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android / toolchain / jdk / jdk21 / HEAD / . / src / hotspot / share / utilities / elfFile.hpp
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/*
* Copyright (c) 1997, 2023, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*
*/
#ifndef SHARE_UTILITIES_ELFFILE_HPP
#define SHARE_UTILITIES_ELFFILE_HPP
#if !defined(_WINDOWS) && !defined(__APPLE__) && !defined(_AIX)
#if defined(__OpenBSD__)
#include <sys/exec_elf.h>
#else
#include <elf.h>
#endif
#include <stdio.h>
#ifdef _LP64
typedef Elf64_Half Elf_Half;
typedef Elf64_Word Elf_Word;
typedef Elf64_Off Elf_Off;
typedef Elf64_Addr Elf_Addr;
typedef Elf64_Ehdr Elf_Ehdr;
typedef Elf64_Shdr Elf_Shdr;
typedef Elf64_Phdr Elf_Phdr;
typedef Elf64_Sym Elf_Sym;
#if !defined(_ALLBSD_SOURCE) || defined(__APPLE__)
#define ELF_ST_TYPE ELF64_ST_TYPE
#endif
#else
typedef Elf32_Half Elf_Half;
typedef Elf32_Word Elf_Word;
typedef Elf32_Off Elf_Off;
typedef Elf32_Addr Elf_Addr;
typedef Elf32_Ehdr Elf_Ehdr;
typedef Elf32_Shdr Elf_Shdr;
typedef Elf32_Phdr Elf_Phdr;
typedef Elf32_Sym Elf_Sym;
#if !defined(_ALLBSD_SOURCE) || defined(__APPLE__)
#define ELF_ST_TYPE ELF32_ST_TYPE
#endif
#endif
#include "jvm_md.h"
#include "globalDefinitions.hpp"
#include "memory/allocation.hpp"
#include "utilities/decoder.hpp"
#ifdef ASSERT
// Helper macros to print different log levels during DWARF parsing
#define DWARF_LOG_SUMMARY(format, ...) DWARF_LOG_WITH_LEVEL(1, format, ##__VA_ARGS__) // Same level as error logging
#define DWARF_LOG_ERROR(format, ...) DWARF_LOG_WITH_LEVEL(1, format, ##__VA_ARGS__)
#define DWARF_LOG_INFO(format, ...) DWARF_LOG_WITH_LEVEL(2, format, ##__VA_ARGS__)
#define DWARF_LOG_DEBUG(format, ...) DWARF_LOG_WITH_LEVEL(3, format, ##__VA_ARGS__)
#define DWARF_LOG_TRACE(format, ...) DWARF_LOG_WITH_LEVEL(4, format, ##__VA_ARGS__)
#define DWARF_LOG_WITH_LEVEL(level, format, ...) \
if (TraceDwarfLevel >= level) { \
tty->print("[dwarf] "); \
tty->print_cr(format, ##__VA_ARGS__); \
}
#else
#define DWARF_LOG_SUMMARY(format, ...)
#define DWARF_LOG_ERROR(format, ...)
#define DWARF_LOG_INFO(format, ...)
#define DWARF_LOG_DEBUG(format, ...)
#define DWARF_LOG_TRACE(format, ...)
#endif
class ElfStringTable;
class ElfSymbolTable;
class ElfFuncDescTable;
class DwarfFile;
// ELF section, may or may not have cached data
class ElfSection {
private:
Elf_Shdr _section_hdr;
void* _section_data;
NullDecoder::decoder_status _stat;
public:
ElfSection(FILE* fd, const Elf_Shdr& hdr);
~ElfSection();
NullDecoder::decoder_status status() const { return _stat; }
const Elf_Shdr* section_header() const { return &_section_hdr; }
const void* section_data() const { return (const void*)_section_data; }
private:
// load this section.
// it return no_error, when it fails to cache the section data due to lack of memory
NullDecoder::decoder_status load_section(FILE* const file, const Elf_Shdr& hdr);
};
class FileReader : public StackObj {
protected:
FILE* const _fd;
public:
FileReader(FILE* const fd) : _fd(fd) {};
bool read(void* buf, size_t size);
size_t read_buffer(void* buf, size_t size);
virtual bool set_position(long offset);
};
// Mark current position, so we can get back to it after
// reads.
class MarkedFileReader : public FileReader {
protected:
long _marked_pos;
public:
MarkedFileReader(FILE* const fd);
~MarkedFileReader();
bool has_mark() const { return _marked_pos >= 0; }
};
// ElfFile is basically an elf file parser, which can lookup the symbol
// that is the nearest to the given address.
