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Путь: Toys/Other, команды версии: Ver.4     Ver.9


readelf

Комментарии в файле readelf.c :

usage: readelf [-adehlnSs] [-p SECTION] [-x SECTION] [file...]

Отображает информацию о файлах ELF.
  • -a Эквивалентно -dhlnSs
  • -d Показать заголовки динамического раздела
  • -e (эквивалентно -hlS)
  • -h Показать заголовок ELF
  • -l Показать заголовки программ
  • -n Показать примечания
  • -p S Вывести строки, найденные в именованном/нумерованном разделе
  • -S Показать заголовки разделов
  • -s Показать таблицы символов (.dynsym и .symtab)
  • -x S Шестнадцатеричный дамп named/ нумерованный раздел
  • --dyn-syms Показать только таблицу символов .dynsym

  • usage: readelf [-adehlnSs] [-p SECTION] [-x SECTION] [file...]

    Displays information about ELF files.
  • -a Equivalent to -dhlnSs
  • -d Show dynamic section
  • -e Headers (equivalent to -hlS)
  • -h Show ELF header
  • -l Show program headers
  • -n Show notes
  • -p S Dump strings found in named/numbered section
  • -S Show section headers
  • -s Show symbol tables (.dynsym and .symtab)
  • -x S Hex dump of named/numbered section
  • --dyn-syms Show just .dynsym symbol table

  • Исходный текст в файле readelf.c

    #define FOR_readelf
    #include "toys.h"
    
    GLOBALS(
      char *x, *p;
    
      char *elf, *shstrtab, *f;
      unsigned long long shoff, phoff, size, shstrtabsz;
      int bits, endian, shnum, shentsize, phentsize;
    )
    
    // Section header.
    struct sh {
      unsigned type, link, info;
      unsigned long long flags, addr, offset, size, addralign, entsize;
      char *name;
    };
    
    // Program header.
    struct ph {
      unsigned type, flags;
      unsigned long long offset, vaddr, paddr, filesz, memsz, align;
    };
    
    static long long elf_get(char **p, int len)
    {
      long long result;
    
      if (*p+len-TT.elf>TT.size)
        perror_exit("Access off end: %td[%d] of %lld\n", *p-TT.elf, len, TT.size);
    
      result = ((TT.endian == 2) ? peek_be : peek_le)(*p, len);
      *p += len;
      return result;
    }
    
    static unsigned long long elf_long(char **p)
    {
      return elf_get(p, 4*(TT.bits+1));
    }
    
    static unsigned elf_int(char **p)
    {
      return elf_get(p, 4);
    }
    
    static unsigned short elf_short(char **p)
    {
      return elf_get(p, 2);
    }
    
    static int get_sh(unsigned i, struct sh *s)
    {
      char *shdr = TT.elf+TT.shoff+i*TT.shentsize;
      unsigned name_offset;
    
      if (i >= TT.shnum || shdr > TT.elf+TT.size-TT.shentsize) {
        printf("No shdr %d\n", i);
        return 0;
      }
    
      name_offset = elf_int(&shdr);
      s->type = elf_int(&shdr);
      s->flags = elf_long(&shdr);
      s->addr = elf_long(&shdr);
      s->offset = elf_long(&shdr);
      s->size = elf_long(&shdr);
      s->link = elf_int(&shdr);
      s->info = elf_int(&shdr);
      s->addralign = elf_long(&shdr);
      s->entsize = elf_long(&shdr);
    
      if (s->type != 8) {
        if (s->offset>TT.size || s->size>TT.size || s->offset>TT.size-s->size) {
          printf("Bad offset/size %llu/%llu for sh %d\n", s->offset, s->size, i);
          return 0;
        }
      }
    
      if (!TT.shstrtab) s->name = "?";
      else {
        s->name = TT.shstrtab + name_offset;
        if (name_offset > TT.shstrtabsz || s->name >= TT.elf+TT.size) {
          printf("Bad name for sh %d\n", i);
          return 0;
        }
      }
    
      return 1;
    }
    
    static int find_section(char *spec, struct sh *s)
    {
      char *end;
      unsigned i;
    
      // Valid section number?
      i = estrtol(spec, &end, 0);
      if (!errno && !*end && i<TT.shnum) return get_sh(i, s);
    
