linux-kernel - Re: [PATCH v3] x86/boot: clean up headers

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Date:   Mon, 4 Mar 2019 16:15:49 -0800
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Nathan Chancellor <natechancellor@...il.com>,
        Nirav Davé <niravd@...gle.com>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] x86/boot: clean up headers

On Mon, Mar 4, 2019 at 4:12 PM Nick Desaulniers <ndesaulniers@...gle.com> wrote:
>
> The inclusion of <linux/kernel.h> was causing issue as the definition of
> __arch_hweight64 from arch/x86/include/asm/arch_hweight.h eventually gets
> included. The definition is problematic when compiled with -m16 (all code
> in arch/x86/boot/ is) as the "D" inline assembly constraint is rejected
> by both compilers when passed an argument of type long long (regardless
> of signedness, anything smaller is fine).
>
> Because GCC performs inlining before semantic analysis, and
> __arch_hweight64 is dead in this translation unit, GCC does not report
> any issues at compile time.  Clang does the semantic analysis in the
> front end, before inlining (run in the middle) can determine the code is
> dead. I consider this another case of PR33587, which I think we can do
> more work to solve.
>
> It turns out that arch/x86/boot/string.c doesn't actually need
> linux/kernel.h, simply linux/limits.h and linux/compiler.h. Include them,
> and sort the headers alphabetically.

Well, should have cut that out of the commit message too in V3...sigh.
Boris assuming everyone's ok with this patch; can you just drop this
sentence from the commit message should you apply the patch (or shall
I send a v4)?

>
> Link: https://bugs.llvm.org/show_bug.cgi?id=33587
> Link: https://github.com/ClangBuiltLinux/linux/issues/347
> Reviewed-by: Nathan Chancellor <natechancellor@...il.com>
> Tested-by: Nathan Chancellor <natechancellor@...il.com>
> Suggested-by: Stephen Rothwell <sfr@...b.auug.org.au>
> Signed-off-by: Nick Desaulniers <ndesaulniers@...gle.com>
> ---
> Changes V2 -> V3:
> * keep linux/types.h
>
> Changes V1 -> V2:
> * Add Reviewed, Tested, Suggested tags.
> * Drop linux/types.h; it's included in linux/limits.h.
>
>  arch/x86/boot/string.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/boot/string.c b/arch/x86/boot/string.c
> index 315a67b8896b..90154df8f125 100644
> --- a/arch/x86/boot/string.c
> +++ b/arch/x86/boot/string.c
> @@ -13,8 +13,9 @@
>   */
>
>  #include <linux/types.h>
> -#include <linux/kernel.h>
> +#include <linux/compiler.h>
>  #include <linux/errno.h>
> +#include <linux/limits.h>
>  #include <asm/asm.h>
>  #include "ctype.h"
>  #include "string.h"
> --
> 2.21.0.352.gf09ad66450-goog
>


-- 
Thanks,
~Nick Desaulniers