[PATCH v2 00/13] refactor Kconfig to consolidate KEXEC and CRASH options

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_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
  - The crash hotplug series appends CRASH_HOTPLUG to Kconfig.kexec
  NOTE: PHYSICAL_START could be argued to be included in this series.
- The Kconfig.kexec is now a submenu titled "Kexec and crash features"
- The Kconfig.kexec is now listed in "General Setup" submenu from
  init/Kconfig
- To control the main common options, new options ARCH_SUPPORTS_KEXEC,
  ARCH_SUPPORTS_KEXEC_FILE and ARCH_SUPPORTS_CRASH_DUMP are introduced.
  NOTE: The existing ARCH_HAS_KEXEC_PURGATORY remains unchanged.
- To account for the slight differences, new options ARCH_SELECTS_KEXEC,
  ARCH_SELECTS_KEXEC_FILE and ARCH_SELECTS_CRASH_DUMP 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

The three main options are KEXEC, KEXEC_FILE and CRASH_DUMP. In the
process of consolidating these 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 three main options has a 'depends on ARCH_SUPPORTS_<option>'
  statement: ARCH_SUPPORTS_KEXEC, ARCH_SUPPORTS_KEXEC_FILE,
  ARCH_SUPPORTS_CRASH_DUMP.

  For example, the KEXEC_FILE option has a 'depends on
  ARCH_SUPPORTS_KEXEC_FILE' statement.

- 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 differences in the config coding for
  the three common options, the ARCH_SELECTS_<option> is used.
  This options 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 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


For KEXEC_FILE:
 ARCH_SUPPORTS_KEXEC_FILE <- KEXEC_FILE <- ARCH_SELECTS_KEXEC_FILE

 KEXEC_FILE                 # in Kconfig.kexec
 ARCH_SUPPORTS_KEXEC_FILE   # in arch/<arch>/Kconfig, as needed
 ARCH_SELECTS_KEXEC_FILE    # in arch/<arch>/Kconfig, as needed


For CRASH:
 ARCH_SUPPORTS_CRASH_DUMP <- CRASH_DUMP <- ARCH_SELECTS_CRASH_DUMP

 CRASH_DUMP                 # in Kconfig.kexec
 ARCH_SUPPORTS_CRASH_DUMP   # in arch/<arch>/Kconfig, as needed
 ARCH_SELECTS_CRASH_DUMP    # 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_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.

As such, I developed the following script to 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.

Regards,
eric

---
v2: 19jun2023
 - The ARCH_HAS_ and ARCH_SUPPORTS_ combination was found to be
   too similar. 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 (13):
  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

 arch/Kconfig           |  13 -----
 arch/arm/Kconfig       |  29 ++---------
 arch/arm64/Kconfig     |  62 +++++------------------
 arch/ia64/Kconfig      |  28 ++---------
 arch/loongarch/Kconfig |  26 +++-------
 arch/m68k/Kconfig      |  19 +------
 arch/mips/Kconfig      |  32 ++----------
 arch/parisc/Kconfig    |  34 +++++--------
 arch/powerpc/Kconfig   |  55 +++++++--------------
 arch/riscv/Kconfig     |  48 ++++++------------
 arch/s390/Kconfig      |  65 +++++++-----------------
 arch/sh/Kconfig        |  46 +++--------------
 arch/x86/Kconfig       |  89 +++++----------------------------
 init/Kconfig           |   2 +
 kernel/Kconfig.kexec   | 110 +++++++++++++++++++++++++++++++++++++++++
 15 files changed, 229 insertions(+), 429 deletions(-)
 create mode 100644 kernel/Kconfig.kexec

-- 
2.31.1

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_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).

Signed-off-by: Eric DeVolder <redacted>
---
 arch/Kconfig         |  13 -----
 init/Kconfig         |   2 +
 kernel/Kconfig.kexec | 110 +++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 112 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..5d576ddfd999
--- /dev/null
+++ b/kernel/Kconfig.kexec

@@ -0,0 +1,110 @@
+# 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 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 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"
+	default ARCH_DEFAULT_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 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_SUPPORTS_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_SUPPORTS_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

-- 
2.31.1

The kexec and crash kernel options are provided in the common
kernel/Kconfig.kexec. Utilize the common options and provide
the ARCH_SUPPORTS_ and ARCH_SELECTS_ entries to recreate the
equivalent set of KEXEC and CRASH options.

Signed-off-by: Eric DeVolder <redacted>
---
 arch/x86/Kconfig | 89 +++++++-----------------------------------------
 1 file changed, 13 insertions(+), 76 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 53bab123a8ee..1afc6ca2986b 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig

@@ -2043,88 +2043,25 @@ config EFI_RUNTIME_MAP
 
 source "kernel/Kconfig.hz"
 
-config KEXEC
-	bool "kexec system call"
-	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 "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
-	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 ARCH_SUPPORTS_KEXEC
+	def_bool y
 
-config ARCH_HAS_KEXEC_PURGATORY
-	def_bool KEXEC_FILE
+config ARCH_SUPPORTS_KEXEC_FILE
+	def_bool X86_64 && CRYPTO && CRYPTO_SHA256
 
-config KEXEC_SIG
-	bool "Verify kernel signature during kexec_file_load() syscall"
+config ARCH_SELECTS_KEXEC_FILE
+	def_bool y
 	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 KEXEC_SIG
-	help
-	  This option makes kernel signature verification mandatory for
-	  the kexec_file_load() syscall.
+	select HAVE_IMA_KEXEC if IMA
 
-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 ARCH_HAS_KEXEC_PURGATORY
+	def_bool KEXEC_FILE
 
-config CRASH_DUMP
-	bool "kernel crash dumps"
-	depends on X86_64 || (X86_32 && HIGHMEM)
-	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
+config ARCH_SUPPORTS_KEXEC_JUMP
+	def_bool y
 
-config KEXEC_JUMP
-	bool "kexec jump"
-	depends on KEXEC && HIBERNATION
-	help
-	  Jump between original kernel and kexeced kernel and invoke
-	  code in physical address mode via KEXEC
+config ARCH_SUPPORTS_CRASH_DUMP
+	def_bool X86_64 || (X86_32 && HIGHMEM)
 
 config PHYSICAL_START
 	hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)

-- 
2.31.1

Hi Eric,

On 06/19/23 at 10:57am, Eric DeVolder wrote:
......

