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

Arnd Bergmann
2023-07-05T15:06:25Z

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@oracle.com>

> +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