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[decompiler] Support accessing 128-bit bitfields (#514)

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* support some 128-bit bitfield stuff

* fix bug

* support type stuff correctly
This commit is contained in:
water111
2021-05-21 20:36:04 -04:00
committed by GitHub
parent 6ac399ca33
commit 3fbdd662dc
14 changed files with 497 additions and 279 deletions
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decompiler/IR2/bitfields.cpp
+63 -3
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@@ -171,7 +171,9 @@ const BitField& find_field(const TypeSystem& ts,
std::optional<bool> looking_for_unsigned) {
for (auto& field : type->fields()) {
if (field.size() == size && field.offset() == start_bit) {
bool is_int = ts.tc(TypeSpec("integer"), field.type());
// the GOAL compiler sign extended floats.
bool is_int =
ts.tc(TypeSpec("integer"), field.type()) || ts.tc(TypeSpec("float"), field.type());
bool is_uint = ts.tc(TypeSpec("uinteger"), field.type());
// allow sign match, or unsigned+not a number.
@@ -182,6 +184,12 @@ const BitField& find_field(const TypeSystem& ts,
// matched!
return field;
}
// this is a hack to work around bad code where extracting the (pointer process)
// would sign extend the address.
if (!is_int && !is_uint && type->get_name() == "handle") {
return field;
}
} else {
return field;
}
@@ -286,6 +294,13 @@ std::optional<BitFieldDef> get_bitfield_initial_set(Form* form,
} // namespace
void BitfieldAccessElement::push_pcpyud() {
if (!m_steps.empty()) {
throw std::runtime_error("Unexpected pcpyud!");
}
m_got_pcpyud = true;
}
/*!
* Add a step to the bitfield access. If this completes the access, returns a form representing the
* access
@@ -294,6 +309,8 @@ FormElement* BitfieldAccessElement::push_step(const BitfieldManip step,
const TypeSystem& ts,
FormPool& pool,
const Env& env) {
int pcpyud_offset = m_got_pcpyud ? 64 : 0;
if (m_steps.empty() && step.kind == BitfieldManip::Kind::LEFT_SHIFT) {
// for left/right shift combo to get a field.
m_steps.push_back(step);
@@ -305,7 +322,38 @@ FormElement* BitfieldAccessElement::push_step(const BitfieldManip step,
bool is_unsigned = step.right_shift_unsigned();
int shift_size = step.get_shift_start_bit();
int size = shift_size - step.amount;
int start_bit = shift_size - size;
int start_bit = pcpyud_offset + shift_size - size;
auto type = ts.lookup_type(m_type);
auto as_bitfield = dynamic_cast<BitFieldType*>(type);
assert(as_bitfield);
auto field = find_field(ts, as_bitfield, start_bit, size, is_unsigned);
auto result =
pool.alloc_element<DerefElement>(m_base, false, DerefToken::make_field_name(field.name()));
result->inline_nested();
return result;
}
if (m_steps.empty() && step.kind == BitfieldManip::Kind::SLLV_SEXT) {
bool is_unsigned = false;
int size = 32;
int start_bit = 0 + pcpyud_offset;
auto type = ts.lookup_type(m_type);
auto as_bitfield = dynamic_cast<BitFieldType*>(type);
assert(as_bitfield);
auto field = find_field(ts, as_bitfield, start_bit, size, is_unsigned);
auto result =
pool.alloc_element<DerefElement>(m_base, false, DerefToken::make_field_name(field.name()));
result->inline_nested();
return result;
}
if (m_steps.empty() && step.kind == BitfieldManip::Kind::PEXTUW) {
if (m_got_pcpyud) {
throw std::runtime_error("unknown pcpyud PEXTUW sequence in bitfield");
}
bool is_unsigned = true;
int size = 32;
int start_bit = 64;
auto type = ts.lookup_type(m_type);
auto as_bitfield = dynamic_cast<BitFieldType*>(type);
assert(as_bitfield);
@@ -318,7 +366,7 @@ FormElement* BitfieldAccessElement::push_step(const BitfieldManip step,
if (m_steps.size() == 1 && m_steps.at(0).kind == BitfieldManip::Kind::LEFT_SHIFT) {
// second op in left/right shift combo
int end_bit = 64 - m_steps.at(0).amount;
int end_bit = pcpyud_offset + 64 - m_steps.at(0).amount;
if (!step.is_right_shift()) {
throw std::runtime_error("Unexpected step 1");
}
@@ -342,12 +390,18 @@ FormElement* BitfieldAccessElement::push_step(const BitfieldManip step,
if (m_steps.empty() && step.kind == BitfieldManip::Kind::LOGAND_WITH_CONSTANT_INT) {
// and with mask
if (m_got_pcpyud) {
throw std::runtime_error("unknown pcpyud LOGAND_WITH_CONSTANT_INT sequence in bitfield");
}
m_steps.push_back(step);
return nullptr;
}
if (m_steps.size() == 1 && m_steps.at(0).kind == BitfieldManip::Kind::LOGAND_WITH_CONSTANT_INT &&
step.kind == BitfieldManip::Kind::NONZERO_COMPARE) {
if (m_got_pcpyud) {
throw std::runtime_error("unknown pcpyud NONZERO_COMPARE sequence in bitfield");
}
auto type = ts.lookup_type(m_type);
auto as_bitfield = dynamic_cast<BitFieldType*>(type);
assert(as_bitfield);
@@ -364,6 +418,9 @@ FormElement* BitfieldAccessElement::push_step(const BitfieldManip step,
if (m_steps.size() == 1 && m_steps.at(0).kind == BitfieldManip::Kind::LOGAND_WITH_CONSTANT_INT &&
step.kind == BitfieldManip::Kind::LOGIOR_WITH_CONSTANT_INT) {
if (m_got_pcpyud) {
throw std::runtime_error("unknown pcpyud LOGIOR_WITH_CONSTANT_INT sequence in bitfield");
}
// this is setting a bitfield to a constant.
// first, let's check that the mask is used properly:
u64 mask = m_steps.at(0).amount;
@@ -399,6 +456,9 @@ FormElement* BitfieldAccessElement::push_step(const BitfieldManip step,
if (m_steps.size() == 1 && m_steps.at(0).kind == BitfieldManip::Kind::LOGAND_WITH_CONSTANT_INT &&
step.kind == BitfieldManip::Kind::LOGIOR_WITH_FORM) {
if (m_got_pcpyud) {
throw std::runtime_error("unknown pcpyud LOGIOR_WITH_FORM sequence in bitfield");
}
// this is setting a bitfield to a variable
u64 mask = m_steps.at(0).amount;