1 /* SPDX-License-Identifier: GPL-2.0-only */ 2 /* 3 * recordmcount.h 4 * 5 * This code was taken out of recordmcount.c written by 6 * Copyright 2009 John F. Reiser <jreiser@BitWagon.com>. All rights reserved. 7 * 8 * The original code had the same algorithms for both 32bit 9 * and 64bit ELF files, but the code was duplicated to support 10 * the difference in structures that were used. This 11 * file creates a macro of everything that is different between 12 * the 64 and 32 bit code, such that by including this header 13 * twice we can create both sets of functions by including this 14 * header once with RECORD_MCOUNT_64 undefined, and again with 15 * it defined. 16 * 17 * This conversion to macros was done by: 18 * Copyright 2010 Steven Rostedt <srostedt@redhat.com>, Red Hat Inc. 19 */ 20 #undef append_func 21 #undef is_fake_mcount 22 #undef fn_is_fake_mcount 23 #undef MIPS_is_fake_mcount 24 #undef mcount_adjust 25 #undef sift_rel_mcount 26 #undef nop_mcount 27 #undef find_secsym_ndx 28 #undef __has_rel_mcount 29 #undef has_rel_mcount 30 #undef tot_relsize 31 #undef get_mcountsym 32 #undef get_sym_str_and_relp 33 #undef do_func 34 #undef Elf_Addr 35 #undef Elf_Ehdr 36 #undef Elf_Shdr 37 #undef Elf_Rel 38 #undef Elf_Rela 39 #undef Elf_Sym 40 #undef ELF_R_SYM 41 #undef Elf_r_sym 42 #undef ELF_R_INFO 43 #undef Elf_r_info 44 #undef ELF_ST_BIND 45 #undef ELF_ST_TYPE 46 #undef fn_ELF_R_SYM 47 #undef fn_ELF_R_INFO 48 #undef uint_t 49 #undef _w 50 #undef _align 51 #undef _size 52 53 #ifdef RECORD_MCOUNT_64 54 # define append_func append64 55 # define sift_rel_mcount sift64_rel_mcount 56 # define nop_mcount nop_mcount_64 57 # define find_secsym_ndx find64_secsym_ndx 58 # define __has_rel_mcount __has64_rel_mcount 59 # define has_rel_mcount has64_rel_mcount 60 # define tot_relsize tot64_relsize 61 # define get_sym_str_and_relp get_sym_str_and_relp_64 62 # define do_func do64 63 # define get_mcountsym get_mcountsym_64 64 # define is_fake_mcount is_fake_mcount64 65 # define fn_is_fake_mcount fn_is_fake_mcount64 66 # define MIPS_is_fake_mcount MIPS64_is_fake_mcount 67 # define mcount_adjust mcount_adjust_64 68 # define Elf_Addr Elf64_Addr 69 # define Elf_Ehdr Elf64_Ehdr 70 # define Elf_Shdr Elf64_Shdr 71 # define Elf_Rel Elf64_Rel 72 # define Elf_Rela Elf64_Rela 73 # define Elf_Sym Elf64_Sym 74 # define ELF_R_SYM ELF64_R_SYM 75 # define Elf_r_sym Elf64_r_sym 76 # define ELF_R_INFO ELF64_R_INFO 77 # define Elf_r_info Elf64_r_info 78 # define ELF_ST_BIND ELF64_ST_BIND 79 # define ELF_ST_TYPE ELF64_ST_TYPE 80 # define fn_ELF_R_SYM fn_ELF64_R_SYM 81 # define fn_ELF_R_INFO fn_ELF64_R_INFO 82 # define uint_t uint64_t 83 # define _w w8 84 # define _align 7u 85 # define _size 8 86 #else 87 # define append_func append32 88 # define sift_rel_mcount sift32_rel_mcount 89 # define nop_mcount nop_mcount_32 90 # define find_secsym_ndx find32_secsym_ndx 91 # define __has_rel_mcount __has32_rel_mcount 92 # define has_rel_mcount has32_rel_mcount 93 # define tot_relsize