bpf: Added linker support for R_BPF_64_NODYLD32.

This patch adds linker support to patch R_BPF_64_NODYLD32 relocations.
The implementation was based on comments and code in LLVM, as the GNU
toolchain does not uses this relocation type.

bfd/bpf-reloc.def

@@ -90,17 +90,20 @@
 
   /* R_BPF_64_NODYLD32 is not used by GNU tools - but it is generated by LLVM.
      We provide an entry here so that tools like strip can safely handle BPF
-     binaries generated by other tools.  */
+     binaries generated by other tools.
+     R_BPF_64_NODYLD32 should be fixed at linker like a R_BPF_64_ABS32.
+     The difference to ABS32 is that LLVM execution engine does not resolve
+     R_BPF_64_NODYLD32 relocations.  */
   BPF_HOWTO (R_BPF_64_NODYLD32,	/* type */
 	 0,			/* rightshift */
-	 0,			/* size */
-	 0,			/* bitsize */
+	 4,			/* size */
+	 32,			/* bitsize */
 	 false,			/* pc_relative */
 	 0,			/* bitpos */
-	 complain_overflow_dont, /* complain_on_overflow */
+	 complain_overflow_bitfield, /* complain_on_overflow */
 	 bpf_elf_generic_reloc, /* special_function */
 	 "R_BPF_64_NODYLD32",	/* name */
 	 false,			/* partial_inplace */
-	 0,			/* src_mask */
-	 0,			/* dst_mask */
-	 false)			/* pcrel_offset */
+	 0xffffffff,		/* src_mask */
+	 0xffffffff,		/* dst_mask */
+	 true)			/* pcrel_offset */

bfd/elf64-bpf.c

@@ -276,6 +276,7 @@ bpf_elf_relocate_section (bfd *output_bfd ATTRIBUTE_UNUSED,
           }
 	case R_BPF_64_ABS64:
 	case R_BPF_64_ABS32:
+	case R_BPF_64_NODYLD32:
 	  {
 	    addend = bfd_get (howto->bitsize, input_bfd, where);
 	    relocation += addend;