+config ARCH_SUPPORTS_KEXEC
+	def_bool y
 
-config ARCH_HAS_KEXEC_PURGATORY
-	def_bool KEXEC_FILE
+config ARCH_SUPPORTS_KEXEC_FILE
+	def_bool X86_64 && CRYPTO && CRYPTO_SHA256

......  

+config ARCH_SELECTS_KEXEC_FILE
+	def_bool y
 	depends on KEXEC_FILE
-	help

I am a little confused about this ARCH_SELECTS_XX adding. Wondering what
limits us defining the ARCH_SUPPORTS_KEXEC_FILE like below? I have limited
knowledge about Kconfig, please correct me if I am wrong. Thanks in
advance.

 +config ARCH_SUPPORTS_KEXEC_FILE
 +	def_bool y
  	depends on KEXEC_FILE
  	depends on X86_64 && CRYPTO && CRYPTO_SHA256

-
-	  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.
-

On 6/20/23 03:21, Baoquan He wrote:

Hi Eric,

On 06/19/23 at 10:57am, Eric DeVolder wrote:
......

quoted

+config ARCH_SUPPORTS_KEXEC
+	def_bool y
  
-config ARCH_HAS_KEXEC_PURGATORY
-	def_bool KEXEC_FILE
+config ARCH_SUPPORTS_KEXEC_FILE
+	def_bool X86_64 && CRYPTO && CRYPTO_SHA256

......

quoted

+config ARCH_SELECTS_KEXEC_FILE
+	def_bool y
  	depends on KEXEC_FILE
-	help

I am a little confused about this ARCH_SELECTS_XX adding. Wondering what
limits us defining the ARCH_SUPPORTS_KEXEC_FILE like below? I have limited
knowledge about Kconfig, please correct me if I am wrong. Thanks in
advance.

  +config ARCH_SUPPORTS_KEXEC_FILE
  +	def_bool y
   	depends on KEXEC_FILE
   	depends on X86_64 && CRYPTO && CRYPTO_SHA256

For the ARCH_SUPPORTS_ options, I chose to list the dependencies on the def_bool line to show that 
it took all those conditions to result in True.
However, as you point out, using a def_bool y and then listing them as 'depends on' works as well.
Probably would have resulted in fewer changes to the Kconfig file.
Either way is ok (the 'depends on KEXEC_FILE' is erroneous in your example).
eric

quoted

-
-	  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.
-

On 06/20/23 at 07:56am, Eric DeVolder wrote:

On 6/20/23 03:21, Baoquan He wrote:

quoted

Hi Eric,

On 06/19/23 at 10:57am, Eric DeVolder wrote:
......

quoted

+config ARCH_SUPPORTS_KEXEC
+	def_bool y
-config ARCH_HAS_KEXEC_PURGATORY
-	def_bool KEXEC_FILE
+config ARCH_SUPPORTS_KEXEC_FILE
+	def_bool X86_64 && CRYPTO && CRYPTO_SHA256

......

quoted

+config ARCH_SELECTS_KEXEC_FILE
+	def_bool y
  	depends on KEXEC_FILE
-	help

I am a little confused about this ARCH_SELECTS_XX adding. Wondering what
limits us defining the ARCH_SUPPORTS_KEXEC_FILE like below? I have limited
knowledge about Kconfig, please correct me if I am wrong. Thanks in
advance.

  +config ARCH_SUPPORTS_KEXEC_FILE
  +	def_bool y
   	depends on KEXEC_FILE
   	depends on X86_64 && CRYPTO && CRYPTO_SHA256

For the ARCH_SUPPORTS_ options, I chose to list the dependencies on the
def_bool line to show that it took all those conditions to result in True.
However, as you point out, using a def_bool y and then listing them as 'depends on' works as well.
Probably would have resulted in fewer changes to the Kconfig file.
Either way is ok (the 'depends on KEXEC_FILE' is erroneous in your example).

Got it, thanks. To me, one option with explicit dependencies looks clearer
and straightforward. I need check and investigage why two options are needed,
whether two options are unavoidable. Not sure if other people would get
the same feeling or not. Honestly, it's my first time to see the usage of
XXX_SELECTS_XXX, it took me a while to dig into.

quoted

quoted

-
-	  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.
-

The kexec and crash kernel options are provided in the common
kernel/Kconfig.kexec. Utilize the common options and provide
the ARCH_SUPPORTS_ and ARCH_SELECTS_ entries to recreate the
equivalent set of KEXEC and CRASH options.

Signed-off-by: Eric DeVolder <redacted>
Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
---
 arch/m68k/Kconfig | 19 ++-----------------
 1 file changed, 2 insertions(+), 17 deletions(-)

diff --git a/arch/m68k/Kconfig b/arch/m68k/Kconfig
index 40198a1ebe27..7b71916d1519 100644
--- a/arch/m68k/Kconfig
+++ b/arch/m68k/Kconfig

@@ -88,23 +88,8 @@ config MMU_SUN3
 	bool
 	depends on MMU && !MMU_MOTOROLA && !MMU_COLDFIRE
 
-config KEXEC
-	bool "kexec system call"
-	depends on M68KCLASSIC && MMU
-	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 ARCH_SUPPORTS_KEXEC
+	def_bool M68KCLASSIC && MMU
 
 config BOOTINFO_PROC
 	bool "Export bootinfo in procfs"

-- 
2.31.1

The kexec and crash kernel options are provided in the common
kernel/Kconfig.kexec. Utilize the common options and provide
the ARCH_SUPPORTS_ and ARCH_SELECTS_ entries to recreate the
equivalent set of KEXEC and CRASH options.

