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 // -*- mode: c++ -*-

 // Copyright (c) 2010 Google Inc. All Rights Reserved.

 //

 // Redistribution and use in source and binary forms, with or without

 // modification, are permitted provided that the following conditions are

 // met:

 //

 //     * Redistributions of source code must retain the above copyright

 // notice, this list of conditions and the following disclaimer.

 //     * Redistributions in binary form must reproduce the above

 // copyright notice, this list of conditions and the following disclaimer

 // in the documentation and/or other materials provided with the

 // distribution.

 //     * Neither the name of Google Inc. nor the names of its

 // contributors may be used to endorse or promote products derived from

 // this software without specific prior written permission.

 //

 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR

 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT

 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,

 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT

 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,

 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY

 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE

 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 // Original author: Jim Blandy <jimb@mozilla.com> <jimb@red-bean.com>

 // stabs_reader.h: Define StabsReader, a parser for STABS debugging

 // information. A description of the STABS debugging format can be

 // found at:

 //

 //    http://sourceware.org/gdb/current/onlinedocs/stabs_toc.html

 //

 // The comments here assume you understand the format.

 //

 // This parser can handle big-endian and little-endian data, and the symbol

 // values may be either 32 or 64 bits long. It handles both STABS in

 // sections (as used on Linux) and STABS appearing directly in an

 // a.out-like symbol table (as used in Darwin OS X Mach-O files).

 #ifndef COMMON_STABS_READER_H__

 #define COMMON_STABS_READER_H__

 #include <stddef.h>

 #include <stdint.h>

 #ifdef HAVE_CONFIG_H

 #include <config.h>

 #endif

 #ifdef HAVE_A_OUT_H

 #include <a.out.h>

 #endif

 #ifdef HAVE_MACH_O_NLIST_H

 #include <mach-o/nlist.h>

 #endif

 #include <string>

 #include <vector>

 #include "common/byte_cursor.h"

 #include "common/using_std_string.h"

 namespace google_breakpad {

 class StabsHandler;

 class StabsReader {

  public:

   // Create a reader for the STABS debug information whose .stab section is

   // being traversed by ITERATOR, and whose .stabstr section is referred to

   // by STRINGS. The reader will call the member functions of HANDLER to

   // report the information it finds, when the reader's 'Process' member

   // function is called.

   //

   // BIG_ENDIAN should be true if the entries in the .stab section are in

   // big-endian form, or false if they are in little-endian form.

   //

   // VALUE_SIZE should be either 4 or 8, indicating the size of the 'value'

   // field in each entry in bytes.

   //

   // UNITIZED should be true if the STABS data is stored in units with

   // N_UNDF headers. This is usually the case for STABS stored in sections,

   // like .stab/.stabstr, and usually not the case for STABS stored in the

   // actual symbol table; UNITIZED should be true when parsing Linux stabs,

   // false when parsing Mac OS X STABS. For details, see:

   // http://sourceware.org/gdb/current/onlinedocs/stabs/Stab-Section-Basics.html

   // 

   // Note that, in ELF, the .stabstr section should be found using the

   // 'sh_link' field of the .stab section header, not by name.

   StabsReader(const uint8_t *stab,    size_t stab_size,

               const uint8_t *stabstr, size_t stabstr_size,

               bool big_endian, size_t value_size, bool unitized,

               StabsHandler *handler);

   // Process the STABS data, calling the handler's member functions to

   // report what we find.  While the handler functions return true,

   // continue to process until we reach the end of the section.  If we

   // processed the entire section and all handlers returned true,

   // return true.  If any handler returned false, return false.

   // 

   // This is only meant to be called once per StabsReader instance;

   // resuming a prior processing pass that stopped abruptly isn't supported.

   bool Process();

  private:

   // An class for walking arrays of STABS entries. This isolates the main

   // STABS reader from the exact format (size; endianness) of the entries

   // themselves.

   class EntryIterator {

    public:

     // The contents of a STABS entry, adjusted for the host's endianness,

     // word size, 'struct nlist' layout, and so on.

     struct Entry {

       // True if this iterator has reached the end of the entry array. When

       // this is set, the other members of this structure are not valid.

       bool at_end;

       // The number of this entry within the list.

       size_t index;

       // The current entry's name offset. This is the offset within the

       // current compilation unit's strings, as establish by the N_UNDF entries.

       size_t name_offset;

       // The current entry's type, 'other' field, descriptor, and value.

       unsigned char type;

       unsigned char other;

       short descriptor;

       uint64_t value;

     };

     // Create a EntryIterator walking the entries in BUFFER. Treat the

     // entries as big-endian if BIG_ENDIAN is true, as little-endian

     // otherwise. Assume each entry has a 'value' field whose size is

     // VALUE_SIZE.

     //

     // This would not be terribly clean to extend to other format variations,

     // but it's enough to handle Linux and Mac, and we'd like STABS to die

     // anyway.

     //

     // For the record: on Linux, STABS entry values are always 32 bits,

     // regardless of the architecture address size (don't ask me why); on

     // Mac, they are 32 or 64 bits long. Oddly, the section header's entry

     // size for a Linux ELF .stab section varies according to the ELF class

     // from 12 to 20 even as the actual entries remain unchanged.

     EntryIterator(const ByteBuffer *buffer, bool big_endian, size_t value_size);

     // Move to the next entry. This function's behavior is undefined if

     // at_end() is true when it is called.

