plt.c revision 8557b4a1a6f2a6d12867ee57b417e3e941963721
1#include <gelf.h> 2#include <sys/ptrace.h> 3#include <errno.h> 4#include <error.h> 5#include <inttypes.h> 6#include <assert.h> 7#include <string.h> 8 9#include "proc.h" 10#include "common.h" 11#include "library.h" 12#include "breakpoint.h" 13#include "linux-gnu/trace.h" 14 15/* There are two PLT types on 32-bit PPC: old-style, BSS PLT, and 16 * new-style "secure" PLT. We can tell one from the other by the 17 * flags on the .plt section. If it's +X (executable), it's BSS PLT, 18 * otherwise it's secure. 19 * 20 * BSS PLT works the same way as most architectures: the .plt section 21 * contains trampolines and we put breakpoints to those. If not 22 * prelinked, .plt contains zeroes, and dynamic linker fills in the 23 * initial set of trampolines, which means that we need to delay 24 * enabling breakpoints until after binary entry point is hit. 25 * Additionally, after first call, dynamic linker updates .plt with 26 * branch to resolved address. That means that on first hit, we must 27 * do something similar to the PPC64 gambit described below. 28 * 29 * With secure PLT, the .plt section doesn't contain instructions but 30 * addresses. The real PLT table is stored in .text. Addresses of 31 * those PLT entries can be computed, and apart from the fact that 32 * they are in .text, they are ordinary PLT entries. 33 * 34 * 64-bit PPC is more involved. Program linker creates for each 35 * library call a _stub_ symbol named xxxxxxxx.plt_call.<callee> 36 * (where xxxxxxxx is a hexadecimal number). That stub does the call 37 * dispatch: it loads an address of a function to call from the 38 * section .plt, and branches. PLT entries themselves are essentially 39 * a curried call to the resolver. When the symbol is resolved, the 40 * resolver updates the value stored in .plt, and the next time 41 * around, the stub calls the library function directly. So we make 42 * at most one trip (none if the binary is prelinked) through each PLT 43 * entry, and correspondingly that is useless as a breakpoint site. 44 * 45 * Note the three confusing terms: stubs (that play the role of PLT 46 * entries), PLT entries, .plt section. 47 * 48 * We first check symbol tables and see if we happen to have stub 49 * symbols available. If yes we just put breakpoints to those, and 50 * treat them as usual breakpoints. The only tricky part is realizing 51 * that there can be more than one breakpoint per symbol. 52 * 53 * The case that we don't have the stub symbols available is harder. 54 * The following scheme uses two kinds of PLT breakpoints: unresolved 55 * and resolved (to some address). When the process starts (or when 56 * we attach), we distribute unresolved PLT breakpoints to the PLT 57 * entries (not stubs). Then we look in .plt, and for each entry 58 * whose value is different than the corresponding PLT entry address, 59 * we assume it was already resolved, and convert the breakpoint to 60 * resolved. We also rewrite the resolved value in .plt back to the 61 * PLT address. 62 * 63 * When a PLT entry hits a resolved breakpoint (which happens because 64 * we rewrite .plt with the original unresolved addresses), we move 65 * the instruction pointer to the corresponding address and continue 66 * the process as if nothing happened. 