Signed-off-by: Eric DeVolder <redacted>
---
 arch/arm64/Kconfig | 62 +++++++++-------------------------------------
 1 file changed, 12 insertions(+), 50 deletions(-)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 343e1e1cae10..dfe47efa7cc1 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig

@@ -1433,60 +1433,22 @@ config PARAVIRT_TIME_ACCOUNTING
 
 	  If in doubt, say N here.
 
-config KEXEC
-	depends on PM_SLEEP_SMP
-	select KEXEC_CORE
-	bool "kexec system call"
-	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.
-
-config KEXEC_FILE
-	bool "kexec file based system call"
-	select KEXEC_CORE
-	select HAVE_IMA_KEXEC if IMA
-	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
-	help
-	  Select this option to verify a signature with loaded kernel
-	  image. If configured, any attempt of loading a image without
-	  valid signature will fail.
-
-	  In addition to that option, you need to enable signature
-	  verification for the corresponding kernel image type being
-	  loaded in order for this to work.
+config ARCH_SUPPORTS_KEXEC
+	def_bool PM_SLEEP_SMP
 
-config KEXEC_IMAGE_VERIFY_SIG
-	bool "Enable Image signature verification support"
-	default y
-	depends on KEXEC_SIG
-	depends on EFI && SIGNED_PE_FILE_VERIFICATION
-	help
-	  Enable Image signature verification support.
+config ARCH_SUPPORTS_KEXEC_FILE
+	def_bool y
 
-comment "Support for PE file signature verification disabled"
-	depends on KEXEC_SIG
-	depends on !EFI || !SIGNED_PE_FILE_VERIFICATION
+config ARCH_SELECTS_KEXEC_FILE
+	def_bool y
+	depends on KEXEC_FILE
+	select HAVE_IMA_KEXEC if IMA
 
-config CRASH_DUMP
-	bool "Build kdump crash kernel"
-	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.
+config ARCH_DEFAULT_KEXEC_IMAGE_VERIFY_SIG
+	def_bool y
 
-	  For more details see Documentation/admin-guide/kdump/kdump.rst
+config ARCH_SUPPORTS_CRASH_DUMP
+	def_bool y
 
 config TRANS_TABLE
 	def_bool y

-- 
2.31.1

The kexec and crash kernel options are provided in the common
kernel/Kconfig.kexec. Utilize the common options and provide
the ARCH_SUPPORTS_ and ARCH_SELECTS_ entries to recreate the
equivalent set of KEXEC and CRASH options.

Signed-off-by: Eric DeVolder <redacted>
---
 arch/parisc/Kconfig | 34 +++++++++++-----------------------
 1 file changed, 11 insertions(+), 23 deletions(-)

diff --git a/arch/parisc/Kconfig b/arch/parisc/Kconfig
index 967bde65dd0e..8de24bc503aa 100644
--- a/arch/parisc/Kconfig
+++ b/arch/parisc/Kconfig

@@ -348,29 +348,17 @@ config NR_CPUS
 	default "4" if 64BIT
 	default "16"
 
-config KEXEC
-	bool "Kexec system call"
-	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.
-
-	  It is an ongoing process to be certain the hardware in a machine
-	  shutdown, so do not be surprised if this code does not
-	  initially work for you.
-
-config KEXEC_FILE
-	bool "kexec file based system call"
-	select KEXEC_CORE
-	select KEXEC_ELF
-	help
-	  This enables the kexec_file_load() System call. This 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.
-
 endmenu
 
+config ARCH_SUPPORTS_KEXEC
+	def_bool y
+
+config ARCH_SUPPORTS_KEXEC_FILE
+	def_bool y
+
+config ARCH_SELECTS_KEXEC_FILE
+	def_bool y
+	depends on KEXEC_FILE
+	select KEXEC_ELF
+
 source "drivers/parisc/Kconfig"

-- 
2.31.1

The kexec and crash kernel options are provided in the common
kernel/Kconfig.kexec. Utilize the common options and provide
the ARCH_SUPPORTS_ and ARCH_SELECTS_ entries to recreate the
equivalent set of KEXEC and CRASH options.

Signed-off-by: Eric DeVolder <redacted>
---
 arch/sh/Kconfig | 46 ++++++++--------------------------------------
 1 file changed, 8 insertions(+), 38 deletions(-)

diff --git a/arch/sh/Kconfig b/arch/sh/Kconfig
index 9652d367fc37..d52e0beed7e9 100644
--- a/arch/sh/Kconfig
+++ b/arch/sh/Kconfig

@@ -546,44 +546,14 @@ menu "Kernel features"
 
 source "kernel/Kconfig.hz"
 
-config KEXEC
-	bool "kexec system call (EXPERIMENTAL)"
-	depends on MMU
-	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 CRASH_DUMP
-	bool "kernel crash dumps (EXPERIMENTAL)"
-	depends on BROKEN_ON_SMP
-	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 using
-	  PHYSICAL_START.
-
-	  For more details see Documentation/admin-guide/kdump/kdump.rst
-
-config KEXEC_JUMP
-	bool "kexec jump (EXPERIMENTAL)"
-	depends on KEXEC && HIBERNATION
-	help
-	  Jump between original kernel and kexeced kernel and invoke
-	  code via KEXEC
+config ARCH_SUPPORTS_KEXEC
+	def_bool MMU
+
+config ARCH_SUPPORTS_CRASH_DUMP
+	def_bool BROKEN_ON_SMP
+
+config ARCH_SUPPORTS_KEXEC_JUMP
+	def_bool y
 
 config PHYSICAL_START
 	hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)

-- 
2.31.1

Hi Eric!

