scripts/recordmcount.h

   1 /* SPDX-License-Identifier: GPL-2.0-only */
   2 /*
   3  * recordmcount.h
   4  *
   5  * This code was taken out of recordmcount.c written by
   6  * Copyright 2009 John F. Reiser <jreiser@BitWagon.com>.  All rights reserved.
   7  *
   8  * The original code had the same algorithms for both 32bit
   9  * and 64bit ELF files, but the code was duplicated to support
  10  * the difference in structures that were used. This
  11  * file creates a macro of everything that is different between
  12  * the 64 and 32 bit code, such that by including this header
  13  * twice we can create both sets of functions by including this
  14  * header once with RECORD_MCOUNT_64 undefined, and again with
  15  * it defined.
  16  *
  17  * This conversion to macros was done by:
  18  * Copyright 2010 Steven Rostedt <srostedt@redhat.com>, Red Hat Inc.
  19  */
  20 #undef append_func
  21 #undef is_fake_mcount
  22 #undef fn_is_fake_mcount
  23 #undef MIPS_is_fake_mcount
  24 #undef mcount_adjust
  25 #undef sift_rel_mcount
  26 #undef nop_mcount
  27 #undef find_secsym_ndx
  28 #undef __has_rel_mcount
  29 #undef has_rel_mcount
  30 #undef tot_relsize
  31 #undef get_mcountsym
  32 #undef find_symtab
  33 #undef get_shnum
  34 #undef set_shnum
  35 #undef get_shstrndx
  36 #undef get_symindex
  37 #undef get_sym_str_and_relp
  38 #undef do_func
  39 #undef Elf_Addr
  40 #undef Elf_Ehdr
  41 #undef Elf_Shdr
  42 #undef Elf_Rel
  43 #undef Elf_Rela
  44 #undef Elf_Sym
  45 #undef ELF_R_SYM
  46 #undef Elf_r_sym
  47 #undef ELF_R_INFO
  48 #undef Elf_r_info
  49 #undef ELF_ST_BIND
  50 #undef ELF_ST_TYPE
  51 #undef fn_ELF_R_SYM
  52 #undef fn_ELF_R_INFO
  53 #undef uint_t
  54 #undef _w
  55 #undef _align
  56 #undef _size
  57
  58 #ifdef RECORD_MCOUNT_64
  59 # define append_func            append64
  60 # define sift_rel_mcount        sift64_rel_mcount
  61 # define nop_mcount             nop_mcount_64
  62 # define find_secsym_ndx        find64_secsym_ndx
  63 # define __has_rel_mcount       __has64_rel_mcount
  64 # define has_rel_mcount         has64_rel_mcount
  65 # define tot_relsize            tot64_relsize
  66 # define find_symtab            find_symtab64
  67 # define get_shnum              get_shnum64
  68 # define set_shnum              set_shnum64
  69 # define get_shstrndx           get_shstrndx64
  70 # define get_symindex           get_symindex64
  71 # define get_sym_str_and_relp   get_sym_str_and_relp_64
  72 # define do_func                do64
  73 # define get_mcountsym          get_mcountsym_64
  74 # define is_fake_mcount         is_fake_mcount64
  75 # define fn_is_fake_mcount      fn_is_fake_mcount64
  76 # define MIPS_is_fake_mcount    MIPS64_is_fake_mcount
  77 # define mcount_adjust          mcount_adjust_64
  78 # define Elf_Addr               Elf64_Addr
  79 # define Elf_Ehdr               Elf64_Ehdr
  80 # define Elf_Shdr               Elf64_Shdr
  81 # define Elf_Rel                Elf64_Rel
  82 # define Elf_Rela               Elf64_Rela
  83 # define Elf_Sym                Elf64_Sym
  84 # define ELF_R_SYM              ELF64_R_SYM
  85 # define Elf_r_sym              Elf64_r_sym
  86 # define ELF_R_INFO             ELF64_R_INFO
  87 # define Elf_r_info             Elf64_r_info
  88 # define ELF_ST_BIND            ELF64_ST_BIND
