The Tor Browser: toolkit/crashreporter/google-breakpad/src/common/dwarf/dwarf2reader.h@129ffea94266 (annotated)

toolkit/crashreporter/google-breakpad/src/common/dwarf/dwarf2reader.h@129ffea94266 (annotated)

toolkit/crashreporter/google-breakpad/src/common/dwarf/dwarf2reader.h

Sat, 03 Jan 2015 20:18:00 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Sat, 03 Jan 2015 20:18:00 +0100
branch: TOR_BUG_3246
changeset 7: 129ffea94266
permissions: -rw-r--r--

Conditionally enable double key logic according to:
private browsing mode or privacy.thirdparty.isolate preference and
implement in GetCookieStringCommon and FindCookie where it counts...
With some reservations of how to convince FindCookie users to test
condition and pass a nullptr when disabling double key logic.

 // -*- 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.
 // CFI reader author: Jim Blandy <jimb@mozilla.com> <jimb@red-bean.com>
 // This file contains definitions related to the DWARF2/3 reader and
 // it's handler interfaces.
 // The DWARF2/3 specification can be found at
 // http://dwarf.freestandards.org and should be considered required
 // reading if you wish to modify the implementation.
 // Only a cursory attempt is made to explain terminology that is
 // used here, as it is much better explained in the standard documents
 #ifndef COMMON_DWARF_DWARF2READER_H__
 #define COMMON_DWARF_DWARF2READER_H__
 #include <list>
 #include <map>
 #include <string>
 #include <utility>
 #include <vector>
 #include "common/dwarf/bytereader.h"
 #include "common/dwarf/dwarf2enums.h"
 #include "common/dwarf/types.h"
 #include "common/using_std_string.h"
 namespace dwarf2reader {
 struct LineStateMachine;
 class Dwarf2Handler;
 class LineInfoHandler;
 // This maps from a string naming a section to a pair containing a
 // the data for the section, and the size of the section.
 typedef std::map<string, std::pair<const char*, uint64> > SectionMap;
 typedef std::list<std::pair<enum DwarfAttribute, enum DwarfForm> >
     AttributeList;
 typedef AttributeList::iterator AttributeIterator;
 typedef AttributeList::const_iterator ConstAttributeIterator;
 struct LineInfoHeader {
   uint64 total_length;
   uint16 version;
   uint64 prologue_length;
   uint8 min_insn_length; // insn stands for instructin
   bool default_is_stmt; // stmt stands for statement
   int8 line_base;
   uint8 line_range;
   uint8 opcode_base;
   // Use a pointer so that signalsafe_addr2line is able to use this structure
   // without heap allocation problem.
   std::vector<unsigned char> *std_opcode_lengths;
 };
 class LineInfo {
  public:
   // Initializes a .debug_line reader. Buffer and buffer length point
   // to the beginning and length of the line information to read.
   // Reader is a ByteReader class that has the endianness set
   // properly.
   LineInfo(const char* buffer_, uint64 buffer_length,
            ByteReader* reader, LineInfoHandler* handler);
   virtual ~LineInfo() {
     if (header_.std_opcode_lengths) {
       delete header_.std_opcode_lengths;
     }
   }
   // Start processing line info, and calling callbacks in the handler.
   // Consumes the line number information for a single compilation unit.
   // Returns the number of bytes processed.
   uint64 Start();
   // Process a single line info opcode at START using the state
   // machine at LSM.  Return true if we should define a line using the
   // current state of the line state machine.  Place the length of the
   // opcode in LEN.
   // If LSM_PASSES_PC is non-NULL, this function also checks if the lsm
   // passes the address of PC. In other words, LSM_PASSES_PC will be
   // set to true, if the following condition is met.
   //
   // lsm's old address < PC <= lsm's new address
   static bool ProcessOneOpcode(ByteReader* reader,
                                LineInfoHandler* handler,
                                const struct LineInfoHeader &header,
                                const char* start,
                                struct LineStateMachine* lsm,
                                size_t* len,
                                uintptr pc,
                                bool *lsm_passes_pc);
  private:
   // Reads the DWARF2/3 header for this line info.
   void ReadHeader();
   // Reads the DWARF2/3 line information
   void ReadLines();
   // The associated handler to call processing functions in
   LineInfoHandler* handler_;
   // The associated ByteReader that handles endianness issues for us
   ByteReader* reader_;
   // A DWARF2/3 line info header.  This is not the same size as
   // in the actual file, as the one in the file may have a 32 bit or
   // 64 bit lengths
   struct LineInfoHeader header_;
   // buffer is the buffer for our line info, starting at exactly where
   // the line info to read is.  after_header is the place right after
   // the end of the line information header.
