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// -*- mode: C++ -*-
// Copyright (c) 2010 Google Inc. All Rights Reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
// CFI reader author: Jim Blandy <jimb@mozilla.com> <jimb@red-bean.com>
// This file contains definitions related to the DWARF2/3 reader and
// it's handler interfaces.
// The DWARF2/3 specification can be found at
// http://dwarf.freestandards.org and should be considered required
// reading if you wish to modify the implementation.
// Only a cursory attempt is made to explain terminology that is
// used here, as it is much better explained in the standard documents
#ifndef COMMON_DWARF_DWARF2READER_H__
#define COMMON_DWARF_DWARF2READER_H__
#include <list>
#include <map>
#include <string>
#include <utility>
#include <vector>
#include "common/dwarf/bytereader.h"
#include "common/dwarf/dwarf2enums.h"
#include "common/dwarf/types.h"
using namespace std;
namespace dwarf2reader {
struct LineStateMachine;
class Dwarf2Handler;
class LineInfoHandler;
// This maps from a string naming a section to a pair containing a
// the data for the section, and the size of the section.
typedef map<string, pair<const char*, uint64> > SectionMap;
typedef list<pair<enum DwarfAttribute, enum DwarfForm> > AttributeList;
typedef AttributeList::iterator AttributeIterator;
typedef AttributeList::const_iterator ConstAttributeIterator;
struct LineInfoHeader {
uint64 total_length;
uint16 version;
uint64 prologue_length;
uint8 min_insn_length; // insn stands for instructin
bool default_is_stmt; // stmt stands for statement
int8 line_base;
uint8 line_range;
uint8 opcode_base;
// Use a pointer so that signalsafe_addr2line is able to use this structure
// without heap allocation problem.
vector<unsigned char> *std_opcode_lengths;
};
class LineInfo {
public:
// Initializes a .debug_line reader. Buffer and buffer length point
// to the beginning and length of the line information to read.
// Reader is a ByteReader class that has the endianness set
// properly.
LineInfo(const char* buffer_, uint64 buffer_length,
ByteReader* reader, LineInfoHandler* handler);
virtual ~LineInfo() {
if (header_.std_opcode_lengths) {
delete header_.std_opcode_lengths;
}
}
// Start processing line info, and calling callbacks in the handler.
// Consumes the line number information for a single compilation unit.
// Returns the number of bytes processed.
uint64 Start();
// Process a single line info opcode at START using the state
// machine at LSM. Return true if we should define a line using the
// current state of the line state machine. Place the length of the
// opcode in LEN.
// If LSM_PASSES_PC is non-NULL, this function also checks if the lsm
// passes the address of PC. In other words, LSM_PASSES_PC will be
// set to true, if the following condition is met.
//
// lsm's old address < PC <= lsm's new address
static bool ProcessOneOpcode(ByteReader* reader,
LineInfoHandler* handler,
const struct LineInfoHeader &header,
const char* start,
struct LineStateMachine* lsm,
size_t* len,
uintptr pc,
bool *lsm_passes_pc);
private:
// Reads the DWARF2/3 header for this line info.
void ReadHeader();
// Reads the DWARF2/3 line information
void ReadLines();
// The associated handler to call processing functions in
LineInfoHandler* handler_;
// The associated ByteReader that handles endianness issues for us
ByteReader* reader_;
// A DWARF2/3 line info header. This is not the same size as
// in the actual file, as the one in the file may have a 32 bit or
// 64 bit lengths
struct LineInfoHeader header_;
// buffer is the buffer for our line info, starting at exactly where
// the line info to read is. after_header is the place right after
// the end of the line information header.
const char* buffer_;
uint64 buffer_length_;
const char* after_header_;
};
// This class is the main interface between the line info reader and
// the client. The virtual functions inside this get called for
// interesting events that happen during line info reading. The
// default implementation does nothing
class LineInfoHandler {
public:
LineInfoHandler() { }
virtual ~LineInfoHandler() { }
// Called when we define a directory. NAME is the directory name,
// DIR_NUM is the directory number
virtual void DefineDir(const string& name, uint32 dir_num) { }
// Called when we define a filename. NAME is the filename, FILE_NUM
// is the file number which is -1 if the file index is the next
// index after the last numbered index (this happens when files are
// dynamically defined by the line program), DIR_NUM is the
// directory index for the directory name of this file, MOD_TIME is
// the modification time of the file, and LENGTH is the length of
// the file
virtual void DefineFile(const string& name, int32 file_num,
uint32 dir_num, uint64 mod_time,
uint64 length) { }
// Called when the line info reader has a new line, address pair
// ready for us. ADDRESS is the address of the code, LENGTH is the
// length of its machine code in bytes, FILE_NUM is the file number
// containing the code, LINE_NUM is the line number in that file for
// the code, and COLUMN_NUM is the column number the code starts at,
// if we know it (0 otherwise).
virtual void AddLine(uint64 address, uint64 length,
uint32 file_num, uint32 line_num, uint32 column_num) { }
};
// The base of DWARF2/3 debug info is a DIE (Debugging Information
// Entry.
