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 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

 /* vim: set ts=8 sts=2 et sw=2 tw=80: */

 // Copyright 2006, 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>

 // This file is derived from the following files in

 // toolkit/crashreporter/google-breakpad:

 //   src/common/dwarf/types.h

 //   src/common/dwarf/dwarf2enums.h

 //   src/common/dwarf/bytereader.h

 //   src/common/dwarf_cfi_to_module.h

 //   src/common/dwarf/dwarf2reader.h

 #ifndef LulDwarfExt_h

 #define LulDwarfExt_h

 #include <stdint.h>

 #include "mozilla/Assertions.h"

 #include "LulDwarfSummariser.h"

 typedef signed char         int8;

 typedef short               int16;

 typedef int                 int32;

 typedef long long           int64;

 typedef unsigned char      uint8;

 typedef unsigned short     uint16;

 typedef unsigned int       uint32;

 typedef unsigned long long uint64;

 #ifdef __PTRDIFF_TYPE__

 typedef          __PTRDIFF_TYPE__ intptr;

 typedef unsigned __PTRDIFF_TYPE__ uintptr;

 #else

 #error "Can't find pointer-sized integral types."

 #endif

 namespace lul {

 // Exception handling frame description pointer formats, as described

 // by the Linux Standard Base Core Specification 4.0, section 11.5,

 // DWARF Extensions.

 enum DwarfPointerEncoding

   {

     DW_EH_PE_absptr	= 0x00,

     DW_EH_PE_omit	= 0xff,

     DW_EH_PE_uleb128    = 0x01,

     DW_EH_PE_udata2	= 0x02,

     DW_EH_PE_udata4	= 0x03,

     DW_EH_PE_udata8	= 0x04,

     DW_EH_PE_sleb128    = 0x09,

     DW_EH_PE_sdata2	= 0x0A,

     DW_EH_PE_sdata4	= 0x0B,

     DW_EH_PE_sdata8	= 0x0C,

     DW_EH_PE_pcrel	= 0x10,

     DW_EH_PE_textrel	= 0x20,

     DW_EH_PE_datarel	= 0x30,

     DW_EH_PE_funcrel	= 0x40,

     DW_EH_PE_aligned	= 0x50,

     // The GNU toolchain sources define this enum value as well,

     // simply to help classify the lower nybble values into signed and

     // unsigned groups.

     DW_EH_PE_signed	= 0x08,

     // This is not documented in LSB 4.0, but it is used in both the

     // Linux and OS X toolchains. It can be added to any other

     // encoding (except DW_EH_PE_aligned), and indicates that the

     // encoded value represents the address at which the true address

     // is stored, not the true address itself.

     DW_EH_PE_indirect	= 0x80

   };

 // We can't use the obvious name of LITTLE_ENDIAN and BIG_ENDIAN

 // because it conflicts with a macro

 enum Endianness {

   ENDIANNESS_BIG,

   ENDIANNESS_LITTLE

 };

 // A ByteReader knows how to read single- and multi-byte values of

 // various endiannesses, sizes, and encodings, as used in DWARF

 // debugging information and Linux C++ exception handling data.

 class ByteReader {

  public:

   // Construct a ByteReader capable of reading one-, two-, four-, and

   // eight-byte values according to ENDIANNESS, absolute machine-sized

   // addresses, DWARF-style "initial length" values, signed and

   // unsigned LEB128 numbers, and Linux C++ exception handling data's

   // encoded pointers.

   explicit ByteReader(enum Endianness endianness);

   virtual ~ByteReader();

   // Read a single byte from BUFFER and return it as an unsigned 8 bit

   // number.

   uint8 ReadOneByte(const char* buffer) const;

   // Read two bytes from BUFFER and return them as an unsigned 16 bit

   // number, using this ByteReader's endianness.

   uint16 ReadTwoBytes(const char* buffer) const;

   // Read four bytes from BUFFER and return them as an unsigned 32 bit

   // number, using this ByteReader's endianness. This function returns

   // a uint64 so that it is compatible with ReadAddress and

   // ReadOffset. The number it returns will never be outside the range

   // of an unsigned 32 bit integer.

   uint64 ReadFourBytes(const char* buffer) const;

   // Read eight bytes from BUFFER and return them as an unsigned 64

   // bit number, using this ByteReader's endianness.

   uint64 ReadEightBytes(const char* buffer) const;

   // Read an unsigned LEB128 (Little Endian Base 128) number from

   // BUFFER and return it as an unsigned 64 bit integer. Set LEN to

   // the number of bytes read.

