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AFLplusplus/llvm_mode/afl-llvm-lto-instrumentation.so.cc

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/*
american fuzzy lop++ - LLVM-mode instrumentation pass
---------------------------------------------------
Written by Laszlo Szekeres <lszekeres@google.com> and
Michal Zalewski
LLVM integration design comes from Laszlo Szekeres. C bits copied-and-pasted
from afl-as.c are Michal's fault.
Copyright 2015, 2016 Google Inc. All rights reserved.
Copyright 2019-2020 AFLplusplus Project. All rights reserved.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at:
http://www.apache.org/licenses/LICENSE-2.0
This library is plugged into LLVM when invoking clang through afl-clang-fast.
It tells the compiler to add code roughly equivalent to the bits discussed
in ../afl-as.h.
*/
// CONFIG OPTION:
// If #define USE_SPLIT is used, then the llvm::SplitEdge function is used
// instead of our own implementation. Ours looks better and will
// compile everywhere. But it is not working for complex code. yet. damn.
#define USE_SPLIT
#define AFL_LLVM_PASS
#include "config.h"
#include "debug.h"
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <list>
#include <string>
#include <fstream>
#include <sys/time.h>
#include "llvm/Config/llvm-config.h"
#if LLVM_VERSION_MAJOR == 3 && LLVM_VERSION_MINOR < 5
typedef long double max_align_t;
#endif
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/LegacyPassManager.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/Module.h"
#include "llvm/Support/Debug.h"
#include "llvm/Transforms/IPO/PassManagerBuilder.h"
#ifdef USE_SPLIT
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/MemorySSAUpdater.h"
#endif
#if LLVM_VERSION_MAJOR > 3 || \
(LLVM_VERSION_MAJOR == 3 && LLVM_VERSION_MINOR > 4)
#include "llvm/IR/DebugInfo.h"
#include "llvm/IR/CFG.h"
#else
#include "llvm/DebugInfo.h"
#include "llvm/Support/CFG.h"
#endif
using namespace llvm;
namespace {
class AFLLTOPass : public ModulePass {
public:
static char ID;
AFLLTOPass() : ModulePass(ID) {
char *ptr;
if (getenv("AFL_DEBUG")) debug = 1;
if ((ptr = getenv("AFL_LLVM_LTO_STARTID")) != NULL)
if ((afl_global_id = atoi(ptr)) < 0 || afl_global_id >= MAP_SIZE)
FATAL("AFL_LLVM_LTO_STARTID value of \"%s\" is not between 0 and %d\n",
ptr, MAP_SIZE - 1);
}
#ifdef USE_SPLIT
void getAnalysisUsage(AnalysisUsage &AU) const override {
ModulePass::getAnalysisUsage(AU);
AU.addRequired<DominatorTreeWrapperPass>();
AU.addRequired<LoopInfoWrapperPass>();
}
#endif
// Calculate the number of average collisions that would occur if all
// location IDs would be assigned randomly (like normal afl/afl++).
// This uses the "balls in bins" algorithm.
