[Zucchini] Create elf types and utils.

Creates types and utility class to manipulate ELF header format and relocation
references.

BufferView: :modify() was also added.
Change-Id: Iacec212a2fb2f8a6c85d551eed4b8e0a84926d89
Reviewed-on: https://chromium-review.googlesource.com/1136846
Commit-Queue: Etienne Pierre-Doray <etiennep@chromium.org>
Reviewed-by: Greg Thompson <grt@chromium.org>
Reviewed-by: Samuel Huang <huangs@chromium.org>
Cr-Commit-Position: refs/heads/master@{#578034}
NOKEYCHECK=True
GitOrigin-RevId: 320f7d9d2cff9702e632af296867bf6ce7b14f8b

1 files changed, 102 insertions, 0 deletions

diff --git a/reloc_elf.h b/reloc_elf.h
new file mode 100644
index 0000000..1b5ba11
--- /dev/null
+++ b/reloc_elf.h
@@ -0,0 +1,102 @@
+// Copyright 2018 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.
+
+#ifndef COMPONENTS_ZUCCHINI_RELOC_ELF_H_
+#define COMPONENTS_ZUCCHINI_RELOC_ELF_H_
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include <vector>
+
+#include "base/optional.h"
+#include "components/zucchini/address_translator.h"
+#include "components/zucchini/buffer_source.h"
+#include "components/zucchini/buffer_view.h"
+#include "components/zucchini/image_utils.h"
+#include "components/zucchini/type_elf.h"
+
+namespace zucchini {
+
+// Section dimensions for ELF files, to store relevant dimensions data from
+// Elf32_Shdr and Elf64_Shdr, while reducing code duplication from templates.
+struct SectionDimensionsElf {
+  SectionDimensionsElf() = default;
+
+  template <class Elf_Shdr>
+  explicit SectionDimensionsElf(const Elf_Shdr& section)
+      : region(BufferRegion{base::checked_cast<size_t>(section.sh_offset),
+                            base::checked_cast<size_t>(section.sh_size)}),
+        entry_size(base::checked_cast<offset_t>(section.sh_entsize)) {}
+
+  friend bool operator<(const SectionDimensionsElf& a,
+                        const SectionDimensionsElf& b) {
+    return a.region.offset < b.region.offset;
+  }
+
+  friend bool operator<(offset_t offset, const SectionDimensionsElf& section) {
+    return offset < section.region.offset;
+  }
+
+  BufferRegion region;
+  offset_t entry_size;  // Varies across REL / RELA sections.
+};
+
+// A Generator to visit all reloc structs located in [|lo|, |hi|) (excluding
+// truncated strct at |lo| but inlcuding truncated struct at |hi|), and emit
+// valid References with |rel_type|. This implements a nested loop unrolled into
+// a generator: the outer loop has |cur_section_dimensions_| visiting
+// |reloc_section_dims| (sorted by |region.offset|), and the inner loop has
+// |cursor_| visiting successive reloc structs within |cur_section_dimensions_|.
+class RelocReaderElf : public ReferenceReader {
+ public:
+  RelocReaderElf(
+      ConstBufferView image,
+      Bitness bitness,
+      const std::vector<SectionDimensionsElf>& reloc_section_dimensions,
+      uint32_t rel_type,
+      offset_t lo,
+      offset_t hi,
+      const AddressTranslator& translator);
+  ~RelocReaderElf() override;
+
+  // If |rel| contains |r_offset| for |rel_type_|, return the RVA. Otherwise
+  // return |kInvalidRva|. These also handle Elf*_Rela, by using the fact that
+  // Elf*_Rel is a prefix of Elf*_Rela.
+  rva_t GetRelocationTarget(elf::Elf32_Rel rel) const;
+  rva_t GetRelocationTarget(elf::Elf64_Rel rel) const;
+
+  // ReferenceReader:
+  base::Optional<Reference> GetNext() override;
+
+ private:
+  const ConstBufferView image_;
+  const Bitness bitness_;
+  const uint32_t rel_type_;
+  const std::vector<SectionDimensionsElf>& reloc_section_dimensions_;
+  std::vector<SectionDimensionsElf>::const_iterator cur_section_dimensions_;
+  offset_t hi_;
+  offset_t cursor_;
+  AddressTranslator::RvaToOffsetCache target_rva_to_offset_;
+};
+
+class RelocWriterElf : public ReferenceWriter {
+ public:
+  RelocWriterElf(MutableBufferView image,
+                 Bitness bitness,
+                 const AddressTranslator& translator);
+  ~RelocWriterElf() override;
+
+  // ReferenceWriter:
+  void PutNext(Reference ref) override;
+
+ private:
+  MutableBufferView image_;
+  const Bitness bitness_;
+  AddressTranslator::OffsetToRvaCache target_offset_to_rva_;
+};
+
+}  // namespace zucchini
+
+#endif  // COMPONENTS_ZUCCHINI_RELOC_ELF_H_