| // Copyright 2017 The Chromium Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #include "components/zucchini/rel32_finder.h" |
| |
| #include <algorithm> |
| |
| #include "base/numerics/safe_conversions.h" |
| |
| namespace zucchini { |
| |
| /******** Abs32GapFinder ********/ |
| |
| Abs32GapFinder::Abs32GapFinder(ConstBufferView image, |
| ConstBufferView region, |
| const std::vector<offset_t>& abs32_locations, |
| size_t abs32_width) |
| : base_(image.begin()), |
| region_end_(region.end()), |
| abs32_end_(abs32_locations.end()), |
| abs32_width_(abs32_width) { |
| DCHECK_GT(abs32_width, size_t(0)); |
| DCHECK_GE(region.begin(), image.begin()); |
| DCHECK_LE(region.end(), image.end()); |
| |
| const offset_t begin_offset = |
| base::checked_cast<offset_t>(region.begin() - image.begin()); |
| // Find the first |abs32_current_| with |*abs32_current_ >= begin_offset|. |
| abs32_current_ = std::lower_bound(abs32_locations.begin(), |
| abs32_locations.end(), begin_offset); |
| |
| // Find lower boundary, accounting for possibility that |abs32_current_[-1]| |
| // may straddle across |region.begin()|. |
| current_lo_ = region.begin(); |
| if (abs32_current_ > abs32_locations.begin()) { |
| current_lo_ = std::max(current_lo_, |
| image.begin() + abs32_current_[-1] + abs32_width_); |
| } |
| } |
| |
| Abs32GapFinder::~Abs32GapFinder() = default; |
| |
| base::Optional<ConstBufferView> Abs32GapFinder::GetNext() { |
| // Iterate over |[abs32_current_, abs32_end_)| and emit segments. |
| while (abs32_current_ != abs32_end_ && |
| base_ + *abs32_current_ < region_end_) { |
| ConstBufferView::const_iterator hi = base_ + *abs32_current_; |
| ConstBufferView gap = ConstBufferView::FromRange(current_lo_, hi); |
| current_lo_ = hi + abs32_width_; |
| ++abs32_current_; |
| if (!gap.empty()) |
| return gap; |
| } |
| // Emit final segment. |
| if (current_lo_ < region_end_) { |
| ConstBufferView gap = ConstBufferView::FromRange(current_lo_, region_end_); |
| current_lo_ = region_end_; |
| return gap; |
| } |
| return base::nullopt; |
| } |
| |
| /******** Rel32Finder ********/ |
| |
| Rel32Finder::Rel32Finder() {} |
| |
| Rel32Finder::~Rel32Finder() = default; |
| |
| void Rel32Finder::SetRegion(ConstBufferView region) { |
| region_ = region; |
| accept_it_ = region.begin(); |
| } |
| |
| bool Rel32Finder::FindNext() { |
| NextIterators next_iters = Scan(region_); |
| if (next_iters.reject == nullptr) { |
| region_.seek(region_.end()); |
| return false; |
| } |
| region_.seek(next_iters.reject); |
| accept_it_ = next_iters.accept; |
| DCHECK_GE(accept_it_, region_.begin()); |
| DCHECK_LE(accept_it_, region_.end()); |
| return true; |
| } |
| |
| void Rel32Finder::Accept() { |
| region_.seek(accept_it_); |
| } |
| |
| /******** Rel32FinderIntel ********/ |
| |
| Rel32Finder::NextIterators Rel32FinderIntel::SetResult( |
| ConstBufferView::const_iterator cursor, |
| uint32_t opcode_size, |
| bool can_point_outside_section) { |
| rel32_ = {cursor + opcode_size, can_point_outside_section}; |
| return {cursor + 1, cursor + (opcode_size + 4)}; |
| } |
| |
| /******** Rel32FinderX86 ********/ |
| |
| Rel32Finder::NextIterators Rel32FinderX86::Scan(ConstBufferView region) { |
| ConstBufferView::const_iterator cursor = region.begin(); |
| while (cursor < region.end()) { |
| // Heuristic rel32 detection by looking for opcodes that use them. |
| if (cursor + 5 <= region.end()) { |
| if (cursor[0] == 0xE8 || cursor[0] == 0xE9) // JMP rel32; CALL rel32 |
| return SetResult(cursor, 1, false); |
| } |
| if (cursor + 6 <= region.end()) { |
| if (cursor[0] == 0x0F && (cursor[1] & 0xF0) == 0x80) // Jcc long form |
| return SetResult(cursor, 2, false); |
| } |
| ++cursor; |
| } |
| return {nullptr, nullptr}; |
| } |
| |
| /******** Rel32FinderX64 ********/ |
| |
| Rel32Finder::NextIterators Rel32FinderX64::Scan(ConstBufferView region) { |
| ConstBufferView::const_iterator cursor = region.begin(); |
| while (cursor < region.end()) { |
| // Heuristic rel32 detection by looking for opcodes that use them. |
| if (cursor + 5 <= region.end()) { |
| if (cursor[0] == 0xE8 || cursor[0] == 0xE9) // JMP rel32; CALL rel32 |
| return SetResult(cursor, 1, false); |
| } |
| if (cursor + 6 <= region.end()) { |
| if (cursor[0] == 0x0F && (cursor[1] & 0xF0) == 0x80) { // Jcc long form |
| return SetResult(cursor, 2, false); |
| } else if ((cursor[0] == 0xFF && |
| (cursor[1] == 0x15 || cursor[1] == 0x25)) || |
| ((cursor[0] == 0x89 || cursor[0] == 0x8B || |
| cursor[0] == 0x8D) && |
| (cursor[1] & 0xC7) == 0x05)) { |
| // 6-byte instructions: |
| // [2-byte opcode] [disp32]: |
| // Opcode |
| // FF 15: CALL QWORD PTR [rip+disp32] |
| // FF 25: JMP QWORD PTR [rip+disp32] |
| // |
| // [1-byte opcode] [ModR/M] [disp32]: |
| // Opcode |
| // 89: MOV DWORD PTR [rip+disp32],reg |
| // 8B: MOV reg,DWORD PTR [rip+disp32] |
| // 8D: LEA reg,[rip+disp32] |
| // ModR/M : MMRRRMMM |
| // MM = 00 & MMM = 101 => rip+disp32 |
| // RRR: selects reg operand from [eax|ecx|...|edi] |
| return SetResult(cursor, 2, true); |
| } |
| } |
| ++cursor; |
| } |
| return {nullptr, nullptr}; |
| } |
| |
| } // namespace zucchini |