utils/readelf.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * A small little readelf implementation for uClibc
   4  *
   5  * Copyright (C) 2000-2006 Erik Andersen <andersen@uclibc.org>
   6  *
   7  * Several functions in this file (specifically, elf_find_section_type(),
   8  * elf_find_phdr_type(), and elf_find_dynamic(), were stolen from elflib.c from
   9  * elfvector (http://www.BitWagon.com/elfvector.html) by John F. Reiser
  10  * <jreiser@BitWagon.com>, which is copyright 2000 BitWagon Software LLC
  11  * (GPL2).
  12  *
  13  * Licensed under GPLv2 or later
  14  */
  15
  16
  17 #include <fcntl.h>
  18 #include <stdio.h>
  19 #include <stdlib.h>
  20 #include <string.h>
  21 #include <unistd.h>
  22 #include <sys/mman.h>
  23 #include <sys/stat.h>
  24 #include <sys/types.h>
  25
  26 #include "bswap.h"
  27 #include "link.h"
  28 /* makefile will include elf.h for us */
  29
  30 static int byteswap;
  31 static __inline__ uint32_t byteswap32_to_host(uint32_t value)
  32 {
  33         if (byteswap==1) {
  34                 return(bswap_32(value));
  35         } else {
  36                 return(value);
  37         }
  38 }
  39 static __inline__ uint64_t byteswap64_to_host(uint64_t value)
  40 {
  41         if (byteswap==1) {
  42                 return(bswap_64(value));
  43         } else {
  44                 return(value);
  45         }
  46 }
  47 #if __WORDSIZE == 64
  48 # define byteswap_to_host(x) byteswap64_to_host(x)
  49 #else
  50 # define byteswap_to_host(x) byteswap32_to_host(x)
  51 #endif
  52
  53 static ElfW(Shdr) * elf_find_section_type( uint32_t key, ElfW(Ehdr) *ehdr)
  54 {
  55         int j;
  56         ElfW(Shdr) *shdr = (ElfW(Shdr) *)(ehdr->e_shoff + (char *)ehdr);
  57         for (j = ehdr->e_shnum; --j>=0; ++shdr) {
  58                 if (key==byteswap32_to_host(shdr->sh_type)) {
  59                         return shdr;
  60                 }
  61         }
  62         return NULL;
  63 }
  64
  65 static ElfW(Phdr) * elf_find_phdr_type( uint32_t type, ElfW(Ehdr) *ehdr)
  66 {
  67         int j;
  68         ElfW(Phdr) *phdr = (ElfW(Phdr) *)(ehdr->e_phoff + (char *)ehdr);
  69         for (j = ehdr->e_phnum; --j>=0; ++phdr) {
  70                 if (type==byteswap32_to_host(phdr->p_type)) {
  71                         return phdr;
  72                 }
  73         }
  74         return NULL;
  75 }
  76
  77 /* Returns value if return_val==1, ptr otherwise */
  78 static void * elf_find_dynamic( int64_t const key, ElfW(Dyn) *dynp,
  79         ElfW(Ehdr) *ehdr, int return_val)
  80 {
  81         ElfW(Phdr) *pt_text = elf_find_phdr_type(PT_LOAD, ehdr);
  82         ElfW(Addr) tx_reloc = byteswap_to_host(pt_text->p_vaddr) - byteswap_to_host(pt_text->p_offset);
  83         for (; DT_NULL!=byteswap_to_host(dynp->d_tag); ++dynp) {
  84                 if (key == byteswap_to_host(dynp->d_tag)) {
  85                         if (return_val == 1)
  86                                 return (void *)byteswap_to_host(dynp->d_un.d_val);
  87                         else
  88                                 return (void *)(byteswap_to_host(dynp->d_un.d_val) - tx_reloc + (char *)ehdr );
  89                 }
  90         }
  91         return NULL;
  92 }
  93
  94 static int check_elf_header(ElfW(Ehdr) *const ehdr)
  95 {
  96         if (! ehdr || strncmp((void *)ehdr, ELFMAG, SELFMAG) != 0 ||
  97                         (ehdr->e_ident[EI_CLASS] != ELFCLASS32 &&
  98                          ehdr->e_ident[EI_CLASS] != ELFCLASS64) ||
  99                         ehdr->e_ident[EI_VERSION] != EV_CURRENT)
 100         {
 101                 return 1;
 102         }
 103
 104         /* Check if the target endianness matches the host's endianness */
 105         byteswap = 0;
 106 #if __BYTE_ORDER == __LITTLE_ENDIAN
 107         if (ehdr->e_ident[5] == ELFDATA2MSB) {
 108                 /* Ick -- we will have to byte-swap everything */
 109                 byteswap = 1;
 110         }
 111 #elif __BYTE_ORDER == __BIG_ENDIAN
 112         if (ehdr->e_ident[5] == ELFDATA2LSB) {
 113                 byteswap = 1;
 114         }
 115 #else
 116 #error Unknown host byte order!