67 * 68 * When unresolved PLT entry is called for the first time, we need to 69 * catch the new value that the resolver will write to a .plt slot. 70 * We also need to prevent another thread from racing through and 71 * taking the branch without ltrace noticing. So when unresolved PLT 72 * entry hits, we have to stop all threads. We then single-step 73 * through the resolver, until the .plt slot changes. When it does, 74 * we treat it the same way as above: convert the PLT breakpoint to 75 * resolved, and rewrite the .plt value back to PLT address. We then 76 * start all threads again. 77 * 78 * As an optimization, we remember the address where the address was 79 * resolved, and put a breakpoint there. The next time around (when 80 * the next PLT entry is to be resolved), instead of single-stepping 81 * through half the dynamic linker, we just let the thread run and hit 82 * this breakpoint. When it hits, we know the PLT entry was resolved. 83 * 84 * N.B. It's tempting to try to emulate the instruction that updates 85 * .plt. We would compute the resolved address, and instead of 86 * letting the dynamic linker put it in .plt, we would resolve the 87 * breakpoint to that address. This way we wouldn't need to stop 88 * other threads. However that instruction may turn out to be a sync, 89 * and in general, may be any instruction between the actual write and 90 * the following sync. XXX TODO that means that we need to put the 91 * post-enable breakpoint at the following sync, not to the 92 * instruction itself (unless it's a sync already). 93 * 94 * XXX TODO If we have hardware watch point, we might put a read watch 95 * on .plt slot, and discover the offenders this way. I don't know 96 * the details, but I assume at most a handful (like, one or two, if 97 * available at all) addresses may be watched at a time, and thus this 98 * would be used as an amendment of the above rather than full-on 99 * solution to PLT tracing on PPC. 100 */ 101 102#define PPC_PLT_STUB_SIZE 16 103#define PPC64_PLT_STUB_SIZE 8 //xxx 104 105static inline int 106host_powerpc64() 107{ 108#ifdef __powerpc64__ 109 return 1; 110#else 111 return 0; 112#endif 113} 114 115static int 116read_target_4(struct Process *proc, target_address_t addr, uint32_t *lp) 117{ 118 unsigned long l = ptrace(PTRACE_PEEKTEXT, proc->pid, addr, 0); 119 if (l == -1UL && errno) 120 return -1; 121 if (host_powerpc64()) 122 l >>= 32; 123 *lp = l; 124 return 0; 125} 126 127static int 128read_target_8(struct Process *proc, target_address_t addr, uint64_t *lp) 129{ 130 assert(host_powerpc64()); 131 unsigned long l = ptrace(PTRACE_PEEKTEXT, proc->pid, addr, 0); 132 if (l == -1UL && errno) 133 return -1; 134 *lp = l; 135 return 0; 136} 137 138static int 139read_target_long(struct Process *proc, target_address_t addr, uint64_t *lp) 140{ 141 if (proc->e_machine == EM_PPC) { 142 uint32_t w; 143 int ret = read_target_4(proc, addr, &w); 144 if (ret >= 0) 145 *lp = (uint64_t)w; 146 return ret; 147 } else { 148 return read_target_8(proc, addr, lp); 149 } 150} 151 152static enum callback_status 153reenable_breakpoint(struct Process *proc, struct breakpoint *bp, void *data) 154{ 155 /* We don't need to re-enable non-PLT breakpoints and 156 * breakpoints