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Message-ID: <715506f0-083d-0dc6-f1a1-781d025e4d15@oracle.com>
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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