// Copyright 2010 Google LLC
//
// 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 LLC 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>
// Implementation of LineInfo, CompilationUnit,
// and CallFrameInfo. See dwarf2reader.h for details.
#ifdef HAVE_CONFIG_H
#include <config.h> // Must come first
#endif
#include "common/dwarf/dwarf2reader.h"
#include <stdint.h>
#include <stdio.h>
#include <string.h>
#include <algorithm>
#include <map>
#include <memory>
#include <stack>
#include <string>
#include <utility>
#include <sys/stat.h>
#include "common/dwarf/bytereader-inl.h"
#include "common/dwarf/bytereader.h"
#include "common/dwarf/line_state_machine.h"
#include "common/using_std_string.h"
#include "google_breakpad/common/breakpad_types.h"
namespace google_breakpad {
const SectionMap::const_iterator GetSectionByName(const SectionMap&
sections, const char *name) {
assert(name[0] == '.');
auto iter = sections.find(name);
if (iter != sections.end())
return iter;
std::string macho_name("__");
macho_name += name + 1;
iter = sections.find(macho_name);
return iter;
}
CompilationUnit::CompilationUnit(const string& path,
const SectionMap& sections, uint64_t offset,
ByteReader* reader, Dwarf2Handler* handler)
: path_(path), offset_from_section_start_(offset), reader_(reader),
sections_(sections), handler_(handler), abbrevs_(),
string_buffer_(NULL), string_buffer_length_(0),
line_string_buffer_(NULL), line_string_buffer_length_(0),
str_offsets_buffer_(NULL), str_offsets_buffer_length_(0),
addr_buffer_(NULL), addr_buffer_length_(0),
is_split_dwarf_(false), is_type_unit_(false), dwo_id_(0), dwo_name_(),
skeleton_dwo_id_(0), addr_base_(0),
str_offsets_base_(0), have_checked_for_dwp_(false),
should_process_split_dwarf_(false), low_pc_(0),
has_source_line_info_(false), source_line_offset_(0) {}
// Initialize a compilation unit from a .dwo or .dwp file.
// In this case, we need the .debug_addr section from the
// executable file that contains the corresponding skeleton
// compilation unit. We also inherit the Dwarf2Handler from
// the executable file, and call it as if we were still
// processing the original compilation unit.
void CompilationUnit::SetSplitDwarf(uint64_t addr_base,
uint64_t dwo_id) {
is_split_dwarf_ = true;
addr_base_ = addr_base;
skeleton_dwo_id_ = dwo_id;
}
// Read a DWARF2/3 abbreviation section.
// Each abbrev consists of a abbreviation number, a tag, a byte
// specifying whether the tag has children, and a list of
// attribute/form pairs.
// The list of forms is terminated by a 0 for the attribute, and a
// zero for the form. The entire abbreviation section is terminated
// by a zero for the code.
void CompilationUnit::ReadAbbrevs() {
if (abbrevs_)
return;
// First get the debug_abbrev section.
SectionMap::const_iterator iter =
GetSectionByName(sections_, ".debug_abbrev");
assert(iter != sections_.end());
abbrevs_ = new std::vector<Abbrev>;
abbrevs_->resize(1);
// The only way to check whether we are reading over the end of the
// buffer would be to first compute the size of the leb128 data by
// reading it, then go back and read it again.
const uint8_t* abbrev_start = iter->second.first +
header_.abbrev_offset;
const uint8_t* abbrevptr = abbrev_start;
#ifndef NDEBUG
const uint64_t abbrev_length = iter->second.second - header_.abbrev_offset;
#endif
uint64_t highest_number = 0;
while (1) {
CompilationUnit::Abbrev abbrev;
size_t len;
const uint64_t number = reader_->ReadUnsignedLEB128(abbrevptr, &len);
highest_number = std::max(highest_number, number);
if (number == 0)
break;
abbrev.number = number;
abbrevptr += len;
assert(abbrevptr < abbrev_start + abbrev_length);
const uint64_t tag = reader_->ReadUnsignedLEB128(abbrevptr, &len);
abbrevptr += len;
abbrev.tag = static_cast<enum DwarfTag>(tag);
assert(abbrevptr < abbrev_start + abbrev_length);
abbrev.has_children = reader_->ReadOneByte(abbrevptr);
abbrevptr += 1;
assert(abbrevptr < abbrev_start + abbrev_length);
while (1) {
const uint64_t nametemp = reader_->ReadUnsignedLEB128(abbrevptr, &len);
abbrevptr += len;
assert(abbrevptr < abbrev_start + abbrev_length);
const uint64_t formtemp = reader_->ReadUnsignedLEB128(abbrevptr, &len);
abbrevptr += len;
if (nametemp == 0 && formtemp == 0)
break;
uint64_t value = 0;
if (formtemp == DW_FORM_implicit_const) {
value = reader_->ReadUnsignedLEB128(abbrevptr, &len);
abbrevptr += len;
}
AttrForm abbrev_attr(static_cast<enum DwarfAttribute>(nametemp),
static_cast<enum DwarfForm>(formtemp),
value);
abbrev.attributes.push_back(abbrev_attr);
}
abbrevs_->push_back(abbrev);
}
// Account of cases where entries are out of order.
std::sort(abbrevs_->begin(), abbrevs_->end(),
[](const CompilationUnit::Abbrev& lhs, const CompilationUnit::Abbrev& rhs) {
return lhs.number < rhs.number;
});
// Ensure that there are no missing sections.
assert(abbrevs_->size() == highest_number + 1);
}
// Skips a single DIE's attributes.
const uint8_t* CompilationUnit::SkipDIE(const uint8_t* start,
const Abbrev& abbrev) {
for (AttributeList::const_iterator i = abbrev.attributes.begin();
i != abbrev.attributes.end();
i++) {
start = SkipAttribute(start, i->form_);
}
return start;
}
// Skips a single attribute form's data.
const uint8_t* CompilationUnit::SkipAttribute(const uint8_t* start,
enum DwarfForm form) {
size_t len;
switch (form) {
case DW_FORM_indirect:
form = static_cast<enum DwarfForm>(reader_->ReadUnsignedLEB128(start,
&len));
start += len;
return SkipAttribute(start, form);
case DW_FORM_flag_present:
case DW_FORM_implicit_const:
return start;
case DW_FORM_addrx1:
case DW_FORM_data1:
case DW_FORM_flag:
case DW_FORM_ref1:
case DW_FORM_strx1:
return start + 1;
case DW_FORM_addrx2:
case DW_FORM_ref2:
case DW_FORM_data2:
case DW_FORM_strx2:
return start + 2;
case DW_FORM_addrx3:
case DW_FORM_strx3:
return start + 3;
case DW_FORM_addrx4:
case DW_FORM_ref4:
case DW_FORM_data4:
case DW_FORM_strx4:
case DW_FORM_ref_sup4:
return start + 4;
case DW_FORM_ref8:
case DW_FORM_data8:
case DW_FORM_ref_sig8:
case DW_FORM_ref_sup8:
return start + 8;
case DW_FORM_data16:
return start + 16;
case DW_FORM_string:
return start + strlen(reinterpret_cast<const char*>(start)) + 1;
case DW_FORM_udata:
case DW_FORM_ref_udata:
case DW_FORM_strx:
case DW_FORM_GNU_str_index:
case DW_FORM_GNU_addr_index:
case DW_FORM_addrx:
case DW_FORM_rnglistx:
case DW_FORM_loclistx:
reader_->ReadUnsignedLEB128(start, &len);
return start + len;
case DW_FORM_sdata:
reader_->ReadSignedLEB128(start, &len);
return start + len;
case DW_FORM_addr:
return start + reader_->AddressSize();
case DW_FORM_ref_addr:
// DWARF2 and 3/4 differ on whether ref_addr is address size or
// offset size.
assert(header_.version >= 2);
if (header_.version == 2) {
return start + reader_->AddressSize();
} else if (header_.version >= 3) {
return start + reader_->OffsetSize();
}
break;
case DW_FORM_block1:
return start + 1 + reader_->ReadOneByte(start);
case DW_FORM_block2:
return start + 2 + reader_->ReadTwoBytes(start);
case DW_FORM_block4:
return start + 4 + reader_->ReadFourBytes(start);
case DW_FORM_block:
case DW_FORM_exprloc: {
uint64_t size = reader_->ReadUnsignedLEB128(start, &len);
return start + size + len;
}
case DW_FORM_strp:
case DW_FORM_line_strp:
case DW_FORM_strp_sup:
case DW_FORM_sec_offset:
return start + reader_->OffsetSize();
}
fprintf(stderr,"Unhandled form type");
return NULL;
}
// Read the abbreviation offset from a compilation unit header.
size_t CompilationUnit::ReadAbbrevOffset(const uint8_t* headerptr) {
assert(headerptr + reader_->OffsetSize() < buffer_ + buffer_length_);
header_.abbrev_offset = reader_->ReadOffset(headerptr);
return reader_->OffsetSize();
}
// Read the address size from a compilation unit header.
size_t CompilationUnit::ReadAddressSize(const uint8_t* headerptr) {
// Compare against less than or equal because this may be the last
// section in the file.
assert(headerptr + 1 <= buffer_ + buffer_length_);
header_.address_size = reader_->ReadOneByte(headerptr);
reader_->SetAddressSize(header_.address_size);
return 1;
}
// Read the DWO id from a split or skeleton compilation unit header.
size_t CompilationUnit::ReadDwoId(const uint8_t* headerptr) {
assert(headerptr + 8 <= buffer_ + buffer_length_);
dwo_id_ = reader_->ReadEightBytes(headerptr);
return 8;
}
// Read the type signature from a type or split type compilation unit header.
size_t CompilationUnit::ReadTypeSignature(const uint8_t* headerptr) {
assert(headerptr + 8 <= buffer_ + buffer_length_);
type_signature_ = reader_->ReadEightBytes(headerptr);
return 8;
}
// Read the DWO id from a split or skeleton compilation unit header.
