Re: [PATCH v4 03/13] arm/kexec: refactor for kernel/Kconfig.kexec

["Arnd Bergmann" <arnd@xxxxxxxx>]

On Wed, Jul 5, 2023, at 16:19, 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 <eric.devolder@xxxxxxxxxx>

> +config ARCH_SUPPORTS_KEXEC
> +	def_bool (!SMP || PM_SLEEP_SMP) && MMU
> 
>  config ATAGS_PROC
>  	bool "Export atags in procfs"
> @@ -1668,17 +1656,8 @@ 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
> 

I see this is now in linux-next, and it caused a few randconfig
build issues, these never happened in the past:

* The #ifdef CONFIG_KEXEC check in arch/arm/include/asm/kexec.h
  needs to be changed to CONFIG_KEXEC_CORE:

include/linux/kexec.h:41:2: error: #error KEXEC_SOURCE_MEMORY_LIMIT not defined

  same thing on m68k

* ARCH_SUPPORTS_CRASH_DUMP needs the same dependency as ARCH_SUPPORTS_KEXEC,
  otherwise we seem to run into an obscure assembler error building the kdump
  core on architectures that do not support kdump:

  /tmp/ccpYl6w9.s:1546: Error: selected processor does not support requested special purpose register -- `mrs r2,cpsr'

* Most architectures build machine_kexec.o only when KEXEC is enabled,
  this also needs to be changed to KEXEC_CORE:

--- a/arch/arm/kernel/Makefile
+++ b/arch/arm/kernel/Makefile
@@ -59,7 +59,7 @@ obj-$(CONFIG_FUNCTION_TRACER) += entry-ftrace.o
 obj-$(CONFIG_DYNAMIC_FTRACE)   += ftrace.o insn.o patch.o
 obj-$(CONFIG_FUNCTION_GRAPH_TRACER)    += ftrace.o insn.o patch.o
 obj-$(CONFIG_JUMP_LABEL)       += jump_label.o insn.o patch.o
-obj-$(CONFIG_KEXEC)            += machine_kexec.o relocate_kernel.o
+obj-$(CONFIG_KEXEC_CORE)       += machine_kexec.o relocate_kernel.o
 # Main staffs in KPROBES are in arch/arm/probes/ .
 obj-$(CONFIG_KPROBES)          += patch.o insn.o
 obj-$(CONFIG_OABI_COMPAT)      += sys_oabi-compat.o


   Arnd