 117 #endif
 118         /* Be vary lazy, and only byteswap the stuff we use */
 119         if (byteswap==1) {
 120                 ehdr->e_type=bswap_16(ehdr->e_type);
 121                 ehdr->e_machine=bswap_16(ehdr->e_machine);
 122                 ehdr->e_phoff=byteswap_to_host(ehdr->e_phoff);
 123                 ehdr->e_shoff=byteswap_to_host(ehdr->e_shoff);
 124                 ehdr->e_phnum=bswap_16(ehdr->e_phnum);
 125                 ehdr->e_shnum=bswap_16(ehdr->e_shnum);
 126         }
 127         return 0;
 128 }
 129
 130
 131 static void describe_elf_hdr(ElfW(Ehdr)* ehdr)
 132 {
 133         char *tmp, *tmp1;
 134
 135         switch (ehdr->e_type) {
 136                 case ET_NONE:   tmp = "None"; tmp1 = "NONE"; break;
 137                 case ET_REL:    tmp = "Relocatable File"; tmp1 = "REL"; break;
 138                 case ET_EXEC:   tmp = "Executable file"; tmp1 = "EXEC"; break;
 139                 case ET_DYN:    tmp = "Shared object file"; tmp1 = "DYN"; break;
 140                 case ET_CORE:   tmp = "Core file"; tmp1 = "CORE"; break;
 141                 default:
 142                                                 tmp = tmp1 = "Unknown";
 143         }
 144         printf( "Type:\t\t%s (%s)\n", tmp1, tmp);
 145
 146         switch (ehdr->e_machine) {
 147                 case EM_NONE:           tmp="No machine"; break;
 148                 case EM_M32:            tmp="AT&T WE 32100"; break;
 149                 case EM_SPARC:          tmp="SUN SPARC"; break;
 150                 case EM_386:            tmp="Intel 80386"; break;
 151                 case EM_68K:            tmp="Motorola m68k family"; break;
 152                 case EM_88K:            tmp="Motorola m88k family"; break;
 153                 case EM_486:            tmp="Intel 80486"; break;
 154                 case EM_860:            tmp="Intel 80860"; break;
 155                 case EM_MIPS:           tmp="MIPS R3000 big-endian"; break;
 156                 case EM_S370:           tmp="IBM System/370"; break;
 157                 case EM_MIPS_RS3_LE:    tmp="MIPS R3000 little-endian"; break;
 158                 case EM_OLD_SPARCV9:    tmp="Sparc v9 (old)"; break;
 159                 case EM_PARISC:         tmp="HPPA"; break;
 160                 /*case EM_PPC_OLD:      tmp="Power PC (old)"; break;  conflicts with EM_VPP500 */
 161                 case EM_SPARC32PLUS:    tmp="Sun's v8plus"; break;
 162                 case EM_960:            tmp="Intel 80960"; break;
 163                 case EM_PPC:            tmp="PowerPC"; break;
 164                 case EM_PPC64:          tmp="PowerPC 64-bit"; break;
 165                 case EM_V800:           tmp="NEC V800 series"; break;
 166                 case EM_FR20:           tmp="Fujitsu FR20"; break;
 167                 case EM_RH32:           tmp="TRW RH-32"; break;
 168                 case EM_MCORE:          tmp="MCORE"; break;
 169                 case EM_ARM:            tmp="ARM"; break;
 170                 case EM_FAKE_ALPHA:     tmp="Digital Alpha"; break;
 171                 case EM_SH:                     tmp="Renesas SH"; break;
 172                 case EM_SPARCV9:        tmp="SPARC v9 64-bit"; break;
 173                 case EM_TRICORE:        tmp="Siemens Tricore"; break;