size_t CompilationUnit::ReadTypeOffset(const uint8_t* headerptr) {
assert(headerptr + reader_->OffsetSize() < buffer_ + buffer_length_);
type_offset_ = reader_->ReadOffset(headerptr);
return reader_->OffsetSize();
}
// Read a DWARF header. The header is variable length in DWARF3 and DWARF4
// (and DWARF2 as extended by most compilers), and consists of an length
// field, a version number, the offset in the .debug_abbrev section for our
// abbrevs, and an address size. DWARF5 adds a unit_type to distinguish
// between partial-, full-, skeleton-, split-, and type- compilation units.
void CompilationUnit::ReadHeader() {
const uint8_t* headerptr = buffer_;
size_t initial_length_size;
assert(headerptr + 4 < buffer_ + buffer_length_);
const uint64_t initial_length
= reader_->ReadInitialLength(headerptr, &initial_length_size);
headerptr += initial_length_size;
header_.length = initial_length;
assert(headerptr + 2 < buffer_ + buffer_length_);
header_.version = reader_->ReadTwoBytes(headerptr);
headerptr += 2;
if (header_.version <= 4) {
// Older versions of dwarf have a relatively simple structure.
headerptr += ReadAbbrevOffset(headerptr);
headerptr += ReadAddressSize(headerptr);
} else {
// DWARF5 adds a unit_type field, and various fields based on unit_type.
assert(headerptr + 1 < buffer_ + buffer_length_);
uint8_t unit_type = reader_->ReadOneByte(headerptr);
headerptr += 1;
headerptr += ReadAddressSize(headerptr);
headerptr += ReadAbbrevOffset(headerptr);
switch (unit_type) {
case DW_UT_compile:
case DW_UT_partial:
// nothing else to read
break;
case DW_UT_skeleton:
case DW_UT_split_compile:
headerptr += ReadDwoId(headerptr);
break;
case DW_UT_type:
case DW_UT_split_type:
is_type_unit_ = true;
headerptr += ReadTypeSignature(headerptr);
headerptr += ReadTypeOffset(headerptr);
break;
default:
fprintf(stderr, "Unhandled compilation unit type 0x%x", unit_type);
break;
}
}
after_header_ = headerptr;
// This check ensures that we don't have to do checking during the
// reading of DIEs. header_.length does not include the size of the
// initial length.
assert(buffer_ + initial_length_size + header_.length <=
buffer_ + buffer_length_);
}
uint64_t CompilationUnit::Start() {
// First get the debug_info section.
SectionMap::const_iterator iter =
GetSectionByName(sections_, ".debug_info");
assert(iter != sections_.end());
// Set up our buffer
buffer_ = iter->second.first + offset_from_section_start_;
if (is_split_dwarf_) {
iter = GetSectionByName(sections_, ".debug_info_offset");
assert(iter != sections_.end());
buffer_length_ = iter->second.second;
} else {
buffer_length_ = iter->second.second - offset_from_section_start_;
}
// Read the header
ReadHeader();
// Figure out the real length from the end of the initial length to
// the end of the compilation unit, since that is the value we
// return.
uint64_t ourlength = header_.length;
if (reader_->OffsetSize() == 8)
ourlength += 12;
else
ourlength += 4;
// See if the user wants this compilation unit, and if not, just return.
if (!handler_->StartCompilationUnit(offset_from_section_start_,
reader_->AddressSize(),
reader_->OffsetSize(),
header_.length,
header_.version))
return ourlength;
else if (header_.version == 5 && is_type_unit_)
return ourlength;
// Otherwise, continue by reading our abbreviation entries.
ReadAbbrevs();
// Set the string section if we have one.
iter = GetSectionByName(sections_, ".debug_str");
if (iter != sections_.end()) {
string_buffer_ = iter->second.first;
string_buffer_length_ = iter->second.second;
}
iter = GetSectionByName(sections_, ".debug_line");
if (iter != sections_.end()) {
line_buffer_ = iter->second.first;
line_buffer_length_ = iter->second.second;
}
// Set the line string section if we have one.
iter = GetSectionByName(sections_, ".debug_line_str");
if (iter != sections_.end()) {
line_string_buffer_ = iter->second.first;
line_string_buffer_length_ = iter->second.second;
}
// Set the string offsets section if we have one.
iter = GetSectionByName(sections_, ".debug_str_offsets");
if (iter != sections_.end()) {
str_offsets_buffer_ = iter->second.first;
str_offsets_buffer_length_ = iter->second.second;
}
// Set the address section if we have one.
iter = GetSectionByName(sections_, ".debug_addr");
if (iter != sections_.end()) {
addr_buffer_ = iter->second.first;
addr_buffer_length_ = iter->second.second;
}
// Now that we have our abbreviations, start processing DIE's.
ProcessDIEs();
// If this is a skeleton compilation unit generated with split DWARF,
// and the client needs the full debug info, we need to find the full
// compilation unit in a .dwo or .dwp file.
should_process_split_dwarf_ =
!is_split_dwarf_ && dwo_name_ != NULL && handler_->NeedSplitDebugInfo();
return ourlength;
}
void CompilationUnit::ProcessFormStringIndex(
uint64_t dieoffset, enum DwarfAttribute attr, enum DwarfForm form,
uint64_t str_index) {
const size_t kStringOffsetsTableHeaderSize =
header_.version >= 5 ? (reader_->OffsetSize() == 8 ? 16 : 8) : 0;
const uint8_t* str_offsets_table_after_header = str_offsets_base_ ?
str_offsets_buffer_ + str_offsets_base_ :
str_offsets_buffer_ + kStringOffsetsTableHeaderSize;
const uint8_t* offset_ptr =
str_offsets_table_after_header + str_index * reader_->OffsetSize();
const uint64_t offset = reader_->ReadOffset(offset_ptr);
if (offset >= string_buffer_length_) {
return;
}
const char* str = reinterpret_cast<const char*>(string_buffer_) + offset;
ProcessAttributeString(dieoffset, attr, form, str);
}
// Special function for pre-processing the
// DW_AT_str_offsets_base and DW_AT_addr_base in a DW_TAG_compile_unit die (for
// DWARF v5). We must make sure to find and process the
// DW_AT_str_offsets_base and DW_AT_addr_base attributes before attempting to
// read any string and address attribute in the compile unit.
const uint8_t* CompilationUnit::ProcessOffsetBaseAttribute(
uint64_t dieoffset, const uint8_t* start, enum DwarfAttribute attr,
enum DwarfForm form, uint64_t implicit_const) {
size_t len;
switch (form) {
// DW_FORM_indirect is never used because it is such a space
// waster.
case DW_FORM_indirect:
form = static_cast<enum DwarfForm>(reader_->ReadUnsignedLEB128(start,
&len));
start += len;
return ProcessOffsetBaseAttribute(dieoffset, start, attr, form,
implicit_const);
case DW_FORM_flag_present:
return start;
case DW_FORM_data1:
case DW_FORM_flag:
return start + 1;
case DW_FORM_data2:
return start + 2;
case DW_FORM_data4:
return start + 4;
case DW_FORM_data8:
return start + 8;
case DW_FORM_data16:
// This form is designed for an md5 checksum inside line tables.
return start + 16;
case DW_FORM_string: {
const char* str = reinterpret_cast<const char*>(start);
return start + strlen(str) + 1;
}
case DW_FORM_udata:
reader_->ReadUnsignedLEB128(start, &len);
return start + len;
case DW_FORM_sdata:
reader_->ReadSignedLEB128(start, &len);
return start + len;
case DW_FORM_addr:
reader_->ReadAddress(start);
return start + reader_->AddressSize();
// This is the important one here!
case DW_FORM_sec_offset:
if (attr == DW_AT_str_offsets_base ||
attr == DW_AT_addr_base)
ProcessAttributeUnsigned(dieoffset, attr, form,
reader_->ReadOffset(start));
else
reader_->ReadOffset(start);
return start + reader_->OffsetSize();
case DW_FORM_ref1:
return start + 1;
case DW_FORM_ref2:
return start + 2;
case DW_FORM_ref4:
return start + 4;
case DW_FORM_ref8:
return start + 8;
case DW_FORM_ref_udata:
reader_->ReadUnsignedLEB128(start, &len);
return start + len;
case DW_FORM_ref_addr:
// DWARF2 and 3/4 differ on whether ref_addr is address size or
// offset size.
assert(header_.version >= 2);
if (header_.version == 2) {
reader_->ReadAddress(start);
return start + reader_->AddressSize();
} else if (header_.version >= 3) {
reader_->ReadOffset(start);
return start + reader_->OffsetSize();
}
break;
case DW_FORM_ref_sig8:
return start + 8;
case DW_FORM_implicit_const:
return start;
case DW_FORM_block1: {
uint64_t datalen = reader_->ReadOneByte(start);
return start + 1 + datalen;
}
case DW_FORM_block2: {
uint64_t datalen = reader_->ReadTwoBytes(start);
return start + 2 + datalen;
}
case DW_FORM_block4: {
uint64_t datalen = reader_->ReadFourBytes(start);
return start + 4 + datalen;
}
case DW_FORM_block:
case DW_FORM_exprloc: {
uint64_t datalen = reader_->ReadUnsignedLEB128(start, &len);
return start + datalen + len;
}
case DW_FORM_strp: {
reader_->ReadOffset(start);
return start + reader_->OffsetSize();
}
case DW_FORM_line_strp: {
reader_->ReadOffset(start);
return start + reader_->OffsetSize();
}
case DW_FORM_strp_sup:
return start + 4;
case DW_FORM_ref_sup4:
return start + 4;
case DW_FORM_ref_sup8:
return start + 8;
case DW_FORM_loclistx:
reader_->ReadUnsignedLEB128(start, &len);
return start + len;
case DW_FORM_strx:
case DW_FORM_GNU_str_index: {
reader_->ReadUnsignedLEB128(start, &len);
return start + len;
}
case DW_FORM_strx1: {
return start + 1;
}
case DW_FORM_strx2: {
return start + 2;
}
case DW_FORM_strx3: {
return start + 3;
}
case DW_FORM_strx4: {
return start + 4;
}
case DW_FORM_addrx:
case DW_FORM_GNU_addr_index:
reader_->ReadUnsignedLEB128(start, &len);
return start + len;
case DW_FORM_addrx1:
return start + 1;
case DW_FORM_addrx2:
return start + 2;
case DW_FORM_addrx3:
return start + 3;
case DW_FORM_addrx4:
return start + 4;
case DW_FORM_rnglistx:
reader_->ReadUnsignedLEB128(start, &len);
return start + len;
}
fprintf(stderr, "Unhandled form type\n");
return NULL;
}
// If one really wanted, you could merge SkipAttribute and
// ProcessAttribute
// This is all boring data manipulation and calling of the handler.
