riscv: Support R_RISCV_ADD64 and R_RISCV_SUB64 relocs

These are needed for the __jump_table in modules using
static keys/jump-labels with the layout from
HAVE_ARCH_JUMP_LABEL_RELATIVE on 64bit kernels.
Signed-off-by: Emil Renner Berthing <kernel@esmil.dk>
Reviewed-by: Björn Töpel <bjorn.topel@gmail.com>
Tested-by: Björn Töpel <bjorn.topel@gmail.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

arch/riscv/kernel/module.c

@@ -263,6 +263,13 @@ static int apply_r_riscv_add32_rela(struct module *me, u32 *location,
 	return 0;
 }
 
+static int apply_r_riscv_add64_rela(struct module *me, u32 *location,
+				    Elf_Addr v)
+{
+	*(u64 *)location += (u64)v;
+	return 0;
+}
+
 static int apply_r_riscv_sub32_rela(struct module *me, u32 *location,
 				    Elf_Addr v)
 {
@@ -270,6 +277,13 @@ static int apply_r_riscv_sub32_rela(struct module *me, u32 *location,
 	return 0;
 }
 
+static int apply_r_riscv_sub64_rela(struct module *me, u32 *location,
+				    Elf_Addr v)
+{
+	*(u64 *)location -= (u64)v;
+	return 0;
+}
+
 static int (*reloc_handlers_rela[]) (struct module *me, u32 *location,
 				Elf_Addr v) = {
 	[R_RISCV_32]			= apply_r_riscv_32_rela,
@@ -290,7 +304,9 @@ static int (*reloc_handlers_rela[]) (struct module *me, u32 *location,
 	[R_RISCV_RELAX]			= apply_r_riscv_relax_rela,
 	[R_RISCV_ALIGN]			= apply_r_riscv_align_rela,
 	[R_RISCV_ADD32]			= apply_r_riscv_add32_rela,
+	[R_RISCV_ADD64]			= apply_r_riscv_add64_rela,
 	[R_RISCV_SUB32]			= apply_r_riscv_sub32_rela,
+	[R_RISCV_SUB64]			= apply_r_riscv_sub64_rela,
 };
 
 int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,