scripts: Add glibcelf.py module

Hopefully, this will lead to tests that are easier to maintain.  The
current approach of parsing readelf -W output using regular expressions
is not necessarily easier than parsing the ELF data directly.

This module is still somewhat incomplete (e.g., coverage of relocation
types and versioning information is missing), but it is sufficient to
perform basic symbol analysis or program header analysis.

The EM_* mapping for architecture-specific constant classes (e.g.,
SttX86_64) is not yet implemented.  The classes are defined for the
benefit of elf/tst-glibcelf.py.

Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>

3 files changed, 1402 insertions, 0 deletions

diff --git a/elf/Makefile b/elf/Makefile
index d30d0ee..3d79f40 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -1115,6 +1115,13 @@ tests-special += $(objpfx)check-abi-ld.out
 update-abi: update-abi-ld
 update-all-abi: update-all-abi-ld
 
+tests-special += $(objpfx)tst-glibcelf.out
+$(objpfx)tst-glibcelf.out: tst-glibcelf.py elf.h $(..)/scripts/glibcelf.py \
+  $(..)/scripts/glibcextract.py
+	PYTHONPATH=$(..)scripts $(PYTHON) tst-glibcelf.py \
+          --cc="$(CC) $(patsubst -DMODULE_NAME=%,-DMODULE_NAME=testsuite,$(CPPFLAGS))" \
+	  < /dev/null > $@ 2>&1; $(evaluate-test)
+
 # The test requires shared _and_ PIE because the executable
 # unit test driver must be able to link with the shared object
 # that is going to eventually go into an installed DSO.
diff --git a/elf/tst-glibcelf.py b/elf/tst-glibcelf.py
new file mode 100644
index 0000000..bf15a3b
--- /dev/null
+++ b/elf/tst-glibcelf.py
@@ -0,0 +1,260 @@
+#!/usr/bin/python3
+# Verify scripts/glibcelf.py contents against elf/elf.h.
+# Copyright (C) 2022 Free Software Foundation, Inc.
+# This file is part of the GNU C Library.
+#
+# The GNU C Library is free software; you can redistribute it and/or
+# modify it under the terms of the GNU Lesser General Public
+# License as published by the Free Software Foundation; either
+# version 2.1 of the License, or (at your option) any later version.
+#
+# The GNU C Library 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
+# Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with the GNU C Library; if not, see
+# <https://www.gnu.org/licenses/>.
+
+import argparse
+import enum
+import sys
+
+import glibcelf
+import glibcextract
+
+errors_encountered = 0
+
+def error(message):
+    global errors_encountered
+    sys.stdout.write('error: {}\n'.format(message))
+    errors_encountered += 1
+
+# The enum constants in glibcelf are expected to have exactly these
+# prefixes.
+expected_constant_prefixes = tuple(
+    'ELFCLASS ELFDATA EM_ ET_ DT_ PF_ PT_ SHF_ SHN_ SHT_ STB_ STT_'.split())
+
+def find_constant_prefix(name):
+    """Returns a matching prefix from expected_constant_prefixes or None."""
+    for prefix in expected_constant_prefixes:
+        if name.startswith(prefix):
+            return prefix
+    return None
+
+def find_enum_types():
+    """A generator for OpenIntEnum and IntFlag classes in glibcelf."""
+    for obj in vars(glibcelf).values():
+        if isinstance(obj, type) and obj.__bases__[0] in (
+                glibcelf._OpenIntEnum, enum.Enum, enum.IntFlag):
+            yield obj
+
+def check_duplicates():
+    """Verifies that enum types do not have duplicate values.
+
+    Different types must have different member names, too.
+
+    """
+    global_seen = {}
+    for typ in find_enum_types():
+        seen = {}
+        last = None
+        for (name, e) in typ.__members__.items():
+            if e.value in seen:
+                error('{} has {}={} and {}={}'.format(
+                    typ, seen[e.value], e.value, name, e.value))
+                last = e
+            else:
+                seen[e.value] = name
+                if last is not None and last.value > e.value:
+                    error('{} has {}={} after {}={}'.format(
+                        typ, name, e.value, last.name, last.value))
+                if name in global_seen:
+                    error('{} used in {} and {}'.format(
+                        name, global_seen[name], typ))
+                else:
+                    global_seen[name] = typ
+
+def check_constant_prefixes():
+    """Check that the constant prefixes match expected_constant_prefixes."""
+    seen = set()
+    for typ in find_enum_types():
+        typ_prefix = None
+        for val in typ:
+            prefix = find_constant_prefix(val.name)
+            if prefix is None:
+                error('constant {!r} for {} has unknown prefix'.format(
+                    val, typ))
+                break
+            elif typ_prefix is None:
+                typ_prefix = prefix
+                seen.add(typ_prefix)
+            elif prefix != typ_prefix:
+                error('prefix {!r} for constant {!r}, expected {!r}'.format(
+                    prefix, val, typ_prefix))
+        if typ_prefix is None:
+            error('empty enum type {}'.format(typ))
+
+    for prefix in sorted(set(expected_constant_prefixes) - seen):
+        error('missing constant prefix {!r}'.format(prefix))
+    # Reverse difference is already covered inside the loop.
+
+def find_elf_h_constants(cc):
+    """Returns a dictionary of relevant constants from <elf.h>."""
