elfinterp.c 10 KB

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  1. /* vi: set sw=4 ts=4: */
  2. /* ARM ELF shared library loader suppport
  3. *
  4. * Copyright (C) 2001-2004 Erik Andersen
  5. *
  6. * All rights reserved.
  7. *
  8. * Redistribution and use in source and binary forms, with or without
  9. * modification, are permitted provided that the following conditions
  10. * are met:
  11. * 1. Redistributions of source code must retain the above copyright
  12. * notice, this list of conditions and the following disclaimer.
  13. * 2. The name of the above contributors may not be
  14. * used to endorse or promote products derived from this software
  15. * without specific prior written permission.
  16. *
  17. * THIS SOFTWARE IS PROVIDED BY THE CONTRIBUTORS ``AS IS'' AND
  18. * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19. * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20. * ARE DISCLAIMED. IN NO EVENT SHALL THE CONTRIBUTORS BE LIABLE
  21. * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22. * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23. * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24. * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25. * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26. * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27. * SUCH DAMAGE.
  28. */
  29. /* Program to load an ELF binary on a linux system, and run it.
  30. References to symbols in sharable libraries can be resolved by either
  31. an ELF sharable library or a linux style of shared library. */
  32. /* Disclaimer: I have never seen any AT&T source code for SVr4, nor have
  33. I ever taken any courses on internals. This program was developed using
  34. information available through the book "UNIX SYSTEM V RELEASE 4,
  35. Programmers guide: Ansi C and Programming Support Tools", which did
  36. a more than adequate job of explaining everything required to get this
  37. working. */
  38. #include "ldso.h"
  39. extern int _dl_linux_resolve(void);
  40. unsigned long _dl_linux_resolver(struct elf_resolve *tpnt, int reloc_entry)
  41. {
  42. ELF_RELOC *this_reloc;
  43. char *strtab;
  44. char *symname;
  45. ElfW(Sym) *symtab;
  46. ELF_RELOC *rel_addr;
  47. int symtab_index;
  48. unsigned long new_addr;
  49. char **got_addr;
  50. unsigned long instr_addr;
  51. rel_addr = (ELF_RELOC *) tpnt->dynamic_info[DT_JMPREL];
  52. this_reloc = rel_addr + reloc_entry;
  53. symtab_index = ELF_R_SYM(this_reloc->r_info);
  54. symtab = (ElfW(Sym) *) tpnt->dynamic_info[DT_SYMTAB];
  55. strtab = (char *) tpnt->dynamic_info[DT_STRTAB];
  56. symname = strtab + symtab[symtab_index].st_name;
  57. /* Address of jump instruction to fix up */
  58. instr_addr = ((unsigned long) this_reloc->r_offset +
  59. (unsigned long) tpnt->loadaddr);
  60. got_addr = (char **) instr_addr;
  61. /* Get the address of the GOT entry */
  62. new_addr = (unsigned long)_dl_find_hash(symname, &_dl_loaded_modules->symbol_scope,
  63. tpnt, ELF_RTYPE_CLASS_PLT, NULL);
  64. if (unlikely(!new_addr)) {
  65. _dl_dprintf(2, "%s: can't resolve symbol '%s'\n",
  66. _dl_progname, symname);
  67. _dl_exit(1);
  68. }
  69. #if defined (__SUPPORT_LD_DEBUG__)
  70. # if !defined __SUPPORT_LD_DEBUG_EARLY__
  71. if ((unsigned long) got_addr < 0x40000000)
  72. # endif
  73. {
  74. if (_dl_debug_bindings)
  75. {
  76. _dl_dprintf(_dl_debug_file, "\nresolve function: %s", symname);
  77. if (_dl_debug_detail) _dl_dprintf(_dl_debug_file,
  78. "\tpatch %x ==> %x @ %x", *got_addr, new_addr, got_addr);
  79. }
  80. }
  81. if (!_dl_debug_nofixups) {
  82. *got_addr = (char *)new_addr;
  83. }
  84. #else
  85. *got_addr = (char *)new_addr;
  86. #endif
  87. return new_addr;
  88. }
  89. static int
  90. _dl_parse(struct elf_resolve *tpnt, struct r_scope_elem *scope,
  91. unsigned long rel_addr, unsigned long rel_size,
