[efi] Ignore new LoongArch PC-relative relocations and relaxations

Several new relocations types have been added in LoongArch ABI version
2.10.  In particular:

- R_LARCH_B16 (18-bit PC-relative jump)
- R_LARCH_B21 (23-bit PC-relative jump)
- R_LARCH_PCREL20_S2 (22-bit PC-relative offset)

Also relocation relaxations have been introduced.  Recent GCC (13.2)
and binutils 2.41+ use these types of relocations, which confuses
elf2efi tool.  As a result, iPXE EFI images for LoongArch fail to
build with the following error:

  Unrecognised relocation type 103

Fix by ignoring R_LARCH_B{16,21} and R_LARCH_PCREL20_S2 (as with other
PC-relative relocations), and by ignoring relaxations (R_LARCH_RELAX).
Relocation relaxations are basically optimizations: ignoring them
results in a correct binary (although it might be suboptimal).

This mirrors iPXE commit ee6185d ("[efi] Ignore new LoongArch
PC-relative relocations and relaxations").

Modified-by: Michael Brown <[email protected]>
Signed-off-by: Michael Brown <[email protected]>

src/elf2efi.c

@@ -140,6 +140,12 @@
 #ifndef R_LARCH_64
 #define R_LARCH_64 2
 #endif
+#ifndef R_LARCH_B16
+#define R_LARCH_B16 64
+#endif
+#ifndef R_LARCH_B21
+#define R_LARCH_B21 65
+#endif
 #ifndef R_LARCH_B26
 #define R_LARCH_B26 66
 #endif
@@ -155,6 +161,12 @@
 #ifndef R_LARCH_GOT_PC_LO12
 #define R_LARCH_GOT_PC_LO12 76
 #endif
+#ifndef R_LARCH_RELAX
+#define R_LARCH_RELAX 100
+#endif
+#ifndef R_LARCH_PCREL20_S2
+#define R_LARCH_PCREL20_S2 103
+#endif
 #ifndef R_X86_64_GOTPCRELX
 #define R_X86_64_GOTPCRELX 41
 #endif
@@ -849,16 +861,24 @@ static void process_reloc ( struct elf_file *elf, const Elf_Shdr *shdr,
 		case ELF_MREL ( EM_AARCH64, R_AARCH64_LDST32_ABS_LO12_NC ) :
 		case ELF_MREL ( EM_AARCH64, R_AARCH64_LDST64_ABS_LO12_NC ) :
 		case ELF_MREL ( EM_AARCH64, R_AARCH64_LDST128_ABS_LO12_NC ) :
+		case ELF_MREL ( EM_LOONGARCH, R_LARCH_B16):
+		case ELF_MREL ( EM_LOONGARCH, R_LARCH_B21):
 		case ELF_MREL ( EM_LOONGARCH, R_LARCH_B26):
 		case ELF_MREL ( EM_LOONGARCH, R_LARCH_PCALA_HI20 ):
 		case ELF_MREL ( EM_LOONGARCH, R_LARCH_PCALA_LO12 ):
 		case ELF_MREL ( EM_LOONGARCH, R_LARCH_GOT_PC_HI20 ):
 		case ELF_MREL ( EM_LOONGARCH, R_LARCH_GOT_PC_LO12 ):
+		case ELF_MREL ( EM_LOONGARCH, R_LARCH_PCREL20_S2 ):
 			/* Skip PC-relative relocations; all relative
 			 * offsets remain unaltered when the object is
 			 * loaded.
 			 */
 			break;
+		case ELF_MREL ( EM_LOONGARCH, R_LARCH_RELAX ):
+			/* Relocation can be relaxed (optimized out).
+			 * Ignore it for now.
+			 */
+			break;
 		case ELF_MREL ( EM_X86_64, R_X86_64_32 ) :
 			/* Ignore 32-bit relocations in a hybrid
 			 * 32-bit BIOS and 64-bit UEFI binary,