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 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