void doJumpIndexTableViaSwitch(
BasicBlock *&block,
InstPtr ip)
{
Function *F = block->getParent();
Module *M = F->getParent();
// we know this conforms to
// movzx reg32, [base+disp]
// sanity check
const MCInst &inst = ip->get_inst();
const MCOperand& dest = OP(0);
const MCOperand& base = OP(1);
TASSERT(base.isReg(), "Conformant jump index tables need base to be a register");
TASSERT(dest.isReg(), "Conformant jump index tables need to write to a register");
JumpIndexTablePtr idxptr = ip->get_jump_index_table();
// to ensure no negative entries
Value *adjustment = CONST_V<32>(block, idxptr->getInitialEntry());
Value *reg_val = R_READ<32>(block, base.getReg());
Value *real_index =
BinaryOperator::Create(Instruction::Add, adjustment, reg_val, "", block);
BasicBlock *continueBlock =
BasicBlock::Create(block->getContext(), "", F, 0);
// create a default block that just traps
BasicBlock *defaultBlock =
BasicBlock::Create(block->getContext(), "", F, 0);
Function *trapFn = Intrinsic::getDeclaration(M, Intrinsic::trap);
CallInst::Create(trapFn, "", defaultBlock);
BranchInst::Create(continueBlock, defaultBlock);
// end default block
const std::vector<uint8_t> &idxblocks = idxptr->getJumpIndexTable();
// create a switch inst
SwitchInst *theSwitch = SwitchInst::Create(
real_index,
defaultBlock,
idxblocks.size(),
block);
// populate switch
int myindex = 0;
for(std::vector<uint8_t>::const_iterator itr = idxblocks.begin();
itr != idxblocks.end();
itr++)
{
BasicBlock *writeBl = emitJumpIndexWrite(F, *itr, dest.getReg(), continueBlock );
theSwitch->addCase(CONST_V<32>(block, myindex), writeBl);
++myindex;
}
// new block to write to is continue block
block = continueBlock;
}
// assume the immediate references code if:
// * we are dealing with a fully linked ELF
// * The immediate is in the range of a valid code or data section
static bool setHeuristicRef(ExecutableContainer *c,
InstPtr I,
int opnum,
stack<VA> &funcs,
raw_ostream &out,
const std::string whichInst)
{
MCOperand op;
std::string imp_name;
ElfTarget *elft = dynamic_cast<ElfTarget*>(c);
op = I->get_inst().getOperand(opnum);
LASSERT(op.isImm(), "No immediate operand for " + whichInst);
VA imm = op.getImm();
if(elft && elft->isLinked()) {
if (elft->is_in_code(imm)) {
// this instruction references code
I->set_call_tgt(imm);
// make sure we disassemble at this new address
funcs.push(imm);
out << "Found new function entry from " << whichInst << ": " << to_string<VA>(imm, hex) << "\n";
return true;
} else if (elft->is_in_data(imm)) {
out << "Adding local data ref to: " << to_string<VA>(imm, hex) << "\n";
I->set_data_offset(imm);
} else if (c->find_import_name(imm, imp_name)) {
out << "Import name is: " << imp_name << "\n";
}
}
return false;
}
bool dataInCodeHeuristic(
ExecutableContainer *c,
InstPtr I,
uint32_t addr,
list<VA> &funcs,
uint32_t relocSize)
{
// detect SEH handler
if(I->get_inst().getOpcode() == X86::PUSHi32) {
uint32_t dw1;
uint8_t *ptr = (uint8_t*)&dw1;
c->readByte(addr+0, ptr+0);
c->readByte(addr+1, ptr+1);
c->readByte(addr+2, ptr+2);
c->readByte(addr+3, ptr+3);
if(dw1 == 0xFFFFFFFE) {
llvm::outs() << "WARNING: Heuristically detected SEH handler at: "
<< to_string<VA>(addr, hex) << "\n";
