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Clone metadata when moving stuff #530

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Jun 30, 2021
Merged

Clone metadata when moving stuff #530

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4 changes: 3 additions & 1 deletion include/remill/BC/Util.h
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Original file line number Diff line number Diff line change
Expand Up @@ -50,6 +50,7 @@ class FunctionType;
class GlobalObject;
class GlobalVariable;
class IntegerType;
class Metadata;
class Module;
class PointerType;
class Type;
Expand Down Expand Up @@ -222,6 +223,7 @@ llvm::IntegerType *AddressType(llvm::Module *module)
__attribute__((deprecated));

using ValueMap = std::unordered_map<llvm::Value *, llvm::Value *>;
using MDMap = std::unordered_map<llvm::Metadata *, llvm::Metadata *>;

// Clone function `source_func` into `dest_func`, using `value_map` to map over
// values. This will strip out debug info during the clone. This will strip out
Expand All @@ -230,7 +232,7 @@ using ValueMap = std::unordered_map<llvm::Value *, llvm::Value *>;
// Note: this will try to clone globals referenced from the module of
// `source_func` into the module of `dest_func`.
void CloneFunctionInto(llvm::Function *source_func, llvm::Function *dest_func,
ValueMap &value_map);
ValueMap &value_map, MDMap &md_map);

// Clone function `source_func` into `dest_func`. This will strip out debug
// info during the clone.
Expand Down
135 changes: 117 additions & 18 deletions lib/BC/Util.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -676,6 +676,7 @@ llvm::IntegerType *AddressType(llvm::Module *module) {
void CloneFunctionInto(llvm::Function *source_func, llvm::Function *dest_func) {
auto new_args = dest_func->arg_begin();
ValueMap value_map;
MDMap md_map;
for (llvm::Argument &old_arg : source_func->args()) {
new_args->setName(old_arg.getName());
value_map[&old_arg] = &*new_args;
Expand All @@ -686,7 +687,7 @@ void CloneFunctionInto(llvm::Function *source_func, llvm::Function *dest_func) {
dest_func->getContext()),
dest_func->getFunctionType());

CloneFunctionInto(source_func, dest_func, value_map);
CloneFunctionInto(source_func, dest_func, value_map, md_map);
}

// Make `func` a clone of the `__remill_basic_block` function.
Expand Down Expand Up @@ -1389,6 +1390,65 @@ static void MoveInstructionIntoModule(llvm::Instruction *inst,
}
}

llvm::Metadata *CloneMetadataInto(
llvm::Module *source_mod, llvm::Module *dest_mod,
llvm::Metadata *md, ValueMap &value_map, MDMap &md_map) {

llvm::Metadata *mapped_md = nullptr;
auto [it, added] = md_map.emplace(md, mapped_md);
if (!added) {
return it->second;
}

llvm::LLVMContext &source_context = source_mod->getContext();
llvm::LLVMContext &dest_context = dest_mod->getContext();

if (llvm::ValueAsMetadata *val_md = llvm::dyn_cast<llvm::ValueAsMetadata>(md)) {
llvm::Value *val = val_md->getValue();
if (auto it = value_map.find(val); it != value_map.end()) {
llvm::Value *mapped_val = it->second;
mapped_md = llvm::ValueAsMetadata::get(mapped_val);

} else if (auto cv = llvm::dyn_cast<llvm::Constant>(val)) {
llvm::Value *mapped_cv = MoveConstantIntoModule(cv, dest_mod, value_map);
if (!mapped_cv) {
return nullptr; // Couldn't move it.
}
mapped_md = llvm::ValueAsMetadata::get(mapped_cv);

} else {
return nullptr;
}

} else if (llvm::MDString *str = llvm::dyn_cast<llvm::MDString>(md)) {
if (&source_context == &dest_context) {
mapped_md = str;
} else {
mapped_md = llvm::MDString::get(dest_context, str->getString());
}

} else if (llvm::MDTuple *tuple = llvm::dyn_cast<llvm::MDTuple>(md)) {
std::vector<llvm::Metadata *> mapped_ops;
for (llvm::Metadata *op : tuple->operands()) {
auto mapped_op = CloneMetadataInto(source_mod, dest_mod, op, value_map,
md_map);
if (!mapped_op) {
return nullptr; // Possibly cyclic or just not clonable.
} else {
mapped_ops.push_back(mapped_op);
}
}
mapped_md = llvm::MDTuple::get(dest_context, mapped_ops);

