[PATCH] [ELF][X86_64] Handle R_X86_64_PC64 relocation

[Davide Italiano]

Hi shankarke,

First of a series of relocation patches.

REPOSITORY
  rL LLVM

http://reviews.llvm.org/D7820

Files:
  lib/ReaderWriter/ELF/X86_64/X86_64RelocationHandler.cpp
  test/elf/X86_64/reloc_r_x86_64_pc64.test

Index: lib/ReaderWriter/ELF/X86_64/X86_64RelocationHandler.cpp
===================================================================
--- lib/ReaderWriter/ELF/X86_64/X86_64RelocationHandler.cpp
+++ lib/ReaderWriter/ELF/X86_64/X86_64RelocationHandler.cpp
@@ -56,6 +56,14 @@
   // TODO: Check for overflow.
 }
 
+/// \brief R_X86_64_PC64 - word64: S + A - P
+static void relocPC64(uint8_t *location, uint64_t P, uint64_t S, uint64_t A) {
+  int64_t result = (uint64_t)((S + A) - P);
+  *reinterpret_cast<llvm::support::ulittle64_t *>(location) =
+      result |
+      (uint64_t) * reinterpret_cast<llvm::support::ulittle64_t *>(location);
+}
+
 std::error_code X86_64TargetRelocationHandler::applyRelocation(
     ELFWriter &writer, llvm::FileOutputBuffer &buf, const lld::AtomLayout &atom,
     const Reference &ref) const {
@@ -112,6 +120,9 @@
     std::memcpy(location - 3, instr, sizeof(instr));
     break;
   }
+  case R_X86_64_PC64:
+    relocPC64(location, relocVAddress, targetVAddress, ref.addend());
+    break;
   case LLD_R_X86_64_GOTRELINDEX: {
     const DefinedAtom *target = cast<const DefinedAtom>(ref.target());
     for (const Reference *r : *target) {
Index: test/elf/X86_64/reloc_r_x86_64_pc64.test
===================================================================
--- test/elf/X86_64/reloc_r_x86_64_pc64.test
+++ test/elf/X86_64/reloc_r_x86_64_pc64.test
@@ -0,0 +1,61 @@
+# Tests that lld can handle relocations of type R_X86_64_PC64
+#RUN: yaml2obj -format=elf -docnum 1 %s -o %t1.o
+#RUN: lld -flavor gnu -target x86_64 %t1.o --noinhibit-exec -o %t2.out -static
+#RUN: llvm-objdump -s %t2.out | FileCheck %s
+#CHECK: Contents of section .data:
+#CHECK: 401000 0a00
+---
+FileHeader:
+  Class:           ELFCLASS64
+  Data:            ELFDATA2LSB
+  OSABI:           ELFOSABI_GNU
+  Type:            ET_REL
+  Machine:         EM_X86_64
+Sections:
+  - Name:            .text
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC, SHF_EXECINSTR ]
+    AddressAlign:    0x0000000000000004
+    Content:         ''
+  - Name:            .data
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_WRITE, SHF_ALLOC ]
+    AddressAlign:    0x0000000000000008
+    Content:         '0000'
+  - Name:            .rela.data
+    Type:            SHT_RELA
+    Link:            .symtab
+    AddressAlign:    0x0000000000000008
+    Info:            .data
+    Relocations:
+      - Offset:          0x0000000000000000
+        Symbol:          foo
+        Type:            R_X86_64_PC64
+        Addend:          8
+  - Name:            .bss
+    Type:            SHT_NOBITS
+    Flags:           [ SHF_WRITE, SHF_ALLOC ]
+    AddressAlign:    0x0000000000000004
+    Content:         ''
+Symbols:
+  Local:
+    - Name:            .text
+      Type:            STT_SECTION
+      Section:         .text
+    - Name:            .data
+      Type:            STT_SECTION
+      Section:         .data
+    - Name:            .bss
+      Type:            STT_SECTION
+      Section:         .bss
+  Global:
+    - Name:            bar
+      Type:            STT_OBJECT
+      Section:         .data
+      Size:            0x0000000000000008
+    - Name:            foo
+      Type:            STT_OBJECT
+      Section:         .data
+      Value:           0x0000000000000002
+      Size:            0x0000000000000002
+...

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