// DWARF groups DIE's into a tree and calls the root of this tree a
// "compilation unit". Most of the time, there is one compilation
// unit in the .debug_info section for each file that had debug info
// generated.
// Each DIE consists of
// 1. a tag specifying a thing that is being described (ie
// DW_TAG_subprogram for functions, DW_TAG_variable for variables, etc
// 2. attributes (such as DW_AT_location for location in memory,
// DW_AT_name for name), and data for each attribute.
// 3. A flag saying whether the DIE has children or not
// In order to gain some amount of compression, the format of
// each DIE (tag name, attributes and data forms for the attributes)
// are stored in a separate table called the "abbreviation table".
// This is done because a large number of DIEs have the exact same tag
// and list of attributes, but different data for those attributes.
// As a result, the .debug_info section is just a stream of data, and
// requires reading of the .debug_abbrev section to say what the data
// means.
// As a warning to the user, it should be noted that the reason for
// using absolute offsets from the beginning of .debug_info is that
// DWARF2/3 supports referencing DIE's from other DIE's by their offset
// from either the current compilation unit start, *or* the beginning
// of the .debug_info section. This means it is possible to reference
// a DIE in one compilation unit from a DIE in another compilation
// unit. This style of reference is usually used to eliminate
// duplicated information that occurs across compilation
// units, such as base types, etc. GCC 3.4+ support this with
// -feliminate-dwarf2-dups. Other toolchains will sometimes do
// duplicate elimination in the linker.
class CompilationUnit {
public:
// Initialize a compilation unit. This requires a map of sections,
// the offset of this compilation unit in the .debug_info section, a
// ByteReader, and a Dwarf2Handler class to call callbacks in.
CompilationUnit(const SectionMap& sections, uint64 offset,
ByteReader* reader, Dwarf2Handler* handler);
virtual ~CompilationUnit() {
if (abbrevs_) delete abbrevs_;
}
// Begin reading a Dwarf2 compilation unit, and calling the
// callbacks in the Dwarf2Handler
// Return the full length of the compilation unit, including
// headers. This plus the starting offset passed to the constructor
// is the offset of the end of the compilation unit --- and the
// start of the next compilation unit, if there is one.
uint64 Start();
private:
// This struct represents a single DWARF2/3 abbreviation
// The abbreviation tells how to read a DWARF2/3 DIE, and consist of a
// tag and a list of attributes, as well as the data form of each attribute.
struct Abbrev {
uint64 number;
enum DwarfTag tag;
bool has_children;
AttributeList attributes;
};
// A DWARF2/3 compilation unit header. This is not the same size as
// in the actual file, as the one in the file may have a 32 bit or
// 64 bit length.
struct CompilationUnitHeader {
uint64 length;
uint16 version;
uint64 abbrev_offset;
uint8 address_size;
} header_;
// Reads the DWARF2/3 header for this compilation unit.
void ReadHeader();
// Reads the DWARF2/3 abbreviations for this compilation unit
void ReadAbbrevs();
// Processes a single DIE for this compilation unit and return a new
// pointer just past the end of it
const char* ProcessDIE(uint64 dieoffset,
const char* start,
const Abbrev& abbrev);
// Processes a single attribute and return a new pointer just past the
// end of it
const char* ProcessAttribute(uint64 dieoffset,
const char* start,
enum DwarfAttribute attr,
enum DwarfForm form);
// Processes all DIEs for this compilation unit
void ProcessDIEs();
// Skips the die with attributes specified in ABBREV starting at
// START, and return the new place to position the stream to.
const char* SkipDIE(const char* start,
const Abbrev& abbrev);
// Skips the attribute starting at START, with FORM, and return the
// new place to position the stream to.
const char* SkipAttribute(const char* start,
enum DwarfForm form);
// Offset from section start is the offset of this compilation unit
// from the beginning of the .debug_info section.
uint64 offset_from_section_start_;
// buffer is the buffer for our CU, starting at .debug_info + offset
// passed in from constructor.
// after_header points to right after the compilation unit header.
const char* buffer_;
uint64 buffer_length_;
const char* after_header_;
// The associated ByteReader that handles endianness issues for us
ByteReader* reader_;
// The map of sections in our file to buffers containing their data
const SectionMap& sections_;
// The associated handler to call processing functions in
Dwarf2Handler* handler_;
// Set of DWARF2/3 abbreviations for this compilation unit. Indexed
// by abbreviation number, which means that abbrevs_[0] is not
// valid.
vector<Abbrev>* abbrevs_;
// String section buffer and length, if we have a string section.