// Beware, this code is called from vm error reporting code, when vm is already
// in "error" state, so there are scenarios, lookup will fail. We want this
// part of code to be very defensive, and bait out if anything went wrong.
class ElfFile: public CHeapObj<mtInternal> {
friend class ElfDecoder;
private:
// link ElfFiles
ElfFile* _next;
// Elf file
char* _filepath;
FILE* _file;
// symbol tables
ElfSymbolTable* _symbol_tables;
// regular string tables
ElfStringTable* _string_tables;
// section header string table, used for finding section name
ElfStringTable* _shdr_string_table;
// function descriptors table
ElfFuncDescTable* _funcDesc_table;
NullDecoder::decoder_status _status;
DwarfFile* _dwarf_file;
static const char* USR_LIB_DEBUG_DIRECTORY;
protected:
// Elf header
Elf_Ehdr _elfHdr;
public:
ElfFile(const char* filepath);
virtual ~ElfFile();
bool decode(address addr, char* buf, int buflen, int* offset);
bool same_elf_file(const char* filepath) const {
assert(filepath != nullptr, "null file path");
return (_filepath != nullptr && !strcmp(filepath, _filepath));
}
NullDecoder::decoder_status get_status() const {
return _status;
}
// Returns true if the elf file is marked NOT to require an executable stack,
// or if the file could not be opened.
// Returns false if the elf file requires an executable stack, the stack flag
// is not set at all, or if the file can not be read.
// On systems other than linux it always returns false.
static bool specifies_noexecstack(const char* filepath) NOT_LINUX({ return false; });
bool get_source_info(uint32_t offset_in_library, char* filename, size_t filename_len, int* line, bool is_pc_after_call);
private:
// sanity check, if the file is a real elf file
static bool is_elf_file(Elf_Ehdr&);
// parse this elf file
NullDecoder::decoder_status parse_elf(const char* filename);
// load string, symbol and function descriptor tables from the elf file
NullDecoder::decoder_status load_tables();
ElfFile* next() const { return _next; }
void set_next(ElfFile* file) { _next = file; }
#if defined(PPC64) && !defined(ABI_ELFv2)
// find a section by name, return section index
// if there is no such section, return -1
int section_by_name(const char* name, Elf_Shdr& hdr);
#endif
// string tables are stored in a linked list
void add_string_table(ElfStringTable* table);
// symbol tables are stored in a linked list
void add_symbol_table(ElfSymbolTable* table);
// return a string table at specified section index
ElfStringTable* get_string_table(int index);
// Cleanup string, symbol and function descriptor tables
void cleanup_tables();
bool create_new_dwarf_file(const char* filepath);
// Struct to store the debug info read from the .gnu_debuglink section.
struct DebugInfo {
static const uint8_t CRC_LEN = 4;
char _dwarf_filename[JVM_MAXPATHLEN];
uint32_t _crc;
};
// Helper class to create DWARF paths when loading a DWARF file.
class DwarfFilePath {
private:
static const uint16_t MAX_DWARF_PATH_LENGTH = JVM_MAXPATHLEN;
const char* _filename;
char _path[MAX_DWARF_PATH_LENGTH];
const uint32_t _crc;
uint16_t _null_terminator_index; // Index for the current null terminator of the string stored in _path
bool check_valid_path() const {
return _path[MAX_DWARF_PATH_LENGTH - 1] == '\0';
}
void update_null_terminator_index() {
_null_terminator_index = strlen(_path);
}
bool copy_to_path_index(uint16_t index_in_path, const char* src);
public:
DwarfFilePath(DebugInfo& debug_info)
: _filename(debug_info._dwarf_filename), _crc(debug_info._crc), _null_terminator_index(0) {
_path[MAX_DWARF_PATH_LENGTH - 1] = '\0'; // Ensures to have a null terminated string and not read beyond the buffer limit.
}
const char* path() const {
return _path;
}
const char* filename() const {
return _filename;
}
uint32_t crc() const {
return _crc;
}
bool set(const char* src);
bool set_filename_after_last_slash() {
return set_after_last_slash(_filename);
}
bool set_after_last_slash(const char* src);
bool append(const char* src);
};
// Load the DWARF file (.debuginfo) that belongs to this file either from (checked in listed order):
// - Same directory as the library file.
// - User defined path in environmental variable _JVM_DWARF_PATH.
// - Subdirectory .debug in same directory as the library file.
