[Zucchini] Add ARM support for ELF files.

This CL enables ARM-ELF (AArch32 and AArch64) support in Zucchini.
* Define ARM {AArch32, AArch64}ReferenceType.
* Add Rel32Finder{Arm, AArch32, AArch64} (with tests) to use
  previously-added ARM disassembly code to extract rel32 references.
* Add DisassemblerElf{Arm, AArch32, AArch64} to parse ARM ELF files and
  create reference readers / writers, and reference groups.
  * For AArch32: Add heuristic detection of ARM vs. Thumb2 mode.
* Add IsTargetOffsetInElfSectionList() (with tests) to help ARM reject
  false positive references.
* Add ReferenceBytesMixerElfArm to remove redundant reference target
  information from bytewise correction data.

Bug: 918867
Change-Id: I1e6d3d8b8d174c85a3d44ca6d642b7ff0bd6a6a6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2922822
Commit-Queue: Samuel Huang <huangs@chromium.org>
Reviewed-by: Etienne Pierre-Doray <etiennep@chromium.org>
Cr-Commit-Position: refs/heads/master@{#908913}
NOKEYCHECK=True
GitOrigin-RevId: 85cc8a596f183487b395a59e80b2f654f241ab2c

1 files changed, 30 insertions, 0 deletions

diff --git a/reference_bytes_mixer.h b/reference_bytes_mixer.h
index 3cbf187..f20b0ef 100644
--- a/reference_bytes_mixer.h
+++ b/reference_bytes_mixer.h
@@ -11,6 +11,7 @@
 
 #include "components/zucchini/buffer_view.h"
 #include "components/zucchini/image_utils.h"
+#include "components/zucchini/rel32_utils.h"
 
 namespace zucchini {
 
@@ -83,6 +84,35 @@ class ReferenceBytesMixer {
                               offset_t new_offset);
 };
 
+// In AArch32 and AArch64, instructions mix operation bits and payload bits in
+// complex ways. This is the main use case of ReferenceBytesMixer.
+class ReferenceBytesMixerElfArm : public ReferenceBytesMixer {
+ public:
+  // |exe_type| must be EXE_TYPE_ELF_ARM or EXE_TYPE_ELF_AARCH64.
+  explicit ReferenceBytesMixerElfArm(ExecutableType exe_type);
+  ReferenceBytesMixerElfArm(const ReferenceBytesMixerElfArm&) = delete;
+  const ReferenceBytesMixerElfArm& operator=(const ReferenceBytesMixerElfArm&) =
+      delete;
+  ~ReferenceBytesMixerElfArm() override;
+
+  // ReferenceBytesMixer:
+  int NumBytes(uint8_t type) const override;
+  ConstBufferView Mix(uint8_t type,
+                      ConstBufferView old_view,
+                      offset_t old_offset,
+                      ConstBufferView new_view,
+                      offset_t new_offset) override;
+
+ private:
+  ArmCopyDispFun GetCopier(uint8_t type) const;
+
+  // For simplicity, 32-bit vs. 64-bit distinction is represented by state
+  // |exe_type_|, instead of creating derived classes.
+  const ExecutableType exe_type_;
+
+  std::vector<uint8_t> out_buffer_;
+};
+
 }  // namespace zucchini
 
 #endif  // COMPONENTS_ZUCCHINI_REFERENCE_BYTES_MIXER_H_