   const char* buffer_;
   uint64 buffer_length_;
   const char* after_header_;
 };
 // This class is the main interface between the line info reader and
 // the client.  The virtual functions inside this get called for
 // interesting events that happen during line info reading.  The
 // default implementation does nothing
 class LineInfoHandler {
  public:
   LineInfoHandler() { }
   virtual ~LineInfoHandler() { }
   // Called when we define a directory.  NAME is the directory name,
   // DIR_NUM is the directory number
   virtual void DefineDir(const string& name, uint32 dir_num) { }
   // Called when we define a filename. NAME is the filename, FILE_NUM
   // is the file number which is -1 if the file index is the next
   // index after the last numbered index (this happens when files are
   // dynamically defined by the line program), DIR_NUM is the
   // directory index for the directory name of this file, MOD_TIME is
   // the modification time of the file, and LENGTH is the length of
   // the file
   virtual void DefineFile(const string& name, int32 file_num,
                           uint32 dir_num, uint64 mod_time,
                           uint64 length) { }
   // Called when the line info reader has a new line, address pair
   // ready for us. ADDRESS is the address of the code, LENGTH is the
   // length of its machine code in bytes, FILE_NUM is the file number
   // containing the code, LINE_NUM is the line number in that file for
   // the code, and COLUMN_NUM is the column number the code starts at,
   // if we know it (0 otherwise).
   virtual void AddLine(uint64 address, uint64 length,
                        uint32 file_num, uint32 line_num, uint32 column_num) { }
 };
 // The base of DWARF2/3 debug info is a DIE (Debugging Information
 // Entry.
 // DWARF groups DIE's into a tree and calls the root of this tree a
 // "compilation unit".  Most of the time, there is one compilation
 // unit in the .debug_info section for each file that had debug info
 // generated.
 // Each DIE consists of
 // 1. a tag specifying a thing that is being described (ie
 // DW_TAG_subprogram for functions, DW_TAG_variable for variables, etc
 // 2. attributes (such as DW_AT_location for location in memory,
 // DW_AT_name for name), and data for each attribute.
 // 3. A flag saying whether the DIE has children or not
 // In order to gain some amount of compression, the format of
 // each DIE (tag name, attributes and data forms for the attributes)
 // are stored in a separate table called the "abbreviation table".
 // This is done because a large number of DIEs have the exact same tag
 // and list of attributes, but different data for those attributes.
 // As a result, the .debug_info section is just a stream of data, and
 // requires reading of the .debug_abbrev section to say what the data
 // means.
 // As a warning to the user, it should be noted that the reason for
 // using absolute offsets from the beginning of .debug_info is that
 // DWARF2/3 supports referencing DIE's from other DIE's by their offset
 // from either the current compilation unit start, *or* the beginning
 // of the .debug_info section.  This means it is possible to reference
 // a DIE in one compilation unit from a DIE in another compilation
 // unit.  This style of reference is usually used to eliminate
 // duplicated information that occurs across compilation
 // units, such as base types, etc.  GCC 3.4+ support this with
 // -feliminate-dwarf2-dups.  Other toolchains will sometimes do
 // duplicate elimination in the linker.
 class CompilationUnit {
  public:
   // Initialize a compilation unit.  This requires a map of sections,
   // the offset of this compilation unit in the .debug_info section, a
   // ByteReader, and a Dwarf2Handler class to call callbacks in.
   CompilationUnit(const SectionMap& sections, uint64 offset,
                   ByteReader* reader, Dwarf2Handler* handler);
   virtual ~CompilationUnit() {
     if (abbrevs_) delete abbrevs_;
   }
   // Begin reading a Dwarf2 compilation unit, and calling the
   // callbacks in the Dwarf2Handler
   // Return the full length of the compilation unit, including
   // headers. This plus the starting offset passed to the constructor
   // is the offset of the end of the compilation unit --- and the
   // start of the next compilation unit, if there is one.
   uint64 Start();
  private:
   // This struct represents a single DWARF2/3 abbreviation
   // The abbreviation tells how to read a DWARF2/3 DIE, and consist of a
   // tag and a list of attributes, as well as the data form of each attribute.
   struct Abbrev {
     uint64 number;
     enum DwarfTag tag;
     bool has_children;
     AttributeList attributes;
   };
   // A DWARF2/3 compilation unit header.  This is not the same size as
   // in the actual file, as the one in the file may have a 32 bit or
   // 64 bit length.
   struct CompilationUnitHeader {
     uint64 length;
     uint16 version;
     uint64 abbrev_offset;
     uint8 address_size;
   } header_;
   // Reads the DWARF2/3 header for this compilation unit.
   void ReadHeader();
   // Reads the DWARF2/3 abbreviations for this compilation unit
   void ReadAbbrevs();
   // Processes a single DIE for this compilation unit and return a new
   // pointer just past the end of it
   const char* ProcessDIE(uint64 dieoffset,
                                   const char* start,
                                   const Abbrev& abbrev);
   // Processes a single attribute and return a new pointer just past the
   // end of it
   const char* ProcessAttribute(uint64 dieoffset,
                                         const char* start,
                                         enum DwarfAttribute attr,
                                         enum DwarfForm form);
   // Processes all DIEs for this compilation unit
   void ProcessDIEs();
   // Skips the die with attributes specified in ABBREV starting at
   // START, and return the new place to position the stream to.
   const char* SkipDIE(const char* start,
                                const Abbrev& abbrev);
   // Skips the attribute starting at START, with FORM, and return the
   // new place to position the stream to.
   const char* SkipAttribute(const char* start,
                                      enum DwarfForm form);
   // Offset from section start is the offset of this compilation unit
   // from the beginning of the .debug_info section.
   uint64 offset_from_section_start_;
   // buffer is the buffer for our CU, starting at .debug_info + offset
   // passed in from constructor.
