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//===- MetaRenamer.cpp - Rename everything with metasyntatic names --------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This pass renames everything with metasyntatic names. The intent is to use
// this pass after bugpoint reduction to conceal the nature of the original
// program.
//
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/IPO.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/Type.h"
#include "llvm/IR/TypeFinder.h"
#include "llvm/Pass.h"
using namespace llvm;
namespace {
// This PRNG is from the ISO C spec. It is intentionally simple and
// unsuitable for cryptographic use. We're just looking for enough
// variety to surprise and delight users.
struct PRNG {
unsigned long next;
void srand(unsigned int seed) {
next = seed;
}
int rand() {
next = next * 1103515245 + 12345;
return (unsigned int)(next / 65536) % 32768;
}
};
struct MetaRenamer : public ModulePass {
static char ID; // Pass identification, replacement for typeid
MetaRenamer() : ModulePass(ID) {
initializeMetaRenamerPass(*PassRegistry::getPassRegistry());
}
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.setPreservesAll();
}
bool runOnModule(Module &M) override {
static const char *const metaNames[] = {
// See http://en.wikipedia.org/wiki/Metasyntactic_variable
"foo", "bar", "baz", "quux", "barney", "snork", "zot", "blam", "hoge",
"wibble", "wobble", "widget", "wombat", "ham", "eggs", "pluto", "spam"
};
// Seed our PRNG with simple additive sum of ModuleID. We're looking to
// simply avoid always having the same function names, and we need to
// remain deterministic.
unsigned int randSeed = 0;
for (std::string::const_iterator I = M.getModuleIdentifier().begin(),
E = M.getModuleIdentifier().end(); I != E; ++I)
randSeed += *I;
PRNG prng;
prng.srand(randSeed);
// Rename all aliases
for (Module::alias_iterator AI = M.alias_begin(), AE = M.alias_end();
AI != AE; ++AI) {
StringRef Name = AI->getName();
if (Name.startswith("llvm.") || (!Name.empty() && Name[0] == 1))
continue;
AI->setName("alias");
}
// Rename all global variables
for (Module::global_iterator GI = M.global_begin(), GE = M.global_end();
GI != GE; ++GI) {
StringRef Name = GI->getName();
if (Name.startswith("llvm.") || (!Name.empty() && Name[0] == 1))
continue;
GI->setName("global");
}
// Rename all struct types
TypeFinder StructTypes;
StructTypes.run(M, true);
for (unsigned i = 0, e = StructTypes.size(); i != e; ++i) {
StructType *STy = StructTypes[i];
if (STy->isLiteral() || STy->getName().empty()) continue;
SmallString<128> NameStorage;
STy->setName((Twine("struct.") + metaNames[prng.rand() %
array_lengthof(metaNames)]).toStringRef(NameStorage));
}
// Rename all functions
for (Module::iterator FI = M.begin(), FE = M.end();
FI != FE; ++FI) {
StringRef Name = FI->getName();
if (Name.startswith("llvm.") || (!Name.empty() && Name[0] == 1))
continue;
FI->setName(metaNames[prng.rand() % array_lengthof(metaNames)]);
runOnFunction(*FI);
}
return true;
}
bool runOnFunction(Function &F) {
for (Function::arg_iterator AI = F.arg_begin(), AE = F.arg_end();
AI != AE; ++AI)
if (!AI->getType()->isVoidTy())
AI->setName("arg");
for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
BB->setName("bb");
for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I)
if (!I->getType()->isVoidTy())
I->setName("tmp");
}
return true;
}
};
}
char MetaRenamer::ID = 0;
INITIALIZE_PASS(MetaRenamer, "metarenamer",
"Assign new names to everything", false, false)
//===----------------------------------------------------------------------===//
//
// MetaRenamer - Rename everything with metasyntactic names.
//
ModulePass *llvm::createMetaRenamerPass() {
return new MetaRenamer();
}
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