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Subject: Re: [PATCH v7 1/4] powerpc: Refactor kexec functions to move arch
 independent code to kernel
From:   Mimi Zohar <zohar@linux.ibm.com>
To:     Lakshmi Ramasubramanian <nramas@linux.microsoft.com>,
        bauerman@linux.ibm.com, robh@kernel.org,
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Cc:     linux-integrity@vger.kernel.org, linux-kernel@vger.kernel.org,
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Date:   Tue, 20 Oct 2020 16:00:34 -0400
In-Reply-To: <20200930205941.1576-2-nramas@linux.microsoft.com>
References: <20200930205941.1576-1-nramas@linux.microsoft.com>
         <20200930205941.1576-2-nramas@linux.microsoft.com>
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Hi Lakshmi,

On Wed, 2020-09-30 at 13:59 -0700, Lakshmi Ramasubramanian wrote:
> The functions remove_ima_buffer() and delete_fdt_mem_rsv() 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.
> 
> remove_ima_buffer() and delete_fdt_mem_rsv() are used to remove
> the IMA log entry from the device tree and free the memory reserved
> for the log. These functions need to be defined even if the current
> kernel does not support carrying forward IMA log across kexec since
> the previous kernel could have supported that and therefore the current
> kernel needs to free the allocation.
> 
> Rename remove_ima_buffer() to remove_ima_kexec_buffer().
> Define remove_ima_kexec_buffer() and delete_fdt_mem_rsv() in kernel.
> A later patch in this series will use these functions to free
> the allocation, if any, made by the previous kernel 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@linux.microsoft.com>
> Signed-off-by: Prakhar Srivastava <prsriva@linux.microsoft.com>
> Signed-off-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
> Reported-by: kernel test robot <lkp@intel.com> error: implicit declaration of function 'delete_fdt_mem_rsv' [-Werror,-Wimplicit-function-declaration]

Much better!  This version limits unnecessarily changing the existing
code to adding a couple of debugging statements, but that looks to be
about it.

Based on Chester Lin's "ima_arch" support for arm64 discussion, the IMA generic
EFI support will be defined in ima/ima-efi.c.  Similarly, I think it would make sense to put the generic device tree support in ima/ima_kexec_fdt.c or ima/ima_fdt.c, as opposed to kernel/.  (Refer to my comments on 2/4 about the new file named ima_kexec_fdt.c.)

thanks,

Mimi