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_X86_32 40 int apply_relocate(Elf32_Shdr *sechdrs, 41 const char *strtab, 42 unsigned int symindex, 43 unsigned int relsec, 44 struct module *me) 45 { 46 unsigned int i; 47 Elf32_Rel *rel = (void *)sechdrs[relsec].sh_addr; 48 Elf32_Sym *sym; 49 uint32_t *location; 50 51 DEBUGP("Applying relocate section %u to %u\n", 52 relsec, sechdrs[relsec].sh_info); 53 for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) { 54 /* This is where to make the change */ 55 location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr 56 + rel[i].r_offset; 57 /* This is the symbol it is referring to. Note that all 58 undefined symbols have been resolved. */ 59 sym = (Elf32_Sym *)sechdrs[symindex].sh_addr 60 + ELF32_R_SYM(rel[i].r_info); 61 62 switch (ELF32_R_TYPE(rel[i].r_info)) { 63 case R_386_32: 64 /* We add the value into the location given */ 65 *location += sym->st_value; 66 break; 67 case R_386_PC32: 68 case R_386_PLT32: 69 /* Add the value, subtract its position */ 70 *location += sym->st_value - (uint32_t)location; 71 break; 72 default: 73 pr_err("%s: Unknown relocation: %u\n", 74 me->name, ELF32_R_TYPE(rel[i].r_info)); 75 return -ENOEXEC; 76 } 77 } 78 return 0; 79 } 80 #else /*X86_64*/ 81 static int __write_relocate_add(Elf64_Shdr *sechdrs, 82 const char *strtab, 83 unsigned int symindex, 84 unsigned int relsec, 85 struct module *me, 86 void *(*write)(void *dest, const void *src, size_t len), 87 bool apply) 88 { 89 unsigned int i; 90 Elf64_Rela *rel = (void *)sechdrs[relsec].sh_addr; 91 Elf64_Sym *sym; 92 void *loc; 93 u64 val; 94 u64 zero = 0ULL; 95 96 DEBUGP("%s relocate section %u to %u\n", 97 apply ? "Applying" : "Clearing", 98 relsec, sechdrs[relsec].sh_info); 99 for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) { 100 size_t size; 101 102 /* This is where to make the change */ 103 loc = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr 104 + rel[i].r_offset; 105 106 /* This is the symbol it is referring to. Note that all 107 undefined symbols have been resolved. */ 108 sym = (Elf64_Sym *)sechdrs[symindex].sh_addr 109 + ELF64_R_SYM(rel[i].r_info); 110 111 DEBUGP("type %d st_value %Lx r_addend %Lx loc %Lx\n", 112 (int)ELF64_R_TYPE(rel[i].r_info), 113 sym->st_value, rel[i].r_addend, (u64)loc); 114 115 val = sym->st_value + rel[i].r_addend; 116 117 switch (ELF64_R_TYPE(rel[i].r_info)) { 118 case R_X86_64_NONE: 119 continue; /* nothing to write */ 120 case R_X86_64_64: 121 size = 8; 122 break; 123 case R_X86_64_32: 124 if (val != *(u32 *)&val) 125 goto overflow; 126 size = 4; 127 break; 128 case R_X86_64_32S: 129 if ((s64)val != *(s32 *)&val) 130 goto overflow; 131 size = 4; 132 break; 133 case R_X86_64_PC32: 134 case R_X86_64_PLT32: 135 val -= (u64)loc; 136 size = 4; 137 break; 138 case R_X86_64_PC64: 139 val -= (u64)loc; 140 size = 8; 141 break; 142 default: 143 pr_err("%s: Unknown rela relocation: %llu\n", 144 me->name, ELF64_R_TYPE(rel[i].r_info)); 145 return -ENOEXEC; 146 } 147 148 if (apply) { 149 if (memcmp(loc, &zero, size)) { 150 pr_err("x86/modules: Invalid relocation target, existing value is nonzero for type %d, loc %p, val %Lx\n", 151 (int)ELF64_R_TYPE(rel[i].r_info), loc, val); 152 return -ENOEXEC; 153 } 154 write(loc, &val, size); 155 } else { 156 if (memcmp(loc, &val, size)) { 157 pr_warn("x86/modules: Invalid relocation target, existing value does not match expected value for type %d, loc %p, val %Lx\n", 158 (int)ELF64_R_TYPE(rel[i].r_info), loc, val); 159 return -ENOEXEC; 160 } 161 write(loc, &zero, size); 162 } 163 } 164 return 0; 165 166 overflow: 167 pr_err("overflow in relocation type %d val %Lx\n", 168 (int)ELF64_R_TYPE(rel[i].r_info), val); 169 pr_err("`%s' likely not compiled with -mcmodel=kernel\n", 170 me->name); 171 return -ENOEXEC; 172 } 173 174 static int write_relocate_add(Elf64_Shdr *sechdrs, 175 const char *strtab, 176 