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 by Lineo, inc and Erik Andersen
  6. * Copyright (C) 2000-2002 Erik Andersen <andersee@debian.org>
  7. *
  8. * Several functions in this file (specifically, elf_find_section_type(),
  9. * elf_find_phdr_type(), and elf_find_dynamic(), were stolen from elflib.c from
  10. * elfvector (http://www.BitWagon.com/elfvector.html) by John F. Reiser
  11. * <jreiser@BitWagon.com>, which is copyright 2000 BitWagon Software LLC
  12. * (GPL2).
  13. *
  14. * This program is free software; you can redistribute it and/or modify
  15. * it under the terms of the GNU General Public License as published by
  16. * the Free Software Foundation; either version 2 of the License, or
  17. * (at your option) any later version.
  18. *
  19. * This program is distributed in the hope that it will be useful,
  20. * but WITHOUT ANY WARRANTY; without even the implied warranty of
  21. * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  22. * General Public License for more details.
  23. *
  24. * You should have received a copy of the GNU General Public License
  25. * along with this program; if not, write to the Free Software
  26. * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  27. *
  28. */
  29. #include <fcntl.h>
  30. #include <stdio.h>
  31. #include <stdlib.h>
  32. #include <string.h>
  33. #include <unistd.h>
  34. #include <sys/mman.h>
  35. #include <sys/stat.h>
  36. #include <sys/types.h>
  37. #include "bswap.h"
  38. #include "elf.h"
  39. int byteswap;
  40. inline uint32_t byteswap32_to_host(uint32_t value)
  41. {
  42. if (byteswap==1) {
  43. return(bswap_32(value));
  44. } else {
  45. return(value);
  46. }
  47. }
  48. Elf32_Shdr * elf_find_section_type( int key, Elf32_Ehdr *ehdr)
  49. {
  50. int j;
  51. Elf32_Shdr *shdr = (Elf32_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. Elf32_Phdr * elf_find_phdr_type( int type, Elf32_Ehdr *ehdr)
  60. {
  61. int j;
  62. Elf32_Phdr *phdr = (Elf32_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(int const key, Elf32_Dyn *dynp,
  72. Elf32_Ehdr *ehdr, int return_val)
  73. {
  74. Elf32_Phdr *pt_text = elf_find_phdr_type(PT_LOAD, ehdr);
  75. unsigned tx_reloc = byteswap32_to_host(pt_text->p_vaddr) - byteswap32_to_host(pt_text->p_offset);
  76. for (; DT_NULL!=byteswap32_to_host(dynp->d_tag); ++dynp) {
  77. if (key == byteswap32_to_host(dynp->d_tag)) {
  78. if (return_val == 1)
  79. return (void *)(intptr_t)byteswap32_to_host(dynp->d_un.d_val);
  80. else
  81. return (void *)(byteswap32_to_host(dynp->d_un.d_val) - tx_reloc + (char *)ehdr );
  82. }
  83. }
  84. return NULL;
  85. }
  86. int check_elf_header(Elf32_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_VERSION] != EV_CURRENT)
  91. {
  92. return 1;
  93. }
  94. /* Check if the target endianness matches the host's endianness */
  95. byteswap = 0;
  96. #if __BYTE_ORDER == __LITTLE_ENDIAN
  97. if (ehdr->e_ident[5] == ELFDATA2MSB) {
  98. /* Ick -- we will have to byte-swap everything */
  99. byteswap = 1;
  100. }
  101. #elif __BYTE_ORDER == __BIG_ENDIAN
  102. if (ehdr->e_ident[5] == ELFDATA2LSB) {
  103. byteswap = 1;
  104. }
  105. #else
  106. #error Unknown host byte order!