     EntryIterator &operator++() { Fetch(); entry_.index++; return *this; }

     // Dereferencing this iterator produces a reference to an Entry structure

     // that holds the current entry's values. The entry is owned by this

     // EntryIterator, and will be invalidated at the next call to operator++.

     const Entry &operator*() const { return entry_; }

     const Entry *operator->() const { return &entry_; }

    private:

     // Read the STABS entry at cursor_, and set entry_ appropriately.

     void Fetch();

     // The size of entries' value field, in bytes.

     size_t value_size_;

     // A byte cursor traversing buffer_.

     ByteCursor cursor_;

     // Values for the entry this iterator refers to.

     Entry entry_;

   };

   // A source line, saved to be reported later.

   struct Line {

     uint64_t address;

     const char *filename;

     int number;

   };

   // Return the name of the current symbol.

   const char *SymbolString();

   // Process a compilation unit starting at symbol_.  Return true

   // to continue processing, or false to abort.

   bool ProcessCompilationUnit();

   // Process a function in current_source_file_ starting at symbol_.

   // Return true to continue processing, or false to abort.

   bool ProcessFunction();

   // Process an exported function symbol.

   // Return true to continue processing, or false to abort.

   bool ProcessExtern();

   // The STABS entries being parsed.

   ByteBuffer entries_;

   // The string section to which the entries refer.

   ByteBuffer strings_;

   // The iterator walking the STABS entries.

   EntryIterator iterator_;

   // True if the data is "unitized"; see the explanation in the comment for

   // StabsReader::StabsReader.

   bool unitized_;

   StabsHandler *handler_;

   // The offset of the current compilation unit's strings within stabstr_.

   size_t string_offset_;

   // The value string_offset_ should have for the next compilation unit,

   // as established by N_UNDF entries.

   size_t next_cu_string_offset_;

   // The current source file name.

   const char *current_source_file_;

   // Mac OS X STABS place SLINE records before functions; we accumulate a

   // vector of these until we see the FUN record, and then report them

   // after the StartFunction call.

   std::vector<Line> queued_lines_;

 };

 // Consumer-provided callback structure for the STABS reader.  Clients

 // of the STABS reader provide an instance of this structure.  The

 // reader then invokes the member functions of that instance to report

 // the information it finds.

 //

 // The default definitions of the member functions do nothing, and return

 // true so processing will continue.

 class StabsHandler {

  public:

   StabsHandler() { }

   virtual ~StabsHandler() { }

   // Some general notes about the handler callback functions:

   // Processing proceeds until the end of the .stabs section, or until

   // one of these functions returns false.

   // The addresses given are as reported in the STABS info, without

   // regard for whether the module may be loaded at different

   // addresses at different times (a shared library, say).  When

   // processing STABS from an ELF shared library, the addresses given

   // all assume the library is loaded at its nominal load address.

   // They are *not* offsets from the nominal load address.  If you

   // want offsets, you must subtract off the library's nominal load

   // address.

   // The arguments to these functions named FILENAME are all

   // references to strings stored in the .stabstr section.  Because

   // both the Linux and Solaris linkers factor out duplicate strings

   // from the .stabstr section, the consumer can assume that if two

   // FILENAME values are different addresses, they represent different

   // file names.

   //

   // Thus, it's safe to use (say) std::map<char *, ...>, which does

   // string address comparisons, not string content comparisons.

   // Since all the strings are in same array of characters --- the

   // .stabstr section --- comparing their addresses produces

   // predictable, if not lexicographically meaningful, results.

   // Begin processing a compilation unit whose main source file is

   // named FILENAME, and whose base address is ADDRESS.  If

   // BUILD_DIRECTORY is non-NULL, it is the name of the build

   // directory in which the compilation occurred.

   virtual bool StartCompilationUnit(const char *filename, uint64_t address,

                                     const char *build_directory) {

     return true;

   }

   // Finish processing the compilation unit.  If ADDRESS is non-zero,

   // it is the ending address of the compilation unit.  If ADDRESS is

   // zero, then the compilation unit's ending address is not

   // available, and the consumer must infer it by other means.

   virtual bool EndCompilationUnit(uint64_t address) { return true; }

   // Begin processing a function named NAME, whose starting address is

   // ADDRESS.  This function belongs to the compilation unit that was

   // most recently started but not ended.

   //

   // Note that, unlike filenames, NAME is not a pointer into the

   // .stabstr section; this is because the name as it appears in the

   // STABS data is followed by type information.  The value passed to

   // StartFunction is the function name alone.

   //

   // In languages that use name mangling, like C++, NAME is mangled.

   virtual bool StartFunction(const string &name, uint64_t address) {

     return true;

   }

   // Finish processing the function.  If ADDRESS is non-zero, it is

   // the ending address for the function.  If ADDRESS is zero, then

   // the function's ending address is not available, and the consumer

   // must infer it by other means.

   virtual bool EndFunction(uint64_t address) { return true; }

   // Report that the code at ADDRESS is attributable to line NUMBER of

   // the source file named FILENAME.  The caller must infer the ending

   // address of the line.

   virtual bool Line(uint64_t address, const char *filename, int number) {

     return true;

   }

   // Report that an exported function NAME is present at ADDRESS.

   // The size of the function is unknown.

   virtual bool Extern(const string &name, uint64_t address) {

     return true;

   }

   // Report a warning.  FORMAT is a printf-like format string,

   // specifying how to format the subsequent arguments.

   virtual void Warning(const char *format, ...) = 0;

 };

 } // namespace google_breakpad

 #endif  // COMMON_STABS_READER_H__