// This is here to avoid doing a section lookup for strings in
// ProcessAttribute, which is in the hot path for DWARF2 reading.
const char* string_buffer_;
uint64 string_buffer_length_;
};
// This class is the main interface between the reader and the
// client. The virtual functions inside this get called for
// interesting events that happen during DWARF2 reading.
// The default implementation skips everything.
class Dwarf2Handler {
public:
Dwarf2Handler() { }
virtual ~Dwarf2Handler() { }
// Start to process a compilation unit at OFFSET from the beginning of the
// .debug_info section. Return false if you would like to skip this
// compilation unit.
virtual bool StartCompilationUnit(uint64 offset, uint8 address_size,
uint8 offset_size, uint64 cu_length,
uint8 dwarf_version) { return false; }
// Start to process a DIE at OFFSET from the beginning of the .debug_info
// section. Return false if you would like to skip this DIE.
virtual bool StartDIE(uint64 offset, enum DwarfTag tag,
const AttributeList& attrs) { return false; }
// Called when we have an attribute with unsigned data to give to our
// handler. The attribute is for the DIE at OFFSET from the beginning of the
// .debug_info section. Its name is ATTR, its form is FORM, and its value is
// DATA.
virtual void ProcessAttributeUnsigned(uint64 offset,
enum DwarfAttribute attr,
enum DwarfForm form,
uint64 data) { }
// Called when we have an attribute with signed data to give to our handler.
// The attribute is for the DIE at OFFSET from the beginning of the
// .debug_info section. Its name is ATTR, its form is FORM, and its value is
// DATA.
virtual void ProcessAttributeSigned(uint64 offset,
enum DwarfAttribute attr,
enum DwarfForm form,
int64 data) { }
// Called when we have an attribute whose value is a reference to
// another DIE. The attribute belongs to the DIE at OFFSET from the
// beginning of the .debug_info section. Its name is ATTR, its form
// is FORM, and the offset of the DIE being referred to from the
// beginning of the .debug_info section is DATA.
virtual void ProcessAttributeReference(uint64 offset,
enum DwarfAttribute attr,
enum DwarfForm form,
uint64 data) { }
// Called when we have an attribute with a buffer of data to give to our
// handler. The attribute is for the DIE at OFFSET from the beginning of the
// .debug_info section. Its name is ATTR, its form is FORM, DATA points to
// the buffer's contents, and its length in bytes is LENGTH. The buffer is
// owned by the caller, not the callee, and may not persist for very long.
// If you want the data to be available later, it needs to be copied.
virtual void ProcessAttributeBuffer(uint64 offset,
enum DwarfAttribute attr,
enum DwarfForm form,
const char* data,
uint64 len) { }
// Called when we have an attribute with string data to give to our handler.
// The attribute is for the DIE at OFFSET from the beginning of the
// .debug_info section. Its name is ATTR, its form is FORM, and its value is
// DATA.
virtual void ProcessAttributeString(uint64 offset,
enum DwarfAttribute attr,
enum DwarfForm form,
const string& data) { }
// Called when finished processing the DIE at OFFSET.
// Because DWARF2/3 specifies a tree of DIEs, you may get starts
// before ends of the previous DIE, as we process children before
// ending the parent.
virtual void EndDIE(uint64 offset) { }
};
// This class is a reader for DWARF's Call Frame Information. CFI
// describes how to unwind stack frames --- even for functions that do
// not follow fixed conventions for saving registers, whose frame size
// varies as they execute, etc.
//
// CFI describes, at each machine instruction, how to compute the
// stack frame's base address, how to find the return address, and
// where to find the saved values of the caller's registers (if the
// callee has stashed them somewhere to free up the registers for its
// own use).
//
// For example, suppose we have a function whose machine code looks
// like this (imagine an assembly language that looks like C, for a
// machine with 32-bit registers, and a stack that grows towards lower
// addresses):
//
// func: ; entry point; return address at sp
// func+0: sp = sp - 16 ; allocate space for stack frame
// func+1: sp[12] = r0 ; save r0 at sp+12
// ... ; other code, not frame-related
// func+10: sp -= 4; *sp = x ; push some x on the stack
// ... ; other code, not frame-related
// func+20: r0 = sp[16] ; restore saved r0
// func+21: sp += 20 ; pop whole stack frame
// func+22: pc = *sp; sp += 4 ; pop return address and jump to it
//
// DWARF CFI is (a very compressed representation of) a table with a
// row for each machine instruction address and a column for each
// register showing how to restore it, if possible.
