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8650c19967
ClickHouse/src/Common/Dwarf.cpp
Ivan Lezhankin 06446b4f08 dbms/ → src/
2020-04-03 18:14:31 +03:00

1037 lines
30 KiB
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#if defined(__ELF__) && !defined(__FreeBSD__)
/*
* Copyright 2012-present Facebook, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/** This file was edited for ClickHouse.
*/
#include <optional>
#include <string.h>
#include <Common/Elf.h>
#include <Common/Dwarf.h>
#include <Common/Exception.h>
#define DW_CHILDREN_no 0
#define DW_FORM_addr 1
#define DW_FORM_block1 0x0a
#define DW_FORM_block2 3
#define DW_FORM_block4 4
#define DW_FORM_block 9
#define DW_FORM_exprloc 0x18
#define DW_FORM_data1 0x0b
#define DW_FORM_ref1 0x11
#define DW_FORM_data2 0x05
#define DW_FORM_ref2 0x12
#define DW_FORM_data4 0x06
#define DW_FORM_ref4 0x13
#define DW_FORM_data8 0x07
#define DW_FORM_ref8 0x14
#define DW_FORM_sdata 0x0d
#define DW_FORM_udata 0x0f
#define DW_FORM_ref_udata 0x15
#define DW_FORM_flag 0x0c
#define DW_FORM_flag_present 0x19
#define DW_FORM_sec_offset 0x17
#define DW_FORM_ref_addr 0x10
#define DW_FORM_string 0x08
#define DW_FORM_strp 0x0e
#define DW_FORM_indirect 0x16
#define DW_TAG_compile_unit 0x11
#define DW_AT_stmt_list 0x10
#define DW_AT_comp_dir 0x1b
#define DW_AT_name 0x03
#define DW_LNE_define_file 0x03
#define DW_LNS_copy 0x01
#define DW_LNS_advance_pc 0x02
#define DW_LNS_advance_line 0x03
#define DW_LNS_set_file 0x04
#define DW_LNS_set_column 0x05
#define DW_LNS_negate_stmt 0x06
#define DW_LNS_set_basic_block 0x07
#define DW_LNS_const_add_pc 0x08
#define DW_LNS_fixed_advance_pc 0x09
#define DW_LNS_set_prologue_end 0x0a
#define DW_LNS_set_epilogue_begin 0x0b
#define DW_LNS_set_isa 0x0c
#define DW_LNE_end_sequence 0x01
#define DW_LNE_set_address 0x02
#define DW_LNE_set_discriminator 0x04
namespace DB
{
namespace ErrorCodes
{
extern const int CANNOT_PARSE_DWARF;
}
Dwarf::Dwarf(const Elf & elf) : elf_(&elf)
{
init();
}
Dwarf::Section::Section(std::string_view d) : is64Bit_(false), data_(d)
{
}
#define SAFE_CHECK(cond, message) do { if (!(cond)) throw Exception(message, ErrorCodes::CANNOT_PARSE_DWARF); } while (false)
namespace
{
// All following read* functions read from a std::string_view, advancing the
// std::string_view, and aborting if there's not enough room.
