1 /* Kernel module help for x86. 2 Copyright (C) 2001 Rusty Russell. 3 4 This program is free software; you can redistribute it and/or modify 5 it under the terms of the GNU General Public License as published by 6 the Free Software Foundation; either version 2 of the License, or 7 (at your option) any later version. 8 9 This program is distributed in the hope that it will be useful, 10 but WITHOUT ANY WARRANTY; without even the implied warranty of 11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 12 GNU General Public License for more details. 13 14 You should have received a copy of the GNU General Public License 15 along with this program; if not, write to the Free Software 16 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA 17 */ 18 19 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 20 21 #include <linux/moduleloader.h> 22 #include <linux/elf.h> 23 #include <linux/vmalloc.h> 24 #include <linux/fs.h> 25 #include <linux/string.h> 26 #include <linux/kernel.h> 27 #include <linux/bug.h> 28 #include <linux/mm.h> 29 #include <linux/gfp.h> 30 #include <linux/jump_label.h> 31 #include <linux/random.h> 32 33 #include <asm/page.h> 34 #include <asm/pgtable.h> 35 36 #if 0 37 #define DEBUGP(fmt, ...) \ 38 printk(KERN_DEBUG fmt, ##__VA_ARGS__) 39 #else 40 #define DEBUGP(fmt, ...) \ 41 do { \ 42 if (0) \ 43 printk(KERN_DEBUG fmt, ##__VA_ARGS__); \ 44 } while (0) 45 #endif 46 47 #ifdef CONFIG_RANDOMIZE_BASE 48 static unsigned long module_load_offset; 49 static int randomize_modules = 1; 50 51 /* Mutex protects the module_load_offset. */ 52 static DEFINE_MUTEX(module_kaslr_mutex); 53 54 static int __init parse_nokaslr(char *p) 55 { 56 randomize_modules = 0; 57 return 0; 58 } 59 early_param("nokaslr", parse_nokaslr); 60 61 static unsigned long int get_module_load_offset(void) 62 { 63 if (randomize_modules) { 64 mutex_lock(&module_kaslr_mutex); 65 /* 66 * Calculate the module_load_offset the first time this 67 * code is called. Once calculated it stays the same until 68 * reboot. 69 */ 70 if (module_load_offset == 0) 71 module_load_offset = 72 (get_random_int() % 1024 + 1) * PAGE_SIZE; 73 mutex_unlock(&module_kaslr_mutex); 74 } 75 return module_load_offset; 76 } 77 #else 78 static unsigned long int get_module_load_offset(void) 79 { 80 return 0; 81 } 82 #endif 83 84 void *module_alloc(unsigned long size) 85 { 86 if (PAGE_ALIGN(size) > MODULES_LEN) 87 return NULL; 88 return __vmalloc_node_range(size, 1, 89 MODULES_VADDR + get_module_load_offset(), 90 MODULES_END, GFP_KERNEL | __GFP_HIGHMEM, 91 PAGE_KERNEL_EXEC, NUMA_NO_NODE, 92 __builtin_return_address(0)); 93 } 94 95 #ifdef CONFIG_X86_32 96 int apply_relocate(Elf32_Shdr *sechdrs, 97 const char *strtab, 98 unsigned int symindex, 99 unsigned int relsec, 100 struct module *me) 101 { 102 unsigned int i; 103 Elf32_Rel *rel = (void *)sechdrs[relsec].sh_addr; 104 Elf32_Sym *sym; 105 uint32_t *location; 106 107 DEBUGP("Applying relocate section %u to %u\n", 108 relsec, sechdrs[relsec].sh_info); 109 for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) { 110 /* This is where to make the change */ 111 location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr 112 + rel[i].r_offset; 113 /* This is the symbol it is referring to. Note that all 114 undefined symbols have been resolved. */ 115 sym = (Elf32_Sym *)sechdrs[symindex].sh_addr 116 + ELF32_R_SYM(rel[i].r_info); 117 118 switch (ELF32_R_TYPE(rel[i].r_info)) { 119 case R_386_32: 120 /* We add the value into the location given */ 121 *location += sym->st_value; 122 break; 123 case R_386_PC32: 124 /* Add the value, subtract its position */ 125 *location += sym->st_value - (uint32_t)location; 126 break; 127 default: 128 pr_err("%s: Unknown relocation: %u\n", 129 me->name, ELF32_R_TYPE(rel[i].r_info)); 130 return -ENOEXEC; 131 } 132 } 133 return 0; 134 } 135 #else /*X86_64*/ 136 int apply_relocate_add(Elf64_Shdr *sechdrs, 137 const char *strtab, 138 unsigned int symindex, 139 unsigned int relsec, 140 struct module *me) 141 { 142 unsigned int i; 143 Elf64_Rela *rel = (void *)sechdrs[relsec].sh_addr; 144 Elf64_Sym *sym; 145 void *loc; 146 u64 val; 147 148 DEBUGP("Applying relocate section %u to %u\n", 149 relsec, sechdrs[relsec].sh_info); 150 for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) { 151 /* This is where to make the change */ 152 loc = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr 153 + rel[i].r_offset; 154 155 /* This is the symbol it is referring to. Note that all 156 undefined symbols have been resolved. */ 157 sym = (Elf64_Sym *)sechdrs[symindex].sh_addr 158 + ELF64_R_SYM(rel[i].r_info); 159 160 DEBUGP("type %d st_value %Lx r_addend %Lx loc %Lx\n", 161 (int)ELF64_R_TYPE(rel[i].r_info), 162 sym->st_value, rel[i].r_addend, (u64)loc); 163 164 val = sym->st_value + rel[i].r_addend; 165 166 switch (ELF64_R_TYPE(rel[i].r_info)) { 167 case R_X86_64_NONE: 168 break; 169 case R_X86_64_64: 170 *(u64 *)loc = val; 171 break; 172 case R_X86_64_32: 173 *(u32 *)loc = val; 174 if (val != *(u32 *)loc) 175 goto overflow; 176 break; 177 case R_X86_64_32S: 178 *(s32 *)loc = val; 179 if ((s64)val != *(s32 *)loc) 180 goto overflow; 181 break; 182 case R_X86_64_PC32: 183 val -= (u64)loc; 184 *(u32 *)loc = val; 185 #if 0 186 if ((s64)val != *(s32 *)loc) 187 goto overflow; 188 #endif 189 break; 190 default: 191 pr_err("%s: Unknown rela relocation: %llu\n", 192 me->name, ELF64_R_TYPE(rel[i].r_info)); 193 return -ENOEXEC; 194 } 195 } 196 return 0; 197 198 overflow: 199 pr_err("overflow in relocation type %d val %Lx\n", 200 (int)ELF64_R_TYPE(rel[i].r_info), val); 201 pr_err("`%s' likely not compiled with -mcmodel=kernel\n", 202 me->name); 203 return -ENOEXEC; 204 } 205 #endif 206 207 int module_finalize(const Elf_Ehdr *hdr, 208 const Elf_Shdr *sechdrs, 209 struct module *me) 210 { 211 const Elf_Shdr *s, *text = NULL, *alt = NULL, *locks = NULL, 212 *para = NULL; 213 char *secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset; 214 215 for (s = sechdrs; s < sechdrs + hdr->e_shnum; s++) { 216 if (!strcmp(".text", secstrings + s->sh_name)) 217 text = s; 218 if (!strcmp(".altinstructions", secstrings + s->sh_name)) 219 alt = s; 220 if (!strcmp(".smp_locks", secstrings + s->sh_name)) 221 locks = s; 222 if (!strcmp(".parainstructions", secstrings + s->sh_name)) 223 para = s; 224 } 225 226 if (alt) { 227 /* patch .altinstructions */ 228 void *aseg = (void *)alt->sh_addr; 229 apply_alternatives(aseg, aseg + alt->sh_size); 230 } 231 if (locks && text) { 232 void *lseg = (void *)locks->sh_addr; 233 void *tseg = (void *)text->sh_addr; 234 alternatives_smp_module_add(me, me->name, 235 lseg, lseg + locks->sh_size, 236 tseg, tseg + text->sh_size); 237 } 238 239 if (para) { 240 void *pseg = (void *)para->sh_addr; 241 apply_paravirt(pseg, pseg + para->sh_size); 242 } 243 244 /* make jump label nops */ 245 jump_label_apply_nops(me); 246 247 return 0; 248 } 249 250 void module_arch_cleanup(struct module *mod) 251 { 252 alternatives_smp_module_del(mod); 253 } 254