      // Search the section names.
      for (i=0; i<TT.shnum; i++)
        if (get_sh(i, s) && !strcmp(s->name, spec)) return 1;
    
      error_msg("%s: no section '%s", TT.f, spec);
      return 0;
    }
    
    static int get_ph(int i, struct ph *ph)
    {
      char *phdr = TT.elf+TT.phoff+i*TT.phentsize;
    
      if (phdr > TT.elf+TT.size-TT.phentsize) {
        printf("Bad phdr %d\n", i);
        return 0;
      }
    
      // Elf64_Phdr reordered fields.
      ph->type = elf_int(&phdr);
      if (TT.bits) {
        ph->flags = elf_int(&phdr);
        ph->offset = elf_long(&phdr);
        ph->vaddr = elf_long(&phdr);
        ph->paddr = elf_long(&phdr);
        ph->filesz = elf_long(&phdr);
        ph->memsz = elf_long(&phdr);
        ph->align = elf_long(&phdr);
      } else {
        ph->offset = elf_int(&phdr);
        ph->vaddr = elf_int(&phdr);
        ph->paddr = elf_int(&phdr);
        ph->filesz = elf_int(&phdr);
        ph->memsz = elf_int(&phdr);
        ph->flags = elf_int(&phdr);
        ph->align = elf_int(&phdr);
      }
    
      if (ph->offset >= TT.size-ph->filesz) {
        printf("phdr %d has bad offset/size %llu/%llu", i, ph->offset, ph->filesz);
        return 0;
      }
    
      return 1;
    }
    
    #define MAP(...) __VA_ARGS__
    #define DECODER(name, values) \
      static char *name(int type) { \
        static char unknown[20]; \
        struct {int v; char *s;} a[] = values; \
        int i; \
        \
        for (i=0; i<ARRAY_LEN(a); i++) if (type==a[i].v) return a[i].s; \
        sprintf(unknown, "0x%x", type); \
        return unknown; \
      }
    
    DECODER(dt_type, MAP({{0,"x(NULL)"},{1,"N(NEEDED)"},{2,"b(PLTRELSZ)"},
      {3,"x(PLTGOT)"},{4,"x(HASH)"},{5,"x(STRTAB)"},{6,"x(SYMTAB)"},{7,"x(RELA)"},
      {8,"b(RELASZ)"},{9,"b(RELAENT)"},{10,"b(STRSZ)"},{11,"b(SYMENT)"},
      {12,"x(INIT)"},{13,"x(FINI)"},{14,"S(SONAME)"},{15,"R(RPATH)"},
      {16,"x(SYMBOLIC)"},{17,"x(REL)"},{18,"b(RELSZ)"},{19,"b(RELENT)"},
      {20,"P(PLTREL)"},{21,"x(DEBUG)"},{22,"x(TEXTREL)"},{23,"x(JMPREL)"},
      {24,"d(BIND_NOW)"},{25,"x(INIT_ARRAY)"},{26,"x(FINI_ARRAY)"},
      {27,"b(INIT_ARRAYSZ)"},{28,"b(FINI_ARRAYSZ)"},{29,"R(RUNPATH)"},
      {30,"f(FLAGS)"},{32,"x(PREINIT_ARRAY)"},{33,"x(PREINIT_ARRAYSZ)"},
      {35,"b(RELRSZ)"},{36,"x(RELR)"},{37,"b(RELRENT)"},
      {0x6000000f,"x(ANDROID_REL)"},{0x60000010,"b(ANDROID_RELSZ)"},
      {0x60000011,"x(ANDROID_RELA)"},{0x60000012,"b(ANDROID_RELASZ)"},
      {0x6fffe000,"x(ANDROID_RELR)"},{0x6fffe001,"b(ANDROID_RELRSZ)"},
      {0x6fffe003,"x(ANDROID_RELRENT)"},{0x6ffffef5,"x(GNU_HASH)"},
      {0x6ffffef6,"x(TLSDESC_PLT)"},{0x6ffffef7,"x(TLSDESC_GOT)"},
      {0x6ffffff0,"x(VERSYM)"},{0x6ffffff9,"d(RELACOUNT)"},
      {0x6ffffffa,"d(RELCOUNT)"},{0x6ffffffb,"F(FLAGS_1)"},
      {0x6ffffffc," (VERDEF)"},{0x6ffffffd,"d(VERDEFNUM)"},
      {0x6ffffffe,"x(VERNEED)"},{0x6fffffff,"d(VERNEEDNUM)"}}))
    
