readelf.c 12 KB

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