  107. #endif
  108. /* Be vary lazy, and only byteswap the stuff we use */
  109. if (byteswap==1) {
  110. ehdr->e_type=bswap_16(ehdr->e_type);
  111. ehdr->e_machine=bswap_16(ehdr->e_machine);
  112. ehdr->e_phoff=bswap_32(ehdr->e_phoff);
  113. ehdr->e_shoff=bswap_32(ehdr->e_shoff);
  114. ehdr->e_phnum=bswap_16(ehdr->e_phnum);
  115. ehdr->e_shnum=bswap_16(ehdr->e_shnum);
  116. }
  117. return 0;
  118. }
  119. #define ELFOSABI_NONE 0 /* UNIX System V ABI */
  120. #define ELFOSABI_HPUX 1 /* HP-UX operating system */
  121. #define ELFOSABI_NETBSD 2 /* NetBSD */
  122. #define ELFOSABI_LINUX 3 /* GNU/Linux */
  123. #define ELFOSABI_HURD 4 /* GNU/Hurd */
  124. #define ELFOSABI_SOLARIS 6 /* Solaris */
  125. #define ELFOSABI_AIX 7 /* AIX */
  126. #define ELFOSABI_IRIX 8 /* IRIX */
  127. #define ELFOSABI_FREEBSD 9 /* FreeBSD */
  128. #define ELFOSABI_TRU64 10 /* TRU64 UNIX */
  129. #define ELFOSABI_MODESTO 11 /* Novell Modesto */
  130. #define ELFOSABI_OPENBSD 12 /* OpenBSD */
  131. #define ELFOSABI_STANDALONE 255 /* Standalone (embedded) application */
  132. #define ELFOSABI_ARM 97 /* ARM */
  133. static void describe_elf_hdr(Elf32_Ehdr* ehdr)
  134. {
  135. char *tmp, *tmp1;
  136. switch (ehdr->e_type) {
  137. case ET_NONE: tmp = "None"; tmp1 = "NONE"; break;
  138. case ET_REL: tmp = "Relocatable File"; tmp1 = "REL"; break;
  139. case ET_EXEC: tmp = "Executable file"; tmp1 = "EXEC"; break;
  140. case ET_DYN: tmp = "Shared object file"; tmp1 = "DYN"; break;
  141. case ET_CORE: tmp = "Core file"; tmp1 = "CORE"; break;
  142. default:
  143. tmp = tmp1 = "Unknown";
  144. }
  145. printf( "Type:\t\t%s (%s)\n", tmp1, tmp);
  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_860: tmp="Intel 80860"; break;
  154. case EM_MIPS: tmp="MIPS R3000 big-endian"; break;
  155. case EM_S370: tmp="IBM System/370"; break;
  156. case EM_MIPS_RS3_LE: tmp="MIPS R3000 little-endian"; break;
  157. case EM_PARISC: tmp="HPPA"; break;
  158. case EM_VPP500: tmp="Fujitsu VPP500"; break;
  159. case EM_SPARC32PLUS: tmp="Sun's v8plus"; break;
  160. case EM_960: tmp="Intel 80960"; break;
  161. case EM_PPC: tmp="PowerPC"; break;
  162. case EM_PPC64: tmp="PowerPC 64-bit"; break;
  163. case EM_S390: tmp="IBM S390"; break;
  164. case EM_V800: tmp="NEC V800 series"; break;
  165. case EM_FR20: tmp="Fujitsu FR20"; break;
  166. case EM_RH32: tmp="TRW RH-32"; break;
  167. case EM_RCE: tmp="Motorola RCE"; break;
  168. case EM_ARM: tmp="ARM"; break;
  169. case EM_FAKE_ALPHA: tmp="Digital Alpha"; break;
  170. case EM_SH: tmp="Hitachi SH"; break;
  171. case EM_SPARCV9: tmp="SPARC v9 64-bit"; break;
  172. case EM_TRICORE: tmp="Siemens Tricore"; break;
  173. case EM_ARC: tmp="Argonaut RISC Core"; break;
  174. case EM_H8_300: tmp="Hitachi H8/300"; break;
  175. case EM_H8_300H: tmp="Hitachi H8/300H"; break;
  176. case EM_H8S: tmp="Hitachi H8S"; break;
  177. case EM_H8_500: tmp="Hitachi H8/500"; break;
  178. case EM_IA_64: tmp="Intel Merced"; break;
  179. case EM_MIPS_X: tmp="Stanford MIPS-X"; break;
  180. case EM_COLDFIRE: tmp="Motorola Coldfire"; break;
