xref: /illumos-gate/usr/src/cmd/file/elf_read.c (revision 24da5b34) 
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 /*	Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T	*/
22 /*	  All Rights Reserved  	*/
23 
24 
25 /*	Copyright (c) 1987, 1988 Microsoft Corporation	*/
26 /*	  All Rights Reserved	*/
27 
28 /*
29  * Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
30  * Use is subject to license terms.
31  */
32 
33 #pragma ident	"%Z%%M%	%I%	%E% SMI"
34 
35 #define	_LARGEFILE64_SOURCE
36 
37 #include <ctype.h>
38 #include <unistd.h>
39 #include <fcntl.h>
40 #include <stdio.h>
41 #include <libelf.h>
42 #include <stdlib.h>
43 #include <limits.h>
44 #include <locale.h>
45 #include <string.h>
46 #include <errno.h>
47 #include <procfs.h>
48 #include <sys/param.h>
49 #include <sys/types.h>
50 #include <sys/stat.h>
51 #include <sys/elf.h>
52 #include <elfcap.h>
53 #include "file.h"
54 #include "elf_read.h"
55 
56 extern const char *File;
57 
58 static int get_class(void);
59 static int get_version(void);
60 static int get_format(void);
61 static int process_shdr(Elf_Info *);
62 static int process_phdr(Elf_Info *);
63 static int file_xlatetom(Elf_Type, char *);
64 static int xlatetom_nhdr(Elf_Nhdr *);
65 static int get_phdr(Elf_Info *, int);
66 static int get_shdr(Elf_Info *, int);
67 
68 static Elf_Ehdr	EI_Ehdr; /* Elf_Ehdr to be stored */
69 static Elf_Shdr	EI_Shdr; /* recent Elf_Shdr to be stored */
70 static Elf_Phdr	EI_Phdr; /* recent Elf_Phdr to be stored */
71 
72 
73 static int
74 get_class(void)
75 {
76 	return (EI_Ehdr.e_ident[EI_CLASS]);
77 }
78 
79 static int
80 get_version(void)
81 {
82 	/* do as what libelf:_elf_config() does */
83 	return (EI_Ehdr.e_ident[EI_VERSION] ?
84 	    EI_Ehdr.e_ident[EI_VERSION] : 1);
85 }
86 
87 static int
88 get_format(void)
89 {
90 	return (EI_Ehdr.e_ident[EI_DATA]);
91 }
92 
93 /*
94  * file_xlatetom:	translate different headers from file
95  * 			representation to memory representaion.
96  */
97 #define	HDRSZ 512
98 static int
99 file_xlatetom(Elf_Type type, char *hdr)
100 {
101 	Elf_Data src, dst;
102 	char *hbuf[HDRSZ];
103 	int version, format;
104 
105 	version = get_version();
106 	format = get_format();
107 
108 	/* will convert only these types */
109 	if (type != ELF_T_EHDR && type != ELF_T_PHDR &&
110 	    type != ELF_T_SHDR && type != ELF_T_WORD &&
111 	    type != ELF_T_CAP)
112 		return (ELF_READ_FAIL);
113 
114 	src.d_buf = (Elf_Void *)hdr;
115 	src.d_type = type;
116 	src.d_version = version;
117 
118 	dst.d_buf = (Elf_Void *)&hbuf;
119 	dst.d_version = EV_CURRENT;
120 
121 	src.d_size = elf_fsize(type, 1, version);
122 	dst.d_size = elf_fsize(type, 1, EV_CURRENT);
123 	if (elf_xlatetom(&dst, &src, format) == NULL)
124 		return (ELF_READ_FAIL);
125 
126 	(void) memcpy(hdr, &hbuf, dst.d_size);
127 	return (ELF_READ_OKAY);
128 }
129 
130 /*
131  * xlatetom_nhdr:	There is no routine to convert Note header
132  * 			so we convert each field of this header.
133  */
134 static int
135 xlatetom_nhdr(Elf_Nhdr *nhdr)
136 {
137 	int r = ELF_READ_FAIL;
138 
139 	r |= file_xlatetom(ELF_T_WORD, (char *)&nhdr->n_namesz);
140 	r |= file_xlatetom(ELF_T_WORD, (char *)&nhdr->n_descsz);
141 	r |= file_xlatetom(ELF_T_WORD, (char *)&nhdr->n_type);
142 	return (r);
143 }
144 
145 /*
146  * elf_read:	reads elf header, program, section headers to
147  * 		collect all information needed for file(1)
148  *		output and stores them in Elf_Info.
