1 /* 2 * recordmcount.h 3 * 4 * This code was taken out of recordmcount.c written by 5 * Copyright 2009 John F. Reiser <jreiser@BitWagon.com>. All rights reserved. 6 * 7 * The original code had the same algorithms for both 32bit 8 * and 64bit ELF files, but the code was duplicated to support 9 * the difference in structures that were used. This 10 * file creates a macro of everything that is different between 11 * the 64 and 32 bit code, such that by including this header 12 * twice we can create both sets of functions by including this 13 * header once with RECORD_MCOUNT_64 undefined, and again with 14 * it defined. 15 * 16 * This conversion to macros was done by: 17 * Copyright 2010 Steven Rostedt <srostedt@redhat.com>, Red Hat Inc. 18 * 19 * Licensed under the GNU General Public License, version 2 (GPLv2). 20 */ 21 #undef append_func 22 #undef is_fake_mcount 23 #undef fn_is_fake_mcount 24 #undef MIPS_is_fake_mcount 25 #undef mcount_adjust 26 #undef sift_rel_mcount 27 #undef nop_mcount 28 #undef find_secsym_ndx 29 #undef __has_rel_mcount 30 #undef has_rel_mcount 31 #undef tot_relsize 32 #undef get_mcountsym 33 #undef get_sym_str_and_relp 34 #undef do_func 35 #undef Elf_Addr 36 #undef Elf_Ehdr 37 #undef Elf_Shdr 38 #undef Elf_Rel 39 #undef Elf_Rela 40 #undef Elf_Sym 41 #undef ELF_R_SYM 42 #undef Elf_r_sym 43 #undef ELF_R_INFO 44 #undef Elf_r_info 45 #undef ELF_ST_BIND 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 fn_ELF_R_SYM fn_ELF64_R_SYM 80 # define fn_ELF_R_INFO fn_ELF64_R_INFO 81 # define uint_t uint64_t 82 # define _w w8 83 # define _align 7u 84 # define _size 8 85 #else 86 # define append_func append32 87 # define sift_rel_mcount sift32_rel_mcount 88 # define nop_mcount nop_mcount_32 89 # define find_secsym_ndx find32_secsym_ndx 90 # define __has_rel_mcount __has32_rel_mcount 91 # define has_rel_mcount has32_rel_mcount 92 # define tot_relsize tot32_relsize 93 # define get_sym_str_and_relp get_sym_str_and_relp_32 94 # define do_func do32 95 # define get_mcountsym get_mcountsym_32 96 # define is_fake_mcount is_fake_mcount32 97 # define fn_is_fake_mcount fn_is_fake_mcount32 98 # define MIPS_is_fake_mcount MIPS32_is_fake_mcount 99 # define mcount_adjust mcount_adjust_32 100 # define Elf_Addr Elf32_Addr 101 # define Elf_Ehdr Elf32_Ehdr 102 # define Elf_Shdr Elf32_Shdr 103 # define Elf_Rel Elf32_Rel 104 # define Elf_Rela Elf32_Rela 105 # define Elf_Sym Elf32_Sym 106 # define ELF_R_SYM ELF32_R_SYM 107 # define Elf_r_sym Elf32_r_sym 108 # define ELF_R_INFO ELF32_R_INFO 109 # define Elf_r_info Elf32_r_info 110 # define ELF_ST_BIND ELF32_ST_BIND 111 # define fn_ELF_R_SYM fn_ELF32_R_SYM 112 # define fn_ELF_R_INFO fn_ELF32_R_INFO 113 # define uint_t uint32_t 114 # define _w w 115 # define _align 3u 116 # define _size 4 117 #endif 118 119 /* Functions and pointers that do_file() may override for specific e_machine. */ 120 static int fn_is_fake_mcount(Elf_Rel const *rp) 121 { 122 return 0; 123 } 124 static int (*is_fake_mcount)(Elf_Rel const *rp) = fn_is_fake_mcount; 125 126 static uint_t fn_ELF_R_SYM(Elf_Rel const *rp) 127 { 128 return ELF_R_SYM(_w(rp->r_info)); 129 } 130 static uint_t (*Elf_r_sym)(Elf_Rel const *rp) = fn_ELF_R_SYM; 131 132 static void fn_ELF_R_INFO(Elf_Rel *const rp, unsigned sym, unsigned type) 133 { 134 rp->r_info = _w(ELF_R_INFO(sym, type)); 135 } 136 static void (*Elf_r_info)(Elf_Rel *const rp, unsigned sym, unsigned type) = fn_ELF_R_INFO; 137 138 static int mcount_adjust = 0; 139 140 /* 141 * MIPS mcount long call has 2 _mcount symbols, only the position of the 1st 142 * _mcount symbol is needed for dynamic function tracer, with it, to disable 143 * tracing(ftrace_make_nop), the instruction in the position is replaced with 144 * the "b label" instruction, to enable tracing(ftrace_make_call), replace the 145 * instruction back. So, here, we set the 2nd one as fake and filter it. 146 * 147 * c: 3c030000 lui v1,0x0 <--> b label 148 * c: R_MIPS_HI16 _mcount 149 * c: R_MIPS_NONE *ABS* 150 * c: R_MIPS_NONE *ABS* 151 * 10: 64630000 daddiu v1,v1,0 152 * 10: R_MIPS_LO16 _mcount 153 * 10: R_MIPS_NONE *ABS* 154 * 10: R_MIPS_NONE *ABS* 155 * 14: 03e0082d move at,ra 156 * 18: 0060f809 jalr v1 157 * label: 158 */ 159 #define MIPS_FAKEMCOUNT_OFFSET 4 160 161 static int MIPS_is_fake_mcount(Elf_Rel const *rp) 162 { 163 static Elf_Addr old_r_offset; 164 Elf_Addr current_r_offset = _w(rp->r_offset); 165 int is_fake; 166 167 is_fake = old_r_offset && 168 (current_r_offset - old_r_offset == MIPS_FAKEMCOUNT_OFFSET); 169 old_r_offset = current_r_offset; 170 171 return is_fake; 172 } 173 174 /* Append the new shstrtab, Elf_Shdr[], __mcount_loc and its relocations. */ 175 static void append_func(Elf_Ehdr *const ehdr, 176 Elf_Shdr *const shstr, 177 uint_t const *const mloc0, 178 uint_t const *const mlocp, 179 Elf_Rel const *const mrel0, 180 Elf_Rel const *const mrelp, 181 unsigned int const rel_entsize, 182 unsigned int const symsec_sh_link) 183 { 184 /* Begin constructing output file */ 185 Elf_Shdr mcsec; 186 char const *mc_name = (sizeof(Elf_Rela) == rel_entsize) 187 ? ".rela__mcount_loc" 188 : ".rel__mcount_loc"; 189 unsigned const old_shnum = w2(ehdr->e_shnum); 190 uint_t const old_shoff = _w(ehdr->e_shoff); 191 uint_t const old_shstr_sh_size = _w(shstr->sh_size); 192 uint_t const old_shstr_sh_offset = _w(shstr->sh_offset); 193 uint_t t = 1 + strlen(mc_name) + _w(shstr->sh_size); 194 uint_t new_e_shoff; 195 196 shstr->sh_size = _w(t); 197 shstr->sh_offset = _w(sb.st_size); 198 t += sb.st_size; 199 t += (_align & -t); /* word-byte align */ 200 new_e_shoff = t; 201 202 /* body for new shstrtab */ 203 ulseek(fd_map, sb.st_size, SEEK_SET); 204 uwrite(fd_map, old_shstr_sh_offset + (void *)ehdr, old_shstr_sh_size); 205 uwrite(fd_map, mc_name, 1 + strlen(mc_name)); 206 207 /* old(modified) Elf_Shdr table, word-byte aligned */ 208 ulseek(fd_map, t, SEEK_SET); 209 t += sizeof(Elf_Shdr) * old_shnum; 210 uwrite(fd_map, old_shoff + (void *)ehdr, 211 sizeof(Elf_Shdr) * old_shnum); 212 213 /* new sections __mcount_loc and .rel__mcount_loc */ 214 t += 2*sizeof(mcsec); 215 mcsec.sh_name = w((sizeof(Elf_Rela) == rel_entsize) + strlen(".rel") 216 + old_shstr_sh_size); 217 mcsec.sh_type = w(SHT_PROGBITS); 218 mcsec.sh_flags = _w(SHF_ALLOC); 219 mcsec.sh_addr = 0; 220 mcsec.sh_offset = _w(t); 221 mcsec.sh_size = _w((void *)mlocp - (void *)mloc0); 222 mcsec.sh_link = 0; 223 mcsec.sh_info = 0; 224 mcsec.sh_addralign = _w(_size); 225 mcsec.sh_entsize = _w(_size); 226 uwrite(fd_map, &mcsec, sizeof(mcsec)); 227 228 mcsec.sh_name = w(old_shstr_sh_size); 229 mcsec.sh_type = (sizeof(Elf_Rela) == rel_entsize) 