linux-kernel - Re: [PATCH v3 12/13] s390/kexec: refactor for kernel/Kconfig.kexec

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Message-ID: <ZJ7ToGgYAq33bwYI@li-008a6a4c-3549-11b2-a85c-c5cc2836eea2.ibm.com>
Date:   Fri, 30 Jun 2023 15:07:44 +0200
From:   Alexander Gordeev <agordeev@...ux.ibm.com>
To:     Eric DeVolder <eric.devolder@...cle.com>
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Subject: Re: [PATCH v3 12/13] s390/kexec: refactor for kernel/Kconfig.kexec

On Mon, Jun 26, 2023 at 12:13:31PM -0400, Eric DeVolder wrote:
> The kexec and crash kernel options are provided in the common
> kernel/Kconfig.kexec. Utilize the common options and provide
> the ARCH_SUPPORTS_ and ARCH_SELECTS_ entries to recreate the
> equivalent set of KEXEC and CRASH options.
> 
> NOTE: The original Kconfig has a KEXEC_SIG which depends on
> MODULE_SIG_FORMAT. However, attempts to keep the MODULE_SIG_FORMAT
> dependency (using the strategy outlined in this series, and other
> techniques) results in 'error: recursive dependency detected'
> on CRYPTO.
> 
> Per Alexander Gordeev <agordeev@...ux.ibm.com>: "the MODULE_SIG_FORMAT
> dependency was introduced with [git commit below] and in fact was not
> necessary, since s390 did/does not use mod_check_sig() anyway.
> 
>  commit c8424e776b09 ("MODSIGN: Export module signature definitions")
> 
> MODULE_SIG_FORMAT is needed to select SYSTEM_DATA_VERIFICATION. But
> SYSTEM_DATA_VERIFICATION is also selected by FS_VERITY*, so dropping
> MODULE_SIG_FORMAT does not hurt."
> 
> Therefore, the solution is to drop the MODULE_SIG_FORMAT dependency
> from KEXEC_SIG. Still results in equivalent .config files for s390.
> 
> Signed-off-by: Eric DeVolder <eric.devolder@...cle.com>
> ---
>  arch/s390/Kconfig | 65 ++++++++++++++---------------------------------
>  1 file changed, 19 insertions(+), 46 deletions(-)
> 
> diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
> index 6dab9c1be508..58dc124433ca 100644
> --- a/arch/s390/Kconfig
> +++ b/arch/s390/Kconfig
> @@ -243,6 +243,25 @@ config PGTABLE_LEVELS
>  
>  source "kernel/livepatch/Kconfig"
>  
> +config ARCH_DEFAULT_KEXEC
> +	def_bool y
> +
> +config ARCH_SUPPORTS_KEXEC
> +	def_bool y
> +
> +config ARCH_SUPPORTS_KEXEC_FILE
> +	def_bool CRYPTO && CRYPTO_SHA256 && CRYPTO_SHA256_S390
> +
> +config ARCH_HAS_KEXEC_PURGATORY
> +	def_bool KEXEC_FILE
> +
> +config ARCH_SUPPORTS_CRASH_DUMP
> +	def_bool y
> +	help
> +	  Refer to <file:Documentation/s390/zfcpdump.rst> for more details on this.
> +	  This option also enables s390 zfcpdump.
> +	  See also <file:Documentation/s390/zfcpdump.rst>
> +
>  menu "Processor type and features"
>  
>  config HAVE_MARCH_Z10_FEATURES
> @@ -481,36 +500,6 @@ config SCHED_TOPOLOGY
>  
>  source "kernel/Kconfig.hz"
>  
> -config KEXEC
> -	def_bool y
> -	select KEXEC_CORE
> -
> -config KEXEC_FILE
> -	bool "kexec file based system call"
> -	select KEXEC_CORE
> -	depends on CRYPTO
> -	depends on CRYPTO_SHA256
> -	depends on CRYPTO_SHA256_S390
> -	help
> -	  Enable the kexec file based system call. In contrast to the normal
> -	  kexec system call this system call takes file descriptors for the
> -	  kernel and initramfs as arguments.
> -
> -config ARCH_HAS_KEXEC_PURGATORY
> -	def_bool y
> -	depends on KEXEC_FILE
> -
> -config KEXEC_SIG
> -	bool "Verify kernel signature during kexec_file_load() syscall"
> -	depends on KEXEC_FILE && MODULE_SIG_FORMAT
> -	help
> -	  This option makes kernel signature verification mandatory for
> -	  the kexec_file_load() syscall.
> -
> -	  In addition to that option, you need to enable signature
> -	  verification for the corresponding kernel image type being
> -	  loaded in order for this to work.
> -
>  config KERNEL_NOBP
>  	def_bool n
>  	prompt "Enable modified branch prediction for the kernel by default"
> @@ -732,22 +721,6 @@ config VFIO_AP
>  
>  endmenu
>  
> -menu "Dump support"
> -
> -config CRASH_DUMP
> -	bool "kernel crash dumps"
> -	select KEXEC
> -	help
> -	  Generate crash dump after being started by kexec.
> -	  Crash dump kernels are loaded in the main kernel with kexec-tools
> -	  into a specially reserved region and then later executed after
> -	  a crash by kdump/kexec.
> -	  Refer to <file:Documentation/s390/zfcpdump.rst> for more details on this.
> -	  This option also enables s390 zfcpdump.
> -	  See also <file:Documentation/s390/zfcpdump.rst>
> -
> -endmenu
> -
>  config CCW
>  	def_bool y

Acked-by: Alexander Gordeev <agordeev@...ux.ibm.com>