   //

   // The unsigned LEB128 representation of an integer N is a variable

   // number of bytes:

   //

   // - If N is between 0 and 0x7f, then its unsigned LEB128

   //   representation is a single byte whose value is N.

   //

   // - Otherwise, its unsigned LEB128 representation is (N & 0x7f) |

   //   0x80, followed by the unsigned LEB128 representation of N /

   //   128, rounded towards negative infinity.

   //

   // In other words, we break VALUE into groups of seven bits, put

   // them in little-endian order, and then write them as eight-bit

   // bytes with the high bit on all but the last.

   uint64 ReadUnsignedLEB128(const char* buffer, size_t* len) const;

   // Read a signed LEB128 number from BUFFER and return it as an

   // signed 64 bit integer. Set LEN to the number of bytes read.

   //

   // The signed LEB128 representation of an integer N is a variable

   // number of bytes:

   //

   // - If N is between -0x40 and 0x3f, then its signed LEB128

   //   representation is a single byte whose value is N in two's

   //   complement.

   //

   // - Otherwise, its signed LEB128 representation is (N & 0x7f) |

   //   0x80, followed by the signed LEB128 representation of N / 128,

   //   rounded towards negative infinity.

   //

   // In other words, we break VALUE into groups of seven bits, put

   // them in little-endian order, and then write them as eight-bit

   // bytes with the high bit on all but the last.

   int64 ReadSignedLEB128(const char* buffer, size_t* len) const;

   // Indicate that addresses on this architecture are SIZE bytes long. SIZE

   // must be either 4 or 8. (DWARF allows addresses to be any number of

   // bytes in length from 1 to 255, but we only support 32- and 64-bit

   // addresses at the moment.) You must call this before using the

   // ReadAddress member function.

   //

   // For data in a .debug_info section, or something that .debug_info

   // refers to like line number or macro data, the compilation unit

   // header's address_size field indicates the address size to use. Call

   // frame information doesn't indicate its address size (a shortcoming of

   // the spec); you must supply the appropriate size based on the

   // architecture of the target machine.

   void SetAddressSize(uint8 size);

   // Return the current address size, in bytes. This is either 4,

   // indicating 32-bit addresses, or 8, indicating 64-bit addresses.

   uint8 AddressSize() const { return address_size_; }

   // Read an address from BUFFER and return it as an unsigned 64 bit

   // integer, respecting this ByteReader's endianness and address size. You

   // must call SetAddressSize before calling this function.

   uint64 ReadAddress(const char* buffer) const;

   // DWARF actually defines two slightly different formats: 32-bit DWARF

   // and 64-bit DWARF. This is *not* related to the size of registers or

   // addresses on the target machine; it refers only to the size of section

   // offsets and data lengths appearing in the DWARF data. One only needs

   // 64-bit DWARF when the debugging data itself is larger than 4GiB.

   // 32-bit DWARF can handle x86_64 or PPC64 code just fine, unless the

   // debugging data itself is very large.

   //

   // DWARF information identifies itself as 32-bit or 64-bit DWARF: each

   // compilation unit and call frame information entry begins with an

   // "initial length" field, which, in addition to giving the length of the

   // data, also indicates the size of section offsets and lengths appearing

   // in that data. The ReadInitialLength member function, below, reads an

   // initial length and sets the ByteReader's offset size as a side effect.

   // Thus, in the normal process of reading DWARF data, the appropriate

   // offset size is set automatically. So, you should only need to call

   // SetOffsetSize if you are using the same ByteReader to jump from the

   // midst of one block of DWARF data into another.