// - /usr/lib/debug directory
bool load_dwarf_file();
bool read_debug_info(DebugInfo* debug_info) const;
bool load_dwarf_file_from_same_directory(DwarfFilePath& dwarf_file_path);
bool load_dwarf_file_from_env_var_path(DwarfFilePath& dwarf_file_path);
bool load_dwarf_file_from_env_path_folder(DwarfFilePath& dwarf_file_path, const char* dwarf_path_from_env, const char* folder);
bool load_dwarf_file_from_debug_sub_directory(DwarfFilePath& dwarf_file_path);
bool load_dwarf_file_from_usr_lib_debug(DwarfFilePath& dwarf_file_path);
bool open_valid_debuginfo_file(const DwarfFilePath& dwarf_file_path);
static uint32_t get_file_crc(FILE* const file);
static uint gnu_debuglink_crc32(uint32_t crc, uint8_t* buf, size_t len);
protected:
FILE* const fd() const { return _file; }
// Read the section header of section 'name'.
bool read_section_header(const char* name, Elf_Shdr& hdr) const;
bool is_valid_dwarf_file() const;
public:
// For whitebox test
static bool _do_not_cache_elf_section;
};
/*
* This class parses and reads filename and line number information from an associated .debuginfo file that belongs to
* this ELF file or directly from this ELF file if there is no separate .debuginfo file. The debug info is written by GCC
* in DWARF - a standardized debugging data format. There are special sections where the DWARF info is written to. These
* sections can either be put into the same ELF file or a separate .debuginfo file. For simplicity, when referring to the
* "DWARF file" or the ".debuginfo file" we just mean the file that contains the required DWARF sections. The current version
* of GCC uses DWARF version 4 as default which is defined in the official standard: http://www.dwarfstd.org/doc/DWARF4.pdf.
* This class is able to parse 32-bit DWARF version 4 for 32 and 64-bit Linux builds. GCC does not emit 64-bit DWARF and
* therefore is not supported by this parser. For some reason, GCC emits DWARF version 3 for the .debug_line section as a
* default. This parser was therefore adapted to support DWARF version 3 and 4 for the .debug_line section. Apart from that,
* other DWARF versions, especially the newest version 5, are not (yet) supported.
*
* Description of used DWARF file sections:
* - .debug_aranges: A table that consists of sets of variable length entries, each set describing the portion of the
* program's address space that is covered by a single compilation unit. In other words, the entries
* describe a mapping between addresses and compilation units.
* - .debug_info: The core DWARF data containing DWARF Information Entries (DIEs). Each DIE consists of a tag and a
* series of attributes. Each (normal) compilation unit is represented by a DIE with the tag
* DW_TAG_compile_unit and contains children. For our purposes, we are only interested in this DIE to
* get to the .debug_line section. We do not care about the children. This parser currently only
* supports normal compilation units and no partial compilation or type units.
* - .debug_abbrev: Represents abbreviation tables for all compilation units. A table for a specific compilation unit
* consists of a series of abbreviation declarations. Each declaration specifies a tag and attributes
* for a DIE. The DIEs from the compilation units in the .debug_info section need the abbreviation table
* to decode their attributes (their meaning and size).
* - .debug_line: Contains filename and line number information for each compilation unit. To get the information, a
* state machine needs to be executed which generates a matrix. Each row of this matrix describes the
* filename and line number (among other information) for a specific offset in the associated ELF library
* file. The state machine is executed until the row for the requested offset is found. The filename and
* line number information can then be fetched with the current register values of the state machine.
*
* Algorithm
* ---------
* Given: Offset into the ELF file library.
* Return: Filename and line number for this offset.
* (1) First, the path to the .debuginfo DWARF file is found by inspecting the .gnu_debuglink section of the library file.
* The DWARF file is then opened by calling the constructor of this class. Once this is done, the processing of the
* DWARF file is initiated by calling find_filename_and_line_number().
* (2) Find the compilation unit offset by reading entries from the section .debug_aranges, which contain address range
* descriptors, until we find the correct descriptor that includes the library offset.
* (3) Find the .debug_line offset for the line number information program from the .debug_info section:
* (a) Parse the compilation unit header from the .debug_info section at the offset obtained by (2).
* (b) Read the debug_abbrev_offset into the .debug_abbrev section that belongs to this compilation unit from the
* header obtained in (3a).
* (c) Read the abbreviation code that immediately follows the compilation unit header from (3a) which is needed to
* find the correct entry in the .debug_abbrev section.
* (d) Find the correct entry in the abbreviation table in the .debug_abbrev section by starting to parse entries at
* the debug_abbrev_offset from (3b) until we find the correct one matching the abbreviation code from (3c).
* (e) Read the specified attributes of the abbreviation entry from (3d) from the compilation unit (in the .debug_info
* section) until we find the attribute DW_AT_stmt_list. This attributes represents an offset into the .debug_line
* section which contains the line number program information to get the filename and the line number.
