From cee7dd28c43bf0c8941b4f6e63be2a36e288e992 Mon Sep 17 00:00:00 2001
From: Lang Hames <lhames@gmail.com>
Date: Thu, 19 May 2016 23:26:05 +0000
Subject: [PATCH] [RuntimeDyld][MachO] Add support for SUBTRACTOR relocations
 between anonymous symbols on x86-64.

llvm-svn: 270157
---
 .../Targets/RuntimeDyldMachOX86_64.h          | 67 ++++++++++++++-----
 .../X86/MachO_x86-64_PIC_relocations.s        | 30 ++++++++-
 2 files changed, 79 insertions(+), 18 deletions(-)

diff --git a/lib/ExecutionEngine/RuntimeDyld/Targets/RuntimeDyldMachOX86_64.h b/lib/ExecutionEngine/RuntimeDyld/Targets/RuntimeDyldMachOX86_64.h
index 0f1407dd8de..bc482298324 100644
--- a/lib/ExecutionEngine/RuntimeDyld/Targets/RuntimeDyldMachOX86_64.h
+++ b/lib/ExecutionEngine/RuntimeDyld/Targets/RuntimeDyldMachOX86_64.h
@@ -157,10 +157,10 @@ private:
 
   Expected<relocation_iterator>
   processSubtractRelocation(unsigned SectionID, relocation_iterator RelI,
-                            const ObjectFile &BaseObjT,
+                            const MachOObjectFile &BaseObj,
                             ObjSectionToIDMap &ObjSectionToID) {
     const MachOObjectFile &Obj =
-        static_cast<const MachOObjectFile&>(BaseObjT);
+        static_cast<const MachOObjectFile&>(BaseObj);
     MachO::any_relocation_info RE =
         Obj.getRelocation(RelI->getRawDataRefImpl());
 
@@ -168,23 +168,60 @@ private:
     uint64_t Offset = RelI->getOffset();
     uint8_t *LocalAddress = Sections[SectionID].getAddressWithOffset(Offset);
     unsigned NumBytes = 1 << Size;
-
-    Expected<StringRef> SubtrahendNameOrErr = RelI->getSymbol()->getName();
-    if (!SubtrahendNameOrErr)
-      return SubtrahendNameOrErr.takeError();
-    auto SubtrahendI = GlobalSymbolTable.find(*SubtrahendNameOrErr);
-    unsigned SectionBID = SubtrahendI->second.getSectionID();
-    uint64_t SectionBOffset = SubtrahendI->second.getOffset();
     int64_t Addend =
       SignExtend64(readBytesUnaligned(LocalAddress, NumBytes), NumBytes * 8);
 
