Repo created

TMessagesProj/jni/voip/webrtc/base/profiler/arm_cfi_table.h

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+// Copyright 2019 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 BASE_PROFILER_ARM_CFI_TABLE_H_
+#define BASE_PROFILER_ARM_CFI_TABLE_H_
+
+#include <memory>
+
+#include "base/containers/buffer_iterator.h"
+#include "base/containers/span.h"
+#include "base/macros.h"
+#include "base/optional.h"
+
+namespace base {
+
+// This class implements methods to read and parse the arm Call Frame
+// Information (CFI) for Chrome, which contains tables for unwinding Chrome
+// functions. For detailed description of the format, see
+// extract_unwind_tables.py.
+class BASE_EXPORT ArmCFITable {
+ public:
+  // The CFI information that correspond to an instruction. {0, 0} is a valid
+  // entry and should be interpreted as the default rule:
+  // .cfa: sp; .cfa = lr (link register).
+  struct FrameEntry {
+    // The offset of the call frame address (CFA) of previous function, relative
+    // to the current stack pointer. Rule for unwinding CFA:
+    // .cfa: sp + cfa_offset.
+    uint16_t cfa_offset = 0;
+    // The offset of location of return address (RA), relative to the previous
+    // call frame address. Rule for unwinding RA:
+    // .ra = *(cfa - ra_offset).
+    uint16_t ra_offset = 0;
+  };
+
+  // Parses |cfi_data| and creates a ArmCFITable that reads from it.
+  // |cfi_data| is required to remain valid for the lifetime of the object.
+  static std::unique_ptr<ArmCFITable> Parse(span<const uint8_t> cfi_data);
+
+  ArmCFITable(span<const uint32_t> function_addresses,
+              span<const uint16_t> entry_data_indices,
+              span<const uint8_t> entry_data);
+  ~ArmCFITable();
+
+  // Finds the CFI row for the given |address| in terms of offset from the
+  // start of the current binary. Concurrent calls are thread safe.
+  Optional<FrameEntry> FindEntryForAddress(uintptr_t address) const;
+
+  size_t GetTableSizeForTesting() const { return function_addresses_.size(); }
+
+ private:
+  // The UNW_INDEX table allows readers to map functions start addresses to
+  // that function's respective entry in the UNW_DATA table.
+  //   - A function's start address is at 0x123, and
+  //   - function_addresses_[2] == 0x123, and
+  //   - entry_data_indices_[2] = 42, then
+  //   - entry_data_[42] is the corresponding entry in the UNW_DATA table for
+  //     the function with the start address of 0x123
+  //
+  // Note that function_addresses is sorted to facilitate easy lookup.
+  const span<const uint32_t> function_addresses_;
+  const span<const uint16_t> entry_data_indices_;
+
+  // A reference to the UNW_DATA table. Each entry in the UNW_DATA table
+  // corresponds to a function, which in turn corresponds to an array of
+  // CFIDataRows. (see arm_cfi_reader.cc).
+  const span<const uint8_t> entry_data_;
+
+  DISALLOW_COPY_AND_ASSIGN(ArmCFITable);
+};
+
+}  // namespace base
+
+#endif  // BASE_PROFILER_ARM_CFI_TABLE_H_