1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* Kernel module help for x86. 3 Copyright (C) 2001 Rusty Russell. 4 5 */ 6 7 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 8 9 #include <linux/moduleloader.h> 10 #include <linux/elf.h> 11 #include <linux/vmalloc.h> 12 #include <linux/fs.h> 13 #include <linux/string.h> 14 #include <linux/kernel.h> 15 #include <linux/kasan.h> 16 #include <linux/bug.h> 17 #include <linux/mm.h> 18 #include <linux/gfp.h> 19 #include <linux/jump_label.h> 20 #include <linux/random.h> 21 #include <linux/memory.h> 22 23 #include <asm/text-patching.h> 24 #include <asm/page.h> 25 #include <asm/setup.h> 26 #include <asm/unwind.h> 27 28 #if 0 29 #define DEBUGP(fmt, ...) \ 30 printk(KERN_DEBUG fmt, ##__VA_ARGS__) 31 #else 32 #define DEBUGP(fmt, ...) \ 33 do { \ 34 if (0) \ 35 printk(KERN_DEBUG fmt, ##__VA_ARGS__); \ 36 } while (0) 37 #endif 38 39 #ifdef CONFIG_RANDOMIZE_BASE 40 static unsigned long module_load_offset; 41 42 /* Mutex protects the module_load_offset. */ 43 static DEFINE_MUTEX(module_kaslr_mutex); 44 45 static unsigned long int get_module_load_offset(void) 46 { 47 if (kaslr_enabled()) { 48 mutex_lock(&module_kaslr_mutex); 49 /* 50 * Calculate the module_load_offset the first time this 51 * code is called. Once calculated it stays the same until 52 * reboot. 53 */ 54 if (module_load_offset == 0) 55 module_load_offset = 56 get_random_u32_inclusive(1, 1024) * PAGE_SIZE; 57 mutex_unlock(&module_kaslr_mutex); 58 } 59 return module_load_offset; 60 } 61 #else 62 static unsigned long int get_module_load_offset(void) 63 { 64 return 0; 65 } 66 #endif 67 68 void *module_alloc(unsigned long size) 69 { 70 gfp_t gfp_mask = GFP_KERNEL; 71 void *p; 72 73 if (PAGE_ALIGN(size) > MODULES_LEN) 74 return NULL; 75 76 p = __vmalloc_node_range(size, MODULE_ALIGN, 77 MODULES_VADDR + get_module_load_offset(), 78 MODULES_END, gfp_mask, PAGE_KERNEL, 79 VM_FLUSH_RESET_PERMS | VM_DEFER_KMEMLEAK, 80 NUMA_NO_NODE, __builtin_return_address(0)); 81 82 if (p && (kasan_alloc_module_shadow(p, size, gfp_mask) < 0)) { 83 vfree(p); 84 return NULL; 85 } 86 87 return p; 88 } 89 90 #ifdef CONFIG_X86_32 91 int apply_relocate(Elf32_Shdr *sechdrs, 92 const char *strtab, 93 unsigned int symindex, 94 unsigned int relsec, 95 struct module *me) 96 { 97 unsigned int i; 98 Elf32_Rel *rel = (void *)sechdrs[relsec].sh_addr; 99 Elf32_Sym *sym; 100 uint32_t *location; 101 102 DEBUGP("Applying relocate section %u to %u\n", 103 relsec, sechdrs[relsec].sh_info); 104 for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) { 105 /* This is where to make the change */ 106 location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr 107 + rel[i].r_offset; 108 /* This is the symbol it is referring to. Note that all 109 undefined symbols have been resolved. */ 110 sym = (Elf32_Sym *)sechdrs[symindex].sh_addr 111 + ELF32_R_SYM(rel[i].r_info); 112 113 switch (ELF32_R_TYPE(rel[i].r_info)) { 114 case R_386_32: 115 /* We add the value into the location given */ 116 *location += sym->st_value; 117 break; 118 case R_386_PC32: 119 case R_386_PLT32: 120 /* Add the value, subtract its position */ 121 *location += sym->st_value - (uint32_t)location; 122 break; 123 default: 124 pr_err("%s: Unknown