//
// A special column named "CFA", for "Canonical Frame Address", tells how
// to compute the base address of the frame; registers' entries may
// refer to the CFA in describing where the registers are saved.
//
// Another special column, named "RA", represents the return address.
//
// For example, here is a complete (uncompressed) table describing the
// function above:
//
// insn cfa r0 r1 ... ra
// =======================================
// func+0: sp cfa[0]
// func+1: sp+16 cfa[0]
// func+2: sp+16 cfa[-4] cfa[0]
// func+11: sp+20 cfa[-4] cfa[0]
// func+21: sp+20 cfa[0]
// func+22: sp cfa[0]
//
// Some things to note here:
//
// - Each row describes the state of affairs *before* executing the
// instruction at the given address. Thus, the row for func+0
// describes the state before we allocate the stack frame. In the
// next row, the formula for computing the CFA has changed,
// reflecting that allocation.
//
// - The other entries are written in terms of the CFA; this allows
// them to remain unchanged as the stack pointer gets bumped around.
// For example, the rule for recovering the return address (the "ra"
// column) remains unchanged throughout the function, even as the
// stack pointer takes on three different offsets from the return
// address.
//
// - Although we haven't shown it, most calling conventions designate
// "callee-saves" and "caller-saves" registers. The callee must
// preserve the values of callee-saves registers; if it uses them,
// it must save their original values somewhere, and restore them
// before it returns. In contrast, the callee is free to trash
// caller-saves registers; if the callee uses these, it will
// probably not bother to save them anywhere, and the CFI will
// probably mark their values as "unrecoverable".
//
// (However, since the caller cannot assume the callee was going to
// save them, caller-saves registers are probably dead in the caller
// anyway, so compilers usually don't generate CFA for caller-saves
// registers.)
//
// - Exactly where the CFA points is a matter of convention that
// depends on the architecture and ABI in use. In the example, the
// CFA is the value the stack pointer had upon entry to the
// function, pointing at the saved return address. But on the x86,
// the call frame information generated by GCC follows the
// convention that the CFA is the address *after* the saved return
// address.
//
// But by definition, the CFA remains constant throughout the
// lifetime of the frame. This makes it a useful value for other
// columns to refer to. It is also gives debuggers a useful handle
// for identifying a frame.
//
// If you look at the table above, you'll notice that a given entry is
// often the same as the one immediately above it: most instructions
// change only one or two aspects of the stack frame, if they affect
// it at all. The DWARF format takes advantage of this fact, and
// reduces the size of the data by mentioning only the addresses and
// columns at which changes take place. So for the above, DWARF CFI
// data would only actually mention the following:
//
// insn cfa r0 r1 ... ra
// =======================================
// func+0: sp cfa[0]
// func+1: sp+16
// func+2: cfa[-4]
// func+11: sp+20
// func+21: r0
// func+22: sp
//
// In fact, this is the way the parser reports CFI to the consumer: as
// a series of statements of the form, "At address X, column Y changed
// to Z," and related conventions for describing the initial state.
//
// Naturally, it would be impractical to have to scan the entire
// program's CFI, noting changes as we go, just to recover the
// unwinding rules in effect at one particular instruction. To avoid
// this, CFI data is grouped into "entries", each of which covers a
// specified range of addresses and begins with a complete statement
// of the rules for all recoverable registers at that starting
// address. Each entry typically covers a single function.
//
// Thus, to compute the contents of a given row of the table --- that
// is, rules for recovering the CFA, RA, and registers at a given
// instruction --- the consumer should find the entry that covers that
// instruction's address, start with the initial state supplied at the
// beginning of the entry, and work forward until it has processed all
// the changes up to and including those for the present instruction.
//
// There are seven kinds of rules that can appear in an entry of the
// table:
//
// - "undefined": The given register is not preserved by the callee;
// its value cannot be recovered.
//
// - "same value": This register has the same value it did in the callee.
//
// - offset(N): The register is saved at offset N from the CFA.
//
// - val_offset(N): The value the register had in the caller is the
// CFA plus offset N. (This is usually only useful for describing
// the stack pointer.)
//
// - register(R): The register's value was saved in another register R.
//
// - expression(E): Evaluating the DWARF expression E using the
// current frame's registers' values yields the address at which the
// register was saved.
