Date:   Wed, 14 Jun 2023 06:54:05 -0500
From:   Eric DeVolder <eric.devolder@...cle.com>
To:     "Leizhen (ThunderTown)" <thunder.leizhen@...wei.com>,
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Subject: Re: [PATCH v1 01/21] kexec: consolidate kexec and crash options into
 kernel/Kconfig.kexec



On 6/13/23 20:19, Leizhen (ThunderTown) wrote:
> 
> 
> 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@...cle.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.
> 
I'll remove the extra spaces.

>> +
>> +	  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.
> 
Good catch, I'll remove MODULE_SIG_FORMAT and place it on just s390 (which is the only arch that had 
it this way).

>> +	help
>> +
> 
> This blank line can be deleted.
> 
I will remove it.

Thank you, Zhen!
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.
>> +
>> +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
>>
> 

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