linux-kernel - Re: Build regressions/improvements in v4.3-rc7

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Date:	Sun, 25 Oct 2015 18:38:18 +0100
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
Cc:	Rabin Vincent <rabin@....in>, Kees Cook <keescook@...omium.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: Build regressions/improvements in v4.3-rc7

On Sun, Oct 25, 2015 at 3:08 PM, Russell King - ARM Linux
<linux@....linux.org.uk> wrote:
> On Sun, Oct 25, 2015 at 11:39:15AM +0100, Geert Uytterhoeven wrote:
>> On Sun, Oct 25, 2015 at 11:18 AM, Geert Uytterhoeven
>> <geert@...ux-m68k.org> wrote:
>> > On Sun, Oct 25, 2015 at 11:12 AM, Geert Uytterhoeven
>> > <geert@...ux-m68k.org> wrote:
>> >> JFYI, when comparing v4.3-rc7[1] to v4.3-rc6[3], the summaries are:
>> >>   - build errors: +12/-4
>>
>> >   + /home/kisskb/slave/src/arch/arm/kernel/patch.c: error: 'L_PTE_DIRTY' undeclared (first use in this function):  => 39:2
>> >   + /home/kisskb/slave/src/arch/arm/kernel/patch.c: error: 'L_PTE_MT_WRITEBACK' undeclared (first use in this function):  => 39:2
>> >   + /home/kisskb/slave/src/arch/arm/kernel/patch.c: error: 'L_PTE_PRESENT' undeclared (first use in this function):  => 39:2
>> >   + /home/kisskb/slave/src/arch/arm/kernel/patch.c: error: 'L_PTE_XN' undeclared (first use in this function):  => 39:2
>> >   + /home/kisskb/slave/src/arch/arm/kernel/patch.c: error: 'L_PTE_YOUNG' undeclared (first use in this function):  => 39:2
>>
>> Caused by:
>>
>> commit ab0615e2d6fb074764a3e4d05f1326fa2fdb4627
>> Author: Rabin Vincent <rabin@....in>
>> Date:   Thu Apr 24 23:28:57 2014 +0200
>>
>>     arm: use fixmap for text patching when text is RO
>>
>> Should the call to set_fixmap() in arch/arm/kernel/patch.c
>> just be protected by #ifdef CONFIG_MMU?
>
> What this shows, time and time again, is that we need better testing for
> !MMU platforms - we need !MMU platforms in the mainline kernel which
> people actually have.
>
> I have an OKI 67001 board (from Simtec), which is the older generation of
> !MMU system, and I have code for it, but arm-soc won't let me put it in
> the mainline kernel - even though it would give me a platform which I can
> add to the boot farm to build and boot a test kernel for.
>
> Consequently, I've little motivation to catch !MMU regressions before
> they hit mainline.
>
> Should we accept old !MMU code into mainline for platforms which kernel
> developers have, in order to aid testing, even though it isn't modern
> platforms and doesn't conform to the latest way of doing stuff.

I think we should have at least one arm-nommu platform in the upstream kernel,
with a suitable defconfig, so 0build will catch regressions.

Alternative, can any of the existing supported arm-mmu platform be used with
a nommu kernel?

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
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