powerpc: Handle new ELFv2 module relocations

The new ELF ABI tends to use R_PPC64_REL16_LO and R_PPC64_REL16_HA
relocations (PC-relative), so implement them.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

arch/powerpc/include/uapi/asm/elf.h

@@ -295,8 +295,13 @@ do {									\
 #define R_PPC64_TLSLD		108
 #define R_PPC64_TOCSAVE		109
 
+#define R_PPC64_REL16		249
+#define R_PPC64_REL16_LO	250
+#define R_PPC64_REL16_HI	251
+#define R_PPC64_REL16_HA	252
+
 /* Keep this the last entry.  */
-#define R_PPC64_NUM		110
+#define R_PPC64_NUM		253
 
 /* There's actually a third entry here, but it's unused */
 struct ppc64_opd_entry

arch/powerpc/kernel/module_64.c

@@ -491,6 +491,23 @@ int apply_relocate_add(Elf64_Shdr *sechdrs,
 			 */
 			break;
 
+		case R_PPC64_REL16_HA:
+			/* Subtract location pointer */
+			value -= (unsigned long)location;
+			value = ((value + 0x8000) >> 16);
+			*((uint16_t *) location)
+				= (*((uint16_t *) location) & ~0xffff)
+				| (value & 0xffff);
+			break;
+
+		case R_PPC64_REL16_LO:
+			/* Subtract location pointer */
+			value -= (unsigned long)location;
+			*((uint16_t *) location)
+				= (*((uint16_t *) location) & ~0xffff)
+				| (value & 0xffff);
+			break;
+
 		default:
 			printk("%s: Unknown ADD relocation: %lu\n",
 			       me->name,