This fixes below linking errors when building with CONFIG_KEXEC_FILE=y &&
CONFIG_KEXEC=n. The {kexec_relocate,crash_save_regs,machine_kexec}.c should
be core kexec source files.

riscv64-linux-gnu-ld: kernel/kexec_core.o: in function `kimage_free':
/home/changbin/work/linux-riscv/kernel/kexec_core.c:651: undefined reference to `machine_kexec_cleanup'
riscv64-linux-gnu-ld: kernel/kexec_core.o: in function `__crash_kexec':
/home/changbin/work/linux-riscv/kernel/kexec_core.c:981: undefined reference to `machine_crash_shutdown'
riscv64-linux-gnu-ld: /home/changbin/work/linux-riscv/kernel/kexec_core.c:982: undefined reference to `machine_kexec'
riscv64-linux-gnu-ld: kernel/kexec_core.o: in function `crash_setup_regs':
/home/changbin/work/linux-riscv/./arch/riscv/include/asm/kexec.h:35: undefined reference to `riscv_crash_save_regs'
riscv64-linux-gnu-ld: kernel/kexec_core.o: in function `kernel_kexec':
/home/changbin/work/linux-riscv/kernel/kexec_core.c:1200: undefined reference to `machine_shutdown'
riscv64-linux-gnu-ld: /home/changbin/work/linux-riscv/kernel/kexec_core.c:1204: undefined reference to `machine_kexec'
riscv64-linux-gnu-ld: kernel/kexec_file.o: in function `__do_sys_kexec_file_load':
/home/changbin/work/linux-riscv/kernel/kexec_file.c:363: undefined reference to `machine_kexec_prepare'
riscv64-linux-gnu-ld: /home/changbin/work/linux-riscv/kernel/kexec_file.c:363: undefined reference to `machine_kexec_prepare'
make: *** [Makefile:1160: vmlinux] Error 1

Signed-off-by: Changbin Du <changbin.du@huawei.com>
---
 arch/riscv/kernel/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile
index c71d6591d539..33bb60a354cd 100644
--- a/arch/riscv/kernel/Makefile
+++ b/arch/riscv/kernel/Makefile
@@ -78,7 +78,7 @@ obj-$(CONFIG_SMP) += cpu_ops_sbi.o
 endif
 obj-$(CONFIG_HOTPLUG_CPU)	+= cpu-hotplug.o
 obj-$(CONFIG_KGDB)		+= kgdb.o
-obj-$(CONFIG_KEXEC)		+= kexec_relocate.o crash_save_regs.o machine_kexec.o
+obj-$(CONFIG_KEXEC_CORE)	+= kexec_relocate.o crash_save_regs.o machine_kexec.o
 obj-$(CONFIG_KEXEC_FILE)	+= elf_kexec.o machine_kexec_file.o
 obj-$(CONFIG_CRASH_DUMP)	+= crash_dump.o
 
-- 
2.26.2


-- 
Cheers,
Changbin Du

Thanks, but it has a solution already. See 
https://lore.kernel.org/all/20220601070204.26882-1-lizhengyu3@huawei.com/ .

On Mon, 06 Jun 2022 11:56:35 +0800, Changbin Du <changbin.du@huawei.com> 
wrote:
> This fixes below linking errors when building with CONFIG_KEXEC_FILE=y &&
> CONFIG_KEXEC=n. The {kexec_relocate,crash_save_regs,machine_kexec}.c should
> be core kexec source files.
>
> riscv64-linux-gnu-ld: kernel/kexec_core.o: in function `kimage_free':
> /home/changbin/work/linux-riscv/kernel/kexec_core.c:651: undefined reference to `machine_kexec_cleanup'
> riscv64-linux-gnu-ld: kernel/kexec_core.o: in function `__crash_kexec':
> /home/changbin/work/linux-riscv/kernel/kexec_core.c:981: undefined reference to `machine_crash_shutdown'
> riscv64-linux-gnu-ld: /home/changbin/work/linux-riscv/kernel/kexec_core.c:982: undefined reference to `machine_kexec'
> riscv64-linux-gnu-ld: kernel/kexec_core.o: in function `crash_setup_regs':
> /home/changbin/work/linux-riscv/./arch/riscv/include/asm/kexec.h:35: undefined reference to `riscv_crash_save_regs'
> riscv64-linux-gnu-ld: kernel/kexec_core.o: in function `kernel_kexec':
> /home/changbin/work/linux-riscv/kernel/kexec_core.c:1200: undefined reference to `machine_shutdown'
> riscv64-linux-gnu-ld: /home/changbin/work/linux-riscv/kernel/kexec_core.c:1204: undefined reference to `machine_kexec'
> riscv64-linux-gnu-ld: kernel/kexec_file.o: in function `__do_sys_kexec_file_load':
> /home/changbin/work/linux-riscv/kernel/kexec_file.c:363: undefined reference to `machine_kexec_prepare'
> riscv64-linux-gnu-ld: /home/changbin/work/linux-riscv/kernel/kexec_file.c:363: undefined reference to `machine_kexec_prepare'
> make: *** [Makefile:1160: vmlinux] Error 1
>
> Signed-off-by: Changbin Du <changbin.du@huawei.com>
> ---
>   arch/riscv/kernel/Makefile | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile
> index c71d6591d539..33bb60a354cd 100644
> --- a/arch/riscv/kernel/Makefile
> +++ b/arch/riscv/kernel/Makefile
> @@ -78,7 +78,7 @@ obj-$(CONFIG_SMP) += cpu_ops_sbi.o
>   endif
>   obj-$(CONFIG_HOTPLUG_CPU)	+= cpu-hotplug.o
>   obj-$(CONFIG_KGDB)		+= kgdb.o
> -obj-$(CONFIG_KEXEC)		+= kexec_relocate.o crash_save_regs.o machine_kexec.o
> +obj-$(CONFIG_KEXEC_CORE)	+= kexec_relocate.o crash_save_regs.o machine_kexec.o
>   obj-$(CONFIG_KEXEC_FILE)	+= elf_kexec.o machine_kexec_file.o
>   obj-$(CONFIG_CRASH_DUMP)	+= crash_dump.o
>