916 lines
32 KiB
Python
916 lines
32 KiB
Python
#!/usr/bin/python3
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# ELF support functionality for Python.
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# Copyright (C) 2022 Free Software Foundation, Inc.
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# This file is part of the GNU C Library.
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#
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# The GNU C Library is free software; you can redistribute it and/or
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# modify it under the terms of the GNU Lesser General Public
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# License as published by the Free Software Foundation; either
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# version 2.1 of the License, or (at your option) any later version.
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#
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# The GNU C Library is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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# Lesser General Public License for more details.
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#
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# You should have received a copy of the GNU Lesser General Public
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# License along with the GNU C Library; if not, see
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# <https://www.gnu.org/licenses/>.
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"""Basic ELF parser.
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Use Image.readfile(path) to read an ELF file into memory and begin
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parsing it.
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"""
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import collections
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import functools
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import os
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import struct
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import glibcpp
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class _MetaNamedValue(type):
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"""Used to set up _NamedValue subclasses."""
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@classmethod
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def __prepare__(metacls, cls, bases, **kwds):
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# Indicates an int-based class. Needed for types like Shn.
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int_based = False
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for base in bases:
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if issubclass(base, int):
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int_based = int
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break
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return dict(by_value={},
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by_name={},
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prefix=None,
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_int_based=int_based)
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def __contains__(self, other):
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return other in self.by_value
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class _NamedValue(metaclass=_MetaNamedValue):
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"""Typed, named integer constants.
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Constants have the following instance attributes:
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name: The full name of the constant (e.g., "PT_NULL").
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short_name: The name with of the constant without the prefix ("NULL").
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value: The integer value of the constant.
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The following class attributes are available:
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by_value: A dict mapping integers to constants.
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by_name: A dict mapping strings to constants.
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prefix: A string that is removed from the start of short names, or None.
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"""
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def __new__(cls, arg0, arg1=None):
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"""Instance creation.
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For the one-argument form, the argument must be a string, an
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int, or an instance of this class. Strings are looked up via
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by_name. Values are looked up via by_value; if value lookup
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fails, a new unnamed instance is returned. Instances of this
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class a re returned as-is.
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The two-argument form expects the name (a string) and the
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value (an integer). A new instance is created in this case.
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The instance is not registered in the by_value/by_name
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dictionaries (but the caller can do that).
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"""
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typ0 = type(arg0)
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if arg1 is None:
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if isinstance(typ0, cls):
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# Re-use the existing object.
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return arg0
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if typ0 is int:
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by_value = cls.by_value
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try:
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return by_value[arg0]
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except KeyError:
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# Create a new object of the requested value.
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if cls._int_based:
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result = int.__new__(cls, arg0)
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else:
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result = object.__new__(cls)
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result.value = arg0
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result.name = None
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return result
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if typ0 is str:
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by_name = cls.by_name
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try:
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return by_name[arg0]
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except KeyError:
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raise ValueError('unknown {} constant: {!r}'.format(
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cls.__name__, arg0))
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else:
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# Types for the two-argument form are rigid.
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if typ0 is not str and typ0 is not None:
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raise ValueError('type {} of name {!r} should be str'.format(
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typ0.__name__, arg0))
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if type(arg1) is not int:
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raise ValueError('type {} of value {!r} should be int'.format(
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type(arg1).__name__, arg1))
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# Create a new named constants.
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if cls._int_based:
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result = int.__new__(cls, arg1)
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else:
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result = object.__new__(cls)
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result.value = arg1
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result.name = arg0
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# Set up the short_name attribute.
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prefix = cls.prefix
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if prefix and arg0.startswith(prefix):
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result.short_name = arg0[len(prefix):]
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else:
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result.short_name = arg0
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return result
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def __str__(self):
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name = self.name
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if name:
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return name
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else:
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return str(self.value)
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def __repr__(self):
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name = self.name
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if name:
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return name
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else:
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return '{}({})'.format(self.__class__.__name__, self.value)
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def __setattr__(self, name, value):
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# Prevent modification of the critical attributes once they
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# have been set.
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if name in ('name', 'value', 'short_name') and hasattr(self, name):
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raise AttributeError('can\'t set attribute {}'.format(name))
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object.__setattr__(self, name, value)
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@functools.total_ordering
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class _TypedConstant(_NamedValue):
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"""Base class for integer-valued optionally named constants.
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This type is not an integer type.
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"""
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def __eq__(self, other):
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return isinstance(other, self.__class__) and self.value == other.value
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def __lt__(self, other):
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return isinstance(other, self.__class__) and self.value <= other.value
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def __hash__(self):
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return hash(self.value)
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class _IntConstant(_NamedValue, int):
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"""Base class for integer-like optionally named constants.
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Instances compare equal to the integer of the same value, and can
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be used in integer arithmetic.
