linux-kernel - Re: [PATCH v4 1/5] powerpc: Refactor kexec functions to move arch independent code to IMA

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Date:   Thu, 27 Aug 2020 20:35:41 -0300
From:   Thiago Jung Bauermann <bauerman@...ux.ibm.com>
To:     Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>
Cc:     zohar@...ux.ibm.com, robh@...nel.org, gregkh@...uxfoundation.org,
        james.morse@....com, catalin.marinas@....com, sashal@...nel.org,
        will@...nel.org, mpe@...erman.id.au, benh@...nel.crashing.org,
        paulus@...ba.org, robh+dt@...nel.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,
        kstewart@...uxfoundation.org, takahiro.akashi@...aro.org,
        tglx@...utronix.de, masahiroy@...nel.org, bhsharma@...hat.com,
        mbrugger@...e.com, hsinyi@...omium.org, tao.li@...o.com,
        christophe.leroy@....fr, linux-integrity@...r.kernel.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        prsriva@...ux.microsoft.com, balajib@...ux.microsoft.com
Subject: Re: [PATCH v4 1/5] powerpc: Refactor kexec functions to move arch
 independent code to IMA


Lakshmi Ramasubramanian <nramas@...ux.microsoft.com> writes:

> The functions ima_get_kexec_buffer() and ima_free_kexec_buffer() that
> handle carrying forward the IMA measurement logs on kexec for powerpc
> do not have architecture specific code, but they are currently defined
> for powerpc only.
>
> Move these functions to IMA subsystem so that it can be used for other
> architectures as well. A later patch in this series will use these
> functions for carrying forward the IMA measurement log for ARM64.
>
> Define FDT_PROP_IMA_KEXEC_BUFFER for the chosen node, namely
> "linux,ima-kexec-buffer", that is added to the DTB to hold
> the address and the size of the memory reserved to carry
> the IMA measurement log.
>
> 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>

This patch removes two functions from arch/powerpc/kexec/ima.c, but adds
four to security/integrity/ima/ima_kexec.c. The extra ones are
get_addr_size_cells() and do_get_kexec_buffer(), which are being copied
from the powerpc code but can't be removed yet because they're still
used there by remove_ima_buffer() and setup_ima_buffer().

On the next patch you remove the need for these functions in powerpc
code and therefore delete them. This confused me at first, so I think it
would be cleared if you put patch 2 first in the series and then on this
patch you can simply move the four functions and delete them from
arch/powerpc/kexec/ima.c.

If you prefer to keep the current order, it's worth mentioning on the
commit log where get_addr_size_cells() and do_get_kexec_buffer() are
coming from.

Regardless:

Reviewed-by: Thiago Jung Bauermann <bauerman@...ux.ibm.com>

-- 
Thiago Jung Bauermann
IBM Linux Technology Center