+    return glibcextract.compute_macro_consts(
+        source_text='#include <elf.h>',
+        cc=cc,
+        macro_re='|'.join(
+            prefix + '.*' for prefix in expected_constant_prefixes))
+
+# The first part of the pair is a name of an <elf.h> constant that is
+# dropped from glibcelf.  The second part is the constant as it is
+# used in <elf.h>.
+glibcelf_skipped_aliases = (
+    ('EM_ARC_A5', 'EM_ARC_COMPACT'),
+    ('PF_PARISC_SBP', 'PF_HP_SBP')
+)
+
+# Constants that provide little value and are not included in
+# glibcelf: *LO*/*HI* range constants, *NUM constants counting the
+# number of constants.  Also includes the alias names from
+# glibcelf_skipped_aliases.
+glibcelf_skipped_constants = frozenset(
+    [e[0] for e in glibcelf_skipped_aliases]) | frozenset("""
+DT_AARCH64_NUM
+DT_ADDRNUM
+DT_ADDRRNGHI
+DT_ADDRRNGLO
+DT_ALPHA_NUM
+DT_ENCODING
+DT_EXTRANUM
+DT_HIOS
+DT_HIPROC
+DT_IA_64_NUM
+DT_LOOS
+DT_LOPROC
+DT_MIPS_NUM
+DT_NUM
+DT_PPC64_NUM
+DT_PPC_NUM
+DT_PROCNUM
+DT_SPARC_NUM
+DT_VALNUM
+DT_VALRNGHI
+DT_VALRNGLO
+DT_VERSIONTAGNUM
+ELFCLASSNUM
+ELFDATANUM
+ET_HIOS
+ET_HIPROC
+ET_LOOS
+ET_LOPROC
+ET_NUM
+PF_MASKOS
+PF_MASKPROC
+PT_HIOS
+PT_HIPROC
+PT_HISUNW
+PT_LOOS
+PT_LOPROC
+PT_LOSUNW
+SHF_MASKOS
+SHF_MASKPROC
+SHN_HIOS
+SHN_HIPROC
+SHN_HIRESERVE
+SHN_LOOS
+SHN_LOPROC
+SHN_LORESERVE
+SHT_HIOS
+SHT_HIPROC
+SHT_HIPROC
+SHT_HISUNW
+SHT_HIUSER
+SHT_LOOS
+SHT_LOPROC
+SHT_LOSUNW
+SHT_LOUSER
+SHT_NUM
+STB_HIOS
+STB_HIPROC
+STB_LOOS
+STB_LOPROC
+STB_NUM
+STT_HIOS
+STT_HIPROC
+STT_LOOS
+STT_LOPROC
+STT_NUM
+""".strip().split())
+
+def check_constant_values(cc):
+    """Checks the values of <elf.h> constants against glibcelf."""
+
+    glibcelf_constants = {
+        e.name: e for typ in find_enum_types() for e in typ}
+    elf_h_constants = find_elf_h_constants(cc=cc)
+
+    missing_in_glibcelf = (set(elf_h_constants) - set(glibcelf_constants)
+                           - glibcelf_skipped_constants)
+    for name in sorted(missing_in_glibcelf):
+        error('constant {} is missing from glibcelf'.format(name))
+
+    unexpected_in_glibcelf = \
+        set(glibcelf_constants) & glibcelf_skipped_constants
+    for name in sorted(unexpected_in_glibcelf):
+        error('constant {} is supposed to be filtered from glibcelf'.format(
+            name))
+
+    missing_in_elf_h = set(glibcelf_constants) - set(elf_h_constants)
+    for name in sorted(missing_in_elf_h):
+        error('constant {} is missing from <elf.h>'.format(name))
+
+    expected_in_elf_h = glibcelf_skipped_constants - set(elf_h_constants)
+    for name in expected_in_elf_h:
+        error('filtered constant {} is missing from <elf.h>'.format(name))
+
+    for alias_name, name_in_glibcelf in glibcelf_skipped_aliases:
+        if name_in_glibcelf not in glibcelf_constants:
+            error('alias value {} for {} not in glibcelf'.format(
+                name_in_glibcelf, alias_name))
+        elif (int(elf_h_constants[alias_name])
+              != glibcelf_constants[name_in_glibcelf].value):
+            error('<elf.h> has {}={}, glibcelf has {}={}'.format(
+                alias_name, elf_h_constants[alias_name],
+                name_in_glibcelf, glibcelf_constants[name_in_glibcelf]))
+
+    # Check for value mismatches:
+    for name in sorted(set(glibcelf_constants) & set(elf_h_constants)):
+        glibcelf_value = glibcelf_constants[name].value
+        elf_h_value = int(elf_h_constants[name])
+        # On 32-bit architectures <elf.h> as some constants that are
+        # parsed as signed, while they are unsigned in glibcelf.  So
+        # far, this only affects some flag constants, so special-case
+        # them here.
+        if (glibcelf_value != elf_h_value
+            and not (isinstance(glibcelf_constants[name], enum.IntFlag)
+                     and glibcelf_value == 1 << 31
+                     and elf_h_value == -(1 << 31))):
+            error('{}: glibcelf has {!r}, <elf.h> has {!r}'.format(
+                name, glibcelf_value, elf_h_value))
+
+def main():
+    """The main entry point."""
