linux-kernel - Re: Clang patch stacks for LTS kernels (v4.4 and v4.9) and status update

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Message-ID: <CA+icZUWjKDgg+-EJ8dyw-r4A+O_iMLPEBk2aKhTWO9_0Em_s4A@mail.gmail.com>
Date:   Tue, 22 May 2018 09:11:54 +0200
From:   Sedat Dilek <sedat.dilek@...il.com>
To:     Nick Desaulniers <nick.desaulniers@...il.com>
Cc:     Matthias Kaehlcke <mka@...omium.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Manoj Gupta <manojgupta@...omium.org>,
        AlistairStrachan <astrachan@...gle.com>,
        "Steven Rostedt (VMware)" <rostedt@...dmis.org>
Subject: Re: Clang patch stacks for LTS kernels (v4.4 and v4.9) and status update

On Sat, May 19, 2018 at 12:54 AM, Nick Desaulniers
<nick.desaulniers@...il.com> wrote:
> Sedat,
> Thanks for the report.  We have a fix ready in
> https://bugs.llvm.org/show_bug.cgi?id=37512.  Can you report what
> version of clang you were using and if earlier versions of clang have
> this issue?
> Thanks,

Hi Nick,

yesterday was public holiday in Germany, so I answer today.

These are really good news, Thanks.

For my recent experiments with Linux-kernel v4.14.y LTS I used Clang...

#1: version 6.0 from Debian/testing repositories
#2: version 7 (svn330207) from <apt-llvm.org>

In these cases I had success (good means boot on bare metal) or it
failed (bad verified in Qemu):

bad: CONFIG_PARAVIRT=y and  CONFIG_CC_STACKPROTECTOR_STRONG=y
good: CONFIG_PARAVIRT=n and CONFIG_CC_STACKPROTECTOR_STRONG=y
good: CONFIG_PARAVIRT=y and CONFIG_CC_STACKPROTECTOR_NONE=y

So, the issue is in both Clang versions and I appreciate to have your
fix in LLVM/Clang version 6.0.1 as I don't know which version will get
into upcoming Debian/buster (version 10, current status: testing).

Hope this helps.

Regards,
- Sedat -