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
srand__anon2e7cb32d0111::PRNG35 void srand(unsigned int seed) {
36 next = seed;
37 }
38
rand__anon2e7cb32d0111::PRNG39 int rand() {
40 next = next * 1103515245 + 12345;
41 return (unsigned int)(next / 65536) % 32768;
42 }
43 };
44
45 static const char *const metaNames[] = {
46 // See http://en.wikipedia.org/wiki/Metasyntactic_variable
47 "foo", "bar", "baz", "quux", "barney", "snork", "zot", "blam", "hoge",
48 "wibble", "wobble", "widget", "wombat", "ham", "eggs", "pluto", "spam"
49 };
50
51 struct Renamer {
Renamer__anon2e7cb32d0111::Renamer52 Renamer(unsigned int seed) {
53 prng.srand(seed);
54 }
55
newName__anon2e7cb32d0111::Renamer56 const char *newName() {
57 return metaNames[prng.rand() % array_lengthof(metaNames)];
58 }
59
60 PRNG prng;
61 };
62
63 struct MetaRenamer : public ModulePass {
64 static char ID; // Pass identification, replacement for typeid
MetaRenamer__anon2e7cb32d0111::MetaRenamer65 MetaRenamer() : ModulePass(ID) {
66 initializeMetaRenamerPass(*PassRegistry::getPassRegistry());
67 }
68
getAnalysisUsage__anon2e7cb32d0111::MetaRenamer69 void getAnalysisUsage(AnalysisUsage &AU) const override {
70 AU.setPreservesAll();
71 }
72
runOnModule__anon2e7cb32d0111::MetaRenamer73 bool runOnModule(Module &M) override {
74 // Seed our PRNG with simple additive sum of ModuleID. We're looking to
75 // simply avoid always having the same function names, and we need to
76 // remain deterministic.
77 unsigned int randSeed = 0;
78 for (auto C : M.getModuleIdentifier())
79 randSeed += C;
80
81 Renamer renamer(randSeed);
82
83 // Rename all aliases
84 for (auto AI = M.alias_begin(), AE = M.alias_end(); AI != AE; ++AI) {
85 StringRef Name = AI->getName();
86 if (Name.startswith("llvm.") || (!Name.empty() && Name[0] == 1))
87 continue;
88
89 AI->setName("alias");
90 }
91
92 // Rename all global variables
93 for (auto GI = M.global_begin(), GE = M.global_end(); GI != GE; ++GI) {
94 StringRef Name = GI->getName();
95 if (Name.startswith("llvm.") || (!Name.empty() && Name[0] == 1))
96 continue;
97
98 GI->setName("global");
99 }
100
101 // Rename all struct types
102 TypeFinder StructTypes;
103 StructTypes.run(M, true);
104 for (StructType *STy : StructTypes) {
105 if (STy->isLiteral() || STy->getName().empty()) continue;
106
107 SmallString<128> NameStorage;
108 STy->setName((Twine("struct.") +
109 renamer.newName()).toStringRef(NameStorage));
110 }
111
112 // Rename all functions
113 for (auto &F : M) {
114 StringRef Name = F.getName();
115 if (Name.startswith("llvm.") || (!Name.empty() && Name[0] == 1))
116 continue;
117
118 F.setName(renamer.newName());
119 runOnFunction(F);
120 }
121 return true;
122 }
123
runOnFunction__anon2e7cb32d0111::MetaRenamer124 bool runOnFunction(Function &F) {
125 for (auto AI = F.arg_begin(), AE = F.arg_end(); AI != AE; ++AI)
126 if (!AI->getType()->isVoidTy())
127 AI->setName("arg");
128
129 for (auto &BB : F) {
130 BB.setName("bb");
131
132 for (auto &I : BB)
133 if (!I.getType()->isVoidTy())
134 I.setName("tmp");
135 }
136 return true;
137 }
138 };
139 }
140
141 char MetaRenamer::ID = 0;
142 INITIALIZE_PASS(MetaRenamer, "metarenamer",
143 "Assign new names to everything", false, false)
144 //===----------------------------------------------------------------------===//
145 //
146 // MetaRenamer - Rename everything with metasyntactic names.
147 //
createMetaRenamerPass()148 ModulePass *llvm::createMetaRenamerPass() {
149 return new MetaRenamer();
150 }
151