  181. case EM_68HC12: tmp="Motorola M68HC12"; break;
  182. case EM_MMA: tmp="Fujitsu MMA Multimedia Accelerator"; break;
  183. case EM_PCP: tmp="Siemens PCP"; break;
  184. case EM_NCPU: tmp="Sony nCPU embeeded RISC"; break;
  185. case EM_NDR1: tmp="Denso NDR1 microprocessor"; break;
  186. case EM_STARCORE: tmp="Motorola Start*Core processor"; break;
  187. case EM_ME16: tmp="Toyota ME16 processor"; break;
  188. case EM_ST100: tmp="STMicroelectronic ST100 processor"; break;
  189. case EM_TINYJ: tmp="Advanced Logic Corp. Tinyj emb.fam"; break;
  190. case EM_X86_64: tmp="AMD x86-64 architecture"; break;
  191. case EM_PDSP: tmp="Sony DSP Processor"; break;
  192. case EM_FX66: tmp="Siemens FX66 microcontroller"; break;
  193. case EM_ST9PLUS: tmp="STMicroelectronics ST9+ 8/16 mc"; break;
  194. case EM_ST7: tmp="STmicroelectronics ST7 8 bit mc"; break;
  195. case EM_68HC16: tmp="Motorola MC68HC16 microcontroller"; break;
  196. case EM_68HC11: tmp="Motorola MC68HC11 microcontroller"; break;
  197. case EM_68HC08: tmp="Motorola MC68HC08 microcontroller"; break;
  198. case EM_68HC05: tmp="Motorola MC68HC05 microcontroller"; break;
  199. case EM_SVX: tmp="Silicon Graphics SVx"; break;
  200. case EM_AT19: tmp="STMicroelectronics ST19 8 bit mc"; break;
  201. case EM_VAX: tmp="Digital VAX"; break;
  202. case EM_CRIS: tmp="Axis Communications 32-bit embedded processor"; break;
  203. case EM_JAVELIN: tmp="Infineon Technologies 32-bit embedded processor"; break;
  204. case EM_FIREPATH: tmp="Element 14 64-bit DSP Processor"; break;
  205. case EM_ZSP: tmp="LSI Logic 16-bit DSP Processor"; break;
  206. case EM_MMIX: tmp="Donald Knuth's educational 64-bit processor"; break;
  207. case EM_HUANY: tmp="Harvard University machine-independent object files"; break;
  208. case EM_PRISM: tmp="SiTera Prism"; break;
  209. case EM_AVR: tmp="Atmel AVR 8-bit microcontroller"; break;
  210. case EM_FR30: tmp="Fujitsu FR30"; break;
  211. case EM_D10V: tmp="Mitsubishi D10V"; break;
  212. case EM_D30V: tmp="Mitsubishi D30V"; break;
  213. case EM_V850: tmp="NEC v850"; break;
  214. case EM_M32R: tmp="Mitsubishi M32R"; break;
  215. case EM_MN10300: tmp="Matsushita MN10300"; break;
  216. case EM_MN10200: tmp="Matsushita MN10200"; break;
  217. case EM_PJ: tmp="picoJava"; break;
  218. default: tmp="unknown";
  219. }
  220. printf( "Machine:\t%s\n", tmp);
  221. switch (ehdr->e_ident[EI_CLASS]) {
  222. case ELFCLASSNONE: tmp = "Invalid class"; break;
  223. case ELFCLASS32: tmp = "ELF32"; break;
  224. case ELFCLASS64: tmp = "ELF64"; break;
  225. default: tmp = "Unknown";
  226. }
  227. printf( "Class:\t\t%s\n", tmp);
  228. switch (ehdr->e_ident[EI_DATA]) {
  229. case ELFDATANONE: tmp = "Invalid data encoding"; break;
  230. case ELFDATA2LSB: tmp = "2's complement, little endian"; break;
  231. case ELFDATA2MSB: tmp = "2's complement, big endian"; break;
  232. default: tmp = "Unknown";
  233. }
  234. printf( "Data:\t\t%s\n", tmp);
  235. printf( "Version:\t%d %s\n", ehdr->e_ident[EI_VERSION],
  236. (ehdr->e_ident[EI_VERSION]==EV_CURRENT)?
