The Tor Browser: tools/profiler/LulDwarf.cpp@97036ab72558 (annotated)

tools/profiler/LulDwarf.cpp@97036ab72558 (annotated)

tools/profiler/LulDwarf.cpp

Tue, 06 Jan 2015 21:39:09 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Tue, 06 Jan 2015 21:39:09 +0100
branch: TOR_BUG_9701
changeset 8: 97036ab72558
permissions: -rw-r--r--

Conditionally force memory storage according to privacy.thirdparty.isolate;
This solves Tor bug #9701, complying with disk avoidance documented in
https://www.torproject.org/projects/torbrowser/design/#disk-avoidance.

 /* -*- 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 (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>
 // Original author: Jim Blandy <jimb@mozilla.com> <jimb@red-bean.com>
 // Implementation of dwarf2reader::LineInfo, dwarf2reader::CompilationUnit,
 // and dwarf2reader::CallFrameInfo. See dwarf2reader.h for details.
 // This file is derived from the following files in
 // toolkit/crashreporter/google-breakpad:
 //   src/common/dwarf/bytereader.cc
 //   src/common/dwarf/dwarf2reader.cc
 //   src/common/dwarf_cfi_to_module.cc
 #include <stdint.h>
 #include <stdio.h>
 #include <string.h>
 #include <stdlib.h>
 #include <map>
 #include <stack>
 #include <string>
 #include "mozilla/Assertions.h"
 #include "LulCommonExt.h"
 #include "LulDwarfInt.h"
 // Set this to 1 for verbose logging
 #define DEBUG_DWARF 0
 namespace lul {
 using std::string;
 ByteReader::ByteReader(enum Endianness endian)
     :offset_reader_(NULL), address_reader_(NULL), endian_(endian),
      address_size_(0), offset_size_(0),
      have_section_base_(), have_text_base_(), have_data_base_(),
      have_function_base_() { }
 ByteReader::~ByteReader() { }
 void ByteReader::SetOffsetSize(uint8 size) {
   offset_size_ = size;
   MOZ_ASSERT(size == 4 || size == 8);
   if (size == 4) {
     this->offset_reader_ = &ByteReader::ReadFourBytes;
   } else {
     this->offset_reader_ = &ByteReader::ReadEightBytes;
   }
 }
 void ByteReader::SetAddressSize(uint8 size) {
   address_size_ = size;
   MOZ_ASSERT(size == 4 || size == 8);
   if (size == 4) {
     this->address_reader_ = &ByteReader::ReadFourBytes;
   } else {
     this->address_reader_ = &ByteReader::ReadEightBytes;
   }
 }
 uint64 ByteReader::ReadInitialLength(const char* start, size_t* len) {
   const uint64 initial_length = ReadFourBytes(start);
   start += 4;
   // In DWARF2/3, if the initial length is all 1 bits, then the offset
   // size is 8 and we need to read the next 8 bytes for the real length.
   if (initial_length == 0xffffffff) {
     SetOffsetSize(8);
     *len = 12;
     return ReadOffset(start);
   } else {
     SetOffsetSize(4);
     *len = 4;
   }
   return initial_length;
 }
 bool ByteReader::ValidEncoding(DwarfPointerEncoding encoding) const {
   if (encoding == DW_EH_PE_omit) return true;
   if (encoding == DW_EH_PE_aligned) return true;
   if ((encoding & 0x7) > DW_EH_PE_udata8)
     return false;
   if ((encoding & 0x70) > DW_EH_PE_funcrel)
     return false;
   return true;
 }
 bool ByteReader::UsableEncoding(DwarfPointerEncoding encoding) const {
   switch (encoding & 0x70) {
     case DW_EH_PE_absptr:  return true;
     case DW_EH_PE_pcrel:   return have_section_base_;
     case DW_EH_PE_textrel: return have_text_base_;
     case DW_EH_PE_datarel: return have_data_base_;
     case DW_EH_PE_funcrel: return have_function_base_;
     default:               return false;
   }
 }
 uint64 ByteReader::ReadEncodedPointer(const char *buffer,
                                       DwarfPointerEncoding encoding,
                                       size_t *len) const {
   // UsableEncoding doesn't approve of DW_EH_PE_omit, so we shouldn't
   // see it here.
   MOZ_ASSERT(encoding != DW_EH_PE_omit);
   // The Linux Standards Base 4.0 does not make this clear, but the
   // GNU tools (gcc/unwind-pe.h; readelf/dwarf.c; gdb/dwarf2-frame.c)
   // agree that aligned pointers are always absolute, machine-sized,
   // machine-signed pointers.
   if (encoding == DW_EH_PE_aligned) {
     MOZ_ASSERT(have_section_base_);
     // We don't need to align BUFFER in *our* address space. Rather, we
     // need to find the next position in our buffer that would be aligned
     // when the .eh_frame section the buffer contains is loaded into the
     // program's memory. So align assuming that buffer_base_ gets loaded at
     // address section_base_, where section_base_ itself may or may not be
     // aligned.
     // First, find the offset to START from the closest prior aligned
     // address.
     uint64 skew = section_base_ & (AddressSize() - 1);
     // Now find the offset from that aligned address to buffer.
     uint64 offset = skew + (buffer - buffer_base_);
     // Round up to the next boundary.
     uint64 aligned = (offset + AddressSize() - 1) & -AddressSize();
     // Convert back to a pointer.
     const char *aligned_buffer = buffer_base_ + (aligned - skew);
     // Finally, store the length and actually fetch the pointer.
     *len = aligned_buffer - buffer + AddressSize();
     return ReadAddress(aligned_buffer);
   }
   // Extract the value first, ignoring whether it's a pointer or an
   // offset relative to some base.
   uint64 offset;
   switch (encoding & 0x0f) {
     case DW_EH_PE_absptr:
       // DW_EH_PE_absptr is weird, as it is used as a meaningful value for
       // both the high and low nybble of encoding bytes. When it appears in
       // the high nybble, it means that the pointer is absolute, not an
       // offset from some base address. When it appears in the low nybble,
       // as here, it means that the pointer is stored as a normal
       // machine-sized and machine-signed address. A low nybble of
       // DW_EH_PE_absptr does not imply that the pointer is absolute; it is
       // correct for us to treat the value as an offset from a base address
       // if the upper nybble is not DW_EH_PE_absptr.
       offset = ReadAddress(buffer);
       *len = AddressSize();
       break;
     case DW_EH_PE_uleb128:
       offset = ReadUnsignedLEB128(buffer, len);
       break;
     case DW_EH_PE_udata2:
       offset = ReadTwoBytes(buffer);
       *len = 2;
       break;
     case DW_EH_PE_udata4:
       offset = ReadFourBytes(buffer);
       *len = 4;
       break;
     case DW_EH_PE_udata8:
       offset = ReadEightBytes(buffer);
       *len = 8;
       break;
     case DW_EH_PE_sleb128:
       offset = ReadSignedLEB128(buffer, len);
       break;
     case DW_EH_PE_sdata2:
       offset = ReadTwoBytes(buffer);
       // Sign-extend from 16 bits.
       offset = (offset ^ 0x8000) - 0x8000;
       *len = 2;
       break;
     case DW_EH_PE_sdata4:
       offset = ReadFourBytes(buffer);
       // Sign-extend from 32 bits.
       offset = (offset ^ 0x80000000ULL) - 0x80000000ULL;
       *len = 4;
       break;
     case DW_EH_PE_sdata8:
       // No need to sign-extend; this is the full width of our type.
       offset = ReadEightBytes(buffer);
       *len = 8;
       break;
     default:
       abort();
   }
   // Find the appropriate base address.
   uint64 base;
   switch (encoding & 0x70) {
     case DW_EH_PE_absptr:
       base = 0;
       break;
     case DW_EH_PE_pcrel:
       MOZ_ASSERT(have_section_base_);
       base = section_base_ + (buffer - buffer_base_);
       break;
     case DW_EH_PE_textrel:
       MOZ_ASSERT(have_text_base_);
       base = text_base_;
       break;
     case DW_EH_PE_datarel:
       MOZ_ASSERT(have_data_base_);
       base = data_base_;
       break;
     case DW_EH_PE_funcrel:
       MOZ_ASSERT(have_function_base_);
       base = function_base_;
       break;
     default:
       abort();
   }
   uint64 pointer = base + offset;
   // Remove inappropriate upper bits.
   if (AddressSize() == 4)
     pointer = pointer & 0xffffffff;
   else
     MOZ_ASSERT(AddressSize() == sizeof(uint64));
   return pointer;
 }
 // A DWARF rule for recovering the address or value of a register, or
 // computing the canonical frame address. There is one subclass of this for
 // each '*Rule' member function in CallFrameInfo::Handler.
 //
 // It's annoying that we have to handle Rules using pointers (because
 // the concrete instances can have an arbitrary size). They're small,
 // so it would be much nicer if we could just handle them by value
 // instead of fretting about ownership and destruction.
 //
 // It seems like all these could simply be instances of std::tr1::bind,
 // except that we need instances to be EqualityComparable, too.
