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