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"""
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pass
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class _FlagConstant(_TypedConstant, int):
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pass
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def _parse_elf_h():
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"""Read ../elf/elf.h and return a dict with the constants in it."""
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path = os.path.join(os.path.dirname(os.path.realpath(__file__)),
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'..', 'elf', 'elf.h')
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class TokenizerReporter:
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"""Report tokenizer errors to standard output."""
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def __init__(self):
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self.errors = 0
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def error(self, token, message):
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self.errors += 1
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print('{}:{}:{}: error: {}'.format(
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path, token.line, token.column, message))
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reporter = TokenizerReporter()
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with open(path) as inp:
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tokens = glibcpp.tokenize_c(inp.read(), reporter)
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if reporter.errors:
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raise IOError('parse error in elf.h')
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class MacroReporter:
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"""Report macro errors to standard output."""
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def __init__(self):
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self.errors = 0
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def error(self, line, message):
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errors += 1
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print('{}:{}: error: {}'.format(path, line, message))
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def note(self, line, message):
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print('{}:{}: note: {}'.format(path, line, message))
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reporter = MacroReporter()
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result = glibcpp.macro_eval(glibcpp.macro_definitions(tokens), reporter)
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if reporter.errors:
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raise IOError('parse error in elf.h')
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return result
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_elf_h = _parse_elf_h()
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del _parse_elf_h
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_elf_h_processed = set()
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def _register_elf_h(cls, prefix=None, skip=(), ranges=False, parent=None):
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prefix = prefix or cls.prefix
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if not prefix:
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raise ValueError('missing prefix for {}'.format(cls.__name__))
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by_value = cls.by_value
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by_name = cls.by_name
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processed = _elf_h_processed
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skip = set(skip)
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skip.add(prefix + 'NUM')
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if ranges:
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skip.add(prefix + 'LOOS')
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skip.add(prefix + 'HIOS')
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skip.add(prefix + 'LOPROC')
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skip.add(prefix + 'HIPROC')
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cls.os_range = (_elf_h[prefix + 'LOOS'], _elf_h[prefix + 'HIOS'])
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cls.proc_range = (_elf_h[prefix + 'LOPROC'], _elf_h[prefix + 'HIPROC'])
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# Inherit the prefix from the parent if not set.
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if parent and cls.prefix is None and parent.prefix is not None:
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cls.prefix = parent.prefix
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processed_len_start = len(processed)
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for name, value in _elf_h.items():
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if name in skip or name in processed:
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continue
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if name.startswith(prefix):
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processed.add(name)
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if value in by_value:
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raise ValueError('duplicate value {}: {}, {}'.format(
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value, name, by_value[value]))
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obj = cls(name, value)
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by_value[value] = obj
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by_name[name] = obj
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setattr(cls, name, obj)
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if parent:
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# Make the symbolic name available through the parent as well.
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parent.by_name[name] = obj
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setattr(parent, name, obj)
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if len(processed) == processed_len_start:
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raise ValueError('nothing matched prefix {!r}'.format(prefix))
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class ElfClass(_TypedConstant):
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"""ELF word size. Type of EI_CLASS values."""
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_register_elf_h(ElfClass, prefix='ELFCLASS')
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class ElfData(_TypedConstant):
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"""ELF endianess. Type of EI_DATA values."""
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_register_elf_h(ElfData, prefix='ELFDATA')
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class Machine(_TypedConstant):
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"""ELF machine type. Type of values in Ehdr.e_machine field."""
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prefix = 'EM_'
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_register_elf_h(Machine, skip=('EM_ARC_A5',))
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class Et(_TypedConstant):
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"""ELF file type. Type of ET_* values and the Ehdr.e_type field."""
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prefix = 'ET_'
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_register_elf_h(Et, ranges=True)
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class Shn(_IntConstant):
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"""ELF reserved section indices."""
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prefix = 'SHN_'
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class ShnMIPS(Shn):
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"""Supplemental SHN_* constants for EM_MIPS."""
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class ShnPARISC(Shn):
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"""Supplemental SHN_* constants for EM_PARISC."""
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_register_elf_h(ShnMIPS, prefix='SHN_MIPS_', parent=Shn)
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_register_elf_h(ShnPARISC, prefix='SHN_PARISC_', parent=Shn)
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_register_elf_h(Shn, skip='SHN_LORESERVE SHN_HIRESERVE'.split(), ranges=True)
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class Sht(_TypedConstant):
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"""ELF section types. Type of SHT_* values."""
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prefix = 'SHT_'
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class ShtALPHA(Sht):
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"""Supplemental SHT_* constants for EM_ALPHA."""
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class ShtARM(Sht):
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"""Supplemental SHT_* constants for EM_ARM."""