149  */
150 int
151 elf_read(int fd, Elf_Info *EI)
152 {
153 	size_t size;
154 	int ret = 1;
155 
156 	Elf_Ehdr *ehdr = &EI_Ehdr;
157 
158 	EI->elffd = fd;
159 	size = sizeof (Elf_Ehdr);
160 
161 	if (pread64(EI->elffd, (void*)ehdr, size, 0) != size)
162 		ret = 0;
163 
164 	if (file_xlatetom(ELF_T_EHDR, (char *)ehdr) == ELF_READ_FAIL)
165 		ret = 0;
166 
167 	if (EI->file == NULL)
168 		return (ELF_READ_FAIL);
169 
170 	EI->type = ehdr->e_type;
171 	EI->machine = ehdr->e_machine;
172 	EI->flags = ehdr->e_flags;
173 
174 	if (ret == 0) {
175 		(void) fprintf(stderr, gettext("%s: %s: can't "
176 		    "read ELF header\n"), File, EI->file);
177 		return (ELF_READ_FAIL);
178 	}
179 	if (process_phdr(EI) == ELF_READ_FAIL)
180 		return (ELF_READ_FAIL);
181 
182 	/* We don't need section info for core files */
183 	if (ehdr->e_type != ET_CORE)
184 		if (process_shdr(EI) == ELF_READ_FAIL)
185 			return (ELF_READ_FAIL);
186 
187 	return (ELF_READ_OKAY);
188 }
189 
190 /*
191  * get_phdr:	reads program header of specified index.
192  */
193 static int
194 get_phdr(Elf_Info *EI, int inx)
195 {
196 	off_t off = 0;
197 	size_t size;
198 	Elf_Ehdr *ehdr = &EI_Ehdr;
199 
200 	if (inx >= ehdr->e_phnum)
201 		return (ELF_READ_FAIL);
202 
203 	size = sizeof (Elf_Phdr);
204 	off = (off_t)ehdr->e_phoff + (inx * size);
205 	if (pread64(EI->elffd, (void *)&EI_Phdr, size, off) != size)
206 		return (ELF_READ_FAIL);
207 
208 	if (file_xlatetom(ELF_T_PHDR, (char *)&EI_Phdr) == ELF_READ_FAIL)
209 		return (ELF_READ_FAIL);
210 
211 	return (ELF_READ_OKAY);
212 }
213 
214 /*
215  * get_shdr:	reads section header of specified index.
216  */
217 static int
218 get_shdr(Elf_Info *EI, int inx)
219 {
220 	off_t off = 0;
221 	size_t size;
222 	Elf_Ehdr *ehdr = &EI_Ehdr;
223 
224 	if (inx >= ehdr->e_shnum)
225 		return (ELF_READ_FAIL);
226 
227 	size = sizeof (Elf_Shdr);
228 	off = (off_t)ehdr->e_shoff + (inx * size);
229 
230 	if (pread64(EI->elffd, (void *)&EI_Shdr, size, off) != size)
231 		return (ELF_READ_FAIL);
232 
233 	if (file_xlatetom(ELF_T_SHDR, (char *)&EI_Shdr) == ELF_READ_FAIL)
234 		return (ELF_READ_FAIL);
235 
236 	return (ELF_READ_OKAY);
237 }
238 
239 /*
240  * process_phdr:	Read Program Headers and see if it is a core
241  *			file of either new or (pre-restructured /proc)
242  * 			type, read the name of the file that dumped this
243  *			core, else see if this is a dynamically linked.
244  */
245 static int
246 process_phdr(Elf_Info *EI)
247 {
248 	register int inx;
249 
250 	Elf_Nhdr Nhdr, *nhdr;	/* note header just read */
251 	Elf_Phdr	*phdr = &EI_Phdr;
252 
253 	int class;
254 	int ntype;
255 	size_t nsz, nmsz, dsz;
256 	off_t offset;
257 	char *psinfo, *fname;
258 
259 	nsz = sizeof (Elf_Nhdr);
260 	nhdr = &Nhdr;
261 	class = get_class();
262 	for (inx = 0; inx < EI_Ehdr.e_phnum; inx++) {
263 		if (get_phdr(EI, inx) == ELF_READ_FAIL)
264 			return (ELF_READ_FAIL);
265 
266 		/* read the note if it is a core */
267 		if (phdr->p_type == PT_NOTE &&
268 		    EI_Ehdr.e_type == ET_CORE) {
269 			/*
270 			 * If the next segment is also a note, use it instead.