 174                 case EM_ARC:            tmp="Argonaut RISC Core"; break;
 175                 case EM_H8_300:         tmp="Renesas H8/300"; break;
 176                 case EM_H8_300H:        tmp="Renesas H8/300H"; break;
 177                 case EM_H8S:            tmp="Renesas H8S"; break;
 178                 case EM_H8_500:         tmp="Renesas H8/500"; break;
 179                 case EM_IA_64:          tmp="Intel Merced"; break;
 180                 case EM_MIPS_X:         tmp="Stanford MIPS-X"; break;
 181                 case EM_COLDFIRE:       tmp="Motorola Coldfire"; break;
 182                 case EM_68HC12:         tmp="Motorola M68HC12"; break;
 183                 case EM_ALPHA:          tmp="Alpha"; break;
 184                 case EM_CYGNUS_D10V:
 185                 case EM_D10V:           tmp="Mitsubishi D10V"; break;
 186                 case EM_CYGNUS_D30V:
 187                 case EM_D30V:           tmp="Mitsubishi D30V"; break;
 188                 case EM_CYGNUS_M32R:
 189                 case EM_M32R:           tmp="Renesas M32R (formerly Mitsubishi M32r)"; break;
 190                 case EM_CYGNUS_V850:
 191                 case EM_V850:           tmp="NEC v850"; break;
 192                 case EM_CYGNUS_MN10300:
 193                 case EM_MN10300:        tmp="Matsushita MN10300"; break;
 194                 case EM_CYGNUS_MN10200:
 195                 case EM_MN10200:        tmp="Matsushita MN10200"; break;
 196                 case EM_CYGNUS_FR30:
 197                 case EM_FR30:           tmp="Fujitsu FR30"; break;
 198                 case EM_CYGNUS_FRV:
 199                 case EM_PJ_OLD:
 200                 case EM_PJ:                     tmp="picoJava"; break;
 201                 case EM_MMA:            tmp="Fujitsu MMA Multimedia Accelerator"; break;
 202                 case EM_PCP:            tmp="Siemens PCP"; break;
 203                 case EM_NCPU:           tmp="Sony nCPU embeeded RISC"; break;
 204                 case EM_NDR1:           tmp="Denso NDR1 microprocessor"; break;
 205                 case EM_STARCORE:       tmp="Motorola Start*Core processor"; break;
 206                 case EM_ME16:           tmp="Toyota ME16 processor"; break;
 207                 case EM_ST100:          tmp="STMicroelectronic ST100 processor"; break;
 208                 case EM_TINYJ:          tmp="Advanced Logic Corp. Tinyj emb.fam"; break;
 209                 case EM_FX66:           tmp="Siemens FX66 microcontroller"; break;
 210                 case EM_ST9PLUS:        tmp="STMicroelectronics ST9+ 8/16 mc"; break;
 211                 case EM_ST7:            tmp="STmicroelectronics ST7 8 bit mc"; break;
 212                 case EM_68HC16:         tmp="Motorola MC68HC16 microcontroller"; break;
 213                 case EM_68HC11:         tmp="Motorola MC68HC11 microcontroller"; break;
 214                 case EM_68HC08:         tmp="Motorola MC68HC08 microcontroller"; break;
 215                 case EM_68HC05:         tmp="Motorola MC68HC05 microcontroller"; break;
 216                 case EM_SVX:            tmp="Silicon Graphics SVx"; break;
 217                 case EM_ST19:           tmp="STMicroelectronics ST19 8 bit mc"; break;
 218                 case EM_VAX:            tmp="Digital VAX"; break;