+    parser = argparse.ArgumentParser(
+        description="Check glibcelf.py and elf.h against each other.")
+    parser.add_argument('--cc', metavar='CC',
+                        help='C compiler (including options) to use')
+    args = parser.parse_args()
+
+    check_duplicates()
+    check_constant_prefixes()
+    check_constant_values(cc=args.cc)
+
+    if errors_encountered > 0:
+        print("note: errors encountered:", errors_encountered)
+        sys.exit(1)
+
+if __name__ == '__main__':
+    main()
diff --git a/scripts/glibcelf.py b/scripts/glibcelf.py
new file mode 100644
index 0000000..8f7d0ca
--- /dev/null
+++ b/scripts/glibcelf.py
@@ -0,0 +1,1135 @@
+#!/usr/bin/python3
+# ELF support functionality for Python.
+# Copyright (C) 2022 Free Software Foundation, Inc.
+# This file is part of the GNU C Library.
+#
+# The GNU C Library is free software; you can redistribute it and/or
+# modify it under the terms of the GNU Lesser General Public
+# License as published by the Free Software Foundation; either
+# version 2.1 of the License, or (at your option) any later version.
+#
+# The GNU C Library 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
+# Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with the GNU C Library; if not, see
+# <https://www.gnu.org/licenses/>.
+
+"""Basic ELF parser.
+
+Use Image.readfile(path) to read an ELF file into memory and begin
+parsing it.
+
+"""
+
+import collections
+import enum
+import struct
+
+class _OpenIntEnum(enum.IntEnum):
+    """Integer enumeration that supports arbitrary int values."""
+    @classmethod
+    def _missing_(cls, value):
+        # See enum.IntFlag._create_pseudo_member_.  This allows
+        # creating of enum constants with arbitrary integer values.
+        pseudo_member = int.__new__(cls, value)
+        pseudo_member._name_ = None
+        pseudo_member._value_ = value
+        return pseudo_member
+
+    def __repr__(self):
+        name = self._name_
+        if name is not None:
+            # The names have prefixes like SHT_, implying their type.
+            return name
+        return '{}({})'.format(self.__class__.__name__, self._value_)
+
+    def __str__(self):
+        name = self._name_
+        if name is not None:
+            return name
+        return str(self._value_)
+
+class ElfClass(_OpenIntEnum):
+    """ELF word size.  Type of EI_CLASS values."""
+    ELFCLASSNONE = 0
+    ELFCLASS32 = 1
+    ELFCLASS64 = 2
+
+class ElfData(_OpenIntEnum):
+    """ELF endianess.  Type of EI_DATA values."""
+    ELFDATANONE = 0
+    ELFDATA2LSB = 1
+    ELFDATA2MSB = 2
+
+class Machine(_OpenIntEnum):
+    """ELF machine type.  Type of values in Ehdr.e_machine field."""
+    EM_NONE = 0
+    EM_M32 = 1
+    EM_SPARC = 2
+    EM_386 = 3
+    EM_68K = 4
+    EM_88K = 5
+    EM_IAMCU = 6
+    EM_860 = 7
+    EM_MIPS = 8
+    EM_S370 = 9
+    EM_MIPS_RS3_LE = 10
+    EM_PARISC = 15
+    EM_VPP500 = 17
+    EM_SPARC32PLUS = 18
+    EM_960 = 19
+    EM_PPC = 20
+    EM_PPC64 = 21
+    EM_S390 = 22
+    EM_SPU = 23
+    EM_V800 = 36
+    EM_FR20 = 37
+    EM_RH32 = 38
+    EM_RCE = 39
+    EM_ARM = 40
+    EM_FAKE_ALPHA = 41
+    EM_SH = 42
+    EM_SPARCV9 = 43
+    EM_TRICORE = 44
+    EM_ARC = 45
+    EM_H8_300 = 46
+    EM_H8_300H = 47
+    EM_H8S = 48
+    EM_H8_500 = 49
+    EM_IA_64 = 50
+    EM_MIPS_X = 51
+    EM_COLDFIRE = 52
+    EM_68HC12 = 53
+    EM_MMA = 54
+    EM_PCP = 55
+    EM_NCPU = 56
+    EM_NDR1 = 57
+    EM_STARCORE = 58
+    EM_ME16 = 59
+    EM_ST100 = 60
+    EM_TINYJ = 61
+    EM_X86_64 = 62
+    EM_PDSP = 63
+    EM_PDP10 = 64
