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 sift_rel_mcount 26 #undef find_secsym_ndx 27 #undef __has_rel_mcount 28 #undef has_rel_mcount 29 #undef tot_relsize 30 #undef do_func 31 #undef Elf_Addr 32 #undef Elf_Ehdr 33 #undef Elf_Shdr 34 #undef Elf_Rel 35 #undef Elf_Rela 36 #undef Elf_Sym 37 #undef ELF_R_SYM 38 #undef Elf_r_sym 39 #undef ELF_R_INFO 40 #undef Elf_r_info 41 #undef ELF_ST_BIND 42 #undef fn_ELF_R_SYM 43 #undef fn_ELF_R_INFO 44 #undef uint_t 45 #undef _w 46 #undef _align 47 #undef _size 48 49 #ifdef RECORD_MCOUNT_64 50 # define append_func append64 51 # define sift_rel_mcount sift64_rel_mcount 52 # define find_secsym_ndx find64_secsym_ndx 53 # define __has_rel_mcount __has64_rel_mcount 54 # define has_rel_mcount has64_rel_mcount 55 # define tot_relsize tot64_relsize 56 # define do_func do64 57 # define is_fake_mcount is_fake_mcount64 58 # define fn_is_fake_mcount fn_is_fake_mcount64 59 # define MIPS_is_fake_mcount MIPS64_is_fake_mcount 60 # define Elf_Addr Elf64_Addr 61 # define Elf_Ehdr Elf64_Ehdr 62 # define Elf_Shdr Elf64_Shdr 63 # define Elf_Rel Elf64_Rel 64 # define Elf_Rela Elf64_Rela 65 # define Elf_Sym Elf64_Sym 66 # define ELF_R_SYM ELF64_R_SYM 67 # define Elf_r_sym Elf64_r_sym 68 # define ELF_R_INFO ELF64_R_INFO 69 # define Elf_r_info Elf64_r_info 70 # define ELF_ST_BIND ELF64_ST_BIND 71 # define fn_ELF_R_SYM fn_ELF64_R_SYM 72 # define fn_ELF_R_INFO fn_ELF64_R_INFO 73 # define uint_t uint64_t 74 # define _w w8 75 # define _align 7u 76 # define _size 8 77 #else 78 # define append_func append32 79 # define sift_rel_mcount sift32_rel_mcount 80 # define find_secsym_ndx find32_secsym_ndx 81 # define __has_rel_mcount __has32_rel_mcount 82 # define has_rel_mcount has32_rel_mcount 83 # define tot_relsize tot32_relsize 84 # define do_func do32 85 # define is_fake_mcount is_fake_mcount32 86 # define fn_is_fake_mcount fn_is_fake_mcount32 87 # define MIPS_is_fake_mcount MIPS32_is_fake_mcount 88 # define Elf_Addr Elf32_Addr 89 # define Elf_Ehdr Elf32_Ehdr 90 # define Elf_Shdr Elf32_Shdr 91 # define Elf_Rel Elf32_Rel 92 # define Elf_Rela Elf32_Rela 93 # define Elf_Sym Elf32_Sym 94 # define ELF_R_SYM ELF32_R_SYM 95 # define Elf_r_sym Elf32_r_sym 96 # define ELF_R_INFO ELF32_R_INFO 97 # define Elf_r_info Elf32_r_info 98 # define ELF_ST_BIND ELF32_ST_BIND 99 # define fn_ELF_R_SYM fn_ELF32_R_SYM 100 # define fn_ELF_R_INFO fn_ELF32_R_INFO 101 # define uint_t uint32_t 102 # define _w w 103 # define _align 3u 104 # define _size 4 105 #endif 106 107 /* Functions and pointers that do_file() may override for specific e_machine. */ 108 static int fn_is_fake_mcount(Elf_Rel const *rp) 109 { 110 return 0; 111 } 112 static int (*is_fake_mcount)(Elf_Rel const *rp) = fn_is_fake_mcount; 