const uint8_t* CompilationUnit::ProcessAttribute(
uint64_t dieoffset, const uint8_t* start, enum DwarfAttribute attr,
enum DwarfForm form, uint64_t implicit_const) {
size_t len;
switch (form) {
// DW_FORM_indirect is never used because it is such a space
// waster.
case DW_FORM_indirect:
form = static_cast<enum DwarfForm>(reader_->ReadUnsignedLEB128(start,
&len));
start += len;
return ProcessAttribute(dieoffset, start, attr, form, implicit_const);
case DW_FORM_flag_present:
ProcessAttributeUnsigned(dieoffset, attr, form, 1);
return start;
case DW_FORM_data1:
case DW_FORM_flag:
ProcessAttributeUnsigned(dieoffset, attr, form,
reader_->ReadOneByte(start));
return start + 1;
case DW_FORM_data2:
ProcessAttributeUnsigned(dieoffset, attr, form,
reader_->ReadTwoBytes(start));
return start + 2;
case DW_FORM_data4:
ProcessAttributeUnsigned(dieoffset, attr, form,
reader_->ReadFourBytes(start));
return start + 4;
case DW_FORM_data8:
ProcessAttributeUnsigned(dieoffset, attr, form,
reader_->ReadEightBytes(start));
return start + 8;
case DW_FORM_data16:
// This form is designed for an md5 checksum inside line tables.
fprintf(stderr, "Unhandled form type: DW_FORM_data16\n");
return start + 16;
case DW_FORM_string: {
const char* str = reinterpret_cast<const char*>(start);
ProcessAttributeString(dieoffset, attr, form, str);
return start + strlen(str) + 1;
}
case DW_FORM_udata:
ProcessAttributeUnsigned(dieoffset, attr, form,
reader_->ReadUnsignedLEB128(start, &len));
return start + len;
case DW_FORM_sdata:
ProcessAttributeSigned(dieoffset, attr, form,
reader_->ReadSignedLEB128(start, &len));
return start + len;
case DW_FORM_addr:
ProcessAttributeUnsigned(dieoffset, attr, form,
reader_->ReadAddress(start));
return start + reader_->AddressSize();
case DW_FORM_sec_offset:
ProcessAttributeUnsigned(dieoffset, attr, form,
reader_->ReadOffset(start));
return start + reader_->OffsetSize();
case DW_FORM_ref1:
handler_->ProcessAttributeReference(dieoffset, attr, form,
reader_->ReadOneByte(start)
+ offset_from_section_start_);
return start + 1;
case DW_FORM_ref2:
handler_->ProcessAttributeReference(dieoffset, attr, form,
reader_->ReadTwoBytes(start)
+ offset_from_section_start_);
return start + 2;
case DW_FORM_ref4:
handler_->ProcessAttributeReference(dieoffset, attr, form,
reader_->ReadFourBytes(start)
+ offset_from_section_start_);
return start + 4;
case DW_FORM_ref8:
handler_->ProcessAttributeReference(dieoffset, attr, form,
reader_->ReadEightBytes(start)
+ offset_from_section_start_);
return start + 8;
case DW_FORM_ref_udata:
handler_->ProcessAttributeReference(dieoffset, attr, form,
reader_->ReadUnsignedLEB128(start,
&len)
+ offset_from_section_start_);
return start + len;
case DW_FORM_ref_addr:
// DWARF2 and 3/4 differ on whether ref_addr is address size or
// offset size.
assert(header_.version >= 2);
if (header_.version == 2) {
handler_->ProcessAttributeReference(dieoffset, attr, form,
reader_->ReadAddress(start));
return start + reader_->AddressSize();
} else if (header_.version >= 3) {
handler_->ProcessAttributeReference(dieoffset, attr, form,
reader_->ReadOffset(start));
return start + reader_->OffsetSize();
}
break;
case DW_FORM_ref_sig8:
handler_->ProcessAttributeSignature(dieoffset, attr, form,
reader_->ReadEightBytes(start));
return start + 8;
case DW_FORM_implicit_const:
handler_->ProcessAttributeUnsigned(dieoffset, attr, form,
implicit_const);
return start;
case DW_FORM_block1: {
uint64_t datalen = reader_->ReadOneByte(start);
handler_->ProcessAttributeBuffer(dieoffset, attr, form, start + 1,
datalen);
return start + 1 + datalen;
}
case DW_FORM_block2: {
uint64_t datalen = reader_->ReadTwoBytes(start);
handler_->ProcessAttributeBuffer(dieoffset, attr, form, start + 2,
datalen);
return start + 2 + datalen;
}
case DW_FORM_block4: {
uint64_t datalen = reader_->ReadFourBytes(start);
handler_->ProcessAttributeBuffer(dieoffset, attr, form, start + 4,
datalen);
return start + 4 + datalen;
}
case DW_FORM_block:
case DW_FORM_exprloc: {
uint64_t datalen = reader_->ReadUnsignedLEB128(start, &len);
handler_->ProcessAttributeBuffer(dieoffset, attr, form, start + len,
datalen);
return start + datalen + len;
}
case DW_FORM_strp: {
assert(string_buffer_ != NULL);
const uint64_t offset = reader_->ReadOffset(start);
assert(string_buffer_ + offset < string_buffer_ + string_buffer_length_);
const char* str = reinterpret_cast<const char*>(string_buffer_ + offset);
ProcessAttributeString(dieoffset, attr, form, str);
return start + reader_->OffsetSize();
}
case DW_FORM_line_strp: {
assert(line_string_buffer_ != NULL);
const uint64_t offset = reader_->ReadOffset(start);
assert(line_string_buffer_ + offset <
line_string_buffer_ + line_string_buffer_length_);
const char* str =
reinterpret_cast<const char*>(line_string_buffer_ + offset);
ProcessAttributeString(dieoffset, attr, form, str);
return start + reader_->OffsetSize();
}
case DW_FORM_strp_sup:
// No support currently for suplementary object files.
fprintf(stderr, "Unhandled form type: DW_FORM_strp_sup\n");
return start + 4;
case DW_FORM_ref_sup4:
// No support currently for suplementary object files.
fprintf(stderr, "Unhandled form type: DW_FORM_ref_sup4\n");
return start + 4;
case DW_FORM_ref_sup8:
// No support currently for suplementary object files.
fprintf(stderr, "Unhandled form type: DW_FORM_ref_sup8\n");
return start + 8;
case DW_FORM_loclistx:
ProcessAttributeUnsigned(dieoffset, attr, form,
reader_->ReadUnsignedLEB128(start, &len));
return start + len;
case DW_FORM_strx:
case DW_FORM_GNU_str_index: {
uint64_t str_index = reader_->ReadUnsignedLEB128(start, &len);
ProcessFormStringIndex(dieoffset, attr, form, str_index);
return start + len;
}
case DW_FORM_strx1: {
uint64_t str_index = reader_->ReadOneByte(start);
ProcessFormStringIndex(dieoffset, attr, form, str_index);
return start + 1;
}
case DW_FORM_strx2: {
uint64_t str_index = reader_->ReadTwoBytes(start);
ProcessFormStringIndex(dieoffset, attr, form, str_index);
return start + 2;
}
case DW_FORM_strx3: {
uint64_t str_index = reader_->ReadThreeBytes(start);
ProcessFormStringIndex(dieoffset, attr, form, str_index);
return start + 3;
}
case DW_FORM_strx4: {
uint64_t str_index = reader_->ReadFourBytes(start);
ProcessFormStringIndex(dieoffset, attr, form, str_index);
return start + 4;
}
case DW_FORM_addrx:
case DW_FORM_GNU_addr_index:
ProcessAttributeAddrIndex(
dieoffset, attr, form, reader_->ReadUnsignedLEB128(start, &len));
return start + len;
case DW_FORM_addrx1:
ProcessAttributeAddrIndex(
dieoffset, attr, form, reader_->ReadOneByte(start));
return start + 1;
case DW_FORM_addrx2:
ProcessAttributeAddrIndex(
dieoffset, attr, form, reader_->ReadTwoBytes(start));
return start + 2;
case DW_FORM_addrx3:
ProcessAttributeAddrIndex(
dieoffset, attr, form, reader_->ReadThreeBytes(start));
return start + 3;
case DW_FORM_addrx4:
ProcessAttributeAddrIndex(
dieoffset, attr, form, reader_->ReadFourBytes(start));
return start + 4;
case DW_FORM_rnglistx:
ProcessAttributeUnsigned(
dieoffset, attr, form, reader_->ReadUnsignedLEB128(start, &len));
return start + len;
}
fprintf(stderr, "Unhandled form type\n");
return NULL;
}
const uint8_t* CompilationUnit::ProcessDIE(uint64_t dieoffset,
const uint8_t* start,
const Abbrev& abbrev) {
// With DWARF v5, the compile_unit die may contain a
// DW_AT_str_offsets_base or DW_AT_addr_base. If it does, that attribute must
// be found and processed before trying to process the other attributes;
// otherwise the string or address values will all come out incorrect.
if ((abbrev.tag == DW_TAG_compile_unit ||
abbrev.tag == DW_TAG_skeleton_unit) &&
header_.version == 5) {
uint64_t dieoffset_copy = dieoffset;
const uint8_t* start_copy = start;
for (AttributeList::const_iterator i = abbrev.attributes.begin();
i != abbrev.attributes.end();
i++) {
start_copy = ProcessOffsetBaseAttribute(dieoffset_copy, start_copy,
i->attr_, i->form_,
i->value_);
}
}
for (AttributeList::const_iterator i = abbrev.attributes.begin();
i != abbrev.attributes.end();
i++) {
start = ProcessAttribute(dieoffset, start, i->attr_, i->form_, i->value_);
}
// If this is a compilation unit in a split DWARF object, verify that
// the dwo_id matches. If it does not match, we will ignore this
// compilation unit.
if (abbrev.tag == DW_TAG_compile_unit
&& is_split_dwarf_
&& dwo_id_ != skeleton_dwo_id_) {
return NULL;
}
return start;
}
void CompilationUnit::ProcessDIEs() {
const uint8_t* dieptr = after_header_;
size_t len;
// lengthstart is the place the length field is based on.