+    EM_PDP11 = 65
+    EM_FX66 = 66
+    EM_ST9PLUS = 67
+    EM_ST7 = 68
+    EM_68HC16 = 69
+    EM_68HC11 = 70
+    EM_68HC08 = 71
+    EM_68HC05 = 72
+    EM_SVX = 73
+    EM_ST19 = 74
+    EM_VAX = 75
+    EM_CRIS = 76
+    EM_JAVELIN = 77
+    EM_FIREPATH = 78
+    EM_ZSP = 79
+    EM_MMIX = 80
+    EM_HUANY = 81
+    EM_PRISM = 82
+    EM_AVR = 83
+    EM_FR30 = 84
+    EM_D10V = 85
+    EM_D30V = 86
+    EM_V850 = 87
+    EM_M32R = 88
+    EM_MN10300 = 89
+    EM_MN10200 = 90
+    EM_PJ = 91
+    EM_OPENRISC = 92
+    EM_ARC_COMPACT = 93
+    EM_XTENSA = 94
+    EM_VIDEOCORE = 95
+    EM_TMM_GPP = 96
+    EM_NS32K = 97
+    EM_TPC = 98
+    EM_SNP1K = 99
+    EM_ST200 = 100
+    EM_IP2K = 101
+    EM_MAX = 102
+    EM_CR = 103
+    EM_F2MC16 = 104
+    EM_MSP430 = 105
+    EM_BLACKFIN = 106
+    EM_SE_C33 = 107
+    EM_SEP = 108
+    EM_ARCA = 109
+    EM_UNICORE = 110
+    EM_EXCESS = 111
+    EM_DXP = 112
+    EM_ALTERA_NIOS2 = 113
+    EM_CRX = 114
+    EM_XGATE = 115
+    EM_C166 = 116
+    EM_M16C = 117
+    EM_DSPIC30F = 118
+    EM_CE = 119
+    EM_M32C = 120
+    EM_TSK3000 = 131
+    EM_RS08 = 132
+    EM_SHARC = 133
+    EM_ECOG2 = 134
+    EM_SCORE7 = 135
+    EM_DSP24 = 136
+    EM_VIDEOCORE3 = 137
+    EM_LATTICEMICO32 = 138
+    EM_SE_C17 = 139
+    EM_TI_C6000 = 140
+    EM_TI_C2000 = 141
+    EM_TI_C5500 = 142
+    EM_TI_ARP32 = 143
+    EM_TI_PRU = 144
+    EM_MMDSP_PLUS = 160
+    EM_CYPRESS_M8C = 161
+    EM_R32C = 162
+    EM_TRIMEDIA = 163
+    EM_QDSP6 = 164
+    EM_8051 = 165
+    EM_STXP7X = 166
+    EM_NDS32 = 167
+    EM_ECOG1X = 168
+    EM_MAXQ30 = 169
+    EM_XIMO16 = 170
+    EM_MANIK = 171
+    EM_CRAYNV2 = 172
+    EM_RX = 173
+    EM_METAG = 174
+    EM_MCST_ELBRUS = 175
+    EM_ECOG16 = 176
+    EM_CR16 = 177
+    EM_ETPU = 178
+    EM_SLE9X = 179
+    EM_L10M = 180
+    EM_K10M = 181
+    EM_AARCH64 = 183
+    EM_AVR32 = 185
+    EM_STM8 = 186
+    EM_TILE64 = 187
+    EM_TILEPRO = 188
+    EM_MICROBLAZE = 189
+    EM_CUDA = 190
+    EM_TILEGX = 191
+    EM_CLOUDSHIELD = 192
+    EM_COREA_1ST = 193
+    EM_COREA_2ND = 194
+    EM_ARCV2 = 195
+    EM_OPEN8 = 196
+    EM_RL78 = 197
+    EM_VIDEOCORE5 = 198
+    EM_78KOR = 199
+    EM_56800EX = 200
+    EM_BA1 = 201
+    EM_BA2 = 202
+    EM_XCORE = 203
+    EM_MCHP_PIC = 204
+    EM_INTELGT = 205
+    EM_KM32 = 210
+    EM_KMX32 = 211
+    EM_EMX16 = 212
+    EM_EMX8 = 213
+    EM_KVARC = 214
+    EM_CDP = 215
+    EM_COGE = 216
+    EM_COOL = 217
+    EM_NORC = 218
+    EM_CSR_KALIMBA = 219
+    EM_Z80 = 220
+    EM_VISIUM = 221
+    EM_FT32 = 222
+    EM_MOXIE = 223
+    EM_AMDGPU = 224
+    EM_RISCV = 243
+    EM_BPF = 247
+    EM_CSKY = 252
+    EM_NUM = 253
+    EM_ALPHA = 0x9026
+
+class Et(_OpenIntEnum):
+    """ELF file type.  Type of ET_* values and the Ehdr.e_type field."""
+    ET_NONE = 0
+    ET_REL = 1
+    ET_EXEC = 2
+    ET_DYN = 3
+    ET_CORE = 4
+
+class Shn(_OpenIntEnum):
+    """ELF reserved section indices."""
+    SHN_UNDEF = 0
+    SHN_BEFORE = 0xff00
+    SHN_AFTER = 0xff01
+    SHN_ABS = 0xfff1
+    SHN_COMMON = 0xfff2
+    SHN_XINDEX = 0xffff
+
+class ShnMIPS(enum.Enum):
+    """Supplemental SHN_* constants for EM_MIPS."""
+    SHN_MIPS_ACOMMON = 0xff00
+    SHN_MIPS_TEXT = 0xff01
+    SHN_MIPS_DATA = 0xff02
+    SHN_MIPS_SCOMMON = 0xff03
+    SHN_MIPS_SUNDEFINED = 0xff04
+
+class ShnPARISC(enum.Enum):
+    """Supplemental SHN_* constants for EM_PARISC."""
+    SHN_PARISC_ANSI_COMMON = 0xff00
+    SHN_PARISC_HUGE_COMMON = 0xff01
+
+class Sht(_OpenIntEnum):
+    """ELF section types.  Type of SHT_* values."""