230 ? w(SHT_RELA) 231 : w(SHT_REL); 232 mcsec.sh_flags = 0; 233 mcsec.sh_addr = 0; 234 mcsec.sh_offset = _w((void *)mlocp - (void *)mloc0 + t); 235 mcsec.sh_size = _w((void *)mrelp - (void *)mrel0); 236 mcsec.sh_link = w(symsec_sh_link); 237 mcsec.sh_info = w(old_shnum); 238 mcsec.sh_addralign = _w(_size); 239 mcsec.sh_entsize = _w(rel_entsize); 240 uwrite(fd_map, &mcsec, sizeof(mcsec)); 241 242 uwrite(fd_map, mloc0, (void *)mlocp - (void *)mloc0); 243 uwrite(fd_map, mrel0, (void *)mrelp - (void *)mrel0); 244 245 ehdr->e_shoff = _w(new_e_shoff); 246 ehdr->e_shnum = w2(2 + w2(ehdr->e_shnum)); /* {.rel,}__mcount_loc */ 247 ulseek(fd_map, 0, SEEK_SET); 248 uwrite(fd_map, ehdr, sizeof(*ehdr)); 249 } 250 251 static unsigned get_mcountsym(Elf_Sym const *const sym0, 252 Elf_Rel const *relp, 253 char const *const str0) 254 { 255 unsigned mcountsym = 0; 256 257 Elf_Sym const *const symp = 258 &sym0[Elf_r_sym(relp)]; 259 char const *symname = &str0[w(symp->st_name)]; 260 char const *mcount = gpfx == '_' ? "_mcount" : "mcount"; 261 262 if (symname[0] == '.') 263 ++symname; /* ppc64 hack */ 264 if (strcmp(mcount, symname) == 0 || 265 (altmcount && strcmp(altmcount, symname) == 0)) 266 mcountsym = Elf_r_sym(relp); 267 268 return mcountsym; 269 } 270 271 static void get_sym_str_and_relp(Elf_Shdr const *const relhdr, 272 Elf_Ehdr const *const ehdr, 273 Elf_Sym const **sym0, 274 char const **str0, 275 Elf_Rel const **relp) 276 { 277 Elf_Shdr *const shdr0 = (Elf_Shdr *)(_w(ehdr->e_shoff) 278 + (void *)ehdr); 279 unsigned const symsec_sh_link = w(relhdr->sh_link); 280 Elf_Shdr const *const symsec = &shdr0[symsec_sh_link]; 281 Elf_Shdr const *const strsec = &shdr0[w(symsec->sh_link)]; 282 Elf_Rel const *const rel0 = (Elf_Rel const *)(_w(relhdr->sh_offset) 283 + (void *)ehdr); 284 285 *sym0 = (Elf_Sym const *)(_w(symsec->sh_offset) 286 + (void *)ehdr); 287 288 *str0 = (char const *)(_w(strsec->sh_offset) 289 + (void *)ehdr); 290 291 *relp = rel0; 292 } 293 294 /* 295 * Look at the relocations in order to find the calls to mcount. 296 * Accumulate the section offsets that are found, and their relocation info, 297 * onto the end of the existing arrays. 298 */ 299 static uint_t *sift_rel_mcount(uint_t *mlocp, 300 unsigned const offbase, 301 Elf_Rel **const mrelpp, 302 Elf_Shdr const *const relhdr, 303 Elf_Ehdr const *const ehdr, 304 unsigned const recsym, 305 uint_t const recval, 306 unsigned const reltype) 307 { 308 uint_t *const mloc0 = mlocp; 309 Elf_Rel *mrelp = *mrelpp; 310 Elf_Sym const *sym0; 311 char const *str0; 312 Elf_Rel const *relp; 313 unsigned rel_entsize = _w(relhdr->sh_entsize); 314 unsigned const nrel = _w(relhdr->sh_size) / rel_entsize; 315 unsigned mcountsym = 0; 316 unsigned t; 317 318 get_sym_str_and_relp(relhdr, ehdr, &sym0, &str0, &relp); 319 320 for (t = nrel; t; --t) { 321 if (!mcountsym) 322 mcountsym = get_mcountsym(sym0, relp, str0); 323 324 if (mcountsym == Elf_r_sym(relp) && !is_fake_mcount(relp)) { 325 uint_t const addend = 326 _w(_w(relp->r_offset) - recval + mcount_adjust); 327 mrelp->r_offset = _w(offbase 328 + ((void *)mlocp - (void *)mloc0)); 329 Elf_r_info(mrelp, recsym, reltype); 330 if (rel_entsize == sizeof(Elf_Rela)) { 331 ((Elf_Rela *)mrelp)->r_addend = addend; 332 *mlocp++ = 0; 333 } else 334 *mlocp++ = addend; 335 