//
// - val_expression(E): Evaluating the DWARF expression E using the
// current frame's registers' values yields the value the register
// had in the caller.
class CallFrameInfo {
public:
// The different kinds of entries one finds in CFI. Used internally,
// and for error reporting.
enum EntryKind { kUnknown, kCIE, kFDE, kTerminator };
// The handler class to which the parser hands the parsed call frame
// information. Defined below.
class Handler;
// A reporter class, which CallFrameInfo uses to report errors
// encountered while parsing call frame information. Defined below.
class Reporter;
// Create a DWARF CFI parser. BUFFER points to the contents of the
// .debug_frame section to parse; BUFFER_LENGTH is its length in bytes.
// REPORTER is an error reporter the parser should use to report
// problems. READER is a ByteReader instance that has the endianness and
// address size set properly. Report the data we find to HANDLER.
//
// This class can also parse Linux C++ exception handling data, as found
// in '.eh_frame' sections. This data is a variant of DWARF CFI that is
// placed in loadable segments so that it is present in the program's
// address space, and is interpreted by the C++ runtime to search the
// call stack for a handler interested in the exception being thrown,
// actually pop the frames, and find cleanup code to run.
//
// There are two differences between the call frame information described
// in the DWARF standard and the exception handling data Linux places in
// the .eh_frame section:
//
// - Exception handling data uses uses a different format for call frame
// information entry headers. The distinguished CIE id, the way FDEs
// refer to their CIEs, and the way the end of the series of entries is
// determined are all slightly different.
//
// If the constructor's EH_FRAME argument is true, then the
// CallFrameInfo parses the entry headers as Linux C++ exception
// handling data. If EH_FRAME is false or omitted, the CallFrameInfo
// parses standard DWARF call frame information.
//
// - Linux C++ exception handling data uses CIE augmentation strings
// beginning with 'z' to specify the presence of additional data after
// the CIE and FDE headers and special encodings used for addresses in
// frame description entries.
//
// CallFrameInfo can handle 'z' augmentations in either DWARF CFI or
// exception handling data if you have supplied READER with the base
// addresses needed to interpret the pointer encodings that 'z'
// augmentations can specify. See the ByteReader interface for details
// about the base addresses. See the CallFrameInfo::Handler interface
// for details about the additional information one might find in
// 'z'-augmented data.
//
// Thus:
//
// - If you are parsing standard DWARF CFI, as found in a .debug_frame
// section, you should pass false for the EH_FRAME argument, or omit
// it, and you need not worry about providing READER with the
// additional base addresses.
//
// - If you want to parse Linux C++ exception handling data from a
// .eh_frame section, you should pass EH_FRAME as true, and call
// READER's Set*Base member functions before calling our Start method.
//
// - If you want to parse DWARF CFI that uses the 'z' augmentations
// (although I don't think any toolchain ever emits such data), you
// could pass false for EH_FRAME, but call READER's Set*Base members.
//
// The extensions the Linux C++ ABI makes to DWARF for exception
// handling are described here, rather poorly:
// http://refspecs.linux-foundation.org/LSB_4.0.0/LSB-Core-generic/LSB-Core-generic/dwarfext.html
// http://refspecs.linux-foundation.org/LSB_4.0.0/LSB-Core-generic/LSB-Core-generic/ehframechpt.html
//
// The mechanics of C++ exception handling, personality routines,
// and language-specific data areas are described here, rather nicely:
// http://www.codesourcery.com/public/cxx-abi/abi-eh.html
CallFrameInfo(const char *buffer, size_t buffer_length,
ByteReader *reader, Handler *handler, Reporter *reporter,
bool eh_frame = false)
: buffer_(buffer), buffer_length_(buffer_length),
reader_(reader), handler_(handler), reporter_(reporter),
eh_frame_(eh_frame) { }
~CallFrameInfo() { }
// Parse the entries in BUFFER, reporting what we find to HANDLER.
// Return true if we reach the end of the section successfully, or
// false if we encounter an error.
bool Start();
// Return the textual name of KIND. For error reporting.
static const char *KindName(EntryKind kind);
private:
struct CIE;
// A CFI entry, either an FDE or a CIE.
struct Entry {
// The starting offset of the entry in the section, for error
// reporting.
size_t offset;
// The start of this entry in the buffer.
const char *start;
// Which kind of entry this is.
//
// We want to be able to use this for error reporting even while we're
// in the midst of parsing. Error reporting code may assume that kind,
// offset, and start fields are valid, although kind may be kUnknown.
EntryKind kind;
// The end of this entry's common prologue (initial length and id), and
// the start of this entry's kind-specific fields.
const char *fields;
// The start of this entry's instructions.
const char *instructions;
// The address past the entry's last byte in the buffer. (Note that
// since offset points to the entry's initial length field, and the
// length field is the number of bytes after that field, this is not
// simply buffer_ + offset + length.)
const char *end;
// For both DWARF CFI and .eh_frame sections, this is the CIE id in a
// CIE, and the offset of the associated CIE in an FDE.
uint64 id;
// The CIE that applies to this entry, if we've parsed it. If this is a
// CIE, then this field points to this structure.
