Add Forward Control-Flow Integrity.

This commit adds a new pass that can inject checks before indirect calls to
make sure that these calls target known locations. It supports three types of
checks and, at compile time, it can take the name of a custom function to call
when an indirect call check fails. The default failure function ignores the
error and continues.

This pass incidentally moves the function JumpInstrTables::transformType from
private to public and makes it static (with a new argument that specifies the
table type to use); this is so that the CFI code can transform function types
at call sites to determine which jump-instruction table to use for the check at
that site.

Also, this removes support for jumptables in ARM, pending further performance
analysis and discussion.

Review: http://reviews.llvm.org/D4167
llvm-svn: 221708

1 files changed, 6 insertions, 6 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index 61f1d1b653e..087836901a7 100644
--- a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -879,16 +879,17 @@ bool AsmPrinter::doFinalization(Module &M) {
     bool IsThumb = (Arch == Triple::thumb || Arch == Triple::thumbeb);
     MCInst TrapInst;
     TM.getSubtargetImpl()->getInstrInfo()->getTrap(TrapInst);
+    unsigned LogAlignment = llvm::Log2_64(JITI->entryByteAlignment());
+
+    // Emit the right section for these functions.
+    OutStreamer.SwitchSection(OutContext.getObjectFileInfo()->getTextSection());
     for (const auto &KV : JITI->getTables()) {
       uint64_t Count = 0;
       for (const auto &FunPair : KV.second) {
         // Emit the function labels to make this be a function entry point.
         MCSymbol *FunSym =
           OutContext.GetOrCreateSymbol(FunPair.second->getName());
-        OutStreamer.EmitSymbolAttribute(FunSym, MCSA_Global);
-        // FIXME: JumpTableInstrInfo should store information about the required
-        // alignment of table entries and the size of the padding instruction.
-        EmitAlignment(3);
+        EmitAlignment(LogAlignment);
         if (IsThumb)
           OutStreamer.EmitThumbFunc(FunSym);
         if (MAI->hasDotTypeDotSizeDirective())
@@ -910,10 +911,9 @@ bool AsmPrinter::doFinalization(Module &M) {
       }
 
       // Emit enough padding instructions to fill up to the next power of two.
-      // This assumes that the trap instruction takes 8 bytes or fewer.
       uint64_t Remaining = NextPowerOf2(Count) - Count;
       for (uint64_t C = 0; C < Remaining; ++C) {
-        EmitAlignment(3);
+        EmitAlignment(LogAlignment);
         OutStreamer.EmitInstruction(TrapInst, getSubtargetInfo());
       }