On Mon, 2023-06-19 at 10:58 -0400, Eric DeVolder wrote:

Acked-by: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>

-- 
 .''`.  John Paul Adrian Glaubitz
: :' :  Debian Developer
`. `'   Physicist
  `-    GPG: 62FF 8A75 84E0 2956 9546  0006 7426 3B37 F5B5 F913

On 6/19/23 13:21, John Paul Adrian Glaubitz wrote:

Acked-by: John Paul Adrian Glaubitz<glaubitz@physik.fu-berlin.de>

Thank you!
eric

The kexec and crash kernel options are provided in the common
kernel/Kconfig.kexec. Utilize the common options and provide
the ARCH_SUPPORTS_ and ARCH_SELECTS_ entries to recreate the
equivalent set of KEXEC and CRASH options.

NOTE: The original Kconfig has a KEXEC_SIG which depends on
MODULE_SIG_FORMAT. However, attempts to keep the MODULE_SIG_FORMAT
dependency (using the strategy outlined in this series, and other
techniques) results in 'error: recursive dependency detected'
on CRYPTO. This occurs due to any path through KEXEC_SIG
attempting to select CRYPTO is ultimately dependent upon CRYPTO:

 CRYPTO
  <- ARCH_SUPPORTS_KEXEC_FILE
     <- KEXEC_FILE
        <- KEXEC_SIG

Therefore, the solution is to drop the MODULE_SIG_FORMAT dependency
for KEXEC_SIG. In practice, however, MODULE_SIG_FORMAT is still
configured-in as the use of KEXEC_SIG is in step with the use of
SYSTEM_DATA_VERIFICATION, which does select MODULE_SIG_FORMAT.
Not ideal, but results in equivalent .config files for s390.

Signed-off-by: Eric DeVolder <redacted>
---
 arch/s390/Kconfig | 65 ++++++++++++++---------------------------------
 1 file changed, 19 insertions(+), 46 deletions(-)

diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index 6dab9c1be508..58dc124433ca 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig

@@ -243,6 +243,25 @@ config PGTABLE_LEVELS
 
 source "kernel/livepatch/Kconfig"
 
+config ARCH_DEFAULT_KEXEC
+	def_bool y
+
+config ARCH_SUPPORTS_KEXEC
+	def_bool y
+
+config ARCH_SUPPORTS_KEXEC_FILE
+	def_bool CRYPTO && CRYPTO_SHA256 && CRYPTO_SHA256_S390
+
+config ARCH_HAS_KEXEC_PURGATORY
+	def_bool KEXEC_FILE
+
+config ARCH_SUPPORTS_CRASH_DUMP
+	def_bool y
+	help
+	  Refer to <file:Documentation/s390/zfcpdump.rst> for more details on this.
+	  This option also enables s390 zfcpdump.
+	  See also <file:Documentation/s390/zfcpdump.rst>
+
 menu "Processor type and features"
 
 config HAVE_MARCH_Z10_FEATURES

@@ -481,36 +500,6 @@ config SCHED_TOPOLOGY
 
 source "kernel/Kconfig.hz"
 
-config KEXEC
-	def_bool y
-	select KEXEC_CORE
-
-config KEXEC_FILE
-	bool "kexec file based system call"
-	select KEXEC_CORE
-	depends on CRYPTO
-	depends on CRYPTO_SHA256
-	depends on CRYPTO_SHA256_S390
-	help
-	  Enable the kexec file based system call. In contrast to the normal
-	  kexec system call this system call takes file descriptors for the
-	  kernel and initramfs as arguments.
-
-config ARCH_HAS_KEXEC_PURGATORY
-	def_bool y
-	depends on KEXEC_FILE
-
-config KEXEC_SIG
-	bool "Verify kernel signature during kexec_file_load() syscall"
-	depends on KEXEC_FILE && MODULE_SIG_FORMAT
-	help
-	  This option makes kernel signature verification mandatory for
-	  the kexec_file_load() syscall.
-
-	  In addition to that option, you need to enable signature
-	  verification for the corresponding kernel image type being
-	  loaded in order for this to work.
-
 config KERNEL_NOBP
 	def_bool n
 	prompt "Enable modified branch prediction for the kernel by default"

@@ -732,22 +721,6 @@ config VFIO_AP
 
 endmenu
 
-menu "Dump support"
-
-config CRASH_DUMP
-	bool "kernel crash dumps"
-	select KEXEC
-	help
-	  Generate crash dump after being started by kexec.
-	  Crash dump kernels are loaded in the main kernel with kexec-tools
-	  into a specially reserved region and then later executed after
-	  a crash by kdump/kexec.
-	  Refer to <file:Documentation/s390/zfcpdump.rst> for more details on this.
-	  This option also enables s390 zfcpdump.
-	  See also <file:Documentation/s390/zfcpdump.rst>
-
-endmenu
-
 config CCW
 	def_bool y
 

-- 
2.31.1

On Mon, Jun 19, 2023 at 10:58:00AM -0400, Eric DeVolder wrote:

Hi Eric,

The kexec and crash kernel options are provided in the common
kernel/Kconfig.kexec. Utilize the common options and provide
the ARCH_SUPPORTS_ and ARCH_SELECTS_ entries to recreate the
equivalent set of KEXEC and CRASH options.

NOTE: The original Kconfig has a KEXEC_SIG which depends on
MODULE_SIG_FORMAT. However, attempts to keep the MODULE_SIG_FORMAT
dependency (using the strategy outlined in this series, and other
techniques) results in 'error: recursive dependency detected'
on CRYPTO. This occurs due to any path through KEXEC_SIG
attempting to select CRYPTO is ultimately dependent upon CRYPTO:

 CRYPTO
  <- ARCH_SUPPORTS_KEXEC_FILE
     <- KEXEC_FILE
        <- KEXEC_SIG

Therefore, the solution is to drop the MODULE_SIG_FORMAT dependency
for KEXEC_SIG. In practice, however, MODULE_SIG_FORMAT is still
configured-in as the use of KEXEC_SIG is in step with the use of
SYSTEM_DATA_VERIFICATION, which does select MODULE_SIG_FORMAT.