CIE *cie;
};
// A common information entry (CIE).
struct CIE: public Entry {
uint8 version; // CFI data version number
string augmentation; // vendor format extension markers
uint64 code_alignment_factor; // scale for code address adjustments
int data_alignment_factor; // scale for stack pointer adjustments
unsigned return_address_register; // which register holds the return addr
// True if this CIE includes Linux C++ ABI 'z' augmentation data.
bool has_z_augmentation;
// Parsed 'z' augmentation data. These are meaningful only if
// has_z_augmentation is true.
bool has_z_lsda; // The 'z' augmentation included 'L'.
bool has_z_personality; // The 'z' augmentation included 'P'.
bool has_z_signal_frame; // The 'z' augmentation included 'S'.
// If has_z_lsda is true, this is the encoding to be used for language-
// specific data area pointers in FDEs.
DwarfPointerEncoding lsda_encoding;
// If has_z_personality is true, this is the encoding used for the
// personality routine pointer in the augmentation data.
DwarfPointerEncoding personality_encoding;
// If has_z_personality is true, this is the address of the personality
// routine --- or, if personality_encoding & DW_EH_PE_indirect, the
// address where the personality routine's address is stored.
uint64 personality_address;
// This is the encoding used for addresses in the FDE header and
// in DW_CFA_set_loc instructions. This is always valid, whether
// or not we saw a 'z' augmentation string; its default value is
// DW_EH_PE_absptr, which is what normal DWARF CFI uses.
DwarfPointerEncoding pointer_encoding;
};
// A frame description entry (FDE).
struct FDE: public Entry {
uint64 address; // start address of described code
uint64 size; // size of described code, in bytes
// If cie->has_z_lsda is true, then this is the language-specific data
// area's address --- or its address's address, if cie->lsda_encoding
// has the DW_EH_PE_indirect bit set.
uint64 lsda_address;
};
// Internal use.
class Rule;
class UndefinedRule;
class SameValueRule;
class OffsetRule;
class ValOffsetRule;
class RegisterRule;
class ExpressionRule;
class ValExpressionRule;
class RuleMap;
class State;
// Parse the initial length and id of a CFI entry, either a CIE, an FDE,
// or a .eh_frame end-of-data mark. CURSOR points to the beginning of the
// data to parse. On success, populate ENTRY as appropriate, and return
// true. On failure, report the problem, and return false. Even if we
// return false, set ENTRY->end to the first byte after the entry if we
// were able to figure that out, or NULL if we weren't.
bool ReadEntryPrologue(const char *cursor, Entry *entry);
// Parse the fields of a CIE after the entry prologue, including any 'z'
// augmentation data. Assume that the 'Entry' fields of CIE are
// populated; use CIE->fields and CIE->end as the start and limit for
// parsing. On success, populate the rest of *CIE, and return true; on
// failure, report the problem and return false.
bool ReadCIEFields(CIE *cie);
// Parse the fields of an FDE after the entry prologue, including any 'z'
// augmentation data. Assume that the 'Entry' fields of *FDE are
// initialized; use FDE->fields and FDE->end as the start and limit for
// parsing. Assume that FDE->cie is fully initialized. On success,
// populate the rest of *FDE, and return true; on failure, report the
// problem and return false.
bool ReadFDEFields(FDE *fde);
// Report that ENTRY is incomplete, and return false. This is just a
// trivial wrapper for invoking reporter_->Incomplete; it provides a
// little brevity.
bool ReportIncomplete(Entry *entry);
// Return true if ENCODING has the DW_EH_PE_indirect bit set.
static bool IsIndirectEncoding(DwarfPointerEncoding encoding) {
return encoding & DW_EH_PE_indirect;
}
// The contents of the DWARF .debug_info section we're parsing.
const char *buffer_;
size_t buffer_length_;
// For reading multi-byte values with the appropriate endianness.
ByteReader *reader_;
// The handler to which we should report the data we find.
Handler *handler_;
// For reporting problems in the info we're parsing.
Reporter *reporter_;
// True if we are processing .eh_frame-format data.
bool eh_frame_;
};
// The handler class for CallFrameInfo. The a CFI parser calls the
// member functions of a handler object to report the data it finds.
class CallFrameInfo::Handler {
public:
// The pseudo-register number for the canonical frame address.
enum { kCFARegister = -1 };
Handler() { }
virtual ~Handler() { }
// The parser has found CFI for the machine code at ADDRESS,
// extending for LENGTH bytes. OFFSET is the offset of the frame
// description entry in the section, for use in error messages.