+    unsigned SectionBID = ~0U;
+    uint64_t SectionBOffset = 0;
+
+    MachO::any_relocation_info RelInfo =
+      Obj.getRelocation(RelI->getRawDataRefImpl());
+
+    bool AIsExternal = BaseObj.getPlainRelocationExternal(RelInfo);
+
+    if (AIsExternal) {
+      Expected<StringRef> SubtrahendNameOrErr = RelI->getSymbol()->getName();
+      if (!SubtrahendNameOrErr)
+        return SubtrahendNameOrErr.takeError();
+      auto SubtrahendI = GlobalSymbolTable.find(*SubtrahendNameOrErr);
+      SectionBID = SubtrahendI->second.getSectionID();
+      SectionBOffset = SubtrahendI->second.getOffset();
+    } else {
+      SectionRef SecB = Obj.getAnyRelocationSection(RelInfo);
+      bool IsCode = SecB.isText();
+      Expected<unsigned> SectionBIDOrErr =
+        findOrEmitSection(Obj, SecB, IsCode, ObjSectionToID);
+      if (!SectionBIDOrErr)
+        return SectionBIDOrErr.takeError();
+      SectionBID = *SectionBIDOrErr;
+      Addend += SecB.getAddress();
+    }
+
     ++RelI;
-    Expected<StringRef> MinuendNameOrErr = RelI->getSymbol()->getName();
-    if (!MinuendNameOrErr)
-      return MinuendNameOrErr.takeError();
-    auto MinuendI = GlobalSymbolTable.find(*MinuendNameOrErr);
-    unsigned SectionAID = MinuendI->second.getSectionID();
-    uint64_t SectionAOffset = MinuendI->second.getOffset();
+
+    unsigned SectionAID = ~0U;
+    uint64_t SectionAOffset = 0;
+
+    RelInfo = Obj.getRelocation(RelI->getRawDataRefImpl());
+
+    bool BIsExternal = BaseObj.getPlainRelocationExternal(RelInfo);
+    if (BIsExternal) {
+      Expected<StringRef> MinuendNameOrErr = RelI->getSymbol()->getName();
+      if (!MinuendNameOrErr)
+        return MinuendNameOrErr.takeError();
+      auto MinuendI = GlobalSymbolTable.find(*MinuendNameOrErr);
+      SectionAID = MinuendI->second.getSectionID();
+      SectionAOffset = MinuendI->second.getOffset();
+    } else {
+      SectionRef SecA = Obj.getAnyRelocationSection(RelInfo);
+      bool IsCode = SecA.isText();
+      Expected<unsigned> SectionAIDOrErr =
+        findOrEmitSection(Obj, SecA, IsCode, ObjSectionToID);
+      if (!SectionAIDOrErr)
+        return SectionAIDOrErr.takeError();
+      SectionAID = *SectionAIDOrErr;
+      Addend -= SecA.getAddress();
+    }
 
     RelocationEntry R(SectionID, Offset, MachO::X86_64_RELOC_SUBTRACTOR, (uint64_t)Addend,
                       SectionAID, SectionAOffset, SectionBID, SectionBOffset,
diff --git a/test/ExecutionEngine/RuntimeDyld/X86/MachO_x86-64_PIC_relocations.s b/test/ExecutionEngine/RuntimeDyld/X86/MachO_x86-64_PIC_relocations.s
index 8a50ede9027..f050c3d846c 100644
--- a/test/ExecutionEngine/RuntimeDyld/X86/MachO_x86-64_PIC_relocations.s
+++ b/test/ExecutionEngine/RuntimeDyld/X86/MachO_x86-64_PIC_relocations.s
@@ -62,11 +62,26 @@ z2:
         .globl  abssym
 abssym = 0xdeadbeef
 
-	# Test subtractor relocations.
-# rtdyld-check: *{8}z3 = z4 - z5 + 4
-z3:
+# Test subtractor relocations between named symbols.
+# rtdyld-check: *{8}z3a = z4 - z5 + 4
+z3a:
         .quad  z4 - z5 + 4
 
+# Test subtractor relocations between anonymous symbols.
+# rtdyld-check: *{8}z3b = (section_addr(test_x86-64.o, _tmp3) + 4) - (section_addr(test_x86-64.o, _tmp4)) + 8
+z3b:
+        .quad  Lanondiff_1 - Lanondiff_2 + 8
+
+# Test subtractor relocations between named and anonymous symbols.
+# rtdyld-check: *{8}z3c = z4 - (section_addr(test_x86-64.o, _tmp4)) + 12
+z3c:
+        .quad  z4 - Lanondiff_2 + 12
+
+# Test subtractor relocations between anonymous and named symbols.
+# rtdyld-check: *{8}z3d = (section_addr(test_x86-64.o, _tmp3) + 4) - z4 + 16
+z3d:
+        .quad  Lanondiff_1 - z4 + 16
+
         .section        __DATA,_tmp1
 z4:
         .byte 1
@@ -75,4 +90,13 @@ z4:
 z5:
         .byte 1
 
+        .section        __DATA,_tmp3
+        .long 1         # padding to make sure we handle non-zero offsets.
+Lanondiff_1:
+        .byte 1
+
+        .section        __DATA,_tmp4
+Lanondiff_2:
+        .byte 1
+
 .subsections_via_symbols