* (4) Find the filename and line number belonging to the given library offset by running the line number program state
* machine with its registers. This creates a matrix where each row stores information for specific addresses (library
* offsets). The state machine executes different opcodes which modify the state machine registers. Certain opcodes
* will add a new row to the matrix by taking the current values of state machine registers. As soon as the correct
* matrix row matching the library offset is found, we can read the line number from the line register of the state
* machine and parse the filename from the line number program header with the given file index from the file register
* of the state machine.
*
* More details about the different phases can be found at the associated classes and methods. A visualization of the
* algorithm inside the different sections can be found in the class comments for DebugAranges, DebugAbbrev and
* LineNumberProgram further down in this file.
*
* Available (develop) log levels (-XX:TraceDwarfLevel=[1,4]) which are only present in debug builds. Each level prints
* all the logs of the previous levels and adds some more fine-grained logging:
* - Level 1 (summary + errors):
* - Prints the path of parsed DWARF file together with the resulting source information.
* - Prints all errors.
* - Level 2 (info):
* - Prints the found offsets of all DWARF sections
* - Level 3 (debug):
* - Prints the results of the steps (1) - (4) together with the generated line information matrix.
* - Level 4 (trace):
* - Complete information about intermediate states/results when parsing the DWARF file.
*/
class DwarfFile : public ElfFile {
static constexpr uint8_t ADDRESS_SIZE = NOT_LP64(4) LP64_ONLY(8);
// We only support 32-bit DWARF (emitted by GCC) which uses 32-bit values for DWARF section lengths and offsets
// relative to the beginning of a section.
static constexpr uint8_t DWARF_SECTION_OFFSET_SIZE = 4;
class MarkedDwarfFileReader : public MarkedFileReader {
private:
long _current_pos;
long _max_pos; // Used to guarantee that we stop reading in case we reached the end of a section.
bool read_leb128(uint64_t* result, int8_t check_size, bool is_signed);
public:
MarkedDwarfFileReader(FILE* const fd) : MarkedFileReader(fd), _current_pos(-1), _max_pos(-1) {}
virtual bool set_position(long new_pos);
long get_position() const { return _current_pos; }
void set_max_pos(long max_pos) { _max_pos = max_pos; }
// Have we reached the limit of maximally allowable bytes to read? Used to ensure to stop reading when a section ends.
bool has_bytes_left() const;
// Call this if another file reader has changed the position of the same file handle.
bool update_to_stored_position();
// Must be called to restore the old position before this file reader changed it with update_to_stored_position().
bool reset_to_previous_position();
bool move_position(long offset);
bool read_byte(void* result);
bool read_word(uint16_t* result);
bool read_dword(uint32_t* result);
bool read_qword(uint64_t* result);
bool read_uleb128_ignore(int8_t check_size = -1);
bool read_uleb128(uint64_t* result, int8_t check_size = -1);
bool read_sleb128(int64_t* result, int8_t check_size = -1);
// Reads 4 bytes for 32-bit and 8 bytes for 64-bit builds.
bool read_address_sized(uintptr_t* result);
bool read_string(char* result = nullptr, size_t result_len = 0);
bool read_non_null_char(char* result);
};
// (2) Processing the .debug_aranges section to find the compilation unit which covers offset_in_library.
// This is specified in section 6.1.2 of the DWARF 4 spec.
//
// Structure of .debug_aranges:
// Section Header
// % Table of variable length sets describing the address space covered by a compilation unit
// % Set 1
// ...
// % Set i:
// % Set header
// ...
// debug_info_offset -> offset to compilation unit
// % Series of address range descriptors [beginning_address, range_length]:
// % Descriptor 1
// ...
// % Descriptor j:
// beginning_address <= offset_in_library < beginning_address + range_length?
// => Found the correct set covering offset_in_library. Take debug_info_offset from the set header to get
// to the correct compilation unit in .debug_info.
class DebugAranges {
// The header is defined in section 6.1.2 of the DWARF 4 spec.
struct DebugArangesSetHeader {
// The total length of all of the entries for that set, not including the length field itself.
uint32_t _unit_length;
// This number is specific to the address lookup table and is independent of the DWARF version number.
uint16_t _version;
// The offset from the beginning of the .debug_info or .debug_types section of the compilation unit header referenced
// by the set. In this parser we only use it as offset into .debug_info. This must be 4 bytes for 32-bit DWARF.
uint32_t _debug_info_offset;
// The size of an address in bytes on the target architecture, 4 bytes for 32-bit and 8 bytes for 64-bit Linux builds.
uint8_t _address_size;
// The size of a segment selector in bytes on the target architecture. This should be 0.
uint8_t _segment_size;
};
// Address descriptor defining a range that is covered by a compilation unit. It is defined in section 6.1.2 after
// the set header in the DWARF 4 spec.
