linux-kernel - Re: linux-next: build failure after merge of the kspp tree

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Date:   Fri, 27 Jul 2018 14:01:06 +0100
From:   Will Deacon <will.deacon@....com>
To:     Stephen Rothwell <sfr@...b.auug.org.au>
Cc:     Kees Cook <keescook@...gle.com>,
        Linux-Next Mailing List <linux-next@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Alexander Popov <alex.popov@...ux.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Laura Abbott <labbott@...hat.com>
Subject: Re: linux-next: build failure after merge of the kspp tree

On Fri, Jul 27, 2018 at 01:55:22PM +0100, Will Deacon wrote:
> On Fri, Jul 27, 2018 at 08:55:11PM +1000, Stephen Rothwell wrote:
> > On Fri, 27 Jul 2018 19:06:47 +1000 Stephen Rothwell <sfr@...b.auug.org.au> wrote:
> > >
> > > On Fri, 27 Jul 2018 19:02:07 +1000 Stephen Rothwell <sfr@...b.auug.org.au> wrote:
> > > >
> > > > After merging the kspp tree, today's linux-next build (x86_64
> > > > allmodconfig) failed like this:
> > > > 
> > > > cc1: error: plugin stackleak_plugin should be specified before -fplugin-arg-stackleak_plugin-disable in the command line
> > > > 
> > > > Maybe caused by commit
> > > > 
> > > >   a8b9eaddb9c0 ("gcc-plugins: Add STACKLEAK plugin for tracking the kernel stack")
> > > > 
> > > > I have used the kspp tree from next-20180726 for today.  
> > > 
> > > Well, that obviously didn't work since the tree hasn't changed for a
> > > few days.
> > > 
> > > I can't see what has interacted to make this happen, so I have dropped
> > > the kspp tree for today.
> > 
> > Actually, it may have been caused by commit
> > 
> >   0b3e336601b8 ("arm64: Add support for STACKLEAK gcc plugin")
> > 
> > from the arm64 tree.
> 
> Thanks, Stephen. I managed to reproduce this by merging for-next/kspp from
> Kees's tree and for-next/core from the arm64 tree. The failure happens when
> building the EFI stub, so the commit you mention above is almost certainly
> the culprit.
> 
> We build the stub with the following GCC invocation:
> 
>  gcc -Wp,-MD,drivers/firmware/efi/libstub/.efi-stub-helper.o.d  -nostdinc -isystem /usr/lib/gcc/x86_64-linux-gnu/4.9/include -I./arch/x86/include -I./arch/x86/include/generated  -I./include -I./arch/x86/include/uapi -I./arch/x86/include/generated/uapi -I./include/uapi -I./include/generated/uapi -include ./include/linux/kconfig.h -include ./include/linux/compiler_types.h -D__KERNEL__ -mcmodel=small -m64 -D__KERNEL__ -O2 -fPIC -fno-strict-aliasing -mno-red-zone -mno-mmx -mno-sse -fshort-wchar -DDISABLE_BRANCH_PROFILING -D__NO_FORTIFY -ffreestanding -fno-stack-protector -fplugin-arg-stackleak_plugin-disable   -fno-builtin      -DKBUILD_BASENAME='"efi_stub_helper"' -DKBUILD_MODNAME='"efi_stub_helper"' -c -o drivers/firmware/efi/libstub/.tmp_efi-stub-helper.o drivers/firmware/efi/libstub/efi-stub-helper.c
> 
> so given that we're not passing any -fplugin= option anyway (because we
> override KBUILD_CFLAGS for the stub), I don't understand why we need
> to the disable option at all.
> 
> Laura?

... ah, but arm and arm64 inherit the old KBUILD_CFLAGS via the
cflags-$(CONFIG_ARM64) and cflags-$(CONFIG_ARM) definitions, so they
would be the places where we need to disable the plugin.

Will