The patch titled
Subject: kexec: consolidate kexec and crash options into kernel/Kconfig.kexec
has been added to the -mm mm-nonmm-unstable branch. Its filename is
kexec-consolidate-kexec-and-crash-options-into-kernel-kconfigkexec.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/kexec-consolidate-kexec-and-crash-options-into-kernel-kconfigkexec.patch
This patch will later appear in the mm-nonmm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Eric DeVolder <eric.devolder@xxxxxxxxxx>
Subject: kexec: consolidate kexec and crash options into kernel/Kconfig.kexec
Date: Thu, 6 Jul 2023 18:20:15 -0400
Patch series "refactor Kconfig to consolidate KEXEC and CRASH options",
v5.
The Kconfig is refactored to consolidate KEXEC and CRASH options from
various arch/<arch>/Kconfig files into new file kernel/Kconfig.kexec.
The Kconfig.kexec is now a submenu titled "Kexec and crash features"
located under "General Setup".
The following options are impacted:
- KEXEC
- KEXEC_FILE
- KEXEC_SIG
- KEXEC_SIG_FORCE
- KEXEC_IMAGE_VERIFY_SIG
- KEXEC_BZIMAGE_VERIFY_SIG
- KEXEC_JUMP
- CRASH_DUMP
Over time, these options have been copied between Kconfig files and
are very similar to one another, but with slight differences.
The following architectures are impacted by the refactor (because of
use of one or more KEXEC/CRASH options):
- arm
- arm64
- ia64
- loongarch
- m68k
- mips
- parisc
- powerpc
- riscv
- s390
- sh
- x86
More information:
In the patch series "crash: Kernel handling of CPU and memory hot
un/plug"
https://lore.kernel.org/lkml/20230503224145.7405-1-eric.devolder@xxxxxxxxxx/
the new kernel feature introduces the config option CRASH_HOTPLUG.
In reviewing, Thomas Gleixner requested that the new config option
not be placed in x86 Kconfig. Rather the option needs a generic/common
home. To Thomas' point, the KEXEC and CRASH options have largely been
duplicated in the various arch/<arch>/Kconfig files, with minor
differences. This kind of proliferation is to be avoid/stopped.
https://lore.kernel.org/lkml/875y91yv63.ffs@tglx/
To that end, I have refactored the arch Kconfigs so as to consolidate
the various KEXEC and CRASH options. Generally speaking, this work has
the following themes:
- KEXEC and CRASH options are moved into new file kernel/Kconfig.kexec
- These items from arch/Kconfig:
CRASH_CORE KEXEC_CORE KEXEC_ELF HAVE_IMA_KEXEC
- These items from arch/x86/Kconfig form the common options:
KEXEC KEXEC_FILE KEXEC_SIG KEXEC_SIG_FORCE
KEXEC_BZIMAGE_VERIFY_SIG KEXEC_JUMP CRASH_DUMP
- These items from arch/arm64/Kconfig form the common options:
KEXEC_IMAGE_VERIFY_SIG
- The crash hotplug series appends CRASH_HOTPLUG to Kconfig.kexec
- The Kconfig.kexec is now a submenu titled "Kexec and crash features"
and is now listed in "General Setup" submenu from init/Kconfig.
- To control the common options, each has a new ARCH_SUPPORTS_<option>
option. These gateway options determine whether the common options
options are valid for the architecture.
- To account for the slight differences in the original architecture
coding of the common options, each now has a corresponding
ARCH_SELECTS_<option> which are used to elicit the same side effects
as the original arch/<arch>/Kconfig files for KEXEC and CRASH options.
- NOTE: The existing ARCH_HAS_KEXEC_PURGATORY remains unchanged.
An example, 'make menuconfig' illustrating the submenu:
> General setup > Kexec and crash features
[*] Enable kexec system call
[*] Enable kexec file based system call
[*] Verify kernel signature during kexec_file_load() syscall
[ ] Require a valid signature in kexec_file_load() syscall
[ ] Enable bzImage signature verification support
[*] kexec jump
[*] kernel crash dumps
[*] Update the crash elfcorehdr on system configuration changes
In the process of consolidating the common options, I encountered
slight differences in the coding of these options in several of the
architectures. As a result, I settled on the following solution:
- Each of the common options has a 'depends on ARCH_SUPPORTS_<option>'
statement. For example, the KEXEC_FILE option has a 'depends on
ARCH_SUPPORTS_KEXEC_FILE' statement.
