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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
Patch Set: Improve rel32_finder doc Created 4 years, 6 months ago
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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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