Add new option to create a header with foward declaration of all exte…

…rnalized functions

This commit adds a way for clang-extract to generate a header file
containing foward declarations of all externalized functions.

This can be enabled by using -DCE_OUTPUT_FUNCTION_PROTOTYPE_HEADER=<arg>.
The generated file is not self-compilable.

Signed-off-by: Giuliano Belinassi <[email protected]>

libcextract/ArgvParser.cpp

@@ -130,6 +130,9 @@ void ArgvParser::Print_Usage_Message(void)
 "  -DCE_SYMVERS_PATH=<arg>  Path to kernel Modules.symvers file.  Only used when\n"
 "                           -D__KERNEL__ is specified.\n"
 "  -DCE_DSC_OUTPUT=<arg>    Libpulp .dsc file output, used for userspace livepatching.\n"
+"  -DCE_OUTPUT_FUNCTION_PROTOTYPE_HEADER=<arg>\n"
+"                           Outputs a header file with a foward declaration of all\n"
+"                           functions. This header is not self-compilable.\n"
 "\n";
 
   llvm::outs() << "The following arguments are ignored by clang-extract:\n";
@@ -215,6 +218,11 @@ bool ArgvParser::Handle_Clang_Extract_Arg(const char *str)
 
     return true;
   }
+  if (prefix("-DCE_OUTPUT_FUNCTION_PROTOTYPE_HEADER=", str)) {
+    OutputFunctionPrototypeHeader = Extract_Single_Arg_C(str);
+
+    return true;
+  }
   if (!strcmp("-DCE_RENAME_SYMBOLS", str)) {
     RenameSymbols = true;
 

libcextract/ArgvParser.hh

@@ -114,6 +114,11 @@ class ArgvParser
     return IncExpansionPolicy;
   }
 
+  inline const char *Get_Output_Path_To_Prototype_Header(void)
+  {
+    return OutputFunctionPrototypeHeader;
+  }
+
   const char *Get_Input_File(void);
 
   /** Print help usage message.  */
@@ -143,4 +148,6 @@ class ArgvParser
   const char *DescOutputPath;
 
   const char *IncExpansionPolicy;
+
+  const char *OutputFunctionPrototypeHeader;
 };

libcextract/FunctionDepsFinder.cpp

@@ -137,6 +137,11 @@ class DeclClosureVisitor : public RecursiveASTVisitor<DeclClosureVisitor>
 
   inline void Mark_As_Analyzed(Decl *decl)
   {
+  /*
+    if (TypedefNameDecl *ndecl = dynamic_cast<TypedefNameDecl *>(decl)) {
+      llvm::outs() << ndecl->getNameAsString() << '\n';
+    }
+  */
     AnalyzedDecls.insert(decl);
   }
 
@@ -303,6 +308,9 @@ class DeclClosureVisitor : public RecursiveASTVisitor<DeclClosureVisitor>
   /* Not called automatically by Transverse.  */
   bool VisitTypedefNameDecl(TypedefNameDecl *decl)
   {
+    if (decl->getNameAsString() == "streampos") {
+      llvm::outs() << "debug me\n";
+    }
     TRY_TO(TraverseType(decl->getUnderlyingType()));
     Closure.Add_Decl_And_Prevs(decl);
 

libcextract/FunctionDepsFinder.hh

@@ -37,6 +37,12 @@ class ClosureSet
   /** Mark decl as dependencies and all its previous decls versions.  */
   bool Add_Decl_And_Prevs(Decl *decl);
 
+  /** Add a single decl to the set.  */
+  void Add_Single_Decl(Decl *decl)
+  {
+    Dependencies.insert(decl);
+  }
+
   inline std::unordered_set<Decl *> &Get_Set(void)
   {
     return Dependencies;

libcextract/HeaderGenerate.cpp

@@ -0,0 +1,74 @@
+//===- HeaderGenerate.hh - Output a header file for generated output. *- C++ -*-===//
+//
+// This project is licensed under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+/// \file
+/// Remove the body of all functions and only outputs the foward declaration.
+//
+//===----------------------------------------------------------------------===//
+
+/* Author: Giuliano Belinassi  */
+
+#include "HeaderGenerate.hh"
+#include "FunctionDepsFinder.hh"
+#include "IncludeTree.hh"
+#include "PrettyPrint.hh"
+
+HeaderGeneration::HeaderGeneration(PassManager::Context *ctx)
+  : AST(ctx->AST.get())
+{
+  Run_Analysis(ctx->NamesLog);
+}
+
+void HeaderGeneration::Print(void)
+{
+  IncludeTree IT(AST); // Not necessary, just to use the RecursivePrint class.
+  RecursivePrint(AST, Closure.Get_Set(), IT, false).Print();
+}
+
+static bool Contains(const std::vector<ExternalizerLogEntry> &v, const std::string &name)
+{
+  for (const ExternalizerLogEntry &x : v) {
+    if (x.NewName == name) {
+      return true;
+    }
+  }
+
+  return false;
+}
+
+bool HeaderGeneration::Run_Analysis(const std::vector<ExternalizerLogEntry> &set)
+{
+  ASTUnit::top_level_iterator it;
+  for (it = AST->top_level_begin(); it != AST->top_level_end(); ++it) {
+    Decl *decl = *it;
+
+    if (FunctionDecl *fdecl = dyn_cast<FunctionDecl>(decl)) {
+      if (Contains(set, fdecl->getNameAsString())) {
+        if (fdecl->hasBody()) {
+          Stmt *body = fdecl->getBody();
+          fdecl->setRangeEnd(body->getBeginLoc().getLocWithOffset(-1));
+          fdecl->setBody(nullptr);
+        }
+        Closure.Add_Single_Decl(fdecl);
+      }
+    }
+  }
+
+  /* Do not output any macros.  */
+  MacroWalker mw(AST->getPreprocessor());
+  PreprocessingRecord *rec = AST->getPreprocessor().getPreprocessingRecord();
+  for (PreprocessedEntity *entity : *rec) {
+    if (MacroDefinitionRecord *def = dyn_cast<MacroDefinitionRecord>(entity)) {
+      if (MacroInfo *info = mw.Get_Macro_Info(def)) {
+        info->setIsUsed(false);
+      }
+    }
+  }
+
+  return true;
+}

