linux-kernel - Re: [PATCH v15 10/10] arm64: Add IMA log information in kimage used for kexec

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Message-ID: <20210127180230.GA593@willie-the-truck>
Date:   Wed, 27 Jan 2021 18:02:30 +0000
From:   Will Deacon <will@...nel.org>
To:     Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>
Cc:     zohar@...ux.ibm.com, bauerman@...ux.ibm.com, robh@...nel.org,
        takahiro.akashi@...aro.org, gregkh@...uxfoundation.org,
        catalin.marinas@....com, mpe@...erman.id.au, james.morse@....com,
        sashal@...nel.org, benh@...nel.crashing.org, paulus@...ba.org,
        frowand.list@...il.com, vincenzo.frascino@....com,
        mark.rutland@....com, dmitry.kasatkin@...il.com, jmorris@...ei.org,
        serge@...lyn.com, pasha.tatashin@...een.com, allison@...utok.net,
        masahiroy@...nel.org, bhsharma@...hat.com, mbrugger@...e.com,
        hsinyi@...omium.org, tao.li@...o.com, christophe.leroy@....fr,
        prsriva@...ux.microsoft.com, balajib@...ux.microsoft.com,
        linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH v15 10/10] arm64: Add IMA log information in kimage used
 for kexec

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@...ux.microsoft.com>
> > > Signed-off-by: Prakhar Srivastava <prsriva@...ux.microsoft.com>
> > > Signed-off-by: Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>
> > > Reviewed-by: Thiago Jung Bauermann <bauerman@...ux.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?

Will