   // Read a DWARF "initial length" field from START, and return it as

   // an unsigned 64 bit integer, respecting this ByteReader's

   // endianness. Set *LEN to the length of the initial length in

   // bytes, either four or twelve. As a side effect, set this

   // ByteReader's offset size to either 4 (if we see a 32-bit DWARF

   // initial length) or 8 (if we see a 64-bit DWARF initial length).

   //

   // A DWARF initial length is either:

   //

   // - a byte count stored as an unsigned 32-bit value less than

   //   0xffffff00, indicating that the data whose length is being

   //   measured uses the 32-bit DWARF format, or

   //

   // - The 32-bit value 0xffffffff, followed by a 64-bit byte count,

   //   indicating that the data whose length is being measured uses

   //   the 64-bit DWARF format.

   uint64 ReadInitialLength(const char* start, size_t* len);

   // Read an offset from BUFFER and return it as an unsigned 64 bit

   // integer, respecting the ByteReader's endianness. In 32-bit DWARF, the

   // offset is 4 bytes long; in 64-bit DWARF, the offset is eight bytes

   // long. You must call ReadInitialLength or SetOffsetSize before calling

   // this function; see the comments above for details.

   uint64 ReadOffset(const char* buffer) const;

   // Return the current offset size, in bytes.

   // A return value of 4 indicates that we are reading 32-bit DWARF.

   // A return value of 8 indicates that we are reading 64-bit DWARF.

   uint8 OffsetSize() const { return offset_size_; }

   // Indicate that section offsets and lengths are SIZE bytes long. SIZE

   // must be either 4 (meaning 32-bit DWARF) or 8 (meaning 64-bit DWARF).

   // Usually, you should not call this function yourself; instead, let a

   // call to ReadInitialLength establish the data's offset size

   // automatically.

   void SetOffsetSize(uint8 size);

   // The Linux C++ ABI uses a variant of DWARF call frame information

   // for exception handling. This data is included in the program's

   // address space as the ".eh_frame" section, and intepreted at

   // runtime to walk the stack, find exception handlers, and run

   // cleanup code. The format is mostly the same as DWARF CFI, with

   // some adjustments made to provide the additional

   // exception-handling data, and to make the data easier to work with

   // in memory --- for example, to allow it to be placed in read-only

   // memory even when describing position-independent code.

   //

   // In particular, exception handling data can select a number of

   // different encodings for pointers that appear in the data, as

   // described by the DwarfPointerEncoding enum. There are actually

   // four axes(!) to the encoding:

   //

   // - The pointer size: pointers can be 2, 4, or 8 bytes long, or use

   //   the DWARF LEB128 encoding.

   //

   // - The pointer's signedness: pointers can be signed or unsigned.

   //

   // - The pointer's base address: the data stored in the exception

   //   handling data can be the actual address (that is, an absolute

   //   pointer), or relative to one of a number of different base

   //   addreses --- including that of the encoded pointer itself, for

   //   a form of "pc-relative" addressing.

   //

   // - The pointer may be indirect: it may be the address where the

   //   true pointer is stored. (This is used to refer to things via

   //   global offset table entries, program linkage table entries, or

   //   other tricks used in position-independent code.)

   //

   // There are also two options that fall outside that matrix

   // altogether: the pointer may be omitted, or it may have padding to

   // align it on an appropriate address boundary. (That last option

   // may seem like it should be just another axis, but it is not.)