  237. "(current)" : "(unknown: %lx)");
  238. switch (ehdr->e_ident[EI_OSABI]) {
  239. case ELFOSABI_SYSV: tmp ="UNIX - System V"; break;
  240. case ELFOSABI_HPUX: tmp ="UNIX - HP-UX"; break;
  241. case ELFOSABI_NETBSD: tmp ="UNIX - NetBSD"; break;
  242. case ELFOSABI_LINUX: tmp ="UNIX - Linux"; break;
  243. case ELFOSABI_HURD: tmp ="GNU/Hurd"; break;
  244. case ELFOSABI_SOLARIS: tmp ="UNIX - Solaris"; break;
  245. case ELFOSABI_AIX: tmp ="UNIX - AIX"; break;
  246. case ELFOSABI_IRIX: tmp ="UNIX - IRIX"; break;
  247. case ELFOSABI_FREEBSD: tmp ="UNIX - FreeBSD"; break;
  248. case ELFOSABI_TRU64: tmp ="UNIX - TRU64"; break;
  249. case ELFOSABI_MODESTO: tmp ="Novell - Modesto"; break;
  250. case ELFOSABI_OPENBSD: tmp ="UNIX - OpenBSD"; break;
  251. case ELFOSABI_STANDALONE: tmp ="Standalone App"; break;
  252. case ELFOSABI_ARM: tmp ="ARM"; break;
  253. default: tmp = "Unknown";
  254. }
  255. printf( "OS/ABI:\t\t%s\n", tmp);
  256. printf( "ABI Version:\t%d\n", ehdr->e_ident[EI_ABIVERSION]);
  257. }
  258. static void list_needed_libraries(Elf32_Dyn* dynamic, char *strtab)
  259. {
  260. Elf32_Dyn *dyns;
  261. printf("Dependancies:\n");
  262. for (dyns=dynamic; byteswap32_to_host(dyns->d_tag)!=DT_NULL; ++dyns) {
  263. if (dyns->d_tag == DT_NEEDED) {
  264. printf("\t%s\n", (char*)strtab + byteswap32_to_host(dyns->d_un.d_val));
  265. }
  266. }
  267. }
  268. static void describe_elf_interpreter(Elf32_Ehdr* ehdr)
  269. {
  270. Elf32_Phdr *phdr;
  271. phdr = elf_find_phdr_type(PT_INTERP, ehdr);
  272. if (phdr) {
  273. printf("Interpreter:\t%s\n", (char*)ehdr + byteswap32_to_host(phdr->p_offset));
  274. }
  275. }
  276. int main( int argc, char** argv)
  277. {
  278. /* map the .so, and locate interesting pieces */
  279. char *dynstr;
  280. char *thefilename = argv[1];
  281. FILE *thefile;
  282. struct stat statbuf;
  283. Elf32_Ehdr *ehdr = 0;
  284. Elf32_Shdr *dynsec;
  285. Elf32_Dyn *dynamic;
  286. if (!thefilename) {
  287. fprintf(stderr, "No filename specified.\n");
  288. exit(EXIT_FAILURE);
  289. }
  290. if (!(thefile = fopen(thefilename, "r"))) {
  291. perror(thefilename);
  292. exit(EXIT_FAILURE);
  293. }
  294. if (fstat(fileno(thefile), &statbuf) < 0) {
  295. perror(thefilename);
  296. exit(EXIT_FAILURE);
  297. }
  298. if (statbuf.st_size < sizeof(Elf32_Ehdr))
  299. goto foo;
  300. /* mmap the file to make reading stuff from it effortless */
  301. ehdr = (Elf32_Ehdr *)mmap(0, statbuf.st_size,
  302. PROT_READ|PROT_WRITE, MAP_PRIVATE, fileno(thefile), 0);
  303. foo:
  304. /* Check if this looks legit */
  305. if (check_elf_header(ehdr)) {
  306. fprintf(stderr, "This does not appear to be an ELF file.\n");
  307. exit(EXIT_FAILURE);
  308. }
  309. describe_elf_hdr(ehdr);
  310. describe_elf_interpreter(ehdr);
  311. dynsec = elf_find_section_type(SHT_DYNAMIC, ehdr);
  312. if (dynsec) {
  313. dynamic = (Elf32_Dyn*)(byteswap32_to_host(dynsec->sh_offset) + (intptr_t)ehdr);
  314. dynstr = (char *)elf_find_dynamic(DT_STRTAB, dynamic, ehdr, 0);
  315. list_needed_libraries(dynamic, dynstr);
  316. }
  317. return 0;
  318. }