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class ShtCSKY(Sht):
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"""Supplemental SHT_* constants for EM_CSKY."""
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class ShtIA_64(Sht):
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"""Supplemental SHT_* constants for EM_IA_64."""
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class ShtMIPS(Sht):
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"""Supplemental SHT_* constants for EM_MIPS."""
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class ShtPARISC(Sht):
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"""Supplemental SHT_* constants for EM_PARISC."""
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class ShtRISCV(Sht):
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"""Supplemental SHT_* constants for EM_RISCV."""
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_register_elf_h(ShtALPHA, prefix='SHT_ALPHA_', parent=Sht)
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_register_elf_h(ShtARM, prefix='SHT_ARM_', parent=Sht)
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_register_elf_h(ShtCSKY, prefix='SHT_CSKY_', parent=Sht)
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_register_elf_h(ShtIA_64, prefix='SHT_IA_64_', parent=Sht)
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_register_elf_h(ShtMIPS, prefix='SHT_MIPS_', parent=Sht)
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_register_elf_h(ShtPARISC, prefix='SHT_PARISC_', parent=Sht)
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_register_elf_h(ShtRISCV, prefix='SHT_RISCV_', parent=Sht)
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_register_elf_h(Sht, ranges=True,
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skip='SHT_LOSUNW SHT_HISUNW SHT_LOUSER SHT_HIUSER'.split())
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class Pf(_FlagConstant):
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"""Program header flags. Type of Phdr.p_flags values."""
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prefix = 'PF_'
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class PfARM(Pf):
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"""Supplemental PF_* flags for EM_ARM."""
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class PfHP(Pf):
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"""Supplemental PF_* flags for HP-UX."""
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class PfIA_64(Pf):
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"""Supplemental PF_* flags for EM_IA_64."""
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class PfMIPS(Pf):
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"""Supplemental PF_* flags for EM_MIPS."""
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class PfPARISC(Pf):
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"""Supplemental PF_* flags for EM_PARISC."""
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_register_elf_h(PfARM, prefix='PF_ARM_', parent=Pf)
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_register_elf_h(PfHP, prefix='PF_HP_', parent=Pf)
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_register_elf_h(PfIA_64, prefix='PF_IA_64_', parent=Pf)
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_register_elf_h(PfMIPS, prefix='PF_MIPS_', parent=Pf)
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_register_elf_h(PfPARISC, prefix='PF_PARISC_', parent=Pf)
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_register_elf_h(Pf, skip='PF_MASKOS PF_MASKPROC'.split())
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class Shf(_FlagConstant):
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"""Section flags. Type of Shdr.sh_type values."""
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prefix = 'SHF_'
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class ShfALPHA(Shf):
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"""Supplemental SHF_* constants for EM_ALPHA."""
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class ShfARM(Shf):
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"""Supplemental SHF_* constants for EM_ARM."""
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class ShfIA_64(Shf):
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"""Supplemental SHF_* constants for EM_IA_64."""
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class ShfMIPS(Shf):
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"""Supplemental SHF_* constants for EM_MIPS."""
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class ShfPARISC(Shf):
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"""Supplemental SHF_* constants for EM_PARISC."""
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_register_elf_h(ShfALPHA, prefix='SHF_ALPHA_', parent=Shf)
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_register_elf_h(ShfARM, prefix='SHF_ARM_', parent=Shf)
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_register_elf_h(ShfIA_64, prefix='SHF_IA_64_', parent=Shf)
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_register_elf_h(ShfMIPS, prefix='SHF_MIPS_', parent=Shf)
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_register_elf_h(ShfPARISC, prefix='SHF_PARISC_', parent=Shf)
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_register_elf_h(Shf, skip='SHF_MASKOS SHF_MASKPROC'.split())
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class Stb(_TypedConstant):
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"""ELF symbol binding type."""
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prefix = 'STB_'
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_register_elf_h(Stb, ranges=True)
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class Stt(_TypedConstant):
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"""ELF symbol type."""
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prefix = 'STT_'
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class SttARM(Sht):
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"""Supplemental STT_* constants for EM_ARM."""
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class SttPARISC(Sht):
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"""Supplemental STT_* constants for EM_PARISC."""
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class SttSPARC(Sht):
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"""Supplemental STT_* constants for EM_SPARC."""
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STT_SPARC_REGISTER = 13
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class SttX86_64(Sht):
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"""Supplemental STT_* constants for EM_X86_64."""
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_register_elf_h(SttARM, prefix='STT_ARM_', parent=Stt)
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_register_elf_h(SttPARISC, prefix='STT_PARISC_', parent=Stt)
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_register_elf_h(SttSPARC, prefix='STT_SPARC_', parent=Stt)
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_register_elf_h(Stt, ranges=True)
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class Pt(_TypedConstant):
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"""ELF program header types. Type of Phdr.p_type."""