// It is the point in the header after the initial length field
const uint8_t* lengthstart = buffer_;
// In 64 bit dwarf, the initial length is 12 bytes, because of the
// 0xffffffff at the start.
if (reader_->OffsetSize() == 8)
lengthstart += 12;
else
lengthstart += 4;
std::stack<uint64_t> die_stack;
while (dieptr < (lengthstart + header_.length)) {
// We give the user the absolute offset from the beginning of
// debug_info, since they need it to deal with ref_addr forms.
uint64_t absolute_offset = (dieptr - buffer_) + offset_from_section_start_;
uint64_t abbrev_num = reader_->ReadUnsignedLEB128(dieptr, &len);
dieptr += len;
// Abbrev == 0 represents the end of a list of children, or padding
// at the end of the compilation unit.
if (abbrev_num == 0) {
if (die_stack.size() == 0)
// If it is padding, then we are done with the compilation unit's DIEs.
return;
const uint64_t offset = die_stack.top();
die_stack.pop();
handler_->EndDIE(offset);
continue;
}
const Abbrev& abbrev = abbrevs_->at(static_cast<size_t>(abbrev_num));
const enum DwarfTag tag = abbrev.tag;
if (!handler_->StartDIE(absolute_offset, tag)) {
dieptr = SkipDIE(dieptr, abbrev);
if (!dieptr) {
fprintf(stderr,
"An error happens when skipping a DIE's attributes at offset "
"0x%" PRIx64
". Stopped processing following DIEs in this CU.\n",
absolute_offset);
exit(1);
}
} else {
dieptr = ProcessDIE(absolute_offset, dieptr, abbrev);
if (!dieptr) {
fprintf(stderr,
"An error happens when processing a DIE at offset 0x%" PRIx64
". Stopped processing following DIEs in this CU.\n",
absolute_offset);
exit(1);
}
}
if (abbrev.has_children) {
die_stack.push(absolute_offset);
} else {
handler_->EndDIE(absolute_offset);
}
}
}
// Check for a valid ELF file and return the Address size.
// Returns 0 if not a valid ELF file.
inline int GetElfWidth(const ElfReader& elf) {
if (elf.IsElf32File())
return 4;
if (elf.IsElf64File())
return 8;
return 0;
}
bool CompilationUnit::ProcessSplitDwarf(std::string& split_file,
SectionMap& sections,
ByteReader& split_byte_reader,
uint64_t& cu_offset) {
if (!should_process_split_dwarf_)
return false;
struct stat statbuf;
bool found_in_dwp = false;
if (!have_checked_for_dwp_) {
// Look for a .dwp file in the same directory as the executable.
have_checked_for_dwp_ = true;
string dwp_suffix(".dwp");
std::string dwp_path = path_ + dwp_suffix;
if (stat(dwp_path.c_str(), &statbuf) != 0) {
// Fall back to a split .debug file in the same directory.
string debug_suffix(".debug");
dwp_path = path_;
size_t found = path_.rfind(debug_suffix);
if (found != string::npos &&
found + debug_suffix.length() == path_.length())
dwp_path = dwp_path.replace(found, debug_suffix.length(), dwp_suffix);
}
if (stat(dwp_path.c_str(), &statbuf) == 0) {
split_elf_reader_ = std::make_unique<ElfReader>(dwp_path);
int width = GetElfWidth(*split_elf_reader_.get());
if (width != 0) {
split_byte_reader = ByteReader(reader_->GetEndianness());
split_byte_reader.SetAddressSize(width);
dwp_reader_ = std::make_unique<DwpReader>(split_byte_reader,
split_elf_reader_.get());
dwp_reader_->Initialize();
// If we have a .dwp file, read the debug sections for the requested CU.
dwp_reader_->ReadDebugSectionsForCU(dwo_id_, §ions);
if (!sections.empty()) {
SectionMap::const_iterator cu_iter =
GetSectionByName(sections, ".debug_info_offset");
SectionMap::const_iterator debug_info_iter =
GetSectionByName(sections, ".debug_info");
assert(cu_iter != sections.end());
assert(debug_info_iter != sections.end());
cu_offset = cu_iter->second.first - debug_info_iter->second.first;
found_in_dwp = true;
split_file = dwp_path;
}
}
}
}
if (!found_in_dwp) {
// If no .dwp file, try to open the .dwo file.
if (stat(dwo_name_, &statbuf) == 0) {
split_elf_reader_ = std::make_unique<ElfReader>(dwo_name_);
int width = GetElfWidth(*split_elf_reader_.get());
if (width != 0) {
split_byte_reader = ByteReader(ENDIANNESS_LITTLE);
split_byte_reader.SetAddressSize(width);
ReadDebugSectionsFromDwo(split_elf_reader_.get(), §ions);
if (!sections.empty()) {
split_file = dwo_name_;
}
}
}
}
return !split_file.empty();
}
void CompilationUnit::ReadDebugSectionsFromDwo(ElfReader* elf_reader,
SectionMap* sections) {
static const char* const section_names[] = {
".debug_abbrev",
".debug_info",
".debug_str_offsets",
".debug_str"
};
for (unsigned int i = 0u;
i < sizeof(section_names)/sizeof(*(section_names)); ++i) {
string base_name = section_names[i];
string dwo_name = base_name + ".dwo";
size_t section_size;
const char* section_data = elf_reader->GetSectionByName(dwo_name,
§ion_size);
if (section_data != NULL)
sections->insert(std::make_pair(
base_name, std::make_pair(
reinterpret_cast<const uint8_t*>(section_data),
section_size)));
}
}
DwpReader::DwpReader(const ByteReader& byte_reader, ElfReader* elf_reader)
: elf_reader_(elf_reader), byte_reader_(byte_reader),
cu_index_(NULL), cu_index_size_(0), string_buffer_(NULL),
string_buffer_size_(0), version_(0), ncolumns_(0), nunits_(0),
nslots_(0), phash_(NULL), pindex_(NULL), shndx_pool_(NULL),
offset_table_(NULL), size_table_(NULL), abbrev_data_(NULL),
abbrev_size_(0), info_data_(NULL), info_size_(0),
str_offsets_data_(NULL), str_offsets_size_(0) {}
void DwpReader::Initialize() {
cu_index_ = elf_reader_->GetSectionByName(".debug_cu_index",
&cu_index_size_);
if (cu_index_ == NULL) {
return;
}
// The .debug_str.dwo section is shared by all CUs in the file.
string_buffer_ = elf_reader_->GetSectionByName(".debug_str.dwo",
&string_buffer_size_);
version_ = byte_reader_.ReadFourBytes(
reinterpret_cast<const uint8_t*>(cu_index_));
if (version_ == 1) {
nslots_ = byte_reader_.ReadFourBytes(
reinterpret_cast<const uint8_t*>(cu_index_)
+ 3 * sizeof(uint32_t));
phash_ = cu_index_ + 4 * sizeof(uint32_t);
pindex_ = phash_ + nslots_ * sizeof(uint64_t);
shndx_pool_ = pindex_ + nslots_ * sizeof(uint32_t);
if (shndx_pool_ >= cu_index_ + cu_index_size_) {
version_ = 0;
}
} else if (version_ == 2 || version_ == 5) {
ncolumns_ = byte_reader_.ReadFourBytes(
reinterpret_cast<const uint8_t*>(cu_index_) + sizeof(uint32_t));
nunits_ = byte_reader_.ReadFourBytes(
reinterpret_cast<const uint8_t*>(cu_index_) + 2 * sizeof(uint32_t));
nslots_ = byte_reader_.ReadFourBytes(
reinterpret_cast<const uint8_t*>(cu_index_) + 3 * sizeof(uint32_t));
phash_ = cu_index_ + 4 * sizeof(uint32_t);
pindex_ = phash_ + nslots_ * sizeof(uint64_t);
offset_table_ = pindex_ + nslots_ * sizeof(uint32_t);
size_table_ = offset_table_ + ncolumns_ * (nunits_ + 1) * sizeof(uint32_t);
abbrev_data_ = elf_reader_->GetSectionByName(".debug_abbrev.dwo",
&abbrev_size_);
info_data_ = elf_reader_->GetSectionByName(".debug_info.dwo", &info_size_);
str_offsets_data_ = elf_reader_->GetSectionByName(".debug_str_offsets.dwo",
&str_offsets_size_);
rnglist_data_ =
elf_reader_->GetSectionByName(".debug_rnglists.dwo", &rnglist_size_);
if (size_table_ >= cu_index_ + cu_index_size_) {
version_ = 0;
}
}
}
void DwpReader::ReadDebugSectionsForCU(uint64_t dwo_id,
SectionMap* sections) {
if (version_ == 1) {
int slot = LookupCU(dwo_id);
if (slot == -1) {
return;
}
// The index table points to the section index pool, where we
// can read a list of section indexes for the debug sections
// for the CU whose dwo_id we are looking for.
int index = byte_reader_.ReadFourBytes(
reinterpret_cast<const uint8_t*>(pindex_)
+ slot * sizeof(uint32_t));
const char* shndx_list = shndx_pool_ + index * sizeof(uint32_t);
for (;;) {
if (shndx_list >= cu_index_ + cu_index_size_) {
version_ = 0;
return;
}
unsigned int shndx = byte_reader_.ReadFourBytes(
reinterpret_cast<const uint8_t*>(shndx_list));
shndx_list += sizeof(uint32_t);
if (shndx == 0)
break;
const char* section_name = elf_reader_->GetSectionName(shndx);
size_t section_size;
const char* section_data;
// We're only interested in these four debug sections.
