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Subject: Re: [PATCH v15 10/10] arm64: Add IMA log information in kimage used
 for kexec
From:   Mimi Zohar <zohar@linux.ibm.com>
To:     Lakshmi Ramasubramanian <nramas@linux.microsoft.com>,
        Will Deacon <will@kernel.org>
Cc:     bauerman@linux.ibm.com, robh@kernel.org,
        takahiro.akashi@linaro.org, gregkh@linuxfoundation.org,
        catalin.marinas@arm.com, mpe@ellerman.id.au, james.morse@arm.com,
        sashal@kernel.org, benh@kernel.crashing.org, paulus@samba.org,
        frowand.list@gmail.com, vincenzo.frascino@arm.com,
        mark.rutland@arm.com, dmitry.kasatkin@gmail.com, jmorris@namei.org,
        serge@hallyn.com, pasha.tatashin@soleen.com, allison@lohutok.net,
        masahiroy@kernel.org, bhsharma@redhat.com, mbrugger@suse.com,
        hsinyi@chromium.org, tao.li@vivo.com, christophe.leroy@c-s.fr,
        prsriva@linux.microsoft.com, balajib@linux.microsoft.com,
        linux-integrity@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, devicetree@vger.kernel.org,
        linuxppc-dev@lists.ozlabs.org
Date:   Wed, 27 Jan 2021 13:31:02 -0500
In-Reply-To: <8a573f84-732a-3591-8751-f7b08edaa01d@linux.microsoft.com>
References: <20210115173017.30617-1-nramas@linux.microsoft.com>
         <20210115173017.30617-11-nramas@linux.microsoft.com>
         <20210127165424.GB358@willie-the-truck>
         <dec23eb8-0b27-3227-d1ef-f759338a7f9f@linux.microsoft.com>
         <20210127180230.GA593@willie-the-truck>
         <8a573f84-732a-3591-8751-f7b08edaa01d@linux.microsoft.com>
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On Wed, 2021-01-27 at 10:24 -0800, Lakshmi Ramasubramanian wrote:
> On 1/27/21 10:02 AM, Will Deacon wrote:
> > On Wed, Jan 27, 2021 at 09:56:53AM -0800, Lakshmi Ramasubramanian wrote:
> >> On 1/27/21 8:54 AM, Will Deacon wrote:
> >>> On Fri, Jan 15, 2021 at 09:30:17AM -0800, Lakshmi Ramasubramanian wrote:
> >>>> Address and size of the buffer containing the IMA measurement log need
> >>>> to be passed from the current kernel to the next kernel on kexec.
> >>>>
> >>>> Add address and size fields to "struct kimage_arch" for ARM64 platform
> >>>> to hold the address and size of the IMA measurement log buffer.
> >>>>
> >>>> Update CONFIG_KEXEC_FILE to select CONFIG_HAVE_IMA_KEXEC, if CONFIG_IMA
> >>>> is enabled, to indicate that the IMA measurement log information is
> >>>> present in the device tree for ARM64.
> >>>>
> >>>> Co-developed-by: Prakhar Srivastava <prsriva@linux.microsoft.com>
> >>>> Signed-off-by: Prakhar Srivastava <prsriva@linux.microsoft.com>
> >>>> Signed-off-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
> >>>> Reviewed-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
> >>>> ---
> >>>>    arch/arm64/Kconfig             | 1 +
> >>>>    arch/arm64/include/asm/kexec.h | 5 +++++
> >>>>    2 files changed, 6 insertions(+)
> >>>>
> >>>> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> >>>> index 1d466addb078..ea7f7fe3dccd 100644
> >>>> --- a/arch/arm64/Kconfig
> >>>> +++ b/arch/arm64/Kconfig
> >>>> @@ -1094,6 +1094,7 @@ config KEXEC
> >>>>    config KEXEC_FILE
> >>>>    	bool "kexec file based system call"
> >>>>    	select KEXEC_CORE
> >>>> +	select HAVE_IMA_KEXEC if IMA
> >>>>    	help
> >>>>    	  This is new version of kexec system call. This system call is
> >>>>    	  file based and takes file descriptors as system call argument
> >>>> diff --git a/arch/arm64/include/asm/kexec.h b/arch/arm64/include/asm/kexec.h
> >>>> index d24b527e8c00..2bd19ccb6c43 100644
> >>>> --- a/arch/arm64/include/asm/kexec.h
> >>>> +++ b/arch/arm64/include/asm/kexec.h
> >>>> @@ -100,6 +100,11 @@ struct kimage_arch {
> >>>>    	void *elf_headers;
> >>>>    	unsigned long elf_headers_mem;
> >>>>    	unsigned long elf_headers_sz;
> >>>> +
> >>>> +#ifdef CONFIG_IMA_KEXEC
> >>>> +	phys_addr_t ima_buffer_addr;
> >>>> +	size_t ima_buffer_size;
> >>>> +#endif
> >>>
> >>> Why do these need to be in the arch structure instead of 'struct kimage'?
> >>>
> >>
> >> Currently, only powerpc and, with this patch set, arm64 have support for
> >> carrying forward IMA measurement list across kexec system call. The above
> >> fields are used for tracking IMA measurement list.
> >>
> >> Do you see a reason to move these fields to "struct kimage"?
> > 
> > If they're gated on CONFIG_IMA_KEXEC, then it seems harmless for them to
> > be added to the shared structure. Or are you saying that there are
> > architectures which have CONFIG_IMA_KEXEC but do not want these fields?
> > 
> 
> As far as I know, there are no other architectures that define 
> CONFIG_IMA_KEXEC, but do not use these fields.

Yes, CONFIG_IMA_KEXEC enables "carrying the IMA measurement list across
a soft boot".   The only arch that currently carries the IMA
measurement across kexec is powerpc.

Mimi