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linux/kernel/Kconfig.kexec
Arnd Bergmann 7844d7d8d8 kexec: select CRYPTO from KEXEC_FILE instead of depending on it 
[ Upstream commit e63bde3d94 ]

All other users of crypto code use 'select' instead of 'depends on', so do
the same thing with KEXEC_FILE for consistency.

In practice this makes very little difference as kernels with kexec
support are very likely to also include some other feature that already
selects both crypto and crypto_sha256, but being consistent here helps for
usability as well as to avoid potential circular dependencies.

This reverts the dependency back to what it was originally before commit
74ca317c26 ("kexec: create a new config option CONFIG_KEXEC_FILE for
new syscall"), which changed changed it with the comment "This should be
safer as "select" is not recursive", but that appears to have been done in
error, as "select" is indeed recursive, and there are no other
dependencies that prevent CRYPTO_SHA256 from being selected here.

Link: https://lkml.kernel.org/r/20231023110308.1202042-2-arnd@kernel.org
Fixes: 74ca317c26 ("kexec: create a new config option CONFIG_KEXEC_FILE for new syscall")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Eric DeVolder <eric_devolder@yahoo.com>
Tested-by: Eric DeVolder <eric_devolder@yahoo.com>
Acked-by: Baoquan He <bhe@redhat.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Conor Dooley <conor@kernel.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2024-01-05 15:19:41 +01:00

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# 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"
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
select CRYPTO_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"
depends on ARCH_SUPPORTS_CRASH_DUMP
select CRASH_CORE
select KEXEC_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>
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.
endmenu
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