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 sift_rel_mcount 23 #undef find_secsym_ndx 24 #undef __has_rel_mcount 25 #undef has_rel_mcount 26 #undef tot_relsize 27 #undef do_func 28 #undef Elf_Ehdr 29 #undef Elf_Shdr 30 #undef Elf_Rel 31 #undef Elf_Rela 32 #undef Elf_Sym 33 #undef ELF_R_SYM 34 #undef ELF_R_INFO 35 #undef ELF_ST_BIND 36 #undef uint_t 37 #undef _w 38 #undef _align 39 #undef _size 40 41 #ifdef RECORD_MCOUNT_64 42 # define append_func append64 43 # define sift_rel_mcount sift64_rel_mcount 44 # define find_secsym_ndx find64_secsym_ndx 45 # define __has_rel_mcount __has64_rel_mcount 46 # define has_rel_mcount has64_rel_mcount 47 # define tot_relsize tot64_relsize 48 # define do_func do64 49 # define Elf_Ehdr Elf64_Ehdr 50 # define Elf_Shdr Elf64_Shdr 51 # define Elf_Rel Elf64_Rel 52 # define Elf_Rela Elf64_Rela 53 # define Elf_Sym Elf64_Sym 54 # define ELF_R_SYM ELF64_R_SYM 55 # define ELF_R_INFO ELF64_R_INFO 56 # define ELF_ST_BIND ELF64_ST_BIND 57 # define uint_t uint64_t 58 # define _w w8 59 # define _align 7u 60 # define _size 8 61 #else 62 # define append_func append32 63 # define sift_rel_mcount sift32_rel_mcount 64 # define find_secsym_ndx find32_secsym_ndx 65 # define __has_rel_mcount __has32_rel_mcount 66 # define has_rel_mcount has32_rel_mcount 67 # define tot_relsize tot32_relsize 68 # define do_func do32 69 # define Elf_Ehdr Elf32_Ehdr 70 # define Elf_Shdr Elf32_Shdr 71 # define Elf_Rel Elf32_Rel 72 # define Elf_Rela Elf32_Rela 73 # define Elf_Sym Elf32_Sym 74 # define ELF_R_SYM ELF32_R_SYM 75 # define ELF_R_INFO ELF32_R_INFO 76 # define ELF_ST_BIND ELF32_ST_BIND 77 # define uint_t uint32_t 78 # define _w w 79 # define _align 3u 80 # define _size 4 81 #endif 82 83 /* Append the new shstrtab, Elf_Shdr[], __mcount_loc and its relocations. */ 84 static void append_func(Elf_Ehdr *const ehdr, 85 Elf_Shdr *const shstr, 86 uint_t const *const mloc0, 87 uint_t const *const mlocp, 88 Elf_Rel const *const mrel0, 89 Elf_Rel const *const mrelp, 90 unsigned int const rel_entsize, 91 unsigned int const symsec_sh_link) 92 { 93 /* Begin constructing output file */ 94 Elf_Shdr mcsec; 95 char const *mc_name = (sizeof(Elf_Rela) == rel_entsize) 96 ? ".rela__mcount_loc" 97 : ".rel__mcount_loc"; 98 unsigned const old_shnum = w2(ehdr->e_shnum); 99 uint_t const old_shoff = _w(ehdr->e_shoff); 100 uint_t const old_shstr_sh_size = _w(shstr->sh_size); 101 uint_t const old_shstr_sh_offset = _w(shstr->sh_offset); 102 uint_t t = 1 + strlen(mc_name) + _w(shstr->sh_size); 103 uint_t new_e_shoff; 104 105 shstr->sh_size = _w(t); 106 shstr->sh_offset = _w(sb.st_size); 107 t += sb.st_size; 108 t += (_align & -t); /* word-byte align */ 109 new_e_shoff = t; 110 111 /* body for new shstrtab */ 112 ulseek(fd_map, sb.st_size, SEEK_SET); 