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

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Date:   Tue, 01 Dec 2020 06:39:04 -0500
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Lakshmi Ramasubramanian <nramas@...ux.microsoft.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 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?

> 
> 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?

Mimi