1 // Copyright 2018 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 #ifndef COMPONENTS_ZUCCHINI_RELOC_ELF_H_
6 #define COMPONENTS_ZUCCHINI_RELOC_ELF_H_
7 
8 #include <stddef.h>
9 #include <stdint.h>
10 
11 #include <optional>
12 #include <vector>
13 
14 #include "base/numerics/safe_conversions.h"
15 #include "components/zucchini/address_translator.h"
16 #include "components/zucchini/buffer_view.h"
17 #include "components/zucchini/image_utils.h"
18 #include "components/zucchini/type_elf.h"
19 
20 namespace zucchini {
21 
22 // Section dimensions for ELF files, to store relevant dimensions data from
23 // Elf32_Shdr and Elf64_Shdr, while reducing code duplication from templates.
24 struct SectionDimensionsElf {
25   SectionDimensionsElf() = default;
26 
27   template <class Elf_Shdr>
SectionDimensionsElfSectionDimensionsElf28   explicit SectionDimensionsElf(const Elf_Shdr& section)
29       : region(BufferRegion{base::checked_cast<size_t>(section.sh_offset),
30                             base::checked_cast<size_t>(section.sh_size)}),
31         entry_size(base::checked_cast<offset_t>(section.sh_entsize)) {}
32 
33   friend bool operator<(const SectionDimensionsElf& a,
34                         const SectionDimensionsElf& b) {
35     return a.region.offset < b.region.offset;
36   }
37 
38   friend bool operator<(offset_t offset, const SectionDimensionsElf& section) {
39     return offset < section.region.offset;
40   }
41 
42   BufferRegion region;
43   offset_t entry_size;  // Varies across REL / RELA sections.
44 };
45 
46 // A Generator to visit all reloc structs located in [|lo|, |hi|) (excluding
47 // truncated strct at |lo| but inlcuding truncated struct at |hi|), and emit
48 // valid References with |rel_type|. This implements a nested loop unrolled into
49 // a generator: the outer loop has |cur_section_dimensions_| visiting
50 // |reloc_section_dims| (sorted by |region.offset|), and the inner loop has
51 // |cursor_| visiting successive reloc structs within |cur_section_dimensions_|.
52 class RelocReaderElf : public ReferenceReader {
53  public:
54   RelocReaderElf(
55       ConstBufferView image,
56       Bitness bitness,
57       const std::vector<SectionDimensionsElf>& reloc_section_dimensions,
58       uint32_t rel_type,
59       offset_t lo,
60       offset_t hi,
61       const AddressTranslator& translator);
62   ~RelocReaderElf() override;
63 
64   // If |rel| contains |r_offset| for |rel_type_|, return the RVA. Otherwise
65   // return |kInvalidRva|. These also handle Elf*_Rela, by using the fact that
66   // Elf*_Rel is a prefix of Elf*_Rela.
67   rva_t GetRelocationTarget(elf::Elf32_Rel rel) const;
68   rva_t GetRelocationTarget(elf::Elf64_Rel rel) const;
69 
70   // ReferenceReader:
71   std::optional<Reference> GetNext() override;
72 
73  private:
74   const ConstBufferView image_;
75   const Bitness bitness_;
76   const uint32_t rel_type_;
77   const std::vector<SectionDimensionsElf>& reloc_section_dimensions_;
78   std::vector<SectionDimensionsElf>::const_iterator cur_section_dimensions_;
79   offset_t hi_;
80   offset_t cursor_;
81   AddressTranslator::RvaToOffsetCache target_rva_to_offset_;
82 };
83 
84 class RelocWriterElf : public ReferenceWriter {
85  public:
86   RelocWriterElf(MutableBufferView image,
87                  Bitness bitness,
88                  const AddressTranslator& translator);
89   ~RelocWriterElf() override;
90 
91   // ReferenceWriter:
92   void PutNext(Reference ref) override;
93 
94  private:
95   MutableBufferView image_;
96   const Bitness bitness_;
97   AddressTranslator::OffsetToRvaCache target_offset_to_rva_;
98 };
99 
100 }  // namespace zucchini
101 
102 #endif  // COMPONENTS_ZUCCHINI_RELOC_ELF_H_
103