 //
 // This could logically be nested within State, but then the qualified names
 // get horrendous.
 class CallFrameInfo::Rule {
  public:
   virtual ~Rule() { }
   // Tell HANDLER that, at ADDRESS in the program, REGISTER can be
   // recovered using this rule. If REGISTER is kCFARegister, then this rule
   // describes how to compute the canonical frame address. Return what the
   // HANDLER member function returned.
   virtual bool Handle(Handler *handler,
                       uint64 address, int register) const = 0;
   // Equality on rules. We use these to decide which rules we need
   // to report after a DW_CFA_restore_state instruction.
   virtual bool operator==(const Rule &rhs) const = 0;
   bool operator!=(const Rule &rhs) const { return ! (*this == rhs); }
   // Return a pointer to a copy of this rule.
   virtual Rule *Copy() const = 0;
   // If this is a base+offset rule, change its base register to REG.
   // Otherwise, do nothing. (Ugly, but required for DW_CFA_def_cfa_register.)
   virtual void SetBaseRegister(unsigned reg) { }
   // If this is a base+offset rule, change its offset to OFFSET. Otherwise,
   // do nothing. (Ugly, but required for DW_CFA_def_cfa_offset.)
   virtual void SetOffset(long long offset) { }
   // A RTTI workaround, to make it possible to implement equality
   // comparisons on classes derived from this one.
   enum CFIRTag {
     CFIR_UNDEFINED_RULE,
     CFIR_SAME_VALUE_RULE,
     CFIR_OFFSET_RULE,
     CFIR_VAL_OFFSET_RULE,
     CFIR_REGISTER_RULE,
     CFIR_EXPRESSION_RULE,
     CFIR_VAL_EXPRESSION_RULE
   };
   // Produce the tag that identifies the child class of this object.
   virtual CFIRTag getTag() const = 0;
 };
 // Rule: the value the register had in the caller cannot be recovered.
 class CallFrameInfo::UndefinedRule: public CallFrameInfo::Rule {
  public:
   UndefinedRule() { }
   ~UndefinedRule() { }
   CFIRTag getTag() const { return CFIR_UNDEFINED_RULE; }
   bool Handle(Handler *handler, uint64 address, int reg) const {
     return handler->UndefinedRule(address, reg);
   }
   bool operator==(const Rule &rhs) const {
     if (rhs.getTag() != CFIR_UNDEFINED_RULE) return false;
     return true;
   }
   Rule *Copy() const { return new UndefinedRule(*this); }
 };
 // Rule: the register's value is the same as that it had in the caller.
 class CallFrameInfo::SameValueRule: public CallFrameInfo::Rule {
  public:
   SameValueRule() { }
   ~SameValueRule() { }
   CFIRTag getTag() const { return CFIR_SAME_VALUE_RULE; }
   bool Handle(Handler *handler, uint64 address, int reg) const {
     return handler->SameValueRule(address, reg);
   }
   bool operator==(const Rule &rhs) const {
     if (rhs.getTag() != CFIR_SAME_VALUE_RULE) return false;
     return true;
   }
   Rule *Copy() const { return new SameValueRule(*this); }
 };
 // Rule: the register is saved at OFFSET from BASE_REGISTER.  BASE_REGISTER
 // may be CallFrameInfo::Handler::kCFARegister.
 class CallFrameInfo::OffsetRule: public CallFrameInfo::Rule {
  public:
   OffsetRule(int base_register, long offset)
       : base_register_(base_register), offset_(offset) { }
   ~OffsetRule() { }
   CFIRTag getTag() const { return CFIR_OFFSET_RULE; }
   bool Handle(Handler *handler, uint64 address, int reg) const {
     return handler->OffsetRule(address, reg, base_register_, offset_);
   }
   bool operator==(const Rule &rhs) const {
     if (rhs.getTag() != CFIR_OFFSET_RULE) return false;
     const OffsetRule *our_rhs = static_cast<const OffsetRule *>(&rhs);
     return (base_register_ == our_rhs->base_register_ &&
             offset_ == our_rhs->offset_);
   }
   Rule *Copy() const { return new OffsetRule(*this); }
   // We don't actually need SetBaseRegister or SetOffset here, since they
   // are only ever applied to CFA rules, for DW_CFA_def_cfa_offset, and it
   // doesn't make sense to use OffsetRule for computing the CFA: it
   // computes the address at which a register is saved, not a value.
  private:
   int base_register_;
   long offset_;
 };
 // Rule: the value the register had in the caller is the value of
 // BASE_REGISTER plus offset. BASE_REGISTER may be
 // CallFrameInfo::Handler::kCFARegister.
 class CallFrameInfo::ValOffsetRule: public CallFrameInfo::Rule {
  public:
   ValOffsetRule(int base_register, long offset)
       : base_register_(base_register), offset_(offset) { }
   ~ValOffsetRule() { }
   CFIRTag getTag() const { return CFIR_VAL_OFFSET_RULE; }
   bool Handle(Handler *handler, uint64 address, int reg) const {
     return handler->ValOffsetRule(address, reg, base_register_, offset_);
   }
   bool operator==(const Rule &rhs) const {
     if (rhs.getTag() != CFIR_VAL_OFFSET_RULE) return false;
     const ValOffsetRule *our_rhs = static_cast<const ValOffsetRule *>(&rhs);
     return (base_register_ == our_rhs->base_register_ &&
             offset_ == our_rhs->offset_);
   }
   Rule *Copy() const { return new ValOffsetRule(*this); }
   void SetBaseRegister(unsigned reg) { base_register_ = reg; }
   void SetOffset(long long offset) { offset_ = offset; }
  private:
   int base_register_;
   long offset_;
 };
 // Rule: the register has been saved in another register REGISTER_NUMBER_.
 class CallFrameInfo::RegisterRule: public CallFrameInfo::Rule {
  public:
   explicit RegisterRule(int register_number)
       : register_number_(register_number) { }
   ~RegisterRule() { }
   CFIRTag getTag() const { return CFIR_REGISTER_RULE; }
   bool Handle(Handler *handler, uint64 address, int reg) const {
     return handler->RegisterRule(address, reg, register_number_);
   }
   bool operator==(const Rule &rhs) const {
     if (rhs.getTag() != CFIR_REGISTER_RULE) return false;
     const RegisterRule *our_rhs = static_cast<const RegisterRule *>(&rhs);
     return (register_number_ == our_rhs->register_number_);
   }
   Rule *Copy() const { return new RegisterRule(*this); }
  private:
   int register_number_;
 };
 // Rule: EXPRESSION evaluates to the address at which the register is saved.
 class CallFrameInfo::ExpressionRule: public CallFrameInfo::Rule {
  public:
   explicit ExpressionRule(const string &expression)
       : expression_(expression) { }
   ~ExpressionRule() { }
   CFIRTag getTag() const { return CFIR_EXPRESSION_RULE; }
   bool Handle(Handler *handler, uint64 address, int reg) const {
     return handler->ExpressionRule(address, reg, expression_);
   }
   bool operator==(const Rule &rhs) const {
     if (rhs.getTag() != CFIR_EXPRESSION_RULE) return false;
     const ExpressionRule *our_rhs = static_cast<const ExpressionRule *>(&rhs);
     return (expression_ == our_rhs->expression_);
   }
   Rule *Copy() const { return new ExpressionRule(*this); }
  private:
   string expression_;
 };
 // Rule: EXPRESSION evaluates to the previous value of the register.
 class CallFrameInfo::ValExpressionRule: public CallFrameInfo::Rule {
  public:
   explicit ValExpressionRule(const string &expression)
       : expression_(expression) { }
   ~ValExpressionRule() { }
   CFIRTag getTag() const { return CFIR_VAL_EXPRESSION_RULE; }
   bool Handle(Handler *handler, uint64 address, int reg) const {
     return handler->ValExpressionRule(address, reg, expression_);
   }
   bool operator==(const Rule &rhs) const {
     if (rhs.getTag() != CFIR_VAL_EXPRESSION_RULE) return false;
     const ValExpressionRule *our_rhs =
         static_cast<const ValExpressionRule *>(&rhs);
     return (expression_ == our_rhs->expression_);
   }
   Rule *Copy() const { return new ValExpressionRule(*this); }
  private:
   string expression_;
 };
 // A map from register numbers to rules.
 class CallFrameInfo::RuleMap {
  public:
   RuleMap() : cfa_rule_(NULL) { }
   RuleMap(const RuleMap &rhs) : cfa_rule_(NULL) { *this = rhs; }
   ~RuleMap() { Clear(); }
   RuleMap &operator=(const RuleMap &rhs);
   // Set the rule for computing the CFA to RULE. Take ownership of RULE.
   void SetCFARule(Rule *rule) { delete cfa_rule_; cfa_rule_ = rule; }
   // Return the current CFA rule. Unlike RegisterRule, this RuleMap retains
   // ownership of the rule. We use this for DW_CFA_def_cfa_offset and
   // DW_CFA_def_cfa_register, and for detecting references to the CFA before
   // a rule for it has been established.
   Rule *CFARule() const { return cfa_rule_; }
   // Return the rule for REG, or NULL if there is none. The caller takes
   // ownership of the result.
