linux/scripts/recordmcount.h
<<
>>
Prefs
   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. */
 137static int fn_is_fake_mcount(Elf_Rel const *rp)
 138{
 139        return 0;
 140}
 141static int (*is_fake_mcount)(Elf_Rel const *rp) = fn_is_fake_mcount;
 142
 143static uint_t fn_ELF_R_SYM(Elf_Rel const *rp)
 144{
 145        return ELF_R_SYM(_w(rp->r_info));
 146}
 147static uint_t (*Elf_r_sym)(Elf_Rel const *rp) = fn_ELF_R_SYM;
 148
 149static 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}
 153static void (*Elf_r_info)(Elf_Rel *const rp, unsigned sym, unsigned type) = fn_ELF_R_INFO;
 154
 155static 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
 178static 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
 191static unsigned int get_symindex(Elf_Sym const *sym, Elf32_Word const *symtab,
 192                                 Elf32_Word const *symtab_shndx)
 193{
 194        unsigned long offset;
 195        int index;
 196
 197        if (sym->st_shndx != SHN_XINDEX)
 198                return w2(sym->st_shndx);
 199
 200        offset = (unsigned long)sym - (unsigned long)symtab;
 201        index = offset / sizeof(*sym);
 202
 203        return w(symtab_shndx[index]);
 204}
 205
 206static unsigned int get_shnum(Elf_Ehdr const *ehdr, Elf_Shdr const *shdr0)
 207{
 208        if (shdr0 && !ehdr->e_shnum)
 209                return w(shdr0->sh_size);
 210
 211        return w2(ehdr->e_shnum);
 212}
 213
 214static void set_shnum(Elf_Ehdr *ehdr, Elf_Shdr *shdr0, unsigned int new_shnum)
 215{
 216        if (new_shnum >= SHN_LORESERVE) {
 217                ehdr->e_shnum = 0;
 218                shdr0->sh_size = w(new_shnum);
 219        } else
 220                ehdr->e_shnum = w2(new_shnum);
 221}
 222
 223static int get_shstrndx(Elf_Ehdr const *ehdr, Elf_Shdr const *shdr0)
 224{
 225        if (ehdr->e_shstrndx != SHN_XINDEX)
 226                return w2(ehdr->e_shstrndx);
 227
 228        return w(shdr0->sh_link);
 229}
 230
 231static void find_symtab(Elf_Ehdr *const ehdr, Elf_Shdr const *shdr0,
 232                        unsigned const nhdr, Elf32_Word **symtab,
 233                        Elf32_Word **symtab_shndx)
 234{
 235        Elf_Shdr const *relhdr;
 236        unsigned k;
 237
 238        *symtab = NULL;
 239        *symtab_shndx = NULL;
 240
 241        for (relhdr = shdr0, k = nhdr; k; --k, ++relhdr) {
 242                if (relhdr->sh_type == SHT_SYMTAB)
 243                        *symtab = (void *)ehdr + relhdr->sh_offset;
 244                else if (relhdr->sh_type == SHT_SYMTAB_SHNDX)
 245                        *symtab_shndx = (void *)ehdr + relhdr->sh_offset;
 246
 247                if (*symtab && *symtab_shndx)
 248                        break;
 249        }
 250}
 251
 252/* Append the new shstrtab, Elf_Shdr[], __mcount_loc and its relocations. */
 253static int append_func(Elf_Ehdr *const ehdr,
 254                        Elf_Shdr *const shstr,
 255                        uint_t const *const mloc0,
 256                        uint_t const *const mlocp,
 257                        Elf_Rel const *const mrel0,
 258                        Elf_Rel const *const mrelp,
 259                        unsigned int const rel_entsize,
 260                        unsigned int const symsec_sh_link)
 261{
 262        /* Begin constructing output file */
 263        Elf_Shdr mcsec;
 264        char const *mc_name = (sizeof(Elf_Rela) == rel_entsize)
 265                ? ".rela__mcount_loc"
 266                :  ".rel__mcount_loc";
 267        uint_t const old_shoff = _w(ehdr->e_shoff);