    DECODER(et_type, MAP({{0,"NONE (None)"},{1,"REL (Relocatable file)"},
      {2,"EXEC (Executable file)"},{3,"DYN (Shared object file)"},
      {4,"CORE (Core file)"}}))
    
    DECODER(nt_type_core, MAP({{1,"NT_PRSTATUS"},{2,"NT_FPREGSET"},
      {3,"NT_PRPSINFO"},{5,"NT_PLATFORM"},{6,"NT_AUXV"},
      {0x46494c45,"NT_FILE"},{0x53494749,"NT_SIGINFO"}}))
    
    DECODER(nt_type_linux, MAP({{0x200,"NT_386_TLS"},{0x202, "NT_X86_XSTATE"},
      {0x400,"NT_ARM_VFP"},{0x401,"NT_ARM_TLS"},{0x405,"NT_ARM_SVE"}}))
    
    DECODER(os_abi, MAP({{0,"UNIX - System V"}}))
    
    DECODER(ph_type, MAP({{0,"NULL"},{1,"LOAD"},{2,"DYNAMIC"},{3,"INTERP"},
      {4,"NOTE"},{5,"SHLIB"},{6,"PHDR"},{7,"TLS"},{0x6474e550,"GNU_EH_FRAME"},
      {0x6474e551,"GNU_STACK"},{0x6474e552,"GNU_RELRO"},{0x70000001,"EXIDX"}}))
    
    DECODER(sh_type, MAP({{0,"NULL"},{1,"PROGBITS"},{2,"SYMTAB"},{3,"STRTAB"},
      {4,"RELA"},{5,"HASH"},{6,"DYNAMIC"},{7,"NOTE"},{8,"NOBITS"},{9,"REL"},
      {10,"SHLIB"},{11,"DYNSYM"},{14,"INIT_ARRAY"},{15,"FINI_ARRAY"},
      {16,"PREINIT_ARRAY"},{17,"GROUP"},{18,"SYMTAB_SHNDX"},{19,"RELR"},
      {0x60000001,"ANDROID_REL"},{0x60000002,"ANDROID_RELA"},
      {0x6fffff00,"ANDROID_RELR"},{0x6ffffff6,"GNU_HASH"},
      {0x6ffffffd,"VERDEF"},{0x6ffffffe,"VERNEED"},
      {0x6fffffff,"VERSYM"},{0x70000001,"ARM_EXIDX"},
      {0x70000003,"ARM_ATTRIBUTES"}}))
    
    DECODER(stb_type, MAP({{0,"LOCAL"},{1,"GLOBAL"},{2,"WEAK"}}))
    
    DECODER(stt_type, MAP({{0,"NOTYPE"},{1,"OBJECT"},{2,"FUNC"},{3,"SECTION"},
      {4,"FILE"},{5,"COMMON"},{6,"TLS"},{10,"GNU_IFUNC"}}))
    
    DECODER(stv_type, MAP({{0,"DEFAULT"},{1,"INTERNAL"},{2,"HIDDEN"},
      {3,"PROTECTED"}}))
    
    static void show_symbols(struct sh *table, struct sh *strtab)
    {
      char *symtab = TT.elf+table->offset, *ndx;
      int numsym = table->size/(TT.bits ? 24 : 16), i;
    
      if (!numsym) return;
    
      xputc('\n');
      printf("Symbol table '%s' contains %d entries:\n"
             "   Num:    %*s  Size Type    Bind   Vis      Ndx Name\n",
             table->name, numsym, 5+8*TT.bits, "Value");
      for (i=0; i<numsym; i++) {
        unsigned st_name = elf_int(&symtab), st_value, st_shndx, st_info, st_other;
        unsigned long st_size;
        char *name, buf[16];
    
        // The various fields were moved around for 64-bit.
        if (TT.bits) {
          st_info = *symtab++;
          st_other = *symtab++;
          st_shndx = elf_short(&symtab);
          st_value = elf_long(&symtab);
          st_size = elf_long(&symtab);
        } else {
          st_value = elf_int(&symtab);
          st_size = elf_int(&symtab);
          st_info = *symtab++;
          st_other = *symtab++;
          st_shndx = elf_short(&symtab);
        }
    
