[PATCH v1] riscv/kexec_file: Fix relocation type R_RISCV_ADD16 and R_RISCV_SUB16 unknown

[sunying]

From: Ying Sun <sunying@xxxxxxxxxxxxxxxx>

Runs on the kernel with CONFIG_RISCV_ALTERNATIVE enabled:
  kexec -sl vmlinux

Error:
  kexec_image: Unknown rela relocation: 34
  kexec_image: Error loading purgatory ret=-8
and
  kexec_image: Unknown rela relocation: 38
  kexec_image: Error loading purgatory ret=-8

The purgatory code uses the 16-bit addition and subtraction relocation
type, but not handled, resulting in kexec_file_load failure.
So add handle to arch_kexec_apply_relocations_add().

Tested on RISC-V64 Qemu-virt, issue fixed.

Co-developed-by: Petr Tesarik <petr@xxxxxxxxxxx>
Signed-off-by: Petr Tesarik <petr@xxxxxxxxxxx>
Signed-off-by: Ying Sun <sunying@xxxxxxxxxxxxxxxx>
---
 arch/riscv/kernel/elf_kexec.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/riscv/kernel/elf_kexec.c b/arch/riscv/kernel/elf_kexec.c
index 11c0d2e0becf..3c37661801f9 100644
--- a/arch/riscv/kernel/elf_kexec.c
+++ b/arch/riscv/kernel/elf_kexec.c
@@ -451,6 +451,12 @@ int arch_kexec_apply_relocations_add(struct purgatory_info *pi,
 			*(u32 *)loc = CLEAN_IMM(CJTYPE, *(u32 *)loc) |
 				 ENCODE_CJTYPE_IMM(val - addr);
 			break;
+		case R_RISCV_ADD16:
+			*(u16 *)loc += val;
+			break;
+		case R_RISCV_SUB16:
+			*(u16 *)loc -= val;
+			break;
 		case R_RISCV_ADD32:
 			*(u32 *)loc += val;
 			break;
-- 
2.34.1