  89 # define ELF_ST_TYPE            ELF64_ST_TYPE
  90 # define fn_ELF_R_SYM           fn_ELF64_R_SYM
  91 # define fn_ELF_R_INFO          fn_ELF64_R_INFO
  92 # define uint_t                 uint64_t
  93 # define _w                     w8
  94 # define _align                 7u
  95 # define _size                  8
  96 #else
  97 # define append_func            append32
  98 # define sift_rel_mcount        sift32_rel_mcount
  99 # define nop_mcount             nop_mcount_32
 100 # define find_secsym_ndx        find32_secsym_ndx
 101 # define __has_rel_mcount       __has32_rel_mcount
 102 # define has_rel_mcount         has32_rel_mcount
 103 # define tot_relsize            tot32_relsize
 104 # define find_symtab            find_symtab32
 105 # define get_shnum              get_shnum32
 106 # define set_shnum              set_shnum32
 107 # define get_shstrndx           get_shstrndx32
 108 # define get_symindex           get_symindex32
 109 # define get_sym_str_and_relp   get_sym_str_and_relp_32
 110 # define do_func                do32
 111 # define get_mcountsym          get_mcountsym_32
 112 # define is_fake_mcount         is_fake_mcount32
 113 # define fn_is_fake_mcount      fn_is_fake_mcount32
 114 # define MIPS_is_fake_mcount    MIPS32_is_fake_mcount
 115 # define mcount_adjust          mcount_adjust_32
 116 # define Elf_Addr               Elf32_Addr
 117 # define Elf_Ehdr               Elf32_Ehdr
 118 # define Elf_Shdr               Elf32_Shdr
 119 # define Elf_Rel                Elf32_Rel
 120 # define Elf_Rela               Elf32_Rela
 121 # define Elf_Sym                Elf32_Sym
 122 # define ELF_R_SYM              ELF32_R_SYM
 123 # define Elf_r_sym              Elf32_r_sym
 124 # define ELF_R_INFO             ELF32_R_INFO
 125 # define Elf_r_info             Elf32_r_info
 126 # define ELF_ST_BIND            ELF32_ST_BIND
 127 # define ELF_ST_TYPE            ELF32_ST_TYPE
 128 # define fn_ELF_R_SYM           fn_ELF32_R_SYM
 129 # define fn_ELF_R_INFO          fn_ELF32_R_INFO
 130 # define uint_t                 uint32_t
 131 # define _w                     w
 132 # define _align                 3u
 133 # define _size                  4
 134 #endif
 135
 136 /* Functions and pointers that do_file() may override for specific e_machine. */
 137 static int fn_is_fake_mcount(Elf_Rel const *rp)
 138 {
 139         return 0;
 140 }
 141 static int (*is_fake_mcount)(Elf_Rel const *rp) = fn_is_fake_mcount;
 142
 143 static uint_t fn_ELF_R_SYM(Elf_Rel const *rp)
 144 {
 145         return ELF_R_SYM(_w(rp->r_info));
 146 }
 147 static uint_t (*Elf_r_sym)(Elf_Rel const *rp) = fn_ELF_R_SYM;
 148
 149 static void fn_ELF_R_INFO(Elf_Rel *const rp, unsigned sym, unsigned type)
 150 {
 151         rp->r_info = _w(ELF_R_INFO(sym, type));
 152 }
 153 static void (*Elf_r_info)(Elf_Rel *const rp, unsigned sym, unsigned type) = fn_ELF_R_INFO;
 154
 155 static int mcount_adjust = 0;
 156
 157 /*
 158  * MIPS mcount long call has 2 _mcount symbols, only the position of the 1st
 159  * _mcount symbol is needed for dynamic function tracer, with it, to disable
 160  * tracing(ftrace_make_nop), the instruction in the position is replaced with
 161  * the "b label" instruction, to enable tracing(ftrace_make_call), replace the
 162  * instruction back. So, here, we set the 2nd one as fake and filter it.