return treatCodeAsData(c, addr, 0x28, funcs);
}
} else {
return treatCodeAsData(c, addr, relocSize, funcs);
}
return false;
}
// return true if this instruction
// branches via a memory lookup
static bool isBranchViaMemory(InstPtr inst) {
switch(inst->get_inst().getOpcode()) {
case X86::JMP32m:
case X86::CALL32m:
return true;
default:
return false;
}
}
static bool processJumpIndexTable(ExecutableContainer *c,
NativeBlockPtr B,
InstPtr jmpinst,
const vector<VA> &jmptable_entries,
raw_ostream &out)
{
// first, find which operand was the index
// register in jmpinst
//
const MCInst &inst = jmpinst->get_inst();
int index_reg = regFromInst(inst);
if(index_reg == -1) {
out << "JMPINST does not use a register to index\n";
return false;
}
// loop backwards through block looking for
// instructions that write to this register
const std::list<InstPtr> &block_insts = B->get_insts();
InstPtr write_reg_insn;
for( std::list<InstPtr>::const_reverse_iterator itr = block_insts.rbegin();
itr != block_insts.rend();
itr++)
{
// check if we 'write to a register'
if(writesToReg((*itr)->get_inst(), index_reg)) {
write_reg_insn = *itr;
break;
}
}
if(write_reg_insn == NULL) {
out << "No instruction writes index register in the same basic block\n";
return false;
}
out << "Found register index write instruction:\n";
if(!parseJumpIndexTable(c, write_reg_insn,
jmptable_entries, out)) {
out << "Could not parse jump index table, aborting\n";
return false;
}
return true;
}
static bool canInstructionReferenceCode( InstPtr inst) {
switch(inst->get_inst().getOpcode()) {
case X86::MOV32mi: // writes to memory, but uses an immediate, which could be code
case X86::MOV32o32a: // writes imm32 to eax; probably code
case X86::MOV32ri: // writes imm32 to register, could be code
case X86::PUSHi32: // push an imm32, which could be code
// need to check if mem references are valid here
case X86::MOV32rm: // writes mem to register, mem could be code?
case X86::PUSH32rmm: // push mem, which could be/have code
//case X86::LEA32r: // write address of mem to reg
return true;
default:
return false;
}
}
NativeBlockPtr decodeBlock( ExecutableContainer *c,
ExternalFunctionMap &f,
LLVMByteDecoder &d,
stack<VA> &blockChildren,
VA e,
stack<VA> &funcs,
raw_ostream &out)
{
NativeBlockPtr B = NativeBlockPtr(new NativeBlock(e, d.getPrinter()));
VA curAddr = e;
bool has_follow = true;
out << "Processing block: " << B->get_name() << "\n";
do
{
InstPtr I = d.getInstFromBuff(curAddr, c);
//I, if a terminator, will have true and false targets
//filled in. I could be an indirect branch of some kind,
//we will deal with that here. we will also deal with the
//instruction if it is a data instruction with relocation
out << to_string<VA>(I->get_loc(), hex) << ":";
out << I->printInst() << "\n";
if(I->get_tr() != 0) {
B->add_follow(I->get_tr());
has_follow = false;
out << "Adding block: " << to_string<VA>(I->get_tr(), hex) << "\n";
blockChildren.push(I->get_tr());
}
if(I->get_fa() != 0) {
B->add_follow(I->get_fa());
has_follow = false;
out << "Adding block: " << to_string<VA>(I->get_fa(), hex) << "\n";
blockChildren.push(I->get_fa());
}
if(I->terminator()) {
has_follow = false;
}
//do we need to add a data reference to this instruction?