336 mrelp = (Elf_Rel *)(rel_entsize + (void *)mrelp); 337 } 338 relp = (Elf_Rel const *)(rel_entsize + (void *)relp); 339 } 340 *mrelpp = mrelp; 341 return mlocp; 342 } 343 344 /* 345 * Read the relocation table again, but this time its called on sections 346 * that are not going to be traced. The mcount calls here will be converted 347 * into nops. 348 */ 349 static void nop_mcount(Elf_Shdr const *const relhdr, 350 Elf_Ehdr const *const ehdr, 351 const char *const txtname) 352 { 353 Elf_Shdr *const shdr0 = (Elf_Shdr *)(_w(ehdr->e_shoff) 354 + (void *)ehdr); 355 Elf_Sym const *sym0; 356 char const *str0; 357 Elf_Rel const *relp; 358 Elf_Shdr const *const shdr = &shdr0[w(relhdr->sh_info)]; 359 unsigned rel_entsize = _w(relhdr->sh_entsize); 360 unsigned const nrel = _w(relhdr->sh_size) / rel_entsize; 361 unsigned mcountsym = 0; 362 unsigned t; 363 int once = 0; 364 365 get_sym_str_and_relp(relhdr, ehdr, &sym0, &str0, &relp); 366 367 for (t = nrel; t; --t) { 368 int ret = -1; 369 370 if (!mcountsym) 371 mcountsym = get_mcountsym(sym0, relp, str0); 372 373 if (mcountsym == Elf_r_sym(relp) && !is_fake_mcount(relp)) { 374 if (make_nop) 375 ret = make_nop((void *)ehdr, shdr->sh_offset + relp->r_offset); 376 if (warn_on_notrace_sect && !once) { 377 printf("Section %s has mcount callers being ignored\n", 378 txtname); 379 once = 1; 380 /* just warn? */ 381 if (!make_nop) 382 return; 383 } 384 } 385 386 /* 387 * If we successfully removed the mcount, mark the relocation 388 * as a nop (don't do anything with it). 389 */ 390 if (!ret) { 391 Elf_Rel rel; 392 rel = *(Elf_Rel *)relp; 393 Elf_r_info(&rel, Elf_r_sym(relp), rel_type_nop); 394 ulseek(fd_map, (void *)relp - (void *)ehdr, SEEK_SET); 395 uwrite(fd_map, &rel, sizeof(rel)); 396 } 397 relp = (Elf_Rel const *)(rel_entsize + (void *)relp); 398 } 399 } 400 401 402 /* 403 * Find a symbol in the given section, to be used as the base for relocating 404 * the table of offsets of calls to mcount. A local or global symbol suffices, 405 * but avoid a Weak symbol because it may be overridden; the change in value 406 * would invalidate the relocations of the offsets of the calls to mcount. 407 * Often the found symbol will be the unnamed local symbol generated by 408 * GNU 'as' for the start of each section. For example: 409 * Num: Value Size Type Bind Vis Ndx Name 410 * 2: 00000000 0 SECTION LOCAL DEFAULT 1 411 */ 412 static unsigned find_secsym_ndx(unsigned const txtndx, 413 char const *const txtname, 414 uint_t *const recvalp, 415 Elf_Shdr const *const symhdr, 416 Elf_Ehdr const *const ehdr) 417 { 418 Elf_Sym const *const sym0 = (Elf_Sym const *)(_w(symhdr->sh_offset) 419 + (void *)ehdr); 420 unsigned const nsym = _w(symhdr->sh_size) / _w(symhdr->sh_entsize); 421 Elf_Sym const *symp; 422 unsigned t; 423 424 for (symp = sym0, t = nsym; t; --t, ++symp) { 425 unsigned int const st_bind = ELF_ST_BIND(symp->st_info); 426 427 if (txtndx == w2(symp->st_shndx) 428 /* avoid STB_WEAK */ 429 && (STB_LOCAL == st_bind || STB_GLOBAL == st_bind)) { 430 *recvalp = _w(symp->st_value); 431 return symp - sym0; 432 } 433 } 434 fprintf(stderr, "Cannot find symbol for section %d: %s.