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prefix = 'PT_'
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class PtAARCH64(Pt):
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"""Supplemental PT_* constants for EM_AARCH64."""
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class PtARM(Pt):
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"""Supplemental PT_* constants for EM_ARM."""
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class PtHP(Pt):
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"""Supplemental PT_* constants for HP-U."""
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class PtIA_64(Pt):
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"""Supplemental PT_* constants for EM_IA_64."""
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class PtMIPS(Pt):
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"""Supplemental PT_* constants for EM_MIPS."""
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class PtPARISC(Pt):
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"""Supplemental PT_* constants for EM_PARISC."""
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class PtRISCV(Pt):
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"""Supplemental PT_* constants for EM_RISCV."""
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_register_elf_h(PtAARCH64, prefix='PT_AARCH64_', parent=Pt)
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_register_elf_h(PtARM, prefix='PT_ARM_', parent=Pt)
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_register_elf_h(PtHP, prefix='PT_HP_', parent=Pt)
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_register_elf_h(PtIA_64, prefix='PT_IA_64_', parent=Pt)
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_register_elf_h(PtMIPS, prefix='PT_MIPS_', parent=Pt)
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_register_elf_h(PtPARISC, prefix='PT_PARISC_', parent=Pt)
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_register_elf_h(PtRISCV, prefix='PT_RISCV_', parent=Pt)
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_register_elf_h(Pt, skip='PT_LOSUNW PT_HISUNW'.split(), ranges=True)
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class Dt(_TypedConstant):
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"""ELF dynamic segment tags. Type of Dyn.d_val."""
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prefix = 'DT_'
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class DtAARCH64(Dt):
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"""Supplemental DT_* constants for EM_AARCH64."""
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class DtALPHA(Dt):
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"""Supplemental DT_* constants for EM_ALPHA."""
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class DtALTERA_NIOS2(Dt):
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"""Supplemental DT_* constants for EM_ALTERA_NIOS2."""
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class DtIA_64(Dt):
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"""Supplemental DT_* constants for EM_IA_64."""
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class DtMIPS(Dt):
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"""Supplemental DT_* constants for EM_MIPS."""
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class DtPPC(Dt):
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"""Supplemental DT_* constants for EM_PPC."""
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class DtPPC64(Dt):
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"""Supplemental DT_* constants for EM_PPC64."""
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class DtRISCV(Dt):
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"""Supplemental DT_* constants for EM_RISCV."""
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class DtSPARC(Dt):
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"""Supplemental DT_* constants for EM_SPARC."""
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_dt_skip = '''
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DT_ENCODING DT_PROCNUM
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DT_ADDRRNGLO DT_ADDRRNGHI DT_ADDRNUM
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DT_VALRNGLO DT_VALRNGHI DT_VALNUM
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DT_VERSIONTAGNUM DT_EXTRANUM
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DT_AARCH64_NUM
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DT_ALPHA_NUM
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DT_IA_64_NUM
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DT_MIPS_NUM
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DT_PPC_NUM
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DT_PPC64_NUM
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DT_SPARC_NUM
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'''.strip().split()
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_register_elf_h(DtAARCH64, prefix='DT_AARCH64_', skip=_dt_skip, parent=Dt)
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_register_elf_h(DtALPHA, prefix='DT_ALPHA_', skip=_dt_skip, parent=Dt)
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_register_elf_h(DtALTERA_NIOS2, prefix='DT_NIOS2_', skip=_dt_skip, parent=Dt)
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_register_elf_h(DtIA_64, prefix='DT_IA_64_', skip=_dt_skip, parent=Dt)
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_register_elf_h(DtMIPS, prefix='DT_MIPS_', skip=_dt_skip, parent=Dt)
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_register_elf_h(DtPPC, prefix='DT_PPC_', skip=_dt_skip, parent=Dt)
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_register_elf_h(DtPPC64, prefix='DT_PPC64_', skip=_dt_skip, parent=Dt)
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_register_elf_h(DtRISCV, prefix='DT_RISCV_', skip=_dt_skip, parent=Dt)
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_register_elf_h(DtSPARC, prefix='DT_SPARC_', skip=_dt_skip, parent=Dt)
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_register_elf_h(Dt, skip=_dt_skip, ranges=True)
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del _dt_skip
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# Constant extraction is complete.
