linux-kernel - Re: [RFC PATCH v1 1/1] Add support for arm64 to carry ima measurement log in kexec_file

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Date:   Tue, 24 Sep 2019 17:25:30 -0300
From:   Thiago Jung Bauermann <bauerman@...ux.ibm.com>
To:     prsriva <prsriva@...ux.microsoft.com>
Cc:     mark.rutland@....com, jean-philippe@...aro.org, arnd@...db.de,
        takahiro.akashi@...aro.org, sboyd@...nel.org,
        catalin.marinas@....com, kexec@...ts.infradead.org,
        linux-kernel@...r.kernel.org, zohar@...ux.ibm.com,
        yamada.masahiro@...ionext.com, kristina.martsenko@....org,
        duwe@....de, allison@...utok.net, james.morse@....org,
        linux-integrity@...r.kernel.org, tglx@...utronix.de,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [RFC PATCH v1 1/1] Add support for arm64 to carry ima measurement log in kexec_file_load


Hello,

prsriva <prsriva@...ux.microsoft.com> writes:

> On 9/19/19 8:07 PM, Thiago Jung Bauermann wrote:
>> Hello Prakhar,
>>
>> Prakhar Srivastava <prsriva@...ux.microsoft.com> writes:
>>
>>> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
>>> index 3adcec05b1f6..f39b12dbf9e8 100644
>>> --- a/arch/arm64/Kconfig
>>> +++ b/arch/arm64/Kconfig
>>> @@ -976,6 +976,13 @@ config KEXEC_VERIFY_SIG
>>>   	  verification for the corresponding kernel image type being
>>>   	  loaded in order for this to work.
>>>
>>> +config HAVE_IMA_KEXEC
>>> +	bool "Carry over IMA measurement log during kexec_file_load() syscall"
>>> +	depends on KEXEC_FILE
>>> +	help
>>> +	  Select this option to carry over IMA measurement log during
>>> +	  kexec_file_load.
>>> +
>>>   config KEXEC_IMAGE_VERIFY_SIG
>>>   	bool "Enable Image signature verification support"
>>>   	default y
>> This is not right. As it stands, HAVE_IMA_KEXEC is essentially a synonym
>> for IMA_KEXEC.
>>
>> It's not meant to be user-visible in the config process. Instead, it's
>> meant to be selected by the arch Kconfig (probably by the ARM64 config
>> symbol) to signal to IMA's Kconfig that it can offer the IMA_KEXEC
>> option.
>>
>> I also mentioned in my previous review that config HAVE_IMA_KEXEC should
>> be defined in arch/Kconfig, not separately in both arch/arm64/Kconfig
>> and arch/powerpc/Kconfig.
>
> I see the entry exists in arch/Kconfig and is overwritten.
> I will remove entries both from powerpc and arm64.
>
> How do i cross-compile for powerpc?

There are some instructions here:

https://github.com/linuxppc/wiki/wiki/Building-powerpc-kernels

>>> diff --git a/arch/arm64/include/asm/ima.h b/arch/arm64/include/asm/ima.h
>>> new file mode 100644
>>> index 000000000000..e23cee84729f
>>> --- /dev/null
>>> +++ b/arch/arm64/include/asm/ima.h
>>> @@ -0,0 +1,29 @@
>>> +/* SPDX-License-Identifier: GPL-2.0 */
>>> +#ifndef _ASM_ARM64_IMA_H
>>> +#define _ASM_ARM64_IMA_H
>>> +
>>> +struct kimage;
>>> +
>>> +int ima_get_kexec_buffer(void **addr, size_t *size);
>>> +int ima_free_kexec_buffer(void);
>>> +
>>> +#ifdef CONFIG_IMA
>>> +void remove_ima_buffer(void *fdt, int chosen_node);
>>> +#else
>>> +static inline void remove_ima_buffer(void *fdt, int chosen_node) {}
>>> +#endif
>> I mentioned in my previous review that remove_ima_buffer() should exist
>> even if CONFIG_IMA isn't set. Did you arrive at a different conclusion?
>
> I made the needed changed in makefile, missed removing the
>
> configs here. Thanks for pointing this out.

Thanks.

-- 
Thiago Jung Bauermann
IBM Linux Technology Center