No, it is actually the other way around.
Could you please provide the correct explanation?

AFAICT the MODULE_SIG_FORMAT dependency was introduced with commit
c8424e776b09 ("MODSIGN: Export module signature definitions") and
in fact was not necessary, since s390 did/does not use mod_check_sig()
anyway. So the SYSTEM_DATA_VERIFICATION could have left intact.

However, the original SYSTEM_DATA_VERIFICATION seems sane and I do
not understand why other architectures do not have it also? May be
Mimi Zohar (putting on CC) could explain that?

It looks like such dependency actually exists in implicit form
(which you picked from x86):

	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.

Does it mean that if an architecture did not enable the signature
verification type explicitly the linker could fail - both before
and after you series?

Thanks!

On 6/21/23 00:00, Alexander Gordeev wrote:

On Mon, Jun 19, 2023 at 10:58:00AM -0400, Eric DeVolder wrote:

Hi Eric,

quoted

The kexec and crash kernel options are provided in the common
kernel/Kconfig.kexec. Utilize the common options and provide
the ARCH_SUPPORTS_ and ARCH_SELECTS_ entries to recreate the
equivalent set of KEXEC and CRASH options.

NOTE: The original Kconfig has a KEXEC_SIG which depends on
MODULE_SIG_FORMAT. However, attempts to keep the MODULE_SIG_FORMAT
dependency (using the strategy outlined in this series, and other
techniques) results in 'error: recursive dependency detected'
on CRYPTO. This occurs due to any path through KEXEC_SIG
attempting to select CRYPTO is ultimately dependent upon CRYPTO:

  CRYPTO
   <- ARCH_SUPPORTS_KEXEC_FILE
      <- KEXEC_FILE
         <- KEXEC_SIG

Therefore, the solution is to drop the MODULE_SIG_FORMAT dependency
for KEXEC_SIG. In practice, however, MODULE_SIG_FORMAT is still
configured-in as the use of KEXEC_SIG is in step with the use of
SYSTEM_DATA_VERIFICATION, which does select MODULE_SIG_FORMAT.

No, it is actually the other way around.
Could you please provide the correct explanation?

AFAICT the MODULE_SIG_FORMAT dependency was introduced with commit
c8424e776b09 ("MODSIGN: Export module signature definitions") and
in fact was not necessary, since s390 did/does not use mod_check_sig()
anyway. So the SYSTEM_DATA_VERIFICATION could have left intact.

Thomas, would the correct explanation be simply indicating that MODULE_SIG_FORMAT isn't needed as it 
is not used by s390 (crediting your summary above)?

However, the original SYSTEM_DATA_VERIFICATION seems sane and I do
not understand why other architectures do not have it also? May be
Mimi Zohar (putting on CC) could explain that?

It looks like such dependency actually exists in implicit form
(which you picked from x86):

	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.

Does it mean that if an architecture did not enable the signature
verification type explicitly the linker could fail - both before
and after you series?

As a quick test I checked x86 and it compiles/links ok if KEXEC_SIG and KEXEC_SIG_FORCE are 
configured-in, but KEXEC_BZIMAGE_VERIFY_SIG (used for x86 sig verify) is not. The reason being that 
the kexec_image_verify_sig() function checks if the fops.verify_sig is non-NULL before invoking the 
verification. If it is NULL, the sig check fails. This would appear to be valid outcome for other 
archs as well.

At any rate, I think attempting to determine if other archs need SYSTEM_DATA_VERIFICATION is out of 
the scope of this series; I'm targeting just the refactor to be equivalent to what is what prior.

Thanks for looking at this!
eric

Thanks!

quoted

Not ideal, but results in equivalent .config files for s390.

Signed-off-by: Eric DeVolder <redacted>
---
  arch/s390/Kconfig | 65 ++++++++++++++---------------------------------
  1 file changed, 19 insertions(+), 46 deletions(-)

diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index 6dab9c1be508..58dc124433ca 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig

@@ -243,6 +243,25 @@ config PGTABLE_LEVELS
  
  source "kernel/livepatch/Kconfig"
  
+config ARCH_DEFAULT_KEXEC
+	def_bool y
+
+config ARCH_SUPPORTS_KEXEC
+	def_bool y
+
+config ARCH_SUPPORTS_KEXEC_FILE
+	def_bool CRYPTO && CRYPTO_SHA256 && CRYPTO_SHA256_S390
+
+config ARCH_HAS_KEXEC_PURGATORY
+	def_bool KEXEC_FILE
+
+config ARCH_SUPPORTS_CRASH_DUMP
+	def_bool y
+	help
+	  Refer to <file:Documentation/s390/zfcpdump.rst> for more details on this.
+	  This option also enables s390 zfcpdump.
+	  See also <file:Documentation/s390/zfcpdump.rst>
+
  menu "Processor type and features"
  
  config HAVE_MARCH_Z10_FEATURES

@@ -481,36 +500,6 @@ config SCHED_TOPOLOGY
  
  source "kernel/Kconfig.hz"
  