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del _register_elf_h
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del _elf_h
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|
|
class StInfo:
|
|
"""ELF symbol binding and type. Type of the Sym.st_info field."""
|
|
def __init__(self, arg0, arg1=None):
|
|
if isinstance(arg0, int) and arg1 is None:
|
|
self.bind = Stb(arg0 >> 4)
|
|
self.type = Stt(arg0 & 15)
|
|
else:
|
|
self.bind = Stb(arg0)
|
|
self.type = Stt(arg1)
|
|
|
|
def value(self):
|
|
"""Returns the raw value for the bind/type combination."""
|
|
return (self.bind.value() << 4) | (self.type.value())
|
|
|
|
# Type in an ELF file. Used for deserialization.
|
|
_Layout = collections.namedtuple('_Layout', 'unpack size')
|
|
|
|
def _define_layouts(baseclass: type, layout32: str, layout64: str,
|
|
types=None, fields32=None):
|
|
"""Assign variants dict to baseclass.
|
|
|
|
The variants dict is indexed by (ElfClass, ElfData) pairs, and its
|
|
values are _Layout instances.
|
|
|
|
"""
|
|
struct32 = struct.Struct(layout32)
|
|
struct64 = struct.Struct(layout64)
|
|
|
|
# Check that the struct formats yield the right number of components.
|
|
for s in (struct32, struct64):
|
|
example = s.unpack(b' ' * s.size)
|
|
if len(example) != len(baseclass._fields):
|
|
raise ValueError('{!r} yields wrong field count: {} != {}'.format(
|
|
s.format, len(example), len(baseclass._fields)))
|
|
|
|
# Check that field names in types are correct.
|
|
if types is None:
|
|
types = ()
|
|
for n in types:
|
|
if n not in baseclass._fields:
|
|
raise ValueError('{} does not have field {!r}'.format(
|
|
baseclass.__name__, n))
|
|
|
|
if fields32 is not None \
|
|
and set(fields32) != set(baseclass._fields):
|
|
raise ValueError('{!r} is not a permutation of the fields {!r}'.format(
|
|
fields32, baseclass._fields))
|
|
|
|
def unique_name(name, used_names = (set((baseclass.__name__,))
|
|
| set(baseclass._fields)
|
|
| {n.__name__
|
|
for n in (types or {}).values()})):
|
|
"""Find a name that is not used for a class or field name."""
|
|
candidate = name
|
|
n = 0
|
|
while candidate in used_names:
|
|
n += 1
|
|
candidate = '{}{}'.format(name, n)
|
|
used_names.add(candidate)
|
|
return candidate
|
|
|
|
blob_name = unique_name('blob')
|
|
struct_unpack_name = unique_name('struct_unpack')
|
|
comps_name = unique_name('comps')
|
|
|
|
layouts = {}
|
|
for (bits, elfclass, layout, fields) in (
|
|
(32, ElfClass.ELFCLASS32, layout32, fields32),
|
|
(64, ElfClass.ELFCLASS64, layout64, None),
|
|
):
|
|
for (elfdata, structprefix, funcsuffix) in (
|
|
(ElfData.ELFDATA2LSB, '<', 'LE'),
|
|
(ElfData.ELFDATA2MSB, '>', 'BE'),
|
|
):
|
|
env = {
|
|
baseclass.__name__: baseclass,
|
|
struct_unpack_name: struct.unpack,
|
|
}
|
|
|
|
# Add the type converters.
|
|
if types:
|
|
for cls in types.values():
|
|
env[cls.__name__] = cls
|
|
|
|
funcname = ''.join(
|
|
('unpack_', baseclass.__name__, str(bits), funcsuffix))
|
|
|
|
code = '''
|
|
def {funcname}({blob_name}):
|
|
'''.format(funcname=funcname, blob_name=blob_name)
|
|
|
|
indent = ' ' * 4
|
|
unpack_call = '{}({!r}, {})'.format(
|
|
struct_unpack_name, structprefix + layout, blob_name)
|
|
field_names = ', '.join(baseclass._fields)
|
|
if types is None and fields is None:
|
|
code += '{}return {}({})\n'.format(
|
|
indent, baseclass.__name__, unpack_call)
|
|
else:
|
|
# Destructuring tuple assignment.
|
|
if fields is None:
|
|
code += '{}{} = {}\n'.format(
|
|
indent, field_names, unpack_call)
|
|
else:
|
|
# Use custom field order.
|
|
code += '{}{} = {}\n'.format(
|
|
indent, ', '.join(fields), unpack_call)
|
|
|
|
# Perform the type conversions.
|
|
for n in baseclass._fields:
|
|
if n in types:
|
|
code += '{}{} = {}({})\n'.format(
|
|
indent, n, types[n].__name__, n)
|
|
# Create the named tuple.
|
|
code += '{}return {}({})\n'.format(
|
|
indent, baseclass.__name__, field_names)
|
|
|
|
exec(code, env)
|
|
layouts[(elfclass, elfdata)] = _Layout(
|
|
env[funcname], struct.calcsize(layout))
|
|
baseclass.layouts = layouts
|
|
|
|
|
|
# Corresponds to EI_* indices into Elf*_Ehdr.e_indent.
|
|
class Ident(collections.namedtuple('Ident',
|
|
'ei_mag ei_class ei_data ei_version ei_osabi ei_abiversion ei_pad')):
|
|
|
|
def __new__(cls, *args):
|
|
"""Construct an object from a blob or its constituent fields."""
