xref: /titanic_44/usr/src/cmd/sgs/libelf/demo/pcom.c (revision 56b2bdd1f04d465cfe4a95b88ae5cba5884154e4)
1 /*
2  * CDDL HEADER START
3  *
4  * The contents of this file are subject to the terms of the
5  * Common Development and Distribution License (the "License").
6  * You may not use this file except in compliance with the License.
7  *
8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9  * or http://www.opensolaris.org/os/licensing.
10  * See the License for the specific language governing permissions
11  * and limitations under the License.
12  *
13  * When distributing Covered Code, include this CDDL HEADER in each
14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15  * If applicable, add the following below this CDDL HEADER, with the
16  * fields enclosed by brackets "[]" replaced with your own identifying
17  * information: Portions Copyright [yyyy] [name of copyright owner]
18  *
19  * CDDL HEADER END
20  */
21 /*
22  * Copyright (c) 1995, 2010, Oracle and/or its affiliates. All rights reserved.
23  */
24 
25 /*
26  * pcom: Print Comment
27  *
28  * This program demonstrates the use of the libelf interface to
29  * read an ELF file.  pcom will open an ELF file using
30  * elf_begin(ELF_C_READ) and examine search the ELF file
31  * for a .comment section.  If a .comment section is found it's
32  * contents will be displayed on stdout.
33  */
34 
35 #include <stdio.h>
36 #include <libelf.h>
37 #include <gelf.h>
38 #include <fcntl.h>
39 #include <unistd.h>
40 #include <stdlib.h>
41 #include <string.h>
42 
43 
44 static const char	*CommentStr = ".comment";
45 
46 static void
47 print_comment(Elf *elf, const char *file)
48 {
49 	Elf_Scn		*scn = NULL;
50 	GElf_Shdr	shdr;
51 	Elf_Data	*data;
52 	size_t		shstrndx;
53 
54 
55 	(void) printf("%s .comment:\n", file);
56 
57 	if (elf_getshdrstrndx(elf, &shstrndx) == -1) {
58 		(void) fprintf(stderr, "%s: elf_getshdrstrndx() failed: %s\n",
59 		    file, elf_errmsg(0));
60 		return;
61 	}
62 
63 	while ((scn = elf_nextscn(elf, scn)) != NULL) {
64 		/*
65 		 * Do a string compare to examine each section header
66 		 * to see if it is a ".comment" section.  If it is then
67 		 * this is the section we want to process.
68 		 */
69 		if (gelf_getshdr(scn, &shdr) == NULL) {
70 			(void) fprintf(stderr, "%s: elf_getshdr() failed: %s\n",
71 			    file, elf_errmsg(0));
72 			return;
73 		}
74 		if (strcmp(CommentStr, elf_strptr(elf, shstrndx,
75 		    shdr.sh_name)) == 0) {
76 			int	i;
77 			char	*ptr;
78 
79 			/*
80 			 * Get the data associated with the .comment
81 			 * section.
82 			 */
83 			if ((data = elf_getdata(scn, NULL)) == NULL) {
84 				(void) fprintf(stderr,
85 				    "%s: elf_getdata() failed: %s\n",
86 				    file, elf_errmsg(0));
87 				return;
88 			}
89 
90 			/*
91 			 * Data in a .comment section is a list of 'null'
92 			 * terminated strings.  The following will print
93 			 * one string per line.
94 			 */
95 			for (i = 0, ptr = (char *)data->d_buf;
96 			    i < data->d_size; i++)
97 				if (ptr[i]) {
98 					(void) puts(&ptr[i]);
99 					i += strlen(&ptr[i]);
100 				}
101 			(void) putchar('\n');
102 		}
103 	}
104 
105 }
106 
107 static void
108 process_elf(Elf *elf, char *file, int fd, int member)
109 {
110 	Elf_Cmd	cmd;
111 	Elf	*_elf;
112 
113 	switch (elf_kind(elf)) {
114 	case ELF_K_ELF:
115 		/*
116 		 * This is an ELF file, now attempt to find it's
117 		 * .comment section and to display it.
118 		 */
119 		print_comment(elf, file);
120 		break;
121 	case ELF_K_AR:
122 		/*
123 		 * Archives contain multiple ELF files, which can each
124 		 * in turn be examined with libelf.
125 		 *
126 		 * The below loop will iterate over each member of the
127 		 * archive and recursively call process_elf().
128 		 */
129 		cmd = ELF_C_READ;
130 		while ((_elf = elf_begin(fd, cmd, elf)) != NULL) {
131 			Elf_Arhdr	*arhdr;
132 			char		buffer[1024];
133 
134 			arhdr = elf_getarhdr(_elf);
135 
136 			/*
137 			 * Build up file names based off of
138 			 * 'archivename(membername)'.
139 			 */
140 			(void) sprintf(buffer, "%s(%s)", file, arhdr->ar_name);
141 
142 			/*
143 			 * Recursively process the ELF members.
144 			 */
145 			process_elf(_elf, buffer, fd, 1);
146 			cmd = elf_next(_elf);
147 			(void) elf_end(_elf);
148 		}
149 		break;
150 	default:
151 		if (!member)
152 			(void) fprintf(stderr,
153 			    "%s: unexpected elf_kind(): 0x%x\n",
154 			    file, elf_kind(elf));
155 		return;
156 	}
157 }
158 
159 int
160 main(int argc, char **argv)
161 {
162 	int	i;
163 
164 	if (argc < 2) {
165 		(void) printf("usage: %s elf_file ...\n", argv[0]);
166 		return (1);
167 	}
168 
169 	/*
170 	 * Initialize the elf library, must be called before elf_begin()
171 	 * can be called.
172 	 */
173 	if (elf_version(EV_CURRENT) == EV_NONE) {
174 		(void) fprintf(stderr,
175 		    "elf_version() failed: %s\n", elf_errmsg(0));
176 		return (1);
177 	}
178 
179 	for (i = 1; i < argc; i++) {
180 		int	fd;
181 		Elf	*elf;
182 		char	*elf_fname;
183 
184 		elf_fname = argv[i];
185 		if ((fd = open(elf_fname, O_RDONLY)) == -1) {
186 			perror("open");
187 			continue;
188 		}
189 
190 		/*
191 		 * Attempt to open an Elf descriptor Read/Write
192 		 * for each file.
193 		 */
194 		if ((elf = elf_begin(fd, ELF_C_READ, 0)) == NULL) {
195 			(void) fprintf(stderr, "elf_begin() failed: %s\n",
196 			    elf_errmsg(0));
197 			(void) close(fd);
198 			continue;
199 		}
200 
201 		/*
202 		 * Process each elf descriptor.
203 		 */
204 		process_elf(elf, elf_fname, fd, 0);
205 		(void) elf_end(elf);
206 		(void) close(fd);
207 	}
208 
209 	return (0);
210 }
211