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Subject: Re: [PATCH v15 10/10] arm64: Add IMA log information in kimage used
 for kexec
To:     Will Deacon <will@kernel.org>, Mimi Zohar <zohar@linux.ibm.com>
Cc:     bauerman@linux.ibm.com, robh@kernel.org,
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References: <20210115173017.30617-1-nramas@linux.microsoft.com>
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 <20210127165424.GB358@willie-the-truck>
 <dec23eb8-0b27-3227-d1ef-f759338a7f9f@linux.microsoft.com>
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 <8a573f84-732a-3591-8751-f7b08edaa01d@linux.microsoft.com>
 <6343ab2eec390ab7582beea04f8006af095850c8.camel@linux.ibm.com>
 <20210127231334.GB1016@willie-the-truck>
From:   Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
Message-ID: <681a4410-8a96-bce1-fcd4-d45d56625b39@linux.microsoft.com>
Date:   Wed, 27 Jan 2021 20:05:21 -0800
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On 1/27/21 3:13 PM, Will Deacon wrote:
> On Wed, Jan 27, 2021 at 01:31:02PM -0500, Mimi Zohar wrote:
>> On Wed, 2021-01-27 at 10:24 -0800, Lakshmi Ramasubramanian wrote:
>>> On 1/27/21 10:02 AM, Will Deacon wrote:
>>>> On Wed, Jan 27, 2021 at 09:56:53AM -0800, Lakshmi Ramasubramanian wrote:
>>>>> On 1/27/21 8:54 AM, Will Deacon wrote:
>>>>>> On Fri, Jan 15, 2021 at 09:30:17AM -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.
>>>>>>>
>>>>>>> Update CONFIG_KEXEC_FILE to select CONFIG_HAVE_IMA_KEXEC, if CONFIG_IMA
>>>>>>> is enabled, to indicate that the IMA measurement log information is
>>>>>>> present in the device tree for ARM64.
>>>>>>>
>>>>>>> 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>
>>>>>>> Reviewed-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
>>>>>>> ---
>>>>>>>     arch/arm64/Kconfig             | 1 +
>>>>>>>     arch/arm64/include/asm/kexec.h | 5 +++++
>>>>>>>     2 files changed, 6 insertions(+)
>>>>>>>
>>>>>>> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
>>>>>>> index 1d466addb078..ea7f7fe3dccd 100644
>>>>>>> --- a/arch/arm64/Kconfig
>>>>>>> +++ b/arch/arm64/Kconfig
>>>>>>> @@ -1094,6 +1094,7 @@ config KEXEC
>>>>>>>     config KEXEC_FILE
>>>>>>>     	bool "kexec file based system call"
>>>>>>>     	select KEXEC_CORE
>>>>>>> +	select HAVE_IMA_KEXEC if IMA
>>>>>>>     	help
>>>>>>>     	  This is new version of kexec system call. This system call is
>>>>>>>     	  file based and takes file descriptors as system call argument
>>>>>>> diff --git a/arch/arm64/include/asm/kexec.h b/arch/arm64/include/asm/kexec.h
>>>>>>> index d24b527e8c00..2bd19ccb6c43 100644
>>>>>>> --- a/arch/arm64/include/asm/kexec.h
>>>>>>> +++ b/arch/arm64/include/asm/kexec.h
>>>>>>> @@ -100,6 +100,11 @@ struct kimage_arch {
>>>>>>>     	void *elf_headers;
>>>>>>>     	unsigned long elf_headers_mem;
>>>>>>>     	unsigned long elf_headers_sz;
>>>>>>> +
>>>>>>> +#ifdef CONFIG_IMA_KEXEC
>>>>>>> +	phys_addr_t ima_buffer_addr;
>>>>>>> +	size_t ima_buffer_size;
>>>>>>> +#endif
>>>>>>
>>>>>> Why do these need to be in the arch structure instead of 'struct kimage'?
>>>>>>
>>>>>
>>>>> Currently, only powerpc and, with this patch set, arm64 have support for
>>>>> carrying forward IMA measurement list across kexec system call. The above
>>>>> fields are used for tracking IMA measurement list.
>>>>>
>>>>> Do you see a reason to move these fields to "struct kimage"?
>>>>
>>>> If they're gated on CONFIG_IMA_KEXEC, then it seems harmless for them to
>>>> be added to the shared structure. Or are you saying that there are
>>>> architectures which have CONFIG_IMA_KEXEC but do not want these fields?
>>>>
>>>
>>> As far as I know, there are no other architectures that define
>>> CONFIG_IMA_KEXEC, but do not use these fields.
>>
>> Yes, CONFIG_IMA_KEXEC enables "carrying the IMA measurement list across
>> a soft boot".   The only arch that currently carries the IMA
>> measurement across kexec is powerpc.
> 
> Ok, in which case this sounds like it should be in the shared structure, no?
> 

Ok - I'll move the IMA kexec buffer fields from "struct kimage_arch" to 
"struct kimage" for both powerpc and arm64.

thanks,
  -lakshmi