 268        uint_t const old_shstr_sh_size   = _w(shstr->sh_size);
 269        uint_t const old_shstr_sh_offset = _w(shstr->sh_offset);
 270        Elf_Shdr *const shdr0 = (Elf_Shdr *)(old_shoff + (void *)ehdr);
 271        unsigned int const old_shnum = get_shnum(ehdr, shdr0);
 272        unsigned int const new_shnum = 2 + old_shnum; /* {.rel,}__mcount_loc */
 273        uint_t t = 1 + strlen(mc_name) + _w(shstr->sh_size);
 274        uint_t new_e_shoff;
 275
 276        shstr->sh_size = _w(t);
 277        shstr->sh_offset = _w(sb.st_size);
 278        t += sb.st_size;
 279        t += (_align & -t);  /* word-byte align */
 280        new_e_shoff = t;
 281
 282        set_shnum(ehdr, shdr0, new_shnum);
 283
 284        /* body for new shstrtab */
 285        if (ulseek(sb.st_size, SEEK_SET) < 0)
 286                return -1;
 287        if (uwrite(old_shstr_sh_offset + (void *)ehdr, old_shstr_sh_size) < 0)
 288                return -1;
 289        if (uwrite(mc_name, 1 + strlen(mc_name)) < 0)
 290                return -1;
 291
 292        /* old(modified) Elf_Shdr table, word-byte aligned */
 293        if (ulseek(t, SEEK_SET) < 0)
 294                return -1;
 295        t += sizeof(Elf_Shdr) * old_shnum;
 296        if (uwrite(old_shoff + (void *)ehdr,
 297               sizeof(Elf_Shdr) * old_shnum) < 0)
 298                return -1;
 299
 300        /* new sections __mcount_loc and .rel__mcount_loc */
 301        t += 2*sizeof(mcsec);
 302        mcsec.sh_name = w((sizeof(Elf_Rela) == rel_entsize) + strlen(".rel")
 303                + old_shstr_sh_size);
 304        mcsec.sh_type = w(SHT_PROGBITS);
 305        mcsec.sh_flags = _w(SHF_ALLOC);
 306        mcsec.sh_addr = 0;
 307        mcsec.sh_offset = _w(t);
 308        mcsec.sh_size = _w((void *)mlocp - (void *)mloc0);
 309        mcsec.sh_link = 0;
 310        mcsec.sh_info = 0;
 311        mcsec.sh_addralign = _w(_size);
 312        mcsec.sh_entsize = _w(_size);
 313        if (uwrite(&mcsec, sizeof(mcsec)) < 0)
 314                return -1;
 315
 316        mcsec.sh_name = w(old_shstr_sh_size);
 317        mcsec.sh_type = (sizeof(Elf_Rela) == rel_entsize)
 318                ? w(SHT_RELA)
 319                : w(SHT_REL);
 320        mcsec.sh_flags = 0;
 321        mcsec.sh_addr = 0;
 322        mcsec.sh_offset = _w((void *)mlocp - (void *)mloc0 + t);
 323        mcsec.sh_size   = _w((void *)mrelp - (void *)mrel0);
 324        mcsec.sh_link = w(symsec_sh_link);
 325        mcsec.sh_info = w(old_shnum);
 326        mcsec.sh_addralign = _w(_size);
 327        mcsec.sh_entsize = _w(rel_entsize);
 328
 329        if (uwrite(&mcsec, sizeof(mcsec)) < 0)
 330                return -1;
 331
 332        if (uwrite(mloc0, (void *)mlocp - (void *)mloc0) < 0)
 333                return -1;
 334        if (uwrite(mrel0, (void *)mrelp - (void *)mrel0) < 0)
 335                return -1;
 336
 337        ehdr->e_shoff = _w(new_e_shoff);
 338        if (ulseek(0, SEEK_SET) < 0)
 339                return -1;
 340        if (uwrite(ehdr, sizeof(*ehdr)) < 0)
 341                return -1;
 342        return 0;
 343}
 344
 345static unsigned get_mcountsym(Elf_Sym const *const sym0,
 346                              Elf_Rel const *relp,
 347                              char const *const str0)
 348{
 349        unsigned mcountsym = 0;
 350
 351        Elf_Sym const *const symp =
 352                &sym0[Elf_r_sym(relp)];
 353        char const *symname = &str0[w(symp->st_name)];
 354        char const *mcount = gpfx == '_' ? "_mcount" : "mcount";
 355        char const *fentry = "__fentry__";
 356
 357        if (symname[0] == '.')