        // TODO: why do we trust name to be null terminated?
        name = TT.elf + strtab->offset + st_name;
        if (name >= TT.elf+TT.size) name = "???";
    
        if (!st_shndx) ndx = "UND";
        else if (st_shndx==0xfff1) ndx = "ABS";
        else sprintf(ndx = buf, "%d", st_shndx);
    
        // TODO: look up and show any symbol versions with @ or @@.
    
        printf("%6d: %0*x %5lu %-7s %-6s %-9s%3s %s\n", i, 8*(TT.bits+1),
          st_value, st_size, stt_type(st_info & 0xf), stb_type(st_info >> 4),
          stv_type(st_other & 3), ndx, name);
      }
    }
    
    static int notematch(int namesz, char **p, char *expected)
    {
      if (namesz!=strlen(expected)+1 || strcmp(*p, expected)) return 0;
      *p += namesz;
    
      return 1;
    }
    
    static void show_notes(unsigned long offset, unsigned long size)
    {
      char *note = TT.elf + offset;
    
      if (size > TT.size || offset > TT.size-size) {
        printf("Bad note bounds %lu/%lu\n", offset, size);
    
        return;
      }
    
      printf("  %-20s%11s\tDescription\n", "Owner", "Data size");
      while (note < TT.elf+offset+size) {
        char *p = note, *desc;
        unsigned namesz=elf_int(&p), descsz=elf_int(&p), type=elf_int(&p), j=0;
    
        if (namesz > size || descsz > size)
          return error_msg("%s: bad note @%lu", TT.f, offset);
        printf("  %-20.*s 0x%08x\t", namesz, p, descsz);
        if (notematch(namesz, &p, "GNU")) {
          if (type == 1) {
            printf("NT_GNU_ABI_TAG\tOS: %s, ABI: %u.%u.%u",
              !elf_int(&p)?"Linux":"?", elf_int(&p), elf_int(&p), elf_int(&p)), j=1;
          } else if (type == 3) {
    // TODO should this set j=1?
            printf("NT_GNU_BUILD_ID\t");
            for (;j<descsz;j++) printf("%02x", *p++);
          } else if (type == 4) {
            printf("NT_GNU_GOLD_VERSION\t%.*s", descsz, p), j=1;
          } else p -= 4;
        } else if (notematch(namesz, &p, "Android")) {
          if (type == 1) {
            printf("NT_VERSION\tAPI level %u", elf_int(&p)), j=1;
            if (descsz>=132) printf(", NDK %.64s (%.64s)", p, p+64);
          } else p -= 8;
        } else if (notematch(namesz, &p, "CORE")) {
          if (*(desc = nt_type_core(type)) != '0') printf("%s", desc), j=1;
    // TODO else p -= 5?
        } else if (notematch(namesz, &p, "LINUX")) {
          if (*(desc = nt_type_linux(type)) != '0') printf("%s", desc), j=1;
    // TODO else p -= 6?
        }
    
        // If we didn't do custom output above, show a hex dump.
        if (!j) {
          printf("0x%x\t", type);
          for (;j<descsz;j++) printf("%c%02x", j ? ' ' : '\t', *p++/*note[16+j]*/);
        }
        xputc('\n');
        note += 3*4 + ((namesz+3)&~3) + ((descsz+3)&~3);
      }
    }
    
    static void scan_elf()
    {
      struct sh dynamic = {}, dynstr = {}, dynsym = {}, shstr = {}, strtab = {},
        symtab = {}, s;
      struct ph ph;
      char *hdr = TT.elf;
      int type, machine, version, flags, entry, ehsize, phnum, shstrndx, i, j, w;
    
      if (TT.size < 45 || smemcmp(hdr, "\177ELF", 4))
        return error_msg("%s: not ELF", TT.f);
    
