1 /*
2 * Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26
27 #if !defined(_WINDOWS) && !defined(__APPLE__)
28
29 #include <string.h>
30 #include <stdio.h>
31 #include <limits.h>
32 #include <new>
33
34 #include "memory/allocation.inline.hpp"
35 #include "utilities/decoder.hpp"
36 #include "utilities/elfFile.hpp"
37 #include "utilities/elfFuncDescTable.hpp"
38 #include "utilities/elfStringTable.hpp"
39 #include "utilities/elfSymbolTable.hpp"
40
41
42 ElfFile::ElfFile(const char* filepath, bool load_tbls) {
43 assert(filepath, "null file path");
44 memset(&m_elfHdr, 0, sizeof(m_elfHdr));
45 m_string_tables = NULL;
46 m_symbol_tables = NULL;
47 m_funcDesc_table = NULL;
48 m_next = NULL;
49 m_status = NullDecoder::no_error;
50
51 int len = strlen(filepath) + 1;
52 m_filepath = (const char*)os::malloc(len * sizeof(char), mtInternal);
53 if (m_filepath != NULL) {
54 strcpy((char*)m_filepath, filepath);
55 m_file = fopen(filepath, "r");
56 if (m_file != NULL) {
57 if (load_tbls) {
58 load_tables();
59 }
60 } else {
61 m_status = NullDecoder::file_not_found;
62 }
63 } else {
64 m_status = NullDecoder::out_of_memory;
65 }
66 }
67
68 ElfFile::~ElfFile() {
69 if (m_string_tables != NULL) {
70 delete m_string_tables;
71 }
72
73 if (m_symbol_tables != NULL) {
74 delete m_symbol_tables;
75 }
76
77 if (m_file != NULL) {
78 fclose(m_file);
79 }
80
81 if (m_filepath != NULL) {
82 os::free((void*)m_filepath);
83 }
84
85 if (m_next != NULL) {
86 delete m_next;
87 }
88 };
89
90
91 //Check elf header to ensure the file is valid.
92 bool ElfFile::is_elf_file(Elf_Ehdr& hdr) {
93 return (ELFMAG0 == hdr.e_ident[EI_MAG0] &&
94 ELFMAG1 == hdr.e_ident[EI_MAG1] &&
95 ELFMAG2 == hdr.e_ident[EI_MAG2] &&
96 ELFMAG3 == hdr.e_ident[EI_MAG3] &&
97 ELFCLASSNONE != hdr.e_ident[EI_CLASS] &&
98 ELFDATANONE != hdr.e_ident[EI_DATA]);
99 }
100
101 bool ElfFile::load_tables() {
102 assert(m_file, "file not open");
103 assert(!NullDecoder::is_error(m_status), "already in error");
104
105 // read elf file header
106 if (fread(&m_elfHdr, sizeof(m_elfHdr), 1, m_file) != 1) {
107 m_status = NullDecoder::file_invalid;
108 return false;
109 }
110
111 if (!is_elf_file(m_elfHdr)) {
112 m_status = NullDecoder::file_invalid;
113 return false;
114 }
115
116 // walk elf file's section headers, and load string tables
117 Elf_Shdr shdr;
118 if (!fseek(m_file, m_elfHdr.e_shoff, SEEK_SET)) {
119 if (NullDecoder::is_error(m_status)) return false;
120
121 for (int index = 0; index < m_elfHdr.e_shnum; index ++) {
122 if (fread((void*)&shdr, sizeof(Elf_Shdr), 1, m_file) != 1) {
123 m_status = NullDecoder::file_invalid;
124 return false;
125 }
126 if (shdr.sh_type == SHT_STRTAB) {
127 // string tables
128 ElfStringTable* table = new (std::nothrow) ElfStringTable(m_file, shdr, index);
129 if (table == NULL) {
130 m_status = NullDecoder::out_of_memory;
131 return false;
132 }
133 add_string_table(table);
134 } else if (shdr.sh_type == SHT_SYMTAB || shdr.sh_type == SHT_DYNSYM) {
135 // symbol tables
136 ElfSymbolTable* table = new (std::nothrow) ElfSymbolTable(m_file, shdr);
137 if (table == NULL) {
138 m_status = NullDecoder::out_of_memory;
139 return false;
140 }
141 add_symbol_table(table);
142 }
143 }
144
145 #if defined(PPC64) && !defined(ABI_ELFv2)
146 // Now read the .opd section wich contains the PPC64 function descriptor table.
