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) {
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 load_tables();
58 } else {
59 m_status = NullDecoder::file_not_found;
60 }
61 } else {
62 m_status = NullDecoder::out_of_memory;
63 }
64 }
65
66 ElfFile::~ElfFile() {
67 if (m_string_tables != NULL) {
68 delete m_string_tables;
69 }
70
71 if (m_symbol_tables != NULL) {
72 delete m_symbol_tables;
73 }
74
75 if (m_file != NULL) {
76 fclose(m_file);
77 }
78
79 if (m_filepath != NULL) {
80 os::free((void*)m_filepath);
81 }
82
83 if (m_next != NULL) {
84 delete m_next;
85 }
86 };
87
88
89 //Check elf header to ensure the file is valid.
90 bool ElfFile::is_elf_file(Elf_Ehdr& hdr) {
91 return (ELFMAG0 == hdr.e_ident[EI_MAG0] &&
92 ELFMAG1 == hdr.e_ident[EI_MAG1] &&
93 ELFMAG2 == hdr.e_ident[EI_MAG2] &&
94 ELFMAG3 == hdr.e_ident[EI_MAG3] &&
95 ELFCLASSNONE != hdr.e_ident[EI_CLASS] &&
96 ELFDATANONE != hdr.e_ident[EI_DATA]);
97 }
98
99 bool ElfFile::load_tables() {
100 assert(m_file, "file not open");
101 assert(!NullDecoder::is_error(m_status), "already in error");
102
103 // read elf file header
104 if (fread(&m_elfHdr, sizeof(m_elfHdr), 1, m_file) != 1) {
105 m_status = NullDecoder::file_invalid;
106 return false;
107 }
108
109 if (!is_elf_file(m_elfHdr)) {
110 m_status = NullDecoder::file_invalid;
111 return false;
112 }
113
114 // walk elf file's section headers, and load string tables
115 Elf_Shdr shdr;
116 if (!fseek(m_file, m_elfHdr.e_shoff, SEEK_SET)) {
117 if (NullDecoder::is_error(m_status)) return false;
118
119 for (int index = 0; index < m_elfHdr.e_shnum; index ++) {
120 if (fread((void*)&shdr, sizeof(Elf_Shdr), 1, m_file) != 1) {
121 m_status = NullDecoder::file_invalid;
122 return false;
123 }
124 if (shdr.sh_type == SHT_STRTAB) {
125 // string tables
126 ElfStringTable* table = new (std::nothrow) ElfStringTable(m_file, shdr, index);
127 if (table == NULL) {
128 m_status = NullDecoder::out_of_memory;
129 return false;
130 }
131 add_string_table(table);
132 } else if (shdr.sh_type == SHT_SYMTAB || shdr.sh_type == SHT_DYNSYM) {
133 // symbol tables
134 ElfSymbolTable* table = new (std::nothrow) ElfSymbolTable(m_file, shdr);
135 if (table == NULL) {
136 m_status = NullDecoder::out_of_memory;
137 return false;
138 }
139 add_symbol_table(table);
140 }
141 }
142
143 #if defined(PPC64) && !defined(ABI_ELFv2)
144 // Now read the .opd section wich contains the PPC64 function descriptor table.
145 // The .opd section is only available on PPC64 (see for example:
146 // http://refspecs.linuxfoundation.org/LSB_3.1.1/LSB-Core-PPC64/LSB-Core-PPC64/specialsections.html)
147 // so this code should do no harm on other platforms but because of performance reasons we only
148 // execute it on PPC64 platforms.
149 // Notice that we can only find the .opd section after we have successfully read in the string
150 // tables in the previous loop, because we need to query the name of each section which is
151 // contained in one of the string tables (i.e. the one with the index m_elfHdr.e_shstrndx).
