linux-kernel - Re: [PATCH v7 2/4] powerpc: Refactor kexec functions to move arch independent code to ima

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Message-ID: <9a44d8aa-515d-fc97-74bd-7ae976dea35b@linux.microsoft.com>
Date:   Tue, 20 Oct 2020 19:38:39 -0700
From:   Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>
To:     Mimi Zohar <zohar@...ux.ibm.com>, bauerman@...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
Cc:     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 v7 2/4] powerpc: Refactor kexec functions to move arch
 independent code to ima

On 10/20/20 1:01 PM, Mimi Zohar wrote:
> On Wed, 2020-09-30 at 13:59 -0700, Lakshmi Ramasubramanian wrote:
>> 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 ima_get_kexec_buffer() and ima_free_kexec_buffer() to IMA
>> subsystem. A later patch in this series will use these functions for
>> carrying forward the IMA measurement log for ARM64.
>>
>> With the above refactoring arch/powerpc/kexec/ima.c contains only
>> functions used when CONFIG_IMA_KEXEC is enabled. Update Makefile
>> in arch/powerpc/kexec to include arch/powerpc/kexec/ima.c only
>> when CONFIG_IMA_KEXEC is enabled.
>>
>> Move ima_dump_measurement_list() and ima_add_kexec_buffer() to
>> a new file namely ima_kexec_fdt.c in IMA. Update
>> security/integrity/ima/Makefile to include ima_kexec_fdt.c only
>> when CONFIG_IMA_KEXEC is enabled.
>>
>> 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>
> 
> The existing support for carrying the IMA measurement list across kexec
> is limited to powerpc.  This patch set is adding similar support for
> arm64, making as much of the existing code as generic as possible.
> However ima_dump_measurement_list() is already generic, but for some
> reason this patch moves it to ima_kexec_fdt.c.  ima_kexec_fdt.c should
> be limited to device tree specific code.

I wanted to split the functions defined under CONFIG_HAVE_IMA_KEXEC and 
CONFIG_IMA_KEXEC to separate files so that we can get rid of #ifdef in C 
file and instead conditionally compile the C files (using Makefile).

ima_dump_measurement_list() need to be defined only when 
CONFIG_IMA_KEXEC is defined. I moved it to ima_kexec_fdt.c

Instead of ima_kexec_fdt.c, where ima_dump_measurement_list() and 
ima_add_kexec_buffer() are defined, perhaps I can change the file name 
to "ima_kexec_buffer.c". Would that be better?

> 
> This patch is probably doing the right thing, but the way the patch is
> formatted it replaces parts of a function with a different function.
> With the changes suggested above and in 1/4,  the next version should
> be clearer.

Like I'd stated above, I wanted to remove "#ifdef" from the C files and 
hence had to move some functions. But the functionalities haven't been 
changed.

thanks,
  -lakshmi