This approach is needed on all common options so as to prevent
options from appearing for architectures which previously did
not allow/enable them. For example, arm supports KEXEC but not
KEXEC_FILE. The arch/arm/Kconfig does not provide
ARCH_SUPPORTS_KEXEC_FILE and so KEXEC_FILE and related options
are not available to arm.
- The boolean ARCH_SUPPORTS_<option> in effect allows the arch to
determine when the feature is allowed. Archs which don't have the
feature simply do not provide the corresponding ARCH_SUPPORTS_<option>.
For each arch, where there previously were KEXEC and/or CRASH
options, these have been replaced with the corresponding boolean
ARCH_SUPPORTS_<option>, and an appropriate def_bool statement.
For example, if the arch supports KEXEC_FILE, then the
ARCH_SUPPORTS_KEXEC_FILE simply has a 'def_bool y'. This permits
the KEXEC_FILE option to be available.
If the arch has a 'depends on' statement in its original coding
of the option, then that expression becomes part of the def_bool
expression. For example, arm64 had:
config KEXEC
depends on PM_SLEEP_SMP
and in this solution, this converts to:
config ARCH_SUPPORTS_KEXEC
def_bool PM_SLEEP_SMP
- In order to account for the architecture differences in the
coding for the common options, the ARCH_SELECTS_<option> in the
arch/<arch>/Kconfig is used. This option has a 'depends on
<option>' statement to couple it to the main option, and from
there can insert the differences from the common option and the
arch original coding of that option.
For example, a few archs enable CRYPTO and CRYTPO_SHA256 for
KEXEC_FILE. These require a ARCH_SELECTS_KEXEC_FILE and
'select CRYPTO' and 'select CRYPTO_SHA256' statements.
Illustrating the option relationships:
For each of the common KEXEC and CRASH options:
ARCH_SUPPORTS_<option> <- <option> <- ARCH_SELECTS_<option>
<option> # in Kconfig.kexec
ARCH_SUPPORTS_<option> # in arch/<arch>/Kconfig, as needed
ARCH_SELECTS_<option> # in arch/<arch>/Kconfig, as needed
For example, KEXEC:
ARCH_SUPPORTS_KEXEC <- KEXEC <- ARCH_SELECTS_KEXEC
KEXEC # in Kconfig.kexec
ARCH_SUPPORTS_KEXEC # in arch/<arch>/Kconfig, as needed
ARCH_SELECTS_KEXEC # in arch/<arch>/Kconfig, as needed
To summarize, the ARCH_SUPPORTS_<option> permits the <option> to be
enabled, and the ARCH_SELECTS_<option> handles side effects (ie.
select statements).
Examples:
A few examples to show the new strategy in action:
===== x86 (minus the help section) =====
Original:
config KEXEC
bool "kexec system call"
select KEXEC_CORE
config KEXEC_FILE
bool "kexec file based system call"
select KEXEC_CORE
select HAVE_IMA_KEXEC if IMA
depends on X86_64
depends on CRYPTO=y
depends on CRYPTO_SHA256=y
config ARCH_HAS_KEXEC_PURGATORY
def_bool KEXEC_FILE
config KEXEC_SIG
bool "Verify kernel signature during kexec_file_load() syscall"
depends on KEXEC_FILE
config KEXEC_SIG_FORCE
bool "Require a valid signature in kexec_file_load() syscall"
depends on KEXEC_SIG
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
config CRASH_DUMP
bool "kernel crash dumps"
depends on X86_64 || (X86_32 && HIGHMEM)
config KEXEC_JUMP
bool "kexec jump"
depends on KEXEC && HIBERNATION
help
becomes...