 163  *
 164  * c:   3c030000        lui     v1,0x0          <-->    b       label
 165  *              c: R_MIPS_HI16  _mcount
 166  *              c: R_MIPS_NONE  *ABS*
 167  *              c: R_MIPS_NONE  *ABS*
 168  * 10:  64630000        daddiu  v1,v1,0
 169  *              10: R_MIPS_LO16 _mcount
 170  *              10: R_MIPS_NONE *ABS*
 171  *              10: R_MIPS_NONE *ABS*
 172  * 14:  03e0082d        move    at,ra
 173  * 18:  0060f809        jalr    v1
 174  * label:
 175  */
 176 #define MIPS_FAKEMCOUNT_OFFSET  4
 177
 178 static int MIPS_is_fake_mcount(Elf_Rel const *rp)
 179 {
 180         static Elf_Addr old_r_offset = ~(Elf_Addr)0;
 181         Elf_Addr current_r_offset = _w(rp->r_offset);
 182         int is_fake;
 183
 184         is_fake = (old_r_offset != ~(Elf_Addr)0) &&
 185                 (current_r_offset - old_r_offset == MIPS_FAKEMCOUNT_OFFSET);
 186         old_r_offset = current_r_offset;
 187
 188         return is_fake;
 189 }
 190
 191 static unsigned int get_symindex(Elf_Sym const *sym, Elf32_Word const *symtab,
 192                                  Elf32_Word const *symtab_shndx)
 193 {
 194         unsigned long offset;
 195         unsigned short shndx = w2(sym->st_shndx);
 196         int index;
 197
 198         if (shndx > SHN_UNDEF && shndx < SHN_LORESERVE)
 199                 return shndx;
 200
 201         if (shndx == SHN_XINDEX) {
 202                 offset = (unsigned long)sym - (unsigned long)symtab;
 203                 index = offset / sizeof(*sym);
 204
 205                 return w(symtab_shndx[index]);
 206         }
 207
 208         return 0;
 209 }
 210
 211 static unsigned int get_shnum(Elf_Ehdr const *ehdr, Elf_Shdr const *shdr0)
 212 {
 213         if (shdr0 && !ehdr->e_shnum)
 214                 return w(shdr0->sh_size);
 215
 216         return w2(ehdr->e_shnum);
 217 }
 218
 219 static void set_shnum(Elf_Ehdr *ehdr, Elf_Shdr *shdr0, unsigned int new_shnum)
 220 {
 221         if (new_shnum >= SHN_LORESERVE) {
 222                 ehdr->e_shnum = 0;
 223                 shdr0->sh_size = w(new_shnum);
 224         } else
 225                 ehdr->e_shnum = w2(new_shnum);
 226 }
 227
 228 static int get_shstrndx(Elf_Ehdr const *ehdr, Elf_Shdr const *shdr0)
 229 {
 230         if (ehdr->e_shstrndx != SHN_XINDEX)
 231                 return w2(ehdr->e_shstrndx);
 232
 233         return w(shdr0->sh_link);
 234 }
 235
 236 static void find_symtab(Elf_Ehdr *const ehdr, Elf_Shdr const *shdr0,
 237                         unsigned const nhdr, Elf32_Word **symtab,
 238                         Elf32_Word **symtab_shndx)
 239 {
 240         Elf_Shdr const *relhdr;
 241         unsigned k;
 242
 243         *symtab = NULL;
 244         *symtab_shndx = NULL;
 245
 246         for (relhdr = shdr0, k = nhdr; k; --k, ++relhdr) {
 247                 if (relhdr->sh_type == SHT_SYMTAB)
 248                         *symtab = (void *)ehdr + relhdr->sh_offset;
 249                 else if (relhdr->sh_type == SHT_SYMTAB_SHNDX)
 250                         *symtab_shndx = (void *)ehdr + relhdr->sh_offset;
 251