+    SHT_NULL = 0
+    SHT_PROGBITS = 1
+    SHT_SYMTAB = 2
+    SHT_STRTAB = 3
+    SHT_RELA = 4
+    SHT_HASH = 5
+    SHT_DYNAMIC = 6
+    SHT_NOTE = 7
+    SHT_NOBITS = 8
+    SHT_REL = 9
+    SHT_SHLIB = 10
+    SHT_DYNSYM = 11
+    SHT_INIT_ARRAY = 14
+    SHT_FINI_ARRAY = 15
+    SHT_PREINIT_ARRAY = 16
+    SHT_GROUP = 17
+    SHT_SYMTAB_SHNDX = 18
+    SHT_GNU_ATTRIBUTES = 0x6ffffff5
+    SHT_GNU_HASH = 0x6ffffff6
+    SHT_GNU_LIBLIST = 0x6ffffff7
+    SHT_CHECKSUM = 0x6ffffff8
+    SHT_SUNW_move = 0x6ffffffa
+    SHT_SUNW_COMDAT = 0x6ffffffb
+    SHT_SUNW_syminfo = 0x6ffffffc
+    SHT_GNU_verdef = 0x6ffffffd
+    SHT_GNU_verneed = 0x6ffffffe
+    SHT_GNU_versym = 0x6fffffff
+
+class ShtALPHA(enum.Enum):
+    """Supplemental SHT_* constants for EM_ALPHA."""
+    SHT_ALPHA_DEBUG = 0x70000001
+    SHT_ALPHA_REGINFO = 0x70000002
+
+class ShtARM(enum.Enum):
+    """Supplemental SHT_* constants for EM_ARM."""
+    SHT_ARM_EXIDX = 0x70000001
+    SHT_ARM_PREEMPTMAP = 0x70000002
+    SHT_ARM_ATTRIBUTES = 0x70000003
+
+class ShtCSKY(enum.Enum):
+    """Supplemental SHT_* constants for EM_CSKY."""
+    SHT_CSKY_ATTRIBUTES = 0x70000001
+
+class ShtIA_64(enum.Enum):
+    """Supplemental SHT_* constants for EM_IA_64."""
+    SHT_IA_64_EXT = 0x70000000
+    SHT_IA_64_UNWIND = 0x70000001
+
+class ShtMIPS(enum.Enum):
+    """Supplemental SHT_* constants for EM_MIPS."""
+    SHT_MIPS_LIBLIST = 0x70000000
+    SHT_MIPS_MSYM = 0x70000001
+    SHT_MIPS_CONFLICT = 0x70000002
+    SHT_MIPS_GPTAB = 0x70000003
+    SHT_MIPS_UCODE = 0x70000004
+    SHT_MIPS_DEBUG = 0x70000005
+    SHT_MIPS_REGINFO = 0x70000006
+    SHT_MIPS_PACKAGE = 0x70000007
+    SHT_MIPS_PACKSYM = 0x70000008
+    SHT_MIPS_RELD = 0x70000009
+    SHT_MIPS_IFACE = 0x7000000b
+    SHT_MIPS_CONTENT = 0x7000000c
+    SHT_MIPS_OPTIONS = 0x7000000d
+    SHT_MIPS_SHDR = 0x70000010
+    SHT_MIPS_FDESC = 0x70000011
+    SHT_MIPS_EXTSYM = 0x70000012
+    SHT_MIPS_DENSE = 0x70000013
+    SHT_MIPS_PDESC = 0x70000014
+    SHT_MIPS_LOCSYM = 0x70000015
+    SHT_MIPS_AUXSYM = 0x70000016
+    SHT_MIPS_OPTSYM = 0x70000017
+    SHT_MIPS_LOCSTR = 0x70000018
+    SHT_MIPS_LINE = 0x70000019
+    SHT_MIPS_RFDESC = 0x7000001a
+    SHT_MIPS_DELTASYM = 0x7000001b
+    SHT_MIPS_DELTAINST = 0x7000001c
+    SHT_MIPS_DELTACLASS = 0x7000001d
+    SHT_MIPS_DWARF = 0x7000001e
+    SHT_MIPS_DELTADECL = 0x7000001f
+    SHT_MIPS_SYMBOL_LIB = 0x70000020
+    SHT_MIPS_EVENTS = 0x70000021
+    SHT_MIPS_TRANSLATE = 0x70000022
+    SHT_MIPS_PIXIE = 0x70000023
+    SHT_MIPS_XLATE = 0x70000024
+    SHT_MIPS_XLATE_DEBUG = 0x70000025
+    SHT_MIPS_WHIRL = 0x70000026
+    SHT_MIPS_EH_REGION = 0x70000027
+    SHT_MIPS_XLATE_OLD = 0x70000028
+    SHT_MIPS_PDR_EXCEPTION = 0x70000029
+    SHT_MIPS_XHASH = 0x7000002b
+
+class ShtPARISC(enum.Enum):
+    """Supplemental SHT_* constants for EM_PARISC."""
+    SHT_PARISC_EXT = 0x70000000
+    SHT_PARISC_UNWIND = 0x70000001
+    SHT_PARISC_DOC = 0x70000002
+
+class Pf(enum.IntFlag):
+    """Program header flags.  Type of Phdr.p_flags values."""
+    PF_X = 1
+    PF_W = 2
+    PF_R = 4
+
+class PfARM(enum.IntFlag):
+    """Supplemental PF_* flags for EM_ARM."""
