From: "H. Peter Anvin" <hpa@zytor.com>
To: Nick Desaulniers <ndesaulniers@google.com>, namit@vmware.com
Cc: Nathan Chancellor <natechancellor@gmail.com>,
Thomas Gleixner <tglx@linutronix.de>,
mingo@redhat.com, bp@alien8.de, x86@kernel.org,
LKML <linux-kernel@vger.kernel.org>,
Kees Cook <keescook@chromium.org>,
Masahiro Yamada <yamada.masahiro@socionext.com>
Subject: Re: [PATCH RFC] x86: Don't include '-Wa,-' when building with Clang
Date: Tue, 23 Oct 2018 13:01:22 -0700 [thread overview]
Message-ID: <96ffedd2-a19d-95de-45fd-3a83025dd48a@zytor.com> (raw)
In-Reply-To: <CAKwvOdmsKbW9v9or+u-W9V7T+LrF4ODY9cgUStkjkmsbMcqJ2g@mail.gmail.com>
On 10/23/18 11:40, Nick Desaulniers wrote:
> On Mon, Oct 22, 2018 at 10:11 PM Nadav Amit <namit@vmware.com> wrote:
>>
>> at 5:37 PM, Nathan Chancellor <natechancellor@gmail.com> wrote:
>>
>> Commit 77b0bf55bc67 ("kbuild/Makefile: Prepare for using macros in
>> inline assembly code to work around asm() related GCC inlining bugs")
>> added this flag to KBUILD_CFLAGS, where it works perfectly fine with
>> GCC. However, when building with Clang, all of the object files compile
>> fine but the build hangs indefinitely at init/main.o, right before the
>> linking stage. Don't include this flag when building with Clang.
>>
>> The kernel builds and boots to a shell in QEMU with both GCC and Clang
>> with this patch applied.
>>
>> Link: https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2FClangBuiltLinux%2Flinux%2Fissues%2F213&data=02%7C01%7Cnamit%40vmware.com%7C871daebc2ca44947d28d08d638811fb5%7Cb39138ca3cee4b4aa4d6cd83d9dd62f0%7C1%7C0%7C636758524579997650&sdata=shuxW81QRrO3TSqbgf462wgZYdLeAKeQEdGRxmnUX30%3D&reserved=0
>> Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
>> ---
>>
>> The reason this patch is labeled RFC is while I can verify that this
>> fixes the issue, I'm not entirely sure why the '-Wa,-' works for GCC
>> and not Clang. I looked into what the flag means and I couldn't really
>> find anything so I just assume it's taking input from stdin? The issue
>> could stem from how GCC forks gas versus how Clang does it. If this
>> isn't of concern and the maintainers are happy with this patch as is,
>> feel free to take it.
>>
Perhaps someone could actually, you know, time the build and see how
much -pipe actually matters, if at all?
-hpa
next prev parent reply other threads:[~2018-10-23 20:01 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-23 0:37 [PATCH RFC] x86: Don't include '-Wa,-' when building with Clang Nathan Chancellor
[not found] ` <F3BBC06A-A9CB-4ABF-ADF4-6B0971FAE364@vmware.com>
2018-10-23 18:40 ` Nick Desaulniers
2018-10-23 20:01 ` H. Peter Anvin [this message]
2018-10-23 21:58 ` Nathan Chancellor
2018-10-23 22:04 ` hpa
2018-10-23 22:08 ` Nick Desaulniers
2018-10-23 22:44 ` Nathan Chancellor
2018-10-23 22:53 ` Nick Desaulniers
2018-10-23 23:01 ` hpa
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