[lld] r231057 - [ELF] Implement R_X86_64_PC16 relocation.

[Davide Italiano]

Author: davide
Date: Tue Mar  3 01:38:20 2015
New Revision: 231057

URL: http://llvm.org/viewvc/llvm-project?rev=231057&view=rev
Log:
[ELF] Implement R_X86_64_PC16 relocation.

Yet another chapter in the story. We're getting there, finally.
Note for the future: the tests for relocation have a lot of duplication
and probably can be unified in a single file. Let's reevaluate this once
the support will be complete (hopefully, soon).

Added:
    lld/trunk/test/elf/X86_64/reloc_r_x86_64_pc16.test
Modified:
    lld/trunk/lib/ReaderWriter/ELF/X86_64/TODO.rst
    lld/trunk/lib/ReaderWriter/ELF/X86_64/X86_64RelocationHandler.cpp
    lld/trunk/lib/ReaderWriter/ELF/X86_64/X86_64RelocationPass.cpp

Modified: lld/trunk/lib/ReaderWriter/ELF/X86_64/TODO.rst
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/lib/ReaderWriter/ELF/X86_64/TODO.rst?rev=231057&r1=231056&r2=231057&view=diff
==============================================================================
--- lld/trunk/lib/ReaderWriter/ELF/X86_64/TODO.rst (original)
+++ lld/trunk/lib/ReaderWriter/ELF/X86_64/TODO.rst Tue Mar  3 01:38:20 2015
@@ -19,7 +19,6 @@ Trivial Relocs
 These are very simple relocation calculations to implement.
 See lib/ReaderWriter/ELF/X86_64/X86_64RelocationHandler.cpp
 
-* R_X86_64_PC16
 * R_X86_64_8
 * R_X86_64_PC8
 * R_X86_64_SIZE32

Modified: lld/trunk/lib/ReaderWriter/ELF/X86_64/X86_64RelocationHandler.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/lib/ReaderWriter/ELF/X86_64/X86_64RelocationHandler.cpp?rev=231057&r1=231056&r2=231057&view=diff
==============================================================================
--- lld/trunk/lib/ReaderWriter/ELF/X86_64/X86_64RelocationHandler.cpp (original)
+++ lld/trunk/lib/ReaderWriter/ELF/X86_64/X86_64RelocationHandler.cpp Tue Mar  3 01:38:20 2015
@@ -48,6 +48,13 @@ static void reloc16(uint8_t *location, u
   // TODO: Check for overflow.
 }
 
+/// \brief R_X86_64_PC16 - word16: S + A - P
+static void relocPC16(uint8_t *location, uint64_t P, uint64_t S, int64_t A) {
+  uint16_t result = (uint16_t)((S + A) - P);
+  write16le(location, result | read16le(location));
+  // 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);
@@ -84,6 +91,9 @@ std::error_code X86_64TargetRelocationHa
   case R_X86_64_16:
     reloc16(location, relocVAddress, targetVAddress, ref.addend());
     break;
+  case R_X86_64_PC16:
+    relocPC16(location, relocVAddress, targetVAddress, ref.addend());
+    break;
   case R_X86_64_TPOFF64:
   case R_X86_64_DTPOFF32:
   case R_X86_64_TPOFF32: {

Modified: lld/trunk/lib/ReaderWriter/ELF/X86_64/X86_64RelocationPass.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/lib/ReaderWriter/ELF/X86_64/X86_64RelocationPass.cpp?rev=231057&r1=231056&r2=231057&view=diff
==============================================================================
--- lld/trunk/lib/ReaderWriter/ELF/X86_64/X86_64RelocationPass.cpp (original)
+++ lld/trunk/lib/ReaderWriter/ELF/X86_64/X86_64RelocationPass.cpp Tue Mar  3 01:38:20 2015
@@ -116,6 +116,7 @@ template <class Derived> class Relocatio
     case R_X86_64_32:
     case R_X86_64_32S:
     case R_X86_64_64:
+    case R_X86_64_PC16:
     case R_X86_64_PC32:
     case R_X86_64_PC64:
       static_cast<Derived *>(this)->handlePlain(ref);

Added: lld/trunk/test/elf/X86_64/reloc_r_x86_64_pc16.test
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/elf/X86_64/reloc_r_x86_64_pc16.test?rev=231057&view=auto
==============================================================================
--- lld/trunk/test/elf/X86_64/reloc_r_x86_64_pc16.test (added)
+++ lld/trunk/test/elf/X86_64/reloc_r_x86_64_pc16.test Tue Mar  3 01:38:20 2015
@@ -0,0 +1,61 @@
+# Tests that lld can handle relocations of type R_X86_64_PC16
+#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 0700
+---
+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_PC16
+        Addend:          5
+  - 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
+...