 252                 if (*symtab && *symtab_shndx)
 253                         break;
 254         }
 255 }
 256
 257 /* Append the new shstrtab, Elf_Shdr[], __mcount_loc and its relocations. */
 258 static int append_func(Elf_Ehdr *const ehdr,
 259                         Elf_Shdr *const shstr,
 260                         uint_t const *const mloc0,
 261                         uint_t const *const mlocp,
 262                         Elf_Rel const *const mrel0,
 263                         Elf_Rel const *const mrelp,
 264                         unsigned int const rel_entsize,
 265                         unsigned int const symsec_sh_link)
 266 {
 267         /* Begin constructing output file */
 268         Elf_Shdr mcsec;
 269         char const *mc_name = (sizeof(Elf_Rela) == rel_entsize)
 270                 ? ".rela__mcount_loc"
 271                 :  ".rel__mcount_loc";
 272         uint_t const old_shoff = _w(ehdr->e_shoff);
 273         uint_t const old_shstr_sh_size   = _w(shstr->sh_size);
 274         uint_t const old_shstr_sh_offset = _w(shstr->sh_offset);
 275         Elf_Shdr *const shdr0 = (Elf_Shdr *)(old_shoff + (void *)ehdr);
 276         unsigned int const old_shnum = get_shnum(ehdr, shdr0);
 277         unsigned int const new_shnum = 2 + old_shnum; /* {.rel,}__mcount_loc */
 278         uint_t t = 1 + strlen(mc_name) + _w(shstr->sh_size);
 279         uint_t new_e_shoff;
 280
 281         shstr->sh_size = _w(t);
 282         shstr->sh_offset = _w(sb.st_size);
 283         t += sb.st_size;
 284         t += (_align & -t);  /* word-byte align */
 285         new_e_shoff = t;
 286
 287         set_shnum(ehdr, shdr0, new_shnum);
 288
 289         /* body for new shstrtab */
 290         if (ulseek(sb.st_size, SEEK_SET) < 0)
 291                 return -1;
 292         if (uwrite(old_shstr_sh_offset + (void *)ehdr, old_shstr_sh_size) < 0)
 293                 return -1;
 294         if (uwrite(mc_name, 1 + strlen(mc_name)) < 0)
 295                 return -1;
 296
 297         /* old(modified) Elf_Shdr table, word-byte aligned */
 298         if (ulseek(t, SEEK_SET) < 0)
 299                 return -1;
 300         t += sizeof(Elf_Shdr) * old_shnum;
 301         if (uwrite(old_shoff + (void *)ehdr,
 302                sizeof(Elf_Shdr) * old_shnum) < 0)
 303                 return -1;
 304
 305         /* new sections __mcount_loc and .rel__mcount_loc */
 306         t += 2*sizeof(mcsec);
 307         mcsec.sh_name = w((sizeof(Elf_Rela) == rel_entsize) + strlen(".rel")
 308                 + old_shstr_sh_size);
 309         mcsec.sh_type = w(SHT_PROGBITS);
 310         mcsec.sh_flags = _w(SHF_ALLOC);
 311         mcsec.sh_addr = 0;
 312         mcsec.sh_offset = _w(t);
 313         mcsec.sh_size = _w((void *)mlocp - (void *)mloc0);
 314         mcsec.sh_link = 0;
 315         mcsec.sh_info = 0;
 316         mcsec.sh_addralign = _w(_size);
 317         mcsec.sh_entsize = _w(_size);
 318         if (uwrite(&mcsec, sizeof(mcsec)) < 0)
 319                 return -1;
 320
 321         mcsec.sh_name = w(old_shstr_sh_size);
