From: Martin Nowack <martin@se.inf.tu-dresden.de>
Date: Tue, 25 Jul 2017 22:38:41 +0200
Subject: Track errno correctly
Patch-mainline: no

Reduce the time of reading the value of errno
and using it and writing it to the state space.

Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
---
 lib/Core/Executor.cpp           | 26 +++++++++++++++++++++++++-
 lib/Core/ExternalDispatcher.cpp | 11 ++++++++++-
 lib/Core/ExternalDispatcher.h   |  2 ++
 lib/Core/Memory.h               |  3 +++
 4 files changed, 40 insertions(+), 2 deletions(-)

diff --git a/lib/Core/Executor.cpp b/lib/Core/Executor.cpp
index efc59008e542..045e353ba932 100644
--- a/lib/Core/Executor.cpp
+++ b/lib/Core/Executor.cpp
@@ -531,7 +531,10 @@ void Executor::initializeGlobals(ExecutionState &state) {
 #else
   int *errno_addr = __error();
 #endif
-  addExternalObject(state, (void *)errno_addr, sizeof *errno_addr, false);
+  MemoryObject *errnoObj =
+      addExternalObject(state, (void *)errno_addr, sizeof *errno_addr, false);
+  // Copy values from and to program space explicitly
+  errnoObj->isUserSpecified = true;
 #endif
 
   // Disabled, we don't want to promote use of live externals.
@@ -2999,6 +3002,27 @@ void Executor::callExternalFunction(ExecutionState &state,
     return;
   }
 
+#ifndef WINDOWS
+#ifndef __APPLE__
+  /* From /usr/include/errno.h: it [errno] is a per-thread variable. */
+  int *errno_addr = __errno_location();
+#else
+  int *errno_addr = __error();
+#endif
+  // Update errno value explicitly
+  ObjectPair result;
+  bool resolved = state.addressSpace.resolveOne(
+      ConstantExpr::create((uint64_t)errno_addr, Expr::Int64), result);
+  if (!resolved)
+    klee_error("Could not resolve memory object for errno");
+  int error = externalDispatcher->getLastErrno();
+  if (memcmp(result.second->concreteStore, &error, result.first->size) != 0) {
+    ObjectState *wos =
+        state.addressSpace.getWriteable(result.first, result.second);
+    memcpy(wos->concreteStore, &error, result.first->size);
+  }
+#endif
+
   Type *resultType = target->inst->getType();
   if (resultType != Type::getVoidTy(function->getContext())) {
     ref<Expr> e = ConstantExpr::fromMemory((void*) args, 
diff --git a/lib/Core/ExternalDispatcher.cpp b/lib/Core/ExternalDispatcher.cpp
index 6c54d34b82bb..28546915b539 100644
--- a/lib/Core/ExternalDispatcher.cpp
+++ b/lib/Core/ExternalDispatcher.cpp
@@ -65,6 +65,7 @@ private:
   llvm::Module *singleDispatchModule;
   std::vector<std::string> moduleIDs;
   std::string &getFreshModuleID();
+  int lastErrno;
 
 public:
   ExternalDispatcherImpl(llvm::LLVMContext &ctx);
@@ -72,6 +73,7 @@ public:
   bool executeCall(llvm::Function *function, llvm::Instruction *i,
                    uint64_t *args);
   void *resolveSymbol(const std::string &name);
+  int getLastErrno();
 };
 
 std::string &ExternalDispatcherImpl::getFreshModuleID() {
@@ -114,7 +116,8 @@ void *ExternalDispatcherImpl::resolveSymbol(const std::string &name) {
   return addr;
 }
 
-ExternalDispatcherImpl::ExternalDispatcherImpl(LLVMContext &ctx) : ctx(ctx) {
+ExternalDispatcherImpl::ExternalDispatcherImpl(LLVMContext &ctx)
+    : ctx(ctx), lastErrno(0) {
   std::string error;
   singleDispatchModule = new Module(getFreshModuleID(), ctx);
 #if LLVM_VERSION_CODE < LLVM_VERSION(3, 6)
@@ -253,6 +256,8 @@ bool ExternalDispatcherImpl::runProtectedCall(Function *f, uint64_t *args) {
     res = false;
   } else {
     executionEngine->runFunction(f, gvArgs);
+    // Explicitly acquire errno information
+    lastErrno = errno;
     res = true;
   }
 
@@ -346,6 +351,8 @@ Function *ExternalDispatcherImpl::createDispatcher(Function *target,
   return dispatcher;
 }
 
+int ExternalDispatcherImpl::getLastErrno() { return lastErrno; }
+
 ExternalDispatcher::ExternalDispatcher(llvm::LLVMContext &ctx)
     : impl(new ExternalDispatcherImpl(ctx)) {}
 
@@ -359,4 +366,6 @@ bool ExternalDispatcher::executeCall(llvm::Function *function,
 void *ExternalDispatcher::resolveSymbol(const std::string &name) {
   return impl->resolveSymbol(name);
 }
+
+int ExternalDispatcher::getLastErrno() { return impl->getLastErrno(); }
 }
diff --git a/lib/Core/ExternalDispatcher.h b/lib/Core/ExternalDispatcher.h
index c64dc7d81b93..e407355d6692 100644
--- a/lib/Core/ExternalDispatcher.h
+++ b/lib/Core/ExternalDispatcher.h
@@ -40,6 +40,8 @@ public:
   bool executeCall(llvm::Function *function, llvm::Instruction *i,
                    uint64_t *args);
   void *resolveSymbol(const std::string &name);
+
+  int getLastErrno();
 };
 }
 
diff --git a/lib/Core/Memory.h b/lib/Core/Memory.h
index 4e5c87346917..afb41390d071 100644
--- a/lib/Core/Memory.h
+++ b/lib/Core/Memory.h
@@ -153,7 +153,10 @@ private:
 
   const MemoryObject *object;
 
+public:
   uint8_t *concreteStore;
+
+private:
   // XXX cleanup name of flushMask (its backwards or something)
   BitArray *concreteMask;
 
-- 
2.15.1