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Date:   Sat, 05 Dec 2020 18:36:46 -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 v10 7/8] powerpc: Move arch_ima_add_kexec_buffer to ima


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

> arch_ima_add_kexec_buffer() sets the address and size of the IMA
> measurement log in the architecture specific field in struct kimage.
> This function does not have architecture specific code, but is
> currently limited to powerpc.
>
> Move arch_ima_add_kexec_buffer() to
> security/integrity/ima/ima_kexec.c so that it is accessible for
> other architectures as well.
>
> Signed-off-by: Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>

Not sure if the maintainers will agree with me (see below), but FWIW:

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

> ---
>  arch/powerpc/include/asm/ima.h     |  3 ---
>  arch/powerpc/kexec/ima.c           | 21 ---------------------
>  security/integrity/ima/ima_kexec.c | 22 ++++++++++++++++++++++
>  3 files changed, 22 insertions(+), 24 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/ima.h b/arch/powerpc/include/asm/ima.h
> index d8444d27f0d8..d6ab5d944dcd 100644
> --- a/arch/powerpc/include/asm/ima.h
> +++ b/arch/powerpc/include/asm/ima.h
> @@ -7,9 +7,6 @@
>  struct kimage;
>  
>  #ifdef CONFIG_IMA_KEXEC
> -int arch_ima_add_kexec_buffer(struct kimage *image, unsigned long load_addr,
> -			      size_t size);
> -
>  int setup_ima_buffer(const struct kimage *image, void *fdt, int chosen_node);
>  #else
>  static inline int setup_ima_buffer(const struct kimage *image, void *fdt,
> diff --git a/arch/powerpc/kexec/ima.c b/arch/powerpc/kexec/ima.c
> index bf7084c0c4da..b2793be353a9 100644
> --- a/arch/powerpc/kexec/ima.c
> +++ b/arch/powerpc/kexec/ima.c
> @@ -13,27 +13,6 @@
>  #include <linux/libfdt.h>
>  #include <asm/ima.h>
>  
> -/**
> - * arch_ima_add_kexec_buffer - do arch-specific steps to add the IMA buffer
> - *
> - * @image: kimage struct to set IMA buffer data
> - * @load_addr: Starting address where IMA buffer is loaded at
> - * @size: Number of bytes in 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;
> -}
> -
>  static int write_number(void *p, u64 value, int cells)
>  {
>  	if (cells == 1) {
> diff --git a/security/integrity/ima/ima_kexec.c b/security/integrity/ima/ima_kexec.c
> index 4d354593aecf..5263dafe8f4d 100644
> --- a/security/integrity/ima/ima_kexec.c
> +++ b/security/integrity/ima/ima_kexec.c
> @@ -74,6 +74,28 @@ static int ima_dump_measurement_list(unsigned long *buffer_size, void **buffer,
>  	return ret;
>  }
>  
> +/**
> + * arch_ima_add_kexec_buffer - do arch-specific steps to add the IMA buffer
> + *
> + * @image: kimage struct to set IMA buffer data
> + * @load_addr: Starting address where IMA buffer is loaded at
> + * @size: Number of bytes in 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.
> + */
> +static 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;
> +}
> +

Both powerpc and arm64 use the definition above for
arch_ima_add_kexec_buffer(), so it makes sense to share them as you do
in this patch. This file isn't the best one to put arch-specific code
which happens to be identical among architectures, but I can't think of
somewhere else to put it.

For now this isn't an issue since powerpc and arm64 are the only arches
implementing tihs feature. If a third arch implemented it and also used
the same function definition as above, it wouldn't be an issue either so
perhaps this is good enough for the time being? :-)

With this patch, the `#include <asm/ima.h>` in
security/integrity/ima/ima.h can be removed. It was there just to
provide a declaration of arch_ima_add_kexec_buffer().

-- 
Thiago Jung Bauermann
IBM Linux Technology Center

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