-config KEXEC
-	def_bool y
-	select KEXEC_CORE
-
-config KEXEC_FILE
-	bool "kexec file based system call"
-	select KEXEC_CORE
-	depends on CRYPTO
-	depends on CRYPTO_SHA256
-	depends on CRYPTO_SHA256_S390
-	help
-	  Enable the kexec file based system call. In contrast to the normal
-	  kexec system call this system call takes file descriptors for the
-	  kernel and initramfs as arguments.
-
-config ARCH_HAS_KEXEC_PURGATORY
-	def_bool y
-	depends on KEXEC_FILE
-
-config KEXEC_SIG
-	bool "Verify kernel signature during kexec_file_load() syscall"
-	depends on KEXEC_FILE && MODULE_SIG_FORMAT
-	help
-	  This option makes kernel signature verification mandatory for
-	  the kexec_file_load() syscall.
-
-	  In addition to that option, you need to enable signature
-	  verification for the corresponding kernel image type being
-	  loaded in order for this to work.
-
  config KERNEL_NOBP
  	def_bool n
  	prompt "Enable modified branch prediction for the kernel by default"

@@ -732,22 +721,6 @@ config VFIO_AP
  
  endmenu
  
-menu "Dump support"
-
-config CRASH_DUMP
-	bool "kernel crash dumps"
-	select KEXEC
-	help
-	  Generate crash dump after being started by kexec.
-	  Crash dump kernels are loaded in the main kernel with kexec-tools
-	  into a specially reserved region and then later executed after
-	  a crash by kdump/kexec.
-	  Refer to <file:Documentation/s390/zfcpdump.rst> for more details on this.
-	  This option also enables s390 zfcpdump.
-	  See also <file:Documentation/s390/zfcpdump.rst>
-
-endmenu
-
  config CCW
  	def_bool y
  

-- 
2.31.1

On Wed, Jun 21, 2023 at 12:10:49PM -0500, Eric DeVolder wrote:
Hi Eric,
...

quoted

quoted

NOTE: The original Kconfig has a KEXEC_SIG which depends on
MODULE_SIG_FORMAT. However, attempts to keep the MODULE_SIG_FORMAT
dependency (using the strategy outlined in this series, and other
techniques) results in 'error: recursive dependency detected'
on CRYPTO. This occurs due to any path through KEXEC_SIG
attempting to select CRYPTO is ultimately dependent upon CRYPTO:

  CRYPTO
   <- ARCH_SUPPORTS_KEXEC_FILE
      <- KEXEC_FILE
         <- KEXEC_SIG

Therefore, the solution is to drop the MODULE_SIG_FORMAT dependency
for KEXEC_SIG. In practice, however, MODULE_SIG_FORMAT is still
configured-in as the use of KEXEC_SIG is in step with the use of
SYSTEM_DATA_VERIFICATION, which does select MODULE_SIG_FORMAT.

No, it is actually the other way around.
Could you please provide the correct explanation?

AFAICT the MODULE_SIG_FORMAT dependency was introduced with commit
c8424e776b09 ("MODSIGN: Export module signature definitions") and
in fact was not necessary, since s390 did/does not use mod_check_sig()
anyway. So the SYSTEM_DATA_VERIFICATION could have left intact.

Thomas, would the correct explanation be simply indicating that
MODULE_SIG_FORMAT isn't needed as it is not used by s390 (crediting your
summary above)?

I guess, you asked me? Anyway, I will try to answer as if I were Thomas :)

MODULE_SIG_FORMAT is needed to select SYSTEM_DATA_VERIFICATION.
But SYSTEM_DATA_VERIFICATION is also selected by FS_VERITY*, so
dropping MODULE_SIG_FORMAT does not hurt.

Thanks!

On 6/22/23 11:24, Alexander Gordeev wrote:

On Wed, Jun 21, 2023 at 12:10:49PM -0500, Eric DeVolder wrote:
Hi Eric,
...

quoted

quoted

quoted

NOTE: The original Kconfig has a KEXEC_SIG which depends on
MODULE_SIG_FORMAT. However, attempts to keep the MODULE_SIG_FORMAT
dependency (using the strategy outlined in this series, and other
techniques) results in 'error: recursive dependency detected'
on CRYPTO. This occurs due to any path through KEXEC_SIG
attempting to select CRYPTO is ultimately dependent upon CRYPTO:

   CRYPTO
    <- ARCH_SUPPORTS_KEXEC_FILE
       <- KEXEC_FILE
          <- KEXEC_SIG

Therefore, the solution is to drop the MODULE_SIG_FORMAT dependency
for KEXEC_SIG. In practice, however, MODULE_SIG_FORMAT is still
configured-in as the use of KEXEC_SIG is in step with the use of
SYSTEM_DATA_VERIFICATION, which does select MODULE_SIG_FORMAT.

No, it is actually the other way around.
Could you please provide the correct explanation?

AFAICT the MODULE_SIG_FORMAT dependency was introduced with commit
c8424e776b09 ("MODSIGN: Export module signature definitions") and
in fact was not necessary, since s390 did/does not use mod_check_sig()
anyway. So the SYSTEM_DATA_VERIFICATION could have left intact.

Thomas, would the correct explanation be simply indicating that
MODULE_SIG_FORMAT isn't needed as it is not used by s390 (crediting your
summary above)?

I guess, you asked me? Anyway, I will try to answer as if I were Thomas :)

MODULE_SIG_FORMAT is needed to select SYSTEM_DATA_VERIFICATION.
But SYSTEM_DATA_VERIFICATION is also selected by FS_VERITY*, so
dropping MODULE_SIG_FORMAT does not hurt.

Thanks!

For the commit message for this s390/Kconfig change, are you ok
with the following?
eric

=====
The kexec and crash kernel options are provided in the common
kernel/Kconfig.kexec. Utilize the common options and provide
the ARCH_SUPPORTS_ and ARCH_SELECTS_ entries to recreate the
equivalent set of KEXEC and CRASH options.

NOTE: The original Kconfig has a KEXEC_SIG which depends on
MODULE_SIG_FORMAT. However, attempts to keep the MODULE_SIG_FORMAT
dependency (using the strategy outlined in this series, and other
techniques) results in 'error: recursive dependency detected'
on CRYPTO.