that are not PPC32 BSS unprelinked. */ 157 if (bp->libsym == NULL 158 || bp->libsym->plt_type == LS_TOPLT_NONE 159 || bp->libsym->lib->arch.bss_plt_prelinked != 0) 160 return CBS_CONT; 161 162 debug(DEBUG_PROCESS, "pid=%d reenable_breakpoint %s", 163 proc->pid, breakpoint_name(bp)); 164 165 assert(proc->e_machine == EM_PPC); 166 uint32_t l; 167 if (read_target_4(proc, bp->addr, &l) < 0) { 168 error(0, errno, "couldn't read PLT value for %s(%p)", 169 breakpoint_name(bp), bp->addr); 170 return CBS_CONT; 171 } 172 bp->libsym->arch.plt_slot_addr = (GElf_Addr)bp->addr; 173 bp->libsym->arch.resolved_value = l; 174 175 /* Re-enable the breakpoint that was overwritten by the 176 * dynamic linker. XXX unfortunately it's overwritten 177 * again after the first call :-/ */ 178 enable_breakpoint(proc, bp); 179 180 return CBS_CONT; 181} 182 183void 184arch_dynlink_done(struct Process *proc) 185{ 186 /* On PPC32, .plt of objects that use BSS PLT are overwritten 187 * by the dynamic linker (unless that object was prelinked). 188 * We need to re-enable breakpoints in those objects. */ 189 proc_each_breakpoint(proc, NULL, reenable_breakpoint, NULL); 190} 191 192GElf_Addr 193arch_plt_sym_val(struct ltelf *lte, size_t ndx, GElf_Rela *rela) 194{ 195 if (lte->ehdr.e_machine == EM_PPC && lte->arch.secure_plt) { 196 assert(lte->arch.plt_stub_vma != 0); 197 return lte->arch.plt_stub_vma + PPC_PLT_STUB_SIZE * ndx; 198 199 } else if (lte->ehdr.e_machine == EM_PPC) { 200 return rela->r_offset; 201 202 } else { 203 /* If we get here, we don't have stub symbols. In 204 * that case we put brakpoints to PLT entries the same 205 * as the PPC32 secure PLT case does. */ 206 assert(lte->arch.plt_stub_vma != 0); 207 return lte->arch.plt_stub_vma + PPC64_PLT_STUB_SIZE * ndx; 208 } 209} 210 211int 212arch_translate_address(struct Process *proc, 213 target_address_t addr, target_address_t *ret) 214{ 215 if (proc->e_machine == EM_PPC64) { 216 assert(host_powerpc64()); 217 long l = ptrace(PTRACE_PEEKTEXT, proc->pid, addr, 0); 218 if (l == -1 && errno) { 219 error(0, errno, ".opd translation of %p", addr); 220 return -1; 221 } 222 *ret = (target_address_t)l; 223 return 0; 224 } 225 226 *ret = addr; 227 return 0; 228} 229 230void * 231sym2addr(struct Process *proc, struct library_symbol *sym) 232{ 233 return sym->enter_addr; 234} 235 236static GElf_Addr 237get_glink_vma(struct ltelf *lte, GElf_Addr ppcgot, Elf_Data *plt_data) 238{ 239 Elf_Scn *ppcgot_sec = NULL; 240 GElf_Shdr ppcgot_shdr; 241 if (ppcgot != 0 242 && elf_get_section_covering(lte, ppcgot, 243 &ppcgot_sec, &ppcgot_shdr) < 0) 244 error(0, 0, "DT_PPC_GOT=%#"PRIx64", but no such section found", 245 ppcgot); 246 247 if (ppcgot_sec != NULL) { 248 Elf_Data *data = elf_loaddata(ppcgot_sec, &ppcgot_shdr); 249 if (data == NULL || data->d_size < 8 ) { 250 error(0, 0, "couldn't read GOT data"); 251 } else { 252 // where PPCGOT begins in .got 253 size_t offset = ppcgot - ppcgot_shdr.sh_addr; 254 assert(offset % 4 == 0); 255 uint32_t glink_vma; 256 if (elf_read_u32(data, offset + 4, &glink_vma) < 0) { 257 error(0, 0, "couldn't read glink VMA address" 258 " at %zd@GOT", offset); 259 return 0; 260 } 261 if (glink_vma != 0) { 262 debug(1, "PPC GOT glink_vma address: %#" PRIx32, 263 glink_vma); 264 return (GElf_Addr)glink_vma; 265 } 266 } 267 } 268 269 if (plt_data != NULL) { 270 uint32_t glink_vma; 271 if (elf_read_u32(plt_data, 0, &glink_vma) < 0) { 272 error(0, 0, "couldn't read glink VMA address"); 273 return 0; 274 } 275 debug(1, ".plt glink_vma address: %#" PRIx32, glink_vma); 276 return (GElf_Addr)glink_vma; 277 } 278 279 return 0; 280} 281 282static int 283load_dynamic_entry(struct ltelf *lte, int tag, GElf_Addr *valuep) 284{ 285 Elf_Scn *scn; 286 GElf_Shdr shdr; 287 if (elf_get_section_type(lte, SHT_DYNAMIC, &scn, &shdr) < 0 288 || scn == NULL) { 289 fail: 290 error(0, 0, "Couldn't get SHT_DYNAMIC: %s", 291 elf_errmsg(-1)); 292 return -1; 293 } 294 295 Elf_Data *data = elf_loaddata(scn, &shdr); 296 if (data == NULL) 297 goto fail; 298 299 size_t j; 300 for (j = 0; j < shdr.sh_size / shdr.sh_entsize; ++j) { 301 GElf_Dyn dyn; 302 if (gelf_getdyn(data, j, &dyn) == NULL) 303 goto fail; 304 305 if(dyn.d_tag == tag) { 306 *valuep = dyn.d_un.d_ptr; 307 return 0; 308 } 309 } 310 311 return -1; 312} 313 314static int 315load_ppcgot(struct ltelf *lte, GElf_Addr *ppcgotp) 316{ 317 return load_dynamic_entry(lte, DT_PPC_GOT, ppcgotp); 318} 319 320static int 321load_ppc64_glink(struct ltelf *lte, GElf_Addr *glinkp) 322{ 323 return load_dynamic_entry(lte, DT_PPC64_GLINK, glinkp); 324} 325 326static int 327nonzero_data(Elf_Data *data) 328{ 329 /* We are not supposed to get here if there's no PLT. */ 330 assert(data != NULL); 331 332 unsigned char *buf = data->d_buf; 333 if (buf == NULL) 334 return 0; 335 336 size_t i; 337 for (i = 0; i < data->d_size; ++i) 338 if (buf[i] != 0) 339 return 1; 340 return 0; 341} 342 343int 344arch_elf_init(struct ltelf *lte, struct library *lib) 345{ 346 lte->arch.secure_plt = !(lte->plt_flags & SHF_EXECINSTR); 347 348 /* For PPC32 BSS, it is important whether the binary was 349 * prelinked. If .plt section is NODATA, or if it contains 350 * zeroes, then this library is not prelinked, and we need to 351 * delay breakpoints. */ 352 if (lte->ehdr.e_machine == EM_PPC && !lte->arch.secure_plt) 353 lib->arch.bss_plt_prelinked = nonzero_data(lte->plt_data); 354 else 355 /* For cases where it's irrelevant, initialize the 356 * value to something conspicuous. */ 357 lib->arch.bss_plt_prelinked = -1; 358 359 if (lte->ehdr.e_machine == EM_PPC && lte->arch.secure_plt) { 360 GElf_Addr ppcgot; 361 if (load_ppcgot(lte, &ppcgot) < 0) { 362 error(0, 0, "couldn't find DT_PPC_GOT"); 363 return -1; 364 } 365 GElf_Addr glink_vma = get_glink_vma(lte, ppcgot, lte->plt_data); 366 367 assert (lte->relplt_size % 12 == 0); 368 size_t count = lte->relplt_size / 12; // size of RELA entry 369 lte->arch.plt_stub_vma = glink_vma 370 - (GElf_Addr)count * PPC_PLT_STUB_SIZE; 371 debug(1, "stub_vma is %#" PRIx64, lte->arch.plt_stub_vma); 372 373 } else if (lte->ehdr.e_machine == EM_PPC64) { 374 GElf_Addr glink_vma; 375 if (load_ppc64_glink(lte, &glink_vma) < 0) { 376 error(0, 0, "couldn't find DT_PPC64_GLINK"); 377 return -1; 378 } 379 380 /* The first glink stub starts at offset 32. */ 381 lte->arch.plt_stub_vma = glink_vma + 32; 382 } 383 384 /* On PPC64, look for stub symbols in symbol table. These are 385 * called: xxxxxxxx.plt_call.callee_name@version+addend. */ 386 if (lte->ehdr.e_machine == EM_PPC64 387 && lte->symtab != NULL && lte->strtab != NULL) { 388 389 /* N.B. We can't simply skip the symbols that we fail 390 * to read or malloc. There may be more than one stub 391 * per symbol name, and if we failed in one but 392 * succeeded in another, the PLT enabling code would 393 * have no way to tell that something is missing. We 394 * could work around that, of course, but it doesn't 395 * seem worth the trouble. So if anything fails, we 396 * just pretend that we don't have stub symbols at 397 * all, as if the binary is stripped. */ 398 399 size_t i; 400 for (i = 0; i < lte->symtab_count; ++i) { 401 GElf_Sym sym; 402 if (gelf_getsym(lte->symtab, i, &sym) == NULL) { 403 struct library_symbol *sym, *next; 404 fail: 405 for (sym = lte->arch.stubs; sym != NULL; ) { 406 next = sym->next; 407 library_symbol_destroy(sym); 408 free(sym); 409 sym = next; 410 } 411 lte->arch.stubs = NULL; 412 break; 413 } 414 415 const char *name = lte->strtab + sym.st_name; 416 417#define STUBN ".plt_call." 418 if ((name = strstr(name, STUBN)) == NULL) 419 continue; 420 name += sizeof(STUBN) - 1; 421#undef STUBN 422 423 size_t len; 424 const char *ver = strchr(name, '@'); 425 if (ver != NULL) { 426 len = ver - name; 427 428 } else { 429 /* If there is "+" at all, check that 430 * the symbol name ends in "+0". */ 431 const char *add = strrchr(name, '+'); 432 if (add != NULL) { 433 assert(strcmp(add, "+0") == 0); 434 len = add - name; 435 } else { 436 len = strlen(name); 437 } 438 } 439 440 char *sym_name = strndup(name, len); 441 struct library_symbol *libsym = malloc(sizeof(*libsym)); 442 if (sym_name == NULL || libsym == NULL) { 443 fail2: 444 free(sym_name); 445 free(libsym); 446 goto fail; 447 } 448 449 /* XXX The double cast should be removed when 450 * target_address_t becomes integral type. */ 451 target_address_t addr = (target_address_t) 452 (uintptr_t)sym.st_value + lte->bias; 453 if (library_symbol_init(libsym, addr, sym_name, 1, 454 LS_TOPLT_EXEC) < 0) 455 goto fail2; 456 libsym->arch.type = PPC64PLT_STUB; 457 libsym->next = lte->arch.stubs; 458 lte->arch.stubs = libsym; 459 } 460 } 461 462 return 0; 463} 464 465static int 466read_plt_slot_value(struct Process *proc, GElf_Addr addr, GElf_Addr *valp) 467{ 468 /* On PPC64, we read from .plt, which contains 8 byte 469 * addresses. On PPC32 we read from .plt, which contains 4 470 * byte instructions. So read_target_long is appropriate. */ 471 uint64_t l; 472 if (read_target_long(proc, (target_address_t)addr, &l) < 0) { 473 error(0, errno, "ptrace .plt slot value @%#" PRIx64, addr); 474 return -1; 475 } 476 477 *valp = (GElf_Addr)l; 478 return 0; 479} 480 481static int 482unresolve_plt_slot(struct Process *proc, GElf_Addr addr, GElf_Addr value) 483{ 484 /* We only modify plt_entry[0], which holds the resolved 485 * address of the routine. We keep the TOC and environment 486 * pointers intact. Hence the only adjustment that we need to 487 * do is to IP. */ 488 if (ptrace(PTRACE_POKETEXT, proc->pid, addr, value) < 0) { 489 error(0, errno, "unresolve .plt slot"); 490 return -1; 491 } 492 return 0; 493} 494 495static void 496mark_as_resolved(struct library_symbol *libsym, GElf_Addr value) 497{ 498 libsym->arch.type = PPC_PLT_RESOLVED; 499 libsym->arch.resolved_value = value; 500} 501 502enum