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/kasan.h> 28 #include <linux/bug.h> 29 #include <linux/mm.h> 30 #include <linux/gfp.h> 31 #include <linux/jump_label.h> 32 #include <linux/random.h> 33 34 #include <asm/page.h> 35 #include <asm/pgtable.h> 36 37 #if 0 38 #define DEBUGP(fmt, ...) \ 39 printk(KERN_DEBUG fmt, ##__VA_ARGS__) 40 #else 41 #define DEBUGP(fmt, ...) \ 42 do { \ 43 if (0) \ 44 printk(KERN_DEBUG fmt, ##__VA_ARGS__); \ 45 } while (0) 46 #endif 47 48 #ifdef CONFIG_RANDOMIZE_BASE 49 static unsigned long module_load_offset; 50 static int randomize_modules = 1; 51 52 /* Mutex protects the module_load_offset. */ 53 static DEFINE_MUTEX(module_kaslr_mutex); 54 55 static int __init parse_nokaslr(char *p) 56 { 57 randomize_modules = 0; 58 return 0; 59 } 60 early_param("nokaslr", parse_nokaslr); 61 62 static unsigned long int get_module_load_offset(void) 63 { 64 if (randomize_modules) { 65 mutex_lock(&module_kaslr_mutex); 66 /* 67 * Calculate the module_load_offset the first time this 68 * code is called. Once calculated it stays the same until 69 * reboot. 70 */ 71 if (module_load_offset == 0) 72 module_load_offset = 73 (get_random_int() % 1024 + 1) * PAGE_SIZE; 74 mutex_unlock(&module_kaslr_mutex); 75 } 76 return module_load_offset; 77 } 78 #else 79 static unsigned long int get_module_load_offset(void) 80 { 81 return 0; 82 } 83 #endif 84 85 void *module_alloc(unsigned long size) 86 { 87 void *p; 88 89 if (PAGE_ALIGN(size) > MODULES_LEN) 90 return NULL; 91 92 p = __vmalloc_node_range(size, MODULE_ALIGN, 93 MODULES_VADDR + get_module_load_offset(), 94 MODULES_END, GFP_KERNEL | __GFP_HIGHMEM, 95 PAGE_KERNEL_EXEC, 0, NUMA_NO_NODE, 96 __builtin_return_address(0)); 97 if (p && (kasan_module_alloc(p, size) < 0)) { 98 vfree(p); 99 return NULL; 100 } 101 102 return p; 103 } 104 105 #ifdef CONFIG_X86_32 106 int apply_relocate(Elf32_Shdr *sechdrs, 107 const char *strtab, 108 unsigned int symindex, 109 unsigned int relsec, 110 struct module *me) 111 { 112 unsigned int i; 113 Elf32_Rel *rel = (void *)sechdrs[relsec].sh_addr; 114 Elf32_Sym *sym; 115 uint32_t *location; 116 117 DEBUGP("Applying relocate section %u to %u\n", 118 relsec, sechdrs[relsec].sh_info); 119 for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) { 120 /* This is where to make the change */ 121 location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr 122 + rel[i].r_offset; 123 /* This is the symbol it is referring to. Note that all 124 undefined symbols have been resolved. */ 125 sym = (Elf32_Sym *)sechdrs[symindex].sh_addr 126 + ELF32_R_SYM(rel[i].r_info); 127 128 switch (ELF32_R_TYPE(rel[i].r_info)) { 129 case R_386_32: 130 /* We add the value into the location given */ 131 *location += sym->st_value; 132 break; 133 case R_386_PC32: 134 /* Add the value, subtract its position */ 135 *location += sym->st_value - (uint32_t)location; 136 break; 137 default: 138 pr_err("%s: Unknown relocation: %u\n", 139 me->name, ELF32_R_TYPE(rel[i].r_info)); 140 return -ENOEXEC; 141 } 142 } 143 return 0; 144 } 145 #else /*X86_64*/ 146 int apply_relocate_add(Elf64_Shdr *sechdrs, 147 const char *strtab, 148 unsigned int symindex, 149 unsigned int relsec, 150 struct module *me) 151 { 152 unsigned int i; 153 Elf64_Rela *rel = (void *)sechdrs[relsec].sh_addr; 154 Elf64_Sym *sym; 155 void *loc; 156 u64 val; 157 158 DEBUGP("Applying relocate section %u to %u\n", 159 relsec, sechdrs[relsec].sh_info); 160 for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) { 161 /* This is where to make the change */ 162 loc = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr 163 + rel[i].r_offset; 164 165 /* This is the symbol it is referring to. Note that all 166 undefined symbols have been resolved. */ 167 sym = (Elf64_Sym *)sechdrs[symindex].sh_addr 168 + ELF64_R_SYM(rel[i].r_info); 169 170 DEBUGP("type %d st_value %Lx r_addend %Lx loc %Lx\n", 171 (int)ELF64_R_TYPE(rel[i].r_info), 172 sym->st_value, rel[i].r_addend, (u64)loc); 173 174 val = sym->st_value + rel[i].r_addend; 175 176 switch (ELF64_R_TYPE(rel[i].r_info)) { 177 case R_X86_64_NONE: 178 break; 179 case R_X86_64_64: 180 *(u64 *)loc = val; 181 break; 182 case R_X86_64_32: 183 *(u32 *)loc = val; 184 if (val != *(u32 *)loc) 185 goto overflow; 186 break; 187 case R_X86_64_32S: 188 *(s32 *)loc = val; 189 if ((s64)val != *(s32 *)loc) 190 goto overflow; 191 break; 192 case R_X86_64_PC32: 193 val -= (u64)loc; 194 *(u32 *)loc = val; 195 #if 0 196 if ((s64)val != *(s32 *)loc) 197 goto overflow; 198 #endif 199 break; 200 default: 201 pr_err("%s: Unknown rela relocation: %llu\n", 202 me->name, ELF64_R_TYPE(rel[i].r_info)); 203 return -ENOEXEC; 204 } 205 } 206 return 0; 207 208 overflow: 209 pr_err("overflow in relocation type %d val %Lx\n", 210 (int)ELF64_R_TYPE(rel[i].r_info), val); 211 pr_err("`%s' likely not compiled with -mcmodel=kernel\n", 212 me->name); 213 return -ENOEXEC; 214 } 215 #endif 216 217 int module_finalize(const Elf_Ehdr *hdr, 218 const Elf_Shdr *sechdrs, 219 struct module *me) 220 { 221 const Elf_Shdr *s, *text = NULL, *alt = NULL, *locks = NULL, 222 *para = NULL; 223 char *secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset; 224 225 for (s = sechdrs; s < sechdrs + hdr->e_shnum; s++) { 226 if (!strcmp(".text", secstrings + s->sh_name)) 227 text = s; 228 if (!strcmp(".altinstructions", secstrings + s->sh_name)) 229 alt = s; 230 if (!strcmp(".smp_locks", secstrings + s->sh_name)) 231 locks = s; 232 if (!strcmp(".parainstructions", secstrings + s->sh_name)) 233 para = s; 234 } 235 236 if (alt) { 237 /* patch .altinstructions */ 238 void *aseg = (void *)alt->sh_addr; 239 apply_alternatives(aseg, aseg + alt->sh_size); 240 } 241 if (locks && text) { 242 void *lseg = (void *)locks->sh_addr; 243 void *tseg = (void *)text->sh_addr; 244 alternatives_smp_module_add(me, me->name, 245 lseg, lseg + locks->sh_size, 246 tseg, tseg + text->sh_size); 247 } 248 249 if (para) { 250 void *pseg = (void *)para->sh_addr; 251 apply_paravirt(pseg, pseg + para->sh_size); 252 } 253 254 /* make jump label nops */ 255 jump_label_apply_nops(me); 256 257 return 0; 258 } 259 260 void module_arch_cleanup(struct module *mod) 261 { 262 alternatives_smp_module_del(mod); 263 } 264