      TT.bits = hdr[4] - 1;
      TT.endian = hdr[5];
      if (TT.bits<0 || TT.bits>1 || TT.endian<1 || TT.endian>2 || hdr[6]!=1)
        return error_msg("%s: bad ELF", TT.f);
    
      hdr += 16; // EI_NIDENT
      type = elf_short(&hdr);
      machine = elf_short(&hdr);
      version = elf_int(&hdr);
      entry = elf_long(&hdr);
      TT.phoff = elf_long(&hdr);
      TT.shoff = elf_long(&hdr);
      flags = elf_int(&hdr);
      ehsize = elf_short(&hdr);
      TT.phentsize = elf_short(&hdr);
      phnum = elf_short(&hdr);
      TT.shentsize = elf_short(&hdr);
      TT.shnum = elf_short(&hdr);
      shstrndx = elf_short(&hdr);
    
      if (toys.optc > 1) printf("\nFile: %s\n", TT.f);
    
      if (FLAG(h)) {
        printf("ELF Header:\n");
        printf("  Magic:   ");
        for (i=0; i<16; i++) printf("%02x%c", TT.elf[i], (i==15) ? '\n' : ' ');
        printf("  Class:                             ELF%d\n", TT.bits?64:32);
        printf("  Data:                              2's complement, %s endian\n",
               (TT.endian==2)?"big":"little");
        printf("  Version:                           1 (current)\n");
        printf("  OS/ABI:                            %s\n", os_abi(TT.elf[7]));
        printf("  ABI Version:                       %d\n", TT.elf[8]);
        printf("  Type:                              %s\n", et_type(type));
        printf("  Machine:                           %s\n", elf_arch_name(machine));
        printf("  Version:                           0x%x\n", version);
        printf("  Entry point address:               0x%x\n", entry);
        printf("  Start of program headers:          %llu (bytes into file)\n",
               TT.phoff);
        printf("  Start of section headers:          %llu (bytes into file)\n",
               TT.shoff);
        printf("  Flags:                             0x%x\n", flags);
        printf("  Size of this header:               %d (bytes)\n", ehsize);
        printf("  Size of program headers:           %d (bytes)\n", TT.phentsize);
        printf("  Number of program headers:         %d\n", phnum);
        printf("  Size of section headers:           %d (bytes)\n", TT.shentsize);
        printf("  Number of section headers:         %d\n", TT.shnum);
        printf("  Section header string table index: %d\n", shstrndx);
      }
      if (TT.phoff > TT.size) return error_msg("%s: bad phoff", TT.f);
      if (TT.shoff > TT.size) return error_msg("%s: bad shoff", TT.f);
    
      // Set up the section header string table so we can use section header names.
      // Core files have shstrndx == 0.
      TT.shstrtab = 0;
      TT.shstrtabsz = 0;
      if (shstrndx) {
        if (!get_sh(shstrndx, &shstr) || shstr.type != 3 /*SHT_STRTAB*/)
          return error_msg("%s: bad shstrndx", TT.f);
        TT.shstrtab = TT.elf+shstr.offset;
        TT.shstrtabsz = shstr.size;
      }
    
      w = 8<<TT.bits;
      if (FLAG(S)) {
        if (!TT.shnum) printf("\nThere are no sections in this file.\n");
        else {
          if (!FLAG(h))
            printf("There are %d section headers, starting at offset %#llx:\n",
                   TT.shnum, TT.shoff);
          printf("\nSection Headers:\n"
                 "  [Nr] %-17s %-15s %-*s %-6s %-6s ES Flg Lk Inf Al\n",
                 "Name", "Type", w, "Address", "Off", "Size");
        }
      }
      // We need to iterate through the section headers even if we're not
      // dumping them, to find specific sections.
      for (i=0; i<TT.shnum; i++) {
        if (!get_sh(i, &s)) continue;
        if (s.type == 2 /*SHT_SYMTAB*/) symtab = s;
        else if (s.type == 6 /*SHT_DYNAMIC*/) dynamic = s;
        else if (s.type == 11 /*SHT_DYNSYM*/) dynsym = s;
        else if (s.type == 3 /*SHT_STRTAB*/) {
          if (!strcmp(s.name, ".strtab")) strtab = s;
          else if (!strcmp(s.name, ".dynstr")) dynstr = s;
        }
    
        if (FLAG(S)) {
          char sh_flags[12] = {}, *p = sh_flags;
    