 219                 case EM_AVR_OLD:
 220                 case EM_AVR:            tmp="Atmel AVR 8-bit microcontroller"; break;
 221                 case EM_CRIS:           tmp="Axis Communications 32-bit embedded processor"; break;
 222                 case EM_JAVELIN:        tmp="Infineon Technologies 32-bit embedded processor"; break;
 223                 case EM_FIREPATH:       tmp="Element 14 64-bit DSP Processor"; break;
 224                 case EM_ZSP:            tmp="LSI Logic 16-bit DSP Processor"; break;
 225                 case EM_MMIX:           tmp="Donald Knuth's educational 64-bit processor"; break;
 226                 case EM_HUANY:          tmp="Harvard University machine-independent object files"; break;
 227                 case EM_PRISM:          tmp="SiTera Prism"; break;
 228                 case EM_X86_64:         tmp="AMD x86-64 architecture"; break;
 229                 case EM_S390_OLD:
 230                 case EM_S390:           tmp="IBM S390"; break;
 231                 case EM_XSTORMY16:      tmp="Sanyo Xstormy16 CPU core"; break;
 232                 case EM_OPENRISC:
 233                 case EM_OR32:           tmp="OpenRISC"; break;
 234                 case EM_CRX:            tmp="National Semiconductor CRX microprocessor"; break;
 235                 case EM_DLX:            tmp="OpenDLX"; break;
 236                 case EM_IP2K_OLD:
 237                 case EM_IP2K:           tmp="Ubicom IP2xxx 8-bit microcontrollers"; break;
 238                 case EM_IQ2000:         tmp="Vitesse IQ2000"; break;
 239                 case EM_XTENSA_OLD:
 240                 case EM_XTENSA:         tmp="Tensilica Xtensa Processor"; break;
 241                 case EM_M32C:           tmp="Renesas M32c"; break;
 242                 case EM_MT:                     tmp="Morpho Techologies MT processor"; break;
 243                 case EM_BLACKFIN:       tmp="Analog Devices Blackfin"; break;
 244                 case EM_NIOS32:         tmp="Altera Nios 32"; break;
 245                 case EM_ALTERA_NIOS2:   tmp="Altera Nios II"; break;
 246                 case EM_VPP500:         tmp="Fujitsu VPP500"; break;
 247                 case EM_PDSP:           tmp="Sony DSP Processor"; break;
 248                 default:                        tmp="unknown";
 249         }
 250         printf( "Machine:\t%s\n", tmp);
 251
 252         switch (ehdr->e_ident[EI_CLASS]) {
 253                 case ELFCLASSNONE: tmp = "Invalid class";  break;
 254                 case ELFCLASS32:   tmp = "ELF32"; break;
 255                 case ELFCLASS64:   tmp = "ELF64"; break;
 256                 default:           tmp = "Unknown";
 257         }
 258         printf( "Class:\t\t%s\n", tmp);
 259
 260         switch (ehdr->e_ident[EI_DATA]) {
 261                 case ELFDATANONE:  tmp = "Invalid data encoding"; break;
 262                 case ELFDATA2LSB:  tmp = "2's complement, little endian"; break;
 263                 case ELFDATA2MSB:  tmp = "2's complement, big endian"; break;
 264                 default:           tmp = "Unknown";
 265         }
 266         printf( "Data:\t\t%s\n", tmp);
 267
 268         printf( "Version:\t%d %s\n", ehdr->e_ident[EI_VERSION],
 269                         (ehdr->e_ident[EI_VERSION]==EV_CURRENT)?