152
153 // Reset the file pointer
154 if (fseek(m_file, m_elfHdr.e_shoff, SEEK_SET)) {
155 m_status = NullDecoder::file_invalid;
156 return false;
157 }
158 for (int index = 0; index < m_elfHdr.e_shnum; index ++) {
159 if (fread((void*)&shdr, sizeof(Elf_Shdr), 1, m_file) != 1) {
160 m_status = NullDecoder::file_invalid;
161 return false;
162 }
163 if (m_elfHdr.e_shstrndx != SHN_UNDEF && shdr.sh_type == SHT_PROGBITS) {
164 ElfStringTable* string_table = get_string_table(m_elfHdr.e_shstrndx);
165 if (string_table == NULL) {
166 m_status = NullDecoder::file_invalid;
167 return false;
168 }
169 char buf[8]; // '8' is enough because we only want to read ".opd"
170 if (string_table->string_at(shdr.sh_name, buf, sizeof(buf)) && !strncmp(".opd", buf, 4)) {
171 m_funcDesc_table = new (std::nothrow) ElfFuncDescTable(m_file, shdr, index);
172 if (m_funcDesc_table == NULL) {
173 m_status = NullDecoder::out_of_memory;
174 return false;
175 }
176 break;
177 }
178 }
179 }
180 #endif
181
182 }
183 return true;
184 }
185
186 bool ElfFile::decode(address addr, char* buf, int buflen, int* offset) {
187 // something already went wrong, just give up
188 if (NullDecoder::is_error(m_status)) {
189 return false;
190 }
191 ElfSymbolTable* symbol_table = m_symbol_tables;
192 int string_table_index;
193 int pos_in_string_table;
194 int off = INT_MAX;
195 bool found_symbol = false;
196 while (symbol_table != NULL) {
197 if (symbol_table->lookup(addr, &string_table_index, &pos_in_string_table, &off, m_funcDesc_table)) {
198 found_symbol = true;
199 break;
200 }
201 symbol_table = symbol_table->m_next;
202 }
203 if (!found_symbol) return false;
204
205 ElfStringTable* string_table = get_string_table(string_table_index);
206
207 if (string_table == NULL) {
208 m_status = NullDecoder::file_invalid;
209 return false;
210 }
211 if (offset) *offset = off;
212
213 return string_table->string_at(pos_in_string_table, buf, buflen);
214 }
215
216
217 void ElfFile::add_symbol_table(ElfSymbolTable* table) {
218 if (m_symbol_tables == NULL) {
219 m_symbol_tables = table;
220 } else {
221 table->m_next = m_symbol_tables;
222 m_symbol_tables = table;
223 }
224 }
225
226 void ElfFile::add_string_table(ElfStringTable* table) {
227 if (m_string_tables == NULL) {
228 m_string_tables = table;
229 } else {
230 table->m_next = m_string_tables;
231 m_string_tables = table;
232 }
233 }
234
235 ElfStringTable* ElfFile::get_string_table(int index) {
236 ElfStringTable* p = m_string_tables;
237 while (p != NULL) {
238 if (p->index() == index) return p;
239 p = p->m_next;
240 }
241 return NULL;
242 }
243
244 #ifdef LINUX
245 bool ElfFile::specifies_noexecstack() {
246 Elf_Phdr phdr;
247 if (!m_file) return true;
248
249 if (!fseek(m_file, m_elfHdr.e_phoff, SEEK_SET)) {
250 for (int index = 0; index < m_elfHdr.e_phnum; index ++) {
251 if (fread((void*)&phdr, sizeof(Elf_Phdr), 1, m_file) != 1) {
252 m_status = NullDecoder::file_invalid;
253 return false;
254 }
255 if (phdr.p_type == PT_GNU_STACK) {
256 if (phdr.p_flags == (PF_R | PF_W)) {
257 return true;
258 } else {
259 return false;
260 }
261 }
262 }
263 }
264 // AARCH64 defaults to noexecstack. All others default to execstack.
265 #ifdef AARCH64
266 return true;
267 #else
268 return false;
269 #endif
270 }
271 #endif
272
273 #endif // !_WINDOWS && !__APPLE__