 322         mcsec.sh_type = (sizeof(Elf_Rela) == rel_entsize)
 323                 ? w(SHT_RELA)
 324                 : w(SHT_REL);
 325         mcsec.sh_flags = 0;
 326         mcsec.sh_addr = 0;
 327         mcsec.sh_offset = _w((void *)mlocp - (void *)mloc0 + t);
 328         mcsec.sh_size   = _w((void *)mrelp - (void *)mrel0);
 329         mcsec.sh_link = w(symsec_sh_link);
 330         mcsec.sh_info = w(old_shnum);
 331         mcsec.sh_addralign = _w(_size);
 332         mcsec.sh_entsize = _w(rel_entsize);
 333
 334         if (uwrite(&mcsec, sizeof(mcsec)) < 0)
 335                 return -1;
 336
 337         if (uwrite(mloc0, (void *)mlocp - (void *)mloc0) < 0)
 338                 return -1;
 339         if (uwrite(mrel0, (void *)mrelp - (void *)mrel0) < 0)
 340                 return -1;
 341
 342         ehdr->e_shoff = _w(new_e_shoff);
 343         if (ulseek(0, SEEK_SET) < 0)
 344                 return -1;
 345         if (uwrite(ehdr, sizeof(*ehdr)) < 0)
 346                 return -1;
 347         return 0;
 348 }
 349
 350 static unsigned get_mcountsym(Elf_Sym const *const sym0,
 351                               Elf_Rel const *relp,
 352                               char const *const str0)
 353 {
 354         unsigned mcountsym = 0;
 355
 356         Elf_Sym const *const symp =
 357                 &sym0[Elf_r_sym(relp)];
 358         char const *symname = &str0[w(symp->st_name)];
 359         char const *mcount = gpfx == '_' ? "_mcount" : "mcount";
 360         char const *fentry = "__fentry__";
 361
 362         if (symname[0] == '.')
 363                 ++symname;  /* ppc64 hack */
 364         if (strcmp(mcount, symname) == 0 ||
 365             (altmcount && strcmp(altmcount, symname) == 0) ||
 366             (strcmp(fentry, symname) == 0))
 367                 mcountsym = Elf_r_sym(relp);
 368
 369         return mcountsym;
 370 }
 371
 372 static void get_sym_str_and_relp(Elf_Shdr const *const relhdr,
 373                                  Elf_Ehdr const *const ehdr,
 374                                  Elf_Sym const **sym0,
 375                                  char const **str0,
 376                                  Elf_Rel const **relp)
 377 {
 378         Elf_Shdr *const shdr0 = (Elf_Shdr *)(_w(ehdr->e_shoff)
 379                 + (void *)ehdr);
 380         unsigned const symsec_sh_link = w(relhdr->sh_link);
 381         Elf_Shdr const *const symsec = &shdr0[symsec_sh_link];
 382         Elf_Shdr const *const strsec = &shdr0[w(symsec->sh_link)];
 383         Elf_Rel const *const rel0 = (Elf_Rel const *)(_w(relhdr->sh_offset)
 384                 + (void *)ehdr);
 385
 386         *sym0 = (Elf_Sym const *)(_w(symsec->sh_offset)
 387                                   + (void *)ehdr);
 388
 389         *str0 = (char const *)(_w(strsec->sh_offset)
 390                                + (void *)ehdr);
 391
 392         *relp = rel0;
 393 }
 394
 395 /*
 396  * Look at the relocations in order to find the calls to mcount.
 397  * Accumulate the section offsets that are found, and their relocation info,
 398  * onto the end of the existing arrays.