   // after_header points to right after the compilation unit header.
   const char* buffer_;
   uint64 buffer_length_;
   const char* after_header_;
   // The associated ByteReader that handles endianness issues for us
   ByteReader* reader_;
   // The map of sections in our file to buffers containing their data
   const SectionMap& sections_;
   // The associated handler to call processing functions in
   Dwarf2Handler* handler_;
   // Set of DWARF2/3 abbreviations for this compilation unit.  Indexed
   // by abbreviation number, which means that abbrevs_[0] is not
   // valid.
   std::vector<Abbrev>* abbrevs_;
   // String section buffer and length, if we have a string section.
   // This is here to avoid doing a section lookup for strings in
   // ProcessAttribute, which is in the hot path for DWARF2 reading.
   const char* string_buffer_;
   uint64 string_buffer_length_;
 };
 // This class is the main interface between the reader and the
 // client.  The virtual functions inside this get called for
 // interesting events that happen during DWARF2 reading.
 // The default implementation skips everything.
 class Dwarf2Handler {
  public:
   Dwarf2Handler() { }
   virtual ~Dwarf2Handler() { }
   // Start to process a compilation unit at OFFSET from the beginning of the
   // .debug_info section. Return false if you would like to skip this
   // compilation unit.
   virtual bool StartCompilationUnit(uint64 offset, uint8 address_size,
                                     uint8 offset_size, uint64 cu_length,
                                     uint8 dwarf_version) { return false; }
   // Start to process a DIE at OFFSET from the beginning of the .debug_info
   // section. Return false if you would like to skip this DIE.
   virtual bool StartDIE(uint64 offset, enum DwarfTag tag) { return false; }
   // Called when we have an attribute with unsigned data to give to our
   // handler. The attribute is for the DIE at OFFSET from the beginning of the
   // .debug_info section. Its name is ATTR, its form is FORM, and its value is
   // DATA.
   virtual void ProcessAttributeUnsigned(uint64 offset,
                                         enum DwarfAttribute attr,
                                         enum DwarfForm form,
                                         uint64 data) { }
   // Called when we have an attribute with signed data to give to our handler.
   // The attribute is for the DIE at OFFSET from the beginning of the
   // .debug_info section. Its name is ATTR, its form is FORM, and its value is
   // DATA.
   virtual void ProcessAttributeSigned(uint64 offset,
                                       enum DwarfAttribute attr,
                                       enum DwarfForm form,
                                       int64 data) { }
   // Called when we have an attribute whose value is a reference to
   // another DIE. The attribute belongs to the DIE at OFFSET from the
   // beginning of the .debug_info section. Its name is ATTR, its form
   // is FORM, and the offset of the DIE being referred to from the
   // beginning of the .debug_info section is DATA.
   virtual void ProcessAttributeReference(uint64 offset,
                                          enum DwarfAttribute attr,
                                          enum DwarfForm form,
                                          uint64 data) { }
   // Called when we have an attribute with a buffer of data to give to our
   // handler. The attribute is for the DIE at OFFSET from the beginning of the
   // .debug_info section. Its name is ATTR, its form is FORM, DATA points to
   // the buffer's contents, and its length in bytes is LENGTH. The buffer is
   // owned by the caller, not the callee, and may not persist for very long.
   // If you want the data to be available later, it needs to be copied.
   virtual void ProcessAttributeBuffer(uint64 offset,
                                       enum DwarfAttribute attr,
                                       enum DwarfForm form,
                                       const char* data,
                                       uint64 len) { }
   // Called when we have an attribute with string data to give to our handler.
   // The attribute is for the DIE at OFFSET from the beginning of the
   // .debug_info section. Its name is ATTR, its form is FORM, and its value is
   // DATA.
   virtual void ProcessAttributeString(uint64 offset,
                                       enum DwarfAttribute attr,
                                       enum DwarfForm form,
                                       const string& data) { }
   // Called when we have an attribute whose value is the 64-bit signature
   // of a type unit in the .debug_types section. OFFSET is the offset of
   // the DIE whose attribute we're reporting. ATTR and FORM are the
   // attribute's name and form. SIGNATURE is the type unit's signature.
   virtual void ProcessAttributeSignature(uint64 offset,
                                          enum DwarfAttribute attr,
                                          enum DwarfForm form,
                                          uint64 signature) { }
   // Called when finished processing the DIE at OFFSET.
   // Because DWARF2/3 specifies a tree of DIEs, you may get starts
   // before ends of the previous DIE, as we process children before
   // ending the parent.
   virtual void EndDIE(uint64 offset) { }
 };
 // This class is a reader for DWARF's Call Frame Information.  CFI
 // describes how to unwind stack frames --- even for functions that do
 // not follow fixed conventions for saving registers, whose frame size
 // varies as they execute, etc.
 //
 // CFI describes, at each machine instruction, how to compute the
 // stack frame's base address, how to find the return address, and
 // where to find the saved values of the caller's registers (if the
 // callee has stashed them somewhere to free up the registers for its
 // own use).