147 // The .opd section is only available on PPC64 (see for example:
148 // http://refspecs.linuxfoundation.org/LSB_3.1.1/LSB-Core-PPC64/LSB-Core-PPC64/specialsections.html)
149 // so this code should do no harm on other platforms but because of performance reasons we only
150 // execute it on PPC64 platforms.
151 // Notice that we can only find the .opd section after we have successfully read in the string
152 // tables in the previous loop, because we need to query the name of each section which is
153 // contained in one of the string tables (i.e. the one with the index m_elfHdr.e_shstrndx).
154
155 // Reset the file pointer
156 if (fseek(m_file, m_elfHdr.e_shoff, SEEK_SET)) {
157 m_status = NullDecoder::file_invalid;
158 return false;
159 }
160 for (int index = 0; index < m_elfHdr.e_shnum; index ++) {
161 if (fread((void*)&shdr, sizeof(Elf_Shdr), 1, m_file) != 1) {
162 m_status = NullDecoder::file_invalid;
163 return false;
164 }
165 if (m_elfHdr.e_shstrndx != SHN_UNDEF && shdr.sh_type == SHT_PROGBITS) {
166 ElfStringTable* string_table = get_string_table(m_elfHdr.e_shstrndx);
167 if (string_table == NULL) {
168 m_status = NullDecoder::file_invalid;
169 return false;
170 }
171 char buf[8]; // '8' is enough because we only want to read ".opd"
172 if (string_table->string_at(shdr.sh_name, buf, sizeof(buf)) && !strncmp(".opd", buf, 4)) {
173 m_funcDesc_table = new (std::nothrow) ElfFuncDescTable(m_file, shdr, index);
174 if (m_funcDesc_table == NULL) {
175 m_status = NullDecoder::out_of_memory;
176 return false;
177 }
178 break;
179 }
180 }
181 }
182 #endif
183
184 }
185 return true;
186 }
187
188 bool ElfFile::decode(address addr, char* buf, int buflen, int* offset) {
189 // something already went wrong, just give up
190 if (NullDecoder::is_error(m_status)) {
191 return false;
192 }
193 ElfSymbolTable* symbol_table = m_symbol_tables;
194 int string_table_index;
195 int pos_in_string_table;
196 int off = INT_MAX;
197 bool found_symbol = false;
198 while (symbol_table != NULL) {
199 if (symbol_table->lookup(addr, &string_table_index, &pos_in_string_table, &off, m_funcDesc_table)) {
200 found_symbol = true;
201 break;
202 }
203 symbol_table = symbol_table->m_next;
204 }
205 if (!found_symbol) return false;
206
207 ElfStringTable* string_table = get_string_table(string_table_index);
208
209 if (string_table == NULL) {
210 m_status = NullDecoder::file_invalid;
211 return false;
212 }
213 if (offset) *offset = off;
214
215 return string_table->string_at(pos_in_string_table, buf, buflen);
216 }
217
218
219 void ElfFile::add_symbol_table(ElfSymbolTable* table) {
220 if (m_symbol_tables == NULL) {
221 m_symbol_tables = table;
222 } else {
223 table->m_next = m_symbol_tables;
224 m_symbol_tables = table;
225 }
226 }
227
228 void ElfFile::add_string_table(ElfStringTable* table) {
229 if (m_string_tables == NULL) {
230 m_string_tables = table;
231 } else {
232 table->m_next = m_string_tables;
233 m_string_tables = table;
234 }
235 }
236
237 ElfStringTable* ElfFile::get_string_table(int index) {
238 ElfStringTable* p = m_string_tables;
239 while (p != NULL) {
240 if (p->index() == index) return p;
241 p = p->m_next;
242 }
243 return NULL;
244 }
245
246 #ifdef LINUX
247 bool ElfFile::specifies_noexecstack() {
248 Elf_Phdr phdr;
249 if (!m_file) return true;
250
251 if (!fseek(m_file, m_elfHdr.e_phoff, SEEK_SET)) {
252 for (int index = 0; index < m_elfHdr.e_phnum; index ++) {
253 if (fread((void*)&phdr, sizeof(Elf_Phdr), 1, m_file) != 1) {
254 m_status = NullDecoder::file_invalid;
255 return false;
256 }
257 if (phdr.p_type == PT_GNU_STACK) {
258 if (phdr.p_flags == (PF_R | PF_W)) {
259 return true;
260 } else {
261 return false;
262 }
263 }
264 }
265 }
266 // AARCH64 defaults to noexecstack. All others default to execstack.
267 #ifdef AARCH64
268 return true;
269 #else
270 return false;
271 #endif
272 }
273 #endif
274
275 #endif // !_WINDOWS && !__APPLE__