| # SPDX-License-Identifier: GPL-2.0+ |
| # Copyright (c) 2016 Google, Inc |
| # Written by Simon Glass <sjg@chromium.org> |
| # |
| # Handle various things related to ELF images |
| # |
| |
| from collections import namedtuple, OrderedDict |
| import io |
| import os |
| import re |
| import shutil |
| import struct |
| import tempfile |
| |
| from u_boot_pylib import command |
| from u_boot_pylib import tools |
| from u_boot_pylib import tout |
| |
| ELF_TOOLS = True |
| try: |
| from elftools.elf.elffile import ELFFile |
| from elftools.elf.elffile import ELFError |
| from elftools.elf.sections import SymbolTableSection |
| except: # pragma: no cover |
| ELF_TOOLS = False |
| |
| # BSYM in little endian, keep in sync with include/binman_sym.h |
| BINMAN_SYM_MAGIC_VALUE = 0x4d595342 |
| |
| # Information about an EFL symbol: |
| # section (str): Name of the section containing this symbol |
| # address (int): Address of the symbol (its value) |
| # size (int): Size of the symbol in bytes |
| # weak (bool): True if the symbol is weak |
| # offset (int or None): Offset of the symbol's data in the ELF file, or None if |
| # not known |
| Symbol = namedtuple('Symbol', ['section', 'address', 'size', 'weak', 'offset']) |
| |
| # Information about an ELF file: |
| # data: Extracted program contents of ELF file (this would be loaded by an |
| # ELF loader when reading this file |
| # load: Load address of code |
| # entry: Entry address of code |
| # memsize: Number of bytes in memory occupied by loading this ELF file |
| ElfInfo = namedtuple('ElfInfo', ['data', 'load', 'entry', 'memsize']) |
| |
| |
| def GetSymbols(fname, patterns): |
| """Get the symbols from an ELF file |
| |
| Args: |
| fname: Filename of the ELF file to read |
| patterns: List of regex patterns to search for, each a string |
| |
| Returns: |
| None, if the file does not exist, or Dict: |
| key: Name of symbol |
| value: Hex value of symbol |
| """ |
| stdout = tools.run('objdump', '-t', fname) |
| lines = stdout.splitlines() |
| if patterns: |
| re_syms = re.compile('|'.join(patterns)) |
| else: |
| re_syms = None |
| syms = {} |
| syms_started = False |
| for line in lines: |
| if not line or not syms_started: |
| if 'SYMBOL TABLE' in line: |
| syms_started = True |
| line = None # Otherwise code coverage complains about 'continue' |
| continue |
| if re_syms and not re_syms.search(line): |
| continue |
| |
| space_pos = line.find(' ') |
| value, rest = line[:space_pos], line[space_pos + 1:] |
| flags = rest[:7] |
| parts = rest[7:].split() |
| section, size = parts[:2] |
| if len(parts) > 2: |
| name = parts[2] if parts[2] != '.hidden' else parts[3] |
| syms[name] = Symbol(section, int(value, 16), int(size, 16), |
| flags[1] == 'w', None) |
| |
| # Sort dict by address |
| return OrderedDict(sorted(syms.items(), key=lambda x: x[1].address)) |
| |
| def _GetFileOffset(elf, addr): |
| """Get the file offset for an address |
| |
| Args: |
| elf (ELFFile): ELF file to check |
| addr (int): Address to search for |
| |
| Returns |
| int: Offset of that address in the ELF file, or None if not valid |
| """ |
| for seg in elf.iter_segments(): |
| seg_end = seg['p_vaddr'] + seg['p_filesz'] |
| if seg.header['p_type'] == 'PT_LOAD': |
| if addr >= seg['p_vaddr'] and addr < seg_end: |
| return addr - seg['p_vaddr'] + seg['p_offset'] |
| |
| def GetFileOffset(fname, addr): |
| """Get the file offset for an address |
| |
| Args: |
| fname (str): Filename of ELF file to check |
| addr (int): Address to search for |
| |
| Returns |
| int: Offset of that address in the ELF file, or None if not valid |
| """ |