New:
config ARCH_SUPPORTS_KEXEC
def_bool y
config ARCH_SUPPORTS_KEXEC_FILE
def_bool X86_64 && CRYPTO && CRYPTO_SHA256
config ARCH_SELECTS_KEXEC_FILE
def_bool y
depends on KEXEC_FILE
select HAVE_IMA_KEXEC if IMA
config ARCH_HAS_KEXEC_PURGATORY
def_bool KEXEC_FILE
config ARCH_SUPPORTS_KEXEC_SIG
def_bool y
config ARCH_SUPPORTS_KEXEC_SIG_FORCE
def_bool y
config ARCH_SUPPORTS_KEXEC_BZIMAGE_VERIFY_SIG
def_bool y
config ARCH_SUPPORTS_KEXEC_JUMP
def_bool y
config ARCH_SUPPORTS_CRASH_DUMP
def_bool X86_64 || (X86_32 && HIGHMEM)
===== powerpc (minus the help section) =====
Original:
config KEXEC
bool "kexec system call"
depends on PPC_BOOK3S || PPC_E500 || (44x && !SMP)
select KEXEC_CORE
config KEXEC_FILE
bool "kexec file based system call"
select KEXEC_CORE
select HAVE_IMA_KEXEC if IMA
select KEXEC_ELF
depends on PPC64
depends on CRYPTO=y
depends on CRYPTO_SHA256=y
config ARCH_HAS_KEXEC_PURGATORY
def_bool KEXEC_FILE
config CRASH_DUMP
bool "Build a dump capture kernel"
depends on PPC64 || PPC_BOOK3S_32 || PPC_85xx || (44x && !SMP)
select RELOCATABLE if PPC64 || 44x || PPC_85xx
becomes...
New:
config ARCH_SUPPORTS_KEXEC
def_bool PPC_BOOK3S || PPC_E500 || (44x && !SMP)
config ARCH_SUPPORTS_KEXEC_FILE
def_bool PPC64 && CRYPTO=y && CRYPTO_SHA256=y
config ARCH_HAS_KEXEC_PURGATORY
def_bool KEXEC_FILE
config ARCH_SELECTS_KEXEC_FILE
def_bool y
depends on KEXEC_FILE
select KEXEC_ELF
select HAVE_IMA_KEXEC if IMA
config ARCH_SUPPORTS_CRASH_DUMP
def_bool PPC64 || PPC_BOOK3S_32 || PPC_85xx || (44x && !SMP)
config ARCH_SELECTS_CRASH_DUMP
def_bool y
depends on CRASH_DUMP
select RELOCATABLE if PPC64 || 44x || PPC_85xx
Testing Approach and Results
There are 388 config files in the arch/<arch>/configs directories.
For each of these config files, a .config is generated both before and
after this Kconfig series, and checked for equivalence. This approach
allows for a rather rapid check of all architectures and a wide
variety of configs wrt/ KEXEC and CRASH, and avoids requiring
compiling for all architectures and running kernels and run-time
testing.
For each config file, the olddefconfig, allnoconfig and allyesconfig
targets are utilized. In testing the randconfig has revealed problems
as well, but is not used in the before and after equivalence check
since one can not generate the "same" .config for before and after,
even if using the same KCONFIG_SEED since the option list is
different.
As such, the following script steps compare the before and after
of 'make olddefconfig'. The new symbols introduced by this series
are filtered out, but otherwise the config files are PASS only if
they were equivalent, and FAIL otherwise.
The script performs the test by doing the following:
# Obtain the "golden" .config output for given config file
# Reset test sandbox
git checkout master
git branch -D test_Kconfig
git checkout -B test_Kconfig master
make distclean
# Write out updated config
cp -f <config file> .config
make ARCH=<arch> olddefconfig
# Track each item in .config, LHSB is "golden"
scoreboard .config
# Obtain the "changed" .config output for given config file
# Reset test sandbox
make distclean
# Apply this Kconfig series
git am <this Kconfig series>
# Write out updated config
cp -f <config file> .config
make ARCH=<arch> olddefconfig
# Track each item in .config, RHSB is "changed"
scoreboard .config
# Determine test result
# Filter-out new symbols introduced by this series
# Filter-out symbol=n which not in either scoreboard
# Compare LHSB "golden" and RHSB "changed" scoreboards and issue PASS/FAIL
The script was instrumental during the refactoring of Kconfig as it
continually revealed problems. The end result being that the solution
presented in this series passes all configs as checked by the script,
with the following exceptions:
- arch/ia64/configs/zx1_config with olddefconfig
This config file has:
# CONFIG_KEXEC is not set
CONFIG_CRASH_DUMP=y
and this refactor now couples KEXEC to CRASH_DUMP, so it is not
possible to enable CRASH_DUMP without KEXEC.