tot32_relsize 94 # define get_sym_str_and_relp get_sym_str_and_relp_32 95 # define do_func do32 96 # define get_mcountsym get_mcountsym_32 97 # define is_fake_mcount is_fake_mcount32 98 # define fn_is_fake_mcount fn_is_fake_mcount32 99 # define MIPS_is_fake_mcount MIPS32_is_fake_mcount 100 # define mcount_adjust mcount_adjust_32 101 # define Elf_Addr Elf32_Addr 102 # define Elf_Ehdr Elf32_Ehdr 103 # define Elf_Shdr Elf32_Shdr 104 # define Elf_Rel Elf32_Rel 105 # define Elf_Rela Elf32_Rela 106 # define Elf_Sym Elf32_Sym 107 # define ELF_R_SYM ELF32_R_SYM 108 # define Elf_r_sym Elf32_r_sym 109 # define ELF_R_INFO ELF32_R_INFO 110 # define Elf_r_info Elf32_r_info 111 # define ELF_ST_BIND ELF32_ST_BIND 112 # define ELF_ST_TYPE ELF32_ST_TYPE 113 # define fn_ELF_R_SYM fn_ELF32_R_SYM 114 # define fn_ELF_R_INFO fn_ELF32_R_INFO 115 # define uint_t uint32_t 116 # define _w w 117 # define _align 3u 118 # define _size 4 119 #endif 120 121 /* Functions and pointers that do_file() may override for specific e_machine. */ 122 static int fn_is_fake_mcount(Elf_Rel const *rp) 123 { 124 return 0; 125 } 126 static int (*is_fake_mcount)(Elf_Rel const *rp) = fn_is_fake_mcount; 127 128 static uint_t fn_ELF_R_SYM(Elf_Rel const *rp) 129 { 130 return ELF_R_SYM(_w(rp->r_info)); 131 } 132 static uint_t (*Elf_r_sym)(Elf_Rel const *rp) = fn_ELF_R_SYM; 133 134 static void fn_ELF_R_INFO(Elf_Rel *const rp, unsigned sym, unsigned type) 135 { 136 rp->r_info = _w(ELF_R_INFO(sym, type)); 137 } 138 static void (*Elf_r_info)(Elf_Rel *const rp, unsigned sym, unsigned type) = fn_ELF_R_INFO; 139 140 static int mcount_adjust = 0; 141 142 /* 143 * MIPS mcount long call has 2 _mcount symbols, only the position of the 1st 144 * _mcount symbol is needed for dynamic function tracer, with it, to disable 145 * tracing(ftrace_make_nop), the instruction in the position is replaced with 146 * the "b label" instruction, to enable tracing(ftrace_make_call), replace the 147 * instruction back. So, here, we set the 2nd one as fake and filter it. 148 * 149 * c: 3c030000 lui v1,0x0 <--> b label 150 * c: R_MIPS_HI16 _mcount 151 * c: R_MIPS_NONE *ABS* 152 * c: R_MIPS_NONE *ABS* 153 * 10: 64630000 daddiu v1,v1,0 154 * 10: R_MIPS_LO16 _mcount 155 * 10: R_MIPS_NONE *ABS* 156 * 10: R_MIPS_NONE *ABS* 157 * 14: 03e0082d move at,ra 158 * 18: 0060f809 jalr v1 159 * label: 160 */ 161 #define MIPS_FAKEMCOUNT_OFFSET 4 162 163 static int MIPS_is_fake_mcount(Elf_Rel const *rp) 164 { 165 static Elf_Addr old_r_offset = ~(Elf_Addr)0; 166 Elf_Addr current_r_offset = _w(rp->r_offset); 167 int is_fake; 168 169 is_fake = (old_r_offset != ~(Elf_Addr)0) && 170 (current_r_offset - old_r_offset == MIPS_FAKEMCOUNT_OFFSET); 171 old_r_offset = current_r_offset; 172 173 return is_fake; 174 } 175 176 /* Append the new shstrtab, Elf_Shdr[], __mcount_loc and its relocations. */ 177 static void append_func(Elf_Ehdr *const ehdr, 178 Elf_Shdr *const shstr, 179 uint_t const *const mloc0, 180 uint_t const *const mlocp, 181 Elf_Rel