 358                ++symname;  /* ppc64 hack */
 359        if (strcmp(mcount, symname) == 0 ||
 360            (altmcount && strcmp(altmcount, symname) == 0) ||
 361            (strcmp(fentry, symname) == 0))
 362                mcountsym = Elf_r_sym(relp);
 363
 364        return mcountsym;
 365}
 366
 367static void get_sym_str_and_relp(Elf_Shdr const *const relhdr,
 368                                 Elf_Ehdr const *const ehdr,
 369                                 Elf_Sym const **sym0,
 370                                 char const **str0,
 371                                 Elf_Rel const **relp)
 372{
 373        Elf_Shdr *const shdr0 = (Elf_Shdr *)(_w(ehdr->e_shoff)
 374                + (void *)ehdr);
 375        unsigned const symsec_sh_link = w(relhdr->sh_link);
 376        Elf_Shdr const *const symsec = &shdr0[symsec_sh_link];
 377        Elf_Shdr const *const strsec = &shdr0[w(symsec->sh_link)];
 378        Elf_Rel const *const rel0 = (Elf_Rel const *)(_w(relhdr->sh_offset)
 379                + (void *)ehdr);
 380
 381        *sym0 = (Elf_Sym const *)(_w(symsec->sh_offset)
 382                                  + (void *)ehdr);
 383
 384        *str0 = (char const *)(_w(strsec->sh_offset)
 385                               + (void *)ehdr);
 386
 387        *relp = rel0;
 388}
 389
 390/*
 391 * Look at the relocations in order to find the calls to mcount.
 392 * Accumulate the section offsets that are found, and their relocation info,
 393 * onto the end of the existing arrays.
 394 */
 395static uint_t *sift_rel_mcount(uint_t *mlocp,
 396                               unsigned const offbase,
 397                               Elf_Rel **const mrelpp,
 398                               Elf_Shdr const *const relhdr,
 399                               Elf_Ehdr const *const ehdr,
 400                               unsigned const recsym,
 401                               uint_t const recval,
 402                               unsigned const reltype)
 403{
 404        uint_t *const mloc0 = mlocp;
 405        Elf_Rel *mrelp = *mrelpp;
 406        Elf_Sym const *sym0;
 407        char const *str0;
 408        Elf_Rel const *relp;
 409        unsigned rel_entsize = _w(relhdr->sh_entsize);
 410        unsigned const nrel = _w(relhdr->sh_size) / rel_entsize;
 411        unsigned mcountsym = 0;
 412        unsigned t;
 413
 414        get_sym_str_and_relp(relhdr, ehdr, &sym0, &str0, &relp);
 415
 416        for (t = nrel; t; --t) {
 417                if (!mcountsym)
 418                        mcountsym = get_mcountsym(sym0, relp, str0);
 419
 420                if (mcountsym && mcountsym == Elf_r_sym(relp) &&
 421                                !is_fake_mcount(relp)) {
 422                        uint_t const addend =
 423                                _w(_w(relp->r_offset) - recval + mcount_adjust);
 424                        mrelp->r_offset = _w(offbase
 425                                + ((void *)mlocp - (void *)mloc0));
 426                        Elf_r_info(mrelp, recsym, reltype);
 427                        if (rel_entsize == sizeof(Elf_Rela)) {
 428                                ((Elf_Rela *)mrelp)->r_addend = addend;
 429                                *mlocp++ = 0;
 430                        } else
 431                                *mlocp++ = addend;
 432
 433                        mrelp = (Elf_Rel *)(rel_entsize + (void *)mrelp);
 434                }
 435                relp = (Elf_Rel const *)(rel_entsize + (void *)relp);
 436        }
 437        *mrelpp = mrelp;
 438        return mlocp;
 439}
 440
 441/*
 442 * Read the relocation table again, but this time its called on sections
 443 * that are not going to be traced. The mcount calls here will be converted
 444 * into nops.
 445 */
 446static int nop_mcount(Elf_Shdr const *const relhdr,
 447                      Elf_Ehdr const *const ehdr,
 448                      const char *const txtname)
 449{
 450        Elf_Shdr *const shdr0 = (Elf_Shdr *)(_w(ehdr->e_shoff)
 451                + (void *)ehdr);
 452        Elf_Sym const *sym0;
 453        char const *str0;
 454        Elf_Rel const *relp;
 455        Elf_Shdr const *const shdr = &shdr0[w(relhdr->sh_info)];
 456        unsigned rel_entsize = _w(relhdr->sh_entsize);
 457        unsigned const nrel = _w(relhdr->sh_size) / rel_entsize;
 458        unsigned mcountsym = 0;
 459        unsigned t;
 460        int once = 0;
 461
 462        get_sym_str_and_relp(relhdr, ehdr, &sym0, &str0, &relp);
 463
 464        for (t = nrel; t; --t) {
 465                int ret = -1;
 466
 467                if (!mcountsym)
 468                        mcountsym = get_mcountsym(sym0, relp, str0);
 469
 470                if (mcountsym == Elf_r_sym(relp) && !is_fake_mcount(relp)) {
 471                        if (make_nop)
 472                                ret = make_nop((void *)ehdr, _w(shdr->sh_offset) + _w(relp->r_offset));
 473                        if (warn_on_notrace_sect && !once) {
 474                                printf("Section %s has mcount callers being ignored\n",
 475                                       txtname);
 476                                once = 1;
 477                                /* just warn? */
 478                                if (!make_nop)
 479                                        return 0;
 480                        }
 481                }
 482
 483                /*
 484                 * If we successfully removed the mcount, mark the relocation
 485                 * as a nop (don't do anything with it).