271 			 */
272 			if (get_phdr(EI, inx+1) == ELF_READ_FAIL)
273 				return (ELF_READ_FAIL);
274 			if (phdr->p_type != PT_NOTE) {
275 				/* read the first phdr back */
276 				if (get_phdr(EI, inx) == ELF_READ_FAIL)
277 					return (ELF_READ_FAIL);
278 			}
279 			offset = phdr->p_offset;
280 			if (pread64(EI->elffd, (void *)nhdr, nsz, offset)
281 				!= nsz)
282 				return (ELF_READ_FAIL);
283 
284 			/* Translate the ELF note header */
285 			if (xlatetom_nhdr(nhdr) == ELF_READ_FAIL)
286 				return (ELF_READ_FAIL);
287 
288 			ntype = nhdr->n_type;
289 			nmsz = nhdr->n_namesz;
290 			dsz = nhdr->n_descsz;
291 
292 			offset += nsz + ((nmsz + 0x03) & ~0x3);
293 			if ((psinfo = malloc(dsz)) == NULL) {
294 				int err = errno;
295 				(void) fprintf(stderr, gettext("%s: malloc "
296 				    "failed: %s\n"), File, strerror(err));
297 				exit(1);
298 			}
299 			if (pread64(EI->elffd, psinfo, dsz, offset) != dsz)
300 				return (ELF_READ_FAIL);
301 			/*
302 			 * We want to print the string contained
303 			 * in psinfo->pr_fname[], where 'psinfo'
304 			 * is either an old NT_PRPSINFO structure
305 			 * or a new NT_PSINFO structure.
306 			 *
307 			 * Old core files have only type NT_PRPSINFO.
308 			 * New core files have type NT_PSINFO.
309 			 *
310 			 * These structures are also different by
311 			 * virtue of being contained in a core file
312 			 * of either 32-bit or 64-bit type.
313 			 *
314 			 * To further complicate matters, we ourself
315 			 * might be compiled either 32-bit or 64-bit.
316 			 *
317 			 * For these reason, we just *know* the offsets of
318 			 * pr_fname[] into the four different structures
319 			 * here, regardless of how we are compiled.
320 			 */
321 			if (class == ELFCLASS32) {
322 				/* 32-bit core file, 32-bit structures */
323 				if (ntype == NT_PSINFO)
324 					fname = psinfo + 88;
325 				else	/* old: NT_PRPSINFO */
326 					fname = psinfo + 84;
327 			} else if (class == ELFCLASS64) {
328 				/* 64-bit core file, 64-bit structures */
329 				if (ntype == NT_PSINFO)
330 					fname = psinfo + 136;
331 				else	/* old: NT_PRPSINFO */
332 					fname = psinfo + 120;
333 			}
334 			EI->core_type = (ntype == NT_PRPSINFO)?
335 					EC_OLDCORE : EC_NEWCORE;
336 			(void) memcpy(EI->fname, fname, strlen(fname));
337 			free(psinfo);
338 		}
339 		if (phdr->p_type == PT_DYNAMIC) {
340 			EI->dynamic = B_TRUE;
341 		}
342 	}
343 	return (ELF_READ_OKAY);
344 }
345 
346 /*
347  * process_shdr:	Read Section Headers to attempt to get HW/SW
348  *			capabilities by looking at the SUNW_cap
349  *			section and set string in Elf_Info.
350  *			Also look for symbol tables and debug
351  *			information sections. Set the "stripped" field
352  *			in Elf_Info with corresponding flags.
