1/*-
2 * Copyright (c) 2006,2008-2011 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 <libelf.h>
28
29#include "_libelf.h"
30
31ELFTC_VCSID("$Id: elf_begin.c 2364 2011-12-28 17:55:25Z jkoshy $");
32
33Elf *
34elf_begin(int fd, Elf_Cmd c, Elf *a)
35{
36	Elf *e;
37
38	e = NULL;
39
40	if (LIBELF_PRIVATE(version) == EV_NONE) {
41		LIBELF_SET_ERROR(SEQUENCE, 0);
42		return (NULL);
43	}
44
45	switch (c) {
46	case ELF_C_NULL:
47		return (NULL);
48
49	case ELF_C_WRITE:
50		/*
51		 * The ELF_C_WRITE command is required to ignore the
52		 * descriptor passed in.
53		 */
54		a = NULL;
55		break;
56
57	case ELF_C_RDWR:
58		if (a != NULL) { /* not allowed for ar(1) archives. */
59			LIBELF_SET_ERROR(ARGUMENT, 0);
60			return (NULL);
61		}
62		/*FALLTHROUGH*/
63	case ELF_C_READ:
64		/*
65		 * Descriptor `a' could be for a regular ELF file, or
66		 * for an ar(1) archive.  If descriptor `a' was opened
67		 * using a valid file descriptor, we need to check if
68		 * the passed in `fd' value matches the original one.
69		 */
70		if (a &&
71		    ((a->e_fd != -1 && a->e_fd != fd) || c != a->e_cmd)) {
72			LIBELF_SET_ERROR(ARGUMENT, 0);
73			return (NULL);
74		}
75		break;
76
77	default:
78		LIBELF_SET_ERROR(ARGUMENT, 0);
79		return (NULL);
80
81	}
82
83	if (a == NULL)
84		e = _libelf_open_object(fd, c, 1);
85	else if (a->e_kind == ELF_K_AR)
86		e = _libelf_ar_open_member(a->e_fd, c, a);
87	else
88		(e = a)->e_activations++;
89
90	return (e);
91}
92