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