// The section names in the .dwo file end with ".dwo", but we
// add them to the sections table with their normal names.
if (!strncmp(section_name, ".debug_abbrev", strlen(".debug_abbrev"))) {
section_data = elf_reader_->GetSectionByIndex(shndx, §ion_size);
sections->insert(std::make_pair(
".debug_abbrev",
std::make_pair(reinterpret_cast<const uint8_t*> (section_data),
section_size)));
} else if (!strncmp(section_name, ".debug_info", strlen(".debug_info"))) {
section_data = elf_reader_->GetSectionByIndex(shndx, §ion_size);
sections->insert(std::make_pair(
".debug_info",
std::make_pair(reinterpret_cast<const uint8_t*> (section_data),
section_size)));
} else if (!strncmp(section_name, ".debug_str_offsets",
strlen(".debug_str_offsets"))) {
section_data = elf_reader_->GetSectionByIndex(shndx, §ion_size);
sections->insert(std::make_pair(
".debug_str_offsets",
std::make_pair(reinterpret_cast<const uint8_t*> (section_data),
section_size)));
}
}
sections->insert(std::make_pair(
".debug_str",
std::make_pair(reinterpret_cast<const uint8_t*> (string_buffer_),
string_buffer_size_)));
} else if (version_ == 2 || version_ == 5) {
uint32_t index = LookupCUv2(dwo_id);
if (index == 0) {
return;
}
// The index points to a row in each of the section offsets table
// and the section size table, where we can read the offsets and sizes
// of the contributions to each debug section from the CU whose dwo_id
// we are looking for. Row 0 of the section offsets table has the
// section ids for each column of the table. The size table begins
// with row 1.
const char* id_row = offset_table_;
const char* offset_row = offset_table_
+ index * ncolumns_ * sizeof(uint32_t);
const char* size_row =
size_table_ + (index - 1) * ncolumns_ * sizeof(uint32_t);
if (size_row + ncolumns_ * sizeof(uint32_t) > cu_index_ + cu_index_size_) {
version_ = 0;
return;
}
for (unsigned int col = 0u; col < ncolumns_; ++col) {
uint32_t section_id =
byte_reader_.ReadFourBytes(reinterpret_cast<const uint8_t*>(id_row)
+ col * sizeof(uint32_t));
uint32_t offset = byte_reader_.ReadFourBytes(
reinterpret_cast<const uint8_t*>(offset_row)
+ col * sizeof(uint32_t));
uint32_t size = byte_reader_.ReadFourBytes(
reinterpret_cast<const uint8_t*>(size_row) + col * sizeof(uint32_t));
if (section_id == DW_SECT_ABBREV) {
sections->insert(std::make_pair(
".debug_abbrev",
std::make_pair(reinterpret_cast<const uint8_t*> (abbrev_data_)
+ offset, size)));
} else if (section_id == DW_SECT_INFO) {
sections->insert(std::make_pair(
".debug_info",
std::make_pair(reinterpret_cast<const uint8_t*>(info_data_), 0)));
// .debug_info_offset will points the buffer for the CU with given
// dwo_id.
sections->insert(std::make_pair(
".debug_info_offset",
std::make_pair(
reinterpret_cast<const uint8_t*>(info_data_) + offset, size)));
} else if (section_id == DW_SECT_STR_OFFSETS) {
sections->insert(std::make_pair(
".debug_str_offsets",
std::make_pair(reinterpret_cast<const uint8_t*> (str_offsets_data_)
+ offset, size)));
} else if (section_id == DW_SECT_RNGLISTS) {
sections->insert(std::make_pair(
".debug_rnglists",
std::make_pair(
reinterpret_cast<const uint8_t*>(rnglist_data_) + offset,
size)));
}
}
sections->insert(std::make_pair(
".debug_str",
std::make_pair(reinterpret_cast<const uint8_t*> (string_buffer_),
string_buffer_size_)));
}
}
int DwpReader::LookupCU(uint64_t dwo_id) {
uint32_t slot = static_cast<uint32_t>(dwo_id) & (nslots_ - 1);
uint64_t probe = byte_reader_.ReadEightBytes(
reinterpret_cast<const uint8_t*>(phash_) + slot * sizeof(uint64_t));
if (probe != 0 && probe != dwo_id) {
uint32_t secondary_hash =
(static_cast<uint32_t>(dwo_id >> 32) & (nslots_ - 1)) | 1;
do {
slot = (slot + secondary_hash) & (nslots_ - 1);
probe = byte_reader_.ReadEightBytes(
reinterpret_cast<const uint8_t*>(phash_) + slot * sizeof(uint64_t));
} while (probe != 0 && probe != dwo_id);
}
if (probe == 0)
return -1;
return slot;
}
uint32_t DwpReader::LookupCUv2(uint64_t dwo_id) {
uint32_t slot = static_cast<uint32_t>(dwo_id) & (nslots_ - 1);
uint64_t probe = byte_reader_.ReadEightBytes(
reinterpret_cast<const uint8_t*>(phash_) + slot * sizeof(uint64_t));
uint32_t index = byte_reader_.ReadFourBytes(
reinterpret_cast<const uint8_t*>(pindex_) + slot * sizeof(uint32_t));
if (index != 0 && probe != dwo_id) {
uint32_t secondary_hash =
(static_cast<uint32_t>(dwo_id >> 32) & (nslots_ - 1)) | 1;
do {
slot = (slot + secondary_hash) & (nslots_ - 1);
probe = byte_reader_.ReadEightBytes(
reinterpret_cast<const uint8_t*>(phash_) + slot * sizeof(uint64_t));
index = byte_reader_.ReadFourBytes(
reinterpret_cast<const uint8_t*>(pindex_) + slot * sizeof(uint32_t));
} while (index != 0 && probe != dwo_id);
}
return index;
}
LineInfo::LineInfo(const uint8_t* buffer, uint64_t buffer_length,
ByteReader* reader, const uint8_t* string_buffer,
size_t string_buffer_length,
const uint8_t* line_string_buffer,
size_t line_string_buffer_length, LineInfoHandler* handler):
handler_(handler), reader_(reader), buffer_(buffer),
string_buffer_(string_buffer),
line_string_buffer_(line_string_buffer) {
#ifndef NDEBUG
buffer_length_ = buffer_length;
string_buffer_length_ = string_buffer_length;
line_string_buffer_length_ = line_string_buffer_length;
#endif
header_.std_opcode_lengths = NULL;
}
uint64_t LineInfo::Start() {
ReadHeader();
ReadLines();
return after_header_ - buffer_;
}
void LineInfo::ReadTypesAndForms(const uint8_t** lineptr,
uint32_t* content_types,
uint32_t* content_forms,
uint32_t max_types,
uint32_t* format_count) {
size_t len;
uint32_t count = reader_->ReadUnsignedLEB128(*lineptr, &len);
*lineptr += len;
if (count < 1 || count > max_types) {
return;
}
for (uint32_t col = 0; col < count; ++col) {
content_types[col] = reader_->ReadUnsignedLEB128(*lineptr, &len);
*lineptr += len;
content_forms[col] = reader_->ReadUnsignedLEB128(*lineptr, &len);
*lineptr += len;
}
*format_count = count;
}
const char* LineInfo::ReadStringForm(uint32_t form, const uint8_t** lineptr) {
const char* name = nullptr;
if (form == DW_FORM_string) {
name = reinterpret_cast<const char*>(*lineptr);
*lineptr += strlen(name) + 1;
return name;
} else if (form == DW_FORM_strp) {
uint64_t offset = reader_->ReadOffset(*lineptr);
assert(offset < string_buffer_length_);
*lineptr += reader_->OffsetSize();
if (string_buffer_ != nullptr) {
name = reinterpret_cast<const char*>(string_buffer_) + offset;
return name;
}
} else if (form == DW_FORM_line_strp) {
uint64_t offset = reader_->ReadOffset(*lineptr);
assert(offset < line_string_buffer_length_);
*lineptr += reader_->OffsetSize();
if (line_string_buffer_ != nullptr) {
name = reinterpret_cast<const char*>(line_string_buffer_) + offset;
return name;
}
}
// Shouldn't be called with a non-string-form, and
// if there is a string form but no string buffer,
// that is a problem too.
assert(0);
return nullptr;
}
uint64_t LineInfo::ReadUnsignedData(uint32_t form, const uint8_t** lineptr) {
size_t len;
uint64_t value;
switch (form) {
case DW_FORM_data1:
value = reader_->ReadOneByte(*lineptr);
*lineptr += 1;
return value;
case DW_FORM_data2:
value = reader_->ReadTwoBytes(*lineptr);
*lineptr += 2;
return value;
case DW_FORM_data4:
value = reader_->ReadFourBytes(*lineptr);
*lineptr += 4;
return value;
case DW_FORM_data8:
value = reader_->ReadEightBytes(*lineptr);
*lineptr += 8;
return value;
case DW_FORM_udata:
value = reader_->ReadUnsignedLEB128(*lineptr, &len);
*lineptr += len;
return value;
default:
fprintf(stderr, "Unrecognized data form.");
return 0;
}
}
void LineInfo::ReadFileRow(const uint8_t** lineptr,
const uint32_t* content_types,
const uint32_t* content_forms, uint32_t row,
uint32_t format_count) {
const char* filename = nullptr;
uint64_t dirindex = 0;
uint64_t mod_time = 0;
uint64_t filelength = 0;
for (uint32_t col = 0; col < format_count; ++col) {
switch (content_types[col]) {
case DW_LNCT_path:
filename = ReadStringForm(content_forms[col], lineptr);
break;
case DW_LNCT_directory_index:
dirindex = ReadUnsignedData(content_forms[col], lineptr);
break;
case DW_LNCT_timestamp:
mod_time = ReadUnsignedData(content_forms[col], lineptr);
break;
case DW_LNCT_size:
filelength = ReadUnsignedData(content_forms[col], lineptr);
break;
case DW_LNCT_MD5:
// MD5 entries help a debugger sort different versions of files with
// the same name. It is always paired with a DW_FORM_data16 and is
// unused in this case.