Per Alexander Gordeev [off-list ref]: "the MODULE_SIG_FORMAT
dependency was introduced with c8424e776b09 ("MODSIGN: Export module
signature definitions") and in fact was not necessary, since s390
did/does not use mod_check_sig() anyway. MODULE_SIG_FORMAT is needed
to select SYSTEM_DATA_VERIFICATION. But SYSTEM_DATA_VERIFICATION is
also selected by FS_VERITY*, so dropping MODULE_SIG_FORMAT does not
hurt."

Therefore, the solution is to drop the MODULE_SIG_FORMAT dependency
from KEXEC_SIG.

On Wed, 2023-06-21 at 07:00 +0200, Alexander Gordeev wrote:

AFAICT the MODULE_SIG_FORMAT dependency was introduced with commit
c8424e776b09 ("MODSIGN: Export module signature definitions") and
in fact was not necessary, since s390 did/does not use mod_check_sig()
anyway. So the SYSTEM_DATA_VERIFICATION could have left intact.

FYI, this patch was included in the patch set to allow IMA to verify
the kexec kernel image appended signature on OpenPOWER.

-- 
thanks,

Mimi

The kexec and crash kernel options are provided in the common
kernel/Kconfig.kexec. Utilize the common options and provide
the ARCH_SUPPORTS_ and ARCH_SELECTS_ entries to recreate the
equivalent set of KEXEC and CRASH options.

Signed-off-by: Eric DeVolder <redacted>
---
 arch/arm/Kconfig | 29 ++++-------------------------
 1 file changed, 4 insertions(+), 25 deletions(-)

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 0fb4b218f665..6af0105407af 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig

@@ -1639,20 +1639,8 @@ config XIP_DEFLATED_DATA
 	  copied, saving some precious ROM space. A possible drawback is a
 	  slightly longer boot delay.
 
-config KEXEC
-	bool "Kexec system call (EXPERIMENTAL)"
-	depends on (!SMP || PM_SLEEP_SMP)
-	depends on MMU
-	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.
-
-	  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.
+config ARCH_SUPPORTS_KEXEC
+	def_bool (!SMP || PM_SLEEP_SMP) && MMU
 
 config ATAGS_PROC
 	bool "Export atags in procfs"

@@ -1662,17 +1650,8 @@ config ATAGS_PROC
 	  Should the atags used to boot the kernel be exported in an "atags"
 	  file in procfs. Useful with kexec.
 
-config CRASH_DUMP
-	bool "Build kdump crash kernel (EXPERIMENTAL)"
-	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
-
-	  For more details see Documentation/admin-guide/kdump/kdump.rst
+config ARCH_SUPPORTS_CRASH_DUMP
+	def_bool y
 
 config AUTO_ZRELADDR
 	bool "Auto calculation of the decompressed kernel image address" if !ARCH_MULTIPLATFORM

-- 
2.31.1

The kexec and crash kernel options are provided in the common
kernel/Kconfig.kexec. Utilize the common options and provide
the ARCH_SUPPORTS_ and ARCH_SELECTS_ entries to recreate the
equivalent set of KEXEC and CRASH options.

Signed-off-by: Eric DeVolder <redacted>
Reviewed-by: Sourabh Jain <redacted>
---
 arch/powerpc/Kconfig | 55 ++++++++++++++------------------------------
 1 file changed, 17 insertions(+), 38 deletions(-)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index bff5820b7cda..70edbda08ae3 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig

@@ -588,41 +588,21 @@ config PPC64_SUPPORTS_MEMORY_FAILURE
 	default "y" if PPC_POWERNV
 	select ARCH_SUPPORTS_MEMORY_FAILURE
 
-config KEXEC
-	bool "kexec system call"
-	depends on PPC_BOOK3S || PPC_E500 || (44x && !SMP)
-	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 "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
-	help
-	  This is a new version of the kexec system call. This call is
-	  file based and takes in file descriptors as system call arguments
-	  for kernel and initramfs as opposed to a list of segments as is the
-	  case for the older kexec call.
+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 PPC64_BIG_ENDIAN_ELF_ABI_V2
 	bool "Build big-endian kernel using ELF ABI V2 (EXPERIMENTAL)"
 	depends on PPC64 && CPU_BIG_ENDIAN

@@ -682,14 +662,13 @@ config RELOCATABLE_TEST
 	  loaded at, which tends to be non-zero and therefore test the
 	  relocation code.
 
-config CRASH_DUMP
-	bool "Build a dump capture kernel"
-	depends on PPC64 || PPC_BOOK3S_32 || PPC_85xx || (44x && !SMP)
+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
-	help
-	  Build a kernel suitable for use as a dump capture kernel.
-	  The same kernel binary can be used as production kernel and dump
-	  capture kernel.
 
 config FA_DUMP
 	bool "Firmware-assisted dump"

-- 
2.31.1

The kexec and crash kernel options are provided in the common
kernel/Kconfig.kexec. Utilize the common options and provide
the ARCH_SUPPORTS_ and ARCH_SELECTS_ entries to recreate the
equivalent set of KEXEC and CRASH options.

Signed-off-by: Eric DeVolder <redacted>
---
 arch/ia64/Kconfig | 28 +++++-----------------------
 1 file changed, 5 insertions(+), 23 deletions(-)

diff --git a/arch/ia64/Kconfig b/arch/ia64/Kconfig
index 21fa63ce5ffc..df54a038e6da 100644
--- a/arch/ia64/Kconfig
+++ b/arch/ia64/Kconfig

@@ -360,31 +360,13 @@ config IA64_HP_AML_NFW
 	  the "force" module parameter, e.g., with the "aml_nfw.force"
 	  kernel command line option.
 
