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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 | /* -*- mode: C++; c-basic-offset: 4; tab-width: 4 -*- * * Copyright (c) 2004-2008 Apple Inc. All rights reserved. * * @APPLE_LICENSE_HEADER_START@ * * This file contains Original Code and/or Modifications of Original Code * as defined in and that are subject to the Apple Public Source License * Version 2.0 (the 'License'). You may not use this file except in * compliance with the License. Please obtain a copy of the License at * http://www.opensource.apple.com/apsl/ and read it before using this * file. * * The Original Code and all software distributed under the License are * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT. * Please see the License for the specific language governing rights and * limitations under the License. * * @APPLE_LICENSE_HEADER_END@ */ #define __STDC_LIMIT_MACROS #include <stdint.h> #include <stddef.h> #include <string.h> #include <stdlib.h> #include <Availability.h> #include <mach/mach.h> #include <mach-o/loader.h> #include <mach-o/ldsyms.h> #include <mach-o/reloc.h> #if __x86_64__ #include <mach-o/x86_64/reloc.h> #endif #include "dyld.h" #include "dyldSyscallInterface.h" // from dyld_gdb.cpp extern void addImagesToAllImages(uint32_t infoCount, const dyld_image_info info[]); extern void syncProcessInfo(); #ifndef MH_PIE #define MH_PIE 0x200000 #endif // currently dyld has no initializers, but if some come back, set this to non-zero #define DYLD_INITIALIZER_SUPPORT 0 #if __LP64__ #define LC_SEGMENT_COMMAND LC_SEGMENT_64 #define macho_segment_command segment_command_64 #define macho_section section_64 #define RELOC_SIZE 3 #else #define LC_SEGMENT_COMMAND LC_SEGMENT #define macho_segment_command segment_command #define macho_section section #define RELOC_SIZE 2 #endif #if __x86_64__ #define POINTER_RELOC X86_64_RELOC_UNSIGNED #else #define POINTER_RELOC GENERIC_RELOC_VANILLA #endif #ifndef BIND_OPCODE_THREADED #define BIND_OPCODE_THREADED 0xD0 #endif #ifndef BIND_SUBOPCODE_THREADED_SET_BIND_ORDINAL_TABLE_SIZE_ULEB #define BIND_SUBOPCODE_THREADED_SET_BIND_ORDINAL_TABLE_SIZE_ULEB 0x00 #endif #ifndef BIND_SUBOPCODE_THREADED_APPLY #define BIND_SUBOPCODE_THREADED_APPLY 0x01 #endif #if __has_feature(ptrauth_calls) #include <ptrauth.h> #endif #if TARGET_IPHONE_SIMULATOR const dyld::SyscallHelpers* gSyscallHelpers = NULL; #endif // // Code to bootstrap dyld into a runnable state // // namespace dyldbootstrap { #if DYLD_INITIALIZER_SUPPORT typedef void (*Initializer)(int argc, const char* argv[], const char* envp[], const char* apple[]); extern const Initializer inits_start __asm("section$start$__DATA$__mod_init_func"); extern const Initializer inits_end __asm("section$end$__DATA$__mod_init_func"); // // For a regular executable, the crt code calls dyld to run the executables initializers. // For a static executable, crt directly runs the initializers. // dyld (should be static) but is a dynamic executable and needs this hack to run its own initializers. // We pass argc, argv, etc in case libc.a uses those arguments // static void runDyldInitializers(const struct macho_header* mh, intptr_t slide, int argc, const char* argv[], const char* envp[], const char* apple[]) { for (const Initializer* p = &inits_start; p < &inits_end; ++p) { (*p)(argc, argv, envp, apple); } } #endif // DYLD_INITIALIZER_SUPPORT // // The kernel may have slid a Position Independent Executable // static uintptr_t slideOfMainExecutable(const struct macho_header* mh) { const uint32_t cmd_count = mh->ncmds; const struct load_command* const cmds = (struct load_command*)(((char*)mh)+sizeof(macho_header)); const struct load_command* cmd = cmds; for (uint32_t i = 0; i < cmd_count; ++i) { if ( cmd->cmd == LC_SEGMENT_COMMAND ) { const struct macho_segment_command* segCmd = (struct macho_segment_command*)cmd; if ( (segCmd->fileoff == 0) && (segCmd->filesize != 0)) { return (uintptr_t)mh - segCmd->vmaddr; } } cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize); } return 