+    PF_ARM_SB = 0x10000000
+    PF_ARM_PI = 0x20000000
+    PF_ARM_ABS = 0x40000000
+
+class PfPARISC(enum.IntFlag):
+    """Supplemental PF_* flags for EM_PARISC."""
+    PF_HP_PAGE_SIZE = 0x00100000
+    PF_HP_FAR_SHARED = 0x00200000
+    PF_HP_NEAR_SHARED = 0x00400000
+    PF_HP_CODE = 0x01000000
+    PF_HP_MODIFY = 0x02000000
+    PF_HP_LAZYSWAP = 0x04000000
+    PF_HP_SBP = 0x08000000
+
+class PfIA_64(enum.IntFlag):
+    """Supplemental PF_* flags for EM_IA_64."""
+    PF_IA_64_NORECOV = 0x80000000
+
+class PfMIPS(enum.IntFlag):
+    """Supplemental PF_* flags for EM_MIPS."""
+    PF_MIPS_LOCAL = 0x10000000
+
+class Shf(enum.IntFlag):
+    """Section flags.  Type of Shdr.sh_type values."""
+    SHF_WRITE = 1 << 0
+    SHF_ALLOC = 1 << 1
+    SHF_EXECINSTR = 1 << 2
+    SHF_MERGE = 1 << 4
+    SHF_STRINGS = 1 << 5
+    SHF_INFO_LINK = 1 << 6
+    SHF_LINK_ORDER = 1 << 7
+    SHF_OS_NONCONFORMING = 256
+    SHF_GROUP = 1 << 9
+    SHF_TLS = 1 << 10
+    SHF_COMPRESSED = 1 << 11
+    SHF_GNU_RETAIN = 1 << 21
+    SHF_ORDERED = 1 << 30
+    SHF_EXCLUDE = 1 << 31
+
+class ShfALPHA(enum.IntFlag):
+    """Supplemental SHF_* constants for EM_ALPHA."""
+    SHF_ALPHA_GPREL = 0x10000000
+
+class ShfARM(enum.IntFlag):
+    """Supplemental SHF_* constants for EM_ARM."""
+    SHF_ARM_ENTRYSECT = 0x10000000
+    SHF_ARM_COMDEF = 0x80000000
+
+class ShfIA_64(enum.IntFlag):
+    """Supplemental SHF_* constants for EM_IA_64."""
+    SHF_IA_64_SHORT  = 0x10000000
+    SHF_IA_64_NORECOV = 0x20000000
+
+class ShfMIPS(enum.IntFlag):
+    """Supplemental SHF_* constants for EM_MIPS."""
+    SHF_MIPS_GPREL = 0x10000000
+    SHF_MIPS_MERGE = 0x20000000
+    SHF_MIPS_ADDR = 0x40000000
+    SHF_MIPS_STRINGS = 0x80000000
+    SHF_MIPS_NOSTRIP = 0x08000000
+    SHF_MIPS_LOCAL = 0x04000000
+    SHF_MIPS_NAMES = 0x02000000
+    SHF_MIPS_NODUPE = 0x01000000
+
+class ShfPARISC(enum.IntFlag):
+    """Supplemental SHF_* constants for EM_PARISC."""
+    SHF_PARISC_SHORT = 0x20000000
+    SHF_PARISC_HUGE = 0x40000000
+    SHF_PARISC_SBP = 0x80000000
+
+class Stb(_OpenIntEnum):
+    """ELF symbol binding type."""
+    STB_LOCAL = 0
+    STB_GLOBAL = 1
+    STB_WEAK = 2
+    STB_GNU_UNIQUE = 10
+    STB_MIPS_SPLIT_COMMON = 13
+
+class Stt(_OpenIntEnum):
+    """ELF symbol type."""
+    STT_NOTYPE = 0
+    STT_OBJECT = 1
+    STT_FUNC = 2
+    STT_SECTION = 3
+    STT_FILE = 4
+    STT_COMMON = 5
+    STT_TLS = 6
+    STT_GNU_IFUNC = 10
+
+class SttARM(enum.Enum):
+    """Supplemental STT_* constants for EM_ARM."""
+    STT_ARM_TFUNC = 13
+    STT_ARM_16BIT = 15
+
+class SttPARISC(enum.Enum):
+    """Supplemental STT_* constants for EM_PARISC."""
+    STT_HP_OPAQUE = 11
+    STT_HP_STUB = 12
+    STT_PARISC_MILLICODE = 13
+
+class SttSPARC(enum.Enum):
+    """Supplemental STT_* constants for EM_SPARC."""
+    STT_SPARC_REGISTER = 13
+
+class SttX86_64(enum.Enum):
+    """Supplemental STT_* constants for EM_X86_64."""
+    SHT_X86_64_UNWIND = 0x70000001
+
+class Pt(_OpenIntEnum):
+    """ELF program header types.  Type of Phdr.p_type."""
+    PT_NULL = 0
+    PT_LOAD = 1
+    PT_DYNAMIC = 2
+    PT_INTERP = 3
+    PT_NOTE = 4
+    PT_SHLIB = 5
+    PT_PHDR = 6
+    PT_TLS = 7
+    PT_NUM = 8
+    PT_GNU_EH_FRAME = 0x6474e550
+    PT_GNU_STACK = 0x6474e551
+    PT_GNU_RELRO = 0x6474e552
+    PT_GNU_PROPERTY = 0x6474e553
+    PT_SUNWBSS = 0x6ffffffa
+    PT_SUNWSTACK = 0x6ffffffb
+
+class PtARM(enum.Enum):
+    """Supplemental PT_* constants for EM_ARM."""
