139 lines
4.8 KiB
C++
139 lines
4.8 KiB
C++
//===-- MCFunction.cpp ----------------------------------------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file defines the algorithm to break down a region of machine code
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// into basic blocks and try to reconstruct a CFG from it.
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//
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//===----------------------------------------------------------------------===//
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#include "MCFunction.h"
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#include "llvm/ADT/STLExtras.h"
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#include "llvm/MC/MCDisassembler.h"
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#include "llvm/MC/MCInst.h"
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#include "llvm/MC/MCInstPrinter.h"
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#include "llvm/MC/MCInstrAnalysis.h"
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#include "llvm/MC/MCInstrDesc.h"
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#include "llvm/MC/MCInstrInfo.h"
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#include "llvm/Support/MemoryObject.h"
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#include "llvm/Support/raw_ostream.h"
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#include "llvm/Support/system_error.h"
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#include <set>
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using namespace llvm;
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MCFunction
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MCFunction::createFunctionFromMC(StringRef Name, const MCDisassembler *DisAsm,
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const MemoryObject &Region, uint64_t Start,
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uint64_t End, const MCInstrAnalysis *Ana,
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raw_ostream &DebugOut,
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SmallVectorImpl<uint64_t> &Calls) {
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std::vector<MCDecodedInst> Instructions;
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std::set<uint64_t> Splits;
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Splits.insert(Start);
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uint64_t Size;
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MCFunction f(Name);
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{
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DenseSet<uint64_t> VisitedInsts;
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SmallVector<uint64_t, 16> WorkList;
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WorkList.push_back(Start);
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// Disassemble code and gather basic block split points.
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while (!WorkList.empty()) {
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uint64_t Index = WorkList.pop_back_val();
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if (VisitedInsts.find(Index) != VisitedInsts.end())
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continue; // Already visited this location.
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for (;Index < End; Index += Size) {
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VisitedInsts.insert(Index);
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MCInst Inst;
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if (DisAsm->getInstruction(Inst, Size, Region, Index, DebugOut, nulls())){
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Instructions.push_back(MCDecodedInst(Index, Size, Inst));
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if (Ana->isBranch(Inst)) {
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uint64_t targ = Ana->evaluateBranch(Inst, Index, Size);
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if (targ != -1ULL && targ == Index+Size)
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continue; // Skip nop jumps.
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// If we could determine the branch target, make a note to start a
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// new basic block there and add the target to the worklist.
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if (targ != -1ULL) {
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Splits.insert(targ);
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WorkList.push_back(targ);
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WorkList.push_back(Index+Size);
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}
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Splits.insert(Index+Size);
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break;
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} else if (Ana->isReturn(Inst)) {
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// Return instruction. This basic block ends here.
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Splits.insert(Index+Size);
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break;
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} else if (Ana->isCall(Inst)) {
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uint64_t targ = Ana->evaluateBranch(Inst, Index, Size);
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// Add the call to the call list if the destination is known.
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if (targ != -1ULL && targ != Index+Size)
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Calls.push_back(targ);
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}
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} else {
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errs().write_hex(Index) << ": warning: invalid instruction encoding\n";
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if (Size == 0)
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Size = 1; // skip illegible bytes
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}
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}
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}
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}
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// Make sure the instruction list is sorted.
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std::sort(Instructions.begin(), Instructions.end());
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// Create basic blocks.
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unsigned ii = 0, ie = Instructions.size();
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for (std::set<uint64_t>::iterator spi = Splits.begin(),
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spe = llvm::prior(Splits.end()); spi != spe; ++spi) {
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MCBasicBlock BB;
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uint64_t BlockEnd = *llvm::next(spi);
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// Add instructions to the BB.
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for (; ii != ie; ++ii) {
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if (Instructions[ii].Address < *spi ||
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Instructions[ii].Address >= BlockEnd)
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break;
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BB.addInst(Instructions[ii]);
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}
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f.addBlock(*spi, BB);
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}
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std::sort(f.Blocks.begin(), f.Blocks.end());
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// Calculate successors of each block.
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for (MCFunction::iterator i = f.begin(), e = f.end(); i != e; ++i) {
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MCBasicBlock &BB = const_cast<MCBasicBlock&>(i->second);
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if (BB.getInsts().empty()) continue;
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const MCDecodedInst &Inst = BB.getInsts().back();
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if (Ana->isBranch(Inst.Inst)) {
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uint64_t targ = Ana->evaluateBranch(Inst.Inst, Inst.Address, Inst.Size);
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if (targ == -1ULL) {
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// Indirect branch. Bail and add all blocks of the function as a
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// successor.
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for (MCFunction::iterator i = f.begin(), e = f.end(); i != e; ++i)
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BB.addSucc(i->first);
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} else if (targ != Inst.Address+Inst.Size)
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BB.addSucc(targ);
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// Conditional branches can also fall through to the next block.
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if (Ana->isConditionalBranch(Inst.Inst) && llvm::next(i) != e)
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BB.addSucc(llvm::next(i)->first);
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} else {
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// No branch. Fall through to the next block.
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if (!Ana->isReturn(Inst.Inst) && llvm::next(i) != e)
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BB.addSucc(llvm::next(i)->first);
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}
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}
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return f;
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}
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