From dd3486ece1c0e6669e8c1f9fa5849310d613b38a Mon Sep 17 00:00:00 2001
From: Peter Collingbourne <peter@pcc.me.uk>
Date: Thu, 30 Oct 2014 13:22:57 +0000
Subject: [dfsan] New calling convention for custom functions with variadic
 arguments.

Summary:
The previous calling convention prevented custom functions from being able
to access argument labels unless it knew how many variadic arguments there
were, and of which type. This restriction made it impossible to correctly
model functions in the printf family, as it is legal to pass more arguments
than required to those functions. We now pass arguments in the following order:

non-vararg arguments
labels for non-vararg arguments
[if vararg function, pointer to array of labels for vararg arguments]
[if non-void function, pointer to label for return value]
vararg arguments

Differential Revision: http://reviews.llvm.org/D6028

llvm-svn: 220906
---
 .../Instrumentation/DataFlowSanitizer.cpp          | 31 +++++++++++++++-------
 1 file changed, 22 insertions(+), 9 deletions(-)

(limited to 'llvm/lib/Transforms/Instrumentation/DataFlowSanitizer.cpp')

diff --git a/llvm/lib/Transforms/Instrumentation/DataFlowSanitizer.cpp b/llvm/lib/Transforms/Instrumentation/DataFlowSanitizer.cpp
index cb84fd6..fa8257f 100644
--- a/llvm/lib/Transforms/Instrumentation/DataFlowSanitizer.cpp
+++ b/llvm/lib/Transforms/Instrumentation/DataFlowSanitizer.cpp
@@ -389,12 +389,6 @@ FunctionType *DataFlowSanitizer::getTrampolineFunctionType(FunctionType *T) {
 }
 
 FunctionType *DataFlowSanitizer::getCustomFunctionType(FunctionType *T) {
-  if (T->isVarArg()) {
-    // The labels are passed after all the arguments so there is no need to
-    // adjust the function type.
-    return T;
-  }
-
   llvm::SmallVector<Type *, 4> ArgTypes;
   for (FunctionType::param_iterator i = T->param_begin(), e = T->param_end();
        i != e; ++i) {
@@ -409,10 +403,12 @@ FunctionType *DataFlowSanitizer::getCustomFunctionType(FunctionType *T) {
   }
   for (unsigned i = 0, e = T->getNumParams(); i != e; ++i)
     ArgTypes.push_back(ShadowTy);
+  if (T->isVarArg())
+    ArgTypes.push_back(ShadowPtrTy);
   Type *RetType = T->getReturnType();
   if (!RetType->isVoidTy())
     ArgTypes.push_back(ShadowPtrTy);
-  return FunctionType::get(T->getReturnType(), ArgTypes, false);
+  return FunctionType::get(T->getReturnType(), ArgTypes, T->isVarArg());
 }
 
 bool DataFlowSanitizer::doInitialization(Module &M) {
@@ -1419,7 +1415,7 @@ void DFSanVisitor::visitCallSite(CallSite CS) {
         std::vector<Value *> Args;
 
         CallSite::arg_iterator i = CS.arg_begin();
-        for (unsigned n = CS.arg_size(); n != 0; ++i, --n) {
+        for (unsigned n = FT->getNumParams(); n != 0; ++i, --n) {
           Type *T = (*i)->getType();
           FunctionType *ParamFT;
           if (isa<PointerType>(T) &&
@@ -1439,9 +1435,23 @@ void DFSanVisitor::visitCallSite(CallSite CS) {
         }
 
         i = CS.arg_begin();
-        for (unsigned n = CS.arg_size(); n != 0; ++i, --n)
+        for (unsigned n = FT->getNumParams(); n != 0; ++i, --n)
           Args.push_back(DFSF.getShadow(*i));
 
+        if (FT->isVarArg()) {
+          auto LabelVAAlloca =
+              new AllocaInst(ArrayType::get(DFSF.DFS.ShadowTy,
+                                            CS.arg_size() - FT->getNumParams()),
+                             "labelva", DFSF.F->getEntryBlock().begin());
+
+          for (unsigned n = 0; i != CS.arg_end(); ++i, ++n) {
+            auto LabelVAPtr = IRB.CreateStructGEP(LabelVAAlloca, n);
+            IRB.CreateStore(DFSF.getShadow(*i), LabelVAPtr);
+          }
+
+          Args.push_back(IRB.CreateStructGEP(LabelVAAlloca, 0));
+        }
+
         if (!FT->getReturnType()->isVoidTy()) {
           if (!DFSF.LabelReturnAlloca) {
             DFSF.LabelReturnAlloca =
@@ -1451,6 +1461,9 @@ void DFSanVisitor::visitCallSite(CallSite CS) {
           Args.push_back(DFSF.LabelReturnAlloca);
         }
 
+        for (i = CS.arg_begin() + FT->getNumParams(); i != CS.arg_end(); ++i)
+          Args.push_back(*i);
+
         CallInst *CustomCI = IRB.CreateCall(CustomF, Args);
         CustomCI->setCallingConv(CI->getCallingConv());
         CustomCI->setAttributes(CI->getAttributes());
-- 
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