1/*-
2 * Copyright (c) 2006,2008 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 <assert.h>
28#include <gelf.h>
29#include <libelf.h>
30#include <stdlib.h>
31
32#include "_libelf.h"
33
34ELFTC_VCSID("$Id: libelf_ehdr.c,v 1.3 2020/05/18 06:46:23 jsg Exp $");
35
36/*
37 * Retrieve counts for sections, phdrs and the section string table index
38 * from section header #0 of the ELF object.
39 */
40static int
41_libelf_load_extended(Elf *e, int ec, uint64_t shoff, uint16_t phnum,
42    uint16_t strndx)
43{
44	size_t fsz;
45	Elf_Scn *scn;
46	uint32_t shtype;
47	_libelf_translator_function *xlator;
48
49	assert(STAILQ_EMPTY(&e->e_u.e_elf.e_scn));
50
51	fsz = _libelf_fsize(ELF_T_SHDR, ec, e->e_version, 1);
52	assert(fsz > 0);
53
54	if (shoff + fsz < shoff) {	/* Numeric overflow. */
55		LIBELF_SET_ERROR(HEADER, 0);
56		return (0);
57	}
58
59	if ((uint64_t) e->e_rawsize < shoff + fsz) {
60		LIBELF_SET_ERROR(HEADER, 0);
61		return (0);
62	}
63
64	if ((scn = _libelf_allocate_scn(e, (size_t) 0)) == NULL)
65		return (0);
66
67	xlator = _libelf_get_translator(ELF_T_SHDR, ELF_TOMEMORY, ec,
68	    _libelf_elfmachine(e));
69	(*xlator)((unsigned char *) &scn->s_shdr, sizeof(scn->s_shdr),
70	    (unsigned char *) e->e_rawfile + shoff, (size_t) 1,
71	    e->e_byteorder != LIBELF_PRIVATE(byteorder));
72
73#define	GET_SHDR_MEMBER(M) ((ec == ELFCLASS32) ? scn->s_shdr.s_shdr32.M : \
74		scn->s_shdr.s_shdr64.M)
75
76	if ((shtype = GET_SHDR_MEMBER(sh_type)) != SHT_NULL) {
77		LIBELF_SET_ERROR(SECTION, 0);
78		return (0);
79	}
80
81	e->e_u.e_elf.e_nscn = (size_t) GET_SHDR_MEMBER(sh_size);
82	e->e_u.e_elf.e_nphdr = (phnum != PN_XNUM) ? phnum :
83	    GET_SHDR_MEMBER(sh_info);
84	e->e_u.e_elf.e_strndx = (strndx != SHN_XINDEX) ? strndx :
85	    GET_SHDR_MEMBER(sh_link);
86#undef	GET_SHDR_MEMBER
87
88	return (1);
89}
90
91#define	EHDR_INIT(E,SZ)	 do {						\
92		Elf##SZ##_Ehdr *eh = (E);				\
93		eh->e_ident[EI_MAG0] = ELFMAG0;				\
94		eh->e_ident[EI_MAG1] = ELFMAG1;				\
95		eh->e_ident[EI_MAG2] = ELFMAG2;				\
96		eh->e_ident[EI_MAG3] = ELFMAG3;				\
97		eh->e_ident[EI_CLASS] = ELFCLASS##SZ;			\
98		eh->e_ident[EI_DATA]  = ELFDATANONE;			\
99		eh->e_ident[EI_VERSION] = LIBELF_PRIVATE(version) & 0xFFU; \
100		eh->e_machine = EM_NONE;				\
101		eh->e_type    = ELF_K_NONE;				\
102		eh->e_version = LIBELF_PRIVATE(version);		\
103	} while (0)
104
105void *
106_libelf_ehdr(Elf *e, int ec, int allocate)
107{
108	void *ehdr;
109	size_t fsz, msz;
110	uint16_t phnum, shnum, strndx;
111	uint64_t shoff;
112	int (*xlator)(unsigned char *_d, size_t _dsz, unsigned char *_s,
113	    size_t _c, int _swap);
114
115	assert(ec == ELFCLASS32 || ec == ELFCLASS64);
116