   // Indicate that the exception handling data is loaded starting at

   // SECTION_BASE, and that the start of its buffer in our own memory

   // is BUFFER_BASE. This allows us to find the address that a given

   // byte in our buffer would have when loaded into the program the

   // data describes. We need this to resolve DW_EH_PE_pcrel pointers.

   void SetCFIDataBase(uint64 section_base, const char *buffer_base);

   // Indicate that the base address of the program's ".text" section

   // is TEXT_BASE. We need this to resolve DW_EH_PE_textrel pointers.

   void SetTextBase(uint64 text_base);

   // Indicate that the base address for DW_EH_PE_datarel pointers is

   // DATA_BASE. The proper value depends on the ABI; it is usually the

   // address of the global offset table, held in a designated register in

   // position-independent code. You will need to look at the startup code

   // for the target system to be sure. I tried; my eyes bled.

   void SetDataBase(uint64 data_base);

   // Indicate that the base address for the FDE we are processing is

   // FUNCTION_BASE. This is the start address of DW_EH_PE_funcrel

   // pointers. (This encoding does not seem to be used by the GNU

   // toolchain.)

   void SetFunctionBase(uint64 function_base);

   // Indicate that we are no longer processing any FDE, so any use of

   // a DW_EH_PE_funcrel encoding is an error.

   void ClearFunctionBase();

   // Return true if ENCODING is a valid pointer encoding.

   bool ValidEncoding(DwarfPointerEncoding encoding) const;

   // Return true if we have all the information we need to read a

   // pointer that uses ENCODING. This checks that the appropriate

   // SetFooBase function for ENCODING has been called.

   bool UsableEncoding(DwarfPointerEncoding encoding) const;

   // Read an encoded pointer from BUFFER using ENCODING; return the

   // absolute address it represents, and set *LEN to the pointer's

   // length in bytes, including any padding for aligned pointers.

   //

   // This function calls 'abort' if ENCODING is invalid or refers to a

   // base address this reader hasn't been given, so you should check

   // with ValidEncoding and UsableEncoding first if you would rather

   // die in a more helpful way.

   uint64 ReadEncodedPointer(const char *buffer, DwarfPointerEncoding encoding,

                             size_t *len) const;

  private:

   // Function pointer type for our address and offset readers.

   typedef uint64 (ByteReader::*AddressReader)(const char*) const;

   // Read an offset from BUFFER and return it as an unsigned 64 bit

   // integer.  DWARF2/3 define offsets as either 4 or 8 bytes,

   // generally depending on the amount of DWARF2/3 info present.

   // This function pointer gets set by SetOffsetSize.

   AddressReader offset_reader_;

   // Read an address from BUFFER and return it as an unsigned 64 bit

   // integer.  DWARF2/3 allow addresses to be any size from 0-255

   // bytes currently.  Internally we support 4 and 8 byte addresses,

   // and will CHECK on anything else.

   // This function pointer gets set by SetAddressSize.

   AddressReader address_reader_;

   Endianness endian_;

   uint8 address_size_;

   uint8 offset_size_;

   // Base addresses for Linux C++ exception handling data's encoded pointers.

   bool have_section_base_, have_text_base_, have_data_base_;

   bool have_function_base_;

   uint64 section_base_;

   uint64 text_base_, data_base_, function_base_;

   const char *buffer_base_;

 };

 inline uint8 ByteReader::ReadOneByte(const char* buffer) const {

   return buffer[0];

 }

 inline uint16 ByteReader::ReadTwoBytes(const char* signed_buffer) const {

   const unsigned char *buffer

     = reinterpret_cast<const unsigned char *>(signed_buffer);

   const uint16 buffer0 = buffer[0];

   const uint16 buffer1 = buffer[1];

   if (endian_ == ENDIANNESS_LITTLE) {

     return buffer0 | buffer1 << 8;

   } else {

     return buffer1 | buffer0 << 8;

   }

 }

 inline uint64 ByteReader::ReadFourBytes(const char* signed_buffer) const {

   const unsigned char *buffer

     = reinterpret_cast<const unsigned char *>(signed_buffer);

   const uint32 buffer0 = buffer[0];

   const uint32 buffer1 = buffer[1];

   const uint32 buffer2 = buffer[2];

   const uint32 buffer3 = buffer[3];

   if (endian_ == ENDIANNESS_LITTLE) {

     return buffer0 | buffer1 << 8 | buffer2 << 16 | buffer3 << 24;

   } else {

     return buffer3 | buffer2 << 8 | buffer1 << 16 | buffer0 << 24;