//again, because there is no offset information in the
//instruction decoder, for now we just ask if every addr
//in the inst is relocated
for(uint32_t i = 0; i < I->get_len(); i++) {
VA addrInInst = curAddr+i;
if(c->is_addr_relocated(addrInInst)) {
VA addr = 0;
std::string has_imp;
// this instruction has a relocation
// save the relocation offset for later
I->set_reloc_offset(i);
//get the offset for this address
//add it as a data offset to the instruction
if (c->find_import_name(addrInInst, has_imp) ) {
if(f.is_data(has_imp))
{
ExternalDataRefPtr data_p = makeExtDataRefFromString(has_imp, f);
out << "Adding external data ref: " << has_imp << "\n";
I->set_ext_data_ref(data_p);
}
else
{
ExternalCodeRefPtr code_p = makeExtCodeRefFromString(has_imp, f);
LASSERT(code_p, "Failed to get ext call from map for symbol: "+has_imp);
//maybe, this call doesn't return, in which case,
//we should kill the decoding of this flow
if(code_p->getReturnType() == ExternalCodeRef::NoReturn) {
has_follow = false;
}
out << "Adding external code ref: " << has_imp << "\n";
I->set_ext_call_target(code_p);
}
} else if(c->relocate_addr(addrInInst, addr)) {
bool can_ref_code = canInstructionReferenceCode(I);
bool is_reloc_code = isAddrOfType(c, addr, ExecutableContainer::CodeSection);
bool is_reloc_data = isAddrOfType(c, addr, ExecutableContainer::DataSection);
unsigned opc = I->get_inst().getOpcode();
if(isBranchViaMemory(I)) {
out << "Detect branch via memory, relocation handled later\n";
}
// this instruction can reference code and does
// reference code
// so we assume the code points to a function
else if( can_ref_code && is_reloc_code ) {
list<VA> new_funcs;
if(dataInCodeHeuristic(c, I, addr, new_funcs)) {
// add new functions to our functions list
for(list<VA>::const_iterator nfi = new_funcs.begin();
nfi != new_funcs.end();
nfi++)
{
funcs.push(*nfi);
}
I->set_data_offset(addr);
} else {
I->set_call_tgt(addr);
out << "Adding: 0x" << to_string<VA>(addr, hex) << " as target\n";
funcs.push(addr);
}
}
// this instruction can't reference code and points to .text
// or references data. Treat as data element
// TODO: extract this from .text and shove into .data?
else if(( !can_ref_code && is_reloc_code) || is_reloc_data )
{
I->set_data_offset(addr);
} else {
out << "WARNING: relocation points to neither code nor data:" << to_string<VA>(addr, hex) << "\n";
}
} else {
out << "*NOT* Relocating relocatable addr:" << to_string<uint32_t>(addrInInst, hex) << "\n";
}
break;
}
}
//is this instruction an external call?
//in a COFF binary, the pcrel call can refer to an
//external symbol that has been relocated
//so, get the string that corresponds, and
//provide the translation using the function map
MCOperand op;
string imp;
switch(I->get_inst().getOpcode()) {
case X86::JMP32m:
{
string thunkSym;
bool r = c->find_import_name(curAddr+2, thunkSym);
if(r) {
// this goes to an external API call
out << "Adding external code ref via JMP: " << thunkSym << "\n";
ExternalCodeRefPtr p = makeExtCodeRefFromString(thunkSym, f);
I->set_ext_call_target(p);
has_follow = false;
} else {
// this is an internal jmp. probably a jump table.
bool did_jmptable = handlePossibleJumpTable(c, B, I, curAddr, funcs, blockChildren, out);
LASSERT(did_jmptable, "JMP32m processing aborted: couldn't parse jumptable");
}
}
break;
case X86::CALLpcrel32:
//this could be an external call in COFF, or not
op = I->get_inst().getOperand(0);
LASSERT(op.isImm(), "Nonsense for CALLpcrel32");
if(op.getImm() !=0) {
VA callTgt = curAddr+op.getImm()+I->get_len();
bool foldFunc = false;
//speculate about callTgt
InstPtr spec = d.getInstFromBuff(callTgt, c);
if(spec->terminator() && spec->get_inst().getOpcode() == X86::JMP32m) {
string thunkSym;
bool r = c->find_import_name(callTgt+2, thunkSym);
LASSERT(r, "Need to find thunk import addr");
ExternalCodeRefPtr p = makeExtCodeRefFromString(thunkSym, f);
I->set_ext_call_target(p);
foldFunc = true;
if(p->getReturnType() == ExternalCodeRef::NoReturn) {
has_follow = false;
}
}
if(foldFunc == false) {
//add this to our list of funcs to search
funcs.push(callTgt);
}
} else {
//check to see if this is an external call...
if(I->has_ext_call_target() == false) {
// may be a local call
VA addr=curAddr+1, relo_addr=0;
out << "Symbol not found, maybe a local call\n";
if(c->relocate_addr(addr, relo_addr)){
out << "Found local call to: " << to_string<VA>(relo_addr, hex) << "\n";
I->set_call_tgt(relo_addr);
out << "Adding: 0x" << to_string<VA>(relo_addr, hex) << " as target\n";
funcs.push(relo_addr);
} else {
out << "Could not relocate addr for local call at: ";
out << to_string<VA>(curAddr, hex) << "\n";
}
} else {
out << "External call to: " << I->get_ext_call_target()->getSymbolName() << "\n";
}
}
break;
case X86::CALL32m:
//this should be a call to an external, or we have no idea
//so we need to try and look up the symbol that we're calling at this address...