struct AddressDescriptor {
uintptr_t beginning_address = 0;
uintptr_t range_length = 0;
};
DwarfFile* _dwarf_file;
MarkedDwarfFileReader _reader;
uint32_t _section_start_address;
// a calculated end position
long _entry_end;
bool read_section_header();
bool read_set_header(DebugArangesSetHeader& header);
bool read_address_descriptors(const DwarfFile::DebugAranges::DebugArangesSetHeader& header,
uint32_t offset_in_library, bool& found_matching_set);
bool read_address_descriptor(AddressDescriptor& descriptor);
static bool does_match_offset(uint32_t offset_in_library, const AddressDescriptor& descriptor) ;
bool is_terminating_entry(const DwarfFile::DebugAranges::DebugArangesSetHeader& header,
const AddressDescriptor& descriptor);
public:
DebugAranges(DwarfFile* dwarf_file) : _dwarf_file(dwarf_file), _reader(dwarf_file->fd()),
_section_start_address(0), _entry_end(0) {}
bool find_compilation_unit_offset(uint32_t offset_in_library, uint32_t* compilation_unit_offset);
};
// (3a-c,e) The compilation unit is read from the .debug_info section. The structure of .debug_info is shown in the
// comments of class DebugAbbrev.
class CompilationUnit {
// Attribute form encodings from Figure 21 in section 7.5 of the DWARF 4 spec.
static constexpr uint8_t DW_FORM_addr = 0x01; // address
static constexpr uint8_t DW_FORM_block2 = 0x03; // block
static constexpr uint8_t DW_FORM_block4 = 0x04; // block
static constexpr uint8_t DW_FORM_data2 = 0x05; // constant
static constexpr uint8_t DW_FORM_data4 = 0x06; // constant
static constexpr uint8_t DW_FORM_data8 = 0x07; // constant
static constexpr uint8_t DW_FORM_string = 0x08; // string
static constexpr uint8_t DW_FORM_block = 0x09; // block
static constexpr uint8_t DW_FORM_block1 = 0x0a; // block
static constexpr uint8_t DW_FORM_data1 = 0x0b; // constant
static constexpr uint8_t DW_FORM_flag = 0x0c; // flag
static constexpr uint8_t DW_FORM_sdata = 0x0d; // constant
static constexpr uint8_t DW_FORM_strp = 0x0e; // string
static constexpr uint8_t DW_FORM_udata = 0x0f; // constant
static constexpr uint8_t DW_FORM_ref_addr = 0x10; // reference0;
static constexpr uint8_t DW_FORM_ref1 = 0x11; // reference
static constexpr uint8_t DW_FORM_ref2 = 0x12; // reference
static constexpr uint8_t DW_FORM_ref4 = 0x13; // reference
static constexpr uint8_t DW_FORM_ref8 = 0x14; // reference
static constexpr uint8_t DW_FORM_ref_udata = 0x15; // reference
static constexpr uint8_t DW_FORM_indirect = 0x16; // see Section 7.5.3
static constexpr uint8_t DW_FORM_sec_offset = 0x17; // lineptr, loclistptr, macptr, rangelistptr
static constexpr uint8_t DW_FORM_exprloc = 0x18;// exprloc
static constexpr uint8_t DW_FORM_flag_present = 0x19; // flag
static constexpr uint8_t DW_FORM_ref_sig8 = 0x20; // reference
// The header is defined in section 7.5.1.1 of the DWARF 4 spec.
struct CompilationUnitHeader {
// The length of the .debug_info contribution for that compilation unit, not including the length field itself.
uint32_t _unit_length;
// The version of the DWARF information for the compilation unit. The value in this field is 4 for DWARF 4.
uint16_t _version;
// The offset into the .debug_abbrev section. This offset associates the compilation unit with a particular set of
// debugging information entry abbreviations.
uint32_t _debug_abbrev_offset;
// The size in bytes of an address on the target architecture, 4 bytes for 32-bit and 8 bytes for 64-bit Linux builds.
uint8_t _address_size;
};
DwarfFile* _dwarf_file;
MarkedDwarfFileReader _reader;
CompilationUnitHeader _header;
const uint32_t _compilation_unit_offset;
// Result of a request initiated by find_debug_line_offset().
uint32_t _debug_line_offset;
bool read_header();
public:
CompilationUnit(DwarfFile* dwarf_file, uint32_t compilation_unit_offset)
: _dwarf_file(dwarf_file), _reader(dwarf_file->fd()), _compilation_unit_offset(compilation_unit_offset), _debug_line_offset(0) {}
bool find_debug_line_offset(uint32_t* debug_line_offset);
bool read_attribute_value(uint64_t attribute_form, bool is_DW_AT_stmt_list_attribute);
};
// (3d) Read from the .debug_abbrev section at the debug_abbrev_offset specified by the compilation unit header.