|
|
if len(args) == 1:
|
|
return cls.unpack(args[0])
|
|
return cls.__base__.__new__(cls, *args)
|
|
|
|
@staticmethod
|
|
def unpack(blob: memoryview) -> 'Ident':
|
|
"""Parse raws data into a tuple."""
|
|
ei_mag, ei_class, ei_data, ei_version, ei_osabi, ei_abiversion, \
|
|
ei_pad = struct.unpack('4s5B7s', blob)
|
|
return Ident(ei_mag, ElfClass(ei_class), ElfData(ei_data),
|
|
ei_version, ei_osabi, ei_abiversion, ei_pad)
|
|
size = 16
|
|
|
|
# Corresponds to Elf32_Ehdr and Elf64_Ehdr.
|
|
Ehdr = collections.namedtuple('Ehdr',
|
|
'e_ident e_type e_machine e_version e_entry e_phoff e_shoff e_flags'
|
|
+ ' e_ehsize e_phentsize e_phnum e_shentsize e_shnum e_shstrndx')
|
|
_define_layouts(Ehdr,
|
|
layout32='16s2H5I6H',
|
|
layout64='16s2HI3QI6H',
|
|
types=dict(e_ident=Ident,
|
|
e_machine=Machine,
|
|
e_type=Et,
|
|
e_shstrndx=Shn))
|
|
|
|
# Corresponds to Elf32_Phdr and Elf64_Pdhr. Order follows the latter.
|
|
Phdr = collections.namedtuple('Phdr',
|
|
'p_type p_flags p_offset p_vaddr p_paddr p_filesz p_memsz p_align')
|
|
_define_layouts(Phdr,
|
|
layout32='8I',
|
|
fields32=('p_type', 'p_offset', 'p_vaddr', 'p_paddr',
|
|
'p_filesz', 'p_memsz', 'p_flags', 'p_align'),
|
|
layout64='2I6Q',
|
|
types=dict(p_type=Pt, p_flags=Pf))
|
|
|
|
|
|
# Corresponds to Elf32_Shdr and Elf64_Shdr.
|
|
class Shdr(collections.namedtuple('Shdr',
|
|
'sh_name sh_type sh_flags sh_addr sh_offset sh_size sh_link sh_info'
|
|
+ ' sh_addralign sh_entsize')):
|
|
def resolve(self, strtab: 'StringTable') -> 'Shdr':
|
|
"""Resolve sh_name using a string table."""
|
|
return self.__class__(strtab.get(self[0]), *self[1:])
|
|
_define_layouts(Shdr,
|
|
layout32='10I',
|
|
layout64='2I4Q2I2Q',
|
|
types=dict(sh_type=Sht,
|
|
sh_flags=Shf,
|
|
sh_link=Shn))
|
|
|
|
# Corresponds to Elf32_Dyn and Elf64_Dyn. The nesting through the
|
|
# d_un union is skipped, and d_ptr is missing (its representation in
|
|
# Python would be identical to d_val).
|
|
Dyn = collections.namedtuple('Dyn', 'd_tag d_val')
|
|
_define_layouts(Dyn,
|
|
layout32='2i',
|
|
layout64='2q',
|
|
types=dict(d_tag=Dt))
|
|
|
|
# Corresponds to Elf32_Sym and Elf64_Sym.
|
|
class Sym(collections.namedtuple('Sym',
|
|
'st_name st_info st_other st_shndx st_value st_size')):
|
|
def resolve(self, strtab: 'StringTable') -> 'Sym':
|
|
"""Resolve st_name using a string table."""
|
|
return self.__class__(strtab.get(self[0]), *self[1:])
|
|
_define_layouts(Sym,
|
|
layout32='3I2BH',
|
|
layout64='I2BH2Q',
|
|
fields32=('st_name', 'st_value', 'st_size', 'st_info',
|
|
'st_other', 'st_shndx'),
|
|
types=dict(st_shndx=Shn,
|
|
st_info=StInfo))
|
|
|
|
# Corresponds to Elf32_Rel and Elf64_Rel.
|
|
Rel = collections.namedtuple('Rel', 'r_offset r_info')
|
|
_define_layouts(Rel,
|
|
layout32='2I',
|
|
layout64='2Q')
|
|
|
|
# Corresponds to Elf32_Rel and Elf64_Rel.
|
|
Rela = collections.namedtuple('Rela', 'r_offset r_info r_addend')
|
|
_define_layouts(Rela,
|
|
layout32='3I',
|
|
layout64='3Q')
|
|
|
|
class StringTable:
|
|
"""ELF string table."""
