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Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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menu "Kexec and crash features"
config CRASH_RESERVE bool
config VMCORE_INFO bool
config KEXEC_CORE bool
config KEXEC_ELF bool
config HAVE_IMA_KEXEC bool
config KEXEC bool "Enable kexec system call" depends on ARCH_SUPPORTS_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.
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_SUPPORTS_KEXEC_FILE select CRYPTO_LIB_SHA256 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 kexec system call.
config KEXEC_SIG bool "Verify kernel signature during kexec_file_load() syscall" depends on ARCH_SUPPORTS_KEXEC_SIG depends on KEXEC_FILE help 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 ARCH_SUPPORTS_KEXEC_SIG_FORCE depends on KEXEC_SIG help This option makes kernel signature verification mandatory for the kexec_file_load() syscall.
config KEXEC_IMAGE_VERIFY_SIG bool "Enable Image signature verification support (ARM)" default ARCH_DEFAULT_KEXEC_IMAGE_VERIFY_SIG depends on ARCH_SUPPORTS_KEXEC_IMAGE_VERIFY_SIG depends on KEXEC_SIG depends on EFI && SIGNED_PE_FILE_VERIFICATION help Enable Image signature verification support.
config KEXEC_BZIMAGE_VERIFY_SIG bool "Enable bzImage signature verification support" depends on ARCH_SUPPORTS_KEXEC_BZIMAGE_VERIFY_SIG 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 ARCH_SUPPORTS_KEXEC_JUMP depends on KEXEC && HIBERNATION help Jump between original kernel and kexeced kernel and invoke code in physical address mode via KEXEC
config CRASH_DUMP bool "kernel crash dumps" default ARCH_DEFAULT_CRASH_DUMP depends on ARCH_SUPPORTS_CRASH_DUMP depends on KEXEC_CORE select VMCORE_INFO select CRASH_RESERVE 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/arch/s390/zfcpdump.rst>
config CRASH_DM_CRYPT bool "Support saving crash dump to dm-crypt encrypted volume" depends on KEXEC_FILE depends on CRASH_DUMP depends on DM_CRYPT depends on KEYS help With this option enabled, user space can intereact with /sys/kernel/config/crash_dm_crypt_keys to make the dm crypt keys persistent for the dump-capture kernel.
config CRASH_DM_CRYPT_CONFIGS def_tristate CRASH_DM_CRYPT select CONFIGFS_FS help CRASH_DM_CRYPT cannot directly select CONFIGFS_FS, because that is required to be built-in.
config CRASH_DUMP_KUNIT_TEST tristate "Unit Tests for kernel crash dumps" if !KUNIT_ALL_TESTS depends on CRASH_DUMP && KUNIT default KUNIT_ALL_TESTS help This option builds KUnit unit tests for kernel crash dumps. The unit tests will be used to verify the correctness of covered functions and also prevent any regression.
If unsure, say N.
config CRASH_HOTPLUG bool "Update the crash elfcorehdr on system configuration changes" default y depends on CRASH_DUMP && (HOTPLUG_CPU || MEMORY_HOTPLUG) depends on ARCH_SUPPORTS_CRASH_HOTPLUG help Enable direct update to the crash elfcorehdr (which contains the list of CPUs and memory regions to be dumped upon a crash) in response to hot plug/unplug or online/offline of CPUs or memory. This is a much more advanced approach than userspace attempting that.
If unsure, say Y.
config CRASH_MAX_MEMORY_RANGES int "Specify the maximum number of memory regions for the elfcorehdr" default 8192 depends on CRASH_HOTPLUG help For the kexec_file_load() syscall path, specify the maximum number of memory regions that the elfcorehdr buffer/segment can accommodate. These regions are obtained via walk_system_ram_res(); eg. the 'System RAM' entries in /proc/iomem. This value is combined with NR_CPUS_DEFAULT and multiplied by sizeof(Elf64_Phdr) to determine the final elfcorehdr memory buffer/ segment size. The value 8192, for example, covers a (sparsely populated) 1TiB system consisting of 128MiB memblocks, while resulting in an elfcorehdr memory buffer/segment size under 1MiB. This represents a sane choice to accommodate both baremetal and virtual machine configurations.
For the kexec_load() syscall path, CRASH_MAX_MEMORY_RANGES is part of the computation behind the value provided through the /sys/kernel/crash_elfcorehdr_size attribute.
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