113 114 static uint_t fn_ELF_R_SYM(Elf_Rel const *rp) 115 { 116 return ELF_R_SYM(_w(rp->r_info)); 117 } 118 static uint_t (*Elf_r_sym)(Elf_Rel const *rp) = fn_ELF_R_SYM; 119 120 static void fn_ELF_R_INFO(Elf_Rel *const rp, unsigned sym, unsigned type) 121 { 122 rp->r_info = _w(ELF_R_INFO(sym, type)); 123 } 124 static void (*Elf_r_info)(Elf_Rel *const rp, unsigned sym, unsigned type) = fn_ELF_R_INFO; 125 126 /* 127 * MIPS mcount long call has 2 _mcount symbols, only the position of the 1st 128 * _mcount symbol is needed for dynamic function tracer, with it, to disable 129 * tracing(ftrace_make_nop), the instruction in the position is replaced with 130 * the "b label" instruction, to enable tracing(ftrace_make_call), replace the 131 * instruction back. So, here, we set the 2nd one as fake and filter it. 132 * 133 * c: 3c030000 lui v1,0x0 <--> b label 134 * c: R_MIPS_HI16 _mcount 135 * c: R_MIPS_NONE *ABS* 136 * c: R_MIPS_NONE *ABS* 137 * 10: 64630000 daddiu v1,v1,0 138 * 10: R_MIPS_LO16 _mcount 139 * 10: R_MIPS_NONE *ABS* 140 * 10: R_MIPS_NONE *ABS* 141 * 14: 03e0082d move at,ra 142 * 18: 0060f809 jalr v1 143 * label: 144 */ 145 #define MIPS_FAKEMCOUNT_OFFSET 4 146 147 static int MIPS_is_fake_mcount(Elf_Rel const *rp) 148 { 149 static Elf_Addr old_r_offset; 150 Elf_Addr current_r_offset = _w(rp->r_offset); 151 int is_fake; 152 153 is_fake = old_r_offset && 154 (current_r_offset - old_r_offset == MIPS_FAKEMCOUNT_OFFSET); 155 old_r_offset = current_r_offset; 156 157 return is_fake; 158 } 159 160 /* Append the new shstrtab, Elf_Shdr[], __mcount_loc and its relocations. */ 161 static void append_func(Elf_Ehdr *const ehdr, 162 Elf_Shdr *const shstr, 163 uint_t const *const mloc0, 164 uint_t const *const mlocp, 165 Elf_Rel const *const mrel0, 166 Elf_Rel const *const mrelp, 167 unsigned int const rel_entsize, 168 unsigned int const symsec_sh_link) 169 { 170 /* Begin constructing output file */ 171 Elf_Shdr mcsec; 172 char const *mc_name = (sizeof(Elf_Rela) == rel_entsize) 173 ? ".rela__mcount_loc" 174 : ".rel__mcount_loc"; 175 unsigned const old_shnum = w2(ehdr->e_shnum); 176 uint_t const old_shoff = _w(ehdr->e_shoff); 177 uint_t const old_shstr_sh_size = _w(shstr->sh_size); 178 uint_t const old_shstr_sh_offset = _w(shstr->sh_offset); 179 uint_t t = 1 + strlen(mc_name) + _w(shstr->sh_size); 180 uint_t new_e_shoff; 181 182 shstr->sh_size = _w(t); 183 shstr->sh_offset = _w(sb.st_size); 184 t += sb.st_size; 185 t += (_align & -t); /* word-byte align */ 186 new_e_shoff = t; 187 188 /* body for new shstrtab */ 189 ulseek(fd_map, sb.st_size, SEEK_SET); 190 uwrite(fd_map, old_shstr_sh_offset + (void *)ehdr, old_shstr_sh_size); 191 uwrite(fd_map, mc_name, 1 + strlen(mc_name)); 192 193 /* old(modified) Elf_Shdr table, word-byte aligned */ 194 ulseek(fd_map, t, SEEK_SET); 195 t += sizeof(Elf_Shdr) * old_shnum; 196 uwrite(fd_map, old_shoff + (void *)ehdr, 197 sizeof(Elf_Shdr) * old_shnum); 198 199 /* new sections __mcount_loc and .rel__mcount_loc */ 200 t += 2*sizeof(mcsec); 201 mcsec.sh_name = w((sizeof(Elf_Rela) == rel_entsize) + strlen(".rel") 202 + old_shstr_sh_size); 203 mcsec.sh_type = w(SHT_PROGBITS); 204 mcsec.sh_flags = _w(SHF_ALLOC); 205 mcsec.sh_addr = 0; 206 mcsec.sh_offset = _w(t); 207 mcsec.sh_size = _w((void *)mlocp - (void *)mloc0); 208 mcsec.sh_link = 0; 209 mcsec.sh_info = 0; 210 mcsec.sh_addralign = _w(_size); 211 mcsec.sh_entsize = _w(_size); 212 uwrite(fd_map, &mcsec, sizeof(mcsec)); 213 214 mcsec.sh_name = w(old_shstr_sh_size); 215 mcsec.sh_type = (sizeof(Elf_Rela) == rel_entsize) 216 ? w(SHT_RELA) 217 : w(SHT_REL); 218 mcsec.sh_flags = 0; 219 mcsec.sh_addr = 0; 220 mcsec.sh_offset = _w((void *)mlocp - (void *)mloc0 + t); 221 mcsec.sh_size = _w((void *)mrelp - (void *)mrel0); 222 mcsec.sh_link = w(symsec_sh_link); 223 mcsec.sh_info = w(old_shnum); 224 mcsec.sh_addralign = _w(_size); 225 mcsec.sh_entsize = _w(rel_entsize); 226 uwrite(fd_map, &mcsec, sizeof(mcsec)); 227 228 uwrite(fd_map, mloc0, (void *)mlocp - (void *)mloc0); 229 uwrite(fd_map, mrel0, (void *)mrelp - (void *)mrel0); 230 231 ehdr->e_shoff = _w(new_e_shoff); 232 ehdr->e_shnum = w2(2 + w2(ehdr->e_shnum)); /* {.rel,}__mcount_loc */ 233 ulseek(fd_map, 0, SEEK_SET); 234 uwrite(fd_map, ehdr, sizeof(*ehdr)); 235 } 236 237 /* 238 * Look at the relocations in order to find the calls to mcount. 239 * Accumulate the section offsets that are found, and their relocation info, 240 * onto the end of the existing arrays. 241 */ 242 static uint_t *sift_rel_mcount(uint_t *mlocp, 243 unsigned const offbase, 244 Elf_Rel **const mrelpp, 245 Elf_Shdr const *const relhdr, 246 Elf_Ehdr const *const ehdr, 247 unsigned const recsym, 248 uint_t const recval, 249 unsigned const reltype) 250 { 251 uint_t *const mloc0 = mlocp; 252 Elf_Rel *mrelp = *mrelpp; 253 Elf_Shdr *const shdr0 = (Elf_Shdr *)(_w(ehdr->e_shoff) 254 + (void *)ehdr); 255 unsigned const symsec_sh_link = w(relhdr->sh_link); 256 Elf_Shdr const *const symsec = &shdr0[symsec_sh_link]; 257 Elf_Sym const *const sym0 = (Elf_Sym const *)(_w(symsec->sh_offset) 258 + (void *)ehdr); 259 260 Elf_Shdr const *const strsec = &shdr0[w(symsec->sh_link)]; 261 char const *const str0 = (char const *)(_w(strsec->sh_offset) 262 + (void *)ehdr); 263 264 Elf_Rel const *const rel0 = (Elf_Rel const *)(_w(relhdr->sh_offset) 265 + (void *)ehdr); 266 unsigned rel_entsize = _w(relhdr->sh_entsize); 267 unsigned const nrel = _w(relhdr->sh_size) / rel_entsize; 268 Elf_Rel const *relp = rel0; 