   Rule *RegisterRule(int reg) const;
   // Set the rule for computing REG to RULE. Take ownership of RULE.
   void SetRegisterRule(int reg, Rule *rule);
   // Make all the appropriate calls to HANDLER as if we were changing from
   // this RuleMap to NEW_RULES at ADDRESS. We use this to implement
   // DW_CFA_restore_state, where lots of rules can change simultaneously.
   // Return true if all handlers returned true; otherwise, return false.
   bool HandleTransitionTo(Handler *handler, uint64 address,
                           const RuleMap &new_rules) const;
  private:
   // A map from register numbers to Rules.
   typedef std::map<int, Rule *> RuleByNumber;
   // Remove all register rules and clear cfa_rule_.
   void Clear();
   // The rule for computing the canonical frame address. This RuleMap owns
   // this rule.
   Rule *cfa_rule_;
   // A map from register numbers to postfix expressions to recover
   // their values. This RuleMap owns the Rules the map refers to.
   RuleByNumber registers_;
 };
 CallFrameInfo::RuleMap &CallFrameInfo::RuleMap::operator=(const RuleMap &rhs) {
   Clear();
   // Since each map owns the rules it refers to, assignment must copy them.
   if (rhs.cfa_rule_) cfa_rule_ = rhs.cfa_rule_->Copy();
   for (RuleByNumber::const_iterator it = rhs.registers_.begin();
        it != rhs.registers_.end(); it++)
     registers_[it->first] = it->second->Copy();
   return *this;
 }
 CallFrameInfo::Rule *CallFrameInfo::RuleMap::RegisterRule(int reg) const {
   MOZ_ASSERT(reg != Handler::kCFARegister);
   RuleByNumber::const_iterator it = registers_.find(reg);
   if (it != registers_.end())
     return it->second->Copy();
   else
     return NULL;
 }
 void CallFrameInfo::RuleMap::SetRegisterRule(int reg, Rule *rule) {
   MOZ_ASSERT(reg != Handler::kCFARegister);
   MOZ_ASSERT(rule);
   Rule **slot = &registers_[reg];
   delete *slot;
   *slot = rule;
 }
 bool CallFrameInfo::RuleMap::HandleTransitionTo(
     Handler *handler,
     uint64 address,
     const RuleMap &new_rules) const {
   // Transition from cfa_rule_ to new_rules.cfa_rule_.
   if (cfa_rule_ && new_rules.cfa_rule_) {
     if (*cfa_rule_ != *new_rules.cfa_rule_ &&
         !new_rules.cfa_rule_->Handle(handler, address, Handler::kCFARegister))
       return false;
   } else if (cfa_rule_) {
     // this RuleMap has a CFA rule but new_rules doesn't.
     // CallFrameInfo::Handler has no way to handle this --- and shouldn't;
     // it's garbage input. The instruction interpreter should have
     // detected this and warned, so take no action here.
   } else if (new_rules.cfa_rule_) {
     // This shouldn't be possible: NEW_RULES is some prior state, and
     // there's no way to remove entries.
     MOZ_ASSERT(0);
   } else {
     // Both CFA rules are empty.  No action needed.
   }
   // Traverse the two maps in order by register number, and report
   // whatever differences we find.
   RuleByNumber::const_iterator old_it = registers_.begin();
   RuleByNumber::const_iterator new_it = new_rules.registers_.begin();
   while (old_it != registers_.end() && new_it != new_rules.registers_.end()) {
     if (old_it->first < new_it->first) {
       // This RuleMap has an entry for old_it->first, but NEW_RULES
       // doesn't.
       //
       // This isn't really the right thing to do, but since CFI generally
       // only mentions callee-saves registers, and GCC's convention for
       // callee-saves registers is that they are unchanged, it's a good
       // approximation.
       if (!handler->SameValueRule(address, old_it->first))
         return false;
       old_it++;
     } else if (old_it->first > new_it->first) {
       // NEW_RULES has entry for new_it->first, but this RuleMap
       // doesn't. This shouldn't be possible: NEW_RULES is some prior
       // state, and there's no way to remove entries.
       MOZ_ASSERT(0);
     } else {
       // Both maps have an entry for this register. Report the new
       // rule if it is different.
       if (*old_it->second != *new_it->second &&
           !new_it->second->Handle(handler, address, new_it->first))
         return false;
       new_it++, old_it++;
     }
   }
   // Finish off entries from this RuleMap with no counterparts in new_rules.
   while (old_it != registers_.end()) {
     if (!handler->SameValueRule(address, old_it->first))
       return false;
     old_it++;
   }
   // Since we only make transitions from a rule set to some previously
   // saved rule set, and we can only add rules to the map, NEW_RULES
   // must have fewer rules than *this.
   MOZ_ASSERT(new_it == new_rules.registers_.end());
   return true;
 }
 // Remove all register rules and clear cfa_rule_.
 void CallFrameInfo::RuleMap::Clear() {
   delete cfa_rule_;
   cfa_rule_ = NULL;
   for (RuleByNumber::iterator it = registers_.begin();
        it != registers_.end(); it++)
     delete it->second;
   registers_.clear();
 }
 // The state of the call frame information interpreter as it processes
 // instructions from a CIE and FDE.
 class CallFrameInfo::State {
  public:
   // Create a call frame information interpreter state with the given
   // reporter, reader, handler, and initial call frame info address.
   State(ByteReader *reader, Handler *handler, Reporter *reporter,
         uint64 address)
       : reader_(reader), handler_(handler), reporter_(reporter),
         address_(address), entry_(NULL), cursor_(NULL),
         saved_rules_(NULL) { }
   ~State() {
     if (saved_rules_)
       delete saved_rules_;
   }
   // Interpret instructions from CIE, save the resulting rule set for
   // DW_CFA_restore instructions, and return true. On error, report
   // the problem to reporter_ and return false.
   bool InterpretCIE(const CIE &cie);
   // Interpret instructions from FDE, and return true. On error,
   // report the problem to reporter_ and return false.
   bool InterpretFDE(const FDE &fde);
  private:
   // The operands of a CFI instruction, for ParseOperands.
   struct Operands {
     unsigned register_number;  // A register number.
     uint64 offset;             // An offset or address.
     long signed_offset;        // A signed offset.
     string expression;         // A DWARF expression.
   };
   // Parse CFI instruction operands from STATE's instruction stream as
   // described by FORMAT. On success, populate OPERANDS with the
   // results, and return true. On failure, report the problem and
   // return false.
   //
   // Each character of FORMAT should be one of the following:
   //
   //   'r'  unsigned LEB128 register number (OPERANDS->register_number)
   //   'o'  unsigned LEB128 offset          (OPERANDS->offset)
   //   's'  signed LEB128 offset            (OPERANDS->signed_offset)
   //   'a'  machine-size address            (OPERANDS->offset)
   //        (If the CIE has a 'z' augmentation string, 'a' uses the
   //        encoding specified by the 'R' argument.)
   //   '1'  a one-byte offset               (OPERANDS->offset)
   //   '2'  a two-byte offset               (OPERANDS->offset)
   //   '4'  a four-byte offset              (OPERANDS->offset)
   //   '8'  an eight-byte offset            (OPERANDS->offset)
   //   'e'  a DW_FORM_block holding a       (OPERANDS->expression)
   //        DWARF expression
   bool ParseOperands(const char *format, Operands *operands);
   // Interpret one CFI instruction from STATE's instruction stream, update
   // STATE, report any rule changes to handler_, and return true. On
   // failure, report the problem and return false.
   bool DoInstruction();
   // The following Do* member functions are subroutines of DoInstruction,
   // factoring out the actual work of operations that have several
   // different encodings.
   // Set the CFA rule to be the value of BASE_REGISTER plus OFFSET, and
   // return true. On failure, report and return false. (Used for
   // DW_CFA_def_cfa and DW_CFA_def_cfa_sf.)
   bool DoDefCFA(unsigned base_register, long offset);
   // Change the offset of the CFA rule to OFFSET, and return true. On
   // failure, report and return false. (Subroutine for
   // DW_CFA_def_cfa_offset and DW_CFA_def_cfa_offset_sf.)
   bool DoDefCFAOffset(long offset);
   // Specify that REG can be recovered using RULE, and return true. On
   // failure, report and return false.
   bool DoRule(unsigned reg, Rule *rule);
   // Specify that REG can be found at OFFSET from the CFA, and return true.
   // On failure, report and return false. (Subroutine for DW_CFA_offset,
   // DW_CFA_offset_extended, and DW_CFA_offset_extended_sf.)
   bool DoOffset(unsigned reg, long offset);
   // Specify that the caller's value for REG is the CFA plus OFFSET,
   // and return true. On failure, report and return false. (Subroutine
   // for DW_CFA_val_offset and DW_CFA_val_offset_sf.)
   bool DoValOffset(unsigned reg, long offset);
   // Restore REG to the rule established in the CIE, and return true. On
   // failure, report and return false. (Subroutine for DW_CFA_restore and
   // DW_CFA_restore_extended.)
   bool DoRestore(unsigned reg);
   // Return the section offset of the instruction at cursor. For use
   // in error messages.
   uint64 CursorOffset() { return entry_->offset + (cursor_ - entry_->start); }
   // Report that entry_ is incomplete, and return false. For brevity.
   bool ReportIncomplete() {
     reporter_->Incomplete(entry_->offset, entry_->kind);
     return false;
   }
   // 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_;
   // The code address to which the next instruction in the stream applies.
   uint64 address_;
   // The entry whose instructions we are currently processing. This is
   // first a CIE, and then an FDE.
   const Entry *entry_;
   // The next instruction to process.
   const char *cursor_;
   // The current set of rules.
