Check for unstable types in IPC messages.

tools/clang/plugins/CheckIPCVisitor.cpp

Index: tools/clang/plugins/CheckIPCVisitor.cpp
diff --git a/tools/clang/plugins/CheckIPCVisitor.cpp b/tools/clang/plugins/CheckIPCVisitor.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..b123b0130ed1c5dd3d5690476a149a84187271ab
--- /dev/null
+++ b/tools/clang/plugins/CheckIPCVisitor.cpp
@@ -0,0 +1,288 @@
+// Copyright (c) 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "CheckIPCVisitor.h"
+
+using namespace clang;
+
+namespace chrome_checker {
+
+namespace {
+
+const char kWriteParamBadType[] =
+    "[chromium-ipc] IPC::WriteParam() is called on blacklisted type '%0'%1.";
+
+const char kTupleBadType[] =
+    "[chromium-ipc] IPC tuple references banned type '%0'%1.";
+
+const char kWriteParamBadSignature[] =
+    "[chromium-ipc] IPC::WriteParam() is expected to have two arguments.";
+
+const char kNoteSeeHere[] =
+    "see here";
+
+}  // namespace
+
+CheckIPCVisitor::CheckIPCVisitor(CompilerInstance& compiler)
+  : compiler_(compiler), context_(nullptr) {
+  auto& diagnostics = compiler_.getDiagnostics();
+  error_write_param_bad_type_ = diagnostics.getCustomDiagID(
+      DiagnosticsEngine::Error, kWriteParamBadType);
+  error_tuple_bad_type_ = diagnostics.getCustomDiagID(
+      DiagnosticsEngine::Error, kTupleBadType);
+  error_write_param_bad_signature_ = diagnostics.getCustomDiagID(
+      DiagnosticsEngine::Error, kWriteParamBadSignature);
+  note_see_here_ = diagnostics.getCustomDiagID(
+      DiagnosticsEngine::Note, kNoteSeeHere);
+
+  blacklisted_typedefs_ = llvm::StringSet<>({
+      "intmax_t",
+      "uintmax_t",
+      "intptr_t",
+      "uintptr_t",
+      "wint_t",
+      "size_t",
+      "rsize_t",
+      "ssize_t",
+      "ptrdiff_t",
+      "dev_t",
+      "off_t",
+      "clock_t",
+      "time_t",
+      "suseconds_t"
+  });
+}
+
+void CheckIPCVisitor::BeginDecl(Decl* decl) {
+  decl_stack_.push_back(decl);
+}
+
+void CheckIPCVisitor::EndDecl() {
+  decl_stack_.pop_back();
+}
+
+void CheckIPCVisitor::VisitTemplateSpecializationType(
+    TemplateSpecializationType* spec) {
+  ValidateCheckedTuple(spec);
+}
+
+void CheckIPCVisitor::VisitCallExpr(CallExpr* call_expr) {
+  ValidateWriteParam(call_expr);
+}
+
+bool CheckIPCVisitor::ValidateWriteParam(const CallExpr* call_expr) {
+  const FunctionDecl* callee_decl = call_expr->getDirectCallee();
+  if (!callee_decl ||
+      callee_decl->getQualifiedNameAsString() != "IPC::WriteParam") {
+    return true;
+  }
+
+  return ValidateWriteParamSignature(call_expr) &&
+      ValidateWriteParamArgument(call_expr->getArg(1));
+}
+
+// Checks that IPC::WriteParam() has expected signature.
+bool CheckIPCVisitor::ValidateWriteParamSignature(
+    const CallExpr* call_expr) {
+  if (call_expr->getNumArgs() != 2) {
+    compiler_.getDiagnostics().Report(
+        call_expr->getExprLoc(), error_write_param_bad_signature_);
+    return false;
+  }
+  return true;
+}
+
+// Checks that IPC::WriteParam() argument type is allowed.
+// See CheckType() for specifics.
+bool CheckIPCVisitor::ValidateWriteParamArgument(const Expr* arg_expr) {
+  if (auto* parent_fn_decl = GetParentDecl<FunctionDecl>()) {
+    auto template_kind = parent_fn_decl->getTemplatedKind();
+    if (template_kind != FunctionDecl::TK_NonTemplate &&
+        template_kind != FunctionDecl::TK_FunctionTemplate) {
+      // Skip all specializations - we don't check WriteParam() on dependent
+      // types (typedef info gets lost), and we checked all non-dependent uses
+      // earlier (when we checked the template itself).
+      return true;
+    }
+  }
+
+  QualType arg_type;
+
+  arg_expr = arg_expr->IgnoreImplicit();
+  if (auto* cast_expr = dyn_cast<ExplicitCastExpr>(arg_expr)) {
+    arg_type = cast_expr->getTypeAsWritten();
+  } else {
+    arg_type = arg_expr->getType();
+  }
+
+  CheckDetails details;
+  if (CheckType(arg_type, &details)) {
+    return true;
+  }
+
+  ReportCheckError(details,
+                   arg_expr->getExprLoc(),
+                   error_write_param_bad_type_);
+
+  return false;
+}
+
+// Checks that IPC::CheckedTuple<> is specialized with allowed types.