// Read (bitwise) one object of type T
template <typename T>
std::enable_if_t<std::is_pod_v<T>, T> read(std::string_view & sp)
{
SAFE_CHECK(sp.size() >= sizeof(T), "underflow");
T x;
memcpy(&x, sp.data(), sizeof(T));
sp.remove_prefix(sizeof(T));
return x;
}
// Read ULEB (unsigned) varint value; algorithm from the DWARF spec
uint64_t readULEB(std::string_view & sp, uint8_t & shift, uint8_t & val)
{
uint64_t r = 0;
shift = 0;
do
{
val = read<uint8_t>(sp);
r |= (uint64_t(val & 0x7f) << shift);
shift += 7;
} while (val & 0x80);
return r;
}
uint64_t readULEB(std::string_view & sp)
{
uint8_t shift;
uint8_t val;
return readULEB(sp, shift, val);
}
// Read SLEB (signed) varint value; algorithm from the DWARF spec
int64_t readSLEB(std::string_view & sp)
{
uint8_t shift;
uint8_t val;
uint64_t r = readULEB(sp, shift, val);
if (shift < 64 && (val & 0x40))
{
r |= -(1ULL << shift); // sign extend
}
return r;
}
// Read a value of "section offset" type, which may be 4 or 8 bytes
uint64_t readOffset(std::string_view & sp, bool is64Bit)
{
return is64Bit ? read<uint64_t>(sp) : read<uint32_t>(sp);
}
// Read "len" bytes
std::string_view readBytes(std::string_view & sp, uint64_t len)
{
SAFE_CHECK(len >= sp.size(), "invalid string length");
std::string_view ret(sp.data(), len);
sp.remove_prefix(len);
return ret;
}
// Read a null-terminated string
std::string_view readNullTerminated(std::string_view & sp)
{
const char * p = static_cast<const char *>(memchr(sp.data(), 0, sp.size()));
SAFE_CHECK(p, "invalid null-terminated string");
std::string_view ret(sp.data(), p - sp.data());
sp = std::string_view(p + 1, sp.size());
return ret;
}
// Skip over padding until sp.data() - start is a multiple of alignment
void skipPadding(std::string_view & sp, const char * start, size_t alignment)
{
size_t remainder = (sp.data() - start) % alignment;
if (remainder)
{
SAFE_CHECK(alignment - remainder <= sp.size(), "invalid padding");
sp.remove_prefix(alignment - remainder);
}
}
}
Dwarf::Path::Path(std::string_view baseDir, std::string_view subDir, std::string_view file)
: baseDir_(baseDir), subDir_(subDir), file_(file)
{
using std::swap;
// Normalize
if (file_.empty())
{
baseDir_ = {};
subDir_ = {};
return;
}
if (file_[0] == '/')
{
// file_ is absolute
baseDir_ = {};
subDir_ = {};
}
if (!subDir_.empty() && subDir_[0] == '/')
{
baseDir_ = {}; // subDir_ is absolute
}
// Make sure it's never the case that baseDir_ is empty, but subDir_ isn't.
if (baseDir_.empty())
{
swap(baseDir_, subDir_);
}
}
size_t Dwarf::Path::size() const
{
size_t size = 0;
bool needs_slash = false;
if (!baseDir_.empty())
{
size += baseDir_.size();
needs_slash = baseDir_.back() != '/';
}
if (!subDir_.empty())
{
size += needs_slash;
size += subDir_.size();
needs_slash = subDir_.back() != '/';
}
if (!file_.empty())
{
size += needs_slash;
size += file_.size();
}
return size;
}
size_t Dwarf::Path::toBuffer(char * buf, size_t bufSize) const
{
size_t total_size = 0;
bool needs_slash = false;
auto append = [&](std::string_view sp)
{
if (bufSize >= 2)
{
size_t to_copy = std::min(sp.size(), bufSize - 1);
memcpy(buf, sp.data(), to_copy);
buf += to_copy;
bufSize -= to_copy;
}
total_size += sp.size();
};
if (!baseDir_.empty())
{
append(baseDir_);
needs_slash = baseDir_.back() != '/';
}
if (!subDir_.empty())
{
if (needs_slash)
{
append("/");
}
append(subDir_);
needs_slash = subDir_.back() != '/';
}
if (!file_.empty())
{
if (needs_slash)
{
append("/");
}
append(file_);
}
if (bufSize)
{
*buf = '\0';
}
SAFE_CHECK(total_size == size(), "Size mismatch");
return total_size;
}
void Dwarf::Path::toString(std::string & dest) const
{
size_t initial_size = dest.size();
dest.reserve(initial_size + size());
if (!baseDir_.empty())
{
dest.append(baseDir_.begin(), baseDir_.end());
}
if (!subDir_.empty())
{
if (!dest.empty() && dest.back() != '/')
{
dest.push_back('/');
}
dest.append(subDir_.begin(), subDir_.end());
}
if (!file_.empty())
{
if (!dest.empty() && dest.back() != '/')
{
dest.push_back('/');
}
dest.append(file_.begin(), file_.end());
}
SAFE_CHECK(dest.size() == initial_size + size(), "Size mismatch");
}
// Next chunk in section
bool Dwarf::Section::next(std::string_view & chunk)
{
chunk = data_;
if (chunk.empty())
return false;
// Initial length is a uint32_t value for a 32-bit section, and
// a 96-bit value (0xffffffff followed by the 64-bit length) for a 64-bit
// section.