const *const mrel0, 182 Elf_Rel const *const mrelp, 183 unsigned int const rel_entsize, 184 unsigned int const symsec_sh_link) 185 { 186 /* Begin constructing output file */ 187 Elf_Shdr mcsec; 188 char const *mc_name = (sizeof(Elf_Rela) == rel_entsize) 189 ? ".rela__mcount_loc" 190 : ".rel__mcount_loc"; 191 unsigned const old_shnum = w2(ehdr->e_shnum); 192 uint_t const old_shoff = _w(ehdr->e_shoff); 193 uint_t const old_shstr_sh_size = _w(shstr->sh_size); 194 uint_t const old_shstr_sh_offset = _w(shstr->sh_offset); 195 uint_t t = 1 + strlen(mc_name) + _w(shstr->sh_size); 196 uint_t new_e_shoff; 197 198 shstr->sh_size = _w(t); 199 shstr->sh_offset = _w(sb.st_size); 200 t += sb.st_size; 201 t += (_align & -t); /* word-byte align */ 202 new_e_shoff = t; 203 204 /* body for new shstrtab */ 205 ulseek(fd_map, sb.st_size, SEEK_SET); 206 uwrite(fd_map, old_shstr_sh_offset + (void *)ehdr, old_shstr_sh_size); 207 uwrite(fd_map, mc_name, 1 + strlen(mc_name)); 208 209 /* old(modified) Elf_Shdr table, word-byte aligned */ 210 ulseek(fd_map, t, SEEK_SET); 211 t += sizeof(Elf_Shdr) * old_shnum; 212 uwrite(fd_map, old_shoff + (void *)ehdr, 213 sizeof(Elf_Shdr) * old_shnum); 214 215 /* new sections __mcount_loc and .rel__mcount_loc */ 216 t += 2*sizeof(mcsec); 217 mcsec.sh_name = w((sizeof(Elf_Rela) == rel_entsize) + strlen(".rel") 218 + old_shstr_sh_size); 219 mcsec.sh_type = w(SHT_PROGBITS); 220 mcsec.sh_flags = _w(SHF_ALLOC); 221 mcsec.sh_addr = 0; 222 mcsec.sh_offset = _w(t); 223 mcsec.sh_size = _w((void *)mlocp - (void *)mloc0); 224 mcsec.sh_link = 0; 225 mcsec.sh_info = 0; 226 mcsec.sh_addralign = _w(_size); 227 mcsec.sh_entsize = _w(_size); 228 uwrite(fd_map, &mcsec, sizeof(mcsec)); 229 230 mcsec.sh_name = w(old_shstr_sh_size); 231 mcsec.sh_type = (sizeof(Elf_Rela) == rel_entsize) 232 ? w(SHT_RELA) 233 : w(SHT_REL); 234 mcsec.sh_flags = 0; 235 mcsec.sh_addr = 0; 236 mcsec.sh_offset = _w((void *)mlocp - (void *)mloc0 + t); 237 mcsec.sh_size = _w((void *)mrelp - (void *)mrel0); 238 mcsec.sh_link = w(symsec_sh_link); 239 mcsec.sh_info = w(old_shnum); 240 mcsec.sh_addralign = _w(_size); 241 mcsec.sh_entsize = _w(rel_entsize); 242 uwrite(fd_map, &mcsec, sizeof(mcsec)); 243 244 uwrite(fd_map, mloc0, (void *)mlocp - (void *)mloc0); 245 uwrite(fd_map, mrel0, (void *)mrelp - (void *)mrel0); 246 247 ehdr->e_shoff = _w(new_e_shoff); 248 ehdr->e_shnum = w2(2 + w2(ehdr->e_shnum)); /* {.rel,}__mcount_loc */ 249 ulseek(fd_map, 0, SEEK_SET); 250 uwrite(fd_map, ehdr, sizeof(*ehdr)); 251 } 252 253 static unsigned get_mcountsym(Elf_Sym const *const sym0, 254 Elf_Rel const *relp, 255 char const *const str0) 256 { 257 unsigned mcountsym = 0; 258 259 Elf_Sym const *const symp = 260 &sym0[Elf_r_sym(relp)]; 261 char const *symname = &str0[w(symp->st_name)]; 262 char const *mcount = gpfx == '_' ? "_mcount" : "mcount"; 263 char const *fentry = "__fentry__"; 264 265 if (symname[0] == '.') 