 //
 // For example, suppose we have a function whose machine code looks
 // like this (imagine an assembly language that looks like C, for a
 // machine with 32-bit registers, and a stack that grows towards lower
 // addresses):
 //
 // func:                                ; entry point; return address at sp
 // func+0:      sp = sp - 16            ; allocate space for stack frame
 // func+1:      sp[12] = r0             ; save r0 at sp+12
 // ...                                  ; other code, not frame-related
 // func+10:     sp -= 4; *sp = x        ; push some x on the stack
 // ...                                  ; other code, not frame-related
 // func+20:     r0 = sp[16]             ; restore saved r0
 // func+21:     sp += 20                ; pop whole stack frame
 // func+22:     pc = *sp; sp += 4       ; pop return address and jump to it
 //
 // DWARF CFI is (a very compressed representation of) a table with a
 // row for each machine instruction address and a column for each
 // register showing how to restore it, if possible.
 //
 // A special column named "CFA", for "Canonical Frame Address", tells how
 // to compute the base address of the frame; registers' entries may
 // refer to the CFA in describing where the registers are saved.
 //
 // Another special column, named "RA", represents the return address.
 //
 // For example, here is a complete (uncompressed) table describing the
 // function above:
 //
 //     insn      cfa    r0      r1 ...  ra
 //     =======================================
 //     func+0:   sp                     cfa[0]
 //     func+1:   sp+16                  cfa[0]
 //     func+2:   sp+16  cfa[-4]         cfa[0]
 //     func+11:  sp+20  cfa[-4]         cfa[0]
 //     func+21:  sp+20                  cfa[0]
 //     func+22:  sp                     cfa[0]
 //
 // Some things to note here:
 //
 // - Each row describes the state of affairs *before* executing the
 //   instruction at the given address.  Thus, the row for func+0
 //   describes the state before we allocate the stack frame.  In the
 //   next row, the formula for computing the CFA has changed,
 //   reflecting that allocation.
 //
 // - The other entries are written in terms of the CFA; this allows
 //   them to remain unchanged as the stack pointer gets bumped around.
 //   For example, the rule for recovering the return address (the "ra"
 //   column) remains unchanged throughout the function, even as the
 //   stack pointer takes on three different offsets from the return
 //   address.
 //
 // - Although we haven't shown it, most calling conventions designate
 //   "callee-saves" and "caller-saves" registers. The callee must
 //   preserve the values of callee-saves registers; if it uses them,
 //   it must save their original values somewhere, and restore them
 //   before it returns. In contrast, the callee is free to trash
 //   caller-saves registers; if the callee uses these, it will
 //   probably not bother to save them anywhere, and the CFI will
 //   probably mark their values as "unrecoverable".
 //
 //   (However, since the caller cannot assume the callee was going to
 //   save them, caller-saves registers are probably dead in the caller
 //   anyway, so compilers usually don't generate CFA for caller-saves
 //   registers.)
 //
 // - Exactly where the CFA points is a matter of convention that
 //   depends on the architecture and ABI in use. In the example, the
 //   CFA is the value the stack pointer had upon entry to the
 //   function, pointing at the saved return address. But on the x86,
 //   the call frame information generated by GCC follows the
 //   convention that the CFA is the address *after* the saved return
 //   address.
 //
 //   But by definition, the CFA remains constant throughout the
 //   lifetime of the frame. This makes it a useful value for other
 //   columns to refer to. It is also gives debuggers a useful handle
 //   for identifying a frame.
 //
 // If you look at the table above, you'll notice that a given entry is
 // often the same as the one immediately above it: most instructions
 // change only one or two aspects of the stack frame, if they affect
 // it at all. The DWARF format takes advantage of this fact, and
 // reduces the size of the data by mentioning only the addresses and
 // columns at which changes take place. So for the above, DWARF CFI
 // data would only actually mention the following:
 //
 //     insn      cfa    r0      r1 ...  ra
 //     =======================================
 //     func+0:   sp                     cfa[0]
 //     func+1:   sp+16
 //     func+2:          cfa[-4]
 //     func+11:  sp+20
 //     func+21:         r0
 //     func+22:  sp
 //
 // In fact, this is the way the parser reports CFI to the consumer: as
 // a series of statements of the form, "At address X, column Y changed
 // to Z," and related conventions for describing the initial state.
 //
 // Naturally, it would be impractical to have to scan the entire
 // program's CFI, noting changes as we go, just to recover the
 // unwinding rules in effect at one particular instruction. To avoid
 // this, CFI data is grouped into "entries", each of which covers a
 // specified range of addresses and begins with a complete statement
 // of the rules for all recoverable registers at that starting
 // address. Each entry typically covers a single function.
 //
 // Thus, to compute the contents of a given row of the table --- that
 // is, rules for recovering the CFA, RA, and registers at a given
 // instruction --- the consumer should find the entry that covers that
 // instruction's address, start with the initial state supplied at the
 // beginning of the entry, and work forward until it has processed all
 // the changes up to and including those for the present instruction.
 //
 // There are seven kinds of rules that can appear in an entry of the
 // table:
 //
 // - "undefined": The given register is not preserved by the callee;
 //   its value cannot be recovered.
 //
 // - "same value": This register has the same value it did in the callee.
 //
 // - offset(N): The register is saved at offset N from the CFA.
