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From:   Thiago Jung Bauermann <bauerman@linux.ibm.com>
To:     Mimi Zohar <zohar@linux.ibm.com>
Cc:     Rob Herring <robh@kernel.org>,
        Lakshmi Ramasubramanian <nramas@linux.microsoft.com>,
        "AKASHI, Takahiro" <takahiro.akashi@linaro.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Will Deacon <will@kernel.org>, Joe Perches <joe@perches.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
        "Michael Ellerman" <mpe@ellerman.id.au>,
        Stephen Rothwell <sfr@canb.auug.org.au>,
        James Morse <james.morse@arm.com>,
        Sasha Levin <sashal@kernel.org>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        linux-integrity@vger.kernel.org,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
        devicetree@vger.kernel.org,
        linuxppc-dev <linuxppc-dev@lists.ozlabs.org>
Subject: Re: [PATCH] of: error: 'const struct kimage' has no member named
 'arch'
In-reply-to: <6a197963deb8e44c71384ea9b89d7f3f13c947bf.camel@linux.ibm.com>
Date:   Fri, 19 Feb 2021 15:09:54 -0300
Message-ID: <87blcgx72l.fsf@manicouagan.localdomain>
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Mimi Zohar <zohar@linux.ibm.com> writes:

> On Fri, 2021-02-19 at 11:43 -0600, Rob Herring wrote:
>> On Fri, Feb 19, 2021 at 10:57 AM Lakshmi Ramasubramanian
>> <nramas@linux.microsoft.com> wrote:
>> >
>> > On 2/19/21 6:16 AM, Rob Herring wrote:
>> > > On Thu, Feb 18, 2021 at 8:53 PM Lakshmi Ramasubramanian
>> > > <nramas@linux.microsoft.com> wrote:
>> > >>
>> > >> On 2/18/21 5:13 PM, Thiago Jung Bauermann wrote:
>> > >>>
>> > >>> Lakshmi Ramasubramanian <nramas@linux.microsoft.com> writes:
>> > >>>
>> > >>>> On 2/18/21 4:07 PM, Mimi Zohar wrote:
>> > >>>>
>> > >>>> Hi Mimi,
>> > >>>>
>> > >>>>> On Thu, 2021-02-18 at 14:33 -0800, Lakshmi Ramasubramanian wrote:
>> > >>>>>> of_kexec_alloc_and_setup_fdt() defined in drivers/of/kexec.c builds
>> > >>>>>> a new device tree object that includes architecture specific data
>> > >>>>>> for kexec system call.  This should be defined only if the architecture
>> > >>>>>> being built defines kexec architecture structure "struct kimage_arch".
>> > >>>>>>
>> > >>>>>> Define a new boolean config OF_KEXEC that is enabled if
>> > >>>>>> CONFIG_KEXEC_FILE and CONFIG_OF_FLATTREE are enabled, and
>> > >>>>>> the architecture is arm64 or powerpc64.  Build drivers/of/kexec.c
>> > >>>>>> if CONFIG_OF_KEXEC is enabled.
>> > >>>>>>
>> > >>>>>> Signed-off-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
>> > >>>>>> Fixes: 33488dc4d61f ("of: Add a common kexec FDT setup function")
>> > >>>>>> Reported-by: kernel test robot <lkp@intel.com>
>> > >>>>>> ---
>> > >>>>>>     drivers/of/Kconfig  | 6 ++++++
>> > >>>>>>     drivers/of/Makefile | 7 +------
>> > >>>>>>     2 files changed, 7 insertions(+), 6 deletions(-)
>> > >>>>>>
>> > >>>>>> diff --git a/drivers/of/Kconfig b/drivers/of/Kconfig
>> > >>>>>> index 18450437d5d5..f2e8fa54862a 100644
>> > >>>>>> --- a/drivers/of/Kconfig
>> > >>>>>> +++ b/drivers/of/Kconfig
>> > >>>>>> @@ -100,4 +100,10 @@ config OF_DMA_DEFAULT_COHERENT
>> > >>>>>>             # arches should select this if DMA is coherent by default for OF devices
>> > >>>>>>             bool
>> > >>>>>>     +config OF_KEXEC
>> > >>>>>> +  bool
>> > >>>>>> +  depends on KEXEC_FILE
>> > >>>>>> +  depends on OF_FLATTREE
>> > >>>>>> +  default y if ARM64 || PPC64
>> > >>>>>> +
>> > >>>>>>     endif # OF
>> > >>>>>> diff --git a/drivers/of/Makefile b/drivers/of/Makefile
