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| 1 // Copyright 2015 The Chromium Authors. All rights reserved. | |
| 2 // Use of this source code is governed by a BSD-style license that can be | |
| 3 // found in the LICENSE file. | |
| 4 | |
| 5 #include <stdint.h> | |
| 6 | |
| 7 #include "courgette/rel32_finder_win32_x86.h" | |
| 8 | |
| 9 namespace courgette { | |
| 10 | |
| 11 Rel32FinderWin32X86::Rel32FinderWin32X86(RVA relocs_start_rva, | |
| 12 RVA relocs_end_rva) | |
| 13 : relocs_start_rva_(relocs_start_rva), relocs_end_rva_(relocs_end_rva) { | |
| 14 } | |
| 15 | |
| 16 Rel32FinderWin32X86::~Rel32FinderWin32X86() { | |
| 17 } | |
| 18 | |
| 19 void Rel32FinderWin32X86::SwapRel32Locations(std::vector<RVA>* dest) { | |
| 20 dest->swap(rel32_locations_); | |
| 21 } | |
| 22 | |
| 23 #if COURGETTE_HISTOGRAM_TARGETS | |
| 24 void Rel32FinderWin32X86::SwapRel32TargetRVAs(std::map<RVA, int>* dest) { | |
| 25 dest->swap(rel32_target_rvas_); | |
| 26 } | |
| 27 #endif | |
| 28 | |
| 29 Rel32FinderWin32X86_Basic::Rel32FinderWin32X86_Basic(RVA relocs_start_rva, | |
| 30 RVA relocs_end_rva) | |
| 31 : Rel32FinderWin32X86(relocs_start_rva, relocs_end_rva) { | |
| 32 } | |
| 33 | |
| 34 Rel32FinderWin32X86_Basic::~Rel32FinderWin32X86_Basic() { | |
| 35 } | |
| 36 | |
| 37 void Rel32FinderWin32X86_Basic::Find(const uint8_t* start_pointer, | |
| 38 const uint8_t* end_pointer, | |
| 39 RVA start_rva, | |
| 40 RVA end_rva, | |
| 41 const std::vector<RVA>& abs32_locations) { | |
| 42 // Quick way to convert from Pointer to RVA within a single Section is to | |
| 43 // subtract 'pointer_to_rva'. | |
| 44 const uint8_t* const adjust_pointer_to_rva = start_pointer - start_rva; | |
| 45 | |
| 46 std::vector<RVA>::const_iterator abs32_pos = abs32_locations.begin(); | |
| 47 | |
| 48 // Find the rel32 relocations. | |
| 49 const uint8_t* p = start_pointer; | |
| 50 while (p < end_pointer) { | |
| 51 RVA current_rva = static_cast<RVA>(p - adjust_pointer_to_rva); | |
| 52 | |
| 53 // Skip the base reloation table if we encounter it. | |
| 54 // Note: We're not bothering to handle the edge case where a Rel32 pointer | |
| 55 // collides with |relocs_start_rva_| by being {1, 2, 3}-bytes before it. | |
| 56 if (current_rva == relocs_start_rva_) { | |
| 57 if (relocs_start_rva_ < relocs_end_rva_) { | |
| 58 p += relocs_end_rva_ - relocs_start_rva_; | |
| 59 continue; | |
| 60 } | |
| 61 } | |
| 62 | |
| 63 // Heuristic discovery of rel32 locations in instruction stream: are the | |
| 64 // next few bytes the start of an instruction containing a rel32 | |
| 65 // addressing mode? | |
| 66 const uint8_t* rel32 = nullptr; | |
| 67 | |
| 68 if (p + 5 <= end_pointer) { | |
| 69 if (*p == 0xE8 || *p == 0xE9) { // jmp rel32 and call rel32 | |
| 70 rel32 = p + 1; | |
| 71 } | |
| 72 } | |
| 73 if (p + 6 <= end_pointer) { | |
| 74 if (*p == 0x0F && (*(p+1) & 0xF0) == 0x80) { // Jcc long form | |
| 75 if (p[1] != 0x8A && p[1] != 0x8B) // JPE/JPO unlikely | |
| 76 rel32 = p + 2; | |
| 77 } | |
| 78 } | |
| 79 if (rel32) { | |
| 80 RVA rel32_rva = static_cast<RVA>(rel32 - adjust_pointer_to_rva); | |
| 81 | |
| 82 // Is there an abs32 reloc overlapping the candidate? | |
| 83 while (abs32_pos != abs32_locations.end() && *abs32_pos < rel32_rva - 3) | |
| 84 ++abs32_pos; | |
| 85 // Now: (*abs32_pos > rel32_rva - 4) i.e. the lowest addressed 4-byte | |
| 86 // region that could overlap rel32_rva. | |
| 87 if (abs32_pos != abs32_locations.end()) { | |
| 88 if (*abs32_pos < rel32_rva + 4) { | |
| 89 // Beginning of abs32 reloc is before end of rel32 reloc so they | |
| 90 // overlap. Skip four bytes past the abs32 reloc. | |
| 91 p += (*abs32_pos + 4) - current_rva; | |
| 92 continue; | |
| 93 } | |
| 94 } | |
| 95 | |
| 96 // + 4 since offset is relative to start of next instruction. | |
| 97 RVA target_rva = rel32_rva + 4 + Read32LittleEndian(rel32); | |
| 98 // Valid, rel32 target must be within image, and within this section. | |
| 99 // Subsumes |target_rva| != |kUnassignedRVA|. | |
| 100 if (start_rva <= target_rva && target_rva < end_rva) { | |
| 101 rel32_locations_.push_back(rel32_rva); | |
| 102 #if COURGETTE_HISTOGRAM_TARGETS | |
| 103 ++rel32_target_rvas_[target_rva]; | |
| 104 #endif | |
| 105 p = rel32 + 4; | |
| 106 continue; | |
| 107 } | |
| 108 } | |
| 109 p += 1; | |
| 110 } | |
| 111 } | |
| 112 | |
| 113 } // namespace courgette | |
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Chromium Code Reviews
Issue 2008253004:
Refactor rel32 searching process for x64 to make it more similar to x86. (Closed)
Base URL: https://chromium.googlesource.com/chromium/src.git@master