From 4501dad2c08ffeef7e7de6b27d1c2d59c0077a5f Mon Sep 17 00:00:00 2001
From: Alessandro Di Federico <ale@clearmind.me>
Date: Wed, 11 Jan 2017 15:25:53 +0100
Subject: [PATCH] Introduce the `--no-link` option

Introduce an option to prevent `revamb` from linking in all the QEMU
helpers. This is useful if the output doesn't need to be compiled, but
just analyzed.
---
 codegenerator.cpp   | 17 ++++++++++-------
 codegenerator.h     |  6 +++++-
 main.cpp            |  8 ++++++--
 variablemanager.cpp |  7 ++++++-
 4 files changed, 27 insertions(+), 11 deletions(-)

diff --git a/codegenerator.cpp b/codegenerator.cpp
index aad5d09ad..e2d5b9dd9 100644
--- a/codegenerator.cpp
+++ b/codegenerator.cpp
@@ -73,7 +73,8 @@ CodeGenerator::CodeGenerator(BinaryFile &Binary,
                              std::string BBSummary,
                              bool EnableOSRA,
                              bool EnableTracing,
-                             bool DetectFunctionBoundaries) :
+                             bool DetectFunctionBoundaries,
+                             bool EnableLinking) :
   TargetArchitecture(Target),
   Context(getGlobalContext()),
   TheModule((new Module("top", Context))),
@@ -82,7 +83,8 @@ CodeGenerator::CodeGenerator(BinaryFile &Binary,
   Binary(Binary),
   EnableOSRA(EnableOSRA),
   EnableTracing(EnableTracing),
-  DetectFunctionBoundaries(DetectFunctionBoundaries)
+  DetectFunctionBoundaries(DetectFunctionBoundaries),
+  EnableLinking(EnableLinking)
 {
   OriginalInstrMDKind = Context.getMDKindID("oi");
   PTCInstrMDKind = Context.getMDKindID("pi");
@@ -875,11 +877,12 @@ void CodeGenerator::translate(uint64_t VirtualAddress,
         GV.setLinkage(GlobalValue::InternalLinkage);
   }
 
-  Linker TheLinker(*TheModule);
-  bool Result = TheLinker.linkInModule(std::move(HelpersModule),
-                                       Linker::LinkOnlyNeeded);
-  assert(!Result && "Linking failed");
-  (void) Result;
+  if (EnableLinking) {
+    Linker TheLinker(*TheModule);
+    bool Result = TheLinker.linkInModule(std::move(HelpersModule),
+                                         Linker::LinkOnlyNeeded);
+    assert(!Result && "Linking failed");
+  }
 
   Variables.setDataLayout(&TheModule->getDataLayout());
 
diff --git a/codegenerator.h b/codegenerator.h
index 0353cb6ad..6d932580d 100644
--- a/codegenerator.h
+++ b/codegenerator.h
@@ -63,6 +63,8 @@ public:
   /// \param EnableTracing specify whether tracing in the ouptut binary should
   ///        be enabled, that is, whether calls to an external `newPC` function
   ///        should be removed at the end of the translation or not.
+  /// \param EnableLinking specifying whether linking to QEMU helpers should be
+  ///        performed or not.
   CodeGenerator(BinaryFile &Binary,
                 Architecture &Target,
                 std::string Output,
@@ -74,7 +76,8 @@ public:
                 std::string BBSummary,
                 bool EnableOSRA,
                 bool EnableTracing,
-                bool DetectFunctionBoundaries);
+                bool DetectFunctionBoundaries,
+                bool EnableLinking);
 
   ~CodeGenerator();
 
@@ -123,6 +126,7 @@ private:
   std::string BBSummaryPath;
   std::string FunctionListPath;
   bool DetectFunctionBoundaries;
+  bool EnableLinking;
 };
 
 #endif // _CODEGENERATOR_H
diff --git a/main.cpp b/main.cpp
index 4f813e115..0f739f89d 100644
--- a/main.cpp
+++ b/main.cpp
@@ -52,6 +52,7 @@ struct ProgramParameters {
   bool EnableTracing;
   bool UseSections;
   bool DetectFunctionsBoundaries;
+  bool NoLink;
 };
 
 using LibraryDestructor = GenericFunctor<decltype(&dlclose), &dlclose>;
@@ -178,7 +179,9 @@ static int parseArgs(int Argc, const char *Argv[],
                &DebugLoggingString,
                "enable verbose logging."),
     OPT_BOOLEAN('O', "no-osra", &Parameters->NoOSRA,
-                "disable OSRA"),
+                "disable OSRA."),
+    OPT_BOOLEAN('L', "no-link", &Parameters->NoLink,
+                "do not link the output to QEMU helpers."),
     OPT_BOOLEAN('t', "tracing", &Parameters->EnableTracing,
                 "enable PC tracing in the output binary (through newPC)"),
     OPT_BOOLEAN('S', "use-sections", &Parameters->UseSections,
@@ -287,7 +290,8 @@ int main(int argc, const char *argv[]) {
                           std::string(Parameters.BBSummaryPath),
                           !Parameters.NoOSRA,
                           Parameters.EnableTracing,
-                          Parameters.DetectFunctionsBoundaries);
+                          Parameters.DetectFunctionsBoundaries,
+                          !Parameters.NoLink);
 
   Generator.translate(Parameters.EntryPointAddress, "root");
 
diff --git a/variablemanager.cpp b/variablemanager.cpp
index f25305351..e01d49733 100644
--- a/variablemanager.cpp
+++ b/variablemanager.cpp
@@ -296,7 +296,12 @@ bool CorrectCPUStateUsagePass::runOnModule(Module& TheModule) {
             continue;
           }
 
-          assert(!Callee->empty() && "external functions are not supported");
+          assert((Callee->getName().startswith("helper")
+                  || !Callee->empty())
+                 && "external functions are not supported");
+
+          if (Callee->empty())
+            break;
 
           // TODO: move all the specialization-handling code outside
           // Is the callee already a specialization?