Fix a Mach-O assembler segfault for a subtraction expression with an undefined symbol.

[oota-llvm.git] / lib / Target / X86 / MCTargetDesc / X86MachObjectWriter.cpp

diff --git a/lib/Target/X86/MCTargetDesc/X86MachObjectWriter.cpp b/lib/Target/X86/MCTargetDesc/X86MachObjectWriter.cpp
index b6f10ba994551dd87948a23df2180cd87fa15b49..5685a7fde141b07510486d3c2ea574803a53f225 100644 (file)
--- a/lib/Target/X86/MCTargetDesc/X86MachObjectWriter.cpp
+++ b/lib/Target/X86/MCTargetDesc/X86MachObjectWriter.cpp
@@ -63,7 +63,7 @@ public:
   void RecordRelocation(MachObjectWriter *Writer,
                         const MCAssembler &Asm, const MCAsmLayout &Layout,
                         const MCFragment *Fragment, const MCFixup &Fixup,
-                        MCValue Target, uint64_t &FixedValue) {
+                        MCValue Target, uint64_t &FixedValue) override {
     if (Writer->is64Bit())
       RecordX86_64Relocation(Writer, Asm, Layout, Fragment, Fixup, Target,
                              FixedValue);
@@ -144,11 +144,15 @@ void X86MachObjectWriter::RecordX86_64Relocation(MachObjectWriter *Writer,
     }
   } else if (Target.getSymB()) { // A - B + constant
     const MCSymbol *A = &Target.getSymA()->getSymbol();
-    MCSymbolData &A_SD = Asm.getSymbolData(*A);
+    if (A->isTemporary())
+      A = &A->AliasedSymbol();
+    const MCSymbolData &A_SD = Asm.getSymbolData(*A);
     const MCSymbolData *A_Base = Asm.getAtom(&A_SD);
 
     const MCSymbol *B = &Target.getSymB()->getSymbol();
-    MCSymbolData &B_SD = Asm.getSymbolData(*B);
+    if (B->isTemporary())
+      B = &B->AliasedSymbol();
+    const MCSymbolData &B_SD = Asm.getSymbolData(*B);
     const MCSymbolData *B_Base = Asm.getAtom(&B_SD);
 
     // Neither symbol can be modified.
@@ -175,16 +179,19 @@ void X86MachObjectWriter::RecordX86_64Relocation(MachObjectWriter *Writer,
     if (A_Base == B_Base && A_Base)
       report_fatal_error("unsupported relocation with identical base", false);
 
-    // A subtraction expression where both symbols are undefined is a
+    // A subtraction expression where either symbol is undefined is a
     // non-relocatable expression.
-    if (A->isUndefined() && B->isUndefined())
-      report_fatal_error("unsupported relocation with subtraction expression",
-                         false);
+    if (A->isUndefined() || B->isUndefined()) {
+      StringRef Name = A->isUndefined() ? A->getName() : B->getName();
+      Asm.getContext().FatalError(Fixup.getLoc(),
+        "unsupported relocation with subtraction expression, symbol '" + 
+        Name + "' can not be undefined in a subtraction expression");
+    }
 
     Value += Writer->getSymbolAddress(&A_SD, Layout) -
-      (A_Base == NULL ? 0 : Writer->getSymbolAddress(A_Base, Layout));
+      (!A_Base ? 0 : Writer->getSymbolAddress(A_Base, Layout));
     Value -= Writer->getSymbolAddress(&B_SD, Layout) -
-      (B_Base == NULL ? 0 : Writer->getSymbolAddress(B_Base, Layout));
+      (!B_Base ? 0 : Writer->getSymbolAddress(B_Base, Layout));
 
     if (A_Base) {
       Index = A_Base->getIndex();
@@ -216,7 +223,7 @@ void X86MachObjectWriter::RecordX86_64Relocation(MachObjectWriter *Writer,
     Type = MachO::X86_64_RELOC_SUBTRACTOR;
   } else {
     const MCSymbol *Symbol = &Target.getSymA()->getSymbol();
-    MCSymbolData &SD = Asm.getSymbolData(*Symbol);
+    const MCSymbolData &SD = Asm.getSymbolData(*Symbol);
     const MCSymbolData *Base = Asm.getAtom(&SD);
 