unsigned long long int calculateCollisions(uint32_t edges) {
double bins = MAP_SIZE;
double balls = edges;
double step1 = 1 - (1 / bins);
double step2 = pow(step1, balls);
double step3 = bins * step2;
double step4 = round(step3);
unsigned long long int empty = step4;
unsigned long long int collisions = edges - (MAP_SIZE - empty);
return collisions;
}
// Get the internal llvm name of a basic block
// This is an ugly debug support so it is commented out :-)
/*
static char *getBBName(const BasicBlock *BB) {
static char *name;
if (!BB->getName().empty()) {
name = strdup(BB->getName().str().c_str());
return name;
}
std::string Str;
raw_string_ostream OS(Str);
BB->printAsOperand(OS, false);
name = strdup(OS.str().c_str());
return name;
}
*/
static bool isBlacklisted(const Function *F) {
static const char *Blacklist[] = {
"asan.", "llvm.", "sancov.", "__ubsan_handle_", "ign.",
"__afl_", "_fini", "__libc_csu"
};
for (auto const &BlacklistFunc : Blacklist) {
if (F->getName().startswith(BlacklistFunc)) { return true; }
}
return false;
}
bool runOnModule(Module &M) override;
protected:
int afl_global_id = 1, debug = 0;
uint32_t be_quiet = 0, inst_blocks = 0, inst_funcs = 0, total_instr = 0;
};
} // namespace
bool AFLLTOPass::runOnModule(Module &M) {
LLVMContext &C = M.getContext();
IntegerType * Int8Ty = IntegerType::getInt8Ty(C);
IntegerType * Int32Ty = IntegerType::getInt32Ty(C);
struct timeval tv;
struct timezone tz;
u32 rand_seed;
/* Setup random() so we get Actually Random(TM) outputs from AFL_R() */
gettimeofday(&tv, &tz);
rand_seed = tv.tv_sec ^ tv.tv_usec ^ getpid();
AFL_SR(rand_seed);
/* Show a banner */
if ((isatty(2) && !getenv("AFL_QUIET")) || getenv("AFL_DEBUG") != NULL) {
SAYF(cCYA "afl-llvm-lto" VERSION cRST
" by Marc \"vanHauser\" Heuse <mh@mh-sec.de>\n");
} else
be_quiet = 1;
#if LLVM_VERSION_MAJOR < 9
char *neverZero_counters_str = getenv("AFL_LLVM_NOT_ZERO");
#endif
/* Get globals for the SHM region and the previous location. Note that
__afl_prev_loc is thread-local. */
GlobalVariable *AFLMapPtr =
new GlobalVariable(M, PointerType::get(Int8Ty, 0), false,
GlobalValue::ExternalLinkage, 0, "__afl_area_ptr");
ConstantInt *Zero = ConstantInt::get(Int8Ty, 0);
ConstantInt *One = ConstantInt::get(Int8Ty, 1);
/* Instrument all the things! */
int inst_blocks = 0;
for (auto &F : M) {
if (F.size() < 2) continue;
if (isBlacklisted(&F)) continue;
#ifdef USE_SPLIT
// DominatorTree &DT =
// getAnalysis<DominatorTreeWrapperPass>(F).getDomTree(); LoopInfo & LI =
// getAnalysis<LoopInfoWrapperPass>(F).getLoopInfo();
#endif
std::vector<BasicBlock *> InsBlocks;
for (auto &BB : F) {
uint32_t succ = 0;
for (succ_iterator SI = succ_begin(&BB), SE = succ_end(&BB); SI != SE;
++SI)
if ((*SI)->size() > 0) succ++;
if (succ < 2) // no need to instrument
continue;
InsBlocks.push_back(&BB);
}
if (InsBlocks.size() > 0) {
uint32_t i = InsBlocks.size();
do {
--i;
BasicBlock * origBB = &(*InsBlocks[i]);
std::vector<BasicBlock *> Successors;
Instruction * TI = origBB->getTerminator();
for (succ_iterator SI = succ_begin(origBB), SE = succ_end(origBB);
SI != SE; ++SI) {
BasicBlock *succ = *SI;
Successors.push_back(succ);
}
if (TI == NULL || TI->getNumSuccessors() < 2) continue;
// if (Successors.size() != TI->getNumSuccessors())
// FATAL("Different successor numbers %lu <-> %u\n", Successors.size(),
// TI->getNumSuccessors());