          for (j=0; j<12; j++) if (s.flags&(1<<j)) *p++ = "WAXxMSILOTC"[j];
          printf("  [%2d] %-17s %-15s %0*llx %06llx %06llx %02llx %3s %2d %2d %2lld\n",
                 i, s.name, sh_type(s.type), w, s.addr, s.offset, s.size,
                 s.entsize, sh_flags, s.link, s.info, s.addralign);
        }
      }
      if (FLAG(S) && TT.shnum)
        printf("Key:\n  (W)rite, (A)lloc, e(X)ecute, (M)erge, (S)trings, (I)nfo\n"
               "  (L)ink order, (O)S, (G)roup, (T)LS, (C)ompressed, x=unknown\n");
    
      if (FLAG(l)) {
        xputc('\n');
        if (!phnum) printf("There are no program headers in this file.\n");
        else {
          if (!FLAG(h))
            printf("Elf file type is %s\nEntry point %#x\n"
              "There are %d program headers, starting at offset %lld\n\n",
              et_type(type), entry, phnum, TT.phoff);
          printf("Program Headers:\n"
                 "  %-14s %-8s %-*s   %-*s   %-7s %-7s Flg Align\n", "Type",
                 "Offset", w, "VirtAddr", w, "PhysAddr", "FileSiz", "MemSiz");
          for (i = 0; i<phnum; i++) {
            if (!get_ph(i, &ph)) continue;
            printf("  %-14s 0x%06llx 0x%0*llx 0x%0*llx 0x%05llx 0x%05llx %c%c%c %#llx\n",
                   ph_type(ph.type), ph.offset, w, ph.vaddr, w, ph.paddr,
                   ph.filesz, ph.memsz, (ph.flags&4)?'R':' ', (ph.flags&2)?'W':' ',
                   (ph.flags&1)?'E':' ', ph.align);
            if (ph.type == 3 /*PH_INTERP*/ && ph.filesz<TT.size &&
                ph.offset<TT.size && ph.filesz - 1 < TT.size - ph.offset) {
    // TODO: ph.filesz of 0 prints unlimited length string
              printf("      [Requesting program interpreter: %*s]\n",
                     (int) ph.filesz-1, TT.elf+ph.offset);
            }
          }
    
          printf("\n Section to Segment mapping:\n  Segment Sections...\n");
          for (i=0; i<phnum; i++) {
            if (!get_ph(i, &ph)) continue;
            printf("   %02d     ", i);
            for (j=0; j<TT.shnum; j++) {
              if (!get_sh(j, &s)) continue;
              if (!*s.name) continue;
              if (s.offset >= ph.offset && s.offset+s.size <= ph.offset+ph.filesz)
                printf("%s ", s.name);
            }
            xputc('\n');
          }
        }
      }
    
      // binutils ld emits a bunch of extra DT_NULL entries, so binutils readelf
      // uses two passes here! We just tell the truth, which matches -h.
      if (FLAG(d)) {
        char *dyn = TT.elf+dynamic.offset, *end = dyn+dynamic.size;
    
        xputc('\n');
        if (!dynamic.size) printf("There is no dynamic section in this file.\n");
        else if (!dynamic.entsize) printf("Bad dynamic entry size 0!\n");
        else {
          printf("Dynamic section at offset 0x%llx contains %lld entries:\n"
                 "  %-*s %-20s %s\n", dynamic.offset, dynamic.size/dynamic.entsize,
                 w+2, "Tag", "Type", "Name/Value");
          while (dyn < end) {
            unsigned long long tag = elf_long(&dyn), val = elf_long(&dyn);
            char *type = dt_type(tag);
    
            printf(" 0x%0*llx %-20s ", w, tag, type+(*type!='0'));
            if (*type == 'd') printf("%lld\n", val);
            else if (*type == 'b') printf("%lld (bytes)\n", val);
    // TODO: trusting this %s to be null terminated
            else if (*type == 's') printf("%s\n", TT.elf+dynstr.offset+val);
            else if (*type == 'f' || *type == 'F') {
              struct bitname { int bit; char *s; }
                df_names[] = {{0, "ORIGIN"},{1,"SYMBOLIC"},{2,"TEXTREL"},
                  {3,"BIND_NOW"},{4,"STATIC_TLS"},{}},
                df_1_names[]={{0,"NOW"},{1,"GLOBAL"},{2,"GROUP"},{3,"NODELETE"},
                  {5,"INITFIRST"},{27,"PIE"},{}},
                *names = *type == 'f' ? df_names : df_1_names;
              int mask;
    