266 ++symname; /* ppc64 hack */ 267 if (strcmp(mcount, symname) == 0 || 268 (altmcount && strcmp(altmcount, symname) == 0) || 269 (strcmp(fentry, symname) == 0)) 270 mcountsym = Elf_r_sym(relp); 271 272 return mcountsym; 273 } 274 275 static void get_sym_str_and_relp(Elf_Shdr const *const relhdr, 276 Elf_Ehdr const *const ehdr, 277 Elf_Sym const **sym0, 278 char const **str0, 279 Elf_Rel const **relp) 280 { 281 Elf_Shdr *const shdr0 = (Elf_Shdr *)(_w(ehdr->e_shoff) 282 + (void *)ehdr); 283 unsigned const symsec_sh_link = w(relhdr->sh_link); 284 Elf_Shdr const *const symsec = &shdr0[symsec_sh_link]; 285 Elf_Shdr const *const strsec = &shdr0[w(symsec->sh_link)]; 286 Elf_Rel const *const rel0 = (Elf_Rel const *)(_w(relhdr->sh_offset) 287 + (void *)ehdr); 288 289 *sym0 = (Elf_Sym const *)(_w(symsec->sh_offset) 290 + (void *)ehdr); 291 292 *str0 = (char const *)(_w(strsec->sh_offset) 293 + (void *)ehdr); 294 295 *relp = rel0; 296 } 297 298 /* 299 * Look at the relocations in order to find the calls to mcount. 300 * Accumulate the section offsets that are found, and their relocation info, 301 * onto the end of the existing arrays. 302 */ 303 static uint_t *sift_rel_mcount(uint_t *mlocp, 304 unsigned const offbase, 305 Elf_Rel **const mrelpp, 306 Elf_Shdr const *const relhdr, 307 Elf_Ehdr const *const ehdr, 308 unsigned const recsym, 309 uint_t const recval, 310 unsigned const reltype) 311 { 312 uint_t *const mloc0 = mlocp; 313 Elf_Rel *mrelp = *mrelpp; 314 Elf_Sym const *sym0; 315 char const *str0; 316 Elf_Rel const *relp; 317 unsigned rel_entsize = _w(relhdr->sh_entsize); 318 unsigned const nrel = _w(relhdr->sh_size) / rel_entsize; 319 unsigned mcountsym = 0; 320 unsigned t; 321 322 get_sym_str_and_relp(relhdr, ehdr, &sym0, &str0, &relp); 323 324 for (t = nrel; t; --t) { 325 if (!mcountsym) 326 mcountsym = get_mcountsym(sym0, relp, str0); 327 328 if (mcountsym && mcountsym == Elf_r_sym(relp) && 329 !is_fake_mcount(relp)) { 330 uint_t const addend = 331 _w(_w(relp->r_offset) - recval + mcount_adjust); 332 mrelp->r_offset = _w(offbase 333 + ((void *)mlocp - (void *)mloc0)); 334 Elf_r_info(mrelp, recsym, reltype); 335 if (rel_entsize == sizeof(Elf_Rela)) { 336 ((Elf_Rela *)mrelp)->r_addend = addend; 337 *mlocp++ = 0; 338 } else 339 *mlocp++ = addend; 340 341 mrelp = (Elf_Rel *)(rel_entsize + (void *)mrelp); 342 } 343 relp = (Elf_Rel const *)(rel_entsize + (void *)relp); 344 } 345 *mrelpp = mrelp; 346 return mlocp; 347 } 348 349 /* 350 * Read the relocation table again, but this time its called on sections 351 * that are not going to be traced. The mcount calls here will be converted 352 * into nops. 353 */ 354 static void nop_mcount(Elf_Shdr const *const relhdr, 355 Elf_Ehdr const *const ehdr, 356 const char *const txtname) 357 { 358 Elf_Shdr *const shdr0 = (Elf_Shdr *)(_w(ehdr->e_shoff) 359 + (void *)ehdr); 360 Elf_Sym const *sym0; 361 char const *str0; 362 Elf_Rel const *relp; 363 Elf_Shdr const *const shdr = &shdr0[w(relhdr->sh_info)]; 364 unsigned rel_entsize = _w(relhdr->sh_entsize); 365 unsigned const nrel = _w(relhdr->sh_size) / rel_entsize; 366 unsigned mcountsym = 0; 367 unsigned t; 368 int once = 0; 369 370 get_sym_str_and_relp(relhdr, ehdr, &sym0, &str0, &relp); 371 372 for (t = nrel; t; --t) { 373 int ret = -1; 374 375 if (!mcountsym) 376 mcountsym = get_mcountsym(sym0, relp, str0); 377 378 if (mcountsym == Elf_r_sym(relp) && !is_fake_mcount(relp)) { 379 if (make_nop) 380 ret = make_nop((void *)ehdr, _w(shdr->sh_offset) + _w(relp->r_offset)); 381 if (warn_on_notrace_sect && !once) { 382 printf("Section %s has mcount callers being ignored\n", 383 txtname); 384 once = 1; 385 /* just warn? */ 386 if (!make_nop) 387 return; 388 } 389 } 390 391 /* 392 * If we successfully removed the mcount, mark the relocation 393 * as a nop (don't do anything with it). 394 */ 395 if (!ret) { 396 Elf_Rel rel; 397 rel = *(Elf_Rel *)relp; 398 Elf_r_info(&rel, Elf_r_sym(relp), rel_type_nop); 399 ulseek(fd_map, (void *)relp - (void *)ehdr, SEEK_SET); 400 uwrite(fd_map, &rel, sizeof(rel)); 401 } 402 relp = (Elf_Rel const *)(rel_entsize + (void *)relp); 403 } 404 } 405 406 407 /* 408 * Find a symbol in the given section, to be used as the base for relocating 409 * the table of offsets of calls to mcount. A local or global symbol suffices, 410 * but avoid a Weak symbol because it may be overridden; the change in value 411 * would invalidate the relocations of the offsets of the calls to mcount. 412 * Often the found symbol will be the unnamed local symbol generated by 413 * GNU 'as' for the start of each section. For example: 414 * Num: Value Size Type Bind Vis Ndx Name 415 * 2: 00000000 0 SECTION LOCAL DEFAULT 1 416 */ 417 static unsigned find_secsym_ndx(unsigned const txtndx, 418 char const *const txtname, 419 uint_t *const recvalp, 420 Elf_Shdr const *const symhdr, 421 Elf_Ehdr const *const ehdr) 422 { 423 Elf_Sym const *const sym0 = (Elf_Sym const *)(_w(symhdr->sh_offset) 424 + (void *)ehdr); 425 unsigned const nsym = _w(symhdr->sh_size) / _w(symhdr->sh_entsize); 426 Elf_Sym const *symp; 427 unsigned t; 428 429 for (symp = sym0, t = nsym; t; --t, ++symp) { 430 unsigned int const st_bind = ELF_ST_BIND(symp->st_info); 431 432 if (txtndx == w2(symp->st_shndx) 433 /* avoid STB_WEAK */ 434 && (STB_LOCAL == st_bind || STB_GLOBAL == st_bind)) { 435 /* function symbols on ARM have quirks, avoid them */ 436 if (w2(ehdr->e_machine) == EM_ARM 437 && ELF_ST_TYPE(symp->st_info) == STT_FUNC) 438 continue; 439 440 *recvalp = _w(symp->st_value); 441 return symp - sym0; 442 } 443 } 444 fprintf(stderr, "Cannot find symbol for section %u: %s.\n", 445 txtndx, txtname); 446 fail_file(); 447 } 448 449 450 /* Evade ISO C restriction: no declaration after statement in has_rel_mcount. */ 451 static char const * 452 __has_rel_mcount(Elf_Shdr const *const relhdr, /* is SHT_REL or SHT_RELA */ 453 Elf_Shdr const *const shdr0, 454 char const *const shstrtab, 455 char const *const fname) 456 { 457 /* .sh_info depends on .sh_type == SHT_REL[,A] */ 458 Elf_Shdr const *const txthdr = &shdr0[w(relhdr->sh_info)]; 459 char const *const txtname = &shstrtab[w(txthdr->sh_name)]; 460 461 if (strcmp("__mcount_loc", txtname) == 0) { 462 fprintf(stderr, "warning: __mcount_loc already exists: %s\n", 463 fname); 464 succeed_file(); 465 } 466 if (w(txthdr->sh_type) != SHT_PROGBITS || 467 !