linux-kernel - Re: [RFC PATCH] kbuild: add -fno-PIE

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Date:   Sat, 29 Oct 2016 19:03:30 +0200
From:   Sven Joachim <svenjoac@....de>
To:     Tomas Janousek <tomi@...i.cz>
Cc:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Joe Perches <joe@...ches.com>,
        Adam Borowski <kilobyte@...band.pl>,
        Michal Marek <mmarek@...e.com>, linux-kbuild@...r.kernel.org,
        linux-kernel@...r.kernel.org, ben@...adent.org.uk
Subject: Re: [RFC PATCH] kbuild: add -fno-PIE

On 2016-10-29 12:10 +0200, Tomas Janousek wrote:

> On Mon, Oct 24, 2016 at 07:32:30PM +0200, Sven Joachim wrote:
>> The attached patch works for me with Debian's gcc-6 package.
>
> I tried your patch when building 4.8.5 on an up-to-date Debian testing and
> still got this:
>
>   AS      arch/x86/entry/vdso/vdso32/note.o
> arch/x86/entry/vdso/vdso32/note.S:1:0: sorry, unimplemented: -mfentry
> isn’t supported for 32-bit in combination with -fpic

I cannot reproduce that, FWIW.  Also, arch/x86/entry/vdso/Makefile seems
to explicitly filter out -mfentry from the compiler flags, but maybe I
misunderstand something.

Could you please show the exact command that's failing with "make V=1"?

> Adding KBUILD_AFLAGS += $(call cc-option,-fno-pie,) helps.
> (Maybe that should be as-option instead. Don't know. There are lots of
> AFLAGS=$(call cc-option, ...) in the Makefiles, anyway.)

This is what Ubuntu is doing, so it works at least for them, I suppose.

Cheers,
       Sven