1  /*-
  2   * Copyright (c) 2006,2008-2010 Joseph Koshy
  3   * All rights reserved.
  4   *
  5   * Redistribution and use in source and binary forms, with or without
  6   * modification, are permitted provided that the following conditions
  7   * are met:
  8   * 1. Redistributions of source code must retain the above copyright
  9   *    notice, this list of conditions and the following disclaimer.
 10   * 2. Redistributions in binary form must reproduce the above copyright
 11   *    notice, this list of conditions and the following disclaimer in the
 12   *    documentation and/or other materials provided with the distribution.
 13   *
 14   * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 15   * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 16   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 17   * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 18   * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 19   * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 20   * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 21   * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 22   * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 23   * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 24   * SUCH DAMAGE.
 25   */
 26  
 27  #include <sys/cdefs.h>
 28  #include <sys/queue.h>
 29  
 30  #include <assert.h>
 31  #include <errno.h>
 32  #include <gelf.h>
 33  #include <libelf.h>
 34  #include <stddef.h>
 35  #include <stdlib.h>
 36  
 37  #include "_libelf.h"
 38  
 39  ELFTC_VCSID("$Id$");
 40  
 41  /*
 42   * Load an ELF section table and create a list of Elf_Scn structures.
 43   */
 44  int
 45  _libelf_load_section_headers(Elf *e, void *ehdr)
 46  {
 47  	Elf_Scn *scn;
 48  	uint64_t shoff;
 49  	Elf32_Ehdr *eh32;
 50  	Elf64_Ehdr *eh64;
 51  	int ec, swapbytes;
 52  	unsigned char *src;
 53  	size_t fsz, i, shnum;
 54  	int (*xlator)(unsigned char *_d, size_t _dsz, unsigned char *_s,
 55  	    size_t _c, int _swap);
 56  
 57  	assert(e != NULL);
 58  	assert(ehdr != NULL);
 59  	assert((e->e_flags & LIBELF_F_SHDRS_LOADED) == 0);
 60  
 61  #define	CHECK_EHDR(E,EH)	do {				\
 62  		if (shoff > e->e_rawsize ||			\
 63  		    fsz != (EH)->e_shentsize ||			\
 64  		    shnum > SIZE_MAX / fsz ||			\
 65  		    fsz * shnum > e->e_rawsize - shoff) {	\
 66  			LIBELF_SET_ERROR(HEADER, 0);		\
 67  			return (0);				\
 68  		}						\
 69  	} while (0)
 70  
 71  	ec = e->e_class;
 72  	fsz = _libelf_fsize(ELF_T_SHDR, ec, e->e_version, (size_t) 1);
 73  	assert(fsz > 0);
 74  
 75  	shnum = e->e_u.e_elf.e_nscn;
 76  
 77  	if (ec == ELFCLASS32) {
 78  		eh32 = (Elf32_Ehdr *) ehdr;
 79  		shoff = (uint64_t) eh32->e_shoff;
 80  		CHECK_EHDR(e, eh32);
 81  	} else {
 82  		eh64 = (Elf64_Ehdr *) ehdr;
 83  		shoff = eh64->e_shoff;
 84  		CHECK_EHDR(e, eh64);
 85  	}
 86  
 87  	xlator = _libelf_get_translator(ELF_T_SHDR, ELF_TOMEMORY, ec);
 88  
 89  	swapbytes = e->e_byteorder != LIBELF_PRIVATE(byteorder);
 90  	src = e->e_rawfile + shoff;
 91  
 92  	/*
 93  	 * If the file is using extended numbering then section #0
 94  	 * would have already been read in.