+// See CheckType() above for specifics.
+bool CheckIPCVisitor::ValidateCheckedTuple(
+    const TemplateSpecializationType* spec) {
+  TemplateDecl* decl = spec->getTemplateName().getAsTemplateDecl();
+  if (!decl || decl->getQualifiedNameAsString() != "IPC::CheckedTuple") {
+    return true;
+  }
+
+  bool valid = true;
+  for (unsigned i = 0; i != spec->getNumArgs(); ++i) {
+    const TemplateArgument& arg = spec->getArg(i);
+    CheckDetails details;
+    if (CheckTemplateArgument(arg, &details)) {
+      continue;
+    }
+
+    valid = false;
+
+    auto* parent_decl = GetParentDecl<Decl>();
+    ReportCheckError(
+        details,
+        parent_decl ? parent_decl->getLocStart() : SourceLocation(),
+        error_tuple_bad_type_);
+  }
+
+  return valid;
+}
+
+template <typename T>
+const T* CheckIPCVisitor::GetParentDecl() const {
+  for (auto i = decl_stack_.rbegin(); i != decl_stack_.rend(); ++i) {
+    if (auto* parent = dyn_cast_or_null<T>(*i)) {
+      return parent;
+    }
+  }
+  return nullptr;
+}
+
+
+bool CheckIPCVisitor::IsBlacklistedType(QualType type) const {
+  return context_->hasSameUnqualifiedType(type, context_->LongTy) ||
+      context_->hasSameUnqualifiedType(type, context_->UnsignedLongTy);
+}
+
+bool CheckIPCVisitor::IsBlacklistedTypedef(const TypedefNameDecl* tdef) const {
+  return blacklisted_typedefs_.find(tdef->getName()) !=
+      blacklisted_typedefs_.end();
+}
+
+// Checks that integer type is allowed (not blacklisted).
+bool CheckIPCVisitor::CheckIntegerType(QualType type,
+                                       CheckDetails* details) const {
+  bool seen_typedef = false;
+  while (true) {
+    details->exit_type = type;
+
+    if (auto* tdef = dyn_cast<TypedefType>(type)) {
+      if (IsBlacklistedTypedef(tdef->getDecl())) {
+        return false;
+      }
+      details->typedefs.push_back(tdef);
+      seen_typedef = true;
+    }
+
+    QualType desugared_type =
+        type->getLocallyUnqualifiedSingleStepDesugaredType();
+    if (desugared_type == type) {
+      break;
+    }
+
+    type = desugared_type;
+  }
+
+  return seen_typedef || !IsBlacklistedType(type);
+}
+
+// Checks that |type| is allowed (not blacklisted), recursively visiting
+// template specializations.
+bool CheckIPCVisitor::CheckType(QualType type, CheckDetails* details) const {
+  if (type->isReferenceType()) {
+    type = type->getPointeeType();
+  }
+  type = type.getLocalUnqualifiedType();
+
+  if (details->entry_type.isNull()) {
+    details->entry_type = type;
+  }
+
+  if (type->isIntegerType()) {
+    return CheckIntegerType(type, details);
+  }
+
+  while (true) {
+    if (auto* spec = dyn_cast<TemplateSpecializationType>(type)) {
+      for (const TemplateArgument& arg: *spec) {
+        if (!CheckTemplateArgument(arg, details)) {
+          return false;
+        }
+      }
+      return true;
+    }
+
+    if (auto* record = dyn_cast<RecordType>(type)) {
+      if (auto* spec = dyn_cast<ClassTemplateSpecializationDecl>(
+              record->getDecl())) {
+        const TemplateArgumentList& args = spec->getTemplateArgs();
+        for (unsigned i = 0; i != args.size(); ++i) {
+          if (!CheckTemplateArgument(args[i], details)) {
+            return false;
+          }
+        }
+      }
+      return true;
+    }
+
+    if (auto* tdef = dyn_cast<TypedefType>(type)) {
+      details->typedefs.push_back(tdef);
+    }
+
+    QualType desugared_type =
+        type->getLocallyUnqualifiedSingleStepDesugaredType();
+    if (desugared_type == type) {
+      break;
+    }
+
+    type = desugared_type;
+  }
+
+  return true;
+}
+
+bool CheckIPCVisitor::CheckTemplateArgument(const TemplateArgument& arg,
+                                            CheckDetails* details) const {
+  return arg.getKind() != TemplateArgument::Type ||
+      CheckType(arg.getAsType(), details);
+}
+
+void CheckIPCVisitor::ReportCheckError(const CheckDetails& details,
+                                       SourceLocation loc,
+                                       unsigned error) {
+  DiagnosticsEngine& diagnostics = compiler_.getDiagnostics();
+
+  std::string entry_type = details.entry_type.getAsString();
+  std::string exit_type = details.exit_type.getAsString();
+
+  std::string via;
+  if (entry_type != exit_type) {
+    via = " via '" + entry_type + "'";
+  }
+  diagnostics.Report(loc, error) << exit_type << via;
+
+  for (const TypedefType* tdef: details.typedefs) {
+    diagnostics.Report(tdef->getDecl()->getLocation(), note_see_here_);
+  }
+}
+
+}  // namespace chrome_checker