   RuleMap rules_;
   // The set of rules established by the CIE, used by DW_CFA_restore
   // and DW_CFA_restore_extended. We set this after interpreting the
   // CIE's instructions.
   RuleMap cie_rules_;
   // A stack of saved states, for DW_CFA_remember_state and
   // DW_CFA_restore_state.
   std::stack<RuleMap>* saved_rules_;
 };
 bool CallFrameInfo::State::InterpretCIE(const CIE &cie) {
   entry_ = &cie;
   cursor_ = entry_->instructions;
   while (cursor_ < entry_->end)
     if (!DoInstruction())
       return false;
   // Note the rules established by the CIE, for use by DW_CFA_restore
   // and DW_CFA_restore_extended.
   cie_rules_ = rules_;
   return true;
 }
 bool CallFrameInfo::State::InterpretFDE(const FDE &fde) {
   entry_ = &fde;
   cursor_ = entry_->instructions;
   while (cursor_ < entry_->end)
     if (!DoInstruction())
       return false;
   return true;
 }
 bool CallFrameInfo::State::ParseOperands(const char *format,
                                          Operands *operands) {
   size_t len;
   const char *operand;
   for (operand = format; *operand; operand++) {
     size_t bytes_left = entry_->end - cursor_;
     switch (*operand) {
       case 'r':
         operands->register_number = reader_->ReadUnsignedLEB128(cursor_, &len);
         if (len > bytes_left) return ReportIncomplete();
         cursor_ += len;
         break;
       case 'o':
         operands->offset = reader_->ReadUnsignedLEB128(cursor_, &len);
         if (len > bytes_left) return ReportIncomplete();
         cursor_ += len;
         break;
       case 's':
         operands->signed_offset = reader_->ReadSignedLEB128(cursor_, &len);
         if (len > bytes_left) return ReportIncomplete();
         cursor_ += len;
         break;
       case 'a':
         operands->offset =
           reader_->ReadEncodedPointer(cursor_, entry_->cie->pointer_encoding,
                                       &len);
         if (len > bytes_left) return ReportIncomplete();
         cursor_ += len;
         break;
       case '1':
         if (1 > bytes_left) return ReportIncomplete();
         operands->offset = static_cast<unsigned char>(*cursor_++);
         break;
       case '2':
         if (2 > bytes_left) return ReportIncomplete();
         operands->offset = reader_->ReadTwoBytes(cursor_);
         cursor_ += 2;
         break;
       case '4':
         if (4 > bytes_left) return ReportIncomplete();
         operands->offset = reader_->ReadFourBytes(cursor_);
         cursor_ += 4;
         break;
       case '8':
         if (8 > bytes_left) return ReportIncomplete();
         operands->offset = reader_->ReadEightBytes(cursor_);
         cursor_ += 8;
         break;
       case 'e': {
         size_t expression_length = reader_->ReadUnsignedLEB128(cursor_, &len);
         if (len > bytes_left || expression_length > bytes_left - len)
           return ReportIncomplete();
         cursor_ += len;
         operands->expression = string(cursor_, expression_length);
         cursor_ += expression_length;
         break;
       }
       default:
         MOZ_ASSERT(0);
     }
   }
   return true;
 }
 bool CallFrameInfo::State::DoInstruction() {
   CIE *cie = entry_->cie;
   Operands ops;
   // Our entry's kind should have been set by now.
   MOZ_ASSERT(entry_->kind != kUnknown);
   // We shouldn't have been invoked unless there were more
   // instructions to parse.
   MOZ_ASSERT(cursor_ < entry_->end);
   unsigned opcode = *cursor_++;
   if ((opcode & 0xc0) != 0) {
     switch (opcode & 0xc0) {
       // Advance the address.
       case DW_CFA_advance_loc: {
         size_t code_offset = opcode & 0x3f;
         address_ += code_offset * cie->code_alignment_factor;
         break;
       }
       // Find a register at an offset from the CFA.
       case DW_CFA_offset:
         if (!ParseOperands("o", &ops) ||
             !DoOffset(opcode & 0x3f, ops.offset * cie->data_alignment_factor))
           return false;
         break;
       // Restore the rule established for a register by the CIE.
       case DW_CFA_restore:
         if (!DoRestore(opcode & 0x3f)) return false;
         break;
       // The 'if' above should have excluded this possibility.
       default:
         MOZ_ASSERT(0);
     }
     // Return here, so the big switch below won't be indented.
     return true;
   }
   switch (opcode) {
     // Set the address.
     case DW_CFA_set_loc:
       if (!ParseOperands("a", &ops)) return false;
       address_ = ops.offset;
       break;
     // Advance the address.
     case DW_CFA_advance_loc1:
       if (!ParseOperands("1", &ops)) return false;
       address_ += ops.offset * cie->code_alignment_factor;
       break;
     // Advance the address.
     case DW_CFA_advance_loc2:
       if (!ParseOperands("2", &ops)) return false;
       address_ += ops.offset * cie->code_alignment_factor;
       break;
     // Advance the address.
     case DW_CFA_advance_loc4:
       if (!ParseOperands("4", &ops)) return false;
       address_ += ops.offset * cie->code_alignment_factor;
       break;
     // Advance the address.
     case DW_CFA_MIPS_advance_loc8:
       if (!ParseOperands("8", &ops)) return false;
       address_ += ops.offset * cie->code_alignment_factor;
       break;
     // Compute the CFA by adding an offset to a register.
     case DW_CFA_def_cfa:
       if (!ParseOperands("ro", &ops) ||
           !DoDefCFA(ops.register_number, ops.offset))
         return false;
       break;
     // Compute the CFA by adding an offset to a register.
     case DW_CFA_def_cfa_sf:
       if (!ParseOperands("rs", &ops) ||
           !DoDefCFA(ops.register_number,
                     ops.signed_offset * cie->data_alignment_factor))
         return false;
       break;
     // Change the base register used to compute the CFA.
     case DW_CFA_def_cfa_register: {
       Rule *cfa_rule = rules_.CFARule();
       if (!cfa_rule) {
         reporter_->NoCFARule(entry_->offset, entry_->kind, CursorOffset());
         return false;
       }
       if (!ParseOperands("r", &ops)) return false;
       cfa_rule->SetBaseRegister(ops.register_number);
       if (!cfa_rule->Handle(handler_, address_, Handler::kCFARegister))
         return false;
       break;
     }
     // Change the offset used to compute the CFA.
     case DW_CFA_def_cfa_offset:
       if (!ParseOperands("o", &ops) ||
           !DoDefCFAOffset(ops.offset))
         return false;
       break;
     // Change the offset used to compute the CFA.
     case DW_CFA_def_cfa_offset_sf:
       if (!ParseOperands("s", &ops) ||
           !DoDefCFAOffset(ops.signed_offset * cie->data_alignment_factor))
         return false;
       break;
     // Specify an expression whose value is the CFA.
     case DW_CFA_def_cfa_expression: {
       if (!ParseOperands("e", &ops))
         return false;
       Rule *rule = new ValExpressionRule(ops.expression);
       rules_.SetCFARule(rule);
       if (!rule->Handle(handler_, address_, Handler::kCFARegister))
         return false;
       break;
     }
     // The register's value cannot be recovered.
     case DW_CFA_undefined: {
       if (!ParseOperands("r", &ops) ||
           !DoRule(ops.register_number, new UndefinedRule()))
         return false;
       break;
     }
     // The register's value is unchanged from its value in the caller.
     case DW_CFA_same_value: {
       if (!ParseOperands("r", &ops) ||
           !DoRule(ops.register_number, new SameValueRule()))
         return false;
       break;
     }
     // Find a register at an offset from the CFA.
     case DW_CFA_offset_extended:
       if (!ParseOperands("ro", &ops) ||
           !DoOffset(ops.register_number,
                     ops.offset * cie->data_alignment_factor))
         return false;
       break;
     // The register is saved at an offset from the CFA.
     case DW_CFA_offset_extended_sf:
       if (!ParseOperands("rs", &ops) ||
           !DoOffset(ops.register_number,
                     ops.signed_offset * cie->data_alignment_factor))
         return false;
       break;
     // The register is saved at an offset from the CFA.
     case DW_CFA_GNU_negative_offset_extended:
       if (!ParseOperands("ro", &ops) ||
           !DoOffset(ops.register_number,
                     -ops.offset * cie->data_alignment_factor))
         return false;
       break;
     // The register's value is the sum of the CFA plus an offset.
     case DW_CFA_val_offset:
       if (!ParseOperands("ro", &ops) ||
           !DoValOffset(ops.register_number,
                        ops.offset * cie->data_alignment_factor))
         return false;
       break;
     // The register's value is the sum of the CFA plus an offset.
     case DW_CFA_val_offset_sf:
       if (!ParseOperands("rs", &ops) ||
           !DoValOffset(ops.register_number,
                        ops.signed_offset * cie->data_alignment_factor))
         return false;
       break;
     // The register has been saved in another register.