113 uwrite(fd_map, old_shstr_sh_offset + (void *)ehdr, old_shstr_sh_size); 114 uwrite(fd_map, mc_name, 1 + strlen(mc_name)); 115 116 /* old(modified) Elf_Shdr table, word-byte aligned */ 117 ulseek(fd_map, t, SEEK_SET); 118 t += sizeof(Elf_Shdr) * old_shnum; 119 uwrite(fd_map, old_shoff + (void *)ehdr, 120 sizeof(Elf_Shdr) * old_shnum); 121 122 /* new sections __mcount_loc and .rel__mcount_loc */ 123 t += 2*sizeof(mcsec); 124 mcsec.sh_name = w((sizeof(Elf_Rela) == rel_entsize) + strlen(".rel") 125 + old_shstr_sh_size); 126 mcsec.sh_type = w(SHT_PROGBITS); 127 mcsec.sh_flags = _w(SHF_ALLOC); 128 mcsec.sh_addr = 0; 129 mcsec.sh_offset = _w(t); 130 mcsec.sh_size = _w((void *)mlocp - (void *)mloc0); 131 mcsec.sh_link = 0; 132 mcsec.sh_info = 0; 133 mcsec.sh_addralign = _w(_size); 134 mcsec.sh_entsize = _w(_size); 135 uwrite(fd_map, &mcsec, sizeof(mcsec)); 136 137 mcsec.sh_name = w(old_shstr_sh_size); 138 mcsec.sh_type = (sizeof(Elf_Rela) == rel_entsize) 139 ? w(SHT_RELA) 140 : w(SHT_REL); 141 mcsec.sh_flags = 0; 142 mcsec.sh_addr = 0; 143 mcsec.sh_offset = _w((void *)mlocp - (void *)mloc0 + t); 144 mcsec.sh_size = _w((void *)mrelp - (void *)mrel0); 145 mcsec.sh_link = w(symsec_sh_link); 146 mcsec.sh_info = w(old_shnum); 147 mcsec.sh_addralign = _w(_size); 148 mcsec.sh_entsize = _w(rel_entsize); 149 uwrite(fd_map, &mcsec, sizeof(mcsec)); 150 151 uwrite(fd_map, mloc0, (void *)mlocp - (void *)mloc0); 152 uwrite(fd_map, mrel0, (void *)mrelp - (void *)mrel0); 153 154 ehdr->e_shoff = _w(new_e_shoff); 155 ehdr->e_shnum = w2(2 + w2(ehdr->e_shnum)); /* {.rel,}__mcount_loc */ 156 ulseek(fd_map, 0, SEEK_SET); 157 uwrite(fd_map, ehdr, sizeof(*ehdr)); 158 } 159 160 161 /* 162 * Look at the relocations in order to find the calls to mcount. 163 * Accumulate the section offsets that are found, and their relocation info, 164 * onto the end of the existing arrays. 165 */ 166 static uint_t *sift_rel_mcount(uint_t *mlocp, 167 unsigned const offbase, 168 Elf_Rel **const mrelpp, 169 Elf_Shdr const *const relhdr, 170 Elf_Ehdr const *const ehdr, 171 unsigned const recsym, 172 uint_t const recval, 173 unsigned const reltype) 174 { 175 uint_t *const mloc0 = mlocp; 176 Elf_Rel *mrelp = *mrelpp; 177 Elf_Shdr *const shdr0 = (Elf_Shdr *)(_w(ehdr->e_shoff) 178 + (void *)ehdr); 179 unsigned const symsec_sh_link = w(relhdr->sh_link); 180 Elf_Shdr const *const symsec = &shdr0[symsec_sh_link]; 181 Elf_Sym const *const sym0 = (Elf_Sym const *)(_w(symsec->sh_offset) 182 + (void *)ehdr); 183 184 Elf_Shdr const *const strsec = &shdr0[w(symsec->sh_link)]; 185 char const *const str0 = (char const *)(_w(strsec->sh_offset) 186 + (void *)ehdr); 187 188 Elf_Rel const *const rel0 = (Elf_Rel const *)(_w(relhdr->sh_offset) 189 + (void *)ehdr); 190 unsigned