auto initial_length = read<uint32_t>(chunk);
is64Bit_ = (initial_length == uint32_t(-1));
auto length = is64Bit_ ? read<uint64_t>(chunk) : initial_length;
SAFE_CHECK(length <= chunk.size(), "invalid DWARF section");
chunk = std::string_view(chunk.data(), length);
data_ = std::string_view(chunk.end(), data_.end() - chunk.end());
return true;
}
bool Dwarf::getSection(const char * name, std::string_view * section) const
{
std::optional<Elf::Section> elf_section = elf_->findSectionByName(name);
if (!elf_section)
return false;
#ifdef SHF_COMPRESSED
if (elf_section->header.sh_flags & SHF_COMPRESSED)
return false;
#endif
*section = { elf_section->begin(), elf_section->size()};
return true;
}
void Dwarf::init()
{
// Make sure that all .debug_* sections exist
if (!getSection(".debug_info", &info_)
|| !getSection(".debug_abbrev", &abbrev_)
|| !getSection(".debug_line", &line_)
|| !getSection(".debug_str", &strings_))
{
elf_ = nullptr;
return;
}
// Optional: fast address range lookup. If missing .debug_info can
// be used - but it's much slower (linear scan).
getSection(".debug_aranges", &aranges_);
}
bool Dwarf::readAbbreviation(std::string_view & section, DIEAbbreviation & abbr)
{
// abbreviation code
abbr.code = readULEB(section);
if (abbr.code == 0)
return false;
// abbreviation tag
abbr.tag = readULEB(section);
// does this entry have children?
abbr.hasChildren = (read<uint8_t>(section) != DW_CHILDREN_no);
// attributes
const char * attribute_begin = section.data();
for (;;)
{
SAFE_CHECK(!section.empty(), "invalid attribute section");
auto attr = readAttribute(section);
if (attr.name == 0 && attr.form == 0)
break;
}
abbr.attributes = std::string_view(attribute_begin, section.data() - attribute_begin);
return true;
}
Dwarf::DIEAbbreviation::Attribute Dwarf::readAttribute(std::string_view & sp)
{
return {readULEB(sp), readULEB(sp)};
}
Dwarf::DIEAbbreviation Dwarf::getAbbreviation(uint64_t code, uint64_t offset) const
{
// Linear search in the .debug_abbrev section, starting at offset
std::string_view section = abbrev_;
section.remove_prefix(offset);
Dwarf::DIEAbbreviation abbr;
while (readAbbreviation(section, abbr))
if (abbr.code == code)
return abbr;
SAFE_CHECK(false, "could not find abbreviation code");
}
Dwarf::AttributeValue Dwarf::readAttributeValue(std::string_view & sp, uint64_t form, bool is64Bit) const
{
switch (form)
{
case DW_FORM_addr:
return uint64_t(read<uintptr_t>(sp));
case DW_FORM_block1:
return readBytes(sp, read<uint8_t>(sp));
case DW_FORM_block2:
return readBytes(sp, read<uint16_t>(sp));
case DW_FORM_block4:
return readBytes(sp, read<uint32_t>(sp));
case DW_FORM_block: [[fallthrough]];
case DW_FORM_exprloc:
return readBytes(sp, readULEB(sp));
case DW_FORM_data1: [[fallthrough]];
case DW_FORM_ref1:
return uint64_t(read<uint8_t>(sp));
case DW_FORM_data2: [[fallthrough]];
case DW_FORM_ref2:
return uint64_t(read<uint16_t>(sp));
case DW_FORM_data4: [[fallthrough]];
case DW_FORM_ref4:
return uint64_t(read<uint32_t>(sp));
case DW_FORM_data8: [[fallthrough]];
case DW_FORM_ref8:
return read<uint64_t>(sp);
case DW_FORM_sdata:
return uint64_t(readSLEB(sp));
case DW_FORM_udata: [[fallthrough]];
case DW_FORM_ref_udata:
return readULEB(sp);
case DW_FORM_flag:
return uint64_t(read<uint8_t>(sp));
case DW_FORM_flag_present:
return uint64_t(1);
case DW_FORM_sec_offset: [[fallthrough]];
case DW_FORM_ref_addr:
return readOffset(sp, is64Bit);
case DW_FORM_string:
return readNullTerminated(sp);
case DW_FORM_strp:
return getStringFromStringSection(readOffset(sp, is64Bit));
case DW_FORM_indirect: // form is explicitly specified
return readAttributeValue(sp, readULEB(sp), is64Bit);
default:
SAFE_CHECK(false, "invalid attribute form");
}
}
std::string_view Dwarf::getStringFromStringSection(uint64_t offset) const
{
SAFE_CHECK(offset < strings_.size(), "invalid strp offset");
std::string_view sp(strings_);
sp.remove_prefix(offset);
return readNullTerminated(sp);
}
/**
* Find @address in .debug_aranges and return the offset in
* .debug_info for compilation unit to which this address belongs.
