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From: "H. Peter Anvin" <hpa@zytor.com>
To: ndesaulniers@google.com, bp@alien8.de, mingo@redhat.com,
	tglx@linutronix.de
Cc: x86@kernel.org,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	Masahiro Yamada <yamada.masahiro@socionext.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Matthias Kaehlcke <mka@chromium.org>,
	Kees Cook <keescook@chromium.org>,
	Cao jin <caoj.fnst@cn.fujitsu.com>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] x86/boot: define CC_HAVE_ASM_GOTO
Date: Mon, 1 Oct 2018 10:38:33 -0700	[thread overview]
Message-ID: <d98d47ea-b639-8afd-2851-1f7ceaf66fd0@zytor.com> (raw)
In-Reply-To: <20180927204800.32210-1-ndesaulniers@google.com>

On 09/27/18 13:47, ndesaulniers@google.com wrote:
> Early prototypes of Clang with asm goto support produce 6 instances of
> the following warning:
> 
> In file included from arch/x86/boot/compressed/misc.h:20:
> In file included from ./include/linux/elf.h:5:
> In file included from ./arch/x86/include/asm/elf.h:8:
> In file included from ./include/linux/thread_info.h:38:
> In file included from ./arch/x86/include/asm/thread_info.h:53:
> ./arch/x86/include/asm/cpufeature.h:150:2: warning: "Compiler lacks
> ASM_GOTO support. Add -D __BPF_TRACING__ to your compiler arguments"
> [-W#warnings]
> your compiler arguments"
>  ^
> 
> Since 6 files under arch/x86/boot/compressed/ include
> arch/x86/boot/compressed/misc.h AND
> arch/x86/boot/compressed/Makefile happens to redefine KBUILD_CFLAGS,
> which set these variables in the top level MAKEFILE.
> 

The Right Thing[TM] would probably be to split the CFLAGS into those
that are independent of x86_64 vs i386. After all, there is no
fundamental reason we couldn't want to use asm goto in the setup or
real-mode code in the future.  In addition to BIOS entry code there is
the EFI32 code.

	-hpa

      parent reply	other threads:[~2018-10-01 17:39 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-09-27 20:47 [PATCH v2] x86/boot: define CC_HAVE_ASM_GOTO ndesaulniers
2018-09-27 21:40 ` Kees Cook
2018-09-27 21:51 ` Borislav Petkov
2018-09-27 22:17   ` Nick Desaulniers
2018-10-01 17:32     ` Borislav Petkov
2018-10-01 17:38 ` H. Peter Anvin [this message]

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