   }

 }

 inline uint64 ByteReader::ReadEightBytes(const char* signed_buffer) const {

   const unsigned char *buffer

     = reinterpret_cast<const unsigned char *>(signed_buffer);

   const uint64 buffer0 = buffer[0];

   const uint64 buffer1 = buffer[1];

   const uint64 buffer2 = buffer[2];

   const uint64 buffer3 = buffer[3];

   const uint64 buffer4 = buffer[4];

   const uint64 buffer5 = buffer[5];

   const uint64 buffer6 = buffer[6];

   const uint64 buffer7 = buffer[7];

   if (endian_ == ENDIANNESS_LITTLE) {

     return buffer0 | buffer1 << 8 | buffer2 << 16 | buffer3 << 24 |

       buffer4 << 32 | buffer5 << 40 | buffer6 << 48 | buffer7 << 56;

   } else {

     return buffer7 | buffer6 << 8 | buffer5 << 16 | buffer4 << 24 |

       buffer3 << 32 | buffer2 << 40 | buffer1 << 48 | buffer0 << 56;

   }

 }

 // Read an unsigned LEB128 number.  Each byte contains 7 bits of

 // information, plus one bit saying whether the number continues or

 // not.

 inline uint64 ByteReader::ReadUnsignedLEB128(const char* buffer,

                                              size_t* len) const {

   uint64 result = 0;

   size_t num_read = 0;

   unsigned int shift = 0;

   unsigned char byte;

   do {

     byte = *buffer++;

     num_read++;

     result |= (static_cast<uint64>(byte & 0x7f)) << shift;

     shift += 7;

   } while (byte & 0x80);

   *len = num_read;

   return result;

 }

 // Read a signed LEB128 number.  These are like regular LEB128

 // numbers, except the last byte may have a sign bit set.

 inline int64 ByteReader::ReadSignedLEB128(const char* buffer,

                                           size_t* len) const {

   int64 result = 0;

   unsigned int shift = 0;

   size_t num_read = 0;

   unsigned char byte;

   do {

       byte = *buffer++;

       num_read++;

       result |= (static_cast<uint64>(byte & 0x7f) << shift);

       shift += 7;

   } while (byte & 0x80);

   if ((shift < 8 * sizeof (result)) && (byte & 0x40))

     result |= -((static_cast<int64>(1)) << shift);

   *len = num_read;

   return result;

 }

 inline uint64 ByteReader::ReadOffset(const char* buffer) const {

   MOZ_ASSERT(this->offset_reader_);

   return (this->*offset_reader_)(buffer);

 }

 inline uint64 ByteReader::ReadAddress(const char* buffer) const {

   MOZ_ASSERT(this->address_reader_);

   return (this->*address_reader_)(buffer);

 }

 inline void ByteReader::SetCFIDataBase(uint64 section_base,

                                        const char *buffer_base) {

   section_base_ = section_base;

   buffer_base_ = buffer_base;

   have_section_base_ = true;

 }

 inline void ByteReader::SetTextBase(uint64 text_base) {

   text_base_ = text_base;

   have_text_base_ = true;

 }

 inline void ByteReader::SetDataBase(uint64 data_base) {

   data_base_ = data_base;

   have_data_base_ = true;

 }

 inline void ByteReader::SetFunctionBase(uint64 function_base) {

   function_base_ = function_base;

   have_function_base_ = true;

 }

 inline void ByteReader::ClearFunctionBase() {

   have_function_base_ = false;

 }

 // (derived from)

 // dwarf_cfi_to_module.h: Define the DwarfCFIToModule class, which

 // accepts parsed DWARF call frame info and adds it to a Summariser object.

 // 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

     std::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 = DW_REG_CFA };

   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 std::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 std::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 std::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.

 // These messages are sent to the message sink |aLog| provided to the

 // constructor.