// VERSION is the version number of the CFI format. AUGMENTATION is
// a string describing any producer-specific extensions present in
// the data. RETURN_ADDRESS is the number of the register that holds
// the address to which the function should return.
//
// Entry should return true to process this CFI, or false to skip to
// the next entry.
//
// The parser invokes Entry for each Frame Description Entry (FDE)
// it finds. The parser doesn't report Common Information Entries
// to the handler explicitly; instead, if the handler elects to
// process a given FDE, the parser reiterates the appropriate CIE's
// contents at the beginning of the FDE's rules.
virtual bool Entry(size_t offset, uint64 address, uint64 length,
uint8 version, const string &augmentation,
unsigned return_address) = 0;
// When the Entry function returns true, the parser calls these
// handler functions repeatedly to describe the rules for recovering
// registers at each instruction in the given range of machine code.
// Immediately after a call to Entry, the handler should assume that
// the rule for each callee-saves register is "unchanged" --- that
// is, that the register still has the value it had in the caller.
//
// If a *Rule function returns true, we continue processing this entry's
// instructions. If a *Rule function returns false, we stop evaluating
// instructions, and skip to the next entry. Either way, we call End
// before going on to the next entry.
//
// In all of these functions, if the REG parameter is kCFARegister, then
// the rule describes how to find the canonical frame address.
// kCFARegister may be passed as a BASE_REGISTER argument, meaning that
// the canonical frame address should be used as the base address for the
// computation. All other REG values will be positive.
// At ADDRESS, register REG's value is not recoverable.
virtual bool UndefinedRule(uint64 address, int reg) = 0;
// At ADDRESS, register REG's value is the same as that it had in
// the caller.
virtual bool SameValueRule(uint64 address, int reg) = 0;
// At ADDRESS, register REG has been saved at offset OFFSET from
// BASE_REGISTER.
virtual bool OffsetRule(uint64 address, int reg,
int base_register, long offset) = 0;
// At ADDRESS, the caller's value of register REG is the current
// value of BASE_REGISTER plus OFFSET. (This rule doesn't provide an
// address at which the register's value is saved.)
virtual bool ValOffsetRule(uint64 address, int reg,
int base_register, long offset) = 0;
// At ADDRESS, register REG has been saved in BASE_REGISTER. This differs
// from ValOffsetRule(ADDRESS, REG, BASE_REGISTER, 0), in that
// BASE_REGISTER is the "home" for REG's saved value: if you want to
// assign to a variable whose home is REG in the calling frame, you
// should put the value in BASE_REGISTER.
virtual bool RegisterRule(uint64 address, int reg, int base_register) = 0;
// At ADDRESS, the DWARF expression EXPRESSION yields the address at
// which REG was saved.
virtual bool ExpressionRule(uint64 address, int reg,
const string &expression) = 0;
// At ADDRESS, the DWARF expression EXPRESSION yields the caller's
// value for REG. (This rule doesn't provide an address at which the
// register's value is saved.)
virtual bool ValExpressionRule(uint64 address, int reg,
const string &expression) = 0;
// Indicate that the rules for the address range reported by the
// last call to Entry are complete. End should return true if
// everything is okay, or false if an error has occurred and parsing
// should stop.
virtual bool End() = 0;
// Handler functions for Linux C++ exception handling data. These are
// only called if the data includes 'z' augmentation strings.
// The Linux C++ ABI uses an extension of the DWARF CFI format to
// walk the stack to propagate exceptions from the throw to the
// appropriate catch, and do the appropriate cleanups along the way.
// CFI entries used for exception handling have two additional data
// associated with them:
//
// - The "language-specific data area" describes which exception
// types the function has 'catch' clauses for, and indicates how
// to go about re-entering the function at the appropriate catch
// clause. If the exception is not caught, it describes the
// destructors that must run before the frame is popped.
//
// - The "personality routine" is responsible for interpreting the
// language-specific data area's contents, and deciding whether
// the exception should continue to propagate down the stack,
// perhaps after doing some cleanup for this frame, or whether the
// exception will be caught here.
//
// In principle, the language-specific data area is opaque to
// everybody but the personality routine. In practice, these values
// may be useful or interesting to readers with extra context, and
// we have to at least skip them anyway, so we might as well report
// them to the handler.
// This entry's exception handling personality routine's address is
// ADDRESS. If INDIRECT is true, then ADDRESS is the address at
// which the routine's address is stored. The default definition for
// this handler function simply returns true, allowing parsing of
// the entry to continue.
virtual bool PersonalityRoutine(uint64 address, bool indirect) {
return true;
}
// This entry's language-specific data area (LSDA) is located at
// ADDRESS. If INDIRECT is true, then ADDRESS is the address at
// which the area's address is stored. The default definition for
// this handler function simply returns true, allowing parsing of
// the entry to continue.
virtual bool LanguageSpecificDataArea(uint64 address, bool indirect) {
return true;
}
// This entry describes a signal trampoline --- this frame is the
// caller of a signal handler. The default definition for this
// handler function simply returns true, allowing parsing of the
// entry to continue.
