On ELF, put PIC jump tables in a non executable section.

Fixes PR22558.

llvm-svn: 228939

2 files changed, 11 insertions, 13 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index aacc486aa14..5a01e0e9b6f 100644
--- a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -1178,23 +1178,14 @@ void AsmPrinter::EmitJumpTableInfo() {
   // the appropriate section.
   const Function *F = MF->getFunction();
   const TargetLoweringObjectFile &TLOF = getObjFileLowering();
-  bool JTInDiffSection = false;
-  if (// In PIC mode, we need to emit the jump table to the same section as the
-      // function body itself, otherwise the label differences won't make sense.
-      // FIXME: Need a better predicate for this: what about custom entries?
-      MJTI->getEntryKind() == MachineJumpTableInfo::EK_LabelDifference32 ||
-      // We should also do if the section name is NULL or function is declared
-      // in discardable section
-      // FIXME: this isn't the right predicate, should be based on the MCSection
-      // for the function.
-      F->isWeakForLinker()) {
-    OutStreamer.SwitchSection(TLOF.SectionForGlobal(F, *Mang, TM));
-  } else {
+  bool JTInDiffSection = !TLOF.shouldPutJumpTableInFunctionSection(
+      MJTI->getEntryKind() == MachineJumpTableInfo::EK_LabelDifference32,
+      *F);
+  if (JTInDiffSection) {
     // Otherwise, drop it in the readonly section.
     const MCSection *ReadOnlySection =
         TLOF.getSectionForJumpTable(*F, *Mang, TM);
     OutStreamer.SwitchSection(ReadOnlySection);
-    JTInDiffSection = true;
   }
 
   EmitAlignment(Log2_32(
diff --git a/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp b/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
index 0a49f5ff9fe..4f46e37d39c 100644
--- a/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
+++ b/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
@@ -356,6 +356,13 @@ const MCSection *TargetLoweringObjectFileELF::getSectionForJumpTable(
   return getContext().getELFSection(Name, ELF::SHT_PROGBITS, Flags, 0, Group);
 }
 
+bool TargetLoweringObjectFileELF::shouldPutJumpTableInFunctionSection(
+    bool UsesLabelDifference, const Function &F) const {
+  // We can always create relative relocations, so use another section
+  // that can be marked non-executable.
+  return false;
+}
+
 /// getSectionForConstant - Given a mergeable constant with the
 /// specified size and relocation information, return a section that it
 /// should be placed in.