|
|
def __init__(self, blob):
|
|
"""Create a new string table backed by the data in the blob.
|
|
|
|
blob: a memoryview-like object
|
|
|
|
"""
|
|
self.blob = blob
|
|
|
|
def get(self, index) -> bytes:
|
|
"""Returns the null-terminated byte string at the index."""
|
|
blob = self.blob
|
|
endindex = index
|
|
while True:
|
|
if blob[endindex] == 0:
|
|
return bytes(blob[index:endindex])
|
|
endindex += 1
|
|
|
|
class Image:
|
|
"""ELF image parser."""
|
|
def __init__(self, image):
|
|
"""Create an ELF image from binary image data.
|
|
|
|
image: a memoryview-like object that supports efficient range
|
|
subscripting.
|
|
|
|
"""
|
|
self.image = image
|
|
ident = self.read(Ident, 0)
|
|
classdata = (ident.ei_class, ident.ei_data)
|
|
# Set self.Ehdr etc. to the subtypes with the right parsers.
|
|
for typ in (Ehdr, Phdr, Shdr, Dyn, Sym, Rel, Rela):
|
|
setattr(self, typ.__name__, typ.layouts.get(classdata, None))
|
|
|
|
if self.Ehdr is not None:
|
|
self.ehdr = self.read(self.Ehdr, 0)
|
|
self._shdr_num = self._compute_shdr_num()
|
|
else:
|
|
self.ehdr = None
|
|
self._shdr_num = 0
|
|
|
|
self._section = {}
|
|
self._stringtab = {}
|
|
|
|
if self._shdr_num > 0:
|
|
self._shdr_strtab = self._find_shdr_strtab()
|
|
else:
|
|
self._shdr_strtab = None
|
|
|
|
@staticmethod
|
|
def readfile(path: str) -> 'Image':
|
|
"""Reads the ELF file at the specified path."""
|
|
with open(path, 'rb') as inp:
|
|
return Image(memoryview(inp.read()))
|
|
|
|
def _compute_shdr_num(self) -> int:
|
|
"""Computes the actual number of section headers."""
|
|
shnum = self.ehdr.e_shnum
|
|
if shnum == 0:
|
|
if self.ehdr.e_shoff == 0 or self.ehdr.e_shentsize == 0:
|
|
# No section headers.
|
|
return 0
|
|
# Otherwise the extension mechanism is used (which may be
|
|
# needed because e_shnum is just 16 bits).
|
|
return self.read(self.Shdr, self.ehdr.e_shoff).sh_size
|
|
return shnum
|
|
|
|
def _find_shdr_strtab(self) -> StringTable:
|
|
"""Finds the section header string table (maybe via extensions)."""
|
|
shstrndx = self.ehdr.e_shstrndx
|
|
if shstrndx == Shn.SHN_XINDEX:
|
|
shstrndx = self.read(self.Shdr, self.ehdr.e_shoff).sh_link
|
|
return self._find_stringtab(shstrndx)
|
|
|
|
def read(self, typ: type, offset:int ):
|
|
"""Reads an object at a specific offset.
|
|
|
|
The type must have been enhanced using _define_variants.
|
|
|
|
"""
|
|
return typ.unpack(self.image[offset: offset + typ.size])
|
|
|
|
def phdrs(self) -> Phdr:
|
|
"""Generator iterating over the program headers."""
|
|
if self.ehdr is None:
|
|
return
|
|
size = self.ehdr.e_phentsize
|
|
if size != self.Phdr.size:
|
|
raise ValueError('Unexpected Phdr size in ELF header: {} != {}'
|
|
.format(size, self.Phdr.size))
|
|
|
|
offset = self.ehdr.e_phoff
|
|
for _ in range(self.ehdr.e_phnum):
|
|
yield self.read(self.Phdr, offset)
|
|
offset += size
|
|
|
|
def shdrs(self, resolve: bool=True) -> Shdr:
|
|
"""Generator iterating over the section headers.
|
|
|
|
If resolve, section names are automatically translated
|
|
using the section header string table.
|
|
|
|
"""
|
|
if self._shdr_num == 0:
|
|
return
|
|
|
|
size = self.ehdr.e_shentsize
|
|
if size != self.Shdr.size:
|
|
raise ValueError('Unexpected Shdr size in ELF header: {} != {}'
|
|
.format(size, self.Shdr.size))
|
|
|
|
offset = self.ehdr.e_shoff
|
|
for _ in range(self._shdr_num):
|
|
shdr = self.read(self.Shdr, offset)
|
|
if resolve:
|
|
shdr = shdr.resolve(self._shdr_strtab)
|
|
yield shdr
|
|
offset += size
|
|
|
|
def dynamic(self) -> Dyn:
|
|
"""Generator iterating over the dynamic segment."""