| if not ELF_TOOLS: |
| raise ValueError("Python: No module named 'elftools'") |
| with open(fname, 'rb') as fd: |
| elf = ELFFile(fd) |
| return _GetFileOffset(elf, addr) |
| |
| def GetSymbolFromAddress(fname, addr): |
| """Get the symbol at a particular address |
| |
| Args: |
| fname (str): Filename of ELF file to check |
| addr (int): Address to search for |
| |
| Returns: |
| str: Symbol name, or None if no symbol at that address |
| """ |
| if not ELF_TOOLS: |
| raise ValueError("Python: No module named 'elftools'") |
| with open(fname, 'rb') as fd: |
| elf = ELFFile(fd) |
| syms = GetSymbols(fname, None) |
| for name, sym in syms.items(): |
| if sym.address == addr: |
| return name |
| |
| def GetSymbolFileOffset(fname, patterns): |
| """Get the symbols from an ELF file |
| |
| Args: |
| fname: Filename of the ELF file to read |
| patterns: List of regex patterns to search for, each a string |
| |
| Returns: |
| None, if the file does not exist, or Dict: |
| key: Name of symbol |
| value: Hex value of symbol |
| """ |
| if not ELF_TOOLS: |
| raise ValueError("Python: No module named 'elftools'") |
| |
| syms = {} |
| with open(fname, 'rb') as fd: |
| elf = ELFFile(fd) |
| |
| re_syms = re.compile('|'.join(patterns)) |
| for section in elf.iter_sections(): |
| if isinstance(section, SymbolTableSection): |
| for symbol in section.iter_symbols(): |
| if not re_syms or re_syms.search(symbol.name): |
| addr = symbol.entry['st_value'] |
| syms[symbol.name] = Symbol( |
| section.name, addr, symbol.entry['st_size'], |
| symbol.entry['st_info']['bind'] == 'STB_WEAK', |
| _GetFileOffset(elf, addr)) |
| |
| # Sort dict by address |
| return OrderedDict(sorted(syms.items(), key=lambda x: x[1].address)) |
| |
| def GetSymbolAddress(fname, sym_name): |
| """Get a value of a symbol from an ELF file |
| |
| Args: |
| fname: Filename of the ELF file to read |
| patterns: List of regex patterns to search for, each a string |
| |
| Returns: |
| Symbol value (as an integer) or None if not found |
| """ |
| syms = GetSymbols(fname, [sym_name]) |
| sym = syms.get(sym_name) |
| if not sym: |
| return None |
| return sym.address |
| |
| def GetPackString(sym, msg): |
| """Get the struct.pack/unpack string to use with a given symbol |
| |
| Args: |
| sym (Symbol): Symbol to check. Only the size member is checked |
| @msg (str): String which indicates the entry being processed, used for |
| errors |
| |
| Returns: |
| str: struct string to use, .e.g. '<I' |
| |
| Raises: |
| ValueError: Symbol has an unexpected size |
| """ |
| if sym.size == 4: |
| return '<I' |
| elif sym.size == 8: |
| return '<Q' |
| else: |
| raise ValueError('%s has size %d: only 4 and 8 are supported' % |
| (msg, sym.size)) |
| |
| def GetSymbolOffset(elf_fname, sym_name, base_sym=None): |
| """Read the offset of a symbol compared to base symbol |
| |
| This is useful for obtaining the value of a single symbol relative to the |
| base of a binary blob. |
| |
| Args: |
| elf_fname: Filename of the ELF file to read |
| sym_name (str): Name of symbol to read |
| base_sym (str): Base symbol to sue to calculate the offset (or None to |
| use '__image_copy_start' |
| |
| Returns: |
| int: Offset of the symbol relative to the base symbol |
| """ |
| if not base_sym: |
| base_sym = '__image_copy_start' |
| fname = tools.get_input_filename(elf_fname) |
| syms = GetSymbols(fname, [base_sym, sym_name]) |
| base = syms[base_sym].address |
| val = syms[sym_name].address |
| return val - base |
| |
| def LookupAndWriteSymbols(elf_fname, entry, section, is_elf=False, |
| base_sym=None, base_addr=None): |