353  */
354 static int
355 process_shdr(Elf_Info *EI)
356 {
357 	int 		capn, mac;
358 	int 		i, j, idx;
359 	off_t		cap_off;
360 	size_t		csize;
361 	char		*section_name;
362 	Elf_Cap 	Chdr;
363 	Elf_Shdr	*shdr = &EI_Shdr;
364 
365 
366 	csize = sizeof (Elf_Cap);
367 	mac = EI_Ehdr.e_machine;
368 
369 	/* if there are no sections, return success anyway */
370 	if (EI_Ehdr.e_shoff == 0 && EI_Ehdr.e_shnum == 0)
371 		return (ELF_READ_OKAY);
372 
373 	/* read section names from String Section */
374 	if (get_shdr(EI, EI_Ehdr.e_shstrndx) == ELF_READ_FAIL)
375 		return (ELF_READ_FAIL);
376 
377 	if ((section_name = malloc(shdr->sh_size)) == NULL)
378 		return (ELF_READ_FAIL);
379 
380 	if (pread64(EI->elffd, section_name, shdr->sh_size, shdr->sh_offset)
381 	    != shdr->sh_size)
382 		return (ELF_READ_FAIL);
383 
384 	/* read all the sections and process them */
385 	for (idx = 1, i = 0; i < EI_Ehdr.e_shnum; idx++, i++) {
386 		char *str;
387 
388 		if (get_shdr(EI, i) == ELF_READ_FAIL)
389 			return (ELF_READ_FAIL);
390 
391 		if (shdr->sh_type == SHT_NULL) {
392 			idx--;
393 			continue;
394 		}
395 
396 		cap_off = shdr->sh_offset;
397 		if (shdr->sh_type == SHT_SUNW_cap) {
398 			if (shdr->sh_size == 0 || shdr->sh_entsize == 0) {
399 				(void) fprintf(stderr, ELF_ERR_ELFCAP1,
400 				    File, EI->file);
401 				return (ELF_READ_FAIL);
402 			}
403 			capn = (shdr->sh_size / shdr->sh_entsize);
404 			for (j = 0; j < capn; j++) {
405 				/*
406 				 * read cap and xlate the values
407 				 */
408 				if (pread64(EI->elffd, &Chdr, csize, cap_off)
409 					!= csize ||
410 					file_xlatetom(ELF_T_CAP, (char *)&Chdr)
411 					    == 0) {
412 					(void) fprintf(stderr, ELF_ERR_ELFCAP2,
413 					    File, EI->file);
414 					return (ELF_READ_FAIL);
415 				}
416 
417 				if (Chdr.c_tag != CA_SUNW_NULL) {
418 					(void) cap_val2str(Chdr.c_tag,
419 						    Chdr.c_un.c_val,
420 						    EI->cap_str,
421 						    sizeof (EI->cap_str),
422 						    0, mac);
423 				}
424 				cap_off += csize;
425 			}
426 		}
427 
428 		/*
429 		 * Definition time:
430 		 *	- "not stripped" means that an executable file
431 		 *	contains a Symbol Table (.symtab)
432 		 *	- "stripped" means that an executable file
433 		 *	does not contain a Symbol Table.
434 		 * When strip -l or strip -x is run, it strips the
435 		 * debugging information (.line section name (strip -l),
436 		 * .line, .debug*, .stabs*, .dwarf* section names
437 		 * and SHT_SUNW_DEBUGSTR and SHT_SUNW_DEBUG
438 		 * section types (strip -x), however the Symbol
439 		 * Table will still be present.
440 		 * Therefore, if
441 		 *	- No Symbol Table present, then report
442 		 *		"stripped"
443 		 *	- Symbol Table present with debugging
444 		 *	information (line number or debug section names,
445 		 *	or SHT_SUNW_DEBUGSTR or SHT_SUNW_DEBUG section
446 		 *	types) then report:
447 		 *		"not stripped"
448 		 *	- Symbol Table present with no debugging
449 		 *	information (line number or debug section names,
450 		 *	or SHT_SUNW_DEBUGSTR or SHT_SUNW_DEBUG section
451 		 *	types) then report:
452 		 *		"not stripped, no debugging information
453 		 *		available"
454 		 */
455 		if ((EI->stripped & E_NOSTRIP) == E_NOSTRIP)
456 			continue;
457 
458 		if (!(EI->stripped & E_SYMTAB) &&
459 		    (shdr->sh_type == SHT_SYMTAB)) {
460 			EI->stripped |= E_SYMTAB;
461 			continue;
462 		}
463 
464 		str = &section_name[shdr->sh_name];
465 
466 		if (!(EI->stripped & E_DBGINF) &&
467 		    ((shdr->sh_type == SHT_SUNW_DEBUG) ||
468 		    (shdr->sh_type == SHT_SUNW_DEBUGSTR) ||
469 		    (is_in_list(str)))) {
470 			EI->stripped |= E_DBGINF;
471 		}
472 	}
473 	free(section_name);
474 
475 	return (ELF_READ_OKAY);
476 }
477