  92. int (*reloc_fnc) (struct elf_resolve *tpnt, struct r_scope_elem *scope,
  93. ELF_RELOC *rpnt, ElfW(Sym) *symtab, char *strtab))
  94. {
  95. int i;
  96. char *strtab;
  97. int goof = 0;
  98. ElfW(Sym) *symtab;
  99. ELF_RELOC *rpnt;
  100. int symtab_index;
  101. /* Now parse the relocation information */
  102. rpnt = (ELF_RELOC *) rel_addr;
  103. rel_size = rel_size / sizeof(ELF_RELOC);
  104. symtab = (ElfW(Sym) *) tpnt->dynamic_info[DT_SYMTAB];
  105. strtab = (char *) tpnt->dynamic_info[DT_STRTAB];
  106. for (i = 0; i < rel_size; i++, rpnt++) {
  107. int res;
  108. symtab_index = ELF_R_SYM(rpnt->r_info);
  109. debug_sym(symtab,strtab,symtab_index);
  110. debug_reloc(symtab,strtab,rpnt);
  111. res = reloc_fnc (tpnt, scope, rpnt, symtab, strtab);
  112. if (res==0) continue;
  113. _dl_dprintf(2, "\n%s: ",_dl_progname);
  114. if (symtab_index)
  115. _dl_dprintf(2, "symbol '%s': ", strtab + symtab[symtab_index].st_name);
  116. if (unlikely(res <0))
  117. {
  118. int reloc_type = ELF_R_TYPE(rpnt->r_info);
  119. #if defined (__SUPPORT_LD_DEBUG__)
  120. _dl_dprintf(2, "can't handle reloc type %s\n ", _dl_reltypes(reloc_type));
  121. #else
  122. _dl_dprintf(2, "can't handle reloc type %x\n", reloc_type);
  123. #endif
  124. _dl_exit(-res);
  125. }
  126. if (unlikely(res >0))
  127. {
  128. _dl_dprintf(2, "can't resolve symbol\n");
  129. goof += res;
  130. }
  131. }
  132. return goof;
  133. }
  134. #if 0
  135. static unsigned long
  136. fix_bad_pc24 (unsigned long *const reloc_addr, unsigned long value)
  137. {
  138. static void *fix_page;
  139. static unsigned int fix_offset;
  140. unsigned int *fix_address;
  141. if (! fix_page)
  142. {
  143. fix_page = _dl_mmap (NULL, PAGE_SIZE , PROT_READ | PROT_WRITE | PROT_EXEC,
  144. MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
  145. fix_offset = 0;
  146. }
  147. fix_address = (unsigned int *)(fix_page + fix_offset);
  148. fix_address[0] = 0xe51ff004; /* ldr pc, [pc, #-4] */
  149. fix_address[1] = value;
  150. fix_offset += 8;
  151. if (fix_offset >= PAGE_SIZE)
  152. fix_page = NULL;
  153. return (unsigned long)fix_address;
  154. }
  155. #endif
  156. static int
  157. _dl_do_reloc (struct elf_resolve *tpnt,struct r_scope_elem *scope,
  158. ELF_RELOC *rpnt, ElfW(Sym) *symtab, char *strtab)
  159. {
  160. int reloc_type;
  161. int symtab_index;
  162. char *symname;
  163. unsigned long *reloc_addr;
  164. unsigned long symbol_addr;
  165. struct symbol_ref sym_ref;
  166. struct elf_resolve *def_mod = 0;
  167. int goof = 0;
  168. reloc_addr = (unsigned long *) (tpnt->loadaddr + (unsigned long) rpnt->r_offset);
  169. reloc_type = ELF_R_TYPE(rpnt->r_info);
  170. symtab_index = ELF_R_SYM(rpnt->r_info);
  171. symbol_addr = 0;
  172. sym_ref.sym = &symtab[symtab_index];
  173. sym_ref.tpnt = NULL;
  174. symname = strtab + symtab[symtab_index].st_name;
  175. if (symtab_index) {
  176. symbol_addr = (unsigned long)_dl_find_hash(symname, scope, tpnt,
  177. elf_machine_type_class(reloc_type), &sym_ref);
  178. /*
  179. * We want to allow undefined references to weak symbols - this might
  180. * have been intentional. We should not be linking local symbols
  181. * here, so all bases should be covered.
  182. */
  183. if (!symbol_addr && (ELF_ST_TYPE(symtab[symtab_index].st_info) != STT_TLS)
  184. && (ELF_ST_BIND(symtab[symtab_index].st_info) != STB_WEAK)) {
  185. /* This may be non-fatal if called from dlopen. */
  186. return 1;
  187. }
  188. if (_dl_trace_prelink) {
  189. _dl_debug_lookup (symname, tpnt, &symtab[symtab_index],
  190. &sym_ref, elf_machine_type_class(reloc_type));
  191. }
  192. def_mod = sym_ref.tpnt;
  193. } else {
  194. /*
  195. * Relocs against STN_UNDEF are usually treated as using a
  196. * symbol value of zero, and using the module containing the
  197. * reloc itself.