 486                 */
 487                if (!ret) {
 488                        Elf_Rel rel;
 489                        rel = *(Elf_Rel *)relp;
 490                        Elf_r_info(&rel, Elf_r_sym(relp), rel_type_nop);
 491                        if (ulseek((void *)relp - (void *)ehdr, SEEK_SET) < 0)
 492                                return -1;
 493                        if (uwrite(&rel, sizeof(rel)) < 0)
 494                                return -1;
 495                }
 496                relp = (Elf_Rel const *)(rel_entsize + (void *)relp);
 497        }
 498        return 0;
 499}
 500
 501/*
 502 * Find a symbol in the given section, to be used as the base for relocating
 503 * the table of offsets of calls to mcount.  A local or global symbol suffices,
 504 * but avoid a Weak symbol because it may be overridden; the change in value
 505 * would invalidate the relocations of the offsets of the calls to mcount.
 506 * Often the found symbol will be the unnamed local symbol generated by
 507 * GNU 'as' for the start of each section.  For example:
 508 *    Num:    Value  Size Type    Bind   Vis      Ndx Name
 509 *      2: 00000000     0 SECTION LOCAL  DEFAULT    1
 510 */
 511static int find_secsym_ndx(unsigned const txtndx,
 512                                char const *const txtname,
 513                                uint_t *const recvalp,
 514                                unsigned int *sym_index,
 515                                Elf_Shdr const *const symhdr,
 516                                Elf32_Word const *symtab,
 517                                Elf32_Word const *symtab_shndx,
 518                                Elf_Ehdr const *const ehdr)
 519{
 520        Elf_Sym const *const sym0 = (Elf_Sym const *)(_w(symhdr->sh_offset)
 521                + (void *)ehdr);
 522        unsigned const nsym = _w(symhdr->sh_size) / _w(symhdr->sh_entsize);
 523        Elf_Sym const *symp;
 524        unsigned t;
 525
 526        for (symp = sym0, t = nsym; t; --t, ++symp) {
 527                unsigned int const st_bind = ELF_ST_BIND(symp->st_info);
 528
 529                if (txtndx == get_symindex(symp, symtab, symtab_shndx)
 530                        /* avoid STB_WEAK */
 531                    && (STB_LOCAL == st_bind || STB_GLOBAL == st_bind)) {
 532                        /* function symbols on ARM have quirks, avoid them */
 533                        if (w2(ehdr->e_machine) == EM_ARM
 534                            && ELF_ST_TYPE(symp->st_info) == STT_FUNC)
 535                                continue;
 536
 537                        *recvalp = _w(symp->st_value);
 538                        *sym_index = symp - sym0;
 539                        return 0;
 540                }
 541        }
 542        fprintf(stderr, "Cannot find symbol for section %u: %s.\n",
 543                txtndx, txtname);
 544        return -1;
 545}
 546
 547/* Evade ISO C restriction: no declaration after statement in has_rel_mcount. */
 548static char const * __has_rel_mcount(Elf_Shdr const *const relhdr, /* reltype */
 549                                     Elf_Shdr const *const shdr0,
 550                                     char const *const shstrtab,
 551                                     char const *const fname)
 552{
 553        /* .sh_info depends on .sh_type == SHT_REL[,A] */
 554        Elf_Shdr const *const txthdr = &shdr0[w(relhdr->sh_info)];
 555        char const *const txtname = &shstrtab[w(txthdr->sh_name)];
 556
 557        if (strcmp("__mcount_loc", txtname) == 0) {
 558                fprintf(stderr, "warning: __mcount_loc already exists: %s\n",
 559                        fname);
 560                return already_has_rel_mcount;
 561        }
 562        if (w(txthdr->sh_type) != SHT_PROGBITS ||
 563            !(_w(txthdr->sh_flags) & SHF_EXECINSTR))
 564                return NULL;
 565        return txtname;
 566}
 567
 568static char const *has_rel_mcount(Elf_Shdr const *const relhdr,
 569                                  Elf_Shdr const *const shdr0,
 570                                  char const *const shstrtab,
 571                                  char const *const fname)
 572{
 573        if (w(relhdr->sh_type) != SHT_REL && w(relhdr->sh_type) != SHT_RELA)
 574                return NULL;
 575        return __has_rel_mcount(relhdr, shdr0, shstrtab, fname);
 576}
 577
 578
 579static unsigned tot_relsize(Elf_Shdr const *const shdr0,
 580                            unsigned nhdr,
