Add MachOImageSymbolTableReader and hook it up to MachOImageReader

util/mac/mach_o_image_symbol_table_reader.h

+// Copyright 2014 The Crashpad Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef CRASHPAD_UTIL_MAC_MACH_O_IMAGE_SYMBOL_TABLE_READER_H_
+#define CRASHPAD_UTIL_MAC_MACH_O_IMAGE_SYMBOL_TABLE_READER_H_
+
+#include "base/basictypes.h"
+
+#include <map>
+#include <string>
+
+#include <mach/mach.h>
+#include <stdint.h>
+
+#include "util/mac/mach_o_image_segment_reader.h"
+#include "util/mac/process_reader.h"
+#include "util/mac/process_types.h"
+#include "util/misc/initialization_state_dcheck.h"
+
+namespace crashpad {
+
+namespace internal {
+class MachOImageSymbolTableReaderInitializer;
+}  // namespace internal
+
+//! \brief A reader for symbol tables in Mach-O images mapped into another
+//!     process.
+class MachOImageSymbolTableReader {
+ public:
+  //! \brief Information about a symbol in a module’s symbol table.
+  //!
+  //! This is a more minimal form of the `nlist` (or `nlist_64`) structure,
+  //! only containing the equivalent of the `n_value` and `n_sect` fields.
+  struct SymbolInformation {

[Robert Sesek, 2014/09/05 19:04:16]

For ProcessReader, you didn't use a nested struct but created
ProcessReaderModule. To be consistent, you could also make that
ProcessReader::Module, or make this non-nested.

[Mark Mentovai, 2014/09/05 20:22:31]

rsesek wrote:
Good point! Spun off https://codereview.chromium.org/543193002.

+    //! \brief The address of the symbol as it exists in the symbol table, not
+    //!     adjusted for any “slide.”
+    mach_vm_address_t value;
+
+    //! \brief The 1-based section index in the module in which the symbol is
+    //!     found.
+    //!
+    //! For symbols defined in a section (`N_SECT`), this is the section index
+    //! that can be passed to MachOImageReader::GetSectionAtIndex(), and \a
+    //! value will need to be adjusted for segment slide if the containing
+    //! segment slid when loaded. For absolute symbols (`N_ABS`), this will be
+    //! `NO_SECT` (`0`), and \a value must not be adjusted for segment slide.
+    uint8_t section;
+  };
+
+  MachOImageSymbolTableReader();
+  ~MachOImageSymbolTableReader();
+
+  //! \brief Reads the symbol table from another process.
+  //!
+  //! This method must only be called once on an object. This method must be
+  //! called successfully before any other method in this class may be called.
+  //!
+  //! \param[in] process_reader The reader for the remote process.
+  //! \param[in] symtab_command The `LC_SYMTAB` load command that identifies
+  //!     the symbol table.
+  //! \param[in] dysymtab_command The `LC_DYSYMTAB` load command that identifies
+  //!     dynamic symbol information within the symbol table. This load command
+  //!     is not present in all modules, and this parameter may be `NULL` for
+  //!     modules that do not have this information. When present, \a
+  //!     dysymtab_command is an optimization that allows the symbol table
+  //!     reader to only examine symbol table entries known to be relevant for
+  //!     its purposes.
+  //! \param[in] linkedit_segment The `__LINKEDIT` segment. This segment should
+  //!     contain the data referenced by \a symtab_command and \a
+  //!     dysymtab_command. This may be any segment in the module, but by
+  //!     convention, the name `__LINKEDIT` is used for this purpose.
+  //! \param[in] linkedit_address The address where \a linkedit_segment is
+  //!     loaded in the remote process.
+  //! \param[in] linkedit_size The size of \a linkedit_segment, starting at \a
+  //!     linkedit_address, as it exists in the remote process.
+  //! \param[in] module_info A string to be used in logged messages. This string
+  //!     is for diagnostic purposes only, and may be empty.
+  //!
+  //! \return `true` if the symbol table was read successfully. `false`
+  //!     otherwise, with an appropriate message logged.
+  bool Initialize(ProcessReader* process_reader,
+                  const process_types::symtab_command* symtab_command,
+                  const process_types::dysymtab_command* dysymtab_command,
+                  const MachOImageSegmentReader* linkedit_segment,
+                  mach_vm_address_t linkedit_address,
+                  mach_vm_size_t linkedit_size,
+                  const std::string& module_info);
+
+  //! \brief Looks up a symbol in the image’s symbol table.
+  //!
+  //! The returned information captures the symbol as it exists in the image’s
+  //! symbol table, not adjusted for any “slide.”
+  //!
+  //! \param[in] name The name of the symbol to look up, “mangled” or
+  //!     “decorated” appropriately. For example, use `"_main"` to look up the
+  //!     symbol for the C `main()` function, and use `"__Z4Funcv"` to look up
+  //!     the symbol for the C++ `Func()` function.
+  //!
+  //! \return A SymbolInformation* object with information about the symbol if
+  //!     it was found, or `NULL` if the symbol was not found or if an error
+  //!     occurred. On error, a warning message will also be logged.
+  //!
+  //! \note Symbol values returned via this interface are not adjusted for
+  //!     “slide.” For slide-adjusted values, use the higher-level
+  //!     MachOImageReader::LookUpExternalDefinedSymbol() interface.
+  const SymbolInformation* LookUpExternalDefinedSymbol(
+      const std::string& name) const;
+
+ private:
+  // TODO(mark): Use unordered_map or a similar hash-based map? For now,
+  // std::map is fine because this map only stores external defined symbols,
+  // and there aren’t expected to be very many of those that performance would
+  // become a problem. std::map is also guaranteed to be part of the standard
+  // library, which isn’t the case for std::unordered_map, which requires the
+  // C++11 library. In reality, std::unordered_map does not appear to provide
+  // a performance advantage. It appears that the memory copies currently done
+  // by TaskMemory::Read() have substantially more impact on symbol table
+  // operations.
+  typedef std::map<std::string, SymbolInformation> SymbolInformationMap;
+
+  SymbolInformationMap external_defined_symbols_;
+  InitializationStateDcheck initialized_;
+
+  friend class internal::MachOImageSymbolTableReaderInitializer;

[Robert Sesek, 2014/09/05 19:04:16]

Is the friend only required to access the SymbolInformationMap type?

[Mark Mentovai, 2014/09/05 20:22:31]

rsesek wrote:
Yeah. I made it public instead of having a friend, but left a comment explaining
why it’s public. Is that better?

[Robert Sesek, 2014/09/05 20:41:31]

Yeah, I think so.

+
+  DISALLOW_COPY_AND_ASSIGN(MachOImageSymbolTableReader);
+};
+
+}  // namespace crashpad
+
+#endif  // CRASHPAD_UTIL_MAC_MACH_O_IMAGE_SYMBOL_TABLE_READER_H_