1 //===- MetaRenamer.cpp - Rename everything with metasyntatic names --------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This pass renames everything with metasyntatic names. The intent is to use
11 // this pass after bugpoint reduction to conceal the nature of the original
12 // program.
13 //
14 //===----------------------------------------------------------------------===//
15 
16 #include "llvm/Transforms/IPO.h"
17 #include "llvm/ADT/STLExtras.h"
18 #include "llvm/ADT/SmallString.h"
19 #include "llvm/IR/DerivedTypes.h"
20 #include "llvm/IR/Function.h"
21 #include "llvm/IR/Module.h"
22 #include "llvm/IR/Type.h"
23 #include "llvm/IR/TypeFinder.h"
24 #include "llvm/Pass.h"
25 using namespace llvm;
26 
27 namespace {
28 
29   // This PRNG is from the ISO C spec. It is intentionally simple and
30   // unsuitable for cryptographic use. We're just looking for enough
31   // variety to surprise and delight users.
32   struct PRNG {
33     unsigned long next;
34 
35     void srand(unsigned int seed) {
36       next = seed;
37     }
38 
39     int rand() {
40       next = next * 1103515245 + 12345;
41       return (unsigned int)(next / 65536) % 32768;
42     }
43   };
44 
45   struct MetaRenamer : public ModulePass {
46     static char ID; // Pass identification, replacement for typeid
47     MetaRenamer() : ModulePass(ID) {
48       initializeMetaRenamerPass(*PassRegistry::getPassRegistry());
49     }
50 
51     void getAnalysisUsage(AnalysisUsage &AU) const {
52       AU.setPreservesAll();
53     }
54 
55     bool runOnModule(Module &M) {
56       static const char *metaNames[] = {
57         // See http://en.wikipedia.org/wiki/Metasyntactic_variable
58         "foo", "bar", "baz", "quux", "barney", "snork", "zot", "blam", "hoge",
59         "wibble", "wobble", "widget", "wombat", "ham", "eggs", "pluto", "spam"
60       };
61 
62       // Seed our PRNG with simple additive sum of ModuleID. We're looking to
63       // simply avoid always having the same function names, and we need to
64       // remain deterministic.
65       unsigned int randSeed = 0;
66       for (std::string::const_iterator I = M.getModuleIdentifier().begin(),
67            E = M.getModuleIdentifier().end(); I != E; ++I)
68         randSeed += *I;
69 
70       PRNG prng;
71       prng.srand(randSeed);
72 
73       // Rename all aliases
74       for (Module::alias_iterator AI = M.alias_begin(), AE = M.alias_end();
75            AI != AE; ++AI)
76         AI->setName("alias");
77 
78       // Rename all global variables
79       for (Module::global_iterator GI = M.global_begin(), GE = M.global_end();
80            GI != GE; ++GI)
81         GI->setName("global");
82 
83       // Rename all struct types
84       TypeFinder StructTypes;
85       StructTypes.run(M, true);
86       for (unsigned i = 0, e = StructTypes.size(); i != e; ++i) {
87         StructType *STy = StructTypes[i];
88         if (STy->isLiteral() || STy->getName().empty()) continue;
89 
90         SmallString<128> NameStorage;
91         STy->setName((Twine("struct.") + metaNames[prng.rand() %
92                      array_lengthof(metaNames)]).toStringRef(NameStorage));
93       }
94 
95       // Rename all functions
96       for (Module::iterator FI = M.begin(), FE = M.end();
97            FI != FE; ++FI) {
98         FI->setName(metaNames[prng.rand() % array_lengthof(metaNames)]);
99         runOnFunction(*FI);
100       }
101       return true;
102     }
103 
104     bool runOnFunction(Function &F) {
105       for (Function::arg_iterator AI = F.arg_begin(), AE = F.arg_end();
106            AI != AE; ++AI)
107         if (!AI->getType()->isVoidTy())
108           AI->setName("arg");
109 
110       for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
111         BB->setName("bb");
112 
113         for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I)
114           if (!I->getType()->isVoidTy())
115             I->setName("tmp");
116       }
117       return true;
118     }
119   };
120 }
121 
122 char MetaRenamer::ID = 0;
123 INITIALIZE_PASS(MetaRenamer, "metarenamer",
124                 "Assign new names to everything", false, false)
125 //===----------------------------------------------------------------------===//
126 //
127 // MetaRenamer - Rename everything with metasyntactic names.
128 //
129 ModulePass *llvm::createMetaRenamerPass() {
130   return new MetaRenamer();
131 }
132