1 /* $OpenBSD: rtld_machine.c,v 1.23 2016/06/21 15:25:37 deraadt Exp $ */ 2 3 /* 4 * Copyright (c) 2004 Dale Rahn 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS 16 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 17 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 18 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY 19 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 20 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 21 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 22 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 23 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 24 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 25 * SUCH DAMAGE. 26 * 27 */ 28 29 #define _DYN_LOADER 30 31 #include <sys/types.h> 32 #include <sys/mman.h> 33 #include <sys/syscall.h> 34 #include <sys/unistd.h> 35 36 #include <nlist.h> 37 #include <link.h> 38 39 #include "syscall.h" 40 #include "archdep.h" 41 #include "resolve.h" 42 43 int64_t pcookie __attribute__((section(".openbsd.randomdata"))) __dso_hidden; 44 45 void _dl_bind_start(void); /* XXX */ 46 Elf_Addr _dl_bind(elf_object_t *object, int reloff); 47 #define _RF_S 0x80000000 /* Resolve symbol */ 48 #define _RF_A 0x40000000 /* Use addend */ 49 #define _RF_P 0x20000000 /* Location relative */ 50 #define _RF_G 0x10000000 /* GOT offset */ 51 #define _RF_B 0x08000000 /* Load address relative */ 52 #define _RF_U 0x04000000 /* Unaligned */ 53 #define _RF_E 0x02000000 /* ERROR */ 54 #define _RF_SZ(s) (((s) & 0xff) << 8) /* memory target size */ 55 #define _RF_RS(s) ((s) & 0xff) /* right shift */ 56 static int reloc_target_flags[] = { 57 0, /* 0 NONE */ 58 _RF_S|_RF_P|_RF_A| _RF_SZ(32) | _RF_RS(0), /* 1 PC24 */ 59 _RF_S|_RF_A| _RF_SZ(32) | _RF_RS(0), /* 2 ABS32 */ 60 _RF_S|_RF_P|_RF_A| _RF_SZ(32) | _RF_RS(0), /* 3 REL32 */ 61 _RF_S|_RF_P|_RF_A| _RF_E, /* 4 REL13 */ 62 _RF_S|_RF_A| _RF_E, /* 5 ABS16 */ 63 _RF_S|_RF_A| _RF_E, /* 6 ABS12 */ 64 _RF_S|_RF_A| _RF_E, /* 7 T_ABS5 */ 65 _RF_S|_RF_A| _RF_E, /* 8 ABS8 */ 66 _RF_S|_RF_B|_RF_A| _RF_E, /* 9 SBREL32 */ 67 _RF_S|_RF_P|_RF_A| _RF_E, /* 10 T_PC22 */ 68 _RF_S|_RF_P|_RF_A| _RF_E, /* 11 T_PC8 */ 69 _RF_E, /* 12 Reserved */ 70 _RF_S|_RF_A| _RF_E, /* 13 SWI24 */ 71 _RF_S|_RF_A| _RF_E, /* 14 T_SWI8 */ 72 _RF_E, /* 15 OBSL */ 73 _RF_E, /* 16 OBSL */ 74 _RF_E, /* 17 UNUSED */ 75 _RF_E, /* 18 UNUSED */ 76 _RF_E, /* 19 UNUSED */ 77 _RF_S| _RF_SZ(32) | _RF_RS(0), /* 20 COPY */ 78 _RF_S|_RF_A| _RF_SZ(32) | _RF_RS(0), /* 21 GLOB_DAT */ 79 _RF_S| _RF_SZ(32) | _RF_RS(0), /* 22 JUMP_SLOT */ 80 _RF_A| _RF_B| _RF_SZ(32) | _RF_RS(0), /* 23 RELATIVE */ 81 _RF_E, /* 24 GOTOFF */ 82 _RF_E, /* 25 GOTPC */ 83 _RF_E, /* 26 GOT32 */ 84 _RF_E, /* 27 PLT32 */ 85 _RF_E, /* 28 UNUSED */ 86 _RF_E, /* 29 UNUSED */ 87 _RF_E, /* 30 UNUSED */ 88 _RF_E, /* 31 UNUSED */ 89 _RF_E, /* 32 A_PCR 0 */ 90 _RF_E, /* 33 A_PCR 8 */ 91 _RF_E, /* 34 A_PCR 16 */ 92 _RF_E, /* 35 B_PCR 0 */ 93 _RF_E, /* 36 B_PCR 12 */ 94 _RF_E, /* 37 B_PCR 20 */ 95 _RF_E, /* 38 RELAB32 */ 96 _RF_E, /* 39 ROSGREL32 */ 97 _RF_E, /* 40 V4BX */ 98 _RF_E, /* 41 STKCHK */ 99 _RF_E /* 42 TSTKCHK */ 100 }; 101 102 #define RELOC_RESOLVE_SYMBOL(t) ((reloc_target_flags[t] & _RF_S) != 0) 103 #define RELOC_PC_RELATIVE(t) ((reloc_target_flags[t] & _RF_P) != 0) 104 #define RELOC_BASE_RELATIVE(t) ((reloc_target_flags[t] & _RF_B) != 0) 105 #define RELOC_UNALIGNED(t) ((reloc_target_flags[t] & _RF_U) != 0) 106 #define RELOC_USE_ADDEND(t) ((reloc_target_flags[t] & _RF_A) != 0) 107 #define RELOC_TARGET_SIZE(t) ((reloc_target_flags[t] >> 8) & 0xff) 108 #define RELOC_VALUE_RIGHTSHIFT(t) (reloc_target_flags[t] & 0xff) 109 static int reloc_target_bitmask[] = { 110 #define _BM(x) (x == 32? ~0 : ~(-(1UL << (x)))) 111 _BM(0), /* 0 NONE */ 112 _BM(24), /* 1 PC24 */ 113 _BM(32), /* 2 ABS32 */ 114 _BM(32), /* 3 REL32 */ 115 _BM(0), /* 4 REL13 */ 116 _BM(0), /* 5 ABS16 */ 117 _BM(0), /* 6 ABS12 */ 118 _BM(0), /* 7 T_ABS5 */ 119 _BM(0), /* 8 ABS8 */ 120 _BM(32), /* 9 SBREL32 */ 121 _BM(0), /* 10 T_PC22 */ 122 _BM(0), /* 11 T_PC8 */ 123 _BM(0), /* 12 Reserved */ 124 _BM(0), /* 13 SWI24 */ 125 _BM(0), /* 14 T_SWI8 */ 126 _BM(0), /* 15 OBSL */ 127 _BM(0), /* 16 OBSL */ 128 _BM(0), /* 17 UNUSED */ 129 _BM(0), /* 18 UNUSED */ 130 _BM(0), /* 19 UNUSED */ 131 _BM(32), /* 20 COPY */ 132 _BM(32), /* 21 GLOB_DAT */ 133 _BM(32), /* 22 JUMP_SLOT */ 134 _BM(32), /* 23 RELATIVE */ 135 _BM(0), /* 24 GOTOFF */ 136 _BM(0), /* 25 GOTPC */ 137 _BM(0), /* 26 GOT32 */ 138 _BM(0), /* 27 PLT32 */ 139 _BM(0), /* 28 UNUSED */ 140 _BM(0), /* 29 UNUSED */ 141 _BM(0), /* 30 UNUSED */ 142 _BM(0), /* 31 UNUSED */ 143 _BM(0), /* 32 A_PCR 0 */ 144 _BM(0), /* 33 A_PCR 8 */ 145 _BM(0), /* 34 A_PCR 16 */ 146 _BM(0), /* 35 B_PCR 0 */ 147 _BM(0), /* 36 B_PCR 12 */ 148 _BM(0), /* 37 B_PCR 20 */ 149 _BM(0), /* 38 RELAB32 */ 150 _BM(0), /* 39 ROSGREL32 */ 151 _BM(0), /* 40 V4BX */ 152 _BM(0), /* 41 STKCHK */ 153 _BM(0) /* 42 TSTKCHK */ 154 #undef _BM 155 }; 156 #define RELOC_VALUE_BITMASK(t) (reloc_target_bitmask[t]) 157 158 #define R_TYPE(x) R_ARM_ ## x 159 160 void _dl_reloc_plt(Elf_Word *where, Elf_Addr value, Elf_Rel *rel); 161 162 int 163 _dl_md_reloc(elf_object_t *object, int rel, int relsz) 164 { 165 long i; 166 long numrel; 167 long relrel; 168 int fails = 0; 169 Elf_Addr loff; 170 Elf_Addr prev_value = 0; 171 const Elf_Sym *prev_sym = NULL; 172 Elf_Rel *rels; 173 struct load_list *llist; 174 175 loff = object->obj_base; 176 numrel = object->Dyn.info[relsz] / sizeof(Elf_Rel); 177 relrel = rel == DT_REL ? object->relcount : 0; 178 rels = (Elf_Rel *)(object->Dyn.info[rel]); 179 180 if (rels == NULL) 181 return(0); 182 183 if (relrel > numrel) { 184 _dl_printf("relcount > numrel: %ld > %ld\n", relrel, numrel); 185 _dl_exit(20); 186 } 187 188 /* 189 * unprotect some segments if we need it. 190 */ 191 if ((object->dyn.textrel == 1) && (rel == DT_REL || rel == DT_RELA)) { 192 for (llist = object->load_list; 193 llist != NULL; 194 llist = llist->next) { 195 if (!