| """Replace all symbols in an entry with their correct values |
| |
| The entry contents is updated so that values for referenced symbols will be |
| visible at run time. This is done by finding out the symbols offsets in the |
| entry (using the ELF file) and replacing them with values from binman's data |
| structures. |
| |
| Args: |
| elf_fname: Filename of ELF image containing the symbol information for |
| entry |
| entry: Entry to process |
| section: Section which can be used to lookup symbol values |
| base_sym: Base symbol marking the start of the image (__image_copy_start |
| by default) |
| base_addr (int): Base address to use for the entry being written. If |
| None then the value of base_sym is used |
| |
| Returns: |
| int: Number of symbols written |
| """ |
| if not base_sym: |
| base_sym = '__image_copy_start' |
| fname = tools.get_input_filename(elf_fname) |
| syms = GetSymbols(fname, ['image', 'binman']) |
| if is_elf: |
| if not ELF_TOOLS: |
| msg = ("Section '%s': entry '%s'" % |
| (section.GetPath(), entry.GetPath())) |
| raise ValueError(f'{msg}: Cannot write symbols to an ELF file without Python elftools') |
| new_syms = {} |
| with open(fname, 'rb') as fd: |
| elf = ELFFile(fd) |
| for name, sym in syms.items(): |
| offset = _GetFileOffset(elf, sym.address) |
| new_syms[name] = Symbol(sym.section, sym.address, sym.size, |
| sym.weak, offset) |
| syms = new_syms |
| |
| if not syms: |
| tout.debug('LookupAndWriteSymbols: no syms') |
| return 0 |
| base = syms.get(base_sym) |
| if not base and not is_elf: |
| tout.debug(f'LookupAndWriteSymbols: no base: elf_fname={elf_fname}, base_sym={base_sym}, is_elf={is_elf}') |
| return 0 |
| if base_addr is None: |
| base_addr = 0 if is_elf else base.address |
| count = 0 |
| for name, sym in syms.items(): |
| if name.startswith('_binman'): |
| msg = ("Section '%s': Symbol '%s'\n in entry '%s'" % |
| (section.GetPath(), name, entry.GetPath())) |
| if is_elf: |
| # For ELF files, use the file offset |
| offset = sym.offset |
| else: |
| # For blobs use the offset of the symbol, calculated by |
| # subtracting the base address which by definition is at the |
| # start |
| offset = sym.address - base.address |
| if offset < 0 or offset + sym.size > entry.contents_size: |
| raise ValueError('%s has offset %x (size %x) but the contents ' |
| 'size is %x' % (entry.GetPath(), offset, |
| sym.size, |
| entry.contents_size)) |
| pack_string = GetPackString(sym, msg) |
| if name == '_binman_sym_magic': |
| value = BINMAN_SYM_MAGIC_VALUE |
| else: |
| # Look up the symbol in our entry tables. |
| value = section.GetImage().GetImageSymbolValue(name, sym.weak, |
| msg, base_addr) |
| if value is None: |
| value = -1 |
| pack_string = pack_string.lower() |
| value_bytes = struct.pack(pack_string, value) |
| tout.debug('%s:\n insert %s, offset %x, value %x, length %d' % |
| (msg, name, offset, value, len(value_bytes))) |
| entry.data = (entry.data[:offset] + value_bytes + |
| entry.data[offset + sym.size:]) |
| count += 1 |
| if count: |
| tout.detail( |
| f"Section '{section.GetPath()}': entry '{entry.GetPath()}' : {count} symbols") |
| return count |
| |
| def GetSymbolValue(sym, data, msg): |
| """Get the value of a symbol |
| |
| This can only be used on symbols with an integer value. |
| |
| Args: |
| sym (Symbol): Symbol to check |
| data (butes): Data for the ELF file - the symbol data appears at offset |
| sym.offset |
| @msg (str): String which indicates the entry being processed, used for |
| errors |
| |
| Returns: |
| int: Value of the symbol |
| |
| Raises: |
| ValueError: Symbol has an unexpected size |