>> > >>>>>> index c13b982084a3..287579dd1695 100644
>> > >>>>>> --- a/drivers/of/Makefile
>> > >>>>>> +++ b/drivers/of/Makefile
>> > >>>>>> @@ -13,11 +13,6 @@ obj-$(CONFIG_OF_RESERVED_MEM) += of_reserved_mem.o
>> > >>>>>>     obj-$(CONFIG_OF_RESOLVE)  += resolver.o
>> > >>>>>>     obj-$(CONFIG_OF_OVERLAY) += overlay.o
>> > >>>>>>     obj-$(CONFIG_OF_NUMA) += of_numa.o
>> > >>>>>> -
>> > >>>>>> -ifdef CONFIG_KEXEC_FILE
>> > >>>>>> -ifdef CONFIG_OF_FLATTREE
>> > >>>>>> -obj-y     += kexec.o
>> > >>>>>> -endif
>> > >>>>>> -endif
>> > >>>>>> +obj-$(CONFIG_OF_KEXEC) += kexec.o
>> > >>>>>>       obj-$(CONFIG_OF_UNITTEST) += unittest-data/
>> > >>>>> Is it possible to reuse CONFIG_HAVE_IMA_KEXEC here?
>> > >>>>>
>> > >>>>
>> > >>>> For ppc64 CONFIG_HAVE_IMA_KEXEC is selected when CONFIG_KEXEC_FILE is enabled.
>> > >>>> So I don't see a problem in reusing CONFIG_HAVE_IMA_KEXEC for ppc.
>> > >>>>
>> > >>>> But for arm64, CONFIG_HAVE_IMA_KEXEC is enabled in the final patch in the patch
>> > >>>> set (the one for carrying forward IMA log across kexec for arm64). arm64 calls
>> > >>>> of_kexec_alloc_and_setup_fdt() prior to enabling CONFIG_HAVE_IMA_KEXEC and hence
>> > >>>> breaks the build for arm64.
>> > >>>
>> > >>> One problem is that I believe that this patch won't placate the robot,
>> > >>> because IIUC it generates config files at random and this change still
>> > >>> allows hppa and s390 to enable CONFIG_OF_KEXEC.
>> > >>
>> > >> I enabled CONFIG_OF_KEXEC for s390. With my patch applied,
>> > >> CONFIG_OF_KEXEC is removed. So I think the robot enabling this config
>> > >> would not be a problem.
>> > >>
>> > >>>
>> > >>> Perhaps a new CONFIG_HAVE_KIMAGE_ARCH option? Not having that option
>> > >>> would still allow building kexec.o, but would be used inside kexec.c to
>> > >>> avoid accessing kimage.arch members.
>> > >>>
>> > >>
>> > >> I think this is a good idea - a new CONFIG_HAVE_KIMAGE_ARCH, which will
>> > >> be selected by arm64 and ppc for now. I tried this, and it fixes the
>> > >> build issue.
>> > >>
>> > >> Although, the name for the new config can be misleading since PARISC,
>> > >> for instance, also defines "struct kimage_arch". Perhaps,
>> > >> CONFIG_HAVE_ELF_KIMAGE_ARCH since of_kexec_alloc_and_setup_fdt() is
>> > >> accessing ELF specific fields in "struct kimage_arch"?
>> > >>
>> > >> Rob/Mimi - please let us know which approach you think is better.
>> > >
>> > > I'd just move the fields to kimage.
>> > >
>> >
>> > I think Mimi's suggestion to use CONFIG_HAVE_IMA_KEXEC for building
>> > drivers/of/kexec.c would work and also avoid the bisect issue if we do
>> > the following:
>> 
>> That seems wrong given only a portion of the file depends on IMA. And
>> it reduces our compile coverage.
>  
> I agree with you this is the wrong solution.  Lakshmi's patch
> introduced a new option to prevent other arch's from including kexec.o,
> which is the same functionality as CONFIG_HAVE_IMA_KEXEC.  I'm just not
> sure what the right solution would be.

I think Rob's suggestion of just moving the elf_load_addr,
elf_headers_sz fields (and for consistency, elf_headers as well even though it
isn't used in tihs file) from kimage_arch to kimage.

The downside is that these fields will go unused on a number of
architectures, but it's not worth complicating the code just because of
it.

The patch to do that would have to go before "of: Add a common kexec FDT
setup function". That should be enough to preserve bisectability for all arches.

-- 
Thiago Jung Bauermann
IBM Linux Technology Center