     case DW_CFA_register: {
       if (!ParseOperands("ro", &ops) ||
           !DoRule(ops.register_number, new RegisterRule(ops.offset)))
         return false;
       break;
     }
     // An expression yields the address at which the register is saved.
     case DW_CFA_expression: {
       if (!ParseOperands("re", &ops) ||
           !DoRule(ops.register_number, new ExpressionRule(ops.expression)))
         return false;
       break;
     }
     // An expression yields the caller's value for the register.
     case DW_CFA_val_expression: {
       if (!ParseOperands("re", &ops) ||
           !DoRule(ops.register_number, new ValExpressionRule(ops.expression)))
         return false;
       break;
     }
     // Restore the rule established for a register by the CIE.
     case DW_CFA_restore_extended:
       if (!ParseOperands("r", &ops) ||
           !DoRestore( ops.register_number))
         return false;
       break;
     // Save the current set of rules on a stack.
     case DW_CFA_remember_state:
       if (!saved_rules_) {
         saved_rules_ = new std::stack<RuleMap>();
       }
       saved_rules_->push(rules_);
       break;
     // Pop the current set of rules off the stack.
     case DW_CFA_restore_state: {
       if (!saved_rules_ || saved_rules_->empty()) {
         reporter_->EmptyStateStack(entry_->offset, entry_->kind,
                                    CursorOffset());
         return false;
       }
       const RuleMap &new_rules = saved_rules_->top();
       if (rules_.CFARule() && !new_rules.CFARule()) {
         reporter_->ClearingCFARule(entry_->offset, entry_->kind,
                                    CursorOffset());
         return false;
       }
       rules_.HandleTransitionTo(handler_, address_, new_rules);
       rules_ = new_rules;
       saved_rules_->pop();
       break;
     }
     // No operation.  (Padding instruction.)
     case DW_CFA_nop:
       break;
     // A SPARC register window save: Registers 8 through 15 (%o0-%o7)
     // are saved in registers 24 through 31 (%i0-%i7), and registers
     // 16 through 31 (%l0-%l7 and %i0-%i7) are saved at CFA offsets
     // (0-15 * the register size). The register numbers must be
     // hard-coded. A GNU extension, and not a pretty one.
     case DW_CFA_GNU_window_save: {
       // Save %o0-%o7 in %i0-%i7.
       for (int i = 8; i < 16; i++)
         if (!DoRule(i, new RegisterRule(i + 16)))
           return false;
       // Save %l0-%l7 and %i0-%i7 at the CFA.
       for (int i = 16; i < 32; i++)
         // Assume that the byte reader's address size is the same as
         // the architecture's register size. !@#%*^ hilarious.
         if (!DoRule(i, new OffsetRule(Handler::kCFARegister,
                                       (i - 16) * reader_->AddressSize())))
           return false;
       break;
     }
     // I'm not sure what this is. GDB doesn't use it for unwinding.
     case DW_CFA_GNU_args_size:
       if (!ParseOperands("o", &ops)) return false;
       break;
     // An opcode we don't recognize.
     default: {
       reporter_->BadInstruction(entry_->offset, entry_->kind, CursorOffset());
       return false;
     }
   }
   return true;
 }
 bool CallFrameInfo::State::DoDefCFA(unsigned base_register, long offset) {
   Rule *rule = new ValOffsetRule(base_register, offset);
   rules_.SetCFARule(rule);
   return rule->Handle(handler_, address_, Handler::kCFARegister);
 }
 bool CallFrameInfo::State::DoDefCFAOffset(long offset) {
   Rule *cfa_rule = rules_.CFARule();
   if (!cfa_rule) {
     reporter_->NoCFARule(entry_->offset, entry_->kind, CursorOffset());
     return false;
   }
   cfa_rule->SetOffset(offset);
   return cfa_rule->Handle(handler_, address_, Handler::kCFARegister);
 }
 bool CallFrameInfo::State::DoRule(unsigned reg, Rule *rule) {
   rules_.SetRegisterRule(reg, rule);
   return rule->Handle(handler_, address_, reg);
 }
 bool CallFrameInfo::State::DoOffset(unsigned reg, long offset) {
   if (!rules_.CFARule()) {
     reporter_->NoCFARule(entry_->offset, entry_->kind, CursorOffset());
     return false;
   }
   return DoRule(reg,
                 new OffsetRule(Handler::kCFARegister, offset));
 }
 bool CallFrameInfo::State::DoValOffset(unsigned reg, long offset) {
   if (!rules_.CFARule()) {
     reporter_->NoCFARule(entry_->offset, entry_->kind, CursorOffset());
     return false;
   }
   return DoRule(reg,
                 new ValOffsetRule(Handler::kCFARegister, offset));
 }
 bool CallFrameInfo::State::DoRestore(unsigned reg) {
   // DW_CFA_restore and DW_CFA_restore_extended don't make sense in a CIE.
   if (entry_->kind == kCIE) {
     reporter_->RestoreInCIE(entry_->offset, CursorOffset());
     return false;
   }
   Rule *rule = cie_rules_.RegisterRule(reg);
   if (!rule) {
     // This isn't really the right thing to do, but since CFI generally
     // only mentions callee-saves registers, and GCC's convention for
     // callee-saves registers is that they are unchanged, it's a good
     // approximation.
     rule = new SameValueRule();
   }
   return DoRule(reg, rule);
 }
 bool CallFrameInfo::ReadEntryPrologue(const char *cursor, Entry *entry) {
   const char *buffer_end = buffer_ + buffer_length_;
   // Initialize enough of ENTRY for use in error reporting.
   entry->offset = cursor - buffer_;
   entry->start = cursor;
   entry->kind = kUnknown;
   entry->end = NULL;
   // Read the initial length. This sets reader_'s offset size.
   size_t length_size;
   uint64 length = reader_->ReadInitialLength(cursor, &length_size);
   if (length_size > size_t(buffer_end - cursor))
     return ReportIncomplete(entry);
   cursor += length_size;
   // In a .eh_frame section, a length of zero marks the end of the series
   // of entries.
   if (length == 0 && eh_frame_) {
     entry->kind = kTerminator;
     entry->end = cursor;
     return true;
   }
   // Validate the length.
   if (length > size_t(buffer_end - cursor))
     return ReportIncomplete(entry);
   // The length is the number of bytes after the initial length field;
   // we have that position handy at this point, so compute the end
   // now. (If we're parsing 64-bit-offset DWARF on a 32-bit machine,
   // and the length didn't fit in a size_t, we would have rejected it
   // above.)
   entry->end = cursor + length;
   // Parse the next field: either the offset of a CIE or a CIE id.
   size_t offset_size = reader_->OffsetSize();
   if (offset_size > size_t(entry->end - cursor)) return ReportIncomplete(entry);
   entry->id = reader_->ReadOffset(cursor);
   // Don't advance cursor past id field yet; in .eh_frame data we need
   // the id's position to compute the section offset of an FDE's CIE.
   // Now we can decide what kind of entry this is.
   if (eh_frame_) {
     // In .eh_frame data, an ID of zero marks the entry as a CIE, and
     // anything else is an offset from the id field of the FDE to the start
     // of the CIE.
     if (entry->id == 0) {
       entry->kind = kCIE;
     } else {
       entry->kind = kFDE;
       // Turn the offset from the id into an offset from the buffer's start.
       entry->id = (cursor - buffer_) - entry->id;
     }
   } else {
     // In DWARF CFI data, an ID of ~0 (of the appropriate width, given the
     // offset size for the entry) marks the entry as a CIE, and anything
     // else is the offset of the CIE from the beginning of the section.
     if (offset_size == 4)
       entry->kind = (entry->id == 0xffffffff) ? kCIE : kFDE;
     else {
       MOZ_ASSERT(offset_size == 8);
       entry->kind = (entry->id == 0xffffffffffffffffULL) ? kCIE : kFDE;
     }
   }
   // Now advance cursor past the id.
    cursor += offset_size;
   // The fields specific to this kind of entry start here.
   entry->fields = cursor;
   entry->cie = NULL;
   return true;
 }
 bool CallFrameInfo::ReadCIEFields(CIE *cie) {
   const char *cursor = cie->fields;
   size_t len;
   MOZ_ASSERT(cie->kind == kCIE);
   // Prepare for early exit.
   cie->version = 0;
   cie->augmentation.clear();
   cie->code_alignment_factor = 0;
   cie->data_alignment_factor = 0;
   cie->return_address_register = 0;
   cie->has_z_augmentation = false;
   cie->pointer_encoding = DW_EH_PE_absptr;
   cie->instructions = 0;
   // Parse the version number.
   if (cie->end - cursor < 1)
     return ReportIncomplete(cie);
   cie->version = reader_->ReadOneByte(cursor);
   cursor++;
   // If we don't recognize the version, we can't parse any more fields of the
   // CIE. For DWARF CFI, we handle versions 1 through 3 (there was never a
   // version 2 of CFI data). For .eh_frame, we handle versions 1 and 3 as well;
   // the difference between those versions seems to be the same as for
   // .debug_frame.