+    PT_ARM_EXIDX = 0x70000001
+
+class PtIA_64(enum.Enum):
+    """Supplemental PT_* constants for EM_IA_64."""
+    PT_IA_64_HP_OPT_ANOT = 0x60000012
+    PT_IA_64_HP_HSL_ANOT = 0x60000013
+    PT_IA_64_HP_STACK = 0x60000014
+    PT_IA_64_ARCHEXT = 0x70000000
+    PT_IA_64_UNWIND = 0x70000001
+
+class PtMIPS(enum.Enum):
+    """Supplemental PT_* constants for EM_MIPS."""
+    PT_MIPS_REGINFO = 0x70000000
+    PT_MIPS_RTPROC = 0x70000001
+    PT_MIPS_OPTIONS = 0x70000002
+    PT_MIPS_ABIFLAGS = 0x70000003
+
+class PtPARISC(enum.Enum):
+    """Supplemental PT_* constants for EM_PARISC."""
+    PT_HP_TLS = 0x60000000
+    PT_HP_CORE_NONE = 0x60000001
+    PT_HP_CORE_VERSION = 0x60000002
+    PT_HP_CORE_KERNEL = 0x60000003
+    PT_HP_CORE_COMM = 0x60000004
+    PT_HP_CORE_PROC = 0x60000005
+    PT_HP_CORE_LOADABLE = 0x60000006
+    PT_HP_CORE_STACK = 0x60000007
+    PT_HP_CORE_SHM = 0x60000008
+    PT_HP_CORE_MMF = 0x60000009
+    PT_HP_PARALLEL = 0x60000010
+    PT_HP_FASTBIND = 0x60000011
+    PT_HP_OPT_ANNOT = 0x60000012
+    PT_HP_HSL_ANNOT = 0x60000013
+    PT_HP_STACK = 0x60000014
+    PT_PARISC_ARCHEXT = 0x70000000
+    PT_PARISC_UNWIND = 0x70000001
+
+class Dt(_OpenIntEnum):
+    """ELF dynamic segment tags.  Type of Dyn.d_val."""
+    DT_NULL = 0
+    DT_NEEDED = 1
+    DT_PLTRELSZ = 2
+    DT_PLTGOT = 3
+    DT_HASH = 4
+    DT_STRTAB = 5
+    DT_SYMTAB = 6
+    DT_RELA = 7
+    DT_RELASZ = 8
+    DT_RELAENT = 9
+    DT_STRSZ = 10
+    DT_SYMENT = 11
+    DT_INIT = 12
+    DT_FINI = 13
+    DT_SONAME = 14
+    DT_RPATH = 15
+    DT_SYMBOLIC = 16
+    DT_REL = 17
+    DT_RELSZ = 18
+    DT_RELENT = 19
+    DT_PLTREL = 20
+    DT_DEBUG = 21
+    DT_TEXTREL = 22
+    DT_JMPREL = 23
+    DT_BIND_NOW = 24
+    DT_INIT_ARRAY = 25
+    DT_FINI_ARRAY = 26
+    DT_INIT_ARRAYSZ = 27
+    DT_FINI_ARRAYSZ = 28
+    DT_RUNPATH = 29
+    DT_FLAGS = 30
+    DT_PREINIT_ARRAY = 32
+    DT_PREINIT_ARRAYSZ = 33
+    DT_SYMTAB_SHNDX = 34
+    DT_GNU_PRELINKED = 0x6ffffdf5
+    DT_GNU_CONFLICTSZ = 0x6ffffdf6
+    DT_GNU_LIBLISTSZ = 0x6ffffdf7
+    DT_CHECKSUM = 0x6ffffdf8
+    DT_PLTPADSZ = 0x6ffffdf9
+    DT_MOVEENT = 0x6ffffdfa
+    DT_MOVESZ = 0x6ffffdfb
+    DT_FEATURE_1 = 0x6ffffdfc
+    DT_POSFLAG_1 = 0x6ffffdfd
+    DT_SYMINSZ = 0x6ffffdfe
+    DT_SYMINENT = 0x6ffffdff
+    DT_GNU_HASH = 0x6ffffef5
+    DT_TLSDESC_PLT = 0x6ffffef6
+    DT_TLSDESC_GOT = 0x6ffffef7
+    DT_GNU_CONFLICT = 0x6ffffef8
+    DT_GNU_LIBLIST = 0x6ffffef9
+    DT_CONFIG = 0x6ffffefa
+    DT_DEPAUDIT = 0x6ffffefb
+    DT_AUDIT = 0x6ffffefc
+    DT_PLTPAD = 0x6ffffefd
+    DT_MOVETAB = 0x6ffffefe
+    DT_SYMINFO = 0x6ffffeff
+    DT_VERSYM = 0x6ffffff0
+    DT_RELACOUNT = 0x6ffffff9
+    DT_RELCOUNT = 0x6ffffffa
+    DT_FLAGS_1 = 0x6ffffffb
+    DT_VERDEF = 0x6ffffffc
+    DT_VERDEFNUM = 0x6ffffffd
+    DT_VERNEED = 0x6ffffffe
+    DT_VERNEEDNUM = 0x6fffffff
+    DT_AUXILIARY = 0x7ffffffd
+    DT_FILTER = 0x7fffffff
+
+class DtAARCH64(enum.Enum):
+    """Supplemental DT_* constants for EM_AARCH64."""