 //
 // - val_offset(N): The value the register had in the caller is the
 //   CFA plus offset N. (This is usually only useful for describing
 //   the stack pointer.)
 //
 // - register(R): The register's value was saved in another register R.
 //
 // - expression(E): Evaluating the DWARF expression E using the
 //   current frame's registers' values yields the address at which the
 //   register was saved.
 //
 // - val_expression(E): Evaluating the DWARF expression E using the
 //   current frame's registers' values yields the value the register
 //   had in the caller.
 class CallFrameInfo {
  public:
   // The different kinds of entries one finds in CFI. Used internally,
   // and for error reporting.
   enum EntryKind { kUnknown, kCIE, kFDE, kTerminator };
   // The handler class to which the parser hands the parsed call frame
   // information.  Defined below.
   class Handler;
   // A reporter class, which CallFrameInfo uses to report errors
   // encountered while parsing call frame information.  Defined below.
   class Reporter;
   // Create a DWARF CFI parser. BUFFER points to the contents of the
   // .debug_frame section to parse; BUFFER_LENGTH is its length in bytes.
   // REPORTER is an error reporter the parser should use to report
   // problems. READER is a ByteReader instance that has the endianness and
   // address size set properly. Report the data we find to HANDLER.
   //
   // This class can also parse Linux C++ exception handling data, as found
   // in '.eh_frame' sections. This data is a variant of DWARF CFI that is
   // placed in loadable segments so that it is present in the program's
   // address space, and is interpreted by the C++ runtime to search the
   // call stack for a handler interested in the exception being thrown,
   // actually pop the frames, and find cleanup code to run.
   //
   // There are two differences between the call frame information described
   // in the DWARF standard and the exception handling data Linux places in
   // the .eh_frame section:
   //
   // - Exception handling data uses uses a different format for call frame
   //   information entry headers. The distinguished CIE id, the way FDEs
   //   refer to their CIEs, and the way the end of the series of entries is
   //   determined are all slightly different.
   //
   //   If the constructor's EH_FRAME argument is true, then the
   //   CallFrameInfo parses the entry headers as Linux C++ exception
   //   handling data. If EH_FRAME is false or omitted, the CallFrameInfo
   //   parses standard DWARF call frame information.
   //
   // - Linux C++ exception handling data uses CIE augmentation strings
   //   beginning with 'z' to specify the presence of additional data after
   //   the CIE and FDE headers and special encodings used for addresses in
   //   frame description entries.
   //
   //   CallFrameInfo can handle 'z' augmentations in either DWARF CFI or
   //   exception handling data if you have supplied READER with the base
   //   addresses needed to interpret the pointer encodings that 'z'
   //   augmentations can specify. See the ByteReader interface for details
   //   about the base addresses. See the CallFrameInfo::Handler interface
   //   for details about the additional information one might find in
   //   'z'-augmented data.
   //
   // Thus:
   //
   // - If you are parsing standard DWARF CFI, as found in a .debug_frame
   //   section, you should pass false for the EH_FRAME argument, or omit
   //   it, and you need not worry about providing READER with the
   //   additional base addresses.
   //
   // - If you want to parse Linux C++ exception handling data from a
   //   .eh_frame section, you should pass EH_FRAME as true, and call
   //   READER's Set*Base member functions before calling our Start method.
   //
   // - If you want to parse DWARF CFI that uses the 'z' augmentations
   //   (although I don't think any toolchain ever emits such data), you
   //   could pass false for EH_FRAME, but call READER's Set*Base members.
   //
   // The extensions the Linux C++ ABI makes to DWARF for exception
   // handling are described here, rather poorly:
   // http://refspecs.linux-foundation.org/LSB_4.0.0/LSB-Core-generic/LSB-Core-generic/dwarfext.html
   // http://refspecs.linux-foundation.org/LSB_4.0.0/LSB-Core-generic/LSB-Core-generic/ehframechpt.html
   //
   // The mechanics of C++ exception handling, personality routines,
   // and language-specific data areas are described here, rather nicely:
   // http://www.codesourcery.com/public/cxx-abi/abi-eh.html
   CallFrameInfo(const char *buffer, size_t buffer_length,
                 ByteReader *reader, Handler *handler, Reporter *reporter,
                 bool eh_frame = false)
       : buffer_(buffer), buffer_length_(buffer_length),
         reader_(reader), handler_(handler), reporter_(reporter),
         eh_frame_(eh_frame) { }
   ~CallFrameInfo() { }
   // Parse the entries in BUFFER, reporting what we find to HANDLER.
   // Return true if we reach the end of the section successfully, or
   // false if we encounter an error.
   bool Start();
   // Return the textual name of KIND. For error reporting.
   static const char *KindName(EntryKind kind);
  private:
   struct CIE;
   // A CFI entry, either an FDE or a CIE.
   struct Entry {
     // The starting offset of the entry in the section, for error
     // reporting.
     size_t offset;
     // The start of this entry in the buffer.
     const char *start;
     // Which kind of entry this is.
     //
     // We want to be able to use this for error reporting even while we're
     // in the midst of parsing. Error reporting code may assume that kind,
     // offset, and start fields are valid, although kind may be kUnknown.
