• Home
  • Line#
  • Scopes#
  • Navigate#
  • Raw
  • Download
1#!/usr/bin/env python3
2# Copyright 2020 The Pigweed Authors
3#
4# Licensed under the Apache License, Version 2.0 (the "License"); you may not
5# use this file except in compliance with the License. You may obtain a copy of
6# the License at
7#
8#     https://www.apache.org/licenses/LICENSE-2.0
9#
10# Unless required by applicable law or agreed to in writing, software
11# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
12# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
13# License for the specific language governing permissions and limitations under
14# the License.
15"""Tests the ELF reader Python module."""
16
17import io
18import os
19import re
20import unittest
21
22from pw_tokenizer import elf_reader
23
24# Output from the following command:
25#
26#   readelf -WS elf_reader_test_binary.elf
27#
28TEST_READELF_OUTPUT = ("""
29There are 33 section headers, starting at offset 0x1758:
30
31Section Headers:
32  [Nr] Name              Type            Address          Off    Size   ES Flg Lk Inf Al
33  [ 0]                   NULL            0000000000000000 000000 000000 00      0   0  0
34  [ 1] .interp           PROGBITS        0000000000000238 000238 00001c 00   A  0   0  1
35  [ 2] .note.ABI-tag     NOTE            0000000000000254 000254 000020 00   A  0   0  4
36  [ 3] .note.gnu.build-id NOTE            0000000000000274 000274 000024 00   A  0   0  4
37  [ 4] .dynsym           DYNSYM          0000000000000298 000298 0000a8 18   A  5   1  8
38  [ 5] .dynstr           STRTAB          0000000000000340 000340 00009b 00   A  0   0  1
39  [ 6] .gnu.hash         GNU_HASH        00000000000003e0 0003e0 00001c 00   A  4   0  8
40  [ 7] .gnu.version      VERSYM          00000000000003fc 0003fc 00000e 02   A  4   0  2
41  [ 8] .gnu.version_r    VERNEED         000000000000040c 00040c 000020 00   A  5   1  4
42  [ 9] .rela.dyn         RELA            0000000000000430 000430 0000d8 18   A  4   0  8
43  [10] .rela.plt         RELA            0000000000000508 000508 000018 18  AI  4  12  8
44  [11] .init             PROGBITS        0000000000000520 000520 000017 00  AX  0   0  4
45  [12] .plt              PROGBITS        0000000000000540 000540 000020 10  AX  0   0 16
46  [13] .text             PROGBITS        0000000000000560 000560 000151 00  AX  0   0 16
47  [14] .fini             PROGBITS        00000000000006b4 0006b4 000009 00  AX  0   0  4
48  [15] .rodata           PROGBITS        00000000000006c0 0006c0 000004 04  AM  0   0  4
49  [16] .test_section_1   PROGBITS        00000000000006d0 0006d0 000010 00   A  0   0 16
50  [17] .test_section_2   PROGBITS        00000000000006e0 0006e0 000004 00   A  0   0  4
51  [18] .eh_frame         X86_64_UNWIND   00000000000006e8 0006e8 0000d4 00   A  0   0  8
52  [19] .eh_frame_hdr     X86_64_UNWIND   00000000000007bc 0007bc 00002c 00   A  0   0  4
53  [20] .fini_array       FINI_ARRAY      0000000000001d80 000d80 000008 08  WA  0   0  8
54  [21] .init_array       INIT_ARRAY      0000000000001d88 000d88 000008 08  WA  0   0  8
55  [22] .dynamic          DYNAMIC         0000000000001d90 000d90 000220 10  WA  5   0  8
56  [23] .got              PROGBITS        0000000000001fb0 000fb0 000030 00  WA  0   0  8
57  [24] .got.plt          PROGBITS        0000000000001fe0 000fe0 000020 00  WA  0   0  8
58  [25] .data             PROGBITS        0000000000002000 001000 000010 00  WA  0   0  8
59  [26] .tm_clone_table   PROGBITS        0000000000002010 001010 000000 00  WA  0   0  8
60  [27] .bss              NOBITS          0000000000002010 001010 000001 00  WA  0   0  1
61  [28] .comment          PROGBITS        0000000000000000 001010 00001d 01  MS  0   0  1
62  [29] .note.gnu.gold-version NOTE            0000000000000000 001030 00001c 00      0   0  4
63  [30] .symtab           SYMTAB          0000000000000000 001050 000390 18     31  21  8
64  [31] .strtab           STRTAB          0000000000000000 0013e0 000227 00      0   0  1
65  [32] .shstrtab         STRTAB          0000000000000000 001607 00014a 00      0   0  1
66Key to Flags:
67  W (write), A (alloc), X (execute), M (merge), S (strings), I (info),
68  L (link order), O (extra OS processing required), G (group), T (TLS),
69  C (compressed), x (unknown), o (OS specific), E (exclude),
70  l (large), p (processor specific)
71""")
72
73TEST_ELF_PATH = os.path.join(os.path.dirname(__file__),
74                             'elf_reader_test_binary.elf')
75
76
77class ElfReaderTest(unittest.TestCase):
78    """Tests the elf_reader.Elf class."""