rel_entsize = _w(relhdr->sh_entsize); 191 unsigned const nrel = _w(relhdr->sh_size) / rel_entsize; 192 Elf_Rel const *relp = rel0; 193 194 unsigned mcountsym = 0; 195 unsigned t; 196 197 for (t = nrel; t; --t) { 198 if (!mcountsym) { 199 Elf_Sym const *const symp = 200 &sym0[ELF_R_SYM(_w(relp->r_info))]; 201 char const *symname = &str0[w(symp->st_name)]; 202 203 if ('.' == symname[0]) 204 ++symname; /* ppc64 hack */ 205 if (0 == strcmp((('_' == gpfx) ? "_mcount" : "mcount"), 206 symname)) 207 mcountsym = ELF_R_SYM(_w(relp->r_info)); 208 } 209 210 if (mcountsym == ELF_R_SYM(_w(relp->r_info))) { 211 uint_t const addend = _w(_w(relp->r_offset) - recval); 212 213 mrelp->r_offset = _w(offbase 214 + ((void *)mlocp - (void *)mloc0)); 215 mrelp->r_info = _w(ELF_R_INFO(recsym, reltype)); 216 if (sizeof(Elf_Rela) == rel_entsize) { 217 ((Elf_Rela *)mrelp)->r_addend = addend; 218 *mlocp++ = 0; 219 } else 220 *mlocp++ = addend; 221 222 mrelp = (Elf_Rel *)(rel_entsize + (void *)mrelp); 223 } 224 relp = (Elf_Rel const *)(rel_entsize + (void *)relp); 225 } 226 *mrelpp = mrelp; 227 return mlocp; 228 } 229 230 231 /* 232 * Find a symbol in the given section, to be used as the base for relocating 233 * the table of offsets of calls to mcount. A local or global symbol suffices, 234 * but avoid a Weak symbol because it may be overridden; the change in value 235 * would invalidate the relocations of the offsets of the calls to mcount. 236 * Often the found symbol will be the unnamed local symbol generated by 237 * GNU 'as' for the start of each section. For example: 238 * Num: Value Size Type Bind Vis Ndx Name 239 * 2: 00000000 0 SECTION LOCAL DEFAULT 1 240 */ 241 static unsigned find_secsym_ndx(unsigned const txtndx, 242 char const *const txtname, 243 uint_t *const recvalp, 244 Elf_Shdr const *const symhdr, 245 Elf_Ehdr const *const ehdr) 246 { 247 Elf_Sym const *const sym0 = (Elf_Sym const *)(_w(symhdr->sh_offset) 248 + (void *)ehdr); 249 unsigned const nsym = _w(symhdr->sh_size) / _w(symhdr->sh_entsize); 250 Elf_Sym const *symp; 251 unsigned t; 252 253 for (symp = sym0, t = nsym; t; --t, ++symp) { 254 unsigned int const st_bind = ELF_ST_BIND(symp->st_info); 255 256 if (txtndx == w2(symp->st_shndx) 257 /* avoid STB_WEAK */ 258 && (STB_LOCAL == st_bind || STB_GLOBAL == st_bind)) { 259 *recvalp = _w(symp->st_value); 260 return symp - sym0; 261 } 262 } 263 fprintf(stderr, "Cannot find symbol for section %d: %s.