 95  	 */
 96  
 97  	i = 0;
 98  	if (!STAILQ_EMPTY(&e->e_u.e_elf.e_scn)) {
 99  		assert(STAILQ_FIRST(&e->e_u.e_elf.e_scn) ==
100  		    STAILQ_LAST(&e->e_u.e_elf.e_scn, _Elf_Scn, s_next));
101  
102  		i = 1;
103  		src += fsz;
104  	}
105  
106  	for (; i < shnum; i++, src += fsz) {
107  		if ((scn = _libelf_allocate_scn(e, i)) == NULL)
108  			return (0);
109  
110  		(*xlator)((unsigned char *) &scn->s_shdr, sizeof(scn->s_shdr),
111  		    src, (size_t) 1, swapbytes);
112  
113  		if (ec == ELFCLASS32) {
114  			scn->s_offset = scn->s_rawoff =
115  			    scn->s_shdr.s_shdr32.sh_offset;
116  			scn->s_size = scn->s_shdr.s_shdr32.sh_size;
117  		} else {
118  			scn->s_offset = scn->s_rawoff =
119  			    scn->s_shdr.s_shdr64.sh_offset;
120  			scn->s_size = scn->s_shdr.s_shdr64.sh_size;
121  		}
122  	}
123  
124  	e->e_flags |= LIBELF_F_SHDRS_LOADED;
125  
126  	return (1);
127  }
128  
129  
130  Elf_Scn *
131  elf_getscn(Elf *e, size_t index)
132  {
133  	int ec;
134  	void *ehdr;
135  	Elf_Scn *s;
136  
137  	if (e == NULL || e->e_kind != ELF_K_ELF ||
138  	    ((ec = e->e_class) != ELFCLASS32 && ec != ELFCLASS64)) {
139  		LIBELF_SET_ERROR(ARGUMENT, 0);
140  		return (NULL);
141  	}
142  
143  	if ((ehdr = _libelf_ehdr(e, ec, 0)) == NULL)
144  		return (NULL);
145  
146  	if (e->e_cmd != ELF_C_WRITE &&
147  	    (e->e_flags & LIBELF_F_SHDRS_LOADED) == 0 &&
148  	    _libelf_load_section_headers(e, ehdr) == 0)
149  		return (NULL);
150  
151  	STAILQ_FOREACH(s, &e->e_u.e_elf.e_scn, s_next)
152  		if (s->s_ndx == index)
153  			return (s);
154  
155  	LIBELF_SET_ERROR(ARGUMENT, 0);
156  	return (NULL);
157  }
158  
159  size_t
160  elf_ndxscn(Elf_Scn *s)
161  {
162  	if (s == NULL) {
163  		LIBELF_SET_ERROR(ARGUMENT, 0);
164  		return (SHN_UNDEF);
165  	}
166  	return (s->s_ndx);
167  }
168  
169  Elf_Scn *
170  elf_newscn(Elf *e)
171  {
172  	int ec;
173  	void *ehdr;
174  	Elf_Scn *scn;
175  
176  	if (e == NULL || e->e_kind != ELF_K_ELF) {
177  		LIBELF_SET_ERROR(ARGUMENT, 0);
178  		return (NULL);
179  	}
180  
181  	if ((ec = e->e_class) != ELFCLASS32 && ec != ELFCLASS64) {
182  		LIBELF_SET_ERROR(CLASS, 0);
183  		return (NULL);
184  	}
185  
186  	if ((ehdr = _libelf_ehdr(e, ec, 0)) == NULL)
187  		return (NULL);
188  
189  	/*
190  	 * The application may be asking for a new section descriptor
191  	 * on an ELF object opened with ELF_C_RDWR or ELF_C_READ.  We
192  	 * need to bring in the existing section information before
193  	 * appending a new one to the list.
194  	 *
195  	 * Per the ELF(3) API, an application is allowed to open a
196  	 * file using ELF_C_READ, mess with its internal structure and
197  	 * use elf_update(...,ELF_C_NULL) to compute its new layout.
198  	 */
199  	if (e->e_cmd != ELF_C_WRITE &&
200  	    (e->e_flags & LIBELF_F_SHDRS_LOADED) == 0 &&
201  	    _libelf_load_section_headers(e, ehdr) == 0)
202  		return (NULL);
203  
204  	if (STAILQ_EMPTY(&e->e_u.e_elf.e_scn)) {
205  		assert(e->e_u.e_elf.e_nscn == 0);
206  		if ((scn = _libelf_allocate_scn(e, (size_t) SHN_UNDEF)) ==
207  		    NULL)
208  			return (NULL);
209  		e->e_u.e_elf.e_nscn++;
210  	}
211  
212  	assert(e->e_u.e_elf.e_nscn > 0);
213  
214  	if ((scn = _libelf_allocate_scn(e, e->e_u.e_elf.e_nscn)) == NULL)
215  		return (NULL);
216  
217  	e->e_u.e_elf.e_nscn++;
218  
219  	(void) elf_flagscn(scn, ELF_C_SET, ELF_F_DIRTY);
220  
221  	return (scn);
222  }
223  
224  Elf_Scn *
225  elf_nextscn(Elf *e, Elf_Scn *s)
226  {
227  	if (e == NULL || (e->e_kind != ELF_K_ELF) ||
228  	    (s && s->s_elf != e)) {
229  		LIBELF_SET_ERROR(ARGUMENT, 0);
230  		return (NULL);
231  	}
232  
233  	return (s == NULL ? elf_getscn(e, (size_t) 1) :
234  	    STAILQ_NEXT(s, s_next));
235  }