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 #include <linux/stackprotector.h> 23 24 #include <asm/text-patching.h> 25 #include <asm/page.h> 26 #include <asm/setup.h> 27 #include <asm/unwind.h> 28 29 #if 0 30 #define DEBUGP(fmt, ...) \ 31 printk(KERN_DEBUG fmt, ##__VA_ARGS__) 32 #else 33 #define DEBUGP(fmt, ...) \ 34 do { \ 35 if (0) \ 36 printk(KERN_DEBUG fmt, ##__VA_ARGS__); \ 37 } while (0) 38 #endif 39 40 #ifdef CONFIG_X86_32 41 int apply_relocate(Elf32_Shdr *sechdrs, 42 const char *strtab, 43 unsigned int symindex, 44 unsigned int relsec, 45 struct module *me) 46 { 47 unsigned int i; 48 Elf32_Rel *rel = (void *)sechdrs[relsec].sh_addr; 49 Elf32_Sym *sym; 50 uint32_t *location; 51 52 DEBUGP("Applying relocate section %u to %u\n", 53 relsec, sechdrs[relsec].sh_info); 54 for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) { 55 /* This is where to make the change */ 56 location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr 57 + rel[i].r_offset; 58 /* This is the symbol it is referring to. Note that all 59 undefined symbols have been resolved. */ 60 sym = (Elf32_Sym *)sechdrs[symindex].sh_addr 61 + ELF32_R_SYM(rel[i].r_info); 62 63 switch (ELF32_R_TYPE(rel[i].r_info)) { 64 case R_386_32: 65 /* We add the value into the location given */ 66 *location += sym->st_value; 67 break; 68 case R_386_PC32: 69 case R_386_PLT32: 70 /* Add the value, subtract its position */ 71 *location += sym->st_value - (uint32_t)location; 72 break; 73 default: 74 pr_err("%s: Unknown relocation: %u\n", 75 me->name, ELF32_R_TYPE(rel[i].r_info)); 76 return -ENOEXEC; 77 } 78 } 79 return 0; 80 } 81 #else /*X86_64*/ 82 static int __write_relocate_add(Elf64_Shdr *sechdrs, 83 const char *strtab, 84 unsigned int symindex, 85 unsigned int relsec, 86 struct module *me, 87 void *(*write)(void *dest, const void *src, size_t len), 88 bool apply) 89 { 90 unsigned int i; 91 Elf64_Rela *rel = (void *)sechdrs[relsec].sh_addr; 92 Elf64_Sym *sym; 93 void *loc; 94 u64 val; 95 u64 zero = 0ULL; 96 97 DEBUGP("%s relocate section %u to %u\n", 98 apply ? "Applying" : "Clearing", 99 relsec, sechdrs[relsec].sh_info); 100 for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) { 101 size_t size; 102 103 /* This is where to make the change */ 104 loc = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr 105 + rel[i].r_offset; 106 107 /* This is the symbol it is referring to. Note that all 108 undefined symbols have been resolved. */ 109 sym = (Elf64_Sym *)sechdrs[symindex].sh_addr 110 + ELF64_R_SYM(rel[i].r_info); 111 112 DEBUGP("type %d st_value %Lx r_addend %Lx loc %Lx\n", 113 (int)ELF64_R_TYPE(rel[i].r_info), 114 sym->st_value, rel[i].r_addend, (u64)loc); 115 116 val = sym->st_value + rel[i].r_addend; 117 118 switch (ELF64_R_TYPE(rel[i].r_info)) { 119 case R_X86_64_NONE: 120 continue; /* nothing to write */ 121 case R_X86_64_64: 122 size = 8; 123 break; 124 case R_X86_64_32: 125 if (val != *(u32 *)&val) 126 goto overflow; 127 size = 4; 128 break; 129 case R_X86_64_32S: 130 if ((s64)val != *(s32 *)&val) 131 goto overflow; 132 size = 4; 133 break; 134 #if defined(CONFIG_STACKPROTECTOR) && \ 135 defined(CONFIG_CC_IS_CLANG) && CONFIG_CLANG_VERSION < 170000 136 case R_X86_64_REX_GOTPCRELX: { 137 static unsigned long __percpu *const addr = &__stack_chk_guard; 138 139 if (sym->st_value != (u64)addr) { 140 pr_err("%s: Unsupported GOTPCREL relocation\n", me->name); 141 return -ENOEXEC; 142 } 143 144 val = (u64)&addr + rel[i].r_addend; 145 fallthrough; 146 } 147 #endif 148 case R_X86_64_PC32: 149 case R_X86_64_PLT32: 150 val -= (u64)loc; 151 size = 4; 152 break; 153 case R_X86_64_PC64: 154 val -= (u64)loc; 155 size = 8; 156 break; 157 default: 158 pr_err("%s: Unknown rela relocation: %llu\n", 159 me->name, ELF64_R_TYPE(rel[i].r_info)); 160 return -ENOEXEC; 161 } 162 163 if (apply) { 164 if (memcmp(loc, &zero, size)) { 165 pr_err("x86/modules: Invalid relocation target, existing value is nonzero for type %d, loc %p, val %Lx\n", 166 (int)ELF64_R_TYPE(rel[i].r_info), loc, val); 167 return -ENOEXEC; 168 } 169 write(loc, &val, size); 170 } else { 171 if (memcmp(loc, &val, size)) { 172 pr_warn("x86/modules: Invalid relocation target, existing value does not match expected value for type %d, loc %p, val %Lx\n", 173 (int)ELF64_R_TYPE(rel[i].r_info), loc, val); 174 return -ENOEXEC; 175 } 176 write(loc, &zero, size); 177 } 178 } 179 return 0; 180 181 overflow: 182 pr_err("overflow in relocation type %d val %Lx\n", 183 (int)ELF64_R_TYPE(rel[i].r_info), val); 184 pr_err("`%s' likely not compiled with -mcmodel=kernel\n", 185 me->name); 186 return -ENOEXEC; 187 } 188 189 static int write_relocate_add(Elf64_Shdr *sechdrs, 190 const char *strtab, 191 unsigned int symindex, 192 unsigned int relsec, 193 struct module *me, 194 bool apply) 195 { 196 int ret; 197 bool early = me->state == MODULE_STATE_UNFORMED; 198 void *(*write)(void *, const void *, size_t) = memcpy; 199 200 if (!early) { 201 write = text_poke; 202 mutex_lock(&text_mutex); 203 } 204 205 ret = __write_relocate_add(sechdrs, strtab, symindex, relsec, me, 206 write, apply); 207 208 if (!early) { 209 smp_text_poke_sync_each_cpu(); 210 mutex_unlock(&text_mutex); 211 } 212 213 return ret; 214 } 215 216 int apply_relocate_add(Elf64_Shdr *sechdrs, 217 const char *strtab, 218 unsigned int symindex, 219 unsigned int relsec, 220 struct module *me) 221 { 222 return write_relocate_add(sechdrs, strtab, symindex, relsec, me, true); 223 } 224 225 #ifdef CONFIG_LIVEPATCH 226 void clear_relocate_add(Elf64_Shdr *sechdrs, 227 const char *strtab, 228 unsigned int symindex, 229 unsigned int relsec, 230 struct module *me) 231 { 232 write_relocate_add(sechdrs, strtab, symindex, relsec, me, false); 233 } 234 #endif 235 236 #endif 237 238 int module_finalize(const Elf_Ehdr *hdr, 239 const Elf_Shdr *sechdrs, 240 struct module *me) 241 { 242 const Elf_Shdr *s, *alt = NULL, *locks = NULL, 243 *orc = NULL, *orc_ip = NULL, 244 *retpolines = NULL, *returns = NULL, *ibt_endbr = NULL, 245 *calls = NULL, *cfi = NULL; 246 char *secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset; 247 248 for (s = sechdrs; s < sechdrs + hdr->e_shnum; s++) { 249 if (!strcmp(".altinstructions", secstrings + s->sh_name)) 250 alt = s; 251 if (!strcmp(".smp_locks", secstrings + s->sh_name)) 252 locks = s; 253 if (!strcmp(".orc_unwind", secstrings + s->sh_name)) 254 orc = s; 255 if (!strcmp(".orc_unwind_ip", secstrings + s->sh_name)) 256 orc_ip = s; 257 if (!strcmp(".retpoline_sites", secstrings + s->sh_name)) 258 retpolines = s; 259 if (!strcmp(".return_sites", secstrings + s->sh_name)) 260 returns = s; 261 if (!strcmp(".call_sites", secstrings + s->sh_name)) 262 calls = s; 263 if (!strcmp(".cfi_sites", secstrings + s->sh_name)) 264 cfi = s; 265 if (!strcmp(".ibt_endbr_seal", secstrings + s->sh_name)) 266 ibt_endbr = s; 267 } 268 269 its_init_mod(me); 270 271 if (retpolines || cfi) { 272 void *rseg = NULL, *cseg = NULL; 273 unsigned int rsize = 0, csize = 0; 274 275 if (retpolines) { 276 rseg = (void *)retpolines->sh_addr; 277 rsize = retpolines->sh_size; 278 } 279 280 if (cfi) { 281 cseg = (void *)cfi->sh_addr; 282 csize = cfi->sh_size; 283 } 284 285 apply_fineibt(rseg, rseg + rsize, cseg, cseg + csize); 286 } 287 if (retpolines) { 288 void *rseg = (void *)retpolines->sh_addr; 289 apply_retpolines(rseg, rseg + retpolines->sh_size); 290 } 291 292 its_fini_mod(me); 293 294 if (returns) { 295 void *rseg = (void *)returns->sh_addr; 296 apply_returns(rseg, rseg + returns->sh_size); 297 } 298 if (calls) { 299 struct callthunk_sites cs = {}; 300 301 cs.call_start = (void *)calls->sh_addr; 302 cs.call_end = (void *)calls->sh_addr + calls->sh_size; 303 304 callthunks_patch_module_calls(&cs, me); 305 } 306 if (alt) { 307 /* patch .altinstructions */ 308 void *aseg = (void *)alt->sh_addr; 309 apply_alternatives(aseg, aseg + alt->sh_size); 310 } 311 if (ibt_endbr) { 312 void *iseg = (void *)ibt_endbr->sh_addr; 313 apply_seal_endbr(iseg, iseg + ibt_endbr->sh_size); 314 } 315 if (locks) { 316 void *lseg = (void *)locks->sh_addr; 317 void *text = me->mem[MOD_TEXT].base; 318 void *text_end = text + me->mem[MOD_TEXT].size; 319 alternatives_smp_module_add(me, me->name, 320 lseg, lseg + locks->sh_size, 321 text, text_end); 322 } 323 324 if (orc && orc_ip) 325 unwind_module_init(me, (void *)orc_ip->sh_addr, orc_ip->sh_size, 326 (void *)orc->sh_addr, orc->sh_size); 327 328 return 0; 329 } 330 331 void module_arch_cleanup(struct module *mod) 332 { 333 alternatives_smp_module_del(mod); 334 its_free_mod(mod); 335 } 336