 399  */
 400 static uint_t *sift_rel_mcount(uint_t *mlocp,
 401                                unsigned const offbase,
 402                                Elf_Rel **const mrelpp,
 403                                Elf_Shdr const *const relhdr,
 404                                Elf_Ehdr const *const ehdr,
 405                                unsigned const recsym,
 406                                uint_t const recval,
 407                                unsigned const reltype)
 408 {
 409         uint_t *const mloc0 = mlocp;
 410         Elf_Rel *mrelp = *mrelpp;
 411         Elf_Sym const *sym0;
 412         char const *str0;
 413         Elf_Rel const *relp;
 414         unsigned rel_entsize = _w(relhdr->sh_entsize);
 415         unsigned const nrel = _w(relhdr->sh_size) / rel_entsize;
 416         unsigned mcountsym = 0;
 417         unsigned t;
 418
 419         get_sym_str_and_relp(relhdr, ehdr, &sym0, &str0, &relp);
 420
 421         for (t = nrel; t; --t) {
 422                 if (!mcountsym)
 423                         mcountsym = get_mcountsym(sym0, relp, str0);
 424
 425                 if (mcountsym && mcountsym == Elf_r_sym(relp) &&
 426                                 !is_fake_mcount(relp)) {
 427                         uint_t const addend =
 428                                 _w(_w(relp->r_offset) - recval + mcount_adjust);
 429                         mrelp->r_offset = _w(offbase
 430                                 + ((void *)mlocp - (void *)mloc0));
 431                         Elf_r_info(mrelp, recsym, reltype);
 432                         if (rel_entsize == sizeof(Elf_Rela)) {
 433                                 ((Elf_Rela *)mrelp)->r_addend = addend;
 434                                 *mlocp++ = 0;
 435                         } else
 436                                 *mlocp++ = addend;
 437
 438                         mrelp = (Elf_Rel *)(rel_entsize + (void *)mrelp);
 439                 }
 440                 relp = (Elf_Rel const *)(rel_entsize + (void *)relp);
 441         }
 442         *mrelpp = mrelp;
 443         return mlocp;
 444 }
 445
 446 /*
 447  * Read the relocation table again, but this time its called on sections
 448  * that are not going to be traced. The mcount calls here will be converted
 449  * into nops.
 450  */
 451 static int nop_mcount(Elf_Shdr const *const relhdr,
 452                       Elf_Ehdr const *const ehdr,
 453                       const char *const txtname)
 454 {
 455         Elf_Shdr *const shdr0 = (Elf_Shdr *)(_w(ehdr->e_shoff)
 456                 + (void *)ehdr);
 457         Elf_Sym const *sym0;
 458         char const *str0;
 459         Elf_Rel const *relp;
 460         Elf_Shdr const *const shdr = &shdr0[w(relhdr->sh_info)];
 461         unsigned rel_entsize = _w(relhdr->sh_entsize);
 462         unsigned const nrel = _w(relhdr->sh_size) / rel_entsize;
 463         unsigned mcountsym = 0;
 464         unsigned t;
 465         int once = 0;
 466
 467         get_sym_str_and_relp(relhdr, ehdr, &sym0, &str0, &relp);
 468
 469         for (t = nrel; t; --t) {
 470                 int ret = -1;
 471
 472                 if (!mcountsym)
 473                         mcountsym = get_mcountsym(sym0, relp, str0);
 474
 475                 if (mcountsym == Elf_r_sym(relp) && !is_fake_mcount(relp)) {
 476                         if (make_nop)
 477                                 ret = make_nop((void *)ehdr, _w(shdr->sh_offset) + _w(relp->r_offset));
 478                         if (warn_on_notrace_sect && !once) {
 479                                 printf("Section %s has mcount callers being ignored\n",
 480                                        txtname);
 481                                 once = 1;
 482                                 /* just warn? */
 483                                 if (!make_nop)
 484                                         return 0;
 485                         }
 486                 }
 487
 488                 /*
 489                  * If we successfully removed the mcount, mark the relocation
 490                  * as a nop (don't do anything with it).
 491                  */
 492                 if (!ret) {
 493                         Elf_Rel rel;
 494                         rel = *(Elf_Rel *)relp;
 495                         Elf_r_info(&rel, Elf_r_sym(relp), rel_type_nop);
 496                         if (ulseek((void *)relp - (void *)ehdr, SEEK_SET) < 0)
 497                                 return -1;
 498                         if (uwrite(&rel, sizeof(rel)) < 0)
 499                                 return -1;
 500                 }
 501                 relp = (Elf_Rel const *)(rel_entsize + (void *)relp);
 502         }
 503         return 0;
 504 }
 505
 506 /*
 507  * Find a symbol in the given section, to be used as the base for relocating
 508  * the table of offsets of calls to mcount.  A local or global symbol suffices,
 509  * but avoid a Weak symbol because it may be overridden; the change in value
 510  * would invalidate the relocations of the offsets of the calls to mcount.
