Re: [PATCH v5 02/13] x86/kexec: refactor for kernel/Kconfig.kexec

[Christophe Leroy <christophe.leroy@csgroup.eu>]

Le 07/07/2023 à 00:20, Eric DeVolder a écrit :
> 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.


Why do you need to duplicate the ARCH_SELECTS_ entries in each 
architecture ?

Why not define them in arch/Kconfig then select if from each architecture ?

For instance here for x86 for ARCH_SELECTS_KEXEC_FILE all you'll have to 
do is:
	select ARCH_SELECTS_KEXEC_FILE if KEXEC_FILE
	select HAVE_IMA_KEXEC if IMA && KEXEC_FILE


Christophe

> 
> Signed-off-by: Eric DeVolder <eric.devolder@oracle.com>
> ---
>   arch/x86/Kconfig | 92 ++++++++++--------------------------------------
>   1 file changed, 19 insertions(+), 73 deletions(-)
> 
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 7422db409770..9767a343f7c2 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -2040,88 +2040,34 @@ config EFI_RUNTIME_MAP
>   
>   source "kernel/Kconfig.hz"
>   
> -config KEXEC
> -	bool "kexec system call"
> -	select KEXEC_CORE
> -	help
> -	  kexec is a system call that implements the ability to shutdown your
> -	  current kernel, and to start another kernel.  It is like a reboot
> -	  but it is independent of the system firmware.   And like a reboot
> -	  you can start any kernel with it, not just Linux.
> -
> -	  The name comes from the similarity to the exec system call.
> -
> -	  It is an ongoing process to be certain the hardware in a machine
> -	  is properly shutdown, so do not be surprised if this code does not
> -	  initially work for you.  As of this writing the exact hardware
> -	  interface is strongly in flux, so no good recommendation can be
> -	  made.
> -
> -config KEXEC_FILE
> -	bool "kexec file based system call"
> -	select KEXEC_CORE
> -	select HAVE_IMA_KEXEC if IMA
> -	depends on X86_64
> -	depends on CRYPTO=y
> -	depends on CRYPTO_SHA256=y
> -	help
> -	  This is new version of kexec system call. This system call is
> -	  file based and takes file descriptors as system call argument
> -	  for kernel and initramfs as opposed to list of segments as
> -	  accepted by previous system call.
> +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 KEXEC_SIG
> -	bool "Verify kernel signature during kexec_file_load() syscall"
> +config ARCH_SELECTS_KEXEC_FILE
> +	def_bool y
>   	depends on KEXEC_FILE
> -	help
> +	select HAVE_IMA_KEXEC if IMA
>   
> -	  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.
> +config ARCH_HAS_KEXEC_PURGATORY
> +	def_bool KEXEC_FILE
>   
> -	  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.
> +config ARCH_SUPPORTS_KEXEC_SIG
> +	def_bool y
>   
> -config KEXEC_SIG_FORCE
> -	bool "Require a valid signature in kexec_file_load() syscall"
> -	depends on KEXEC_SIG
> -	help
> -	  This option makes kernel signature verification mandatory for
> -	  the kexec_file_load() syscall.
> +config ARCH_SUPPORTS_KEXEC_SIG_FORCE
> +	def_bool y
>   
> -config KEXEC_BZIMAGE_VERIFY_SIG
> -	bool "Enable bzImage signature verification support"
> -	depends on KEXEC_SIG
> -	depends on SIGNED_PE_FILE_VERIFICATION
> -	select SYSTEM_TRUSTED_KEYRING
> -	help
> -	  Enable bzImage signature verification support.
> +config ARCH_SUPPORTS_KEXEC_BZIMAGE_VERIFY_SIG
> +	def_bool y
>   
> -config CRASH_DUMP
> -	bool "kernel crash dumps"
> -	depends on X86_64 || (X86_32 && HIGHMEM)
> -	help
> -	  Generate crash dump after being started by kexec.
> -	  This should be normally only set in special crash dump kernels
> -	  which are loaded in the main kernel with kexec-tools into
> -	  a specially reserved region and then later executed after
> -	  a crash by kdump/kexec. The crash dump kernel must be compiled
> -	  to a memory address not used by the main kernel or BIOS using
> -	  PHYSICAL_START, or it must be built as a relocatable image
> -	  (CONFIG_RELOCATABLE=y).
> -	  For more details see Documentation/admin-guide/kdump/kdump.rst
> +config ARCH_SUPPORTS_KEXEC_JUMP
> +	def_bool y
>   
> -config KEXEC_JUMP
> -	bool "kexec jump"
> -	depends on KEXEC && HIBERNATION
> -	help
> -	  Jump between original kernel and kexeced kernel and invoke
> -	  code in physical address mode via KEXEC
> +config ARCH_SUPPORTS_CRASH_DUMP
> +	def_bool X86_64 || (X86_32 && HIGHMEM)
>   
>   config PHYSICAL_START
>   	hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)