*/
bool Dwarf::findDebugInfoOffset(uintptr_t address, std::string_view aranges, uint64_t & offset)
{
Section aranges_section(aranges);
std::string_view chunk;
while (aranges_section.next(chunk))
{
auto version = read<uint16_t>(chunk);
SAFE_CHECK(version == 2, "invalid aranges version");
offset = readOffset(chunk, aranges_section.is64Bit());
auto address_size = read<uint8_t>(chunk);
SAFE_CHECK(address_size == sizeof(uintptr_t), "invalid address size");
auto segment_size = read<uint8_t>(chunk);
SAFE_CHECK(segment_size == 0, "segmented architecture not supported");
// Padded to a multiple of 2 addresses.
// Strangely enough, this is the only place in the DWARF spec that requires
// padding.
skipPadding(chunk, aranges.data(), 2 * sizeof(uintptr_t));
for (;;)
{
auto start = read<uintptr_t>(chunk);
auto length = read<uintptr_t>(chunk);
if (start == 0 && length == 0)
break;
// Is our address in this range?
if (address >= start && address < start + length)
return true;
}
}
return false;
}
/**
* Find the @locationInfo for @address in the compilation unit represented
* by the @sp .debug_info entry.
* Returns whether the address was found.
* Advances @sp to the next entry in .debug_info.
*/
bool Dwarf::findLocation(uintptr_t address, std::string_view & infoEntry, LocationInfo & locationInfo) const
{
// For each compilation unit compiled with a DWARF producer, a
// contribution is made to the .debug_info section of the object
// file. Each such contribution consists of a compilation unit
// header (see Section 7.5.1.1) followed by a single
// DW_TAG_compile_unit or DW_TAG_partial_unit debugging information
// entry, together with its children.
// 7.5.1.1 Compilation Unit Header
// 1. unit_length (4B or 12B): read by Section::next
// 2. version (2B)
// 3. debug_abbrev_offset (4B or 8B): offset into the .debug_abbrev section
// 4. address_size (1B)
Section debug_info_section(infoEntry);
std::string_view chunk;
SAFE_CHECK(debug_info_section.next(chunk), "invalid debug info");
auto version = read<uint16_t>(chunk);
SAFE_CHECK(version >= 2 && version <= 4, "invalid info version");
uint64_t abbrev_offset = readOffset(chunk, debug_info_section.is64Bit());
auto address_size = read<uint8_t>(chunk);
SAFE_CHECK(address_size == sizeof(uintptr_t), "invalid address size");
// We survived so far. The first (and only) DIE should be DW_TAG_compile_unit
// NOTE: - binutils <= 2.25 does not issue DW_TAG_partial_unit.
// - dwarf compression tools like `dwz` may generate it.