117	if (e == NULL || e->e_kind != ELF_K_ELF) {
118		LIBELF_SET_ERROR(ARGUMENT, 0);
119		return (NULL);
120	}
121
122	if (e->e_class != ELFCLASSNONE && e->e_class != ec) {
123		LIBELF_SET_ERROR(CLASS, 0);
124		return (NULL);
125	}
126
127	if (e->e_version != EV_CURRENT) {
128		LIBELF_SET_ERROR(VERSION, 0);
129		return (NULL);
130	}
131
132	if (e->e_class == ELFCLASSNONE)
133		e->e_class = ec;
134
135	if (ec == ELFCLASS32)
136		ehdr = (void *) e->e_u.e_elf.e_ehdr.e_ehdr32;
137	else
138		ehdr = (void *) e->e_u.e_elf.e_ehdr.e_ehdr64;
139
140	if (ehdr != NULL)	/* already have a translated ehdr */
141		return (ehdr);
142
143	fsz = _libelf_fsize(ELF_T_EHDR, ec, e->e_version, (size_t) 1);
144	assert(fsz > 0);
145
146	if (e->e_cmd != ELF_C_WRITE && e->e_rawsize < (off_t) fsz) {
147		LIBELF_SET_ERROR(HEADER, 0);
148		return (NULL);
149	}
150
151	if ((msz = _libelf_msize(ELF_T_EHDR, ec, EV_CURRENT)) == 0)
152		return (NULL);
153
154	if ((ehdr = calloc((size_t) 1, msz)) == NULL) {
155		LIBELF_SET_ERROR(RESOURCE, 0);
156		return (NULL);
157	}
158
159	if (ec == ELFCLASS32) {
160		e->e_u.e_elf.e_ehdr.e_ehdr32 = ehdr;
161		EHDR_INIT(ehdr,32);
162	} else {
163		e->e_u.e_elf.e_ehdr.e_ehdr64 = ehdr;
164		EHDR_INIT(ehdr,64);
165	}
166
167	if (allocate)
168		e->e_flags |= ELF_F_DIRTY;
169
170	if (e->e_cmd == ELF_C_WRITE)
171		return (ehdr);
172
173	xlator = _libelf_get_translator(ELF_T_EHDR, ELF_TOMEMORY, ec,
174	    _libelf_elfmachine(e));
175	(*xlator)((unsigned char*) ehdr, msz, e->e_rawfile, (size_t) 1,
176	    e->e_byteorder != LIBELF_PRIVATE(byteorder));
177
178	if (ec == ELFCLASS32) {
179		phnum = ((Elf32_Ehdr *) ehdr)->e_phnum;
180		shnum = ((Elf32_Ehdr *) ehdr)->e_shnum;
181		shoff = ((Elf32_Ehdr *) ehdr)->e_shoff;
182		strndx = ((Elf32_Ehdr *) ehdr)->e_shstrndx;
183	} else {
184		phnum = ((Elf64_Ehdr *) ehdr)->e_phnum;
185		shnum = ((Elf64_Ehdr *) ehdr)->e_shnum;
186		shoff = ((Elf64_Ehdr *) ehdr)->e_shoff;
187		strndx = ((Elf64_Ehdr *) ehdr)->e_shstrndx;
188	}
189
190	if (shnum >= SHN_LORESERVE ||
191	    (shoff == 0LL && (shnum != 0 || phnum == PN_XNUM ||
192		strndx == SHN_XINDEX))) {
193		LIBELF_SET_ERROR(HEADER, 0);
194		return (NULL);
195	}
196
197	/*
198	 * If extended numbering is being used, read the correct
199	 * number of sections and program header entries.
200	 */
201	if ((shnum == 0 && shoff != 0) || phnum == PN_XNUM || strndx == SHN_XINDEX) {
202		if (_libelf_load_extended(e, ec, shoff, phnum, strndx) == 0)
203			return (NULL);
204	} else {
205		/* not using extended numbering */
206		e->e_u.e_elf.e_nphdr = phnum;
207		e->e_u.e_elf.e_nscn = shnum;
208		e->e_u.e_elf.e_strndx = strndx;
209	}
210
211	return (ehdr);
212}
213