*lineptr += 16;
break;
default:
fprintf(stderr, "Unrecognized form in line table header. %d\n",
content_types[col]);
assert(false);
break;
}
}
assert(filename != nullptr);
handler_->DefineFile(filename, row, dirindex, mod_time, filelength);
}
// The header for a debug_line section is mildly complicated, because
// the line info is very tightly encoded.
void LineInfo::ReadHeader() {
const uint8_t* lineptr = buffer_;
size_t initial_length_size;
const uint64_t initial_length
= reader_->ReadInitialLength(lineptr, &initial_length_size);
lineptr += initial_length_size;
header_.total_length = initial_length;
assert(buffer_ + initial_length_size + header_.total_length <=
buffer_ + buffer_length_);
header_.version = reader_->ReadTwoBytes(lineptr);
lineptr += 2;
if (header_.version >= 5) {
uint8_t address_size = reader_->ReadOneByte(lineptr);
reader_->SetAddressSize(address_size);
lineptr += 1;
uint8_t segment_selector_size = reader_->ReadOneByte(lineptr);
if (segment_selector_size != 0) {
fprintf(stderr,"No support for segmented memory.");
}
lineptr += 1;
} else {
// Address size *must* be set by CU ahead of time.
assert(reader_->AddressSize() != 0);
}
header_.prologue_length = reader_->ReadOffset(lineptr);
lineptr += reader_->OffsetSize();
header_.min_insn_length = reader_->ReadOneByte(lineptr);
lineptr += 1;
if (header_.version >= 4) {
__attribute__((unused)) uint8_t max_ops_per_insn =
reader_->ReadOneByte(lineptr);
++lineptr;
assert(max_ops_per_insn == 1);
}
header_.default_is_stmt = reader_->ReadOneByte(lineptr);
lineptr += 1;
header_.line_base = *reinterpret_cast<const int8_t*>(lineptr);
lineptr += 1;
header_.line_range = reader_->ReadOneByte(lineptr);
lineptr += 1;
header_.opcode_base = reader_->ReadOneByte(lineptr);
lineptr += 1;
header_.std_opcode_lengths = new std::vector<unsigned char>;
header_.std_opcode_lengths->resize(header_.opcode_base + 1);
(*header_.std_opcode_lengths)[0] = 0;
for (int i = 1; i < header_.opcode_base; i++) {
(*header_.std_opcode_lengths)[i] = reader_->ReadOneByte(lineptr);
lineptr += 1;
}
if (header_.version <= 4) {
// Directory zero is assumed to be the compilation directory and special
// cased where used. It is not actually stored in the dwarf data. But an
// empty entry here avoids off-by-one errors elsewhere in the code.
handler_->DefineDir("", 0);
// It is legal for the directory entry table to be empty.
if (*lineptr) {
uint32_t dirindex = 1;
while (*lineptr) {
const char* dirname = reinterpret_cast<const char*>(lineptr);
handler_->DefineDir(dirname, dirindex);
lineptr += strlen(dirname) + 1;
dirindex++;
}
}
lineptr++;
// It is also legal for the file entry table to be empty.
// Similarly for file zero.
handler_->DefineFile("", 0, 0, 0, 0);
if (*lineptr) {
uint32_t fileindex = 1;
size_t len;
while (*lineptr) {
const char* filename = ReadStringForm(DW_FORM_string, &lineptr);
uint64_t dirindex = reader_->ReadUnsignedLEB128(lineptr, &len);
lineptr += len;
uint64_t mod_time = reader_->ReadUnsignedLEB128(lineptr, &len);
lineptr += len;
uint64_t filelength = reader_->ReadUnsignedLEB128(lineptr, &len);
lineptr += len;
handler_->DefineFile(filename, fileindex,
static_cast<uint32_t>(dirindex), mod_time,
filelength);
fileindex++;
}
}
lineptr++;
} else {
// Read the DWARF-5 directory table.
// Dwarf5 supports five different types and forms per directory- and
// file-table entry. Theoretically, there could be duplicate entries
// in this table, but that would be quite unusual.
static const uint32_t kMaxTypesAndForms = 5;
uint32_t content_types[kMaxTypesAndForms];
uint32_t content_forms[kMaxTypesAndForms];
uint32_t format_count;
size_t len;
ReadTypesAndForms(&lineptr, content_types, content_forms, kMaxTypesAndForms,
&format_count);
uint32_t entry_count = reader_->ReadUnsignedLEB128(lineptr, &len);
lineptr += len;
for (uint32_t row = 0; row < entry_count; ++row) {
const char* dirname = nullptr;
for (uint32_t col = 0; col < format_count; ++col) {
// The path is the only relevant content type for this implementation.
if (content_types[col] == DW_LNCT_path) {
dirname = ReadStringForm(content_forms[col], &lineptr);
}
}
handler_->DefineDir(dirname, row);
}
// Read the DWARF-5 filename table.
ReadTypesAndForms(&lineptr, content_types, content_forms, kMaxTypesAndForms,
&format_count);
entry_count = reader_->ReadUnsignedLEB128(lineptr, &len);
lineptr += len;
for (uint32_t row = 0; row < entry_count; ++row) {
ReadFileRow(&lineptr, content_types, content_forms, row, format_count);
}
}
after_header_ = lineptr;
}
/* static */
bool LineInfo::ProcessOneOpcode(ByteReader* reader,
LineInfoHandler* handler,
const struct LineInfoHeader& header,
const uint8_t* start,
struct LineStateMachine* lsm,
size_t* len,
uintptr pc,
bool* lsm_passes_pc) {
size_t oplen = 0;
size_t templen;
uint8_t opcode = reader->ReadOneByte(start);
oplen++;
start++;
// If the opcode is great than the opcode_base, it is a special
// opcode. Most line programs consist mainly of special opcodes.
if (opcode >= header.opcode_base) {
opcode -= header.opcode_base;
const int64_t advance_address = (opcode / header.line_range)
* header.min_insn_length;
const int32_t advance_line = (opcode % header.line_range)
+ header.line_base;
// Check if the lsm passes "pc". If so, mark it as passed.
if (lsm_passes_pc &&
lsm->address <= pc && pc < lsm->address + advance_address) {
*lsm_passes_pc = true;
}
lsm->address += advance_address;
lsm->line_num += advance_line;
lsm->basic_block = true;
*len = oplen;
return true;
}
// Otherwise, we have the regular opcodes
switch (opcode) {
case DW_LNS_copy: {
lsm->basic_block = false;
*len = oplen;
return true;
}
case DW_LNS_advance_pc: {
uint64_t advance_address = reader->ReadUnsignedLEB128(start, &templen);
oplen += templen;
// Check if the lsm passes "pc". If so, mark it as passed.
if (lsm_passes_pc && lsm->address <= pc &&
pc < lsm->address + header.min_insn_length * advance_address) {
*lsm_passes_pc = true;
}
lsm->address += header.min_insn_length * advance_address;
}
break;
case DW_LNS_advance_line: {
const int64_t advance_line = reader->ReadSignedLEB128(start, &templen);
oplen += templen;
lsm->line_num += static_cast<int32_t>(advance_line);
// With gcc 4.2.1, we can get the line_no here for the first time
// since DW_LNS_advance_line is called after DW_LNE_set_address is
// called. So we check if the lsm passes "pc" here, not in
// DW_LNE_set_address.
if (lsm_passes_pc && lsm->address == pc) {
*lsm_passes_pc = true;
}
}
break;
case DW_LNS_set_file: {
const uint64_t fileno = reader->ReadUnsignedLEB128(start, &templen);
oplen += templen;
lsm->file_num = static_cast<uint32_t>(fileno);
}
break;
case DW_LNS_set_column: {
const uint64_t colno = reader->ReadUnsignedLEB128(start, &templen);
oplen += templen;
lsm->column_num = static_cast<uint32_t>(colno);
}
break;
case DW_LNS_negate_stmt: {
lsm->is_stmt = !lsm->is_stmt;
}
break;
case DW_LNS_set_basic_block: {
lsm->basic_block = true;
}
break;
case DW_LNS_fixed_advance_pc: {
const uint16_t advance_address = reader->ReadTwoBytes(start);
oplen += 2;
// Check if the lsm passes "pc". If so, mark it as passed.
if (lsm_passes_pc &&
lsm->address <= pc && pc < lsm->address + advance_address) {
*lsm_passes_pc = true;
}
lsm->address += advance_address;
}
break;
case DW_LNS_const_add_pc: {
const int64_t advance_address = header.min_insn_length
* ((255 - header.opcode_base)
/ header.line_range);
// Check if the lsm passes "pc". If so, mark it as passed.