  198. */
  199. symbol_addr = symtab[symtab_index].st_value;
  200. def_mod = tpnt;
  201. }
  202. #if defined (__SUPPORT_LD_DEBUG__)
  203. {
  204. unsigned long old_val = *reloc_addr;
  205. #endif
  206. switch (reloc_type) {
  207. case R_ARM_NONE:
  208. break;
  209. case R_ARM_ABS32:
  210. *reloc_addr += symbol_addr;
  211. break;
  212. case R_ARM_PC24:
  213. #if 0
  214. {
  215. unsigned long addend;
  216. long newvalue, topbits;
  217. addend = *reloc_addr & 0x00ffffff;
  218. if (addend & 0x00800000) addend |= 0xff000000;
  219. newvalue = symbol_addr - (unsigned long)reloc_addr + (addend << 2);
  220. topbits = newvalue & 0xfe000000;
  221. if (topbits != 0xfe000000 && topbits != 0x00000000)
  222. {
  223. newvalue = fix_bad_pc24(reloc_addr, symbol_addr)
  224. - (unsigned long)reloc_addr + (addend << 2);
  225. topbits = newvalue & 0xfe000000;
  226. if (unlikely(topbits != 0xfe000000 && topbits != 0x00000000))
  227. {
  228. _dl_dprintf(2,"symbol '%s': R_ARM_PC24 relocation out of range.",
  229. symtab[symtab_index].st_name);
  230. _dl_exit(1);
  231. }
  232. }
  233. newvalue >>= 2;
  234. symbol_addr = (*reloc_addr & 0xff000000) | (newvalue & 0x00ffffff);
  235. *reloc_addr = symbol_addr;
  236. break;
  237. }
  238. #else
  239. _dl_dprintf(2,"R_ARM_PC24: Compile shared libraries with -fPIC!\n");
  240. _dl_exit(1);
  241. #endif
  242. case R_ARM_GLOB_DAT:
  243. case R_ARM_JUMP_SLOT:
  244. *reloc_addr = symbol_addr;
  245. break;
  246. case R_ARM_RELATIVE:
  247. *reloc_addr += (unsigned long) tpnt->loadaddr;
  248. break;
  249. case R_ARM_COPY:
  250. _dl_memcpy((void *) reloc_addr,
  251. (void *) symbol_addr, symtab[symtab_index].st_size);
  252. break;
  253. #if defined USE_TLS && USE_TLS
  254. case R_ARM_TLS_DTPMOD32:
  255. *reloc_addr = def_mod->l_tls_modid;
  256. break;
  257. case R_ARM_TLS_DTPOFF32:
  258. *reloc_addr += symbol_addr;
  259. break;
  260. case R_ARM_TLS_TPOFF32:
  261. CHECK_STATIC_TLS ((struct link_map *) def_mod);
  262. *reloc_addr += (symbol_addr + def_mod->l_tls_offset);
  263. break;
  264. #endif
  265. default:
  266. return -1; /*call _dl_exit(1) */
  267. }
  268. #if defined (__SUPPORT_LD_DEBUG__)
  269. if (_dl_debug_reloc && _dl_debug_detail)
  270. _dl_dprintf(_dl_debug_file, "\tpatch: %x ==> %x @ %x", old_val, *reloc_addr, reloc_addr);
  271. }
  272. #endif
  273. return goof;
  274. }
  275. static int
  276. _dl_do_lazy_reloc (struct elf_resolve *tpnt, struct r_scope_elem *scope,
  277. ELF_RELOC *rpnt, ElfW(Sym) *symtab, char *strtab)
  278. {
  279. int reloc_type;
  280. unsigned long *reloc_addr;
  281. reloc_addr = (unsigned long *) (tpnt->loadaddr + (unsigned long) rpnt->r_offset);
  282. reloc_type = ELF_R_TYPE(rpnt->r_info);
  283. #if defined (__SUPPORT_LD_DEBUG__)
  284. {
  285. unsigned long old_val = *reloc_addr;
  286. #endif
  287. switch (reloc_type) {
  288. case R_ARM_NONE:
  289. break;
  290. case R_ARM_JUMP_SLOT:
  291. *reloc_addr += (unsigned long) tpnt->loadaddr;
  292. break;
  293. default:
  294. return -1; /*call _dl_exit(1) */
  295. }
  296. #if defined (__SUPPORT_LD_DEBUG__)
  297. if (_dl_debug_reloc && _dl_debug_detail)
  298. _dl_dprintf(_dl_debug_file, "\tpatch: %x ==> %x @ %x", old_val, *reloc_addr, reloc_addr);
  299. }
  300. #endif
  301. return 0;
  302. }
  303. void _dl_parse_lazy_relocation_information(struct dyn_elf *rpnt,
  304. unsigned long rel_addr, unsigned long rel_size)
  305. {
  306. (void)_dl_parse(rpnt->dyn, NULL, rel_addr, rel_size, _dl_do_lazy_reloc);
  307. }
  308. int _dl_parse_relocation_information(struct dyn_elf *rpnt,
  309. struct r_scope_elem *scope, unsigned long rel_addr, unsigned long rel_size)
  310. {
  311. return _dl_parse(rpnt->dyn, scope, rel_addr, rel_size, _dl_do_reloc);
  312. }