|
|
for phdr in self.phdrs():
|
|
if phdr.p_type == Pt.PT_DYNAMIC:
|
|
# Pick the first dynamic segment, like the loader.
|
|
if phdr.p_filesz == 0:
|
|
# Probably separated debuginfo.
|
|
return
|
|
offset = phdr.p_offset
|
|
end = offset + phdr.p_memsz
|
|
size = self.Dyn.size
|
|
while True:
|
|
next_offset = offset + size
|
|
if next_offset > end:
|
|
raise ValueError(
|
|
'Dynamic segment size {} is not a multiple of Dyn size {}'.format(
|
|
phdr.p_memsz, size))
|
|
yield self.read(self.Dyn, offset)
|
|
if next_offset == end:
|
|
return
|
|
offset = next_offset
|
|
|
|
def syms(self, shdr: Shdr, resolve: bool=True) -> Sym:
|
|
"""A generator iterating over a symbol table.
|
|
|
|
If resolve, symbol names are automatically translated using
|
|
the string table for the symbol table.
|
|
|
|
"""
|
|
assert shdr.sh_type == Sht.SHT_SYMTAB
|
|
size = shdr.sh_entsize
|
|
if size != self.Sym.size:
|
|
raise ValueError('Invalid symbol table entry size {}'.format(size))
|
|
offset = shdr.sh_offset
|
|
end = shdr.sh_offset + shdr.sh_size
|
|
if resolve:
|
|
strtab = self._find_stringtab(shdr.sh_link)
|
|
while offset < end:
|
|
sym = self.read(self.Sym, offset)
|
|
if resolve:
|
|
sym = sym.resolve(strtab)
|
|
yield sym
|
|
offset += size
|
|
if offset != end:
|
|
raise ValueError('Symbol table is not a multiple of entry size')
|
|
|
|
def lookup_string(self, strtab_index: int, strtab_offset: int) -> bytes:
|
|
"""Looks up a string in a string table identified by its link index."""
|
|
try:
|
|
strtab = self._stringtab[strtab_index]
|
|
except KeyError:
|
|
strtab = self._find_stringtab(strtab_index)
|
|
return strtab.get(strtab_offset)
|
|
|
|
def find_section(self, shndx: Shn) -> Shdr:
|
|
"""Returns the section header for the indexed section.
|
|
|
|
The section name is not resolved.
|
|
"""
|
|
try:
|
|
return self._section[shndx]
|
|
except KeyError:
|
|
pass
|
|
if shndx in Shn:
|
|
raise ValueError('Reserved section index {}'.format(shndx))
|
|
idx = shndx.value
|
|
if idx < 0 or idx > self._shdr_num:
|
|
raise ValueError('Section index {} out of range [0, {})'.format(
|
|
idx, self._shdr_num))
|
|
shdr = self.read(
|
|
self.Shdr, self.ehdr.e_shoff + idx * self.Shdr.size)
|
|
self._section[shndx] = shdr
|
|
return shdr
|
|
|
|
def _find_stringtab(self, sh_link: int) -> StringTable:
|
|
if sh_link in self._stringtab:
|
|
return self._stringtab
|
|
if sh_link < 0 or sh_link >= self._shdr_num:
|
|
raise ValueError('Section index {} out of range [0, {})'.format(
|
|
sh_link, self._shdr_num))
|
|
shdr = self.read(
|
|
self.Shdr, self.ehdr.e_shoff + sh_link * self.Shdr.size)
|
|
if shdr.sh_type != Sht.SHT_STRTAB:
|
|
raise ValueError(
|
|
'Section {} is not a string table: {}'.format(
|
|
sh_link, shdr.sh_type))
|
|
strtab = StringTable(
|
|
self.image[shdr.sh_offset:shdr.sh_offset + shdr.sh_size])
|
|
# This could retrain essentially arbitrary amounts of data,
|
|
# but caching string tables seems important for performance.
|
|
self._stringtab[sh_link] = strtab
|
|
return strtab
|
|
|
|
def elf_hash(s):
|
|
"""Computes the ELF hash of the string."""
|
|
acc = 0
|
|
for ch in s:
|
|
if type(ch) is not int:
|
|
ch = ord(ch)
|
|
acc = ((acc << 4) + ch) & 0xffffffff
|
|
top = acc & 0xf0000000
|
|
acc = (acc ^ (top >> 24)) & ~top
|
|
return acc
|
|
|
|
def gnu_hash(s):
|
|
"""Computes the GNU hash of the string."""
|
|
h = 5381
|
|
for ch in s:
|
|
if type(ch) is not int:
|
|
ch = ord(ch)
|
|
h = (h * 33 + ch) & 0xffffffff
|
|
return h
|
|
|
|
__all__ = [name for name in dir() if name[0].isupper()]
|