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// Copyright 2017 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifdef UNSAFE_BUFFERS_BUILD
// TODO(crbug.com/40285824): Remove this and convert code to safer constructs.
#pragma allow_unsafe_buffers
#endif
#include "components/zucchini/reloc_win32.h"
#include <algorithm>
#include <tuple>
#include <utility>
#include "base/logging.h"
#include "base/numerics/safe_conversions.h"
#include "components/zucchini/algorithm.h"
#include "components/zucchini/io_utils.h"
#include "components/zucchini/type_win_pe.h"
namespace zucchini {
/******** RelocUnitWin32 ********/
RelocUnitWin32::RelocUnitWin32() = default;
RelocUnitWin32::RelocUnitWin32(uint8_t type_in,
offset_t location_in,
rva_t target_rva_in)
: type(type_in), location(location_in), target_rva(target_rva_in) {}
bool operator==(const RelocUnitWin32& a, const RelocUnitWin32& b) {
return std::tie(a.type, a.location, a.target_rva) ==
std::tie(b.type, b.location, b.target_rva);
}
/******** RelocRvaReaderWin32 ********/
// static
bool RelocRvaReaderWin32::FindRelocBlocks(
ConstBufferView image,
BufferRegion reloc_region,
std::vector<offset_t>* reloc_block_offsets) {
CHECK_LT(reloc_region.size, kOffsetBound);
ConstBufferView reloc_data = image[reloc_region];
reloc_block_offsets->clear();
while (reloc_data.size() >= sizeof(pe::RelocHeader)) {
reloc_block_offsets->push_back(
base::checked_cast<offset_t>(reloc_data.begin() - image.begin()));
auto size = reloc_data.read<pe::RelocHeader>(0).size;
// |size| must be aligned to 4-bytes.
if (size < sizeof(pe::RelocHeader) || size % 4 || size > reloc_data.size())
return false;
reloc_data.remove_prefix(size);
}
return reloc_data.empty(); // Fail if trailing data exist.
}
RelocRvaReaderWin32::RelocRvaReaderWin32(
ConstBufferView image,
BufferRegion reloc_region,
const std::vector<offset_t>& reloc_block_offsets,
offset_t lo,
offset_t hi)
: image_(image) {
CHECK_LE(lo, hi);
lo = base::checked_cast<offset_t>(reloc_region.InclusiveClamp(lo));
hi = base::checked_cast<offset_t>(reloc_region.InclusiveClamp(hi));
end_it_ = image_.begin() + hi;
// By default, get GetNext() to produce empty output.
cur_reloc_units_ = BufferSource(end_it_, 0);
if (reloc_block_offsets.empty())
return;
// Find the block that contains |lo|.
auto block_it = std::upper_bound(reloc_block_offsets.begin(),
reloc_block_offsets.end(), lo);
DCHECK(block_it != reloc_block_offsets.begin());
--block_it;
// Initialize |cur_reloc_units_| and |rva_hi_bits_|.
if (!LoadRelocBlock(image_.begin() + *block_it))
return; // Nothing left.
// Skip |cur_reloc_units_| to |lo|, truncating up.
offset_t cur_reloc_units_offset =
base::checked_cast<offset_t>(cur_reloc_units_.begin() - image_.begin());
if (lo > cur_reloc_units_offset) {
offset_t delta =
AlignCeil<offset_t>(lo - cur_reloc_units_offset, kRelocUnitSize);
// Okay if this empties |cur_reloc_units_|.
cur_reloc_units_.Skip(delta);
}
}
RelocRvaReaderWin32::RelocRvaReaderWin32(RelocRvaReaderWin32&&) = default;
RelocRvaReaderWin32::~RelocRvaReaderWin32() = default;
// Unrolls a nested loop: outer = reloc blocks and inner = reloc entries.
std::optional<RelocUnitWin32> RelocRvaReaderWin32::GetNext() {
// "Outer loop" to find non-empty reloc block.