   if (cie->version < 1 || cie->version > 3) {
     reporter_->UnrecognizedVersion(cie->offset, cie->version);
     return false;
   }
   const char *augmentation_start = cursor;
   const void *augmentation_end =
       memchr(augmentation_start, '\0', cie->end - augmentation_start);
   if (! augmentation_end) return ReportIncomplete(cie);
   cursor = static_cast<const char *>(augmentation_end);
   cie->augmentation = string(augmentation_start,
                                   cursor - augmentation_start);
   // Skip the terminating '\0'.
   cursor++;
   // Is this CFI augmented?
   if (!cie->augmentation.empty()) {
     // Is it an augmentation we recognize?
     if (cie->augmentation[0] == DW_Z_augmentation_start) {
       // Linux C++ ABI 'z' augmentation, used for exception handling data.
       cie->has_z_augmentation = true;
     } else {
       // Not an augmentation we recognize. Augmentations can have arbitrary
       // effects on the form of rest of the content, so we have to give up.
       reporter_->UnrecognizedAugmentation(cie->offset, cie->augmentation);
       return false;
     }
   }
   // Parse the code alignment factor.
   cie->code_alignment_factor = reader_->ReadUnsignedLEB128(cursor, &len);
   if (size_t(cie->end - cursor) < len) return ReportIncomplete(cie);
   cursor += len;
   // Parse the data alignment factor.
   cie->data_alignment_factor = reader_->ReadSignedLEB128(cursor, &len);
   if (size_t(cie->end - cursor) < len) return ReportIncomplete(cie);
   cursor += len;
   // Parse the return address register. This is a ubyte in version 1, and
   // a ULEB128 in version 3.
   if (cie->version == 1) {
     if (cursor >= cie->end) return ReportIncomplete(cie);
     cie->return_address_register = uint8(*cursor++);
   } else {
     cie->return_address_register = reader_->ReadUnsignedLEB128(cursor, &len);
     if (size_t(cie->end - cursor) < len) return ReportIncomplete(cie);
     cursor += len;
   }
   // If we have a 'z' augmentation string, find the augmentation data and
   // use the augmentation string to parse it.
   if (cie->has_z_augmentation) {
     uint64_t data_size = reader_->ReadUnsignedLEB128(cursor, &len);
     if (size_t(cie->end - cursor) < len + data_size)
       return ReportIncomplete(cie);
     cursor += len;
     const char *data = cursor;
     cursor += data_size;
     const char *data_end = cursor;
     cie->has_z_lsda = false;
     cie->has_z_personality = false;
     cie->has_z_signal_frame = false;
     // Walk the augmentation string, and extract values from the
     // augmentation data as the string directs.
     for (size_t i = 1; i < cie->augmentation.size(); i++) {
       switch (cie->augmentation[i]) {
         case DW_Z_has_LSDA:
           // The CIE's augmentation data holds the language-specific data
           // area pointer's encoding, and the FDE's augmentation data holds
           // the pointer itself.
           cie->has_z_lsda = true;
           // Fetch the LSDA encoding from the augmentation data.
           if (data >= data_end) return ReportIncomplete(cie);
           cie->lsda_encoding = DwarfPointerEncoding(*data++);
           if (!reader_->ValidEncoding(cie->lsda_encoding)) {
             reporter_->InvalidPointerEncoding(cie->offset, cie->lsda_encoding);
             return false;
           }
           // Don't check if the encoding is usable here --- we haven't
           // read the FDE's fields yet, so we're not prepared for
           // DW_EH_PE_funcrel, although that's a fine encoding for the
           // LSDA to use, since it appears in the FDE.
           break;
         case DW_Z_has_personality_routine:
           // The CIE's augmentation data holds the personality routine
           // pointer's encoding, followed by the pointer itself.
           cie->has_z_personality = true;
           // Fetch the personality routine pointer's encoding from the
           // augmentation data.
           if (data >= data_end) return ReportIncomplete(cie);
           cie->personality_encoding = DwarfPointerEncoding(*data++);
           if (!reader_->ValidEncoding(cie->personality_encoding)) {
             reporter_->InvalidPointerEncoding(cie->offset,
                                               cie->personality_encoding);
             return false;
           }
           if (!reader_->UsableEncoding(cie->personality_encoding)) {
             reporter_->UnusablePointerEncoding(cie->offset,
                                                cie->personality_encoding);
             return false;
           }
           // Fetch the personality routine's pointer itself from the data.
           cie->personality_address =
             reader_->ReadEncodedPointer(data, cie->personality_encoding,
                                         &len);
           if (len > size_t(data_end - data))
             return ReportIncomplete(cie);
           data += len;
           break;
         case DW_Z_has_FDE_address_encoding:
           // The CIE's augmentation data holds the pointer encoding to use
           // for addresses in the FDE.
           if (data >= data_end) return ReportIncomplete(cie);
           cie->pointer_encoding = DwarfPointerEncoding(*data++);
           if (!reader_->ValidEncoding(cie->pointer_encoding)) {
             reporter_->InvalidPointerEncoding(cie->offset,
                                               cie->pointer_encoding);
             return false;
           }
           if (!reader_->UsableEncoding(cie->pointer_encoding)) {
             reporter_->UnusablePointerEncoding(cie->offset,
                                                cie->pointer_encoding);
             return false;
           }
           break;
         case DW_Z_is_signal_trampoline:
           // Frames using this CIE are signal delivery frames.
           cie->has_z_signal_frame = true;
           break;
         default:
           // An augmentation we don't recognize.
           reporter_->UnrecognizedAugmentation(cie->offset, cie->augmentation);
           return false;
       }
     }
   }
   // The CIE's instructions start here.
   cie->instructions = cursor;
   return true;
 }
 bool CallFrameInfo::ReadFDEFields(FDE *fde) {
   const char *cursor = fde->fields;
   size_t size;
   fde->address = reader_->ReadEncodedPointer(cursor, fde->cie->pointer_encoding,
                                              &size);
   if (size > size_t(fde->end - cursor))
     return ReportIncomplete(fde);
   cursor += size;
   reader_->SetFunctionBase(fde->address);
   // For the length, we strip off the upper nybble of the encoding used for
   // the starting address.
   DwarfPointerEncoding length_encoding =
     DwarfPointerEncoding(fde->cie->pointer_encoding & 0x0f);
   fde->size = reader_->ReadEncodedPointer(cursor, length_encoding, &size);
   if (size > size_t(fde->end - cursor))
     return ReportIncomplete(fde);
   cursor += size;
   // If the CIE has a 'z' augmentation string, then augmentation data
   // appears here.
   if (fde->cie->has_z_augmentation) {
     uint64_t data_size = reader_->ReadUnsignedLEB128(cursor, &size);
     if (size_t(fde->end - cursor) < size + data_size)
       return ReportIncomplete(fde);
     cursor += size;
     // In the abstract, we should walk the augmentation string, and extract
     // items from the FDE's augmentation data as we encounter augmentation
     // string characters that specify their presence: the ordering of items
     // in the augmentation string determines the arrangement of values in
     // the augmentation data.
     //
     // In practice, there's only ever one value in FDE augmentation data
     // that we support --- the LSDA pointer --- and we have to bail if we
     // see any unrecognized augmentation string characters. So if there is
     // anything here at all, we know what it is, and where it starts.
     if (fde->cie->has_z_lsda) {
       // Check whether the LSDA's pointer encoding is usable now: only once
       // we've parsed the FDE's starting address do we call reader_->
       // SetFunctionBase, so that the DW_EH_PE_funcrel encoding becomes
       // usable.
       if (!reader_->UsableEncoding(fde->cie->lsda_encoding)) {
         reporter_->UnusablePointerEncoding(fde->cie->offset,
                                            fde->cie->lsda_encoding);
         return false;
       }
       fde->lsda_address =
         reader_->ReadEncodedPointer(cursor, fde->cie->lsda_encoding, &size);
       if (size > data_size)
         return ReportIncomplete(fde);
       // Ideally, we would also complain here if there were unconsumed
       // augmentation data.
