Steven Rostedt | c28d507 | 2010-10-13 19:06:14 -0400 | [diff] [blame^] | 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 | } |