// TODO(tudorb): Handle DW_TAG_partial_unit?
auto code = readULEB(chunk);
SAFE_CHECK(code != 0, "invalid code");
auto abbr = getAbbreviation(code, abbrev_offset);
SAFE_CHECK(abbr.tag == DW_TAG_compile_unit, "expecting compile unit entry");
// Skip children entries, remove_prefix to the next compilation unit entry.
infoEntry.remove_prefix(chunk.end() - infoEntry.begin());
// Read attributes, extracting the few we care about
bool found_line_offset = false;
uint64_t line_offset = 0;
std::string_view compilation_directory;
std::string_view main_file_name;
DIEAbbreviation::Attribute attr;
std::string_view attributes = abbr.attributes;
for (;;)
{
attr = readAttribute(attributes);
if (attr.name == 0 && attr.form == 0)
{
break;
}
auto val = readAttributeValue(chunk, attr.form, debug_info_section.is64Bit());
switch (attr.name)
{
case DW_AT_stmt_list:
// Offset in .debug_line for the line number VM program for this
// compilation unit
line_offset = std::get<uint64_t>(val);
found_line_offset = true;
break;
case DW_AT_comp_dir:
// Compilation directory
compilation_directory = std::get<std::string_view>(val);
break;
case DW_AT_name:
// File name of main file being compiled
main_file_name = std::get<std::string_view>(val);
break;
}
}
if (!main_file_name.empty())
{
locationInfo.hasMainFile = true;
locationInfo.mainFile = Path(compilation_directory, "", main_file_name);
}
if (!found_line_offset)
{
return false;
}
std::string_view line_section(line_);
line_section.remove_prefix(line_offset);
LineNumberVM line_vm(line_section, compilation_directory);
// Execute line number VM program to find file and line
locationInfo.hasFileAndLine = line_vm.findAddress(address, locationInfo.file, locationInfo.line);
return locationInfo.hasFileAndLine;
}
bool Dwarf::findAddress(uintptr_t address, LocationInfo & locationInfo, LocationInfoMode mode) const
{
locationInfo = LocationInfo();
if (mode == LocationInfoMode::DISABLED)
{
return false;
}
if (!elf_)
{ // No file.
return false;
}
if (!aranges_.empty())
{
// Fast path: find the right .debug_info entry by looking up the
// address in .debug_aranges.
uint64_t offset = 0;
if (findDebugInfoOffset(address, aranges_, offset))
{
// Read compilation unit header from .debug_info
std::string_view info_entry(info_);
info_entry.remove_prefix(offset);
findLocation(address, info_entry, locationInfo);
return locationInfo.hasFileAndLine;
}
else if (mode == LocationInfoMode::FAST)
{
// NOTE: Clang (when using -gdwarf-aranges) doesn't generate entries
// in .debug_aranges for some functions, but always generates
// .debug_info entries. Scanning .debug_info is slow, so fall back to
// it only if such behavior is requested via LocationInfoMode.
return false;
}
else
{
SAFE_CHECK(mode == LocationInfoMode::FULL, "unexpected mode");
// Fall back to the linear scan.
}
}
// Slow path (linear scan): Iterate over all .debug_info entries
// and look for the address in each compilation unit.
std::string_view info_entry(info_);
while (!info_entry.empty() && !locationInfo.hasFileAndLine)
findLocation(address, info_entry, locationInfo);
return locationInfo.hasFileAndLine;
}
Dwarf::LineNumberVM::LineNumberVM(std::string_view data, std::string_view compilationDirectory)
: compilationDirectory_(compilationDirectory)
{
Section section(data);
SAFE_CHECK(section.next(data_), "invalid line number VM");
is64Bit_ = section.is64Bit();
init();
reset();
}
void Dwarf::LineNumberVM::reset()
{
address_ = 0;
file_ = 1;
line_ = 1;
column_ = 0;
isStmt_ = defaultIsStmt_;
basicBlock_ = false;
endSequence_ = false;
prologueEnd_ = false;
epilogueBegin_ = false;
isa_ = 0;
discriminator_ = 0;
}
void Dwarf::LineNumberVM::init()
{
version_ = read<uint16_t>(data_);
SAFE_CHECK(version_ >= 2 && version_ <= 4, "invalid version in line number VM");
uint64_t header_length = readOffset(data_, is64Bit_);
SAFE_CHECK(header_length <= data_.size(), "invalid line number VM header length");
std::string_view header(data_.data(), header_length);
data_ = std::string_view(header.end(), data_.end() - header.end());
minLength_ = read<uint8_t>(header);
if (version_ == 4)
{ // Version 2 and 3 records don't have this
uint8_t max_ops_per_instruction = read<uint8_t>(header);
SAFE_CHECK(max_ops_per_instruction == 1, "VLIW not supported");
}
defaultIsStmt_ = read<uint8_t>(header);
lineBase_ = read<int8_t>(header); // yes, signed
lineRange_ = read<uint8_t>(header);
opcodeBase_ = read<uint8_t>(header);
SAFE_CHECK(opcodeBase_ != 0, "invalid opcode base");
standardOpcodeLengths_ = reinterpret_cast<const uint8_t *>(header.data()); //-V506
header.remove_prefix(opcodeBase_ - 1);
// We don't want to use heap, so we don't keep an unbounded amount of state.