              if (*type == 'F') printf("Flags: ");
              for (j=0; names[j].s; j++)
                if (val & (mask=(1<<names[j].bit)))
                  printf("%s%s", names[j].s, (val &= ~mask) ? " " : "");
              if (val) printf("0x%llx", val);
              xputc('\n');
            } else if (*type == 'N' || *type == 'R' || *type == 'S') {
              char *s = TT.elf+dynstr.offset+val;
    
              if (dynstr.offset>TT.size || val>TT.size || dynstr.offset>TT.size-val)
                s = "???";
              printf("%s: [%s]\n", *type=='N' ? "Shared library" :
                (*type=='R' ? "Library runpath" : "Library soname"), s);
            } else if (*type == 'P') {
              j = strlen(type = dt_type(val));
              if (*type != '0') type += 2, j -= 3;
              printf("%*.*s\n", j, j, type);
            } else printf("0x%llx\n", val);
          }
        }
      }
    
      if (FLAG(dyn_syms)) show_symbols(&dynsym, &dynstr);
      if (FLAG(s)) show_symbols(&symtab, &strtab);
    
      if (FLAG(n)) {
        int found = 0;
    
        for (i=0; i<TT.shnum; i++) {
          if (!get_sh(i, &s)) continue;
          if (s.type == 7 /*SHT_NOTE*/) {
            printf("\nDisplaying notes found in: %s\n", s.name);
            show_notes(s.offset, s.size);
            found = 1;
          }
        }
        for (i=0; !found && i<phnum; i++) {
          if (!get_ph(i, &ph)) continue;
          if (ph.type == 4 /*PT_NOTE*/) {
            printf("\n"
              "Displaying notes found at file offset 0x%llx with length 0x%llx:\n",
              ph.offset, ph.filesz);
            show_notes(ph.offset, ph.filesz);
          }
        }
      }
    
      if (FLAG(x) && find_section(TT.x, &s)) {
        char *p = TT.elf+s.offset;
        long offset = 0;
    
        printf("\nHex dump of section '%s':\n", s.name);
        while (offset < s.size) {
          int space = 2*16 + 16/4;
    
          printf("  0x%08lx ", offset);
          for (i=0; i<16 && offset < s.size; offset++)
            space -= printf("%02x%s", *p++, " "+!!(++i%4));
          printf("%*s", space, "");
          for (p -= i; i; i--, p++) putchar((*p>=' ' && *p<='~') ? *p : '.');
          xputc('\n');
        }
        xputc('\n');
      }
    
      if (FLAG(p) && find_section(TT.p, &s)) {
        char *begin = TT.elf+s.offset, *end = begin + s.size, *p = begin;
        int any = 0;
    
        printf("\nString dump of section '%s':\n", s.name);
        for (; p < end; p++) {
          if (isprint(*p)) {
            printf("  [%6tx]  ", p-begin);
            while (p < end && isprint(*p)) putchar(*p++);
            xputc('\n');
            any=1;
          }
        }
        if (!any) printf("  No strings found in this section.\n");
        xputc('\n');
      }
    }
    
    void readelf_main(void)
    {
      char **arg;
      int all = FLAG_d|FLAG_h|FLAG_l|FLAG_n|FLAG_S|FLAG_s|FLAG_dyn_syms;
    
      if (FLAG(a)) toys.optflags |= all;
      if (FLAG(e)) toys.optflags |= FLAG_h|FLAG_l|FLAG_S;
      if (FLAG(s)) toys.optflags |= FLAG_dyn_syms;
      if (!(toys.optflags & (all|FLAG_p|FLAG_x))) help_exit("needs a flag");
    
      for (arg = toys.optargs; *arg; arg++) {
        int fd = open(TT.f = *arg, O_RDONLY);
        struct stat sb;
    
        if (fd == -1) perror_msg("%s", TT.f);
        else {
          if (fstat(fd, &sb)) perror_msg("%s", TT.f);
          else if (!sb.st_size) error_msg("%s: empty", TT.f);
          else if (!S_ISREG(sb.st_mode)) error_msg("%s: not a regular file",TT.f);
          else {
            TT.elf = xmmap(0, TT.size=sb.st_size, PROT_READ, MAP_SHARED, fd, 0);
            scan_elf();
            munmap(TT.elf, TT.size);
          }
          close(fd);
        }
      }
    }