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// -*- mode: c++ -*-
// Copyright (c) 2010 Google Inc. All Rights Reserved.
//
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// 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
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//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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// 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_MACH_O_NLIST_H
#include <mach-o/nlist.h>
#elif defined(HAVE_A_OUT_H)
#include <a.out.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__