plt_status 503arch_elf_add_plt_entry(struct Process *proc, struct ltelf *lte, 504 const char *a_name, GElf_Rela *rela, size_t ndx, 505 struct library_symbol **ret) 506{ 507 if (lte->ehdr.e_machine == EM_PPC) 508 return plt_default; 509 510 /* PPC64. If we have stubs, we return a chain of breakpoint 511 * sites, one for each stub that corresponds to this PLT 512 * entry. */ 513 struct library_symbol *chain = NULL; 514 struct library_symbol **symp; 515 for (symp = <e->arch.stubs; *symp != NULL; ) { 516 struct library_symbol *sym = *symp; 517 if (strcmp(sym->name, a_name) != 0) { 518 symp = &(*symp)->next; 519 continue; 520 } 521 522 /* Re-chain the symbol from stubs to CHAIN. */ 523 *symp = sym->next; 524 sym->next = chain; 525 chain = sym; 526 } 527 528 if (chain != NULL) { 529 *ret = chain; 530 return plt_ok; 531 } 532 533 /* We don't have stub symbols. Find corresponding .plt slot, 534 * and check whether it contains the corresponding PLT address 535 * (or 0 if the dynamic linker hasn't run yet). N.B. we don't 536 * want read this from ELF file, but from process image. That 537 * makes a difference if we are attaching to a running 538 * process. */ 539 540 GElf_Addr plt_entry_addr = arch_plt_sym_val(lte, ndx, rela); 541 GElf_Addr plt_slot_addr = rela->r_offset; 542 assert(plt_slot_addr >= lte->plt_addr 543 || plt_slot_addr < lte->plt_addr + lte->plt_size); 544 545 GElf_Addr plt_slot_value; 546 if (read_plt_slot_value(proc, plt_slot_addr, &plt_slot_value) < 0) 547 return plt_fail; 548 549 char *name = strdup(a_name); 550 struct library_symbol *libsym = malloc(sizeof(*libsym)); 551 if (name == NULL || libsym == NULL) { 552 error(0, errno, "allocation for .plt slot"); 553 fail: 554 free(name); 555 free(libsym); 556 return plt_fail; 557 } 558 559 /* XXX The double cast should be removed when 560 * target_address_t becomes integral type. */ 561 if (library_symbol_init(libsym, 562 (target_address_t)(uintptr_t)plt_entry_addr, 563 name, 1, LS_TOPLT_EXEC) < 0) 564 goto fail; 565 libsym->arch.plt_slot_addr = plt_slot_addr; 566 567 if (plt_slot_value == plt_entry_addr || plt_slot_value == 0) { 568 libsym->arch.type = PPC64PLT_UNRESOLVED; 569 libsym->arch.resolved_value = plt_entry_addr; 570 571 } else { 572 /* Unresolve the .plt slot. If the binary was 573 * prelinked, this makes the code invalid, because in 574 * case of prelinked binary, the dynamic linker 575 * doesn't update .plt[0] and .plt[1] with addresses 576 * of the resover. But we don't care, we will never 577 * need to enter the resolver. That just means that 578 * we have to un-un-resolve this back before we 579 * detach. */ 580 581 if (unresolve_plt_slot(proc, plt_slot_addr, plt_entry_addr) < 0) { 582 library_symbol_destroy(libsym); 583 goto fail; 584 } 585 mark_as_resolved(libsym, plt_slot_value); 586 } 587 588 *ret = libsym; 589 return plt_ok; 590} 591 592void 593arch_elf_destroy(struct ltelf *lte) 594{ 595 struct library_symbol *sym; 596 for (sym = lte->arch.stubs; sym != NULL; ) { 597 struct library_symbol *next = sym->next; 598 library_symbol_destroy(sym); 599 free(sym); 600 sym = next; 601 } 602} 603 604static void 605dl_plt_update_bp_on_hit(struct breakpoint *bp, struct Process *proc) 606{ 607 struct process_stopping_handler *self = proc->arch.handler; 608 