     EntryKind kind;
     // The end of this entry's common prologue (initial length and id), and
     // the start of this entry's kind-specific fields.
     const char *fields;
     // The start of this entry's instructions.
     const char *instructions;
     // The address past the entry's last byte in the buffer. (Note that
     // since offset points to the entry's initial length field, and the
     // length field is the number of bytes after that field, this is not
     // simply buffer_ + offset + length.)
     const char *end;
     // For both DWARF CFI and .eh_frame sections, this is the CIE id in a
     // CIE, and the offset of the associated CIE in an FDE.
     uint64 id;
     // The CIE that applies to this entry, if we've parsed it. If this is a
     // CIE, then this field points to this structure.
     CIE *cie;
   };
   // A common information entry (CIE).
   struct CIE: public Entry {
     uint8 version;                      // CFI data version number
     string augmentation;                // vendor format extension markers
     uint64 code_alignment_factor;       // scale for code address adjustments
     int data_alignment_factor;          // scale for stack pointer adjustments
     unsigned return_address_register;   // which register holds the return addr
     // True if this CIE includes Linux C++ ABI 'z' augmentation data.
     bool has_z_augmentation;
     // Parsed 'z' augmentation data. These are meaningful only if
     // has_z_augmentation is true.
     bool has_z_lsda;                    // The 'z' augmentation included 'L'.
     bool has_z_personality;             // The 'z' augmentation included 'P'.
     bool has_z_signal_frame;            // The 'z' augmentation included 'S'.
     // If has_z_lsda is true, this is the encoding to be used for language-
     // specific data area pointers in FDEs.
     DwarfPointerEncoding lsda_encoding;
     // If has_z_personality is true, this is the encoding used for the
     // personality routine pointer in the augmentation data.
     DwarfPointerEncoding personality_encoding;
     // If has_z_personality is true, this is the address of the personality
     // routine --- or, if personality_encoding & DW_EH_PE_indirect, the
     // address where the personality routine's address is stored.
     uint64 personality_address;
     // This is the encoding used for addresses in the FDE header and
     // in DW_CFA_set_loc instructions. This is always valid, whether
     // or not we saw a 'z' augmentation string; its default value is
     // DW_EH_PE_absptr, which is what normal DWARF CFI uses.
     DwarfPointerEncoding pointer_encoding;
   };
   // A frame description entry (FDE).
   struct FDE: public Entry {
     uint64 address;                     // start address of described code
     uint64 size;                        // size of described code, in bytes
     // If cie->has_z_lsda is true, then this is the language-specific data
     // area's address --- or its address's address, if cie->lsda_encoding
     // has the DW_EH_PE_indirect bit set.
     uint64 lsda_address;
   };
   // Internal use.
   class Rule;
   class UndefinedRule;
   class SameValueRule;
   class OffsetRule;
   class ValOffsetRule;
   class RegisterRule;
   class ExpressionRule;
   class ValExpressionRule;
   class RuleMap;
   class State;
   // Parse the initial length and id of a CFI entry, either a CIE, an FDE,
   // or a .eh_frame end-of-data mark. CURSOR points to the beginning of the
   // data to parse. On success, populate ENTRY as appropriate, and return
   // true. On failure, report the problem, and return false. Even if we
   // return false, set ENTRY->end to the first byte after the entry if we
   // were able to figure that out, or NULL if we weren't.
   bool ReadEntryPrologue(const char *cursor, Entry *entry);
   // Parse the fields of a CIE after the entry prologue, including any 'z'
   // augmentation data. Assume that the 'Entry' fields of CIE are
   // populated; use CIE->fields and CIE->end as the start and limit for
   // parsing. On success, populate the rest of *CIE, and return true; on
   // failure, report the problem and return false.
   bool ReadCIEFields(CIE *cie);
   // Parse the fields of an FDE after the entry prologue, including any 'z'
   // augmentation data. Assume that the 'Entry' fields of *FDE are
   // initialized; use FDE->fields and FDE->end as the start and limit for
   // parsing. Assume that FDE->cie is fully initialized. On success,
   // populate the rest of *FDE, and return true; on failure, report the
   // problem and return false.
   bool ReadFDEFields(FDE *fde);
   // Report that ENTRY is incomplete, and return false. This is just a
   // trivial wrapper for invoking reporter_->Incomplete; it provides a
   // little brevity.
   bool ReportIncomplete(Entry *entry);
   // Return true if ENCODING has the DW_EH_PE_indirect bit set.
   static bool IsIndirectEncoding(DwarfPointerEncoding encoding) {
     return encoding & DW_EH_PE_indirect;
   }
   // The contents of the DWARF .debug_info section we're parsing.
   const char *buffer_;
   size_t buffer_length_;
   // For reading multi-byte values with the appropriate endianness.
   ByteReader *reader_;
   // The handler to which we should report the data we find.
   Handler *handler_;
   // For reporting problems in the info we're parsing.
   Reporter *reporter_;
   // True if we are processing .eh_frame-format data.
   bool eh_frame_;
 };
 // The handler class for CallFrameInfo.  The a CFI parser calls the
 // member functions of a handler object to report the data it finds.
 class CallFrameInfo::Handler {
  public:
   // The pseudo-register number for the canonical frame address.
   enum { kCFARegister = -1 };
   Handler() { }
   virtual ~Handler() { }
   // The parser has found CFI for the machine code at ADDRESS,
   // extending for LENGTH bytes. OFFSET is the offset of the frame
   // description entry in the section, for use in error messages.