\n", 264 txtndx, txtname); 265 fail_file(); 266 } 267 268 269 /* Evade ISO C restriction: no declaration after statement in has_rel_mcount. */ 270 static char const * 271 __has_rel_mcount(Elf_Shdr const *const relhdr, /* is SHT_REL or SHT_RELA */ 272 Elf_Shdr const *const shdr0, 273 char const *const shstrtab, 274 char const *const fname) 275 { 276 /* .sh_info depends on .sh_type == SHT_REL[,A] */ 277 Elf_Shdr const *const txthdr = &shdr0[w(relhdr->sh_info)]; 278 char const *const txtname = &shstrtab[w(txthdr->sh_name)]; 279 280 if (0 == strcmp("__mcount_loc", txtname)) { 281 fprintf(stderr, "warning: __mcount_loc already exists: %s\n", 282 fname); 283 succeed_file(); 284 } 285 if (SHT_PROGBITS != w(txthdr->sh_type) || 286 !is_mcounted_section_name(txtname)) 287 return NULL; 288 return txtname; 289 } 290 291 static char const *has_rel_mcount(Elf_Shdr const *const relhdr, 292 Elf_Shdr const *const shdr0, 293 char const *const shstrtab, 294 char const *const fname) 295 { 296 if (SHT_REL != w(relhdr->sh_type) && SHT_RELA != w(relhdr->sh_type)) 297 return NULL; 298 return __has_rel_mcount(relhdr, shdr0, shstrtab, fname); 299 } 300 301 302 static unsigned tot_relsize(Elf_Shdr const *const shdr0, 303 unsigned nhdr, 304 const char *const shstrtab, 305 const char *const fname) 306 { 307 unsigned totrelsz = 0; 308 Elf_Shdr const *shdrp = shdr0; 309 310 for (; nhdr; --nhdr, ++shdrp) { 311 if (has_rel_mcount(shdrp, shdr0, shstrtab, fname)) 312 totrelsz += _w(shdrp->sh_size); 313 } 314 return totrelsz; 315 } 316 317 318 /* Overall supervision for Elf32 ET_REL file. */ 319 static void 320 do_func(Elf_Ehdr *const ehdr, char const *const fname, unsigned const reltype) 321 { 322 Elf_Shdr *const shdr0 = (Elf_Shdr *)(_w(ehdr->e_shoff) 323 + (void *)ehdr); 324 unsigned const nhdr = w2(ehdr->e_shnum); 325 Elf_Shdr *const shstr = &shdr0[w2(ehdr->e_shstrndx)]; 326 char const *const shstrtab = (char const *)(_w(shstr->sh_offset) 327 + (void *)ehdr); 328 329 Elf_Shdr const *relhdr; 330 unsigned k; 331 332 /* Upper bound on space: assume all relevant relocs are for mcount. */ 333 unsigned const totrelsz = tot_relsize(shdr0, nhdr, shstrtab, fname); 334 Elf_Rel *const mrel0 = umalloc(totrelsz); 335 Elf_Rel * mrelp = mrel0; 336 337 /* 2*sizeof(address) <= sizeof(Elf_Rel) */ 338 uint_t *const mloc0 = umalloc(totrelsz>>1); 339 uint_t * mlocp = mloc0; 340 341 unsigned rel_entsize = 0; 342 unsigned symsec_sh_link = 0; 343 344 for (relhdr = shdr0, k = nhdr; k; --k, ++relhdr) { 345 char const *const txtname = has_rel_mcount(relhdr, shdr0, 346 shstrtab, fname); 347 if (txtname) { 348 uint_t recval = 0; 349 unsigned const recsym = find_secsym_ndx( 350 w(relhdr->sh_info), txtname, &recval, 351 &shdr0[symsec_sh_link = w(relhdr->sh_link)], 352 ehdr); 353 354 rel_entsize = _w(relhdr->sh_entsize); 355 mlocp = sift_rel_mcount(mlocp, 356 (void *)mlocp - (void *)mloc0, &mrelp, 357 relhdr, ehdr, recsym, recval, reltype); 358 } 359 } 360 if (mloc0 != mlocp) { 361 append_func(ehdr, shstr, mloc0, mlocp, mrel0, mrelp, 362 rel_entsize, symsec_sh_link); 363 } 364 free(mrel0); 365 free(mloc0); 366 } 367