while (cur_reloc_units_.Remaining() < kRelocUnitSize) {
if (!LoadRelocBlock(cur_reloc_units_.end()))
return std::nullopt;
}
if (end_it_ - cur_reloc_units_.begin() < kRelocUnitSize)
return std::nullopt;
// "Inner loop" to extract single reloc unit.
offset_t location =
base::checked_cast<offset_t>(cur_reloc_units_.begin() - image_.begin());
uint16_t entry = cur_reloc_units_.read<uint16_t>(0);
uint8_t type = static_cast<uint8_t>(entry >> 12);
rva_t rva = rva_hi_bits_ + (entry & 0xFFF);
if (!cur_reloc_units_.Skip(kRelocUnitSize)) {
return std::nullopt;
}
return RelocUnitWin32{type, location, rva};
}
bool RelocRvaReaderWin32::LoadRelocBlock(
ConstBufferView::const_iterator block_begin) {
ConstBufferView header_buf(block_begin, sizeof(pe::RelocHeader));
if (header_buf.end() >= end_it_ ||
end_it_ - header_buf.end() < kRelocUnitSize) {
return false;
}
const auto& header = header_buf.read<pe::RelocHeader>(0);
rva_hi_bits_ = header.rva_hi;
uint32_t block_size = header.size;
if (block_size < sizeof(pe::RelocHeader))
return false;
if ((block_size - sizeof(pe::RelocHeader)) % kRelocUnitSize != 0)
return false;
cur_reloc_units_ = BufferSource(block_begin, block_size);
cur_reloc_units_.Skip(sizeof(pe::RelocHeader)); // Always succeeds.
return true;
}
/******** RelocReaderWin32 ********/
RelocReaderWin32::RelocReaderWin32(RelocRvaReaderWin32&& reloc_rva_reader,
uint16_t reloc_type,
offset_t offset_bound,
const AddressTranslator& translator)
: reloc_rva_reader_(std::move(reloc_rva_reader)),
reloc_type_(reloc_type),
offset_bound_(offset_bound),
entry_rva_to_offset_(translator) {}
RelocReaderWin32::~RelocReaderWin32() = default;
// ReferenceReader:
std::optional<Reference> RelocReaderWin32::GetNext() {
for (std::optional<RelocUnitWin32> unit = reloc_rva_reader_.GetNext();
unit.has_value(); unit = reloc_rva_reader_.GetNext()) {
if (unit->type != reloc_type_)
continue;
offset_t target = entry_rva_to_offset_.Convert(unit->target_rva);
if (target == kInvalidOffset)
continue;
// Ensure that |target| (abs32 reference) lies entirely within the image.
if (target >= offset_bound_)
continue;
offset_t location = unit->location;
return Reference{location, target};
}
return std::nullopt;
}
/******** RelocWriterWin32 ********/
RelocWriterWin32::RelocWriterWin32(
uint16_t reloc_type,
MutableBufferView image,
BufferRegion reloc_region,
const std::vector<offset_t>& reloc_block_offsets,
const AddressTranslator& translator)
: reloc_type_(reloc_type),
image_(image),
reloc_region_(reloc_region),
reloc_block_offsets_(reloc_block_offsets),
target_offset_to_rva_(translator) {}
RelocWriterWin32::~RelocWriterWin32() = default;
void RelocWriterWin32::PutNext(Reference ref) {
DCHECK_GE(ref.location, reloc_region_.lo());
DCHECK_LT(ref.location, reloc_region_.hi());
auto block_it = std::upper_bound(reloc_block_offsets_->begin(),
reloc_block_offsets_->end(), ref.location);
--block_it;
rva_t rva_hi_bits = image_.read<pe::RelocHeader>(*block_it).rva_hi;
rva_t target_rva = target_offset_to_rva_.Convert(ref.target);
rva_t rva_lo_bits = (target_rva - rva_hi_bits) & 0xFFF;
if (target_rva != rva_hi_bits + rva_lo_bits) {
LOG(ERROR) << "Invalid RVA at " << AsHex<8>(ref.location) << ".";
return;
}
image_.write<uint16_t>(ref.location, rva_lo_bits | (reloc_type_ << 12));
}
} // namespace zucchini
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