   // VERSION is the version number of the CFI format. AUGMENTATION is
   // a string describing any producer-specific extensions present in
   // the data. RETURN_ADDRESS is the number of the register that holds
   // the address to which the function should return.
   //
   // Entry should return true to process this CFI, or false to skip to
   // the next entry.
   //
   // The parser invokes Entry for each Frame Description Entry (FDE)
   // it finds.  The parser doesn't report Common Information Entries
   // to the handler explicitly; instead, if the handler elects to
   // process a given FDE, the parser reiterates the appropriate CIE's
   // contents at the beginning of the FDE's rules.
   virtual bool Entry(size_t offset, uint64 address, uint64 length,
                      uint8 version, const string &augmentation,
                      unsigned return_address) = 0;
   // When the Entry function returns true, the parser calls these
   // handler functions repeatedly to describe the rules for recovering
   // registers at each instruction in the given range of machine code.
   // Immediately after a call to Entry, the handler should assume that
   // the rule for each callee-saves register is "unchanged" --- that
   // is, that the register still has the value it had in the caller.
   //
   // If a *Rule function returns true, we continue processing this entry's
   // instructions. If a *Rule function returns false, we stop evaluating
   // instructions, and skip to the next entry. Either way, we call End
   // before going on to the next entry.
   //
   // In all of these functions, if the REG parameter is kCFARegister, then
   // the rule describes how to find the canonical frame address.
   // kCFARegister may be passed as a BASE_REGISTER argument, meaning that
   // the canonical frame address should be used as the base address for the
   // computation. All other REG values will be positive.
   // At ADDRESS, register REG's value is not recoverable.
   virtual bool UndefinedRule(uint64 address, int reg) = 0;
   // At ADDRESS, register REG's value is the same as that it had in
   // the caller.
   virtual bool SameValueRule(uint64 address, int reg) = 0;
   // At ADDRESS, register REG has been saved at offset OFFSET from
   // BASE_REGISTER.
   virtual bool OffsetRule(uint64 address, int reg,
                           int base_register, long offset) = 0;
   // At ADDRESS, the caller's value of register REG is the current
   // value of BASE_REGISTER plus OFFSET. (This rule doesn't provide an
   // address at which the register's value is saved.)
   virtual bool ValOffsetRule(uint64 address, int reg,
                              int base_register, long offset) = 0;
   // At ADDRESS, register REG has been saved in BASE_REGISTER. This differs
   // from ValOffsetRule(ADDRESS, REG, BASE_REGISTER, 0), in that
   // BASE_REGISTER is the "home" for REG's saved value: if you want to
   // assign to a variable whose home is REG in the calling frame, you
   // should put the value in BASE_REGISTER.
   virtual bool RegisterRule(uint64 address, int reg, int base_register) = 0;
   // At ADDRESS, the DWARF expression EXPRESSION yields the address at
   // which REG was saved.
   virtual bool ExpressionRule(uint64 address, int reg,
                               const string &expression) = 0;
   // At ADDRESS, the DWARF expression EXPRESSION yields the caller's
   // value for REG. (This rule doesn't provide an address at which the
   // register's value is saved.)
   virtual bool ValExpressionRule(uint64 address, int reg,
                                  const string &expression) = 0;
   // Indicate that the rules for the address range reported by the
   // last call to Entry are complete.  End should return true if
   // everything is okay, or false if an error has occurred and parsing
   // should stop.
   virtual bool End() = 0;
   // Handler functions for Linux C++ exception handling data. These are
   // only called if the data includes 'z' augmentation strings.
   // The Linux C++ ABI uses an extension of the DWARF CFI format to
   // walk the stack to propagate exceptions from the throw to the
   // appropriate catch, and do the appropriate cleanups along the way.
   // CFI entries used for exception handling have two additional data
   // associated with them:
   //
   // - The "language-specific data area" describes which exception
   //   types the function has 'catch' clauses for, and indicates how
   //   to go about re-entering the function at the appropriate catch
   //   clause. If the exception is not caught, it describes the
   //   destructors that must run before the frame is popped.
   //
   // - The "personality routine" is responsible for interpreting the
   //   language-specific data area's contents, and deciding whether
   //   the exception should continue to propagate down the stack,
   //   perhaps after doing some cleanup for this frame, or whether the
   //   exception will be caught here.
   //
   // In principle, the language-specific data area is opaque to
   // everybody but the personality routine. In practice, these values
   // may be useful or interesting to readers with extra context, and
   // we have to at least skip them anyway, so we might as well report
   // them to the handler.
