ClickHouse/src/Common/Dwarf.h

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#pragma once
#if defined(__ELF__) && !defined(__FreeBSD__)
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/*
* 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 <string>
#include <string_view>
#include <variant>
namespace DB
{
class Elf;
/**
* DWARF record parser.
*
* We only implement enough DWARF functionality to convert from PC address
* to file and line number information.
*
* This means (although they're not part of the public API of this class), we
* can parse Debug Information Entries (DIEs), abbreviations, attributes (of
* all forms), and we can interpret bytecode for the line number VM.
*
* We can interpret DWARF records of version 2, 3, or 4, although we don't
* actually support many of the version 4 features (such as VLIW, multiple
* operations per instruction)
*
* Note that the DWARF record parser does not allocate heap memory at all.
* This is on purpose: you can use the parser from
* memory-constrained situations (such as an exception handler for
* std::out_of_memory) If it weren't for this requirement, some things would
* be much simpler: the Path class would be unnecessary and would be replaced
* with a std::string; the list of file names in the line number VM would be
* kept as a vector of strings instead of re-executing the program to look for
* DW_LNE_define_file instructions, etc.
*/
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class Dwarf final
{
// Note that Dwarf uses (and returns) std::string_view a lot.
// The std::string_view point within sections in the ELF file, and so will
// be live for as long as the passed-in Elf is live.
public:
/** Create a DWARF parser around an ELF file. */
explicit Dwarf(const Elf & elf);
/**
* Represent a file path a s collection of three parts (base directory,
* subdirectory, and file).
*/
class Path
{
public:
Path() {}
Path(std::string_view baseDir, std::string_view subDir, std::string_view file);
std::string_view baseDir() const { return baseDir_; }
std::string_view subDir() const { return subDir_; }
std::string_view file() const { return file_; }
size_t size() const;
/**
* Copy the Path to a buffer of size bufSize.
*
* toBuffer behaves like snprintf: It will always null-terminate the
* buffer (so it will copy at most bufSize-1 bytes), and it will return
* the number of bytes that would have been written if there had been
* enough room, so, if toBuffer returns a value >= bufSize, the output
* was truncated.
*/
size_t toBuffer(char * buf, size_t bufSize) const;
void toString(std::string & dest) const;
std::string toString() const
{
std::string s;
toString(s);
return s;
}
// TODO(tudorb): Implement operator==, operator!=; not as easy as it
// seems as the same path can be represented in multiple ways
private:
std::string_view baseDir_;
std::string_view subDir_;
std::string_view file_;
};
enum class LocationInfoMode
{
// Don't resolve location info.
DISABLED,
// Perform CU lookup using .debug_aranges (might be incomplete).
FAST,
// Scan all CU in .debug_info (slow!) on .debug_aranges lookup failure.
FULL,
};
struct LocationInfo
{
bool hasMainFile = false;
Path mainFile;
bool hasFileAndLine = false;
Path file;
uint64_t line = 0;
};
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/** Find the file and line number information corresponding to address.
* The address must be physical - offset in object file without offset in virtual memory where the object is loaded.
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*/
bool findAddress(uintptr_t address, LocationInfo & info, LocationInfoMode mode) const;
private:
static bool findDebugInfoOffset(uintptr_t address, std::string_view aranges, uint64_t & offset);
void init();
bool findLocation(uintptr_t address, std::string_view & infoEntry, LocationInfo & info) const;
const Elf * elf_;
// DWARF section made up of chunks, each prefixed with a length header.
// The length indicates whether the chunk is DWARF-32 or DWARF-64, which
// guides interpretation of "section offset" records.
// (yes, DWARF-32 and DWARF-64 sections may coexist in the same file)
class Section
{
public:
Section() : is64Bit_(false) {}
explicit Section(std::string_view d);
// Return next chunk, if any; the 4- or 12-byte length was already
// parsed and isn't part of the chunk.
bool next(std::string_view & chunk);
// Is the current chunk 64 bit?
bool is64Bit() const { return is64Bit_; }
private:
// Yes, 32- and 64- bit sections may coexist. Yikes!
bool is64Bit_;
std::string_view data_;
};
// Abbreviation for a Debugging Information Entry.
struct DIEAbbreviation
{
uint64_t code;
uint64_t tag;
bool hasChildren;
struct Attribute
{
uint64_t name;
uint64_t form;
};
std::string_view attributes;
};
// Interpreter for the line number bytecode VM
class LineNumberVM
{
public:
LineNumberVM(std::string_view data, std::string_view compilationDirectory);
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bool findAddress(uintptr_t target, Path & file, uint64_t & line);
private:
void init();
void reset();
// Execute until we commit one new row to the line number matrix
bool next(std::string_view & program);
enum StepResult
{
CONTINUE, // Continue feeding opcodes
COMMIT, // Commit new <address, file, line> tuple
END, // End of sequence
};
// Execute one opcode
StepResult step(std::string_view & program);
struct FileName
{
std::string_view relativeName;
// 0 = current compilation directory
// otherwise, 1-based index in the list of include directories
uint64_t directoryIndex;
};
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// Read one FileName object, remove_prefix program
static bool readFileName(std::string_view & program, FileName & fn);
// Get file name at given index; may be in the initial table
// (fileNames_) or defined using DW_LNE_define_file (and we reexecute
// enough of the program to find it, if so)
FileName getFileName(uint64_t index) const;
// Get include directory at given index
std::string_view getIncludeDirectory(uint64_t index) const;
// Execute opcodes until finding a DW_LNE_define_file and return true;
// return file at the end.
bool nextDefineFile(std::string_view & program, FileName & fn) const;
// Initialization
bool is64Bit_;
std::string_view data_;
std::string_view compilationDirectory_;
// Header
uint16_t version_;
uint8_t minLength_;
bool defaultIsStmt_;
int8_t lineBase_;
uint8_t lineRange_;
uint8_t opcodeBase_;
const uint8_t * standardOpcodeLengths_;
std::string_view includeDirectories_;
size_t includeDirectoryCount_;
std::string_view fileNames_;
size_t fileNameCount_;
// State machine registers
uint64_t address_;
uint64_t file_;
uint64_t line_;
uint64_t column_;
bool isStmt_;
bool basicBlock_;
bool endSequence_;
bool prologueEnd_;
bool epilogueBegin_;
uint64_t isa_;
uint64_t discriminator_;
};
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// Read an abbreviation from a std::string_view, return true if at end; remove_prefix section
static bool readAbbreviation(std::string_view & section, DIEAbbreviation & abbr);
// Get abbreviation corresponding to a code, in the chunk starting at
// offset in the .debug_abbrev section
DIEAbbreviation getAbbreviation(uint64_t code, uint64_t offset) const;
// Read one attribute <name, form> pair, remove_prefix sp; returns <0, 0> at end.
static DIEAbbreviation::Attribute readAttribute(std::string_view & sp);
// Read one attribute value, remove_prefix sp
typedef std::variant<uint64_t, std::string_view> AttributeValue;
AttributeValue readAttributeValue(std::string_view & sp, uint64_t form, bool is64Bit) const;
// Get an ELF section by name, return true if found
bool getSection(const char * name, std::string_view * section) const;
// Get a string from the .debug_str section
std::string_view getStringFromStringSection(uint64_t offset) const;
std::string_view info_; // .debug_info
std::string_view abbrev_; // .debug_abbrev
std::string_view aranges_; // .debug_aranges
std::string_view line_; // .debug_line
std::string_view strings_; // .debug_str
};
}
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#endif