[PATCH] D47098: [ELF] Support R_X86_64_GOTPC32 and R_X86_64_GOTOFF64

[Fangrui Song via Phabricator via llvm-commits]

MaskRay created this revision.
MaskRay added reviewers: ruiu, grimar.
Herald added subscribers: llvm-commits, arichardson, emaste.
Herald added a reviewer: espindola.

The RelExpr names R_GOTONLY_PC_FROM_END R_GOTREL_FROM_END look weird,
they do not capture the semantics that these relocation types are
relative to the _GLOBAL_OFFSET_TABLE_ (which could be in the middle of
.got), we should probably fix that in the future.


Repository:
  rLLD LLVM Linker

https://reviews.llvm.org/D47098

Files:
  ELF/Arch/X86_64.cpp
  ELF/InputSection.cpp
  ELF/Relocations.cpp
  test/ELF/x86_64/relocation/shared.s


Index: test/ELF/x86_64/relocation/shared.s
===================================================================
--- /dev/null
+++ test/ELF/x86_64/relocation/shared.s
@@ -0,0 +1,18 @@
+// REQUIRES: x86
+// RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
+// RUN: ld.lld %t.o -shared -soname t -o %t.so
+// RUN: llvm-objdump -d %t.so | FileCheck %s
+
+// 0x3000 (.dynamic) - 0x2000 (.got.plt) = 4096
+// CHECK: R_X86_64_GOTOFF64:
+// CHECK-NEXT: 1000:{{.*}}movabsq $4096, %rax
+.global R_X86_64_GOTOFF64
+R_X86_64_GOTOFF64:
+  movabsq $_DYNAMIC at GOTOFF, %rax
+
+// 0x100a + 7 (instruction length) + 4079 = 0x2000 (.got.plt)
+// CHECK: R_X86_64_GOTPC32:
+// CHECK-NEXT: 100a:{{.*}}leaq 4079(%rip), %rax
+.global R_X86_64_GOTPC32
+R_X86_64_GOTPC32:
+  leaq _GLOBAL_OFFSET_TABLE_(%rip), %rax
Index: ELF/Relocations.cpp
===================================================================
--- ELF/Relocations.cpp
+++ ELF/Relocations.cpp
@@ -347,9 +347,9 @@
   if (isRelExprOneOf<R_GOT_FROM_END, R_GOT_OFF, R_MIPS_GOT_LOCAL_PAGE,
                      R_MIPS_GOTREL, R_MIPS_GOT_OFF, R_MIPS_GOT_OFF32,
                      R_MIPS_GOT_GP_PC, R_MIPS_TLSGD, R_GOT_PAGE_PC, R_GOT_PC,
-                     R_GOTONLY_PC, R_GOTONLY_PC_FROM_END, R_PLT_PC, R_TLSGD_PC,
-                     R_TLSGD, R_PPC_CALL_PLT, R_TLSDESC_CALL, R_TLSDESC_PAGE,
-                     R_HINT>(E))
+                     R_GOTONLY_PC, R_GOTONLY_PC_FROM_END, R_GOTREL_FROM_END,
+                     R_PLT_PC, R_TLSGD_PC, R_TLSGD, R_PPC_CALL_PLT,
+                     R_TLSDESC_CALL, R_TLSDESC_PAGE, R_HINT>(E))
     return true;
 
   // These never do, except if the entire file is position dependent or if
Index: ELF/InputSection.cpp
===================================================================
--- ELF/InputSection.cpp
+++ ELF/InputSection.cpp
@@ -495,11 +495,11 @@
   case R_GOTONLY_PC:
     return InX::Got->getVA() + A - P;
   case R_GOTONLY_PC_FROM_END:
-    return InX::Got->getVA() + A - P + InX::Got->getSize();
+    return InX::GotPlt->getVA() + A - P;
   case R_GOTREL:
     return Sym.getVA(A) - InX::Got->getVA();
   case R_GOTREL_FROM_END:
-    return Sym.getVA(A) - InX::Got->getVA() - InX::Got->getSize();
+    return Sym.getVA(A) - InX::GotPlt->getVA();
   case R_GOT_FROM_END:
   case R_RELAX_TLS_GD_TO_IE_END:
     return Sym.getGotOffset() + A - InX::Got->getSize();
Index: ELF/Arch/X86_64.cpp
===================================================================
--- ELF/Arch/X86_64.cpp
+++ ELF/Arch/X86_64.cpp
@@ -105,6 +105,11 @@
   case R_X86_64_REX_GOTPCRELX:
   case R_X86_64_GOTTPOFF:
     return R_GOT_PC;
+  case R_X86_64_GOTPC32:
+  case R_X86_64_GOTPC64:
+    return R_GOTONLY_PC_FROM_END;
+  case R_X86_64_GOTOFF64:
+    return R_GOTREL_FROM_END;
   case R_X86_64_NONE:
     return R_NONE;
   default:
@@ -300,6 +305,7 @@
   case R_X86_64_32S:
   case R_X86_64_TPOFF32:
   case R_X86_64_GOT32:
+  case R_X86_64_GOTPC32:
   case R_X86_64_GOTPCREL:
   case R_X86_64_GOTPCRELX:
   case R_X86_64_REX_GOTPCRELX:
@@ -319,6 +325,7 @@
   case R_X86_64_PC64:
   case R_X86_64_SIZE64:
   case R_X86_64_GOT64:
+  case R_X86_64_GOTOFF64:
     write64le(Loc, Val);
     break;
   default:


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