   // This entry's exception handling personality routine's address is
   // ADDRESS. If INDIRECT is true, then ADDRESS is the address at
   // which the routine's address is stored. The default definition for
   // this handler function simply returns true, allowing parsing of
   // the entry to continue.
   virtual bool PersonalityRoutine(uint64 address, bool indirect) {
     return true;
   }
   // This entry's language-specific data area (LSDA) is located at
   // ADDRESS. If INDIRECT is true, then ADDRESS is the address at
   // which the area's address is stored. The default definition for
   // this handler function simply returns true, allowing parsing of
   // the entry to continue.
   virtual bool LanguageSpecificDataArea(uint64 address, bool indirect) {
     return true;
   }
   // This entry describes a signal trampoline --- this frame is the
   // caller of a signal handler. The default definition for this
   // handler function simply returns true, allowing parsing of the
   // entry to continue.
   //
   // The best description of the rationale for and meaning of signal
   // trampoline CFI entries seems to be in the GCC bug database:
   // http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26208
   virtual bool SignalHandler() { return true; }
 };
 // The CallFrameInfo class makes calls on an instance of this class to
 // report errors or warn about problems in the data it is parsing. The
 // default definitions of these methods print a message to stderr, but
 // you can make a derived class that overrides them.
 class CallFrameInfo::Reporter {
  public:
   // Create an error reporter which attributes troubles to the section
   // named SECTION in FILENAME.
   //
   // Normally SECTION would be .debug_frame, but the Mac puts CFI data
   // in a Mach-O section named __debug_frame. If we support
   // Linux-style exception handling data, we could be reading an
   // .eh_frame section.
   Reporter(const string &filename,
            const string &section = ".debug_frame")
       : filename_(filename), section_(section) { }
   virtual ~Reporter() { }
   // The CFI entry at OFFSET ends too early to be well-formed. KIND
   // indicates what kind of entry it is; KIND can be kUnknown if we
   // haven't parsed enough of the entry to tell yet.
   virtual void Incomplete(uint64 offset, CallFrameInfo::EntryKind kind);
   // The .eh_frame data has a four-byte zero at OFFSET where the next
   // entry's length would be; this is a terminator. However, the buffer
   // length as given to the CallFrameInfo constructor says there should be
   // more data.
   virtual void EarlyEHTerminator(uint64 offset);
   // The FDE at OFFSET refers to the CIE at CIE_OFFSET, but the
   // section is not that large.
   virtual void CIEPointerOutOfRange(uint64 offset, uint64 cie_offset);
   // The FDE at OFFSET refers to the CIE at CIE_OFFSET, but the entry
   // there is not a CIE.
   virtual void BadCIEId(uint64 offset, uint64 cie_offset);
   // The FDE at OFFSET refers to a CIE with version number VERSION,
   // which we don't recognize. We cannot parse DWARF CFI if it uses
   // a version number we don't recognize.
   virtual void UnrecognizedVersion(uint64 offset, int version);
   // The FDE at OFFSET refers to a CIE with augmentation AUGMENTATION,
   // which we don't recognize. We cannot parse DWARF CFI if it uses
   // augmentations we don't recognize.
   virtual void UnrecognizedAugmentation(uint64 offset,
                                         const string &augmentation);
   // The pointer encoding ENCODING, specified by the CIE at OFFSET, is not
   // a valid encoding.
   virtual void InvalidPointerEncoding(uint64 offset, uint8 encoding);
   // The pointer encoding ENCODING, specified by the CIE at OFFSET, depends
   // on a base address which has not been supplied.
   virtual void UnusablePointerEncoding(uint64 offset, uint8 encoding);
   // The CIE at OFFSET contains a DW_CFA_restore instruction at
   // INSN_OFFSET, which may not appear in a CIE.
   virtual void RestoreInCIE(uint64 offset, uint64 insn_offset);
   // The entry at OFFSET, of kind KIND, has an unrecognized
   // instruction at INSN_OFFSET.
   virtual void BadInstruction(uint64 offset, CallFrameInfo::EntryKind kind,
                               uint64 insn_offset);
   // The instruction at INSN_OFFSET in the entry at OFFSET, of kind
   // KIND, establishes a rule that cites the CFA, but we have not
   // established a CFA rule yet.
   virtual void NoCFARule(uint64 offset, CallFrameInfo::EntryKind kind,
                          uint64 insn_offset);
   // The instruction at INSN_OFFSET in the entry at OFFSET, of kind
   // KIND, is a DW_CFA_restore_state instruction, but the stack of
   // saved states is empty.
   virtual void EmptyStateStack(uint64 offset, CallFrameInfo::EntryKind kind,
                                uint64 insn_offset);
   // The DW_CFA_remember_state instruction at INSN_OFFSET in the entry
   // at OFFSET, of kind KIND, would restore a state that has no CFA
   // rule, whereas the current state does have a CFA rule. This is
   // bogus input, which the CallFrameInfo::Handler interface doesn't
   // (and shouldn't) have any way to report.
   virtual void ClearingCFARule(uint64 offset, CallFrameInfo::EntryKind kind,
                                uint64 insn_offset);
  protected:
   // The name of the file whose CFI we're reading.
   string filename_;
   // The name of the CFI section in that file.
   string section_;
 };
 }  // namespace dwarf2reader
 #endif  // UTIL_DEBUGINFO_DWARF2READER_H__

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toolkit/crashreporter/google-breakpad/src/common/dwarf/dwarf2reader.h@129ffea94266 (annotated)

toolkit/crashreporter/google-breakpad/src/common/dwarf/dwarf2reader.h