Handle R_X86_64_GOTOFF64.

[ruiu]

Summary

R_X86_64_GOTOFF64 is a relocation type to set to a distance betwween
a symbol and the beginning of the .got section. Previously, we always
created a dynamic relocation for the relocation type even though it
can be resolved at link-time.

Creating a dynamic relocation for R_X86_64_GOTOFF64 caused link failure
for some programs that do have a relocation of the type in a .text
section, as text relocations are prohibited in most configurations.

[MaskRay]

..This is what I removed from https://reviews.llvm.org/D47098 (which is still blocked by https://reviews.llvm.org/D47507) because of reviewer's suggestion. Anyway LG.

[ruiu]

It is not me who requested you remove GOTOFF64 relocation support from your patch, but if you have a patch with a title "Add R_X86_64_GOTPC{32,64} support", I wouldn't be surprised if you are requested to remove code to support other types of relocations, as patches shouldn't contain unrelated changes. A best practice is to separate a patch to two or more.

lld/trunk/ELF/Arch/X86_64.cpp

RelExpr X86_64<ELFT>::getRelExpr(RelType Type, const Symbol &S,
   case R_X86_64_GOT32:
   case R_X86_64_GOT64:
     return R_GOT_FROM_END;
   case R_X86_64_GOTPCREL:
   case R_X86_64_GOTPCRELX:
   case R_X86_64_REX_GOTPCRELX:
   case R_X86_64_GOTTPOFF:
     return R_GOT_PC;
+  case R_X86_64_GOTOFF64:
+    return R_GOTREL;
   case R_X86_64_GOTPC32:
   case R_X86_64_GOTPC64:
     return R_GOTONLY_PC_FROM_END;
   case R_X86_64_NONE:
     return R_NONE;
   default:
     return R_INVALID;
   }
case R_X86_64_SIZE32:
     write32le(Loc, Val);
     break;
   case R_X86_64_64:
   case R_X86_64_DTPOFF64:
   case R_X86_64_GLOB_DAT:
   case R_X86_64_PC64:
   case R_X86_64_SIZE64:
   case R_X86_64_GOT64:
+  case R_X86_64_GOTOFF64:
   case R_X86_64_GOTPC64:
     write64le(Loc, Val);
     break;
   default:
     error(getErrorLocation(Loc) + "unrecognized reloc " + Twine(Type));
   }
 }
 

lld/trunk/test/ELF/x86-64-reloc-gotoff64.s

+// REQUIRES: x86
+
+// RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
+// RUN: ld.lld -shared -o %t.so %t.o
+// RUN: llvm-readelf -sections %t.so | FileCheck %s
+// RUN: llvm-objdump -d %t.so | FileCheck -check-prefix=DISASM %s
+
+// CHECK: .dynamic DYNAMIC  0000000000002000 002000
+// CHECK: .got     PROGBITS 0000000000002070 002070
+
+// DISASM: 1000: 48 ba 90 ff ff ff ff ff ff ff   movabsq $-112, %rdx
+
+.global _start
+.weak _DYNAMIC
+.hidden _DYNAMIC
+_start:
+  movabsq $_DYNAMIC@GOTOFF, %rdx