(llist->prot & PROT_WRITE)) 196 _dl_mprotect(llist->start, llist->size, 197 PROT_READ | PROT_WRITE); 198 } 199 } 200 201 /* tight loop for leading RELATIVE relocs */ 202 for (i = 0; i < relrel; i++, rels++) { 203 Elf_Addr *where; 204 205 #ifdef DEBUG 206 if (ELF_R_TYPE(rels->r_info) != R_TYPE(RELATIVE)) { 207 _dl_printf("RELCOUNT wrong\n"); 208 _dl_exit(20); 209 } 210 #endif 211 where = (Elf_Addr *)(rels->r_offset + loff); 212 *where += loff; 213 } 214 for (; i < numrel; i++, rels++) { 215 Elf_Addr *where, value, ooff, mask; 216 Elf_Word type; 217 const Elf_Sym *sym, *this; 218 const char *symn; 219 220 type = ELF_R_TYPE(rels->r_info); 221 222 if (reloc_target_flags[type] & _RF_E) { 223 _dl_printf(" bad relocation %d %d\n", i, type); 224 _dl_exit(1); 225 } 226 if (type == R_TYPE(NONE)) 227 continue; 228 229 if (type == R_TYPE(JUMP_SLOT) && rel != DT_JMPREL) 230 continue; 231 232 where = (Elf_Addr *)(rels->r_offset + loff); 233 234 if (RELOC_USE_ADDEND(type)) 235 #ifdef LDSO_ARCH_IS_RELA_ 236 value = rels->r_addend; 237 #else 238 value = *where & RELOC_VALUE_BITMASK(type); 239 #endif 240 else 241 value = 0; 242 243 sym = NULL; 244 symn = NULL; 245 if (RELOC_RESOLVE_SYMBOL(type)) { 246 sym = object->dyn.symtab; 247 sym += ELF_R_SYM(rels->r_info); 248 symn = object->dyn.strtab + sym->st_name; 249 250 if (sym->st_shndx != SHN_UNDEF && 251 ELF_ST_BIND(sym->st_info) == STB_LOCAL) { 252 value += loff; 253 } else if (sym == prev_sym) { 254 value += prev_value; 255 } else { 256 this = NULL; 257 ooff = _dl_find_symbol_bysym(object, 258 ELF_R_SYM(rels->r_info), &this, 259 SYM_SEARCH_ALL|SYM_WARNNOTFOUND| 260 ((type == R_TYPE(JUMP_SLOT)) ? 261 SYM_PLT : SYM_NOTPLT), 262 sym, NULL); 263 if (this == NULL) { 264 resolve_failed: 265 if (ELF_ST_BIND(sym->st_info) != 266 STB_WEAK) 267 fails++; 268 continue; 269 } 270 prev_sym = sym; 271 prev_value = (Elf_Addr)(ooff + this->st_value); 272 value += prev_value; 273 } 274 } 275 276 if (type == R_TYPE(JUMP_SLOT)) { 277 /* 278 _dl_reloc_plt((Elf_Word *)where, value, rels); 279 */ 280 *where = value; 281 continue; 282 } 283 284 if (type == R_TYPE(COPY)) { 285 void *dstaddr = where; 286 const void *srcaddr; 287 const Elf_Sym *dstsym = sym, *srcsym = NULL; 288 Elf_Addr soff; 289 290 soff = _dl_find_symbol(symn, &srcsym, 291 SYM_SEARCH_OTHER|SYM_WARNNOTFOUND|SYM_NOTPLT, 292 dstsym, object, NULL); 293 if (srcsym == NULL) 294 goto resolve_failed; 295 296 srcaddr = (void *)(soff + srcsym->st_value); 297 _dl_bcopy(srcaddr, dstaddr, dstsym->st_size); 298 continue; 299 } 300 301 if (RELOC_PC_RELATIVE(type)) 302 value -= (Elf_Addr)where; 303 if (RELOC_BASE_RELATIVE(type)) 304 value += loff; 305 306 mask = RELOC_VALUE_BITMASK(type); 307 value >>= RELOC_VALUE_RIGHTSHIFT(type); 308 value &= mask; 309 310 if (RELOC_UNALIGNED(type)) { 311 /* Handle unaligned relocations. */ 312 Elf_Addr tmp = 0; 313 char *ptr = (char *)where; 314 int i, size = RELOC_TARGET_SIZE(type)/8; 315 316 /* Read it in one byte at a time. */ 317 for (i=0; i<size; i++) 318 tmp = (tmp << 8) | ptr[i]; 319 320 tmp &= ~mask; 321 tmp |= value; 322 323 /* Write it back out. */ 324 for (i=0; i<size; i++) 325 ptr[i] = ((tmp >> (8*i)) & 0xff); 326 } else { 327 *where &= ~mask; 328 *where |= value; 329 } 330 } 331 332 /* reprotect the unprotected segments */ 333 if ((object->dyn.textrel == 1) && (rel == DT_REL || rel == DT_RELA)) { 334 for (llist = object->load_list; 335 llist != NULL; 336 llist = llist->next) { 337 if (!