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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
// Copyright (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 "mozilla/Sprintf.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, REG can be
// recovered using this rule. If REG 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 reg) 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 override { return CFIR_UNDEFINED_RULE; }
bool Handle(Handler* handler, uint64 address, int reg) const override {
return handler->UndefinedRule(address, reg);
}
bool operator==(const Rule& rhs) const override {
if (rhs.getTag() != CFIR_UNDEFINED_RULE) return false;
return true;
}
Rule* Copy() const override { 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 override { return CFIR_SAME_VALUE_RULE; }
bool Handle(Handler* handler, uint64 address, int reg) const override {
return handler->SameValueRule(address, reg);
}
bool operator==(const Rule& rhs) const override {
if (rhs.getTag() != CFIR_SAME_VALUE_RULE) return false;
return true;
}
Rule* Copy() const override { 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 override { return CFIR_OFFSET_RULE; }
bool Handle(Handler* handler, uint64 address, int reg) const override {
return handler->OffsetRule(address, reg, base_register_, offset_);
}
bool operator==(const Rule& rhs) const override {
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 override { 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 override { return CFIR_VAL_OFFSET_RULE; }
bool Handle(Handler* handler, uint64 address, int reg) const override {
return handler->ValOffsetRule(address, reg, base_register_, offset_);
}
bool operator==(const Rule& rhs) const override {
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 override { return new ValOffsetRule(*this); }
void SetBaseRegister(unsigned reg) override { base_register_ = reg; }
void SetOffset(long long offset) override { 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 override { return CFIR_REGISTER_RULE; }
bool Handle(Handler* handler, uint64 address, int reg) const override {
return handler->RegisterRule(address, reg, register_number_);
}
bool operator==(const Rule& rhs) const override {
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 override { 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 override { return CFIR_EXPRESSION_RULE; }
bool Handle(Handler* handler, uint64 address, int reg) const override {
return handler->ExpressionRule(address, reg, expression_);
}
bool operator==(const Rule& rhs) const override {
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 override { 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 override { return CFIR_VAL_EXPRESSION_RULE; }
bool Handle(Handler* handler, uint64 address, int reg) const override {
return handler->ValExpressionRule(address, reg, expression_);
}
bool operator==(const Rule& rhs) const override {
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 override { 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 4 (there was never a
// version 2 of CFI data). For .eh_frame, we handle versions 1 and 4 as well;
// the difference between those versions seems to be the same as for
// .debug_frame.
if (cie->version < 1 || cie->version > 4) {
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;
}
}
if (cie->version >= 4) {
// Check that the address_size and segment_size fields are plausible.
if (cie->end - cursor < 2) {
return ReportIncomplete(cie);
}
uint8_t address_size = reader_->ReadOneByte(cursor);
cursor++;
if (address_size != sizeof(void*)) {
// This is not per-se invalid CFI. But we can reasonably expect to
// be running on a target of the same word size as the CFI is for,
// so we reject this case.
reporter_->InvalidDwarf4Artefact(cie->offset, "Invalid address_size");
return false;
}
uint8_t segment_size = reader_->ReadOneByte(cursor);
cursor++;
if (segment_size != 0) {
// This is also not per-se invalid CFI, but we don't currently handle
// the case of non-zero |segment_size|.
reporter_->InvalidDwarf4Artefact(cie->offset, "Invalid segment_size");
return false;
}
// We only continue parsing if |segment_size| is zero. If this routine
// is ever changed to allow non-zero |segment_size|, then
// ReadFDEFields() below will have to be changed to match, per comments
// there.
}
// 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;
// At this point, for Dwarf 4 and above, we are assuming that the
// associated CIE has its |segment_size| field equal to zero. This is
// checked for in ReadCIEFields() above. If ReadCIEFields() is ever
// changed to allow non-zero |segment_size| CIEs then we will have to read
// the segment_selector value at this point.
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];
SprintfLiteral(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];
SprintfLiteral(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];
SprintfLiteral(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];
SprintfLiteral(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];
SprintfLiteral(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];
SprintfLiteral(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::InvalidDwarf4Artefact(uint64 offset,
const char* what) {
char* what_safe = strndup(what, 100);
char buf[300];
SprintfLiteral(buf,
"%s: CFI frame description entry at offset 0x%llx in '%s':"
" CIE specifies invalid Dwarf4 artefact: %s\n",
filename_.c_str(), offset, section_.c_str(), what_safe);
log_(buf);
free(what_safe);
}
void CallFrameInfo::Reporter::InvalidPointerEncoding(uint64 offset,
uint8 encoding) {
char buf[300];
SprintfLiteral(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];
SprintfLiteral(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];
SprintfLiteral(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];
SprintfLiteral(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];
SprintfLiteral(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];
SprintfLiteral(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];
SprintfLiteral(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);
}
unsigned int DwarfCFIToModule::RegisterNames::I386() {
/*
8 "$eax", "$ecx", "$edx", "$ebx", "$esp", "$ebp", "$esi", "$edi",
3 "$eip", "$eflags", "$unused1",
8 "$st0", "$st1", "$st2", "$st3", "$st4", "$st5", "$st6", "$st7",
2 "$unused2", "$unused3",
8 "$xmm0", "$xmm1", "$xmm2", "$xmm3", "$xmm4", "$xmm5", "$xmm6", "$xmm7",
8 "$mm0", "$mm1", "$mm2", "$mm3", "$mm4", "$mm5", "$mm6", "$mm7",
3 "$fcw", "$fsw", "$mxcsr",
8 "$es", "$cs", "$ss", "$ds", "$fs", "$gs", "$unused4", "$unused5",
2 "$tr", "$ldtr"
*/
return 8 + 3 + 8 + 2 + 8 + 8 + 3 + 8 + 2;
}
unsigned int