[PATCH v6 00/14] refactor Kconfig to consolidate KEXEC and CRASH options
Eric DeVolder
eric.devolder at oracle.com
Wed Jul 12 09:15:31 PDT 2023
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@oracle.com/
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.
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_SUPPORTS_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_SUPPORTS_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).
Regards,
eric
---
v6: 12jul2023
- More cycles with randconfig has revealed problems relating to
MODULE_SIG_FORMAT/SYSTEM_DATA_VERIFICATION on s390. This version
solves the problem by placing MODULE_SIG_FORMAT on the
ARCH_SUPPORTS_KEXEC_SIG def_bool statement, similar to original.
- Added patch to rename ARCH_HAS_KEXEC_PURGATORY to
ARCH_SUPPORTS_KEXEC_PURGATORY to follow convention agreed upon
since v2.
- Re-run regressions locally including failing randconfig config
files reported.
v5: 6jul2023
https://lore.kernel.org/lkml/20230706222027.189117-1-eric.devolder@oracle.com/
- Filled out all common options with a 'depends on ARCH_SUPPORTS_
<option>' and provided it in the needed archs. Result of testing
with allnoconfig and allyesconfig.
- Added 'depends on ARCH_SUPPORTS_KEXEC' to CRASH_DUMP, per Arnd
Bergmann.
- Investigated fails revealed by Andrew Morton's machinery, and
spot tested with this solution.
v4: 5jul2023
https://lore.kernel.org/lkml/20230705142004.3605799-1-eric.devolder@oracle.com/
- Corrected conversion issue with riscv, per Conor Dooley.
- Andrew Mortons's akpm test machinery found a problem with config
files generated by randconfig. The problem existed prior to this
series and manifests because most arch/<arch>/Kconfig CRASH_DUMP
does not have any dependencies on KEXEC. As a result, randconfig
produces a config file enabling CRASH_DUMP but not KEXEC, which
leads to compile/link-time problems. Andrew requested closing
this hole. To that end 'select KEXEC' has been added to CRASH_DUMP.
This behavior pre-existed for arm arm64 ia64 loongarch mips powerpc
riscv sh and x86.
- Applied Acked-by's from:
s390: Alexander Gordeev <agordeev at linux.ibm.com>
v3: 26jun2023
https://lore.kernel.org/lkml/20230626161332.183214-1-eric.devolder@oracle.com/
- Rebased onto 6.4.0
- Reworded s390 commit message to clarify MODULE_SIG_FORMAT,
per Alexander Gordeev
- Applied Acked-by's from:
m68k: Geert Uytterhoeven <geert at linux-m68k.org>
mips: Thomas Bogendoerfer <tsbogend at alpha.franken.de>
sh: John Paul Adrian Glaubitz <glaubitz at physik.fu-berlin.de>
v2: 19jun2023
https://lore.kernel.org/lkml/20230619145801.1064716-1-eric.devolder@oracle.com/
- The ARCH_HAS_ and ARCH_SUPPORTS_ combination was found to be
too similar/confusing. Renamed these two new options as such:
ARCH_HAS_<option> ---> ARCH_SUPPORTS_<option>
ARCH_SUPPORTS_<option> ---> ARCH_SELECTS_<option>
Per Kees Cook, Michael Ellerman
NOTE: ARCH_HAS_KEXEC_PURGATORY was left as-is, as that is what
it is prior to this series.
Updated this cover letter to reflect the same.
- Some minor cleaning up of the help sections, per Zhen Lei and
Alexander Gordeev.
- Removed the MODULE_SIG_FORMAT dependency from KEXEC_SIG in
kernel/Kconfig.kexec. Only s390 had it prior to this series.
See also commit message in
"s390/kexec: refactor for kernel/Kconfig.kexec"
- Added to Kconfig.kexec the KEXEC_IMAGE_VERIFY_SIG from arm64,
per Zhen Lei.
- Fixed the powerpc ARCH_SUPPORTS_KEXEC_FILE conversion, per
Michael Ellerman.
v1: 12jun2023
https://lore.kernel.org/lkml/20230612172805.681179-1-eric.devolder@oracle.com/
- Initial
- Based on 6.4.0-rc6
---
Eric DeVolder (14):
kexec: consolidate kexec and crash options into kernel/Kconfig.kexec
x86/kexec: refactor for kernel/Kconfig.kexec
arm/kexec: refactor for kernel/Kconfig.kexec
ia64/kexec: refactor for kernel/Kconfig.kexec
arm64/kexec: refactor for kernel/Kconfig.kexec
loongarch/kexec: refactor for kernel/Kconfig.kexec
m68k/kexec: refactor for kernel/Kconfig.kexec
mips/kexec: refactor for kernel/Kconfig.kexec
parisc/kexec: refactor for kernel/Kconfig.kexec
powerpc/kexec: refactor for kernel/Kconfig.kexec
riscv/kexec: refactor for kernel/Kconfig.kexec
s390/kexec: refactor for kernel/Kconfig.kexec
sh/kexec: refactor for kernel/Kconfig.kexec
kexec: rename ARCH_HAS_KEXEC_PURGATORY
arch/Kconfig | 13 ----
arch/arm/Kconfig | 29 ++-------
arch/arm64/Kconfig | 64 +++++--------------
arch/ia64/Kconfig | 28 ++------
arch/loongarch/Kconfig | 26 ++------
arch/m68k/Kconfig | 19 +-----
arch/mips/Kconfig | 32 ++--------
arch/parisc/Kconfig | 34 ++++------
arch/powerpc/Kconfig | 57 ++++++-----------
arch/riscv/Kbuild | 2 +-
arch/riscv/Kconfig | 46 ++++----------
arch/riscv/kernel/elf_kexec.c | 4 +-
arch/s390/Kbuild | 2 +-
arch/s390/Kconfig | 69 +++++++-------------
arch/sh/Kconfig | 46 +++-----------
arch/x86/Kconfig | 92 ++++++---------------------
init/Kconfig | 2 +
kernel/Kconfig.kexec | 116 ++++++++++++++++++++++++++++++++++
kernel/kexec_file.c | 6 +-
19 files changed, 257 insertions(+), 430 deletions(-)
create mode 100644 kernel/Kconfig.kexec
--
2.31.1
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