bin/zxdb/symbols/location.h

// Copyright 2018 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#pragma once

#include <stdint.h>

#include "garnet/bin/zxdb/symbols/file_line.h"
#include "garnet/bin/zxdb/symbols/lazy_symbol.h"
#include "garnet/bin/zxdb/symbols/symbol_context.h"

namespace zxdb {

class CodeBlock;
class Function;

// Represents all the symbol information for a code location.
class Location {
 public:
  // A location can be invalid (has no address), can have an address that we
  // haven't tried to symbolize, and a symbolized address. The latter two
  // states allow symbolizing on demand without having additional types.
  //
  // The "symbolized" state doesn't necessarily mean there are symbols, it
  // just means we tried to symbolize it.
  enum class State {
    // There is no address or data for this location.
    kInvalid,

    // There is an address for this location but we haven't tried to symbolize
    // it.
    kAddress,

    // There is an address for the location and we tried to symbolize it. This
    // doesn't mean that symbolization succeeded, so the symbol() and file/line
    // could still be empty.
    kSymbolized,

    // The symbol corresponds to a Variable, but its location has not been
    // computed so it will have a null address.
    //
    // Some global variables actually need to be evaluated asynchronously
    // based on the current CPU state. For example, TLS values are located
    // relative to the CPU register that indicates the TLS base. When
    // resolving a symbolic name, we can encounter these which can't be
    // evaluated in the global context of the synbol system.
    //
    // Currently these aren't handled in most places. But if a caller is in a
    // position to evaluate this it can fill out the address from the symbol.
    kUnlocatedVariable,
  };

  Location();
  Location(State state, uint64_t address);

  // Symbolized location.
  Location(uint64_t address, FileLine file_line, int column,
           const SymbolContext& symbol_context,
           LazySymbol symbol = LazySymbol());

  // Unlocated variable.
  Location(const SymbolContext& symbol_context, LazySymbol symbol);

  ~Location();

  bool is_valid() const { return state_ != State::kInvalid; }

  // The different between "symbolized" and "has_symbols" is that the former
  // means we tried to symbolize it, and the latter means we actually
  // succeeded to symbolize EITHER the line or the function. One or the other
  // could be missing, however.
  bool is_symbolized() const { return state_ == State::kSymbolized; }
  bool has_symbols() const { return file_line_.is_valid() || symbol_; }

  // The absolute address of this location.
  uint64_t address() const { return address_; }

  const FileLine& file_line() const { return file_line_; }
  int column() const { return column_; }

  // The symbol associated with this address, if any. In the case of code this
  // will be a Function. It will not be the code block inside the function
  // (code wanting lexical blocks can look inside the function's children as
  // needed). It could also be a variable symbol corresponding to a global or
  // static variable.
  //
  // When looking up code locations from the symbol system, this will be the
  // most specific function covering the code in question (the innermost
  // inlined function if there is one). But Locations may be generated (e.g. by
  // the stack unwinder) for any of the other inlined functions that may cover
  // the same address.
  //
  // This isn't necessarily valid, even if the State == kSymbolized. It could
  // be the symbol table indicates file/line info for this address but could
  // lack a function record for it.
  const LazySymbol& symbol() const { return symbol_; }

  // Symbolized locations will have a valid symbol context for converting
  // addresses.
  const SymbolContext& symbol_context() const { return symbol_context_; }

  // Offsets the code addresses in this by adding an amount. This is used to
  // convert module-relative addresses to global ones by adding the module
  // load address.
  void AddAddressOffset(uint64_t offset);

 private:
  State state_ = State::kInvalid;
  uint64_t address_ = 0;
  FileLine file_line_;
  int column_ = 0;
  LazySymbol symbol_;
  SymbolContext symbol_context_ = SymbolContext::ForRelativeAddresses();
};

}  // namespace zxdb