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      1 /*
      2  * Copyright 2014, The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *     http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 #include "Log.h"
     18 #include "RSTransforms.h"
     19 #include "RSStubsWhiteList.h"
     20 
     21 #include <cstdlib>
     22 
     23 #include <llvm/IR/Instructions.h>
     24 #include <llvm/IR/Module.h>
     25 #include <llvm/IR/Function.h>
     26 #include <llvm/Pass.h>
     27 
     28 namespace { // anonymous namespace
     29 
     30 // Create a Module pass that screens all the global functions in the
     31 // module and check if any disallowed external function is accessible
     32 // and potentially callable.
     33 class RSScreenFunctionsPass : public llvm::ModulePass {
     34 private:
     35   static char ID;
     36 
     37   std::vector<std::string> &whiteList = stubList;
     38 
     39   bool isPresent(std::vector<std::string> &list, const std::string &name) {
     40     auto lower = std::lower_bound(list.begin(),
     41                                   list.end(),
     42                                   name);
     43 
     44     if (lower != list.end() && name.compare(*lower) == 0)
     45       return true;
     46     return false;
     47   }
     48 
     49   bool isLegal(llvm::Function &F) {
     50     // A global function symbol is legal if
     51     // a. it has a body, i.e. is not empty or
     52     // b. its name starts with "llvm." or
     53     // c. it is present in the whitelist
     54 
     55     if (!F.empty())
     56       return true;
     57 
     58     llvm::StringRef FName = F.getName();
     59     if (FName.startswith("llvm."))
     60       return true;
     61 
     62     if (isPresent(whiteList, FName.str()))
     63       return true;
     64 
     65     return false;
     66   }
     67 
     68 public:
     69   RSScreenFunctionsPass()
     70     : ModulePass (ID) {
     71       std::sort(whiteList.begin(), whiteList.end());
     72   }
     73 
     74   virtual void getAnalysisUsage(llvm::AnalysisUsage &AU) const override {
     75     AU.setPreservesAll();
     76   }
     77 
     78   bool runOnModule(llvm::Module &M) override {
     79     bool failed = false;
     80 
     81     auto &FunctionList(M.getFunctionList());
     82     for(auto &F: FunctionList) {
     83       if (!isLegal(F)) {
     84         ALOGE("Call to function %s from RenderScript is disallowed\n",
     85               F.getName().str().c_str());
     86         failed = true;
     87       }
     88     }
     89 
     90     if (failed) {
     91       llvm::report_fatal_error("Use of undefined external function");
     92     }
     93 
     94     return false;
     95   }
     96 
     97 };
     98 
     99 }
    100 
    101 char RSScreenFunctionsPass::ID = 0;
    102 
    103 namespace bcc {
    104 
    105 llvm::ModulePass *
    106 createRSScreenFunctionsPass() {
    107   return new RSScreenFunctionsPass();
    108 }
    109 
    110 }
    111