 581                            const char *const shstrtab,
 582                            const char *const fname)
 583{
 584        unsigned totrelsz = 0;
 585        Elf_Shdr const *shdrp = shdr0;
 586        char const *txtname;
 587
 588        for (; nhdr; --nhdr, ++shdrp) {
 589                txtname = has_rel_mcount(shdrp, shdr0, shstrtab, fname);
 590                if (txtname == already_has_rel_mcount) {
 591                        totrelsz = 0;
 592                        break;
 593                }
 594                if (txtname && is_mcounted_section_name(txtname))
 595                        totrelsz += _w(shdrp->sh_size);
 596        }
 597        return totrelsz;
 598}
 599
 600/* Overall supervision for Elf32 ET_REL file. */
 601static int do_func(Elf_Ehdr *const ehdr, char const *const fname,
 602                   unsigned const reltype)
 603{
 604        Elf_Shdr *const shdr0 = (Elf_Shdr *)(_w(ehdr->e_shoff)
 605                + (void *)ehdr);
 606        unsigned const nhdr = get_shnum(ehdr, shdr0);
 607        Elf_Shdr *const shstr = &shdr0[get_shstrndx(ehdr, shdr0)];
 608        char const *const shstrtab = (char const *)(_w(shstr->sh_offset)
 609                + (void *)ehdr);
 610
 611        Elf_Shdr const *relhdr;
 612        unsigned k;
 613
 614        Elf32_Word *symtab;
 615        Elf32_Word *symtab_shndx;
 616
 617        /* Upper bound on space: assume all relevant relocs are for mcount. */
 618        unsigned       totrelsz;
 619
 620        Elf_Rel *      mrel0;
 621        Elf_Rel *      mrelp;
 622
 623        uint_t *      mloc0;
 624        uint_t *      mlocp;
 625
 626        unsigned rel_entsize = 0;
 627        unsigned symsec_sh_link = 0;
 628
 629        int result = 0;
 630
 631        totrelsz = tot_relsize(shdr0, nhdr, shstrtab, fname);
 632        if (totrelsz == 0)
 633                return 0;
 634        mrel0 = umalloc(totrelsz);
 635        mrelp = mrel0;
 636        if (!mrel0)
 637                return -1;
 638
 639        /* 2*sizeof(address) <= sizeof(Elf_Rel) */
 640        mloc0 = umalloc(totrelsz>>1);
 641        mlocp = mloc0;
 642        if (!mloc0) {
 643                free(mrel0);
 644                return -1;
 645        }
 646
 647        find_symtab(ehdr, shdr0, nhdr, &symtab, &symtab_shndx);
 648
 649        for (relhdr = shdr0, k = nhdr; k; --k, ++relhdr) {
 650                char const *const txtname = has_rel_mcount(relhdr, shdr0,
 651                        shstrtab, fname);
 652                if (txtname == already_has_rel_mcount) {
 653                        result = 0;
 654                        file_updated = 0;
 655                        goto out; /* Nothing to be done; don't append! */
 656                }
 657                if (txtname && is_mcounted_section_name(txtname)) {
 658                        unsigned int recsym;
 659                        uint_t recval = 0;
 660
 661                        symsec_sh_link = w(relhdr->sh_link);
 662                        result = find_secsym_ndx(w(relhdr->sh_info), txtname,
 663                                                &recval, &recsym,
 664                                                &shdr0[symsec_sh_link],
 665                                                symtab, symtab_shndx,
 666                                                ehdr);
 667                        if (result)
 668                                goto out;
 669
 670                        rel_entsize = _w(relhdr->sh_entsize);
 671                        mlocp = sift_rel_mcount(mlocp,
 672                                (void *)mlocp - (void *)mloc0, &mrelp,
 673                                relhdr, ehdr, recsym, recval, reltype);
 674                } else if (txtname && (warn_on_notrace_sect || make_nop)) {
 675                        /*
 676                         * This section is ignored by ftrace, but still
 677                         * has mcount calls. Convert them to nops now.
 678                         */
 679                        if (nop_mcount(relhdr, ehdr, txtname) < 0) {
 680                                result = -1;
 681                                goto out;
 682                        }
 683                }
 684        }
 685        if (!result && mloc0 != mlocp)
 686                result = append_func(ehdr, shstr, mloc0, mlocp, mrel0, mrelp,
 687                                     rel_entsize, symsec_sh_link);
 688out:
 689        free(mrel0);
 690        free(mloc0);
 691        return result;
 692}
 693