linux-kernel - Re: [patch core/stackprotector] stackprotector: Fix build when compiler lacks support

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Date:	Wed, 1 Jan 2014 11:33:38 -0800
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	"Yann E. MORIN" <yann.morin.1998@...e.fr>
Cc:	Kees Cook <keescook@...omium.org>,
	David Rientjes <rientjes@...gle.com>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Ralf Baechle <ralf@...ux-mips.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	James Hogan <james.hogan@...tec.com>,
	Michal Marek <mmarek@...e.cz>,
	Paul Mundt <lethal@...ux-sh.org>,
	Shawn Guo <shawn.guo@...aro.org>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	linux-kbuild <linux-kbuild@...r.kernel.org>,
	Sam Ravnborg <sam@...nborg.org>,
	"linux-tip-commits@...r.kernel.org" 
	<linux-tip-commits@...r.kernel.org>
Subject: Re: [patch core/stackprotector] stackprotector: Fix build when
 compiler lacks support

On Wed, Jan 1, 2014 at 3:42 AM, Yann E. MORIN <yann.morin.1998@...e.fr> wrote:
>
> On 2013-12-31 16:16 -0800, Linus Torvalds spake thusly:
>>
>> What we really really want to do is to have some way to add config
>> options based on shell scripts and compiler support. That would also
>> get rid of a lot of Makefile trickery etc.
>>
>> Then we could just make CC_STACKPROTECTOR_STRONG depend on
>> CC_SUPPORTS_STACKPROTECTOR_STRONG or whatever.
>
> Sam Ravnborg suggested somethink along those lines back in July:
>     http://marc.info/?l=linux-kbuild&m=137399785206527&w=2
> and a tentative implementation:
>     http://marc.info/?l=linux-kbuild&m=137409581406434&w=2

Ack. Looks good to me. I've wanted this for a long time for other
reasons, we should finally just do it.

That said, we should make sure that the shell execution thing gets
access to $(CC) etc variables that we have in

> Basically, that would give something like:
>
>     config CC_SUPPORTS_STACKPROTECTOR_STRONG
>         bool
>         option exec="some/script/to/test-gcc -fstack-protector-strong"

For the compiler options, it would hopefully be sufficient to just do
something like

  config CC_SUPPORTS_STACKPROTECTOR_STRONG
      bool
      option exec="$CC -fstack-protector-strong -c empty.c"

or something like that. No?

              Linus
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