linux-kernel - Re: [PATCH v9 7/8] arm64: Store IMA log information in kimage used for kexec

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Message-ID: <9e0430bc-e86b-c1c8-3b55-39292a05d6bb@linux.microsoft.com>
Date:   Tue, 1 Dec 2020 11:08:01 -0800
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 v9 7/8] arm64: Store IMA log information in kimage used
 for kexec

On 12/1/20 3:39 AM, Mimi Zohar wrote:
> On Fri, 2020-11-13 at 11:22 -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.
>> Define an architecture specific function for ARM64 namely
>> arch_ima_add_kexec_buffer() that will set the address and size of
>> the current kernel's IMA buffer to be passed to the next kernel on kexec.
>>
>> 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/include/asm/ima.h   | 18 ++++++++++++++++++
>>   arch/arm64/include/asm/kexec.h |  3 +++
>>   arch/arm64/kernel/Makefile     |  1 +
>>   arch/arm64/kernel/ima_kexec.c  | 34 ++++++++++++++++++++++++++++++++++
>>   4 files changed, 56 insertions(+)
>>   create mode 100644 arch/arm64/include/asm/ima.h
>>   create mode 100644 arch/arm64/kernel/ima_kexec.c
>>
>> diff --git a/arch/arm64/include/asm/ima.h b/arch/arm64/include/asm/ima.h
>> new file mode 100644
>> index 000000000000..507fc94ddaba
>> --- /dev/null
>> +++ b/arch/arm64/include/asm/ima.h
>> @@ -0,0 +1,18 @@
>> +/* SPDX-License-Identifier: GPL-2.0-or-later */
>> +/*
>> + * Copyright (C) 2019 Microsoft Corporation
>> + *
>> + * Author: Prakhar Srivastava <prsriva@...ux.microsoft.com>
>> + *
>> + */
>> +#ifndef _ASM_ARCH_IMA_H
>> +#define _ASM_ARCH_IMA_H
>> +
>> +struct kimage;
>> +
>> +#ifdef CONFIG_IMA_KEXEC
>> +int arch_ima_add_kexec_buffer(struct kimage *image, unsigned long load_addr,
>> +			      size_t size);
>> +#endif /* CONFIG_IMA_KEXEC */
>> +
>> +#endif /* _ASM_ARCH_IMA_H */
>> diff --git a/arch/arm64/include/asm/kexec.h b/arch/arm64/include/asm/kexec.h
>> index d24b527e8c00..7bd60c185ad3 100644
>> --- a/arch/arm64/include/asm/kexec.h
>> +++ b/arch/arm64/include/asm/kexec.h
>> @@ -100,6 +100,9 @@ struct kimage_arch {
>>   	void *elf_headers;
>>   	unsigned long elf_headers_mem;
>>   	unsigned long elf_headers_sz;
>> +
>> +	phys_addr_t ima_buffer_addr;
>> +	size_t ima_buffer_size;
>>   };
> 
> Any reason these definitions are not conditionally defined based on
> CONFIG_IMA_KEXEC, like on powerpc?

I'll define ima buffer related fields conditionally (CONFIG_IMA_KEXEC).

> 
>>
>> diff --git a/arch/arm64/kernel/ima_kexec.c b/arch/arm64/kernel/ima_kexec.c
>> new file mode 100644
>> index 000000000000..1847f1230710
>> --- /dev/null
>> +++ b/arch/arm64/kernel/ima_kexec.c
>> @@ -0,0 +1,34 @@
>> +// SPDX-License-Identifier: GPL-2.0-or-later
>> +/*
>> + * Copyright (C) 2019 Microsoft Corporation
>> + *
>> + * Author: Prakhar Srivastava <prsriva@...ux.microsoft.com>
>> + *
>> + * File: ima_kexec.c
>> + *       Defines IMA kexec functions.
>> + */
>> +
>> +#include <linux/kernel.h>
>> +#include <linux/kexec.h>
>> +#include <linux/types.h>
>> +#include <asm/ima.h>
>> +
>> +/**
>> + * arch_ima_add_kexec_buffer - do arch-specific steps to add the IMA buffer
>> + *
>> + * @image: kimage structure to set ima buffer information in for kexec
>> + * @load_addr: Start address of the IMA buffer
>> + * @size: size of the IMA buffer
>> + *
>> + * Architectures should use this function to pass on the IMA buffer
>> + * information to the next kernel.
>> + *
>> + * Return: 0 on success, negative errno on error.
>> + */
>> +int arch_ima_add_kexec_buffer(struct kimage *image, unsigned long load_addr,
>> +			      size_t size)
>> +{
>> +	image->arch.ima_buffer_addr = load_addr;
>> +	image->arch.ima_buffer_size = size;
>> +	return 0;
>> +}
> 
> This is exactly the same as the powerpc version.  Couldn't there be a
> common version of this as well?

I think it can be moved to a common version. I'll make that change.

thanks,
  -lakshmi