linux-kernel - Re: [PATCH v2 02/13] x86/kexec: refactor for kernel/Kconfig.kexec

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Message-ID: <ac065d02-61a4-3b1f-241d-443ede70d3f2@oracle.com>
Date:   Tue, 20 Jun 2023 07:56:55 -0500
From:   Eric DeVolder <eric.devolder@...cle.com>
To:     Baoquan He <bhe@...hat.com>
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Subject: Re: [PATCH v2 02/13] x86/kexec: refactor for kernel/Kconfig.kexec



On 6/20/23 03:21, Baoquan He wrote:
> Hi Eric,
> 
> On 06/19/23 at 10:57am, Eric DeVolder wrote:
> ......
>> +config ARCH_SUPPORTS_KEXEC
>> +	def_bool y
>>   
>> -config ARCH_HAS_KEXEC_PURGATORY
>> -	def_bool KEXEC_FILE
>> +config ARCH_SUPPORTS_KEXEC_FILE
>> +	def_bool X86_64 && CRYPTO && CRYPTO_SHA256
> ......
>> +config ARCH_SELECTS_KEXEC_FILE
>> +	def_bool y
>>   	depends on KEXEC_FILE
>> -	help
> 
> I am a little confused about this ARCH_SELECTS_XX adding. Wondering what
> limits us defining the ARCH_SUPPORTS_KEXEC_FILE like below? I have limited
> knowledge about Kconfig, please correct me if I am wrong. Thanks in
> advance.
> 
>   +config ARCH_SUPPORTS_KEXEC_FILE
>   +	def_bool y
>    	depends on KEXEC_FILE
>    	depends on X86_64 && CRYPTO && CRYPTO_SHA256
> 

For the ARCH_SUPPORTS_ options, I chose to list the dependencies on the def_bool line to show that 
it took all those conditions to result in True.
However, as you point out, using a def_bool y and then listing them as 'depends on' works as well.
Probably would have resulted in fewer changes to the Kconfig file.
Either way is ok (the 'depends on KEXEC_FILE' is erroneous in your example).
eric


>> -
>> -	  This option makes the kexec_file_load() syscall check for a valid
>> -	  signature of the kernel image.  The image can still be loaded without
>> -	  a valid signature unless you also enable KEXEC_SIG_FORCE, though if
>> -	  there's a signature that we can check, then it must be valid.
>> -
>> -	  In addition to this option, you need to enable signature
>> -	  verification for the corresponding kernel image type being
>> -	  loaded in order for this to work.
>> -
>