(_w(txthdr->sh_flags) & SHF_EXECINSTR)) 468 return NULL; 469 return txtname; 470 } 471 472 static char const *has_rel_mcount(Elf_Shdr const *const relhdr, 473 Elf_Shdr const *const shdr0, 474 char const *const shstrtab, 475 char const *const fname) 476 { 477 if (w(relhdr->sh_type) != SHT_REL && w(relhdr->sh_type) != SHT_RELA) 478 return NULL; 479 return __has_rel_mcount(relhdr, shdr0, shstrtab, fname); 480 } 481 482 483 static unsigned tot_relsize(Elf_Shdr const *const shdr0, 484 unsigned nhdr, 485 const char *const shstrtab, 486 const char *const fname) 487 { 488 unsigned totrelsz = 0; 489 Elf_Shdr const *shdrp = shdr0; 490 char const *txtname; 491 492 for (; nhdr; --nhdr, ++shdrp) { 493 txtname = has_rel_mcount(shdrp, shdr0, shstrtab, fname); 494 if (txtname && is_mcounted_section_name(txtname)) 495 totrelsz += _w(shdrp->sh_size); 496 } 497 return totrelsz; 498 } 499 500 501 /* Overall supervision for Elf32 ET_REL file. */ 502 static void 503 do_func(Elf_Ehdr *const ehdr, char const *const fname, unsigned const reltype) 504 { 505 Elf_Shdr *const shdr0 = (Elf_Shdr *)(_w(ehdr->e_shoff) 506 + (void *)ehdr); 507 unsigned const nhdr = w2(ehdr->e_shnum); 508 Elf_Shdr *const shstr = &shdr0[w2(ehdr->e_shstrndx)]; 509 char const *const shstrtab = (char const *)(_w(shstr->sh_offset) 510 + (void *)ehdr); 511 512 Elf_Shdr const *relhdr; 513 unsigned k; 514 515 /* Upper bound on space: assume all relevant relocs are for mcount. */ 516 unsigned const totrelsz = tot_relsize(shdr0, nhdr, shstrtab, fname); 517 Elf_Rel *const mrel0 = umalloc(totrelsz); 518 Elf_Rel * mrelp = mrel0; 519 520 /* 2*sizeof(address) <= sizeof(Elf_Rel) */ 521 uint_t *const mloc0 = umalloc(totrelsz>>1); 522 uint_t * mlocp = mloc0; 523 524 unsigned rel_entsize = 0; 525 unsigned symsec_sh_link = 0; 526 527 for (relhdr = shdr0, k = nhdr; k; --k, ++relhdr) { 528 char const *const txtname = has_rel_mcount(relhdr, shdr0, 529 shstrtab, fname); 530 if (txtname && is_mcounted_section_name(txtname)) { 531 uint_t recval = 0; 532 unsigned const recsym = find_secsym_ndx( 533 w(relhdr->sh_info), txtname, &recval, 534 &shdr0[symsec_sh_link = w(relhdr->sh_link)], 535 ehdr); 536 537 rel_entsize = _w(relhdr->sh_entsize); 538 mlocp = sift_rel_mcount(mlocp, 539 (void *)mlocp - (void *)mloc0, &mrelp, 540 relhdr, ehdr, recsym, recval, reltype); 541 } else if (txtname && (warn_on_notrace_sect || make_nop)) { 542 /* 543 * This section is ignored by ftrace, but still 544 * has mcount calls. Convert them to nops now. 545 */ 546 nop_mcount(relhdr, ehdr, txtname); 547 } 548 } 549 if (mloc0 != mlocp) { 550 append_func(ehdr, shstr, mloc0, mlocp, mrel0, mrelp, 551 rel_entsize, symsec_sh_link); 552 } 553 free(mrel0); 554 free(mloc0); 555 } 556