\n", 435 txtndx, txtname); 436 fail_file(); 437 } 438 439 440 /* Evade ISO C restriction: no declaration after statement in has_rel_mcount. */ 441 static char const * 442 __has_rel_mcount(Elf_Shdr const *const relhdr, /* is SHT_REL or SHT_RELA */ 443 Elf_Shdr const *const shdr0, 444 char const *const shstrtab, 445 char const *const fname) 446 { 447 /* .sh_info depends on .sh_type == SHT_REL[,A] */ 448 Elf_Shdr const *const txthdr = &shdr0[w(relhdr->sh_info)]; 449 char const *const txtname = &shstrtab[w(txthdr->sh_name)]; 450 451 if (strcmp("__mcount_loc", txtname) == 0) { 452 fprintf(stderr, "warning: __mcount_loc already exists: %s\n", 453 fname); 454 succeed_file(); 455 } 456 if (w(txthdr->sh_type) != SHT_PROGBITS || 457 !(w(txthdr->sh_flags) & SHF_EXECINSTR)) 458 return NULL; 459 return txtname; 460 } 461 462 static char const *has_rel_mcount(Elf_Shdr const *const relhdr, 463 Elf_Shdr const *const shdr0, 464 char const *const shstrtab, 465 char const *const fname) 466 { 467 if (w(relhdr->sh_type) != SHT_REL && w(relhdr->sh_type) != SHT_RELA) 468 return NULL; 469 return __has_rel_mcount(relhdr, shdr0, shstrtab, fname); 470 } 471 472 473 static unsigned tot_relsize(Elf_Shdr const *const shdr0, 474 unsigned nhdr, 475 const char *const shstrtab, 476 const char *const fname) 477 { 478 unsigned totrelsz = 0; 479 Elf_Shdr const *shdrp = shdr0; 480 char const *txtname; 481 482 for (; nhdr; --nhdr, ++shdrp) { 483 txtname = has_rel_mcount(shdrp, shdr0, shstrtab, fname); 484 if (txtname && is_mcounted_section_name(txtname)) 485 totrelsz += _w(shdrp->sh_size); 486 } 487 return totrelsz; 488 } 489 490 491 /* Overall supervision for Elf32 ET_REL file. */ 492 static void 493 do_func(Elf_Ehdr *const ehdr, char const *const fname, unsigned const reltype) 494 { 495 Elf_Shdr *const shdr0 = (Elf_Shdr *)(_w(ehdr->e_shoff) 496 + (void *)ehdr); 497 unsigned const nhdr = w2(ehdr->e_shnum); 498 Elf_Shdr *const shstr = &shdr0[w2(ehdr->e_shstrndx)]; 499 char const *const shstrtab = (char const *)(_w(shstr->sh_offset) 500 + (void *)ehdr); 501 502 Elf_Shdr const *relhdr; 503 unsigned k; 504 505 /* Upper bound on space: assume all relevant relocs are for mcount. */ 506 unsigned const totrelsz = tot_relsize(shdr0, nhdr, shstrtab, fname); 507 Elf_Rel *const mrel0 = umalloc(totrelsz); 508 Elf_Rel * mrelp = mrel0; 509 510 /* 2*sizeof(address) <= sizeof(Elf_Rel) */ 511 uint_t *const mloc0 = umalloc(totrelsz>>1); 512 uint_t * mlocp = mloc0; 513 514 unsigned rel_entsize = 0; 515 unsigned symsec_sh_link = 0; 516 517 for (relhdr = shdr0, k = nhdr; k; --k, ++relhdr) { 518 char const *const txtname = has_rel_mcount(relhdr, shdr0, 519 shstrtab, fname); 520 if (txtname && is_mcounted_section_name(txtname)) { 521 uint_t recval = 0; 522 unsigned const recsym = find_secsym_ndx( 523 w(relhdr->sh_info), txtname, &recval, 524 &shdr0[symsec_sh_link = w(relhdr->sh_link)], 525 ehdr); 526 527 rel_entsize = _w(relhdr->sh_entsize); 528 mlocp = sift_rel_mcount(mlocp, 529 (void *)mlocp - (void *)mloc0, &mrelp, 530 relhdr, ehdr, recsym, recval, reltype); 531 } else if (txtname && (warn_on_notrace_sect || make_nop)) { 532 /* 533 * This section is ignored by ftrace, but still 534 * has mcount calls. Convert them to nops now. 535 */ 536 nop_mcount(relhdr, ehdr, txtname); 537 } 538 } 539 if (mloc0 != mlocp) { 540 append_func(ehdr, shstr, mloc0, mlocp, mrel0, mrelp, 541 rel_entsize, symsec_sh_link); 542 } 543 free(mrel0); 544 free(mloc0); 545 } 546