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Date: Mon, 9 Jul 2018 11:29:45 -0700
From: Guenter Roeck <linux@roeck-us.net>
Subject: Re: Build/qemu test results for v4.18-rc4
Message-ID: <20180709182945.GA31159@roeck-us.net>
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To: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Kees Cook <keescook@chromium.org>, LKML <linux-kernel@vger.kernel.org>, Masahiro Yamada <yamada.masahiro@socionext.com>, Linus Torvalds <torvalds@linux-foundation.org>, Martin Schwidefsky <schwidefsky@de.ibm.com>, linux-s390 <linux-s390@vger.kernel.org>
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On Mon, Jul 09, 2018 at 08:16:04PM +0200, Christian Borntraeger wrote:
> 
> 
> On 07/09/2018 08:06 PM, Kees Cook wrote:
> > On Mon, Jul 9, 2018 at 10:55 AM, Guenter Roeck <linux@roeck-us.net> wrote:
> >> s390:allmodconfig:
> >>
> >> arch/s390/kernel/als.o: In function `verify_facilities':
> >> als.c:(.init.text+0x24): undefined reference to `latent_entropy'
> >> als.c:(.init.text+0xae): undefined reference to `latent_entropy'
> >> make[3]: *** [arch/s390/boot/compressed/vmlinux] Error 1
> >> make[2]: *** [arch/s390/boot/compressed/vmlinux] Error 2
> >> make[1]: *** [bzImage] Error 2
> >>
> >> This problem is only seen when using a compiler which has the relevant
> >> plugins enabled. Bisect points to commit 1658dcee3d43ed ("gcc-plugins:
> >> allow to enable GCC_PLUGINS for COMPILE_TEST") as the culprit. I don't
> >> know if a fix for v4.18 has been submitted. The s390 boot code in -next
> >> has been rearranged and the problem is no longer seen there.
> > 
> > Hm, that would imply that mm/page_alloc.o wasn't visible during the
> > als.o linking? But ... if the problem is gone, I guess... good?
> 
> als.o is used to detect if the kernel was compiled for a newer generation
> than the hardware that we are running on (very early). So it is compiled
> without gcov, kcov,ubsan and with a different march -in other words special.
> In linux-next we moved the als part to the decompressor which avoids all
> these kind of special handling. As this is part of a bigger patch set it 
> would be  non-trivial to backport that for 4.18.
> So unless we want to have it fixed for 4.18 I think we are fine.
> 

Fine with me. Please let me know if the problem won't be fixed, and I'll
disable allmodconfig test builds for s390 images in v4.18.

Thanks,
Guenter