| """ |
| pack_string = GetPackString(sym, msg) |
| value = struct.unpack(pack_string, data[sym.offset:sym.offset + sym.size]) |
| return value[0] |
| |
| def MakeElf(elf_fname, text, data): |
| """Make an elf file with the given data in a single section |
| |
| The output file has a several section including '.text' and '.data', |
| containing the info provided in arguments. |
| |
| Args: |
| elf_fname: Output filename |
| text: Text (code) to put in the file's .text section |
| data: Data to put in the file's .data section |
| """ |
| outdir = tempfile.mkdtemp(prefix='binman.elf.') |
| s_file = os.path.join(outdir, 'elf.S') |
| |
| # Spilt the text into two parts so that we can make the entry point two |
| # bytes after the start of the text section |
| text_bytes1 = ['\t.byte\t%#x' % byte for byte in text[:2]] |
| text_bytes2 = ['\t.byte\t%#x' % byte for byte in text[2:]] |
| data_bytes = ['\t.byte\t%#x' % byte for byte in data] |
| with open(s_file, 'w') as fd: |
| print('''/* Auto-generated C program to produce an ELF file for testing */ |
| |
| .section .text |
| .code32 |
| .globl _start |
| .type _start, @function |
| %s |
| _start: |
| %s |
| .ident "comment" |
| |
| .comm fred,8,4 |
| |
| .section .empty |
| .globl _empty |
| _empty: |
| .byte 1 |
| |
| .globl ernie |
| .data |
| .type ernie, @object |
| .size ernie, 4 |
| ernie: |
| %s |
| ''' % ('\n'.join(text_bytes1), '\n'.join(text_bytes2), '\n'.join(data_bytes)), |
| file=fd) |
| lds_file = os.path.join(outdir, 'elf.lds') |
| |
| # Use a linker script to set the alignment and text address. |
| with open(lds_file, 'w') as fd: |
| print('''/* Auto-generated linker script to produce an ELF file for testing */ |
| |
| PHDRS |
| { |
| text PT_LOAD ; |
| data PT_LOAD ; |
| empty PT_LOAD FLAGS ( 6 ) ; |
| note PT_NOTE ; |
| } |
| |
| SECTIONS |
| { |
| . = 0xfef20000; |
| ENTRY(_start) |
| .text . : SUBALIGN(0) |
| { |
| *(.text) |
| } :text |
| .data : { |
| *(.data) |
| } :data |
| _bss_start = .; |
| .empty : { |
| *(.empty) |
| } :empty |
| /DISCARD/ : { |
| *(.note.gnu.property) |
| } |
| .note : { |
| *(.comment) |
| } :note |
| .bss _bss_start (OVERLAY) : { |
| *(.bss) |
| } |
| } |
| ''', file=fd) |
| # -static: Avoid requiring any shared libraries |
| # -nostdlib: Don't link with C library |
| # -Wl,--build-id=none: Don't generate a build ID, so that we just get the |
| # text section at the start |
| # -m32: Build for 32-bit x86 |
| # -T...: Specifies the link script, which sets the start address |
| cc, args = tools.get_target_compile_tool('cc') |
| args += ['-static', '-nostdlib', '-Wl,--build-id=none', '-m32', '-T', |
| lds_file, '-o', elf_fname, s_file] |
| stdout = command.output(cc, *args) |
| shutil.rmtree(outdir) |
| |
| def DecodeElf(data, location): |
| """Decode an ELF file and return information about it |
| |
| Args: |
| data: Data from ELF file |
| location: Start address of data to return |
| |
| Returns: |
| ElfInfo object containing information about the decoded ELF file |
| """ |
| if not ELF_TOOLS: |
| raise ValueError("Python: No module named 'elftools'") |
| file_size = len(data) |
| with io.BytesIO(data) as fd: |
| elf = ELFFile(fd) |
| data_start = 0xffffffff |
| data_end = 0 |
| mem_end = 0 |
| virt_to_phys = 0 |
| |
| for i in range(elf.num_segments()): |
| segment = elf.get_segment(i) |
| if segment['p_type'] != 'PT_LOAD' or not segment['p_memsz']: |
| skipped = 1 # To make code-coverage see this line |
| continue |
| start = segment['p_paddr'] |
| mend = start + segment['p_memsz'] |
| rend = start + segment['p_filesz'] |
| data_start = min(data_start, start) |