0; } inline uint64_t read_uleb128(const uint8_t*& p, const uint8_t* end) { uint64_t result = 0; int bit = 0; do { if (p == end) throw "malformed uleb128 extends beyond trie"; uint64_t slice = *p & 0x7f; if (bit >= 64 || slice << bit >> bit != slice) throw "uleb128 too big for 64-bits"; else { result |= (slice << bit); bit += 7; } } while (*p++ & 0x80); return result; } inline int64_t read_sleb128(const uint8_t*& p, const uint8_t* end) { int64_t result = 0; int bit = 0; uint8_t byte; do { if (p == end) throw "malformed sleb128"; byte = *p++; result |= (((int64_t)(byte & 0x7f)) << bit); bit += 7; } while (byte & 0x80); // sign extend negative numbers if ( (byte & 0x40) != 0 ) result |= (~0ULL) << bit; return result; } // // If the kernel does not load dyld at its preferred address, we need to apply // fixups to various initialized parts of the __DATA segment // static void rebaseDyld(const struct macho_header* mh, intptr_t slide) { // rebase non-lazy pointers (which all point internal to dyld, since dyld uses no shared libraries) // and get interesting pointers into dyld const uint32_t cmd_count = mh->ncmds; const struct load_command* const cmds = (struct load_command*)(((char*)mh)+sizeof(macho_header)); const struct load_command* cmd = cmds; // First look for compressed info and use it if it exists. const struct macho_segment_command* linkEditSeg = NULL; const dyld_info_command* dyldInfoCmd = NULL; for (uint32_t i = 0; i < cmd_count; ++i) { switch (cmd->cmd) { case LC_SEGMENT_COMMAND: { const struct macho_segment_command* seg = (struct macho_segment_command*)cmd; if ( strcmp(seg->segname, "__LINKEDIT") == 0 ) linkEditSeg = seg; break; } case LC_DYLD_INFO_ONLY: dyldInfoCmd = (struct dyld_info_command*)cmd; break; } if (dyldInfoCmd && linkEditSeg) break; cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize); } if ( linkEditSeg == NULL ) throw "dyld missing LINKEDIT"; // Reset the iterator. cmd = cmds; auto getSegmentAtIndex = [cmd_count, cmds](unsigned segIndex) -> const struct macho_segment_command* { const struct load_command* cmd = cmds; for (uint32_t i = 0; i < cmd_count; ++i) { switch (cmd->cmd) { case LC_SEGMENT_COMMAND: if (!segIndex) { const struct macho_segment_command* seg = (struct macho_segment_command*)cmd; return seg; } --segIndex; break; } cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize); } throw "out of bounds command"; return 0; }; auto segActualLoadAddress = [&](unsigned segIndex) -> uintptr_t { const struct macho_segment_command* seg = getSegmentAtIndex(segIndex); return seg->vmaddr + slide; }; #if __has_feature(ptrauth_calls) auto imageBaseAddress = [cmds, cmd_count]() -> uintptr_t { const struct load_command* cmd = cmds; for (uint32_t i = 0; i < cmd_count; ++i) { switch (cmd->cmd) { case LC_SEGMENT_COMMAND: { const struct macho_segment_command* seg = (struct macho_segment_command*)cmd; if ( (seg->fileoff == 0) && (seg->filesize != 0) ) return seg->vmaddr; break; } } cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize); } return 0; }; #endif if (dyldInfoCmd && (dyldInfoCmd->bind_size != 0) ) { if ( dyldInfoCmd->rebase_size != 0 ) throw "unthreaded rebases are not supported"; const uint8_t* linkEditBase = (uint8_t*)(linkEditSeg->vmaddr + slide - linkEditSeg->fileoff); const uint8_t* const start = linkEditBase + dyldInfoCmd->bind_off; const uint8_t* const end = &start[dyldInfoCmd->bind_size]; const uint8_t* p = start; uintptr_t segmentStartAddress = 0; uint64_t segOffset = 0; int segIndex = 0; #if __has_feature(ptrauth_calls) uintptr_t fBaseAddress = imageBaseAddress(); #endif bool done = false; while ( !done && (p < end) ) { uint8_t immediate = *p & BIND_IMMEDIATE_MASK; uint8_t opcode = *p & BIND_OPCODE_MASK; ++p; switch (opcode) { case BIND_OPCODE_DONE: done = true; break; case BIND_OPCODE_SET_DYLIB_ORDINAL_IMM: break; case BIND_OPCODE_SET_DYLIB_ORDINAL_ULEB: break; case BIND_OPCODE_SET_DYLIB_SPECIAL_IMM: break; case BIND_OPCODE_SET_SYMBOL_TRAILING_FLAGS_IMM: while (*p != '\0') ++p; ++p; break; case BIND_OPCODE_SET_TYPE_IMM: break; case BIND_OPCODE_SET_ADDEND_SLEB: read_sleb128(p, end); break; case BIND_OPCODE_SET_SEGMENT_AND_OFFSET_ULEB: segIndex = immediate; segmentStartAddress = segActualLoadAddress(segIndex); segOffset = read_uleb128(p, end); break; case BIND_OPCODE_ADD_ADDR_ULEB: segOffset += read_uleb128(p, end); break; case BIND_OPCODE_DO_BIND: break; case BIND_OPCODE_DO_BIND_ADD_ADDR_ULEB: break; case BIND_OPCODE_DO_BIND_ADD_ADDR_IMM_SCALED: break; case BIND_OPCODE_DO_BIND_ULEB_TIMES_SKIPPING_ULEB: read_uleb128(p, end); read_uleb128(p, end); break; case BIND_OPCODE_THREADED: // Note the immediate is a sub opcode switch (immediate) { case BIND_SUBOPCODE_THREADED_SET_BIND_ORDINAL_TABLE_SIZE_ULEB: read_uleb128(p, end); break; case BIND_SUBOPCODE_THREADED_APPLY: { uint64_t delta = 0; do { uintptr_t address = segmentStartAddress + (uintptr_t)segOffset; uint64_t value = *(uint64_t*)address; #if __has_feature(ptrauth_calls) uint16_t diversity = (uint16_t)(value >> 32); bool hasAddressDiversity = (value & (1ULL << 48)) != 0; ptrauth_key key = (ptrauth_key)((value >> 49) & 0x3); bool isAuthenticated = (value & (1ULL << 63)) != 0; #endif bool isRebase = (value & (1ULL << 62)) == 0; if (isRebase) { #if __has_feature(ptrauth_calls) if (isAuthenticated) { // The new value for a rebase is the low 32-bits of the threaded value plus the slide. uint64_t newValue = (value & 0xFFFFFFFF) + slide; // Add in the offset from the mach_header newValue += fBaseAddress; // We have bits to merge in to the discriminator uintptr_t discriminator = diversity; if (hasAddressDiversity) { // First calculate a new discriminator using the address of where we are trying to store the value discriminator = __builtin_ptrauth_blend_discriminator((void*)address, discriminator); } switch (key) { case ptrauth_key_asia: newValue = (uintptr_t)__builtin_ptrauth_sign_unauthenticated((void*)newValue, ptrauth_key_asia, discriminator); break; case ptrauth_key_asib: newValue = (uintptr_t)__builtin_ptrauth_sign_unauthenticated((void*)newValue, ptrauth_key_asib, discriminator); break; case ptrauth_key_asda: newValue = (uintptr_t)__builtin_ptrauth_sign_unauthenticated((void*)newValue, ptrauth_key_asda, discriminator); break; case ptrauth_key_asdb: newValue = (uintptr_t)__builtin_ptrauth_sign_unauthenticated((void*)newValue, ptrauth_key_asdb, discriminator); break; } *(uint64_t*)address = newValue; } else #endif { // Regular pointer which needs to fit in 51-bits of value. // C++ RTTI uses the top bit, so we'll allow the whole top-byte // and the signed-extended bottom 43-bits to be fit in to 51-bits. uint64_t top8Bits = value & 0x0007F80000000000ULL; uint64_t bottom43Bits = value & 0x000007FFFFFFFFFFULL; uint64_t targetValue = ( top8Bits << 13 ) | (((intptr_t)(bottom43Bits << 21) >> 21) & 0x00FFFFFFFFFFFFFF); targetValue = targetValue + slide; *(uint64_t*)address = targetValue; } } // The delta is bits [51..61] // And bit 62 is to tell us if we are a rebase (0) or bind (1) value &= ~(1ULL << 62); delta = ( value & 0x3FF8000000000000 ) >> 51; segOffset += delta * sizeof(uintptr_t); } while ( delta != 0 ); break; } default: throw "unknown threaded bind subopcode"; } break; default: throw "unknown bind opcode"; } } return; } #if __x86_64__ const struct macho_segment_command* firstWritableSeg = NULL; #endif const struct dysymtab_command* dynamicSymbolTable = NULL; for (uint32_t i = 0; i < cmd_count; ++i) { switch (cmd->cmd) { case LC_SEGMENT_COMMAND: { const struct macho_segment_command* seg = (struct macho_segment_command*)cmd; const struct macho_section* const sectionsStart = (struct macho_section*)((char*)seg + sizeof(struct macho_segment_command)); const struct macho_section* const sectionsEnd = §ionsStart[seg->nsects]; for (const struct macho_section* sect=sectionsStart; sect < sectionsEnd; ++sect) { const uint8_t type = sect->flags & SECTION_TYPE; if ( type == S_NON_LAZY_SYMBOL_POINTERS ) { // rebase non-lazy pointers (which all point internal to