     // Relocations inside debug sections always use local relocations when
@@ -226,8 +233,8 @@ void X86MachObjectWriter::RecordX86_64Relocation(MachObjectWriter *Writer,
     if (Symbol->isInSection()) {
       const MCSectionMachO &Section = static_cast<const MCSectionMachO&>(
         Fragment->getParent()->getSection());
-      if (Section.hasAttribute(MCSectionMachO::S_ATTR_DEBUG))
-        Base = 0;
+      if (Section.hasAttribute(MachO::S_ATTR_DEBUG))
+        Base = nullptr;
     }
 
     // x86_64 almost always uses external relocations, except when there is no
@@ -358,13 +365,14 @@ bool X86MachObjectWriter::RecordScatteredRelocation(MachObjectWriter *Writer,
                                                     MCValue Target,
                                                     unsigned Log2Size,
                                                     uint64_t &FixedValue) {
+  uint64_t OriginalFixedValue = FixedValue;
   uint32_t FixupOffset = Layout.getFragmentOffset(Fragment)+Fixup.getOffset();
   unsigned IsPCRel = Writer->isFixupKindPCRel(Asm, Fixup.getKind());
   unsigned Type = MachO::GENERIC_RELOC_VANILLA;
 
   // See <reloc.h>.
   const MCSymbol *A = &Target.getSymA()->getSymbol();
-  MCSymbolData *A_SD = &Asm.getSymbolData(*A);
+  const MCSymbolData *A_SD = &Asm.getSymbolData(*A);
 
   if (!A_SD->getFragment())
     report_fatal_error("symbol '" + A->getName() +
@@ -377,7 +385,7 @@ bool X86MachObjectWriter::RecordScatteredRelocation(MachObjectWriter *Writer,
   uint32_t Value2 = 0;
 
   if (const MCSymbolRefExpr *B = Target.getSymB()) {
-    MCSymbolData *B_SD = &Asm.getSymbolData(B->getSymbol());
+    const MCSymbolData *B_SD = &Asm.getSymbolData(B->getSymbol());
 
     if (!B_SD->getFragment())
       report_fatal_error("symbol '" + B->getSymbol().getName() +
@@ -427,8 +435,10 @@ bool X86MachObjectWriter::RecordScatteredRelocation(MachObjectWriter *Writer,
     // symbol, things can go badly.
     //
     // Required for 'as' compatibility.
-    if (FixupOffset > 0xffffff)
+    if (FixupOffset > 0xffffff) {
+      FixedValue = OriginalFixedValue;
       return false;
+    }
   }
 
   MachO::any_relocation_info MRE;
@@ -458,7 +468,7 @@ void X86MachObjectWriter::RecordTLVPRelocation(MachObjectWriter *Writer,
   unsigned IsPCRel = 0;
 
   // Get the symbol data.
-  MCSymbolData *SD_A = &Asm.getSymbolData(Target.getSymA()->getSymbol());
+  const MCSymbolData *SD_A = &Asm.getSymbolData(Target.getSymA()->getSymbol());
   unsigned Index = SD_A->getIndex();
 
   // We're only going to have a second symbol in pic mode and it'll be a
@@ -469,7 +479,8 @@ void X86MachObjectWriter::RecordTLVPRelocation(MachObjectWriter *Writer,
     // If this is a subtraction then we're pcrel.
     uint32_t FixupAddress =
       Writer->getFragmentAddress(Fragment, Layout) + Fixup.getOffset();
-    MCSymbolData *SD_B = &Asm.getSymbolData(Target.getSymB()->getSymbol());
+    const MCSymbolData *SD_B =
+        &Asm.getSymbolData(Target.getSymB()->getSymbol());
     IsPCRel = 1;
     FixedValue = (FixupAddress - Writer->getSymbolAddress(SD_B, Layout) +
                   Target.getConstant());
@@ -517,7 +528,7 @@ void X86MachObjectWriter::RecordX86Relocation(MachObjectWriter *Writer,
   }
 
   // Get the symbol data, if any.
-  MCSymbolData *SD = 0;
+  const MCSymbolData *SD = nullptr;
   if (Target.getSymA())
     SD = &Asm.getSymbolData(Target.getSymA()->getSymbol());
 
@@ -564,7 +575,7 @@ void X86MachObjectWriter::RecordX86Relocation(MachObjectWriter *Writer,
       // For external relocations, make sure to offset the fixup value to
       // compensate for the addend of the symbol address, if it was
       // undefined. This occurs with weak definitions, for example.
-      if (!SD->Symbol->isUndefined())
+      if (!SD->getSymbol().isUndefined())
         FixedValue -= Layout.getSymbolOffset(SD);
     } else {
       // The index is the section ordinal (1-based).