assert(self != NULL); 609 610 struct library_symbol *libsym = self->breakpoint_being_enabled->libsym; 611 GElf_Addr value; 612 if (read_plt_slot_value(proc, libsym->arch.plt_slot_addr, &value) < 0) 613 return; 614 615 unresolve_plt_slot(proc, libsym->arch.plt_slot_addr, 616 libsym->arch.resolved_value); 617 618 /* cb_on_all_stopped looks if HANDLER is set to NULL as a way 619 * to check that this was run. It's an error if it 620 * wasn't. */ 621 breakpoint_turn_off(bp, proc); 622 proc->arch.handler = NULL; 623} 624 625static void 626cb_on_all_stopped(struct process_stopping_handler *self) 627{ 628 /* Put that in for dl_plt_update_bp_on_hit to see. */ 629 assert(self->task_enabling_breakpoint->arch.handler == NULL); 630 self->task_enabling_breakpoint->arch.handler = self; 631 632 linux_ptrace_disable_and_continue(self); 633} 634 635static enum callback_status 636cb_keep_stepping_p(struct process_stopping_handler *self) 637{ 638 struct Process *proc = self->task_enabling_breakpoint; 639 struct library_symbol *libsym = self->breakpoint_being_enabled->libsym; 640 GElf_Addr value; 641 if (read_plt_slot_value(proc, libsym->arch.plt_slot_addr, &value) < 0) 642 return CBS_FAIL; 643 644 /* In UNRESOLVED state, the RESOLVED_VALUE in fact contains 645 * the PLT entry value. */ 646 if (value == libsym->arch.resolved_value) 647 return CBS_CONT; 648 649 /* The .plt slot got resolved! We can migrate the breakpoint 650 * to RESOLVED and stop single-stepping. */ 651 if (unresolve_plt_slot(proc, libsym->arch.plt_slot_addr, 652 libsym->arch.resolved_value) < 0) 653 return CBS_FAIL; 654 655 /* Install breakpoint to the address where the change takes 656 * place. If we fail, then that just means that we'll have to 657 * singlestep the next time around as well. */ 658 struct Process *leader = proc->leader; 659 if (leader == NULL || leader->arch.dl_plt_update_bp != NULL) 660 goto done; 661 662 /* We need to install to the next instruction. ADDR points to 663 * a store instruction, so moving the breakpoint one 664 * instruction forward is safe. */ 665 target_address_t addr = get_instruction_pointer(proc) + 4; 666 leader->arch.dl_plt_update_bp = insert_breakpoint(proc, addr, NULL); 667 if (leader->arch.dl_plt_update_bp == NULL) 668 goto done; 669 670 /* Turn it off for now. We will turn it on again when we hit 671 * the PLT entry that needs this. */ 672 breakpoint_turn_off(leader->arch.dl_plt_update_bp, proc); 673 674 if (leader->arch.dl_plt_update_bp != NULL) { 675 static struct bp_callbacks dl_plt_update_cbs = { 676 .on_hit = dl_plt_update_bp_on_hit, 677 }; 678 leader->arch.dl_plt_update_bp->cbs = &dl_plt_update_cbs; 679 } 680 681done: 682 mark_as_resolved(libsym, value); 683 684 return CBS_STOP; 685} 686 687static void 688ppc_plt_bp_continue(struct breakpoint *bp, struct Process *proc) 689{ 690 switch (bp->libsym->arch.type) { 691 target_address_t rv; 692 struct Process *leader; 693 void (*on_all_stopped)(struct process_stopping_handler *); 694 enum callback_status (*keep_stepping_p) 695 (struct process_stopping_handler *); 696 697 case PPC_DEFAULT: 698 assert(proc->e_machine == EM_PPC); 699 assert(bp->libsym != NULL); 700 assert(bp->libsym->lib->arch.bss_plt_prelinked == 0); 701 /* fall-through */ 702 703 case PPC64PLT_UNRESOLVED: 704 