scripts/recordmcount.h

   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 }