//
// The interplay between the .debug_info and .debug_abbrev sections is more complex. The following visualization of the structure
// of both sections support the comments found in the parsing steps of the CompilationUnit and DebugAbbrev class.
//
// Structure of .debug_abbrev:
// Section Header
// % Series of abbreviation tables
// % Abbreviation table 1
// ...
// % Abbreviation table for compilation unit at debug_abbrev_offset:
// % Series of declarations:
// % Declaration 1:
// abbreviation code
// tag
// DW_CHILDREN_yes/no
// % Series of attribute specifications
// % Attribute specification 1:
// attribute name
// attribute form
// ...
// % Last attribute specification:
// 0
// 0
// ...
// % Declaration i:
// Abbrev code read from compilation unit [AC]
// DW_TAG_compile_unit
// DW_CHILDREN_yes
// % Series of attribute specifications
// % Attribute specification 1 [AS1]
// ...
// % Attribute specification j [ASj]:
// DW_AT_stmt_list
// DW_FORM_sec_offset
//
//
// Structure of .debug_info:
// Section Header
// % Series of compilation units
// % Compilation unit 1
// ...
// % Compilation unit i for library offset fetched from .debug_aranges:
// % Compilation unit header:
// ...
// debug_abbrev_offset -> offset for abbreviation table in .debug_abbrev for this compilation unit
// ...
// Abbrev code -> used in .debug_abbrev to find the correct declaration [AC]
// % Series of attribute values
// Attribute value 1 (in the format defined by attribute specification 1 [AS1])
// ...
// Attribute value j (in the format defined by attribute specification j [ASj]):
// => Specifies Offset to line number program for this compilation unit in .debug_line
class DebugAbbrev {
struct AbbreviationDeclaration {
uint64_t _abbrev_code;
uint64_t _tag;
uint8_t _has_children;
};
struct AttributeSpecification {
uint64_t _name;
uint64_t _form;
};
// Tag encoding from Figure 18 in section 7.5 of the DWARF 4 spec.
static constexpr uint8_t DW_TAG_compile_unit = 0x11;
// Child determination encoding from Figure 19 in section 7.5 of the DWARF 4 spec.
static constexpr uint8_t DW_CHILDREN_yes = 0x01;
// Attribute encoding from Figure 20 in section 7.5 of the DWARF 4 spec.
static constexpr uint8_t DW_AT_stmt_list = 0x10;
/* There is no specific header for this section */
DwarfFile* _dwarf_file;
MarkedDwarfFileReader _reader;
CompilationUnit* _compilation_unit; // Need to read from compilation unit while parsing the entries in .debug_abbrev.
// Result field of a request
uint32_t* _debug_line_offset;
bool read_declaration(AbbreviationDeclaration& declaration);
static bool is_wrong_or_unsupported_format(const AbbreviationDeclaration& declaration);
bool read_attribute_specifications(bool is_DW_TAG_compile_unit);
bool read_attribute_specification(AttributeSpecification& specification);
static bool is_terminating_specification(const AttributeSpecification& attribute_specification) ;
public:
DebugAbbrev(DwarfFile* dwarf_file, CompilationUnit* compilation_unit) :
_dwarf_file(dwarf_file), _reader(_dwarf_file->fd()), _compilation_unit(compilation_unit),
_debug_line_offset(nullptr) {}
bool read_section_header(uint32_t debug_abbrev_offset);
bool find_debug_line_offset(uint64_t abbrev_code);
};
// (4) The line number program for the compilation unit at the offset of the .debug_line obtained by (3).
// For some reason, earlier GCC versions emit the line number program in DWARF 2 or 3 format even though the
// default is DWARF 4. It also mixes the standards (see comments in the parsing code).
//
// Therefore, this class supports DWARF 2, 3 and 4 parsing as specified in section 6.2 of the DWARF specs.
// The parsing of DWARF 2 is already covered by the parsing of DWARF 3 as they use the shared opcodes in the same way.
// The parsing of DWARF 4, however, needs some adaptation as it consumes more data for some shared opcodes.
//
// DWARF 2 standard: https://dwarfstd.org/doc/dwarf-2.0.0.pdf
// DWARF 3 standard: https://dwarfstd.org/doc/Dwarf3.pdf
//
//
// Structure of .debug_ling:
// Section Header
// % Series of line number program entries for each compilation unit
// % Line number program 1
// ...
// % Line number program i for our compilation unit:
// % Line program header unit header:
// ...
// version -> currently emits version 3 by default
// ...
// file_name -> sequence of file names
// % Sequence of opcodes as part of the line number program to build the line number information matrix:
// % Format of matrix: [offset, line, directory_index, file_index]
// % Line 1
// ...
