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