self_reloc.c revision 283505 
1/*-
2 * Copyright (c) 2008-2010 Rui Paulo <rpaulo@FreeBSD.org>
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__FBSDID("$FreeBSD: stable/10/sys/boot/common/self_reloc.c 283505 2015-05-25 01:06:55Z ian $");
29
30#include <sys/types.h>
31#include <elf.h>
32#include <bootstrap.h>
33
34#if defined(__aarch64__)
35#define	ElfW_Rel	Elf64_Rela
36#define	ElfW_Dyn	Elf64_Dyn
37#define	ELFW_R_TYPE	ELF64_R_TYPE
38#define	ELF_RELA
39#elif defined(__arm__) || defined(__i386__)
40#define	ElfW_Rel	Elf32_Rel
41#define	ElfW_Dyn	Elf32_Dyn
42#define	ELFW_R_TYPE	ELF32_R_TYPE
43#elif defined(__amd64__)
44#define	ElfW_Rel	Elf64_Rel
45#define	ElfW_Dyn	Elf64_Dyn
46#define	ELFW_R_TYPE	ELF64_R_TYPE
47#else
48#error architecture not supported
49#endif
50#if defined(__aarch64__)
51#define	RELOC_TYPE_NONE		R_AARCH64_NONE
52#define	RELOC_TYPE_RELATIVE	R_AARCH64_RELATIVE
53#elif defined(__amd64__)
54#define	RELOC_TYPE_NONE		R_X86_64_NONE
55#define	RELOC_TYPE_RELATIVE	R_X86_64_RELATIVE
56#elif defined(__arm__)
57#define	RELOC_TYPE_NONE		R_ARM_NONE
58#define	RELOC_TYPE_RELATIVE	R_ARM_RELATIVE
59#elif defined(__i386__)
60#define	RELOC_TYPE_NONE		R_386_NONE
61#define	RELOC_TYPE_RELATIVE	R_386_RELATIVE
62#endif
63
64/*
65 * A simple elf relocator.
66 */
67void
68self_reloc(Elf_Addr baseaddr, ElfW_Dyn *dynamic)
69{
70	Elf_Word relsz, relent;
71	Elf_Addr *newaddr;
72	ElfW_Rel *rel;
73	ElfW_Dyn *dynp;
74
75	/*
76	 * Find the relocation address, its size and the relocation entry.
77	 */
78	relsz = 0;
79	relent = 0;
80	for (dynp = dynamic; dynp->d_tag != DT_NULL; dynp++) {
81		switch (dynp->d_tag) {
82		case DT_REL:
83		case DT_RELA:
84			rel = (ElfW_Rel *)(dynp->d_un.d_ptr + baseaddr);
85			break;
86		case DT_RELSZ:
87		case DT_RELASZ:
88			relsz = dynp->d_un.d_val;
89			break;
90		case DT_RELENT:
91		case DT_RELAENT:
92			relent = dynp->d_un.d_val;
93			break;
94		default:
95			break;
96		}
97	}
98
99	/*
100	 * Perform the actual relocation.
101	 */
102	for (; relsz > 0; relsz -= relent) {
103		switch (ELFW_R_TYPE(rel->r_info)) {
104		case RELOC_TYPE_NONE:
105			/* No relocation needs be performed. */
106			break;
107
108		case RELOC_TYPE_RELATIVE:
109			/* Address relative to the base address. */
110			newaddr = (Elf_Addr *)(rel->r_offset + baseaddr);
111			*newaddr += baseaddr;
112			/* Add the addend when the ABI uses them */
113#ifdef ELF_RELA
114			*newaddr += rel->r_addend;
115#endif
116			break;
117		default:
118			/* XXX: do we need other relocations ? */
119			break;
120		}
121		rel = (ElfW_Rel *) ((caddr_t) rel + relent);
122	}
123}
124