269 270 unsigned mcountsym = 0; 271 unsigned t; 272 273 for (t = nrel; t; --t) { 274 if (!mcountsym) { 275 Elf_Sym const *const symp = 276 &sym0[Elf_r_sym(relp)]; 277 char const *symname = &str0[w(symp->st_name)]; 278 char const *mcount = '_' == gpfx ? "_mcount" : "mcount"; 279 280 if ('.' == symname[0]) 281 ++symname; /* ppc64 hack */ 282 if (0 == strcmp(mcount, symname) || 283 (altmcount && 0 == strcmp(altmcount, symname))) 284 mcountsym = Elf_r_sym(relp); 285 } 286 287 if (mcountsym == Elf_r_sym(relp) && !is_fake_mcount(relp)) { 288 uint_t const addend = _w(_w(relp->r_offset) - recval); 289 290 mrelp->r_offset = _w(offbase 291 + ((void *)mlocp - (void *)mloc0)); 292 Elf_r_info(mrelp, recsym, reltype); 293 if (sizeof(Elf_Rela) == rel_entsize) { 294 ((Elf_Rela *)mrelp)->r_addend = addend; 295 *mlocp++ = 0; 296 } else 297 *mlocp++ = addend; 298 299 mrelp = (Elf_Rel *)(rel_entsize + (void *)mrelp); 300 } 301 relp = (Elf_Rel const *)(rel_entsize + (void *)relp); 302 } 303 *mrelpp = mrelp; 304 return mlocp; 305 } 306 307 308 /* 309 * Find a symbol in the given section, to be used as the base for relocating 310 * the table of offsets of calls to mcount. A local or global symbol suffices, 311 * but avoid a Weak symbol because it may be overridden; the change in value 312 * would invalidate the relocations of the offsets of the calls to mcount. 313 * Often the found symbol will be the unnamed local symbol generated by 314 * GNU 'as' for the start of each section. For example: 315 * Num: Value Size Type Bind Vis Ndx Name 316 * 2: 00000000 0 SECTION LOCAL DEFAULT 1 317 */ 318 static unsigned find_secsym_ndx(unsigned const txtndx, 319 char const *const txtname, 320 uint_t *const recvalp, 321 Elf_Shdr const *const symhdr, 322 Elf_Ehdr const *const ehdr) 323 { 324 Elf_Sym const *const sym0 = (Elf_Sym const *)(_w(symhdr->sh_offset) 325 + (void *)ehdr); 326 unsigned const nsym = _w(symhdr->sh_size) / _w(symhdr->sh_entsize); 327 Elf_Sym const *symp; 328 unsigned t; 329 330 for (symp = sym0, t = nsym; t; --t, ++symp) { 331 unsigned int const st_bind = ELF_ST_BIND(symp->st_info); 332 333 if (txtndx == w2(symp->st_shndx) 334 /* avoid STB_WEAK */ 335 && (STB_LOCAL == st_bind || STB_GLOBAL == st_bind)) { 336 *recvalp = _w(symp->st_value); 337 return symp - sym0; 338 } 339 } 340 fprintf(stderr, "Cannot find symbol for section %d: %s.