The Tor Browser: comparison tools/profiler/LulDwarfExt.h

--1:000000000000
+:bf0884a8d641
+/* -*- 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

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