-config KEXEC
-	bool "kexec system call"
-	depends on !SMP || HOTPLUG_CPU
-	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.
+endmenu
 
-config CRASH_DUMP
-	  bool "kernel crash dumps"
-	  depends on IA64_MCA_RECOVERY && (!SMP || HOTPLUG_CPU)
-	  help
-	    Generate crash dump after being started by kexec.
+config ARCH_SUPPORTS_KEXEC
+	def_bool !SMP || HOTPLUG_CPU
 
-endmenu
+config ARCH_SUPPORTS_CRASH_DUMP
+	def_bool IA64_MCA_RECOVERY && (!SMP || HOTPLUG_CPU)
 
 menu "Power management and ACPI options"
 

-- 
2.31.1

The kexec and crash kernel options are provided in the common
kernel/Kconfig.kexec. Utilize the common options and provide
the ARCH_SUPPORTS_ and ARCH_SELECTS_ entries to recreate the
equivalent set of KEXEC and CRASH options.

Signed-off-by: Eric DeVolder <redacted>
---
 arch/mips/Kconfig | 32 +++++---------------------------
 1 file changed, 5 insertions(+), 27 deletions(-)

diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index 675a8660cb85..3d9960942cbd 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig

@@ -2873,33 +2873,11 @@ config HZ
 config SCHED_HRTICK
 	def_bool HIGH_RES_TIMERS
 
-config KEXEC
-	bool "Kexec system call"
-	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 CRASH_DUMP
-	bool "Kernel crash dumps"
-	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 firmware using
-	  PHYSICAL_START.
+config ARCH_SUPPORTS_KEXEC
+	def_bool y
+
+config ARCH_SUPPORTS_CRASH_DUMP
+	def_bool y
 
 config PHYSICAL_START
 	hex "Physical address where the kernel is loaded"

-- 
2.31.1

On Mon, Jun 19, 2023 at 10:57:56AM -0400, Eric DeVolder wrote:

The kexec and crash kernel options are provided in the common
kernel/Kconfig.kexec. Utilize the common options and provide
the ARCH_SUPPORTS_ and ARCH_SELECTS_ entries to recreate the
equivalent set of KEXEC and CRASH options.

Signed-off-by: Eric DeVolder <redacted>
---
 arch/mips/Kconfig | 32 +++++---------------------------
 1 file changed, 5 insertions(+), 27 deletions(-)

Acked-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

-- 
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea.                                                [ RFC1925, 2.3 ]

On 6/20/23 07:52, Thomas Bogendoerfer wrote:

Acked-by: Thomas Bogendoerfer<tsbogend@alpha.franken.de>

Thank you!
eric

The kexec and crash kernel options are provided in the common
kernel/Kconfig.kexec. Utilize the common options and provide
the ARCH_SUPPORTS_ and ARCH_SELECTS_ entries to recreate the
equivalent set of KEXEC and CRASH options.

Signed-off-by: Eric DeVolder <redacted>
---
 arch/loongarch/Kconfig | 26 +++++++-------------------
 1 file changed, 7 insertions(+), 19 deletions(-)

diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
index d38b066fc931..3542bf669c78 100644
--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig

@@ -481,28 +481,16 @@ config ARCH_STRICT_ALIGN
 	  to run kernel only on systems with h/w unaligned access support in
 	  order to optimise for performance.
 
-config KEXEC
-	bool "Kexec system call"
-	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.
+config ARCH_SUPPORTS_KEXEC
+	def_bool y
 
-	  The name comes from the similarity to the exec system call.
+config ARCH_SUPPORTS_CRASH_DUMP
+	def_bool y
 
-config CRASH_DUMP
-	bool "Build kdump crash kernel"
+config ARCH_SELECTS_CRASH_DUMP
+	def_bool y
+	depends on CRASH_DUMP
 	select RELOCATABLE
-	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.
-
-	  For more details see Documentation/admin-guide/kdump/kdump.rst
 
 config RELOCATABLE
 	bool "Relocatable kernel"

-- 
2.31.1

The kexec and crash kernel options are provided in the common
kernel/Kconfig.kexec. Utilize the common options and provide
the ARCH_SUPPORTS_ and ARCH_SELECTS_ entries to recreate the
equivalent set of KEXEC and CRASH options.

Signed-off-by: Eric DeVolder <redacted>
---
 arch/riscv/Kconfig | 48 ++++++++++++++--------------------------------
 1 file changed, 14 insertions(+), 34 deletions(-)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 5966ad97c30c..c484abd9bbfd 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig

@@ -585,48 +585,28 @@ config RISCV_BOOT_SPINWAIT
 
 	  If unsure what to do here, say N.
 
-config KEXEC
-	bool "Kexec system call"
-	depends on MMU
+config ARCH_SUPPORTS_KEXEC
+	def_bool MMU
+
+config ARCH_SELECTS_KEXEC
+	def_bool y
+	depends on KEXEC
 	select HOTPLUG_CPU if SMP
-	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.
+config ARCH_SUPPORTS_KEXEC_FILE
+	def_bool 64BIT && MMU && CRYPTO=y && CRYPTO_SHA256=y
 
-config KEXEC_FILE
-	bool "kexec file based systmem call"
-	depends on 64BIT && MMU
-	select HAVE_IMA_KEXEC if IMA
-	select KEXEC_CORE
+config ARCH_SELECTS_KEXEC_FILE
+	def_bool y
+	depends on KEXEC_FILE
 	select KEXEC_ELF
-	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.
-
-	  If you don't know what to do here, say Y.
+	select HAVE_IMA_KEXEC if IMA
 
 config ARCH_HAS_KEXEC_PURGATORY
 	def_bool KEXEC_FILE
-	depends on CRYPTO=y
-	depends on CRYPTO_SHA256=y
 
-config CRASH_DUMP
-	bool "Build kdump crash kernel"
-	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.
-
-	  For more details see Documentation/admin-guide/kdump/kdump.rst
+config ARCH_SUPPORTS_CRASH_DUMP
+	def_bool y
 
 config COMPAT
 	bool "Kernel support for 32-bit U-mode"

-- 
2.31.1