(llist->prot & PROT_WRITE)) 338 _dl_mprotect(llist->start, llist->size, 339 llist->prot); 340 } 341 } 342 343 return (fails); 344 } 345 346 /* 347 * Relocate the Global Offset Table (GOT). 348 * This is done by calling _dl_md_reloc on DT_JMPREL for DL_BIND_NOW, 349 * otherwise the lazy binding plt initialization is performed. 350 */ 351 int 352 _dl_md_reloc_got(elf_object_t *object, int lazy) 353 { 354 int fails = 0; 355 Elf_Addr *pltgot = (Elf_Addr *)object->Dyn.info[DT_PLTGOT]; 356 int i, num; 357 Elf_Rel *rel; 358 359 if (object->Dyn.info[DT_PLTREL] != DT_REL) 360 return (0); 361 362 if (object->traced) 363 lazy = 1; 364 365 if (!lazy) { 366 fails = _dl_md_reloc(object, DT_JMPREL, DT_PLTRELSZ); 367 } else { 368 rel = (Elf_Rel *)(object->Dyn.info[DT_JMPREL]); 369 num = (object->Dyn.info[DT_PLTRELSZ]); 370 371 for (i = 0; i < num/sizeof(Elf_Rel); i++, rel++) { 372 Elf_Addr *where; 373 where = (Elf_Addr *)(rel->r_offset + object->obj_base); 374 *where += object->obj_base; 375 } 376 377 pltgot[1] = (Elf_Addr)object; 378 pltgot[2] = (Elf_Addr)_dl_bind_start; 379 } 380 381 /* mprotect the GOT */ 382 _dl_protect_segment(object, 0, "__got_start", "__got_end", PROT_READ); 383 384 return (fails); 385 } 386 387 Elf_Addr 388 _dl_bind(elf_object_t *object, int relidx) 389 { 390 Elf_Rel *rel; 391 const Elf_Sym *sym, *this; 392 const char *symn; 393 const elf_object_t *sobj; 394 Elf_Addr ooff; 395 int64_t cookie = pcookie; 396 struct { 397 struct __kbind param; 398 Elf_Word newval; 399 } buf; 400 401 rel = ((Elf_Rel *)object->Dyn.info[DT_JMPREL]) + (relidx); 402 403 sym = object->dyn.symtab; 404 sym += ELF_R_SYM(rel->r_info); 405 symn = object->dyn.strtab + sym->st_name; 406 407 this = NULL; 408 ooff = _dl_find_symbol(symn, &this, 409 SYM_SEARCH_ALL|SYM_WARNNOTFOUND|SYM_PLT, sym, object, &sobj); 410 if (this == NULL) { 411 _dl_printf("lazy binding failed!\n"); 412 *(volatile int *)0 = 0; /* XXX */ 413 } 414 415 buf.newval = ooff + this->st_value; 416 417 if (__predict_false(sobj->traced) && _dl_trace_plt(sobj, symn)) 418 return (buf.newval); 419 420 buf.param.kb_addr = (Elf_Addr *)(object->obj_base + rel->r_offset); 421 buf.param.kb_size = sizeof(Elf_Word); 422 423 /* directly code the syscall, so that it's actually inline here */ 424 { 425 register long syscall_num __asm("r12") = SYS_kbind; 426 register void *arg1 __asm("r0") = &buf; 427 register long arg2 __asm("r1") = sizeof(buf); 428 register long arg3 __asm("r2") = 0xffffffff & cookie; 429 register long arg4 __asm("r3") = 0xffffffff & (cookie >> 32); 430 431 __asm volatile("swi 0" : "+r" (arg1), "+r" (arg2) 432 : "r" (syscall_num), "r" (arg3), "r" (arg4) 433 : "cc", "memory"); 434 } 435 436 return (buf.newval); 437 } 438