 511  * Often the found symbol will be the unnamed local symbol generated by
 512  * GNU 'as' for the start of each section.  For example:
 513  *    Num:    Value  Size Type    Bind   Vis      Ndx Name
 514  *      2: 00000000     0 SECTION LOCAL  DEFAULT    1
 515  */
 516 static int find_secsym_ndx(unsigned const txtndx,
 517                                 char const *const txtname,
 518                                 uint_t *const recvalp,
 519                                 unsigned int *sym_index,
 520                                 Elf_Shdr const *const symhdr,
 521                                 Elf32_Word const *symtab,
 522                                 Elf32_Word const *symtab_shndx,
 523                                 Elf_Ehdr const *const ehdr)
 524 {
 525         Elf_Sym const *const sym0 = (Elf_Sym const *)(_w(symhdr->sh_offset)
 526                 + (void *)ehdr);
 527         unsigned const nsym = _w(symhdr->sh_size) / _w(symhdr->sh_entsize);
 528         Elf_Sym const *symp;
 529         unsigned t;
 530
 531         for (symp = sym0, t = nsym; t; --t, ++symp) {
 532                 unsigned int const st_bind = ELF_ST_BIND(symp->st_info);
 533
 534                 if (txtndx == get_symindex(symp, symtab, symtab_shndx)
 535                         /* avoid STB_WEAK */
 536                     && (STB_LOCAL == st_bind || STB_GLOBAL == st_bind)) {
 537                         /* function symbols on ARM have quirks, avoid them */
 538                         if (w2(ehdr->e_machine) == EM_ARM
 539                             && ELF_ST_TYPE(symp->st_info) == STT_FUNC)
 540                                 continue;
 541
 542                         *recvalp = _w(symp->st_value);
 543                         *sym_index = symp - sym0;
 544                         return 0;
 545                 }
 546         }
 547         fprintf(stderr, "Cannot find symbol for section %u: %s.\n",
 548                 txtndx, txtname);
 549         return -1;
 550 }
 551
 552 /* Evade ISO C restriction: no declaration after statement in has_rel_mcount. */
 553 static char const * __has_rel_mcount(Elf_Shdr const *const relhdr, /* reltype */
 554                                      Elf_Shdr const *const shdr0,
 555                                      char const *const shstrtab,
 556                                      char const *const fname)
 557 {
 558         /* .sh_info depends on .sh_type == SHT_REL[,A] */
 559         Elf_Shdr const *const txthdr = &shdr0[w(relhdr->sh_info)];
 560         char const *const txtname = &shstrtab[w(txthdr->sh_name)];
 561
 562         if (strcmp("__mcount_loc", txtname) == 0) {
 563                 fprintf(stderr, "warning: __mcount_loc already exists: %s\n",
 564                         fname);
 565                 return already_has_rel_mcount;
 566         }
 567         if (w(txthdr->sh_type) != SHT_PROGBITS ||
 568             !(_w(txthdr->sh_flags) & SHF_EXECINSTR))
 569                 return NULL;
 570         return txtname;
 571 }
 572
 573 static char const *has_rel_mcount(Elf_Shdr const *const relhdr,
 574                                   Elf_Shdr const *const shdr0,
 575                                   char const *const shstrtab,
 576                                   char const *const fname)
 577 {
 578         if (w(relhdr->sh_type) != SHT_REL && w(relhdr->sh_type) != SHT_RELA)
 579                 return NULL;
 580         return __has_rel_mcount(relhdr, shdr0, shstrtab, fname);
 581 }
 582
 583
 584 static unsigned tot_relsize(Elf_Shdr const *const shdr0,
 585                             unsigned nhdr,
 586                             const char *const shstrtab,
 587                             const char *const fname)
 588 {
 589         unsigned totrelsz = 0;
 590         Elf_Shdr const *shdrp = shdr0;
 591         char const *txtname;
 592
 593         for (; nhdr; --nhdr, ++shdrp) {
 594                 txtname = has_rel_mcount(shdrp, shdr0, shstrtab, fname);
 595                 if (txtname == already_has_rel_mcount) {
 596                         totrelsz = 0;
 597                         break;
