nick Desaulniers wrote:
> The kernel uses `-include` to include include/linux/compiler_types.h
> into all translation units (see scripts/Makefile.lib), which #includes
> compiler_attributes.h.
> 
> arch/powerpc/boot/ uses different compiler flags from the rest of the
> kernel. As such, it doesn't contain the definitions from these headers,
> and redefines a few that it needs.
> 
> For the purpose of enabling -Wimplicit-fallthrough for ppc, include
> compiler_types.h via `-include`.
> 
> Link: https://github.com/ClangBuiltLinux/linux/issues/236
> Signed-off-by: Nick Desaulniers <ndesaulniers@...gle.com>

Reviewed-by: Nathan Chancellor <natechancellor@...il.com>
Tested-by: Nathan Chancellor <natechancellor@...il.com>

> ---
> We could just `#include "include/linux/compiler_types.h"` in the few .c
> sources used from lib/ (there are proper header guards in
> compiler_types.h).
> 
> It was also noted in 6a9dc5fd6170 that we could -D__KERNEL__ and
> -include compiler_types.h like the main kernel does, though testing that
> produces a whole sea of warnings to cleanup. This approach is minimally
> invasive.
> 
>  arch/powerpc/boot/Makefile     | 1 +
>  arch/powerpc/boot/decompress.c | 1 -
>  2 files changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/powerpc/boot/Makefile b/arch/powerpc/boot/Makefile
> index f8ce6d2dde7b..1659963a8f1d 100644
> --- a/arch/powerpc/boot/Makefile
> +++ b/arch/powerpc/boot/Makefile
> @@ -31,6 +31,7 @@ endif
>  BOOTCFLAGS    := -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs \
>  		 -fno-strict-aliasing -O2 -msoft-float -mno-altivec -mno-vsx \
>  		 -pipe -fomit-frame-pointer -fno-builtin -fPIC -nostdinc \
> +		 -include $(srctree)/include/linux/compiler_attributes.h \
>  		 $(LINUXINCLUDE)
>  
>  ifdef CONFIG_PPC64_BOOT_WRAPPER
> diff --git a/arch/powerpc/boot/decompress.c b/arch/powerpc/boot/decompress.c
> index 8bf39ef7d2df..6098b879ac97 100644
> --- a/arch/powerpc/boot/decompress.c
> +++ b/arch/powerpc/boot/decompress.c
> @@ -21,7 +21,6 @@
>  
>  #define STATIC static
>  #define INIT
> -#define __always_inline inline
>  
>  /*
>   * The build process will copy the required zlib source files and headers
> -- 
> 2.29.2.299.gdc1121823c-goog
>