 270                         "(current)" : "(unknown: %lx)");
 271
 272         switch (ehdr->e_ident[EI_OSABI]) {
 273                 case ELFOSABI_SYSV:       tmp ="UNIX - System V"; break;
 274                 case ELFOSABI_HPUX:       tmp ="UNIX - HP-UX"; break;
 275                 case ELFOSABI_NETBSD:     tmp ="UNIX - NetBSD"; break;
 276                 case ELFOSABI_LINUX:      tmp ="UNIX - Linux"; break;
 277                 case ELFOSABI_HURD:       tmp ="GNU/Hurd"; break;
 278                 case ELFOSABI_SOLARIS:    tmp ="UNIX - Solaris"; break;
 279                 case ELFOSABI_AIX:        tmp ="UNIX - AIX"; break;
 280                 case ELFOSABI_IRIX:       tmp ="UNIX - IRIX"; break;
 281                 case ELFOSABI_FREEBSD:    tmp ="UNIX - FreeBSD"; break;
 282                 case ELFOSABI_TRU64:      tmp ="UNIX - TRU64"; break;
 283                 case ELFOSABI_MODESTO:    tmp ="Novell - Modesto"; break;
 284                 case ELFOSABI_OPENBSD:    tmp ="UNIX - OpenBSD"; break;
 285                 case ELFOSABI_STANDALONE: tmp ="Standalone App"; break;
 286                 case ELFOSABI_ARM:        tmp ="ARM"; break;
 287                 default:                  tmp = "Unknown";
 288         }
 289         printf( "OS/ABI:\t\t%s\n", tmp);
 290
 291         printf( "ABI Version:\t%d\n", ehdr->e_ident[EI_ABIVERSION]);
 292 }
 293
 294 static void list_needed_libraries(ElfW(Dyn)* dynamic, char *strtab)
 295 {
 296         ElfW(Dyn)  *dyns;
 297
 298         printf("Dependancies:\n");
 299         for (dyns=dynamic; byteswap_to_host(dyns->d_tag)!=DT_NULL; ++dyns) {
 300                 if (dyns->d_tag == DT_NEEDED) {
 301                         printf("\t%s\n", (char*)strtab + byteswap_to_host(dyns->d_un.d_val));
 302                 }
 303         }
 304 }
 305
 306 static void describe_elf_interpreter(ElfW(Ehdr)* ehdr)
 307 {
 308         ElfW(Phdr) *phdr;
 309         phdr = elf_find_phdr_type(PT_INTERP, ehdr);
 310         if (phdr) {
 311                 printf("Interpreter:\t%s\n", (char*)ehdr + byteswap_to_host(phdr->p_offset));
 312         }
 313 }
 314
 315 int main( int argc, char** argv)
 316 {
 317         /* map the .so, and locate interesting pieces */
 318         char *dynstr;
 319         char *thefilename = argv[1];
 320         FILE *thefile;
 321         struct stat statbuf;
 322         ElfW(Ehdr) *ehdr = 0;
 323         ElfW(Shdr) *dynsec;
 324         ElfW(Dyn) *dynamic;
 325
 326         if (argc < 2 || !thefilename) {
 327                 fprintf(stderr, "No filename specified.\n");
 328                 exit(EXIT_FAILURE);
 329         }
 330         if (!(thefile = fopen(thefilename, "r"))) {
 331                 perror(thefilename);
 332                 exit(EXIT_FAILURE);
 333         }
 334         if (fstat(fileno(thefile), &statbuf) < 0) {
 335                 perror(thefilename);
 336                 exit(EXIT_FAILURE);
 337         }
 338
 339         if ((size_t)statbuf.st_size < sizeof(ElfW(Ehdr)))
 340                 goto foo;
 341
 342         /* mmap the file to make reading stuff from it effortless */
 343         ehdr = (ElfW(Ehdr) *)mmap(0, statbuf.st_size,
 344                         PROT_READ|PROT_WRITE, MAP_PRIVATE, fileno(thefile), 0);
 345
 346 foo:
 347         /* Check if this looks legit */
 348         if (check_elf_header(ehdr)) {
 349                 fprintf(stderr, "This does not appear to be an ELF file.\n");
 350                 exit(EXIT_FAILURE);
 351         }
 352         describe_elf_hdr(ehdr);
 353         describe_elf_interpreter(ehdr);
 354
 355         dynsec = elf_find_section_type(SHT_DYNAMIC, ehdr);
 356         if (dynsec) {
 357                 dynamic = (ElfW(Dyn)*)(byteswap_to_host(dynsec->sh_offset) + (char *)ehdr);
 358                 dynstr = (char *)elf_find_dynamic(DT_STRTAB, dynamic, ehdr, 0);
 359                 list_needed_libraries(dynamic, dynstr);
 360         }
 361
 362         return 0;
 363 }