| data_end = max(data_end, rend) |
| mem_end = max(mem_end, mend) |
| if not virt_to_phys: |
| virt_to_phys = segment['p_paddr'] - segment['p_vaddr'] |
| |
| output = bytearray(data_end - data_start) |
| for i in range(elf.num_segments()): |
| segment = elf.get_segment(i) |
| if segment['p_type'] != 'PT_LOAD' or not segment['p_memsz']: |
| skipped = 1 # To make code-coverage see this line |
| continue |
| start = segment['p_paddr'] |
| offset = 0 |
| if start < location: |
| offset = location - start |
| start = location |
| # A legal ELF file can have a program header with non-zero length |
| # but zero-length file size and a non-zero offset which, added |
| # together, are greater than input->size (i.e. the total file size). |
| # So we need to not even test in the case that p_filesz is zero. |
| # Note: All of this code is commented out since we don't have a test |
| # case for it. |
| size = segment['p_filesz'] |
| #if not size: |
| #continue |
| #end = segment['p_offset'] + segment['p_filesz'] |
| #if end > file_size: |
| #raise ValueError('Underflow copying out the segment. File has %#x bytes left, segment end is %#x\n', |
| #file_size, end) |
| output[start - data_start:start - data_start + size] = ( |
| segment.data()[offset:]) |
| return ElfInfo(output, data_start, elf.header['e_entry'] + virt_to_phys, |
| mem_end - data_start) |
| |
| def UpdateFile(infile, outfile, start_sym, end_sym, insert): |
| tout.notice("Creating file '%s' with data length %#x (%d) between symbols '%s' and '%s'" % |
| (outfile, len(insert), len(insert), start_sym, end_sym)) |
| syms = GetSymbolFileOffset(infile, [start_sym, end_sym]) |
| if len(syms) != 2: |
| raise ValueError("Expected two symbols '%s' and '%s': got %d: %s" % |
| (start_sym, end_sym, len(syms), |
| ','.join(syms.keys()))) |
| |
| size = syms[end_sym].offset - syms[start_sym].offset |
| if len(insert) > size: |
| raise ValueError("Not enough space in '%s' for data length %#x (%d); size is %#x (%d)" % |
| (infile, len(insert), len(insert), size, size)) |
| |
| data = tools.read_file(infile) |
| newdata = data[:syms[start_sym].offset] |
| newdata += insert + tools.get_bytes(0, size - len(insert)) |
| newdata += data[syms[end_sym].offset:] |
| tools.write_file(outfile, newdata) |
| tout.info('Written to offset %#x' % syms[start_sym].offset) |
| |
| def read_loadable_segments(data): |
| """Read segments from an ELF file |
| |
| Args: |
| data (bytes): Contents of file |
| |
| Returns: |
| tuple: |
| list of segments, each: |
| int: Segment number (0 = first) |
| int: Start address of segment in memory |
| bytes: Contents of segment |
| int: entry address for image |
| |
| Raises: |
| ValueError: elftools is not available |
| """ |
| if not ELF_TOOLS: |
| raise ValueError("Python: No module named 'elftools'") |
| with io.BytesIO(data) as inf: |
| try: |
| elf = ELFFile(inf) |
| except ELFError as err: |
| raise ValueError(err) |
| entry = elf.header['e_entry'] |
| segments = [] |
| for i in range(elf.num_segments()): |
| segment = elf.get_segment(i) |
| if segment['p_type'] != 'PT_LOAD' or not segment['p_memsz']: |
| skipped = 1 # To make code-coverage see this line |
| continue |
| start = segment['p_offset'] |
| rend = start + segment['p_filesz'] |
| segments.append((i, segment['p_paddr'], data[start:rend])) |
| return segments, entry |
| |
| def is_valid(data): |
| """Check if some binary data is a valid ELF file |
| |
| Args: |
| data (bytes): Bytes to check |
| |
| Returns: |
| bool: True if a valid Elf file, False if not |
| """ |
| try: |
| DecodeElf(data, 0) |
| return True |
| except ELFError: |
| return False |