// % Line j:
// [offset matching offset_in_library, line, directory_index, file_index]
// => Get line number + look up file_index in file_name list (pick file_index'th string)
class LineNumberProgram {
// Standard opcodes for the line number program defined in section 6.2.5.2 of the DWARF 4 spec.
static constexpr uint8_t DW_LNS_copy = 1;
static constexpr uint8_t DW_LNS_advance_pc = 2;
static constexpr uint8_t DW_LNS_advance_line = 3;
static constexpr uint8_t DW_LNS_set_file = 4;
static constexpr uint8_t DW_LNS_set_column = 5;
static constexpr uint8_t DW_LNS_negate_stmt = 6;
static constexpr uint8_t DW_LNS_set_basic_block = 7;
static constexpr uint8_t DW_LNS_const_add_pc = 8;
static constexpr uint8_t DW_LNS_fixed_advance_pc = 9;
static constexpr uint8_t DW_LNS_set_prologue_end = 10; // Introduced with DWARF 3
static constexpr uint8_t DW_LNS_set_epilogue_begin = 11; // Introduced with DWARF 3
static constexpr uint8_t DW_LNS_set_isa = 12; // Introduced with DWARF 3
// Extended opcodes for the line number program defined in section 6.2.5.2 of the DWARF 4 spec.
static constexpr uint8_t DW_LNE_end_sequence = 1;
static constexpr uint8_t DW_LNE_set_address = 2;
static constexpr uint8_t DW_LNE_define_file = 3;
static constexpr uint8_t DW_LNE_set_discriminator = 4; // Introduced with DWARF 4
static constexpr const char* overflow_filename = "<OVERFLOW>";
static constexpr const char minimal_overflow_filename = 'L';
// The header is defined in section 6.2.4 of the DWARF 4 spec.
struct LineNumberProgramHeader {
// The size in bytes of the line number information for this compilation unit, not including the unit_length
// field itself. 32-bit DWARF uses 4 bytes.
uint32_t _unit_length;
// The version of the DWARF information for the line number program unit. The value in this field should be 4 for
// DWARF 4 and version 3 as used for DWARF 3.
uint16_t _version;
// The number of bytes following the header_length field to the beginning of the first byte of the line number
// program itself. 32-bit DWARF uses 4 bytes.
uint32_t _header_length;
// The size in bytes of the smallest target machine instruction. Line number program opcodes that alter the address
// and op_index registers use this and maximum_operations_per_instruction in their calculations.
uint8_t _minimum_instruction_length;
// The maximum number of individual operations that may be encoded in an instruction. Line number program opcodes
// that alter the address and op_index registers use this and minimum_instruction_length in their calculations.
// For non-VLIW architectures, this field is 1, the op_index register is always 0, and the operation pointer is
// simply the address register. This is only used with DWARF 4.
uint8_t _maximum_operations_per_instruction;
// The initial value of the is_stmt register.
uint8_t _default_is_stmt;
// This parameter affects the meaning of the special opcodes.
int8_t _line_base;
// This parameter affects the meaning of the special opcodes.
uint8_t _line_range;
// The number assigned to the first special opcode.
uint8_t _opcode_base;
// This array specifies the number of LEB128 operands for each of the standard opcodes. The first element of the
// array corresponds to the opcode whose value is 1, and the last element corresponds to the opcode whose value is
// opcode_base-1. DWARF 2 uses 9 standard opcodes while DWARF 3 and 4 use 12.
uint8_t _standard_opcode_lengths[12];
/*
* The following fields are not part of the real header and are only used for the implementation.
*/
// Offset where the filename strings are starting in header.
long _file_names_offset;
// _header_length only specifies the number of bytes following the _header_length field. It does not include
// the size of _unit_length, _version and _header_length itself. This constant represents the number of missing
// bytes to get the real size of the header:
// sizeof(_unit_length) + sizeof(_version) + sizeof(_header_length) = 4 + 2 + 4 = 10
static constexpr uint8_t HEADER_DESCRIPTION_BYTES = 10;
};
// The line number program state consists of several registers that hold the current state of the line number program
// state machine. The state/different state registers are defined in section 6.2.2 of the DWARF 4 spec. Most of these
// fields (state registers) are not used to get the filename and the line number information.
struct LineNumberProgramState : public CHeapObj<mtInternal> {
// The program-counter value corresponding to a machine instruction generated by the compiler.
// 4 bytes on 32-bit and 8 bytes on 64-bit.
uintptr_t _address;
// The index of an operation within a VLIW instruction. The index of the first operation is 0. For non-VLIW
// architectures, this register will always be 0.