79    def setUp(self):
80        super().setUp()
81        self._elf_file = open(TEST_ELF_PATH, 'rb')
82        self._elf = elf_reader.Elf(self._elf_file)
83
84    def tearDown(self):
85        super().tearDown()
86        self._elf_file.close()
87
88    def _section(self, name):
89        return next(self._elf.sections_with_name(name))
90
91    def test_readelf_comparison_using_the_readelf_binary(self):
92        """Compares elf_reader to readelf's output."""
93
94        parse_readelf_output = re.compile(r'\s+'
95                                          r'\[\s*(?P<number>\d+)\]\s+'
96                                          r'(?P<name>\.\S*)?\s+'
97                                          r'(?P<type>\S+)\s+'
98                                          r'(?P<addr>[0-9a-fA-F]+)\s+'
99                                          r'(?P<offset>[0-9a-fA-F]+)\s+'
100                                          r'(?P<size>[0-9a-fA-F]+)\s+')
101
102        readelf_sections = []
103        for number, name, _, addr, offset, size in parse_readelf_output.findall(
104                TEST_READELF_OUTPUT):
105            readelf_sections.append((
106                int(number),
107                name or '',
108                int(addr, 16),
109                int(offset, 16),
110                int(size, 16),
111            ))
112
113        self.assertEqual(len(readelf_sections), 33)
114        self.assertEqual(len(readelf_sections), len(self._elf.sections))
115
116        for (index,
117             section), readelf_section in zip(enumerate(self._elf.sections),
118                                              readelf_sections):
119            readelf_index, name, address, offset, size = readelf_section
120
121            self.assertEqual(index, readelf_index)
122            self.assertEqual(section.name, name)
123            self.assertEqual(section.address, address)
124            self.assertEqual(section.offset, offset)
125            self.assertEqual(section.size, size)
126
127    def test_dump_single_section(self):
128        self.assertEqual(self._elf.dump_section_contents(r'\.test_section_1'),
129                         b'You cannot pass\0')
130        self.assertEqual(self._elf.dump_section_contents(r'\.test_section_2'),
131                         b'\xef\xbe\xed\xfe')
132
133    def test_dump_multiple_sections(self):
134        if (self._section('.test_section_1').address <
135                self._section('.test_section_2').address):
136            contents = b'You cannot pass\0\xef\xbe\xed\xfe'
137        else:
138            contents = b'\xef\xbe\xed\xfeYou cannot pass\0'
139
140        self.assertIn(self._elf.dump_section_contents(r'.test_section_\d'),
141                      contents)
142
143    def test_read_values(self):
144        address = self._section('.test_section_1').address
145        self.assertEqual(self._elf.read_value(address), b'You cannot pass')
146
147        int32_address = self._section('.test_section_2').address
148        self.assertEqual(self._elf.read_value(int32_address, 4),
149                         b'\xef\xbe\xed\xfe')
150
151    def test_read_string(self):
152        bytes_io = io.BytesIO(
153            b'This is a null-terminated string\0No terminator!')
154        self.assertEqual(elf_reader.read_c_string(bytes_io),
155                         b'This is a null-terminated string')
156        self.assertEqual(elf_reader.read_c_string(bytes_io), b'No terminator!')
157        self.assertEqual(elf_reader.read_c_string(bytes_io), b'')
158
159    def test_compatible_file_for_elf(self):
160        self.assertTrue(elf_reader.compatible_file(self._elf_file))
161        self.assertTrue(elf_reader.compatible_file(io.BytesIO(b'\x7fELF')))
162
163    def test_compatible_file_for_elf_start_at_offset(self):
164        self._elf_file.seek(13)  # Seek ahead to get out of sync
165        self.assertTrue(elf_reader.compatible_file(self._elf_file))
166        self.assertEqual(13, self._elf_file.tell())
167
168    def test_compatible_file_for_invalid_elf(self):
169        self.assertFalse(elf_reader.compatible_file(io.BytesIO(b'\x7fELVESF')))
170
171
172def _archive_file(data: bytes) -> bytes:
173    return ('FILE ID 90123456'
174            'MODIFIED 012'
175            'OWNER '
176            'GROUP '
177            'MODE 678'
178            f'{len(data):10}'  # File size -- the only part that's needed.