dyld, since dyld uses no shared libraries) const uint32_t pointerCount = (uint32_t)(sect->size / sizeof(uintptr_t)); uintptr_t* const symbolPointers = (uintptr_t*)(sect->addr + slide); for (uint32_t j=0; j < pointerCount; ++j) { symbolPointers[j] += slide; } } } #if __x86_64__ if ( (firstWritableSeg == NULL) && (seg->initprot & VM_PROT_WRITE) ) firstWritableSeg = seg; #endif } break; case LC_DYSYMTAB: dynamicSymbolTable = (struct dysymtab_command *)cmd; break; } cmd = (const struct load_command*)(((char*)cmd)+cmd->cmdsize); } // use reloc's to rebase all random data pointers #if __x86_64__ if ( firstWritableSeg == NULL ) throw "no writable segment in dyld"; const uintptr_t relocBase = firstWritableSeg->vmaddr + slide; #else const uintptr_t relocBase = (uintptr_t)mh; #endif const relocation_info* const relocsStart = (struct relocation_info*)(linkEditSeg->vmaddr + slide + dynamicSymbolTable->locreloff - linkEditSeg->fileoff); const relocation_info* const relocsEnd = &relocsStart[dynamicSymbolTable->nlocrel]; for (const relocation_info* reloc=relocsStart; reloc < relocsEnd; ++reloc) { if ( reloc->r_length != RELOC_SIZE ) throw "relocation in dyld has wrong size"; if ( reloc->r_type != POINTER_RELOC ) throw "relocation in dyld has wrong type"; // update pointer by amount dyld slid *((uintptr_t*)(reloc->r_address + relocBase)) += slide; } } extern "C" void mach_init(); extern "C" void __guard_setup(const char* apple[]); // // This is code to bootstrap dyld. This work in normally done for a program by dyld and crt. // In dyld we have to do this manually. // uintptr_t start(const struct macho_header* appsMachHeader, int argc, const char* argv[], intptr_t slide, const struct macho_header* dyldsMachHeader, uintptr_t* startGlue) { // if kernel had to slide dyld, we need to fix up load sensitive locations // we have to do this before using any global variables slide = slideOfMainExecutable(dyldsMachHeader); bool shouldRebase = slide != 0; #if __has_feature(ptrauth_calls) shouldRebase = true; #endif if ( shouldRebase ) { rebaseDyld(dyldsMachHeader, slide); } // allow dyld to use mach messaging mach_init(); // kernel sets up env pointer to be just past end of agv array const char** envp = &argv[argc+1]; // kernel sets up apple pointer to be just past end of envp array const char** apple = envp; while(*apple != NULL) { ++apple; } ++apple; // set up random value for stack canary __guard_setup(apple); #if DYLD_INITIALIZER_SUPPORT // run all C++ initializers inside dyld runDyldInitializers(dyldsMachHeader, slide, argc, argv, envp, apple); #endif // now that we are done bootstrapping dyld, call dyld's main uintptr_t appsSlide = slideOfMainExecutable(appsMachHeader); return dyld::_main(appsMachHeader, appsSlide, argc, argv, envp, apple, startGlue); } #if TARGET_IPHONE_SIMULATOR extern "C" uintptr_t start_sim(int argc, const char* argv[], const char* envp[], const char* apple[], const macho_header* mainExecutableMH, const macho_header* dyldMH, uintptr_t dyldSlide, const dyld::SyscallHelpers*, uintptr_t* startGlue); uintptr_t start_sim(int argc, const char* argv[], const char* envp[], const char* apple[], const macho_header* mainExecutableMH, const macho_header* dyldMH, uintptr_t dyldSlide, const dyld::SyscallHelpers* sc, uintptr_t* startGlue) { // if simulator dyld loaded slid, it needs to rebase itself // we have to do this before using any global variables if ( dyldSlide != 0 ) { rebaseDyld(dyldMH, dyldSlide); } // save table of syscall pointers gSyscallHelpers = sc; // allow dyld to use mach messaging mach_init(); // set up random value for stack canary __guard_setup(apple); // setup gProcessInfo to point to host dyld's struct dyld::gProcessInfo = (struct dyld_all_image_infos*)(sc->getProcessInfo()); syncProcessInfo(); // now that we are done bootstrapping dyld, call dyld's main uintptr_t appsSlide = slideOfMainExecutable(mainExecutableMH); return dyld::_main(mainExecutableMH, appsSlide, argc, argv, envp, apple, startGlue); } #endif } // end of namespace |