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comparison agent/src/os/linux/salibelf.c @ 0:a61af66fc99e jdk7-b24

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author duke
date Sat, 01 Dec 2007 00:00:00 +0000
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children c18cbe5936b8
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-1:000000000000 0:a61af66fc99e
1 /*
2 * Copyright 2003-2006 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
20 * CA 95054 USA or visit www.sun.com if you need additional information or
21 * have any questions.
22 *
23 */
24
25 #include "salibelf.h"
26 #include <stdlib.h>
27 #include <unistd.h>
28
29 extern void print_debug(const char*,...);
30
31 // ELF file parsing helpers. Note that we do *not* use libelf here.
32 int read_elf_header(int fd, ELF_EHDR* ehdr) {
33 if (pread(fd, ehdr, sizeof (ELF_EHDR), 0) != sizeof (ELF_EHDR) ||
34 memcmp(&ehdr->e_ident[EI_MAG0], ELFMAG, SELFMAG) != 0 ||
35 ehdr->e_version != EV_CURRENT) {
36 return 0;
37 }
38 return 1;
39 }
40
41 bool is_elf_file(int fd) {
42 ELF_EHDR ehdr;
43 return read_elf_header(fd, &ehdr);
44 }
45
46 // read program header table of an ELF file
47 ELF_PHDR* read_program_header_table(int fd, ELF_EHDR* hdr) {
48 ELF_PHDR* phbuf = 0;
49 // allocate memory for program header table
50 size_t nbytes = hdr->e_phnum * hdr->e_phentsize;
51
52 if ((phbuf = (ELF_PHDR*) malloc(nbytes)) == NULL) {
53 print_debug("can't allocate memory for reading program header table\n");
54 return NULL;
55 }
56
57 if (pread(fd, phbuf, nbytes, hdr->e_phoff) != nbytes) {
58 print_debug("ELF file is truncated! can't read program header table\n");
59 free(phbuf);
60 return NULL;
61 }
62
63 return phbuf;
64 }
65
66 // read section header table of an ELF file
67 ELF_SHDR* read_section_header_table(int fd, ELF_EHDR* hdr) {
68 ELF_SHDR* shbuf = 0;
69 // allocate memory for section header table
70 size_t nbytes = hdr->e_shnum * hdr->e_shentsize;
71
72 if ((shbuf = (ELF_SHDR*) malloc(nbytes)) == NULL) {
73 print_debug("can't allocate memory for reading section header table\n");
74 return NULL;
75 }
76
77 if (pread(fd, shbuf, nbytes, hdr->e_shoff) != nbytes) {
78 print_debug("ELF file is truncated! can't read section header table\n");
79 free(shbuf);
80 return NULL;
81 }
82
83 return shbuf;
84 }
85
86 // read a particular section's data
87 void* read_section_data(int fd, ELF_EHDR* ehdr, ELF_SHDR* shdr) {
88 void *buf = NULL;
89 if (shdr->sh_type == SHT_NOBITS || shdr->sh_size == 0) {
90 return buf;
91 }
92 if ((buf = calloc(shdr->sh_size, 1)) == NULL) {
93 print_debug("can't allocate memory for reading section data\n");
94 return NULL;
95 }
96 if (pread(fd, buf, shdr->sh_size, shdr->sh_offset) != shdr->sh_size) {
97 free(buf);
98 print_debug("section data read failed\n");
99 return NULL;
100 }
101 return buf;
102 }
103
104 uintptr_t find_base_address(int fd, ELF_EHDR* ehdr) {
105 uintptr_t baseaddr = (uintptr_t)-1;
106 int cnt;
107 ELF_PHDR *phbuf, *phdr;
108
109 // read program header table
110 if ((phbuf = read_program_header_table(fd, ehdr)) == NULL) {
111 goto quit;
112 }
113
114 // the base address of a shared object is the lowest vaddr of
115 // its loadable segments (PT_LOAD)
116 for (phdr = phbuf, cnt = 0; cnt < ehdr->e_phnum; cnt++, phdr++) {
117 if (phdr->p_type == PT_LOAD && phdr->p_vaddr < baseaddr) {
118 baseaddr = phdr->p_vaddr;
119 }
120 }
121
122 quit:
123 if (phbuf) free(phbuf);
124 return baseaddr;
125 }