179            '`\n'.encode() + data)
180
181
182class ArchiveTest(unittest.TestCase):
183    """Tests reading from archive files."""
184    def setUp(self):
185        super().setUp()
186
187        with open(TEST_ELF_PATH, 'rb') as fd:
188            self._elf_data = fd.read()
189
190        self._archive_entries = b'blah', b'hello', self._elf_data
191
192        self._archive_data = elf_reader.ARCHIVE_MAGIC + b''.join(
193            _archive_file(f) for f in self._archive_entries)
194        self._archive = io.BytesIO(self._archive_data)
195
196    def test_compatible_file_for_archive(self):
197        self.assertTrue(elf_reader.compatible_file(io.BytesIO(b'!<arch>\n')))
198        self.assertTrue(elf_reader.compatible_file(self._archive))
199
200    def test_compatible_file_for_invalid_archive(self):
201        self.assertFalse(elf_reader.compatible_file(io.BytesIO(b'!<arch>')))
202
203    def test_iterate_over_files(self):
204        for expected, size in zip(self._archive_entries,
205                                  elf_reader.files_in_archive(self._archive)):
206            self.assertEqual(expected, self._archive.read(size))
207
208    def test_iterate_over_empty_archive(self):
209        with self.assertRaises(StopIteration):
210            next(iter(elf_reader.files_in_archive(io.BytesIO(b'!<arch>\n'))))
211
212    def test_iterate_over_invalid_archive(self):
213        with self.assertRaises(elf_reader.FileDecodeError):
214            for _ in elf_reader.files_in_archive(
215                    io.BytesIO(b'!<arch>blah blahblah')):
216                pass
217
218    def test_extra_newline_after_entry_is_ignored(self):
219        archive = io.BytesIO(elf_reader.ARCHIVE_MAGIC +
220                             _archive_file(self._elf_data) + b'\n' +
221                             _archive_file(self._elf_data))
222
223        for size in elf_reader.files_in_archive(archive):
224            self.assertEqual(self._elf_data, archive.read(size))
225
226    def test_two_extra_newlines_parsing_fails(self):
227        archive = io.BytesIO(elf_reader.ARCHIVE_MAGIC +
228                             _archive_file(self._elf_data) + b'\n\n' +
229                             _archive_file(self._elf_data))
230
231        with self.assertRaises(elf_reader.FileDecodeError):
232            for size in elf_reader.files_in_archive(archive):
233                self.assertEqual(self._elf_data, archive.read(size))
234
235    def test_iterate_over_archive_with_invalid_size(self):
236        data = elf_reader.ARCHIVE_MAGIC + _archive_file(b'$' * 3210)
237        file = io.BytesIO(data)
238
239        # Iterate over the file normally.
240        for size in elf_reader.files_in_archive(file):
241            self.assertEqual(b'$' * 3210, file.read(size))
242
243        # Replace the size with a hex number, which is not valid.
244        with self.assertRaises(elf_reader.FileDecodeError):
245            for _ in elf_reader.files_in_archive(
246                    io.BytesIO(data.replace(b'3210', b'0x99'))):
247                pass
248
249    def test_elf_reader_dump_single_section(self):
250        elf = elf_reader.Elf(self._archive)
251        self.assertEqual(elf.dump_section_contents(r'\.test_section_1'),
252                         b'You cannot pass\0')
253        self.assertEqual(elf.dump_section_contents(r'\.test_section_2'),
254                         b'\xef\xbe\xed\xfe')
255
256    def test_elf_reader_read_values(self):
257        elf = elf_reader.Elf(self._archive)
258        address = next(elf.sections_with_name('.test_section_1')).address
259        self.assertEqual(elf.read_value(address), b'You cannot pass')
260
261        int32_address = next(elf.sections_with_name('.test_section_2')).address
262        self.assertEqual(elf.read_value(int32_address, 4), b'\xef\xbe\xed\xfe')
263
264
265if __name__ == '__main__':
266    unittest.main()
267