// Not supported.
} else {
return nullptr;
}

it->second = mapped_md;
return mapped_md;
}

} // namespace

// Clone function `source_func` into `dest_func`, using `value_map` to map over
Expand All @@ -1398,7 +1458,7 @@ static void MoveInstructionIntoModule(llvm::Instruction *inst,
// Note: this will try to clone globals referenced from the module of
// `source_func` into the module of `dest_func`.
void CloneFunctionInto(llvm::Function *source_func, llvm::Function *dest_func,
ValueMap &value_map) {
ValueMap &value_map, MDMap &md_map) {

auto func_name = source_func->getName().str();
auto source_mod = source_func->getParent();
Expand Down Expand Up @@ -1447,26 +1507,69 @@ void CloneFunctionInto(llvm::Function *source_func, llvm::Function *dest_func,
// Fixup the references in the cloned instructions so that they point into
// the cloned function, or point to declared globals in the module containing
// `dest_func`.
for (auto &old_block : *source_func) {
for (auto &old_inst : old_block) {
for (llvm::BasicBlock &old_block : *source_func) {
for (llvm::Instruction &old_inst : old_block) {
if (llvm::isa<llvm::DbgInfoIntrinsic>(old_inst)) {
continue;
}

auto new_inst = llvm::dyn_cast<llvm::Instruction>(value_map[&old_inst]);
new_inst->setDebugLoc(llvm::DebugLoc());
new_inst->setName(old_inst.getName());

// Clear out all metadata from the new instruction.
MoveInstructionIntoModule(new_inst, dest_mod, value_map);
}
}

// NOTE(pag): All fixed MD kinds are part of the custom map, and are
// initialized into the context upon construction. There are about
// 40 of them.
llvm::SmallVector<llvm::StringRef, 64> source_md_names;

source_context.getMDKindNames(source_md_names);

std::unordered_map<unsigned, unsigned> md_id_map;
md_id_map.reserve(source_md_names.size());
for (auto i = 0u; i < source_md_names.size(); ++i) {
if (&source_context != &dest_context) {
md_id_map[i] = dest_context.getMDKindID(source_md_names[i]);
} else {
md_id_map[i] = i;
}
}

// Now port the metadata.
for (llvm::BasicBlock &old_block : *source_func) {
for (llvm::Instruction &old_inst : old_block) {
if (llvm::isa<llvm::DbgInfoIntrinsic>(old_inst)) {
continue;
}

llvm::Instruction *new_inst =
llvm::dyn_cast<llvm::Instruction>(value_map[&old_inst]);
if (!new_inst) {
continue;
}

mds.clear();
old_inst.getAllMetadata(mds);

// First, clear out the old metadata; the metadata IDs might not all
// align.
for (auto md_info : mds) {
if (md_info.first != reg_md_id || &source_context != &dest_context) {
new_inst->setMetadata(md_info.first, nullptr);
}
new_inst->setMetadata(md_info.first, nullptr);
}

new_inst->setDebugLoc(llvm::DebugLoc());
new_inst->setName(old_inst.getName());

MoveInstructionIntoModule(new_inst, dest_mod, value_map);
// Next, try to convert the metadata over, mapping metadata IDs along
// the way.
for (auto md_info : mds) {
llvm::MDNode *new_md = llvm::dyn_cast_or_null<llvm::MDNode>(
CloneMetadataInto(source_mod, dest_mod, md_info.second,
value_map, md_map));
if (new_md) {
new_inst->setMetadata(md_id_map[md_info.first], new_md);
}
}
}
}
}
Expand Down Expand Up @@ -1586,9 +1689,7 @@ void MoveFunctionIntoModule(llvm::Function *func, llvm::Module *dest_module) {
existing_decl_in_dest_module = nullptr;
}

if (!in_same_context) {
IF_LLVM_GTE_370(ClearMetaData(func);)
}
IF_LLVM_GTE_370(ClearMetaData(func);)

// Fill up the locals so that they map to themselves.
for (auto &arg : func->args()) {
Expand All @@ -1597,9 +1698,7 @@ void MoveFunctionIntoModule(llvm::Function *func, llvm::Module *dest_module) {
for (auto &block : *func) {
value_map.emplace(&block, &block);
for (auto &inst : block) {
if (!in_same_context) {
ClearMetaData(&inst);
}
ClearMetaData(&inst);
value_map.emplace(&inst, &inst);
}
}
Expand Down