\n", 341 txtndx, txtname); 342 fail_file(); 343 } 344 345 346 /* Evade ISO C restriction: no declaration after statement in has_rel_mcount. */ 347 static char const * 348 __has_rel_mcount(Elf_Shdr const *const relhdr, /* is SHT_REL or SHT_RELA */ 349 Elf_Shdr const *const shdr0, 350 char const *const shstrtab, 351 char const *const fname) 352 { 353 /* .sh_info depends on .sh_type == SHT_REL[,A] */ 354 Elf_Shdr const *const txthdr = &shdr0[w(relhdr->sh_info)]; 355 char const *const txtname = &shstrtab[w(txthdr->sh_name)]; 356 357 if (0 == strcmp("__mcount_loc", txtname)) { 358 fprintf(stderr, "warning: __mcount_loc already exists: %s\n", 359 fname); 360 succeed_file(); 361 } 362 if (SHT_PROGBITS != w(txthdr->sh_type) || 363 !is_mcounted_section_name(txtname)) 364 return NULL; 365 return txtname; 366 } 367 368 static char const *has_rel_mcount(Elf_Shdr const *const relhdr, 369 Elf_Shdr const *const shdr0, 370 char const *const shstrtab, 371 char const *const fname) 372 { 373 if (SHT_REL != w(relhdr->sh_type) && SHT_RELA != w(relhdr->sh_type)) 374 return NULL; 375 return __has_rel_mcount(relhdr, shdr0, shstrtab, fname); 376 } 377 378 379 static unsigned tot_relsize(Elf_Shdr const *const shdr0, 380 unsigned nhdr, 381 const char *const shstrtab, 382 const char *const fname) 383 { 384 unsigned totrelsz = 0; 385 Elf_Shdr const *shdrp = shdr0; 386 387 for (; nhdr; --nhdr, ++shdrp) { 388 if (has_rel_mcount(shdrp, shdr0, shstrtab, fname)) 389 totrelsz += _w(shdrp->sh_size); 390 } 391 return totrelsz; 392 } 393 394 395 /* Overall supervision for Elf32 ET_REL file. */ 396 static void 397 do_func(Elf_Ehdr *const ehdr, char const *const fname, unsigned const reltype) 398 { 399 Elf_Shdr *const shdr0 = (Elf_Shdr *)(_w(ehdr->e_shoff) 400 + (void *)ehdr); 401 unsigned const nhdr = w2(ehdr->e_shnum); 402 Elf_Shdr *const shstr = &shdr0[w2(ehdr->e_shstrndx)]; 403 char const *const shstrtab = (char const *)(_w(shstr->sh_offset) 404 + (void *)ehdr); 405 406 Elf_Shdr const *relhdr; 407 unsigned k; 408 409 /* Upper bound on space: assume all relevant relocs are for mcount. */ 410 unsigned const totrelsz = tot_relsize(shdr0, nhdr, shstrtab, fname); 411 Elf_Rel *const mrel0 = umalloc(totrelsz); 412 Elf_Rel * mrelp = mrel0; 413 414 /* 2*sizeof(address) <= sizeof(Elf_Rel) */ 415 uint_t *const mloc0 = umalloc(totrelsz>>1); 416 uint_t * mlocp = mloc0; 417 418 unsigned rel_entsize = 0; 419 unsigned symsec_sh_link = 0; 420 421 for (relhdr = shdr0, k = nhdr; k; --k, ++relhdr) { 422 char const *const txtname = has_rel_mcount(relhdr, shdr0, 423 shstrtab, fname); 424 if (txtname) { 425 uint_t recval = 0; 426 unsigned const recsym = find_secsym_ndx( 427 w(relhdr->sh_info), txtname, &recval, 428 &shdr0[symsec_sh_link = w(relhdr->sh_link)], 429 ehdr); 430 431 rel_entsize = _w(relhdr->sh_entsize); 432 mlocp = sift_rel_mcount(mlocp, 433 (void *)mlocp - (void *)mloc0, &mrelp, 434 relhdr, ehdr, recsym, recval, reltype); 435 } 436 } 437 if (mloc0 != mlocp) { 438 append_func(ehdr, shstr, mloc0, mlocp, mrel0, mrelp, 439 rel_entsize, symsec_sh_link); 440 } 441 free(mrel0); 442 free(mloc0); 443 } 444