relocation: %u\n", 125 me->name, ELF32_R_TYPE(rel[i].r_info)); 126 return -ENOEXEC; 127 } 128 } 129 return 0; 130 } 131 #else /*X86_64*/ 132 static int __write_relocate_add(Elf64_Shdr *sechdrs, 133 const char *strtab, 134 unsigned int symindex, 135 unsigned int relsec, 136 struct module *me, 137 void *(*write)(void *dest, const void *src, size_t len), 138 bool apply) 139 { 140 unsigned int i; 141 Elf64_Rela *rel = (void *)sechdrs[relsec].sh_addr; 142 Elf64_Sym *sym; 143 void *loc; 144 u64 val; 145 u64 zero = 0ULL; 146 147 DEBUGP("%s relocate section %u to %u\n", 148 apply ? "Applying" : "Clearing", 149 relsec, sechdrs[relsec].sh_info); 150 for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) { 151 size_t size; 152 153 /* 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 continue; /* nothing to write */ 171 case R_X86_64_64: 172 size = 8; 173 break; 174 case R_X86_64_32: 175 if (val != *(u32 *)&val) 176 goto overflow; 177 size = 4; 178 break; 179 case R_X86_64_32S: 180 if ((s64)val != *(s32 *)&val) 181 goto overflow; 182 size = 4; 183 break; 184 case R_X86_64_PC32: 185 case R_X86_64_PLT32: 186 val -= (u64)loc; 187 size = 4; 188 break; 189 case R_X86_64_PC64: 190 val -= (u64)loc; 191 size = 8; 192 break; 193 default: 194 pr_err("%s: Unknown rela relocation: %llu\n", 195 me->name, ELF64_R_TYPE(rel[i].r_info)); 196 return -ENOEXEC; 197 } 198 199 if (apply) { 200 if (memcmp(loc, &zero, size)) { 201 pr_err("x86/modules: Invalid relocation target, existing value is nonzero for type %d, loc %p, val %Lx\n", 202 (int)ELF64_R_TYPE(rel[i].r_info), loc, val); 203 return -ENOEXEC; 204 } 205 write(loc, &val, size); 206 } else { 207 if (memcmp(loc, &val, size)) { 208 pr_warn("x86/modules: Invalid relocation target, existing value does not match expected value for type %d, loc %p, val %Lx\n", 209 (int)ELF64_R_TYPE(rel[i].r_info), loc, val); 210 return -ENOEXEC; 211 } 212 write(loc, &zero, size); 213 } 214 } 215 return 0; 216 217 overflow: 218 pr_err("overflow in relocation type %d val %Lx\n", 219 (int)ELF64_R_TYPE(rel[i].r_info), val); 220 pr_err("`%s' likely not compiled with -mcmodel=kernel\n", 221 me->name); 222 return -ENOEXEC; 223 } 224 225 static int write_relocate_add(Elf64_Shdr *sechdrs, 226 const char *strtab, 227 unsigned int symindex, 228 unsigned int relsec, 229 struct module *me, 230 bool apply) 231 { 232 int ret; 233 bool early = me->state == MODULE_STATE_UNFORMED; 234 void *(*write)(void *, const void *, size_t) = memcpy; 235 236 if (!early) { 237 write = text_poke; 238 mutex_lock(&text_mutex); 239 } 240 241 ret = __write_relocate_add(sechdrs, strtab, symindex, relsec, me, 242 write, apply); 243 244 if (!early) { 245 text_poke_sync(); 246 mutex_unlock(&text_mutex); 247 } 248 249 return ret; 250 } 251 252 int apply_relocate_add(Elf64_Shdr *sechdrs, 253 const char *strtab, 254 unsigned int symindex, 255 unsigned int relsec, 256 struct module *me) 257 { 258 return write_relocate_add(sechdrs, strtab, symindex, relsec, me, true); 259 } 260 261 #ifdef CONFIG_LIVEPATCH 262 void clear_relocate_add(Elf64_Shdr *sechdrs, 263 const char *strtab, 264 unsigned int symindex, 265 unsigned int relsec, 266 struct module *me) 267 { 268 write_relocate_add(sechdrs, strtab, symindex, relsec, me, false); 