1 /* $OpenBSD: self_reloc.c,v 1.2 2018/10/20 11:57:43 kettenis Exp $ */
2 /*-
3 * Copyright (c) 2008-2010 Rui Paulo <rpaulo@FreeBSD.org>
4 * All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
16 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
17 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
18 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
19 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
20 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
21 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
22 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
23 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
24 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
25 * SUCH DAMAGE.
26 */
27
28 #include <sys/param.h>
29 #include <machine/reloc.h>
30
31 #if defined(__aarch64__) || defined(__amd64__)
32 #define ELFSIZE 64
33 #define ElfW_Rel Elf64_Rela
34 #define ElfW_Dyn Elf64_Dyn
35 #define ELFW_R_TYPE ELF64_R_TYPE
36 #define ELF_RELA
37 #elif defined(__arm__) || defined(__i386__)
38 #define ELFSIZE 32
39 #define ElfW_Rel Elf32_Rel
40 #define ElfW_Dyn Elf32_Dyn
41 #define ELFW_R_TYPE ELF32_R_TYPE
42 #else
43 #error architecture not supported
44 #endif
45
46 #include <sys/exec_elf.h>
47
48 #if defined(__aarch64__)
49 #define RELOC_TYPE_NONE R_AARCH64_NONE
50 #define RELOC_TYPE_RELATIVE R_AARCH64_RELATIVE
51 #elif defined(__amd64__)
52 #define RELOC_TYPE_NONE R_X86_64_NONE
53 #define RELOC_TYPE_RELATIVE R_X86_64_RELATIVE
54 #elif defined(__arm__)
55 #define RELOC_TYPE_NONE R_ARM_NONE
56 #define RELOC_TYPE_RELATIVE R_ARM_RELATIVE
57 #elif defined(__i386__)
58 #define RELOC_TYPE_NONE R_386_NONE
59 #define RELOC_TYPE_RELATIVE R_386_RELATIVE
60 #endif
61
62 /*
63 * A simple elf relocator.
64 */
65 void
self_reloc(Elf_Addr baseaddr,ElfW_Dyn * dynamic)66 self_reloc(Elf_Addr baseaddr, ElfW_Dyn *dynamic)
67 {
68 Elf_Word relsz, relent;
69 Elf_Addr *newaddr;
70 ElfW_Rel *rel = NULL;
71 ElfW_Dyn *dynp;
72
73 /*
74 * Find the relocation address, its size and the relocation entry.
75 */
76 relsz = 0;
77 relent = 0;
78 for (dynp = dynamic; dynp->d_tag != DT_NULL; dynp++) {
79 switch (dynp->d_tag) {
80 case DT_REL:
81 case DT_RELA:
82 rel = (ElfW_Rel *)(dynp->d_un.d_ptr + baseaddr);
83 break;
84 case DT_RELSZ:
85 case DT_RELASZ:
86 relsz = dynp->d_un.d_val;
87 break;
88 case DT_RELENT:
89 case DT_RELAENT:
90 relent = dynp->d_un.d_val;
91 break;
92 default:
93 break;
94 }
95 }
96
97 /*
98 * Perform the actual relocation. We rely on the object having been
99 * linked at 0, so that the difference between the load and link
100 * address is the same as the load address.
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 newaddr = (Elf_Addr *)(rel->r_offset + baseaddr);
110 #ifdef ELF_RELA
111 /* Addend relative to the base address. */
112 *newaddr = baseaddr + rel->r_addend;
113 #else
114 /* Address relative to the base address. */
115 *newaddr += baseaddr;
116 #endif
117 break;
118 default:
119 /* XXX: do we need other relocations ? */
120 break;
121 }
122 rel = (ElfW_Rel *) ((caddr_t) rel + relent);
123 }
124 }
125