// The address and op_index registers, taken together, form an operation pointer that can reference any
// individual operation with the instruction stream. This field was introduced with DWARF 4.
uint32_t _op_index;
// The identity of the source file corresponding to a machine instruction.
uint32_t _file;
// A source line number. Lines are numbered beginning at 1. The compiler may emit the value 0 in cases where an
// instruction cannot be attributed to any source line.
uint32_t _line;
// A column number within a source line. Columns are numbered beginning at 1. The value 0 is reserved to indicate
// that a statement begins at the "left edge" of the line.
uint32_t _column;
// Indicates that the current instruction is a recommended breakpoint location.
bool _is_stmt;
// Indicates that the current instruction is the beginning of a basic block.
bool _basic_block;
// Indicates that the current address is that of the first byte after the end of a sequence of target machine
// instructions. end_sequence terminates a sequence of lines.
bool _end_sequence;
// Indicates that the current address is one (of possibly many) where execution should be suspended for an entry
// breakpoint of a function. This field was introduced with DWARF 3.
bool _prologue_end;
// Indicates that the current address is one (of possibly many) where execution should be suspended for an exit
// breakpoint of a function. This field was introduced with DWARF 3.
bool _epilogue_begin;
// Encodes the applicable instruction set architecture for the current instruction.
// This field was introduced with DWARF 3.
uint32_t _isa;
// Identifies the block to which the current instruction belongs. This field was introduced with DWARF 4.
uint32_t _discriminator;
/*
* Additional fields which are not part of the actual state as described in DWARF spec.
*/
// Header fields
// Specifies which DWARF version is used in the .debug_line section. Supported version: DWARF 2, 3, and 4.
const uint16_t _dwarf_version;
const bool _initial_is_stmt;
// Implementation specific fields
bool _append_row;
bool _do_reset;
bool _first_entry_in_sequence;
bool _can_sequence_match_offset;
bool _found_match;
LineNumberProgramState(const LineNumberProgramHeader& header)
: _is_stmt(header._default_is_stmt != 0), _dwarf_version(header._version),
_initial_is_stmt(header._default_is_stmt != 0), _found_match(false) {
reset_fields();
}
void reset_fields();
// Defined in section 6.2.5.1 of the DWARF spec 4. add_to_address_register() must always be executed before set_index_register.
void add_to_address_register(uint32_t operation_advance, const LineNumberProgramHeader& header);
void set_index_register(uint32_t operation_advance, const LineNumberProgramHeader& header);
};
DwarfFile* _dwarf_file;
MarkedDwarfFileReader _reader;
LineNumberProgramHeader _header;
LineNumberProgramState* _state;
const uint32_t _offset_in_library;
const uint64_t _debug_line_offset;
bool _is_pc_after_call;
bool read_header();
bool run_line_number_program(char* filename, size_t filename_len, int* line);
bool apply_opcode();
bool apply_extended_opcode();
bool apply_standard_opcode(uint8_t opcode);
void apply_special_opcode(uint8_t opcode);
bool does_offset_match_entry(uintptr_t previous_address, uint32_t previous_file, uint32_t previous_line);
void print_and_store_prev_entry(uint32_t previous_file, uint32_t previous_line);
bool get_filename_from_header(uint32_t file_index, char* filename, size_t filename_len);
bool read_filename(char* filename, size_t filename_len);
static void write_filename_for_overflow(char* filename, size_t filename_len) ;
public:
LineNumberProgram(DwarfFile* dwarf_file, uint32_t offset_in_library, uint64_t debug_line_offset, bool is_pc_after_call)
: _dwarf_file(dwarf_file), _reader(dwarf_file->fd()), _offset_in_library(offset_in_library),
_debug_line_offset(debug_line_offset), _is_pc_after_call(is_pc_after_call) {}
~LineNumberProgram() { delete _state; }
bool find_filename_and_line_number(char* filename, size_t filename_len, int* line);
};
public:
DwarfFile(const char* filepath) : ElfFile(filepath) {}
/*
* Starting point of reading line number and filename information from the DWARF file.
*
* Given: Offset into the ELF library file, a filename buffer of size filename_size, a line number pointer.
* Return: True: The filename is set in the 'filename' buffer and the line number at the address pointed to by 'line'.
* False: Something went wrong either while reading from the file or during parsing due to an unexpected format.
* This could happen if the DWARF file is in an unsupported or wrong format.
*
* More details about the different phases can be found at the associated methods.
*/
bool get_filename_and_line_number(uint32_t offset_in_library, char* filename, size_t filename_len, int* line, bool is_pc_after_call);
};
#endif // !_WINDOWS && !__APPLE__
#endif // SHARE_UTILITIES_ELFFILE_HPP