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 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 }