1/* $OpenBSD: self_reloc.c,v 1.1 2021/04/28 19:01:00 drahn 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__) || defined(__riscv)
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#elif defined(__riscv)
61#define RELOC_TYPE_NONE		R_RISCV_NONE
62#define RELOC_TYPE_RELATIVE	R_RISCV_RELATIVE
63#endif
64
65/*
66 * A simple elf relocator.
67 */
68void
69self_reloc(Elf_Addr baseaddr, ElfW_Dyn *dynamic)
70{
71	Elf_Word relsz, relent;
72	Elf_Addr *newaddr;
73	ElfW_Rel *rel = NULL;
74	ElfW_Dyn *dynp;
75
76	/*
77	 * Find the relocation address, its size and the relocation entry.
78	 */
79	relsz = 0;
80	relent = 0;
81	for (dynp = dynamic; dynp->d_tag != DT_NULL; dynp++) {
82		switch (dynp->d_tag) {
83		case DT_REL:
84		case DT_RELA:
85			rel = (ElfW_Rel *)(dynp->d_un.d_ptr + baseaddr);
86			break;
87		case DT_RELSZ:
88		case DT_RELASZ:
89			relsz = dynp->d_un.d_val;
90			break;
91		case DT_RELENT:
92		case DT_RELAENT:
93			relent = dynp->d_un.d_val;
94			break;
95		default:
96			break;
97		}
98	}
99
100	/*
101	 * Perform the actual relocation. We rely on the object having been
102	 * linked at 0, so that the difference between the load and link
103	 * address is the same as the load address.
104	 */
105	for (; relsz > 0; relsz -= relent) {
106		switch (ELFW_R_TYPE(rel->r_info)) {
107		case RELOC_TYPE_NONE:
108			/* No relocation needs be performed. */
109			break;
110
111		case RELOC_TYPE_RELATIVE:
112			newaddr = (Elf_Addr *)(rel->r_offset + baseaddr);
113#ifdef ELF_RELA
114			/* Addend relative to the base address. */
115			*newaddr = baseaddr + rel->r_addend;
116#else
117			/* Address relative to the base address. */
118			*newaddr += baseaddr;
119#endif
120			break;
121		default:
122			/* XXX: do we need other relocations ? */
123			break;
124		}
125		rel = (ElfW_Rel *) ((caddr_t) rel + relent);
126	}
127}
128