//
// The best description of the rationale for and meaning of signal
// trampoline CFI entries seems to be in the GCC bug database:
// http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26208
virtual bool SignalHandler() { return true; }
};
// The CallFrameInfo class makes calls on an instance of this class to
// report errors or warn about problems in the data it is parsing. The
// default definitions of these methods print a message to stderr, but
// you can make a derived class that overrides them.
class CallFrameInfo::Reporter {
public:
// Create an error reporter which attributes troubles to the section
// named SECTION in FILENAME.
//
// Normally SECTION would be .debug_frame, but the Mac puts CFI data
// in a Mach-O section named __debug_frame. If we support
// Linux-style exception handling data, we could be reading an
// .eh_frame section.
Reporter(const string &filename,
const string &section = ".debug_frame")
: filename_(filename), section_(section) { }
virtual ~Reporter() { }
// The CFI entry at OFFSET ends too early to be well-formed. KIND
// indicates what kind of entry it is; KIND can be kUnknown if we
// haven't parsed enough of the entry to tell yet.
virtual void Incomplete(uint64 offset, CallFrameInfo::EntryKind kind);
// The .eh_frame data has a four-byte zero at OFFSET where the next
// entry's length would be; this is a terminator. However, the buffer
// length as given to the CallFrameInfo constructor says there should be
// more data.
virtual void EarlyEHTerminator(uint64 offset);
// The FDE at OFFSET refers to the CIE at CIE_OFFSET, but the
// section is not that large.
virtual void CIEPointerOutOfRange(uint64 offset, uint64 cie_offset);
// The FDE at OFFSET refers to the CIE at CIE_OFFSET, but the entry
// there is not a CIE.
virtual void BadCIEId(uint64 offset, uint64 cie_offset);
// The FDE at OFFSET refers to a CIE with version number VERSION,
// which we don't recognize. We cannot parse DWARF CFI if it uses
// a version number we don't recognize.
virtual void UnrecognizedVersion(uint64 offset, int version);
// The FDE at OFFSET refers to a CIE with augmentation AUGMENTATION,
// which we don't recognize. We cannot parse DWARF CFI if it uses
// augmentations we don't recognize.
virtual void UnrecognizedAugmentation(uint64 offset,
const string &augmentation);
// The pointer encoding ENCODING, specified by the CIE at OFFSET, is not
// a valid encoding.
virtual void InvalidPointerEncoding(uint64 offset, uint8 encoding);
// The pointer encoding ENCODING, specified by the CIE at OFFSET, depends
// on a base address which has not been supplied.
virtual void UnusablePointerEncoding(uint64 offset, uint8 encoding);
// The CIE at OFFSET contains a DW_CFA_restore instruction at
// INSN_OFFSET, which may not appear in a CIE.
virtual void RestoreInCIE(uint64 offset, uint64 insn_offset);
// The entry at OFFSET, of kind KIND, has an unrecognized
// instruction at INSN_OFFSET.
virtual void BadInstruction(uint64 offset, CallFrameInfo::EntryKind kind,
uint64 insn_offset);
// The instruction at INSN_OFFSET in the entry at OFFSET, of kind
// KIND, establishes a rule that cites the CFA, but we have not
// established a CFA rule yet.
virtual void NoCFARule(uint64 offset, CallFrameInfo::EntryKind kind,
uint64 insn_offset);
// The instruction at INSN_OFFSET in the entry at OFFSET, of kind
// KIND, is a DW_CFA_restore_state instruction, but the stack of
// saved states is empty.
virtual void EmptyStateStack(uint64 offset, CallFrameInfo::EntryKind kind,
uint64 insn_offset);
// The DW_CFA_remember_state instruction at INSN_OFFSET in the entry
// at OFFSET, of kind KIND, would restore a state that has no CFA
// rule, whereas the current state does have a CFA rule. This is
// bogus input, which the CallFrameInfo::Handler interface doesn't
// (and shouldn't) have any way to report.
virtual void ClearingCFARule(uint64 offset, CallFrameInfo::EntryKind kind,
uint64 insn_offset);
protected:
// The name of the file whose CFI we're reading.
string filename_;
// The name of the CFI section in that file.
string section_;
};
} // namespace dwarf2reader
#endif // UTIL_DEBUGINFO_DWARF2READER_H__
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