on_all_stopped = NULL; 705 keep_stepping_p = NULL; 706 leader = proc->leader; 707 708 if (leader != NULL && leader->arch.dl_plt_update_bp != NULL 709 && breakpoint_turn_on(leader->arch.dl_plt_update_bp, 710 proc) >= 0) 711 on_all_stopped = cb_on_all_stopped; 712 else 713 keep_stepping_p = cb_keep_stepping_p; 714 715 if (process_install_stopping_handler 716 (proc, bp, on_all_stopped, keep_stepping_p, NULL) < 0) { 717 error(0, 0, "ppc_plt_bp_continue: couldn't install" 718 " event handler"); 719 continue_after_breakpoint(proc, bp); 720 } 721 return; 722 723 case PPC64PLT_RESOLVED: 724 /* XXX The double cast should be removed when 725 * target_address_t becomes integral type. */ 726 rv = (target_address_t) 727 (uintptr_t)bp->libsym->arch.resolved_value; 728 set_instruction_pointer(proc, rv); 729 continue_process(proc->pid); 730 return; 731 732 case PPC64PLT_STUB: 733 /* These should never hit here. */ 734 break; 735 } 736 737 assert(bp->libsym->arch.type != bp->libsym->arch.type); 738 abort(); 739} 740 741void 742arch_library_init(struct library *lib) 743{ 744} 745 746void 747arch_library_destroy(struct library *lib) 748{ 749} 750 751void 752arch_library_clone(struct library *retp, struct library *lib) 753{ 754} 755 756int 757arch_library_symbol_init(struct library_symbol *libsym) 758{ 759 /* We set type explicitly in the code above, where we have the 760 * necessary context. This is for calls from ltrace-elf.c and 761 * such. */ 762 libsym->arch.type = PPC_DEFAULT; 763 return 0; 764} 765 766void 767arch_library_symbol_destroy(struct library_symbol *libsym) 768{ 769} 770 771int 772arch_library_symbol_clone(struct library_symbol *retp, 773 struct library_symbol *libsym) 774{ 775 retp->arch = libsym->arch; 776 return 0; 777} 778 779/* For some symbol types, we need to set up custom callbacks. XXX we 780 * don't need PROC here, we can store the data in BP if it is of 781 * interest to us. */ 782int 783arch_breakpoint_init(struct Process *proc, struct breakpoint *bp) 784{ 785 /* Artificial and entry-point breakpoints are plain. */ 786 if (bp->libsym == NULL || bp->libsym->plt_type != LS_TOPLT_EXEC) 787 return 0; 788 789 /* On PPC, secure PLT and prelinked BSS PLT are plain. */ 790 if (proc->e_machine == EM_PPC 791 && bp->libsym->lib->arch.bss_plt_prelinked != 0) 792 return 0; 793 794 /* On PPC64, stub PLT breakpoints are plain. */ 795 if (proc->e_machine == EM_PPC64 796 && bp->libsym->arch.type == PPC64PLT_STUB) 797 return 0; 798 799 static struct bp_callbacks cbs = { 800 .on_continue = ppc_plt_bp_continue, 801 }; 802 breakpoint_set_callbacks(bp, &cbs); 803 return 0; 804} 805 806void 807arch_breakpoint_destroy(struct breakpoint *bp) 808{ 809} 810 811int 812arch_breakpoint_clone(struct breakpoint *retp, struct breakpoint *sbp) 813{ 814 retp->arch = sbp->arch; 815 return 0; 816} 817 818int 819arch_process_init(struct Process *proc) 820{ 821 proc->arch.dl_plt_update_bp = NULL; 822 proc->arch.handler = NULL; 823 return 0; 824} 825 826void 827arch_process_destroy(struct Process *proc) 828{ 829} 830 831int 832arch_process_clone(struct Process *retp, struct Process *proc) 833{ 834 retp->arch = proc->arch; 835 return 0; 836} 837 838int 839arch_process_exec(struct Process *proc) 840{ 841 return arch_process_init(proc); 842} 843