     }
     cursor += data_size;
   }
   // The FDE's instructions start after those.
   fde->instructions = cursor;
   return true;
 }
 bool CallFrameInfo::Start() {
   const char *buffer_end = buffer_ + buffer_length_;
   const char *cursor;
   bool all_ok = true;
   const char *entry_end;
   bool ok;
   // Traverse all the entries in buffer_, skipping CIEs and offering
   // FDEs to the handler.
   for (cursor = buffer_; cursor < buffer_end;
        cursor = entry_end, all_ok = all_ok && ok) {
     FDE fde;
     // Make it easy to skip this entry with 'continue': assume that
     // things are not okay until we've checked all the data, and
     // prepare the address of the next entry.
     ok = false;
     // Read the entry's prologue.
     if (!ReadEntryPrologue(cursor, &fde)) {
       if (!fde.end) {
         // If we couldn't even figure out this entry's extent, then we
         // must stop processing entries altogether.
         all_ok = false;
         break;
       }
       entry_end = fde.end;
       continue;
     }
     // The next iteration picks up after this entry.
     entry_end = fde.end;
     // Did we see an .eh_frame terminating mark?
     if (fde.kind == kTerminator) {
       // If there appears to be more data left in the section after the
       // terminating mark, warn the user. But this is just a warning;
       // we leave all_ok true.
       if (fde.end < buffer_end) reporter_->EarlyEHTerminator(fde.offset);
       break;
     }
     // In this loop, we skip CIEs. We only parse them fully when we
     // parse an FDE that refers to them. This limits our memory
     // consumption (beyond the buffer itself) to that needed to
     // process the largest single entry.
     if (fde.kind != kFDE) {
       ok = true;
       continue;
     }
     // Validate the CIE pointer.
     if (fde.id > buffer_length_) {
       reporter_->CIEPointerOutOfRange(fde.offset, fde.id);
       continue;
     }
     CIE cie;
     // Parse this FDE's CIE header.
     if (!ReadEntryPrologue(buffer_ + fde.id, &cie))
       continue;
     // This had better be an actual CIE.
     if (cie.kind != kCIE) {
       reporter_->BadCIEId(fde.offset, fde.id);
       continue;
     }
     if (!ReadCIEFields(&cie))
       continue;
     // We now have the values that govern both the CIE and the FDE.
     cie.cie = &cie;
     fde.cie = &cie;
     // Parse the FDE's header.
     if (!ReadFDEFields(&fde))
       continue;
     // Call Entry to ask the consumer if they're interested.
     if (!handler_->Entry(fde.offset, fde.address, fde.size,
                          cie.version, cie.augmentation,
                          cie.return_address_register)) {
       // The handler isn't interested in this entry. That's not an error.
       ok = true;
       continue;
     }
     if (cie.has_z_augmentation) {
       // Report the personality routine address, if we have one.
       if (cie.has_z_personality) {
         if (!handler_
             ->PersonalityRoutine(cie.personality_address,
                                  IsIndirectEncoding(cie.personality_encoding)))
           continue;
       }
       // Report the language-specific data area address, if we have one.
       if (cie.has_z_lsda) {
         if (!handler_
             ->LanguageSpecificDataArea(fde.lsda_address,
                                        IsIndirectEncoding(cie.lsda_encoding)))
           continue;
       }
       // If this is a signal-handling frame, report that.
       if (cie.has_z_signal_frame) {
         if (!handler_->SignalHandler())
           continue;
       }
     }
     // Interpret the CIE's instructions, and then the FDE's instructions.
     State state(reader_, handler_, reporter_, fde.address);
     ok = state.InterpretCIE(cie) && state.InterpretFDE(fde);
     // Tell the ByteReader that the function start address from the
     // FDE header is no longer valid.
     reader_->ClearFunctionBase();
     // Report the end of the entry.
     handler_->End();
   }
   return all_ok;
 }
 const char *CallFrameInfo::KindName(EntryKind kind) {
   if (kind == CallFrameInfo::kUnknown)
     return "entry";
   else if (kind == CallFrameInfo::kCIE)
     return "common information entry";
   else if (kind == CallFrameInfo::kFDE)
     return "frame description entry";
   else {
     MOZ_ASSERT (kind == CallFrameInfo::kTerminator);
     return ".eh_frame sequence terminator";
   }
 }
 bool CallFrameInfo::ReportIncomplete(Entry *entry) {
   reporter_->Incomplete(entry->offset, entry->kind);
   return false;
 }
 void CallFrameInfo::Reporter::Incomplete(uint64 offset,
                                          CallFrameInfo::EntryKind kind) {
   char buf[300];
   snprintf(buf, sizeof(buf),
            "%s: CFI %s at offset 0x%llx in '%s': entry ends early\n",
            filename_.c_str(), CallFrameInfo::KindName(kind), offset,
            section_.c_str());
   log_(buf);
 }
 void CallFrameInfo::Reporter::EarlyEHTerminator(uint64 offset) {
   char buf[300];
   snprintf(buf, sizeof(buf),
            "%s: CFI at offset 0x%llx in '%s': saw end-of-data marker"
            " before end of section contents\n",
            filename_.c_str(), offset, section_.c_str());
   log_(buf);
 }
 void CallFrameInfo::Reporter::CIEPointerOutOfRange(uint64 offset,
                                                    uint64 cie_offset) {
   char buf[300];
   snprintf(buf, sizeof(buf),
            "%s: CFI frame description entry at offset 0x%llx in '%s':"
            " CIE pointer is out of range: 0x%llx\n",
            filename_.c_str(), offset, section_.c_str(), cie_offset);
   log_(buf);
 }
 void CallFrameInfo::Reporter::BadCIEId(uint64 offset, uint64 cie_offset) {
   char buf[300];
   snprintf(buf, sizeof(buf),
            "%s: CFI frame description entry at offset 0x%llx in '%s':"
            " CIE pointer does not point to a CIE: 0x%llx\n",
            filename_.c_str(), offset, section_.c_str(), cie_offset);
   log_(buf);
 }
 void CallFrameInfo::Reporter::UnrecognizedVersion(uint64 offset, int version) {
   char buf[300];
   snprintf(buf, sizeof(buf),
            "%s: CFI frame description entry at offset 0x%llx in '%s':"
            " CIE specifies unrecognized version: %d\n",
            filename_.c_str(), offset, section_.c_str(), version);
   log_(buf);
 }
 void CallFrameInfo::Reporter::UnrecognizedAugmentation(uint64 offset,
                                                        const string &aug) {
   char buf[300];
   snprintf(buf, sizeof(buf),
            "%s: CFI frame description entry at offset 0x%llx in '%s':"
            " CIE specifies unrecognized augmentation: '%s'\n",
            filename_.c_str(), offset, section_.c_str(), aug.c_str());
   log_(buf);
 }
 void CallFrameInfo::Reporter::InvalidPointerEncoding(uint64 offset,
                                                      uint8 encoding) {
   char buf[300];
   snprintf(buf, sizeof(buf),
            "%s: CFI common information entry at offset 0x%llx in '%s':"
            " 'z' augmentation specifies invalid pointer encoding: 0x%02x\n",
            filename_.c_str(), offset, section_.c_str(), encoding);
   log_(buf);
 }
 void CallFrameInfo::Reporter::UnusablePointerEncoding(uint64 offset,
                                                       uint8 encoding) {
   char buf[300];
   snprintf(buf, sizeof(buf),
            "%s: CFI common information entry at offset 0x%llx in '%s':"
            " 'z' augmentation specifies a pointer encoding for which"
            " we have no base address: 0x%02x\n",
            filename_.c_str(), offset, section_.c_str(), encoding);
   log_(buf);
 }
 void CallFrameInfo::Reporter::RestoreInCIE(uint64 offset, uint64 insn_offset) {
   char buf[300];
   snprintf(buf, sizeof(buf),
            "%s: CFI common information entry at offset 0x%llx in '%s':"
            " the DW_CFA_restore instruction at offset 0x%llx"
            " cannot be used in a common information entry\n",
            filename_.c_str(), offset, section_.c_str(), insn_offset);
   log_(buf);
 }
 void CallFrameInfo::Reporter::BadInstruction(uint64 offset,
                                              CallFrameInfo::EntryKind kind,
                                              uint64 insn_offset) {
   char buf[300];
   snprintf(buf, sizeof(buf),
            "%s: CFI %s at offset 0x%llx in section '%s':"
            " the instruction at offset 0x%llx is unrecognized\n",
            filename_.c_str(), CallFrameInfo::KindName(kind),
            offset, section_.c_str(), insn_offset);
   log_(buf);
 }
 void CallFrameInfo::Reporter::NoCFARule(uint64 offset,
                                         CallFrameInfo::EntryKind kind,
                                         uint64 insn_offset) {
   char buf[300];
   snprintf(buf, sizeof(buf),
            "%s: CFI %s at offset 0x%llx in section '%s':"
