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