+    DT_AARCH64_BTI_PLT = 0x70000001
+    DT_AARCH64_PAC_PLT = 0x70000003
+    DT_AARCH64_VARIANT_PCS = 0x70000005
+
+class DtALPHA(enum.Enum):
+    """Supplemental DT_* constants for EM_ALPHA."""
+    DT_ALPHA_PLTRO = 0x70000000
+
+class DtALTERA_NIOS2(enum.Enum):
+    """Supplemental DT_* constants for EM_ALTERA_NIOS2."""
+    DT_NIOS2_GP = 0x70000002
+
+class DtIA_64(enum.Enum):
+    """Supplemental DT_* constants for EM_IA_64."""
+    DT_IA_64_PLT_RESERVE = 0x70000000
+
+class DtMIPS(enum.Enum):
+    """Supplemental DT_* constants for EM_MIPS."""
+    DT_MIPS_RLD_VERSION = 0x70000001
+    DT_MIPS_TIME_STAMP = 0x70000002
+    DT_MIPS_ICHECKSUM = 0x70000003
+    DT_MIPS_IVERSION = 0x70000004
+    DT_MIPS_FLAGS = 0x70000005
+    DT_MIPS_BASE_ADDRESS = 0x70000006
+    DT_MIPS_MSYM = 0x70000007
+    DT_MIPS_CONFLICT = 0x70000008
+    DT_MIPS_LIBLIST = 0x70000009
+    DT_MIPS_LOCAL_GOTNO = 0x7000000a
+    DT_MIPS_CONFLICTNO = 0x7000000b
+    DT_MIPS_LIBLISTNO = 0x70000010
+    DT_MIPS_SYMTABNO = 0x70000011
+    DT_MIPS_UNREFEXTNO = 0x70000012
+    DT_MIPS_GOTSYM = 0x70000013
+    DT_MIPS_HIPAGENO = 0x70000014
+    DT_MIPS_RLD_MAP = 0x70000016
+    DT_MIPS_DELTA_CLASS = 0x70000017
+    DT_MIPS_DELTA_CLASS_NO = 0x70000018
+    DT_MIPS_DELTA_INSTANCE = 0x70000019
+    DT_MIPS_DELTA_INSTANCE_NO = 0x7000001a
+    DT_MIPS_DELTA_RELOC = 0x7000001b
+    DT_MIPS_DELTA_RELOC_NO = 0x7000001c
+    DT_MIPS_DELTA_SYM = 0x7000001d
+    DT_MIPS_DELTA_SYM_NO = 0x7000001e
+    DT_MIPS_DELTA_CLASSSYM = 0x70000020
+    DT_MIPS_DELTA_CLASSSYM_NO = 0x70000021
+    DT_MIPS_CXX_FLAGS = 0x70000022
+    DT_MIPS_PIXIE_INIT = 0x70000023
+    DT_MIPS_SYMBOL_LIB = 0x70000024
+    DT_MIPS_LOCALPAGE_GOTIDX = 0x70000025
+    DT_MIPS_LOCAL_GOTIDX = 0x70000026
+    DT_MIPS_HIDDEN_GOTIDX = 0x70000027
+    DT_MIPS_PROTECTED_GOTIDX = 0x70000028
+    DT_MIPS_OPTIONS = 0x70000029
+    DT_MIPS_INTERFACE = 0x7000002a
+    DT_MIPS_DYNSTR_ALIGN = 0x7000002b
+    DT_MIPS_INTERFACE_SIZE = 0x7000002c
+    DT_MIPS_RLD_TEXT_RESOLVE_ADDR = 0x7000002d
+    DT_MIPS_PERF_SUFFIX = 0x7000002e
+    DT_MIPS_COMPACT_SIZE = 0x7000002f
+    DT_MIPS_GP_VALUE = 0x70000030
+    DT_MIPS_AUX_DYNAMIC = 0x70000031
+    DT_MIPS_PLTGOT = 0x70000032
+    DT_MIPS_RWPLT = 0x70000034
+    DT_MIPS_RLD_MAP_REL = 0x70000035
+    DT_MIPS_XHASH = 0x70000036
+
+class DtPPC(enum.Enum):
+    """Supplemental DT_* constants for EM_PPC."""
+    DT_PPC_GOT = 0x70000000
+    DT_PPC_OPT = 0x70000001
+
+class DtPPC64(enum.Enum):
+    """Supplemental DT_* constants for EM_PPC64."""
+    DT_PPC64_GLINK = 0x70000000
+    DT_PPC64_OPD = 0x70000001
+    DT_PPC64_OPDSZ = 0x70000002
+    DT_PPC64_OPT = 0x70000003
+
+class DtSPARC(enum.Enum):
+    """Supplemental DT_* constants for EM_SPARC."""
+    DT_SPARC_REGISTER = 0x70000001
+
+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
+
+
+__all__ = [name for name in dir() if name[0].isupper()]