if(c->find_import_name(curAddr+2, imp)) {
ExternalCodeRefPtr p = makeExtCodeRefFromString(imp, f);
LASSERT(p, "Failed to get ext call from map for symbol"+imp);
out << "Calling symbol: " << p->getSymbolName() << "\n";
if(p->getReturnType() == ExternalCodeRef::NoReturn) {
has_follow = false;
}
I->set_ext_call_target(p);
} else {
out << "Cannot find symbol at address ";
out << to_string<VA>(curAddr, hex) << "\n";
}
break;
}
B->add_inst(I);
curAddr += I->get_len();
} while(has_follow);
//we have built a basic block, it might contain
//multiple calls, but it only has one terminator
//which is either a ret or a branch
return B;
}
static bool handlePossibleJumpTable(ExecutableContainer *c,
NativeBlockPtr B,
InstPtr jmpinst,
VA curAddr,
stack<VA> &funcs,
stack<VA> &blockChildren,
raw_ostream &out) {
LASSERT(jmpinst->get_inst().getOpcode() == X86::JMP32m,
"handlePossibleJumpTable needs a JMP32m opcode" );
// is this a jump table, step 0
// does this instruction have a relocation?
VA reloc_offset = jmpinst->get_reloc_offset();
if (reloc_offset == 0) {
out << "Not a jump table: no relocation in JMP32m\n";
// bail, this is not a jump table
return false;
}
// this relocation has to point to a relocation
VA addrInInst = curAddr + reloc_offset;
VA jmpTableEntry, someFunction;
if(!c->relocate_addr(addrInInst, jmpTableEntry)) {
out << "Not a jump table: can't relocate relocation in JMP32m\n";
// can't relocate, something bad happened
return false;
}
if(!c->relocate_addr(jmpTableEntry, someFunction)) {
// could not relocate the default jump table entry.
// not good
out << "Not a jump table: can't relocate first jump table entry\n";
return false;
}
bool is_reloc_code = isAddrOfType(c, someFunction, ExecutableContainer::CodeSection);
if(!is_reloc_code) {
// jump table entry not point to code
out << "Not a jump table: first entry doesn't point to code\n";
return false;
}
// read jump table entries and add them as new function
// entry points
vector<VA> jmptable_entries;
int new_funs;
int original_zero;
// this reads negative jump table indexes, but vectors are not negative
// indexed. the negative most, which should be the new index 0, is now
// index N. Reverse the vector so it will be index 0, and save the current
// size as the original zeroth element
new_funs = addJmpTableEntries(c, jmptable_entries, jmpTableEntry, -4, out);
std::reverse(jmptable_entries.begin(), jmptable_entries.end());
out << "Added: " << to_string<int>(new_funs, dec) << " functions to jmptable\n";
original_zero = new_funs;
// add original entry at the zero position
jmptable_entries.push_back(someFunction);
out << "Added JMPTABLE entry [" << to_string<uint32_t>(jmpTableEntry, hex)
<< "] => " << to_string<uint32_t>(someFunction, hex) << "\n";
// add the positive table entries
new_funs = addJmpTableEntries(c, jmptable_entries, jmpTableEntry, 4, out);
out << "Added: " << to_string<int>(new_funs, dec) << " functions to jmptable\n";
// associate instruction with jump table
JumpTable *jt = new JumpTable(jmptable_entries, original_zero);
jmpinst->set_jump_table(JumpTablePtr(jt));
stack<VA> *toPush = NULL;
// if this jump table is in the format
// jmp [reg*4+imm32], then it is conformant
// and we can turn it into an llvm switch();
bool is_conformant = isConformantJumpInst(jmpinst);
if(is_conformant) {
toPush = &blockChildren;
out << "GOT A CONFORMANT JUMP INST\n";
} else {
toPush = &funcs;
}
// add these jump table entries as new entry points
for(std::vector<VA>::const_iterator itr = jmptable_entries.begin();
itr != jmptable_entries.end();
itr++)
{
out << "Adding block via jmptable: " << to_string<VA>(*itr, hex) << "\n";
toPush->push(*itr);
if(is_conformant) {
B->add_follow(*itr);
}
}
processJumpIndexTable(c, B, jmpinst, jmptable_entries, out);
return true;
}
