linux-kernel - Re: [PATCH v12 2/4] powerpc: Move arch independent ima kexec functions to drivers/of/kexec.c

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Date:   Thu, 17 Dec 2020 22:25:33 -0800
From:   Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>
To:     Rob Herring <robh@...nel.org>
Cc:     Mimi Zohar <zohar@...ux.ibm.com>,
        Thiago Jung Bauermann <bauerman@...ux.ibm.com>,
        "AKASHI, Takahiro" <takahiro.akashi@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Will Deacon <will@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Michael Ellerman <mpe@...erman.id.au>,
        James Morse <james.morse@....com>,
        Sasha Levin <sashal@...nel.org>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Frank Rowand <frowand.list@...il.com>,
        vincenzo.frascino@....com, Mark Rutland <mark.rutland@....com>,
        dmitry.kasatkin@...il.com, James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Pavel Tatashin <pasha.tatashin@...een.com>,
        Allison Randal <allison@...utok.net>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Bhupesh Sharma <bhsharma@...hat.com>,
        Matthias Brugger <mbrugger@...e.com>,
        Hsin-Yi Wang <hsinyi@...omium.org>, tao.li@...o.com,
        Christophe Leroy <christophe.leroy@....fr>,
        Prakhar Srivastava <prsriva@...ux.microsoft.com>,
        balajib@...ux.microsoft.com, linux-integrity@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        devicetree@...r.kernel.org
Subject: Re: [PATCH v12 2/4] powerpc: Move arch independent ima kexec
 functions to drivers/of/kexec.c

On 12/17/20 2:01 PM, Rob Herring wrote:

> 
> [...]
> 
>>>> +#ifdef CONFIG_IMA_KEXEC
>>>> +/**
>>>> + * 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)
>>>
>>> This should be a static inline in asm/kexec.h.
>>
>> arch_ima_add_kexec_buffer() is identical for powerpc and arm64.
>> Would it be better to "static inline" this function in "of.h" instead of
>> duplicating it in "asm/kexec.h" for powerpc and arm64?
> 
> No, think about what it is specific to and place it there. It has
> nothing to do with DT really. All it is is a wrapper to access the
> struct members in kimage_arch. So it belongs where they are declared.
> Now perhaps ima_buffer_addr and ima_buffer_size shouldn't be arch
> specific, but that's a separate issue.
> 

Since "struct kimage" definition is not available in "asm/kexec.h", 
defining arch_ima_add_kexec_buffer() in this header file results in the 
following build error:

./arch/powerpc/include/asm/kexec.h: In function 'arch_ima_add_kexec_buffer':
./arch/powerpc/include/asm/kexec.h:139:7: error: 'struct kimage' has no 
member named 'arch'
   139 |  image->arch.ima_buffer_addr = load_addr;

I think it would be appropriate to make arch_ima_add_kexec_buffer() a 
static inline function in "security/integrity/ima/ima_kexec.c" - the 
only file where this function is used.

This will also enable sharing this function for powerpc and arm64 
architectures.

thanks,
  -lakshmi