- arch/sh/configs/* with allyesconfig
The arch/sh/Kconfig codes CRASH_DUMP as dependent upon BROKEN_ON_MMU
(which clearly is not meant to be set). This symbol is not provided
but with the allyesconfig it is set to yes which enables CRASH_DUMP.
But KEXEC is coded as dependent upon MMU, and is set to no in
arch/sh/mm/Kconfig, so KEXEC is not enabled.
This refactor now couples KEXEC to CRASH_DUMP, so it is not
possible to enable CRASH_DUMP without KEXEC.
While the above exceptions are not equivalent to their original,
the config file produced is valid (and in fact better wrt/ CRASH_DUMP
handling).
This patch (of 13):
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". All the kexec and crash options that
were once in the arch-dependent submenu "Processor type and features" are
now consolidated in the new submenu.
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_SUPPORTS_<option> config options.
Architectures can utilize the new ARCH_SELECTS_<option> config
options to specify additional components when <option> is enabled.
To summarize, the ARCH_SUPPORTS_<option> permits the <option> to be
enabled, and the ARCH_SELECTS_<option> handles side effects (ie.
select statements).
Link: https://lkml.kernel.org/r/20230706222027.189117-1-eric.devolder@xxxxxxxxxx
Link: https://lkml.kernel.org/r/20230706222027.189117-2-eric.devolder@xxxxxxxxxx
Signed-off-by: Eric DeVolder <eric.devolder@xxxxxxxxxx>
Cc: Alexander Gordeev <agordeev@xxxxxxxxxxxxx>
Cc: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
Cc: John Paul Adrian Glaubitz <glaubitz@xxxxxxxxxxxxxxxxxxx>
Cc: Sourabh Jain <sourabhjain@xxxxxxxxxxxxx>
Cc: Thomas Bogendoerfer <tsbogend@xxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/Kconfig | 13 ----
init/Kconfig | 2
kernel/Kconfig.kexec | 116 +++++++++++++++++++++++++++++++++++++++++
3 files changed, 118 insertions(+), 13 deletions(-)
--- a/arch/Kconfig~kexec-consolidate-kexec-and-crash-options-into-kernel-kconfigkexec
+++ a/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
--- a/init/Kconfig~kexec-consolidate-kexec-and-crash-options-into-kernel-kconfigkexec
+++ a/init/Kconfig
@@ -1927,6 +1927,8 @@ config BINDGEN_VERSION_TEXT
config TRACEPOINTS
bool
+source "kernel/Kconfig.kexec"
+
endmenu # General setup
source "arch/Kconfig"
--- /dev/null
+++ a/kernel/Kconfig.kexec
@@ -0,0 +1,116 @@
+# 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_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 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
+ depends on ARCH_SUPPORTS_KEXEC
+ select CRASH_CORE
+ select KEXEC_CORE
+ select KEXEC
+ 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
_
Patches currently in -mm which might be from eric.devolder@xxxxxxxxxx are
kexec-consolidate-kexec-and-crash-options-into-kernel-kconfigkexec.patch
x86-kexec-refactor-for-kernel-kconfigkexec.patch
arm-kexec-refactor-for-kernel-kconfigkexec.patch
ia64-kexec-refactor-for-kernel-kconfigkexec.patch
arm64-kexec-refactor-for-kernel-kconfigkexec.patch
loongarch-kexec-refactor-for-kernel-kconfigkexec.patch
m68k-kexec-refactor-for-kernel-kconfigkexec.patch
mips-kexec-refactor-for-kernel-kconfigkexec.patch
parisc-kexec-refactor-for-kernel-kconfigkexec.patch
powerpc-kexec-refactor-for-kernel-kconfigkexec.patch
riscv-kexec-refactor-for-kernel-kconfigkexec.patch
s390-kexec-refactor-for-kernel-kconfigkexec.patch
sh-kexec-refactor-for-kernel-kconfigkexec.patch
