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 15.1.2507.23; Wed, 14 Jun 2023 09:19:38 +0800
Subject: Re: [PATCH v1 01/21] kexec: consolidate kexec and crash options into
 kernel/Kconfig.kexec
To: Eric DeVolder <eric.devolder@oracle.com>, <linux@armlinux.org.uk>,
	<catalin.marinas@arm.com>, <will@kernel.org>, <chenhuacai@kernel.org>,
	<geert@linux-m68k.org>, <tsbogend@alpha.franken.de>,
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References: <20230612172805.681179-1-eric.devolder@oracle.com>
 <20230612172805.681179-2-eric.devolder@oracle.com>
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On 2023/6/13 1:27, Eric DeVolder wrote:
> The config options for kexec and crash features are consolidated
> into new file kernel/Kconfig.kexec. Under the "General Setup" submenu
> is a new submenu "Kexec and crash handling" where all the kexec and
> crash options that were once in the arch-dependent submenu "Processor
> type and features" are now consolidated.
> 
> The following options are impacted:
> 
>  - KEXEC
>  - KEXEC_FILE
>  - KEXEC_SIG
>  - KEXEC_SIG_FORCE
>  - KEXEC_BZIMAGE_VERIFY_SIG
>  - KEXEC_JUMP
>  - CRASH_DUMP
> 
> The three main options are KEXEC, KEXEC_FILE and CRASH_DUMP.
> 
> Architectures specify support of certain KEXEC and CRASH features with
> similarly named new ARCH_HAS_<option> config options.
> 
> Architectures can utilize the new ARCH_SUPPORTS_<option> config
> options to specify additional components when <option> is enabled.
> 
> To summarize, the ARCH_HAS_<option> permits the <option> to be
> enabled, and the ARCH_SUPPORTS_<option> handles side effects (ie.
> select statements).
> 
> Signed-off-by: Eric DeVolder <eric.devolder@oracle.com>
> ---
>  arch/Kconfig         |  13 ------
>  init/Kconfig         |   2 +
>  kernel/Kconfig.kexec | 103 +++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 105 insertions(+), 13 deletions(-)
>  create mode 100644 kernel/Kconfig.kexec
> 
> diff --git a/arch/Kconfig b/arch/Kconfig
> index 205fd23e0cad..a37730679730 100644
> --- a/arch/Kconfig
> +++ b/arch/Kconfig
> @@ -11,19 +11,6 @@ source "arch/$(SRCARCH)/Kconfig"
>  
>  menu "General architecture-dependent options"
>  
> -config CRASH_CORE
> -	bool
> -
> -config KEXEC_CORE
> -	select CRASH_CORE
> -	bool
> -
> -config KEXEC_ELF
> -	bool
> -
> -config HAVE_IMA_KEXEC
> -	bool
> -
>  config ARCH_HAS_SUBPAGE_FAULTS
>  	bool
>  	help
> diff --git a/init/Kconfig b/init/Kconfig
> index 32c24950c4ce..4424447e23a5 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -1917,6 +1917,8 @@ config BINDGEN_VERSION_TEXT
>  config TRACEPOINTS
>  	bool
>  
> +source "kernel/Kconfig.kexec"
> +
>  endmenu		# General setup
>  
>  source "arch/Kconfig"
> diff --git a/kernel/Kconfig.kexec b/kernel/Kconfig.kexec
> new file mode 100644
> index 000000000000..660048099865
> --- /dev/null
> +++ b/kernel/Kconfig.kexec
> @@ -0,0 +1,103 @@
> +# SPDX-License-Identifier: GPL-2.0-only
> +
> +menu "Kexec and crash features"
> +
> +config CRASH_CORE
> +	bool
> +
> +config KEXEC_CORE
> +	select CRASH_CORE
> +	bool
> +
> +config KEXEC_ELF
> +	bool
> +
> +config HAVE_IMA_KEXEC
> +	bool
> +
> +config KEXEC
> +	bool "Enable kexec system call"
> +	default ARCH_DEFAULT_KEXEC
> +	depends on ARCH_HAS_KEXEC
> +	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.

"kernel.  It is like", "firmware.   And like"

A few more spaces, I don't know the original author's intention, perhaps can be removed.

> +
> +	  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 "Enable kexec file based system call"
> +	depends on ARCH_HAS_KEXEC_FILE
> +	select KEXEC_CORE
> +	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 KEXEC_SIG
> +	bool "Verify kernel signature during kexec_file_load() syscall"
> +	depends on KEXEC_FILE && MODULE_SIG_FORMAT

I see that there is no "depends on MODULE_SIG_FORMAT" on x86 and arm64.

> +	help
> +

This blank line can be deleted.

> +	  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.
> +
> +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 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 KEXEC_JUMP
> +	bool "kexec jump"
> +	depends on KEXEC && HIBERNATION
> +	depends on ARCH_HAS_KEXEC_JUMP
> +	help
> +	  Jump between original kernel and kexeced kernel and invoke
> +	  code in physical address mode via KEXEC
> +
> +config CRASH_DUMP
> +	bool "kernel crash dumps"
> +	depends on ARCH_HAS_CRASH_DUMP
> +	select KEXEC_CORE
> +	select CRASH_CORE
> +	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
> +
> +	  For s390, this option also enables zfcpdump.
> +	  See also <file:Documentation/s390/zfcpdump.rst>
> +
> +endmenu
> 

-- 
Regards,
  Zhen Lei