if (lsm_passes_pc &&
lsm->address <= pc && pc < lsm->address + advance_address) {
*lsm_passes_pc = true;
}
lsm->address += advance_address;
}
break;
case DW_LNS_extended_op: {
const uint64_t extended_op_len = reader->ReadUnsignedLEB128(start,
&templen);
start += templen;
oplen += templen + extended_op_len;
const uint64_t extended_op = reader->ReadOneByte(start);
start++;
switch (extended_op) {
case DW_LNE_end_sequence: {
lsm->end_sequence = true;
*len = oplen;
return true;
}
break;
case DW_LNE_set_address: {
// With gcc 4.2.1, we cannot tell the line_no here since
// DW_LNE_set_address is called before DW_LNS_advance_line is
// called. So we do not check if the lsm passes "pc" here. See
// also the comment in DW_LNS_advance_line.
uint64_t address = reader->ReadAddress(start);
lsm->address = address;
}
break;
case DW_LNE_define_file: {
const char* filename = reinterpret_cast<const char*>(start);
templen = strlen(filename) + 1;
start += templen;
uint64_t dirindex = reader->ReadUnsignedLEB128(start, &templen);
oplen += templen;
const uint64_t mod_time = reader->ReadUnsignedLEB128(start,
&templen);
oplen += templen;
const uint64_t filelength = reader->ReadUnsignedLEB128(start,
&templen);
oplen += templen;
if (handler) {
handler->DefineFile(filename, -1, static_cast<uint32_t>(dirindex),
mod_time, filelength);
}
}
break;
}
}
break;
default: {
// Ignore unknown opcode silently
if (header.std_opcode_lengths) {
for (int i = 0; i < (*header.std_opcode_lengths)[opcode]; i++) {
reader->ReadUnsignedLEB128(start, &templen);
start += templen;
oplen += templen;
}
}
}
break;
}
*len = oplen;
return false;
}
void LineInfo::ReadLines() {
struct LineStateMachine lsm;
// lengthstart is the place the length field is based on.
// It is the point in the header after the initial length field
const uint8_t* lengthstart = buffer_;
// In 64 bit dwarf, the initial length is 12 bytes, because of the
// 0xffffffff at the start.
if (reader_->OffsetSize() == 8)
lengthstart += 12;
else
lengthstart += 4;
const uint8_t* lineptr = after_header_;
lsm.Reset(header_.default_is_stmt);
// The LineInfoHandler interface expects each line's length along
// with its address, but DWARF only provides addresses (sans
// length), and an end-of-sequence address; one infers the length
// from the next address. So we report a line only when we get the
// next line's address, or the end-of-sequence address.
bool have_pending_line = false;
uint64_t pending_address = 0;
uint32_t pending_file_num = 0, pending_line_num = 0, pending_column_num = 0;
while (lineptr < lengthstart + header_.total_length) {
size_t oplength;
bool add_row = ProcessOneOpcode(reader_, handler_, header_,
lineptr, &lsm, &oplength, (uintptr)-1,
NULL);
if (add_row) {
if (have_pending_line)
handler_->AddLine(pending_address, lsm.address - pending_address,
pending_file_num, pending_line_num,
pending_column_num);
if (lsm.end_sequence) {
lsm.Reset(header_.default_is_stmt);
have_pending_line = false;
} else {
pending_address = lsm.address;
pending_file_num = lsm.file_num;
pending_line_num = lsm.line_num;
pending_column_num = lsm.column_num;
have_pending_line = true;
}
}
lineptr += oplength;
}
after_header_ = lengthstart + header_.total_length;
}
bool RangeListReader::ReadRanges(enum DwarfForm form, uint64_t data) {
if (form == DW_FORM_sec_offset) {
if (cu_info_->version_ <= 4) {
return ReadDebugRanges(data);
} else {
return ReadDebugRngList(data);
}
} else if (form == DW_FORM_rnglistx) {
if (cu_info_->ranges_base_ == 0) {
// In split dwarf, there's no DW_AT_rnglists_base attribute, range_base
// will just be the first byte after the header.
cu_info_->ranges_base_ = reader_->OffsetSize() == 4? 12: 20;
}
offset_array_ = cu_info_->ranges_base_;
uint64_t index_offset = reader_->OffsetSize() * data;
uint64_t range_list_offset =
reader_->ReadOffset(cu_info_->buffer_ + offset_array_ + index_offset);
return ReadDebugRngList(offset_array_ + range_list_offset);
}
return false;
}
bool RangeListReader::ReadDebugRanges(uint64_t offset) {
const uint64_t max_address =
(reader_->AddressSize() == 4) ? 0xffffffffUL
: 0xffffffffffffffffULL;
const uint64_t entry_size = reader_->AddressSize() * 2;
bool list_end = false;
do {
if (offset > cu_info_->size_ - entry_size) {
return false; // Invalid range detected
}
uint64_t start_address = reader_->ReadAddress(cu_info_->buffer_ + offset);
uint64_t end_address = reader_->ReadAddress(
cu_info_->buffer_ + offset + reader_->AddressSize());
if (start_address == max_address) { // Base address selection
cu_info_->base_address_ = end_address;
} else if (start_address == 0 && end_address == 0) { // End-of-list
handler_->Finish();
list_end = true;
} else { // Add a range entry
handler_->AddRange(start_address + cu_info_->base_address_,
end_address + cu_info_->base_address_);
}
offset += entry_size;
} while (!list_end);
return true;
}
bool RangeListReader::ReadDebugRngList(uint64_t offset) {
uint64_t start = 0;
uint64_t end = 0;
uint64_t range_len = 0;
uint64_t index = 0;
// A uleb128's length isn't known until after it has been read, so overruns
// are only caught after an entire entry.
while (offset < cu_info_->size_) {
uint8_t entry_type = reader_->ReadOneByte(cu_info_->buffer_ + offset);
offset += 1;
// Handle each entry type per Dwarf 5 Standard, section 2.17.3.
switch (entry_type) {
case DW_RLE_end_of_list:
handler_->Finish();
return true;
case DW_RLE_base_addressx:
offset += ReadULEB(offset, &index);
cu_info_->base_address_ = GetAddressAtIndex(index);
break;
case DW_RLE_startx_endx:
offset += ReadULEB(offset, &index);
start = GetAddressAtIndex(index);
offset += ReadULEB(offset, &index);
end = GetAddressAtIndex(index);
handler_->AddRange(start, end);
break;
case DW_RLE_startx_length:
offset += ReadULEB(offset, &index);
start = GetAddressAtIndex(index);
offset += ReadULEB(offset, &range_len);
handler_->AddRange(start, start + range_len);
break;
case DW_RLE_offset_pair:
offset += ReadULEB(offset, &start);
offset += ReadULEB(offset, &end);
handler_->AddRange(start + cu_info_->base_address_,
end + cu_info_->base_address_);
break;
case DW_RLE_base_address:
offset += ReadAddress(offset, &cu_info_->base_address_);
break;
case DW_RLE_start_end:
offset += ReadAddress(offset, &start);
offset += ReadAddress(offset, &end);
handler_->AddRange(start, end);
break;
case DW_RLE_start_length:
offset += ReadAddress(offset, &start);
offset += ReadULEB(offset, &end);
handler_->AddRange(start, start + end);
break;
}
}
return false;
}
// 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_t 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) { }
};
// Rule: the value the register had in the caller cannot be recovered.
class CallFrameInfo::UndefinedRule: public CallFrameInfo::Rule {
public:
UndefinedRule() { }
~UndefinedRule() { }
bool Handle(Handler* handler, uint64_t address, int reg) const {
return handler->UndefinedRule(address, reg);
}
bool operator==(const Rule& rhs) const {
// dynamic_cast is allowed by the Google C++ Style Guide, if the use has
// been carefully considered; cheap RTTI-like workarounds are forbidden.
const UndefinedRule* our_rhs = dynamic_cast<const UndefinedRule*>(&rhs);
return (our_rhs != NULL);
}
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() { }
bool Handle(Handler* handler, uint64_t address, int reg) const {
return handler->SameValueRule(address, reg);
}
bool operator==(const Rule& rhs) const {
// dynamic_cast is allowed by the Google C++ Style Guide, if the use has
// been carefully considered; cheap RTTI-like workarounds are forbidden.
const SameValueRule* our_rhs = dynamic_cast<const SameValueRule*>(&rhs);
return (our_rhs != NULL);
}
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() { }
bool Handle(Handler* handler, uint64_t address, int reg) const {
return handler->OffsetRule(address, reg, base_register_, offset_);
}
bool operator==(const Rule& rhs) const {
// dynamic_cast is allowed by the Google C++ Style Guide, if the use has
// been carefully considered; cheap RTTI-like workarounds are forbidden.
const OffsetRule* our_rhs = dynamic_cast<const OffsetRule*>(&rhs);
return (our_rhs &&
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() { }
bool Handle(Handler* handler, uint64_t address, int reg) const {
return handler->ValOffsetRule(address, reg, base_register_, offset_);
}
bool operator==(const Rule& rhs) const {
// dynamic_cast is allowed by the Google C++ Style Guide, if the use has
// been carefully considered; cheap RTTI-like workarounds are forbidden.
const ValOffsetRule* our_rhs = dynamic_cast<const ValOffsetRule*>(&rhs);
return (our_rhs &&
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() { }
bool Handle(Handler* handler, uint64_t address, int reg) const {
return handler->RegisterRule(address, reg, register_number_);
}
bool operator==(const Rule& rhs) const {
// dynamic_cast is allowed by the Google C++ Style Guide, if the use has
// been carefully considered; cheap RTTI-like workarounds are forbidden.