for (uint32_t j = 0; j < Successors.size(); j++) {
#ifdef USE_SPLIT
BasicBlock *newBB = llvm::SplitEdge(origBB, Successors[j]);
#else
BasicBlock *newBB = BasicBlock::Create(C, "", &F, nullptr);
#endif
if (!newBB) {
if (!be_quiet) WARNF("Split failed!");
continue;
}
#ifdef USE_SPLIT
BasicBlock::iterator IP = newBB->getFirstInsertionPt();
IRBuilder<> IRB(&(*IP));
#else
IRBuilder<> IRB(&(*newBB));
#endif
/* Set the ID of the inserted basic block */
ConstantInt *CurLoc = ConstantInt::get(Int32Ty, afl_global_id++);
/* Load SHM pointer */
LoadInst *MapPtr = IRB.CreateLoad(AFLMapPtr);
MapPtr->setMetadata(M.getMDKindID("nosanitize"),
MDNode::get(C, None));
Value *MapPtrIdx = IRB.CreateGEP(MapPtr, CurLoc);
/* Update bitmap */
LoadInst *Counter = IRB.CreateLoad(MapPtrIdx);
Counter->setMetadata(M.getMDKindID("nosanitize"),
MDNode::get(C, None));
Value *Incr = IRB.CreateAdd(Counter, One);
#if LLVM_VERSION_MAJOR < 9
if (neverZero_counters_str !=
NULL) { // with llvm 9 we make this the default as the bug in
// llvm is then fixed
#endif
auto cf = IRB.CreateICmpEQ(Incr, Zero);
auto carry = IRB.CreateZExt(cf, Int8Ty);
Incr = IRB.CreateAdd(Incr, carry);
#if LLVM_VERSION_MAJOR < 9
}
#endif
IRB.CreateStore(Incr, MapPtrIdx)
->setMetadata(M.getMDKindID("nosanitize"), MDNode::get(C, None));
#ifdef USE_SPLIT
// nothing
#else
// Unconditional jump to the destination BB
IRB.CreateBr(Successors[j]);
// Replace the original destination to this newly inserted BB
origBB->replacePhiUsesWith(Successors[j], newBB);
BasicBlock *S = Successors[j];
S->replacePhiUsesWith(origBB, newBB);
TI->setSuccessor(j, newBB);
#endif
// done :)
inst_blocks++;
}
} while (i > 0);
}
}
// save highest location ID to global variable
if (afl_global_id > MAP_SIZE) {
uint32_t pow2map = 1, map = afl_global_id;
while ((map = map >> 1))
pow2map++;
FATAL(
"We have %u blocks to instrument but the map size is only %u! Edit "
"config.h and set MAP_SIZE_POW2 from %u to %u, then recompile "
"afl-fuzz and llvm_mode.",
afl_global_id, MAP_SIZE, MAP_SIZE_POW2, pow2map);
}
if (getenv("AFL_LLVM_LTO_DONTWRITEID") == NULL) {
GlobalVariable *AFLFinalLoc = new GlobalVariable(
M, Int32Ty, true, GlobalValue::ExternalLinkage, 0, "__afl_final_loc", 0,
GlobalVariable::GeneralDynamicTLSModel, 0, false);
ConstantInt *const_loc = ConstantInt::get(Int32Ty, afl_global_id);
AFLFinalLoc->setAlignment(4);
AFLFinalLoc->setInitializer(const_loc);
}
/* Say something nice. */
if (!be_quiet) {
if (!inst_blocks)
WARNF("No instrumentation targets found.");
else {
char modeline[100];
snprintf(modeline, sizeof(modeline), "%s%s%s%s",
getenv("AFL_HARDEN") ? "hardened" : "non-hardened",
getenv("AFL_USE_ASAN") ? ", ASAN" : "",
getenv("AFL_USE_MSAN") ? ", MSAN" : "",
getenv("AFL_USE_UBSAN") ? ", UBSAN" : "");
OKF("Instrumented %u locations with no collisions (on average %llu "
"collisions would be in afl-gcc/afl-clang-fast) (%s mode).",
inst_blocks, calculateCollisions(inst_blocks), modeline);
}
}
return true;
}
char AFLLTOPass::ID = 0;
static void registerAFLLTOPass(const PassManagerBuilder &,
legacy::PassManagerBase &PM) {
PM.add(new AFLLTOPass());
}
static RegisterPass<AFLLTOPass> X("afl-lto", "afl++ LTO instrumentation pass",
false, false);
static RegisterStandardPasses RegisterAFLLTOPass(
PassManagerBuilder::EP_OptimizerLast, registerAFLLTOPass);
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