libcextract/HeaderGenerate.hh

@@ -0,0 +1,42 @@
+//===- HeaderGenerate.hh - Output a header file for generated output. *- C++ -*-===//
+//
+// This project is licensed under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+/// \file
+/// Remove the body of all functions and only outputs the foward declaration.
+//
+//===----------------------------------------------------------------------===//
+
+/* Author: Giuliano Belinassi  */
+
+#pragma once
+
+#include "Passes.hh"
+#include "FunctionDepsFinder.hh"
+#include "SymbolExternalizer.hh"
+
+
+using namespace clang;
+
+/** Outputs a header file with a foward declarations of all functions in the current
+ *  AST.
+ *
+ *  WARNING:  This class modifies the AST.
+ */
+class HeaderGeneration
+{
+  public:
+  HeaderGeneration(PassManager::Context *);
+
+  bool Run_Analysis(const std::vector<ExternalizerLogEntry> &set);
+
+  void Print(void);
+
+  protected:
+  ASTUnit *AST;
+  ClosureSet Closure;
+};

libcextract/Passes.cpp

@@ -25,6 +25,7 @@
 #include "DscFileGenerator.hh"
 #include "NonLLVMMisc.hh"
 #include "Error.hh"
+#include "HeaderGenerate.hh"
 
 #include "clang/Frontend/ASTUnit.h"
 #include "clang/Frontend/CompilerInstance.h"
@@ -513,6 +514,39 @@ class GenerateDscPass : public Pass
     }
 };
 
+class HeaderGenerationPass : public Pass
+{
+  public:
+  HeaderGenerationPass()
+  {
+    PassName = "HeaderGenerationPass";
+  }
+
+  virtual bool Gate(PassManager::Context *ctx)
+  {
+    /* Only runs if the user requested the header.  */
+    return ctx->OutputFunctionPrototypeHeader;
+  }
+
+  virtual bool Run_Pass(PassManager::Context *ctx)
+  {
+    std::error_code ec;
+    llvm::raw_fd_ostream out(ctx->OutputFunctionPrototypeHeader, ec);
+    PrettyPrint::Set_Output_Ostream(&out);
+
+    HeaderGeneration HGen(ctx);
+    HGen.Print();
+
+    PrettyPrint::Set_Output_Ostream(nullptr);
+    return true;
+  }
+
+  virtual void Dump_Result(PassManager::Context *ctx)
+  {
+    /* The dump is the generated file itself.  */
+  }
+};
+
 PassManager::PassManager()
 {
   /* Declare the pass list.  Passes will run in this order.  */
@@ -524,6 +558,7 @@ PassManager::PassManager()
     new FunctionExternalizerPass(),
     new GenerateDscPass(),
     new ClosurePass(/*PrintToFile=*/true),
+    new HeaderGenerationPass(),
   };
 }
 

libcextract/Passes.hh

@@ -59,6 +59,7 @@ class PassManager {
             IpaclonesPath(args.Get_Ipaclones_Path()),
             SymversPath(args.Get_Symvers_Path()),
             DscOutputPath(args.Get_Dsc_Output_Path()),
+            OutputFunctionPrototypeHeader(args.Get_Output_Path_To_Prototype_Header()),
             IncExpansionPolicy(IncludeExpansionPolicy::Get_Overriding(
                                args.Get_Include_Expansion_Policy(), Kernel)),
             NamesLog(),
@@ -119,6 +120,9 @@ class PassManager {
         /* Path to libpulp .dsc file for output.  */
         const char *DscOutputPath;
 
+        /* Output path to a file containing foward declarations of all functions.  */
+        const char *OutputFunctionPrototypeHeader;
+
         /* Policy used to expand includes.  */
         IncludeExpansionPolicy::Policy IncExpansionPolicy;
 

libcextract/meson.build

@@ -32,7 +32,8 @@ libcextract_sources = [
   'SymbolExternalizer.cpp',
   'SymversParser.cpp',
   'TopLevelASTIterator.cpp',
-  'ExpansionPolicy.cpp'
+  'ExpansionPolicy.cpp',
+  'HeaderGenerate.cpp'
 ]
 
 libcextract_static = static_library('cextract', libcextract_sources)