 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(void (*aLog)(const char*),

            const std::string &filename,

            const std::string &section = ".debug_frame")

       : log_(aLog), 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 std::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);

  private:

   // A logging sink function, as supplied by LUL's user.

   void (*log_)(const char*);

  protected:

   // The name of the file whose CFI we're reading.

   std::string filename_;

   // The name of the CFI section in that file.

   std::string section_;

 };

 using lul::CallFrameInfo;

 using lul::Summariser;

 // A class that accepts parsed call frame information from the DWARF

 // CFI parser and populates a google_breakpad::Module object with the

 // contents.

 class DwarfCFIToModule: public CallFrameInfo::Handler {

  public:

   // DwarfCFIToModule uses an instance of this class to report errors

   // detected while converting DWARF CFI to Breakpad STACK CFI records.

   class Reporter {

    public:

     // Create a reporter that writes messages to the message sink

     // |aLog|. FILE is the name of the file we're processing, and

     // SECTION is the name of the section within that file that we're

     // looking at (.debug_frame, .eh_frame, etc.).

     Reporter(void (*aLog)(const char*),

              const std::string &file, const std::string &section)

       : log_(aLog), file_(file), section_(section) { }

     virtual ~Reporter() { }

     // The DWARF CFI entry at OFFSET says that REG is undefined, but the

     // Breakpad symbol file format cannot express this.

     virtual void UndefinedNotSupported(size_t offset,

                                        const UniqueString* reg);

     // The DWARF CFI entry at OFFSET says that REG uses a DWARF

     // expression to find its value, but DwarfCFIToModule is not

     // capable of translating DWARF expressions to Breakpad postfix

     // expressions.

     virtual void ExpressionsNotSupported(size_t offset,

                                          const UniqueString* reg);

   private:

     // A logging sink function, as supplied by LUL's user.

     void (*log_)(const char*);

   protected:

     std::string file_, section_;

   };

   // Register name tables. If TABLE is a vector returned by one of these

   // functions, then TABLE[R] is the name of the register numbered R in

   // DWARF call frame information.

   class RegisterNames {

    public:

     // Intel's "x86" or IA-32.

     static const unsigned int I386();

     // AMD x86_64, AMD64, Intel EM64T, or Intel 64

     static const unsigned int X86_64();

     // ARM.

     static const unsigned int ARM();

   };

   // Create a handler for the dwarf2reader::CallFrameInfo parser that

   // records the stack unwinding information it receives in SUMM.

   //

   // Use REGISTER_NAMES[I] as the name of register number I; *this

   // keeps a reference to the vector, so the vector should remain

   // alive for as long as the DwarfCFIToModule does.

   //

   // Use REPORTER for reporting problems encountered in the conversion

   // process.

   DwarfCFIToModule(const unsigned int num_dw_regs,

                    Reporter *reporter,

                    /*OUT*/Summariser* summ)

       : summ_(summ), num_dw_regs_(num_dw_regs), reporter_(reporter),

         return_address_(-1) {

   }

   virtual ~DwarfCFIToModule() {}

   virtual bool Entry(size_t offset, uint64 address, uint64 length,

                      uint8 version, const std::string &augmentation,

                      unsigned return_address);

   virtual bool UndefinedRule(uint64 address, int reg);

   virtual bool SameValueRule(uint64 address, int reg);

   virtual bool OffsetRule(uint64 address, int reg,

                           int base_register, long offset);

   virtual bool ValOffsetRule(uint64 address, int reg,

                              int base_register, long offset);

   virtual bool RegisterRule(uint64 address, int reg, int base_register);

   virtual bool ExpressionRule(uint64 address, int reg,

                               const std::string &expression);

   virtual bool ValExpressionRule(uint64 address, int reg,

                                  const std::string &expression);

   virtual bool End();

  private:

   // Return the name to use for register REG.

   const UniqueString* RegisterName(int i);

   // The Summariser to which we should give entries

   Summariser* summ_;

   // The number of Dwarf-defined register names for this architecture.

   const unsigned int num_dw_regs_;

   // The reporter to use to report problems.

   Reporter *reporter_;

   // The section offset of the current frame description entry, for

   // use in error messages.

   size_t entry_offset_;

   // The return address column for that entry.

   unsigned return_address_;

 };

 } // namespace lul

 #endif // LulDwarfExt_h