// We'll just skip over include directories and file names here, and
// we'll loop again when we actually need to retrieve one.
std::string_view sp;
const char * tmp = header.data();
includeDirectoryCount_ = 0;
while (!(sp = readNullTerminated(header)).empty())
{
++includeDirectoryCount_;
}
includeDirectories_ = std::string_view(tmp, header.data() - tmp);
tmp = header.data();
FileName fn;
fileNameCount_ = 0;
while (readFileName(header, fn))
{
++fileNameCount_;
}
fileNames_ = std::string_view(tmp, header.data() - tmp);
}
bool Dwarf::LineNumberVM::next(std::string_view & program)
{
Dwarf::LineNumberVM::StepResult ret;
do
{
ret = step(program);
} while (ret == CONTINUE);
return (ret == COMMIT);
}
Dwarf::LineNumberVM::FileName Dwarf::LineNumberVM::getFileName(uint64_t index) const
{
SAFE_CHECK(index != 0, "invalid file index 0");
FileName fn;
if (index <= fileNameCount_)
{
std::string_view file_names = fileNames_;
for (; index; --index)
{
if (!readFileName(file_names, fn))
{
abort();
}
}
return fn;
}
index -= fileNameCount_;
std::string_view program = data_;
for (; index; --index)
{
SAFE_CHECK(nextDefineFile(program, fn), "invalid file index");
}
return fn;
}
std::string_view Dwarf::LineNumberVM::getIncludeDirectory(uint64_t index) const
{
if (index == 0)
{
return std::string_view();
}
SAFE_CHECK(index <= includeDirectoryCount_, "invalid include directory");
std::string_view include_directories = includeDirectories_;
std::string_view dir;
for (; index; --index)
{
dir = readNullTerminated(include_directories);
if (dir.empty())
{
abort(); // BUG
}
}
return dir;
}
bool Dwarf::LineNumberVM::readFileName(std::string_view & program, FileName & fn)
{
fn.relativeName = readNullTerminated(program);
if (fn.relativeName.empty())
{
return false;
}
fn.directoryIndex = readULEB(program);
// Skip over file size and last modified time
readULEB(program);
readULEB(program);
return true;
}
bool Dwarf::LineNumberVM::nextDefineFile(std::string_view & program, FileName & fn) const
{
while (!program.empty())
{
auto opcode = read<uint8_t>(program);
if (opcode >= opcodeBase_)
{ // special opcode
continue;
}
if (opcode != 0)
{ // standard opcode
// Skip, slurp the appropriate number of LEB arguments
uint8_t arg_count = standardOpcodeLengths_[opcode - 1];
while (arg_count--)
{
readULEB(program);
}
continue;
}
// Extended opcode
auto length = readULEB(program);
// the opcode itself should be included in the length, so length >= 1
SAFE_CHECK(length != 0, "invalid extended opcode length");
read<uint8_t>(program); // extended opcode
--length;
if (opcode == DW_LNE_define_file)
{
SAFE_CHECK(readFileName(program, fn), "invalid empty file in DW_LNE_define_file");
return true;
}
program.remove_prefix(length);
}
return false;
}
Dwarf::LineNumberVM::StepResult Dwarf::LineNumberVM::step(std::string_view & program)
{
auto opcode = read<uint8_t>(program);
if (opcode >= opcodeBase_)
{ // special opcode
uint8_t adjusted_opcode = opcode - opcodeBase_;
uint8_t op_advance = adjusted_opcode / lineRange_;
address_ += minLength_ * op_advance;
line_ += lineBase_ + adjusted_opcode % lineRange_;
basicBlock_ = false;
prologueEnd_ = false;
epilogueBegin_ = false;
discriminator_ = 0;
return COMMIT;
}
if (opcode != 0)
{ // standard opcode
// Only interpret opcodes that are recognized by the version we're parsing;
// the others are vendor extensions and we should ignore them.