const RegisterRule* our_rhs = dynamic_cast<const RegisterRule*>(&rhs);
return (our_rhs && 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() { }
bool Handle(Handler* handler, uint64_t address, int reg) const {
return handler->ExpressionRule(address, reg, expression_);
}
bool operator==(const Rule& rhs) const {
// dynamic_cast is allowed by the Google C++ Style Guide, if the use has
// been carefully considered; cheap RTTI-like workarounds are forbidden.
const ExpressionRule* our_rhs = dynamic_cast<const ExpressionRule*>(&rhs);
return (our_rhs && expression_ == our_rhs->expression_);
}
Rule* Copy() const { return new ExpressionRule(*this); }
private:
string expression_;
};
// Rule: EXPRESSION evaluates to the address at which the register is saved.
class CallFrameInfo::ValExpressionRule: public CallFrameInfo::Rule {
public:
explicit ValExpressionRule(const string& expression)
: expression_(expression) { }
~ValExpressionRule() { }
bool Handle(Handler* handler, uint64_t address, int reg) const {
return handler->ValExpressionRule(address, reg, expression_);
}
bool operator==(const Rule& rhs) const {
// dynamic_cast is allowed by the Google C++ Style Guide, if the use has
// been carefully considered; cheap RTTI-like workarounds are forbidden.
const ValExpressionRule* our_rhs =
dynamic_cast<const ValExpressionRule*>(&rhs);
return (our_rhs && 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_t 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 {
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) {
assert(reg != Handler::kCFARegister);
assert(rule);
Rule** slot = ®isters_[reg];
delete *slot;
*slot = rule;
}
bool CallFrameInfo::RuleMap::HandleTransitionTo(
Handler* handler,
uint64_t 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.
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.
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.
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_t address)
: reader_(reader), handler_(handler), reporter_(reporter),
address_(address), entry_(NULL), cursor_(NULL) { }
// 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_t 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_t 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_t 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 uint8_t* 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(reinterpret_cast<const char*>(cursor_),
expression_length);
cursor_ += expression_length;
break;
}
default:
assert(0);
}
}
return true;
}
bool CallFrameInfo::State::DoInstruction() {
CIE* cie = entry_->cie;
Operands ops;
// Our entry's kind should have been set by now.
assert(entry_->kind != kUnknown);
// We shouldn't have been invoked unless there were more
// instructions to parse.
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:
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: {
if (!ParseOperands("r", &ops)) return false;
Rule* cfa_rule = rules_.CFARule();
if (!cfa_rule) {
if (!DoDefCFA(ops.register_number, ops.offset)) {
reporter_->NoCFARule(entry_->offset, entry_->kind, CursorOffset());
return false;
}
} else {
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:
saved_rules_.push(rules_);
break;
// Pop the current set of rules off the stack.
case DW_CFA_restore_state: {
if (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;
// case DW_CFA_AARCH64_negate_ra_state
case DW_CFA_GNU_window_save: {
if (handler_->Architecture() == "arm64") {
// Indicates that the return address, x30 has been signed.
// Breakpad will speculatively remove pointer-authentication codes when
// interpreting return addresses, regardless of this bit.
} else if (handler_->Architecture() == "sparc" ||
handler_->Architecture() == "sparcv9") {
// 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.
// 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 uint8_t* cursor, Entry* entry) {
const uint8_t* 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_t 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 {
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 uint8_t* cursor = cie->fields;
size_t len;
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 uint8_t* augmentation_start = cursor;
const uint8_t* augmentation_end =
reinterpret_cast<const uint8_t*>(memchr(augmentation_start, '\0',
cie->end - augmentation_start));
if (! augmentation_end) return ReportIncomplete(cie);
cursor = augmentation_end;
cie->augmentation = string(reinterpret_cast<const char*>(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) {
cie->address_size = *cursor++;
if (cie->address_size != 8 && cie->address_size != 4) {
reporter_->UnexpectedAddressSize(cie->offset, cie->address_size);
return false;
}
cie->segment_size = *cursor++;
if (cie->segment_size != 0) {
reporter_->UnexpectedSegmentSize(cie->offset, cie->segment_size);
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_t(*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 uint8_t* data = cursor;
cursor += data_size;
const uint8_t* 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 uint8_t* 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 uint8_t* buffer_end = buffer_ + buffer_length_;
const uint8_t* cursor;
bool all_ok = true;
const uint8_t* 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;
// TODO(nbilling): This could lead to strange behavior if a single buffer
// contained a mixture of DWARF versions as well as address sizes. Not
// sure if it's worth handling such a case.
// DWARF4 CIE specifies address_size, so use it for this call frame.
if (cie.version >= 4) {
reader_->SetAddressSize(cie.address_size);
}
// 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 {
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_t offset,
CallFrameInfo::EntryKind kind) {
fprintf(stderr,
"%s: CFI %s at offset 0x%" PRIx64 " in '%s': entry ends early\n",
filename_.c_str(), CallFrameInfo::KindName(kind), offset,
section_.c_str());
}
void CallFrameInfo::Reporter::EarlyEHTerminator(uint64_t offset) {
fprintf(stderr,
"%s: CFI at offset 0x%" PRIx64 " in '%s': saw end-of-data marker"
" before end of section contents\n",
filename_.c_str(), offset, section_.c_str());
}
void CallFrameInfo::Reporter::CIEPointerOutOfRange(uint64_t offset,
uint64_t cie_offset) {
fprintf(stderr,
"%s: CFI frame description entry at offset 0x%" PRIx64 " in '%s':"
" CIE pointer is out of range: 0x%" PRIx64 "\n",
filename_.c_str(), offset, section_.c_str(), cie_offset);
}
void CallFrameInfo::Reporter::BadCIEId(uint64_t offset, uint64_t cie_offset) {
fprintf(stderr,
"%s: CFI frame description entry at offset 0x%" PRIx64 " in '%s':"
" CIE pointer does not point to a CIE: 0x%" PRIx64 "\n",
filename_.c_str(), offset, section_.c_str(), cie_offset);
}
void CallFrameInfo::Reporter::UnexpectedAddressSize(uint64_t offset,
uint8_t address_size) {
fprintf(stderr,
"%s: CFI frame description entry at offset 0x%" PRIx64 " in '%s':"
" CIE specifies unexpected address size: %d\n",
filename_.c_str(), offset, section_.c_str(), address_size);
}
void CallFrameInfo::Reporter::UnexpectedSegmentSize(uint64_t offset,
uint8_t segment_size) {
fprintf(stderr,
"%s: CFI frame description entry at offset 0x%" PRIx64 " in '%s':"
" CIE specifies unexpected segment size: %d\n",
filename_.c_str(), offset, section_.c_str(), segment_size);
}
void CallFrameInfo::Reporter::UnrecognizedVersion(uint64_t offset, int version) {
fprintf(stderr,
"%s: CFI frame description entry at offset 0x%" PRIx64 " in '%s':"
" CIE specifies unrecognized version: %d\n",
filename_.c_str(), offset, section_.c_str(), version);
}
void CallFrameInfo::Reporter::UnrecognizedAugmentation(uint64_t offset,
const string& aug) {
fprintf(stderr,
"%s: CFI frame description entry at offset 0x%" PRIx64 " in '%s':"
" CIE specifies unrecognized augmentation: '%s'\n",
filename_.c_str(), offset, section_.c_str(), aug.c_str());
}
void CallFrameInfo::Reporter::InvalidPointerEncoding(uint64_t offset,
uint8_t encoding) {
fprintf(stderr,
"%s: CFI common information entry at offset 0x%" PRIx64 " in '%s':"
" 'z' augmentation specifies invalid pointer encoding: 0x%02x\n",
filename_.c_str(), offset, section_.c_str(), encoding);
}
void CallFrameInfo::Reporter::UnusablePointerEncoding(uint64_t offset,
uint8_t encoding) {
fprintf(stderr,
"%s: CFI common information entry at offset 0x%" PRIx64 " 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);
}
void CallFrameInfo::Reporter::RestoreInCIE(uint64_t offset, uint64_t insn_offset) {
fprintf(stderr,
"%s: CFI common information entry at offset 0x%" PRIx64 " in '%s':"
" the DW_CFA_restore instruction at offset 0x%" PRIx64
" cannot be used in a common information entry\n",
filename_.c_str(), offset, section_.c_str(), insn_offset);
}
void CallFrameInfo::Reporter::BadInstruction(uint64_t offset,
CallFrameInfo::EntryKind kind,
uint64_t insn_offset) {
fprintf(stderr,
"%s: CFI %s at offset 0x%" PRIx64 " in section '%s':"
" the instruction at offset 0x%" PRIx64 " is unrecognized\n",
filename_.c_str(), CallFrameInfo::KindName(kind),
offset, section_.c_str(), insn_offset);
}
void CallFrameInfo::Reporter::NoCFARule(uint64_t offset,
CallFrameInfo::EntryKind kind,
uint64_t insn_offset) {
fprintf(stderr,
"%s: CFI %s at offset 0x%" PRIx64 " in section '%s':"
" the instruction at offset 0x%" PRIx64 " 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);
}
void CallFrameInfo::Reporter::EmptyStateStack(uint64_t offset,
CallFrameInfo::EntryKind kind,
uint64_t insn_offset) {
fprintf(stderr,
"%s: CFI %s at offset 0x%" PRIx64 " in section '%s':"
" the DW_CFA_restore_state instruction at offset 0x%" PRIx64
" 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);
}
void CallFrameInfo::Reporter::ClearingCFARule(uint64_t offset,
CallFrameInfo::EntryKind kind,
uint64_t insn_offset) {
fprintf(stderr,
"%s: CFI %s at offset 0x%" PRIx64 " in section '%s':"
" the DW_CFA_restore_state instruction at offset 0x%" PRIx64
" would clear the CFA rule in effect\n",
filename_.c_str(), CallFrameInfo::KindName(kind), offset,
section_.c_str(), insn_offset);
}
} // namespace google_breakpad