269 } 270 #endif 271 272 #endif 273 274 int module_finalize(const Elf_Ehdr *hdr, 275 const Elf_Shdr *sechdrs, 276 struct module *me) 277 { 278 const Elf_Shdr *s, *alt = NULL, *locks = NULL, 279 *para = NULL, *orc = NULL, *orc_ip = NULL, 280 *retpolines = NULL, *returns = NULL, *ibt_endbr = NULL, 281 *calls = NULL, *cfi = NULL; 282 char *secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset; 283 284 for (s = sechdrs; s < sechdrs + hdr->e_shnum; s++) { 285 if (!strcmp(".altinstructions", secstrings + s->sh_name)) 286 alt = s; 287 if (!strcmp(".smp_locks", secstrings + s->sh_name)) 288 locks = s; 289 if (!strcmp(".parainstructions", secstrings + s->sh_name)) 290 para = s; 291 if (!strcmp(".orc_unwind", secstrings + s->sh_name)) 292 orc = s; 293 if (!strcmp(".orc_unwind_ip", secstrings + s->sh_name)) 294 orc_ip = s; 295 if (!strcmp(".retpoline_sites", secstrings + s->sh_name)) 296 retpolines = s; 297 if (!strcmp(".return_sites", secstrings + s->sh_name)) 298 returns = s; 299 if (!strcmp(".call_sites", secstrings + s->sh_name)) 300 calls = s; 301 if (!strcmp(".cfi_sites", secstrings + s->sh_name)) 302 cfi = s; 303 if (!strcmp(".ibt_endbr_seal", secstrings + s->sh_name)) 304 ibt_endbr = s; 305 } 306 307 /* 308 * See alternative_instructions() for the ordering rules between the 309 * various patching types. 310 */ 311 if (para) { 312 void *pseg = (void *)para->sh_addr; 313 apply_paravirt(pseg, pseg + para->sh_size); 314 } 315 if (retpolines || cfi) { 316 void *rseg = NULL, *cseg = NULL; 317 unsigned int rsize = 0, csize = 0; 318 319 if (retpolines) { 320 rseg = (void *)retpolines->sh_addr; 321 rsize = retpolines->sh_size; 322 } 323 324 if (cfi) { 325 cseg = (void *)cfi->sh_addr; 326 csize = cfi->sh_size; 327 } 328 329 apply_fineibt(rseg, rseg + rsize, cseg, cseg + csize); 330 } 331 if (retpolines) { 332 void *rseg = (void *)retpolines->sh_addr; 333 apply_retpolines(rseg, rseg + retpolines->sh_size); 334 } 335 if (returns) { 336 void *rseg = (void *)returns->sh_addr; 337 apply_returns(rseg, rseg + returns->sh_size); 338 } 339 if (alt) { 340 /* patch .altinstructions */ 341 void *aseg = (void *)alt->sh_addr; 342 apply_alternatives(aseg, aseg + alt->sh_size); 343 } 344 if (calls || para) { 345 struct callthunk_sites cs = {}; 346 347 if (calls) { 348 cs.call_start = (void *)calls->sh_addr; 349 cs.call_end = (void *)calls->sh_addr + calls->sh_size; 350 } 351 352 if (para) { 353 cs.pv_start = (void *)para->sh_addr; 354 cs.pv_end = (void *)para->sh_addr + para->sh_size; 355 } 356 357 callthunks_patch_module_calls(&cs, me); 358 } 359 if (ibt_endbr) { 360 void *iseg = (void *)ibt_endbr->sh_addr; 361 apply_ibt_endbr(iseg, iseg + ibt_endbr->sh_size); 362 } 363 if (locks) { 364 void *lseg = (void *)locks->sh_addr; 365 void *text = me->mem[MOD_TEXT].base; 366 void *text_end = text + me->mem[MOD_TEXT].size; 367 alternatives_smp_module_add(me, me->name, 368 lseg, lseg + locks->sh_size, 369 text, text_end); 370 } 371 372 if (orc && orc_ip) 373 unwind_module_init(me, (void *)orc_ip->sh_addr, orc_ip->sh_size, 374 (void *)orc->sh_addr, orc->sh_size); 375 376 return 0; 377 } 378 379 void module_arch_cleanup(struct module *mod) 380 { 381 alternatives_smp_module_del(mod); 382 } 383