linux-kernel - Re: [PATCH v4 0/2] Support kexec/kdump for clang built kernel

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Message-ID: <alpine.DEB.2.21.1907260038580.1791@nanos.tec.linutronix.de>
Date:   Fri, 26 Jul 2019 00:51:44 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Nick Desaulniers <ndesaulniers@...gle.com>
cc:     mingo@...hat.com, bp@...en8.de, peterz@...radead.org,
        clang-built-linux@...glegroups.com, linux-kernel@...r.kernel.org,
        yamada.masahiro@...ionext.com
Subject: Re: [PATCH v4 0/2] Support kexec/kdump for clang built kernel

On Thu, 25 Jul 2019, Nick Desaulniers wrote:

I'm really impressed how you manage to make the cover letter (0/N) a reply
to 1/N instead of 1..N/N being a reply to 0/N.

  In-Reply-To: <20190725200625.174838-1-ndesaulniers@...gle.com>
  Message-Id: <20190725200625.174838-3-ndesaulniers@...gle.com>

Is that a new git feature to be $corp top-posting compliant?

> 1. Reuse the implementation of memcpy and memset instead of relying on
> __builtin_memcpy and __builtin_memset as it causes infinite recursion
> in Clang (at any opt level) or GCC at -O2.
> 2. Don't reset KBUILD_CFLAGS, rather filter CONFIG_FUNCTION_TRACER,
> CONFIG_STACKPROTECTOR, and CONFIG_STACKPROTECTOR_STRONG flags via
> `CFLAGS_REMOVE_<file>.o'
> 
> A good test of this series (besides boot testing a kexec kernel):
> * There should be no undefined symbols in arch/x86/purgatory/purgatory.ro:
> $ nm arch/x86/purgatory/purgatory.ro
>   particularly `warn`, `bcmp`, `__stack_chk_fail`, `memcpy` or `memset`.
> * `-pg`, `-fstack-protector`, `-fstack-protector-strong` should not be
>   added to the command line for the c source files under arch/x86/purgatory/
>   when compiling with CONFIG_FUNCTION_TRACER=y, CONFIG_STACKPROTECTOR=y,
>   and CONFIG_STACKPROTECTOR_STRONG=y.
> 
> V4 of: https://lkml.org/lkml/2019/7/23/864

Please don't use lkml.org references. I know it's popular but equally
unreliable at times.

The long term reliable reference is message id based, i.e.:

 lkml.kernel.org/r/$MSGID

or

 lore.kernel.org/lkml/$MSGID

even if the base URLs would cease to exist, the message id will give you a
trivial way to find the relevant thread, but if '2019/7/23/864' stops to
work, good luck in finding the original post. I wasted hours on that just
because a subject line changed enough to confuse the big internet stalking
machines.

Thanks,

	tglx