unsigned int symindex, 177 unsigned int relsec, 178 struct module *me, 179 bool apply) 180 { 181 int ret; 182 bool early = me->state == MODULE_STATE_UNFORMED; 183 void *(*write)(void *, const void *, size_t) = memcpy; 184 185 if (!early) { 186 write = text_poke; 187 mutex_lock(&text_mutex); 188 } 189 190 ret = __write_relocate_add(sechdrs, strtab, symindex, relsec, me, 191 write, apply); 192 193 if (!early) { 194 text_poke_sync(); 195 mutex_unlock(&text_mutex); 196 } 197 198 return ret; 199 } 200 201 int apply_relocate_add(Elf64_Shdr *sechdrs, 202 const char *strtab, 203 unsigned int symindex, 204 unsigned int relsec, 205 struct module *me) 206 { 207 return write_relocate_add(sechdrs, strtab, symindex, relsec, me, true); 208 } 209 210 #ifdef CONFIG_LIVEPATCH 211 void clear_relocate_add(Elf64_Shdr *sechdrs, 212 const char *strtab, 213 unsigned int symindex, 214 unsigned int relsec, 215 struct module *me) 216 { 217 write_relocate_add(sechdrs, strtab, symindex, relsec, me, false); 218 } 219 #endif 220 221 #endif 222 223 int module_finalize(const Elf_Ehdr *hdr, 224 const Elf_Shdr *sechdrs, 225 struct module *me) 226 { 227 const Elf_Shdr *s, *alt = NULL, *locks = NULL, 228 *orc = NULL, *orc_ip = NULL, 229 *retpolines = NULL, *returns = NULL, *ibt_endbr = NULL, 230 *calls = NULL, *cfi = NULL; 231 char *secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset; 232 233 for (s = sechdrs; s < sechdrs + hdr->e_shnum; s++) { 234 if (!strcmp(".altinstructions", secstrings + s->sh_name)) 235 alt = s; 236 if (!strcmp(".smp_locks", secstrings + s->sh_name)) 237 locks = s; 238 if (!strcmp(".orc_unwind", secstrings + s->sh_name)) 239 orc = s; 240 if (!strcmp(".orc_unwind_ip", secstrings + s->sh_name)) 241 orc_ip = s; 242 if (!strcmp(".retpoline_sites", secstrings + s->sh_name)) 243 retpolines = s; 244 if (!strcmp(".return_sites", secstrings + s->sh_name)) 245 returns = s; 246 if (!strcmp(".call_sites", secstrings + s->sh_name)) 247 calls = s; 248 if (!strcmp(".cfi_sites", secstrings + s->sh_name)) 249 cfi = s; 250 if (!strcmp(".ibt_endbr_seal", secstrings + s->sh_name)) 251 ibt_endbr = s; 252 } 253 254 if (retpolines || cfi) { 255 void *rseg = NULL, *cseg = NULL; 256 unsigned int rsize = 0, csize = 0; 257 258 if (retpolines) { 259 rseg = (void *)retpolines->sh_addr; 260 rsize = retpolines->sh_size; 261 } 262 263 if (cfi) { 264 cseg = (void *)cfi->sh_addr; 265 csize = cfi->sh_size; 266 } 267 268 apply_fineibt(rseg, rseg + rsize, cseg, cseg + csize); 269 } 270 if (retpolines) { 271 void *rseg = (void *)retpolines->sh_addr; 272 apply_retpolines(rseg, rseg + retpolines->sh_size); 273 } 274 if (returns) { 275 void *rseg = (void *)returns->sh_addr; 276 apply_returns(rseg, rseg + returns->sh_size); 277 } 278 if (alt) { 279 /* patch .altinstructions */ 280 void *aseg = (void *)alt->sh_addr; 281 apply_alternatives(aseg, aseg + alt->sh_size); 282 } 283 if (calls || alt) { 284 struct callthunk_sites cs = {}; 285 286 if (calls) { 287 cs.call_start = (void *)calls->sh_addr; 288 cs.call_end = (void *)calls->sh_addr + calls->sh_size; 289 } 290 291 if (alt) { 292 cs.alt_start = (void *)alt->sh_addr; 293 cs.alt_end = (void *)alt->sh_addr + alt->sh_size; 294 } 295 296 callthunks_patch_module_calls(&cs, me); 297 } 298 if (ibt_endbr) { 299 void *iseg = (void *)ibt_endbr->sh_addr; 300 apply_seal_endbr(iseg, iseg + ibt_endbr->sh_size); 301 } 302 if (locks) { 303 void *lseg = (void *)locks->sh_addr; 304 void *text = me->mem[MOD_TEXT].base; 305 void *text_end = text + me->mem[MOD_TEXT].size; 306 alternatives_smp_module_add(me, me->name, 307 lseg, lseg + locks->sh_size, 308 text, text_end); 309 } 310 311 if (orc && orc_ip) 312 unwind_module_init(me, (void *)orc_ip->sh_addr, orc_ip->sh_size, 313 (void *)orc->sh_addr, orc->sh_size); 314 315 return 0; 316 } 317 318 void module_arch_cleanup(struct module *mod) 319 { 320 alternatives_smp_module_del(mod); 321 } 322