switch (opcode)
{
case DW_LNS_copy:
basicBlock_ = false;
prologueEnd_ = false;
epilogueBegin_ = false;
discriminator_ = 0;
return COMMIT;
case DW_LNS_advance_pc:
address_ += minLength_ * readULEB(program);
return CONTINUE;
case DW_LNS_advance_line:
line_ += readSLEB(program);
return CONTINUE;
case DW_LNS_set_file:
file_ = readULEB(program);
return CONTINUE;
case DW_LNS_set_column:
column_ = readULEB(program);
return CONTINUE;
case DW_LNS_negate_stmt:
isStmt_ = !isStmt_;
return CONTINUE;
case DW_LNS_set_basic_block:
basicBlock_ = true;
return CONTINUE;
case DW_LNS_const_add_pc:
address_ += minLength_ * ((255 - opcodeBase_) / lineRange_);
return CONTINUE;
case DW_LNS_fixed_advance_pc:
address_ += read<uint16_t>(program);
return CONTINUE;
case DW_LNS_set_prologue_end:
if (version_ == 2)
{
break; // not supported in version 2
}
prologueEnd_ = true;
return CONTINUE;
case DW_LNS_set_epilogue_begin:
if (version_ == 2)
{
break; // not supported in version 2
}
epilogueBegin_ = true;
return CONTINUE;
case DW_LNS_set_isa:
if (version_ == 2)
{
break; // not supported in version 2
}
isa_ = readULEB(program);
return CONTINUE;
}
// Unrecognized standard opcode, slurp the appropriate number of LEB
// arguments.
uint8_t arg_count = standardOpcodeLengths_[opcode - 1];
while (arg_count--)
{
readULEB(program);
}
return CONTINUE;
}
// Extended opcode
auto length = readULEB(program);
// the opcode itself should be included in the length, so length >= 1
SAFE_CHECK(length != 0, "invalid extended opcode length");
auto extended_opcode = read<uint8_t>(program);
--length;
switch (extended_opcode)
{
case DW_LNE_end_sequence:
return END;
case DW_LNE_set_address:
address_ = read<uintptr_t>(program);
return CONTINUE;
case DW_LNE_define_file:
// We can't process DW_LNE_define_file here, as it would require us to
// use unbounded amounts of state (ie. use the heap). We'll do a second
// pass (using nextDefineFile()) if necessary.
break;
case DW_LNE_set_discriminator:
discriminator_ = readULEB(program);
return CONTINUE;
}
// Unrecognized extended opcode
program.remove_prefix(length);
return CONTINUE;
}
bool Dwarf::LineNumberVM::findAddress(uintptr_t target, Path & file, uint64_t & line)
{
std::string_view program = data_;
// Within each sequence of instructions, the address may only increase.
// Unfortunately, within the same compilation unit, sequences may appear
// in any order. So any sequence is a candidate if it starts at an address
// <= the target address, and we know we've found the target address if
// a candidate crosses the target address.
enum State
{
START,
LOW_SEQ, // candidate
HIGH_SEQ
};
State state = START;
reset();
uint64_t prev_file = 0;
uint64_t prev_line = 0;
while (!program.empty())
{
bool seq_end = !next(program);
if (state == START)
{
if (!seq_end)
{
state = address_ <= target ? LOW_SEQ : HIGH_SEQ;
}
}
if (state == LOW_SEQ)
{
if (address_ > target)
{
// Found it! Note that ">" is indeed correct (not ">="), as each
// sequence is guaranteed to have one entry past-the-end (emitted by
// DW_LNE_end_sequence)
if (prev_file == 0)
{
return false;
}
auto fn = getFileName(prev_file);
file = Path(compilationDirectory_, getIncludeDirectory(fn.directoryIndex), fn.relativeName);
line = prev_line;
return true;
}
prev_file = file_;
prev_line = line_;
}
if (seq_end)
{
state = START;
reset();
}
}
return false;
}
}
#endif
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