            " the instruction at offset 0x%llx assumes that a CFA rule has"
            " been set, but none has been set\n",
            filename_.c_str(), CallFrameInfo::KindName(kind), offset,
            section_.c_str(), insn_offset);
   log_(buf);
 }
 void CallFrameInfo::Reporter::EmptyStateStack(uint64 offset,
                                               CallFrameInfo::EntryKind kind,
                                               uint64 insn_offset) {
   char buf[300];
   snprintf(buf, sizeof(buf),
            "%s: CFI %s at offset 0x%llx in section '%s':"
            " the DW_CFA_restore_state instruction at offset 0x%llx"
            " should pop a saved state from the stack, but the stack is empty\n",
            filename_.c_str(), CallFrameInfo::KindName(kind), offset,
            section_.c_str(), insn_offset);
   log_(buf);
 }
 void CallFrameInfo::Reporter::ClearingCFARule(uint64 offset,
                                               CallFrameInfo::EntryKind kind,
                                               uint64 insn_offset) {
   char buf[300];
   snprintf(buf, sizeof(buf),
            "%s: CFI %s at offset 0x%llx in section '%s':"
            " the DW_CFA_restore_state instruction at offset 0x%llx"
            " would clear the CFA rule in effect\n",
            filename_.c_str(), CallFrameInfo::KindName(kind), offset,
            section_.c_str(), insn_offset);
   log_(buf);
 }
 const unsigned int DwarfCFIToModule::RegisterNames::I386() {
   /*
 "$eax", "$ecx", "$edx", "$ebx", "$esp", "$ebp", "$esi", "$edi",
 "$eip", "$eflags", "$unused1",
 "$st0", "$st1", "$st2", "$st3", "$st4", "$st5", "$st6", "$st7",
 "$unused2", "$unused3",
 "$xmm0", "$xmm1", "$xmm2", "$xmm3", "$xmm4", "$xmm5", "$xmm6", "$xmm7",
 "$mm0", "$mm1", "$mm2", "$mm3", "$mm4", "$mm5", "$mm6", "$mm7",
 "$fcw", "$fsw", "$mxcsr",
 "$es", "$cs", "$ss", "$ds", "$fs", "$gs", "$unused4", "$unused5",
 "$tr", "$ldtr"
   */
   return 8 + 3 + 8 + 2 + 8 + 8 + 3 + 8 + 2;
 }
 const unsigned int DwarfCFIToModule::RegisterNames::X86_64() {
   /*
 "$rax", "$rdx", "$rcx", "$rbx", "$rsi", "$rdi", "$rbp", "$rsp",
 "$r8",  "$r9",  "$r10", "$r11", "$r12", "$r13", "$r14", "$r15",
 "$rip",
 "$xmm0","$xmm1","$xmm2", "$xmm3", "$xmm4", "$xmm5", "$xmm6", "$xmm7",
 "$xmm8","$xmm9","$xmm10","$xmm11","$xmm12","$xmm13","$xmm14","$xmm15",
 "$st0", "$st1", "$st2", "$st3", "$st4", "$st5", "$st6", "$st7",
 "$mm0", "$mm1", "$mm2", "$mm3", "$mm4", "$mm5", "$mm6", "$mm7",
 "$rflags",
 "$es", "$cs", "$ss", "$ds", "$fs", "$gs", "$unused1", "$unused2",
 "$fs.base", "$gs.base", "$unused3", "$unused4",
 "$tr", "$ldtr",
 "$mxcsr", "$fcw", "$fsw"
   */
   return 8 + 8 + 1 + 8 + 8 + 8 + 8 + 1 + 8 + 4 + 2 + 3;
 }
 // Per ARM IHI 0040A, section 3.1
 const unsigned int DwarfCFIToModule::RegisterNames::ARM() {
   /*
 "r0",  "r1",  "r2",  "r3",  "r4",  "r5",  "r6",  "r7",
 "r8",  "r9",  "r10", "r11", "r12", "sp",  "lr",  "pc",
 "f0",  "f1",  "f2",  "f3",  "f4",  "f5",  "f6",  "f7",
 "fps", "cpsr", "",   "",    "",    "",    "",    "",
 "",    "",    "",    "",    "",    "",    "",    "",
 "",    "",    "",    "",    "",    "",    "",    "",
 "",    "",    "",    "",    "",    "",    "",    "",
 "",    "",    "",    "",    "",    "",    "",    "",
 "s0",  "s1",  "s2",  "s3",  "s4",  "s5",  "s6",  "s7",
 "s8",  "s9",  "s10", "s11", "s12", "s13", "s14", "s15",
 "s16", "s17", "s18", "s19", "s20", "s21", "s22", "s23",
 "s24", "s25", "s26", "s27", "s28", "s29", "s30", "s31",
 "f0",  "f1",  "f2",  "f3",  "f4",  "f5",  "f6",  "f7"
   */
   return 13 * 8;
 }
 bool DwarfCFIToModule::Entry(size_t offset, uint64 address, uint64 length,
                              uint8 version, const string &augmentation,
                              unsigned return_address) {
   if (DEBUG_DWARF)
     printf("LUL.DW DwarfCFIToModule::Entry 0x%llx,+%lld\n", address, length);
   summ_->Entry(address, length);
   // If dwarf2reader::CallFrameInfo can handle this version and
   // augmentation, then we should be okay with that, so there's no
   // need to check them here.
   // Get ready to collect entries.
   return_address_ = return_address;
   // Breakpad STACK CFI records must provide a .ra rule, but DWARF CFI
   // may not establish any rule for .ra if the return address column
   // is an ordinary register, and that register holds the return
   // address on entry to the function. So establish an initial .ra
   // rule citing the return address register.
   if (return_address_ < num_dw_regs_) {
     summ_->Rule(address, return_address_, return_address, 0, false);
   }
   return true;
 }
 const UniqueString* DwarfCFIToModule::RegisterName(int i) {
   if (i < 0) {
     MOZ_ASSERT(i == kCFARegister);
     return ustr__ZDcfa();
   }
   unsigned reg = i;
   if (reg == return_address_)
     return ustr__ZDra();
   char buf[30];
   sprintf(buf, "dwarf_reg_%u", reg);
   return ToUniqueString(buf);
 }
 bool DwarfCFIToModule::UndefinedRule(uint64 address, int reg) {
   reporter_->UndefinedNotSupported(entry_offset_, RegisterName(reg));
   // Treat this as a non-fatal error.
   return true;
 }
 bool DwarfCFIToModule::SameValueRule(uint64 address, int reg) {
   if (DEBUG_DWARF)
     printf("LUL.DW  0x%llx: old r%d = Same\n", address, reg);
   // reg + 0
   summ_->Rule(address, reg, reg, 0, false);
   return true;
 }
 bool DwarfCFIToModule::OffsetRule(uint64 address, int reg,
                                   int base_register, long offset) {
   if (DEBUG_DWARF)
     printf("LUL.DW  0x%llx: old r%d = *(r%d + %ld)\n",
            address, reg, base_register, offset);
   // *(base_register + offset)
   summ_->Rule(address, reg, base_register, offset, true);
   return true;
 }
 bool DwarfCFIToModule::ValOffsetRule(uint64 address, int reg,
                                      int base_register, long offset) {
   if (DEBUG_DWARF)
     printf("LUL.DW  0x%llx: old r%d = r%d + %ld\n",
            address, reg, base_register, offset);
   // base_register + offset
   summ_->Rule(address, reg, base_register, offset, false);
   return true;
 }
 bool DwarfCFIToModule::RegisterRule(uint64 address, int reg,
                                     int base_register) {
   if (DEBUG_DWARF)
     printf("LUL.DW  0x%llx: old r%d = r%d\n", address, reg, base_register);
   // base_register + 0
   summ_->Rule(address, reg, base_register, 0, false);
   return true;
 }
 bool DwarfCFIToModule::ExpressionRule(uint64 address, int reg,
                                       const string &expression) {
   reporter_->ExpressionsNotSupported(entry_offset_, RegisterName(reg));
   // Treat this as a non-fatal error.
   return true;
 }
 bool DwarfCFIToModule::ValExpressionRule(uint64 address, int reg,
                                          const string &expression) {
   reporter_->ExpressionsNotSupported(entry_offset_, RegisterName(reg));
   // Treat this as a non-fatal error.
   return true;
 }
 bool DwarfCFIToModule::End() {
   //module_->AddStackFrameEntry(entry_);
   if (DEBUG_DWARF)
     printf("LUL.DW DwarfCFIToModule::End()\n");
   summ_->End();
   return true;
 }
 void DwarfCFIToModule::Reporter::UndefinedNotSupported(
     size_t offset,
     const UniqueString* reg) {
   char buf[300];
   snprintf(buf, sizeof(buf),
            "DwarfCFIToModule::Reporter::UndefinedNotSupported()\n");
   log_(buf);
   //BPLOG(INFO) << file_ << ", section '" << section_
   //  << "': the call frame entry at offset 0x"
   //  << std::setbase(16) << offset << std::setbase(10)
   //  << " sets the rule for register '" << FromUniqueString(reg)
   //  << "' to 'undefined', but the Breakpad symbol file format cannot "
   //  << " express this";
 }
 // FIXME: move this somewhere sensible
 static bool is_power_of_2(uint64_t n)
 {
   int i, nSetBits = 0;
   for (i = 0; i < 8*(int)sizeof(n); i++) {
     if ((n & ((uint64_t)1) << i) != 0)
       nSetBits++;
   }
   return nSetBits <= 1;
 }
 void DwarfCFIToModule::Reporter::ExpressionsNotSupported(
     size_t offset,
     const UniqueString* reg) {
   static uint64_t n_complaints = 0; // This isn't threadsafe
   n_complaints++;
   if (!is_power_of_2(n_complaints))
     return;
   char buf[300];
   snprintf(buf, sizeof(buf),
            "DwarfCFIToModule::Reporter::"
            "ExpressionsNotSupported(shown %llu times)\n",
            (unsigned long long int)n_complaints);
   log_(buf);
   //BPLOG(INFO) << file_ << ", section '" << section_
   //  << "': the call frame entry at offset 0x"
   //  << std::setbase(16) << offset << std::setbase(10)
   //  << " uses a DWARF expression to describe how to recover register '"
   //  << FromUniqueString(reg) << "', but this translator cannot yet "
   //  << "translate DWARF expressions to Breakpad postfix expressions (shown "
   //  << n_complaints << " times)";
 }
 } // namespace lul

The Tor Browser / annotate

tools/profiler/LulDwarf.cpp@97036ab72558 (annotated)

tools/profiler/LulDwarf.cpp