 598                 }
 599                 if (txtname && is_mcounted_section_name(txtname))
 600                         totrelsz += _w(shdrp->sh_size);
 601         }
 602         return totrelsz;
 603 }
 604
 605 /* Overall supervision for Elf32 ET_REL file. */
 606 static int do_func(Elf_Ehdr *const ehdr, char const *const fname,
 607                    unsigned const reltype)
 608 {
 609         Elf_Shdr *const shdr0 = (Elf_Shdr *)(_w(ehdr->e_shoff)
 610                 + (void *)ehdr);
 611         unsigned const nhdr = get_shnum(ehdr, shdr0);
 612         Elf_Shdr *const shstr = &shdr0[get_shstrndx(ehdr, shdr0)];
 613         char const *const shstrtab = (char const *)(_w(shstr->sh_offset)
 614                 + (void *)ehdr);
 615
 616         Elf_Shdr const *relhdr;
 617         unsigned k;
 618
 619         Elf32_Word *symtab;
 620         Elf32_Word *symtab_shndx;
 621
 622         /* Upper bound on space: assume all relevant relocs are for mcount. */
 623         unsigned       totrelsz;
 624
 625         Elf_Rel *      mrel0;
 626         Elf_Rel *      mrelp;
 627
 628         uint_t *      mloc0;
 629         uint_t *      mlocp;
 630
 631         unsigned rel_entsize = 0;
 632         unsigned symsec_sh_link = 0;
 633
 634         int result = 0;
 635
 636         totrelsz = tot_relsize(shdr0, nhdr, shstrtab, fname);
 637         if (totrelsz == 0)
 638                 return 0;
 639         mrel0 = umalloc(totrelsz);
 640         mrelp = mrel0;
 641         if (!mrel0)
 642                 return -1;
 643
 644         /* 2*sizeof(address) <= sizeof(Elf_Rel) */
 645         mloc0 = umalloc(totrelsz>>1);
 646         mlocp = mloc0;
 647         if (!mloc0) {
 648                 free(mrel0);
 649                 return -1;
 650         }
 651
 652         find_symtab(ehdr, shdr0, nhdr, &symtab, &symtab_shndx);
 653
 654         for (relhdr = shdr0, k = nhdr; k; --k, ++relhdr) {
 655                 char const *const txtname = has_rel_mcount(relhdr, shdr0,
 656                         shstrtab, fname);
 657                 if (txtname == already_has_rel_mcount) {
 658                         result = 0;
 659                         file_updated = 0;
 660                         goto out; /* Nothing to be done; don't append! */
 661                 }
 662                 if (txtname && is_mcounted_section_name(txtname)) {
 663                         unsigned int recsym;
 664                         uint_t recval = 0;
 665
 666                         symsec_sh_link = w(relhdr->sh_link);
 667                         result = find_secsym_ndx(w(relhdr->sh_info), txtname,
 668                                                 &recval, &recsym,
 669                                                 &shdr0[symsec_sh_link],
 670                                                 symtab, symtab_shndx,
 671                                                 ehdr);
 672                         if (result)
 673                                 goto out;
 674
 675                         rel_entsize = _w(relhdr->sh_entsize);
 676                         mlocp = sift_rel_mcount(mlocp,
 677                                 (void *)mlocp - (void *)mloc0, &mrelp,
 678                                 relhdr, ehdr, recsym, recval, reltype);
 679                 } else if (txtname && (warn_on_notrace_sect || make_nop)) {
 680                         /*
 681                          * This section is ignored by ftrace, but still
 682                          * has mcount calls. Convert them to nops now.
 683                          */
 684                         if (nop_mcount(relhdr, ehdr, txtname) < 0) {
 685                                 result = -1;
 686                                 goto out;
 687                         }
 688                 }
 689         }
 690         if (!result && mloc0 != mlocp)
 691                 result = append_func(ehdr, shstr, mloc0, mlocp, mrel0, mrelp,
 692                                      rel_entsize, symsec_sh_link);
 693 out:
 694         free(mrel0);
 695         free(mloc0);
 696         return result;
 697 }