__uClibc_main.c 7.7 KB

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  1. /*
  2. * Copyright (C) Feb 2001 Manuel Novoa III
  3. * Copyright (C) 2000-2005 Erik Andersen <andersen@uclibc.org>
  4. *
  5. * Licensed under the LGPL v2.1, see the file COPYING.LIB in this tarball.
  6. *
  7. * __uClibc_main is the routine to be called by all the arch-specific
  8. * versions of crt1.S in uClibc.
  9. *
  10. * It is meant to handle any special initialization needed by the library
  11. * such as setting the global variable(s) __environ (environ) and
  12. * initializing the stdio package. Using weak symbols, the latter is
  13. * avoided in the static library case.
  14. */
  15. #define _ERRNO_H
  16. #include <features.h>
  17. #include <unistd.h>
  18. #include <stdlib.h>
  19. #include <string.h>
  20. #include <elf.h>
  21. #include <link.h>
  22. #include <bits/uClibc_page.h>
  23. #include <paths.h>
  24. #include <unistd.h>
  25. #include <asm/errno.h>
  26. #include <fcntl.h>
  27. #include <sys/stat.h>
  28. #include <sys/sysmacros.h>
  29. #ifndef SHARED
  30. void *__libc_stack_end=NULL;
  31. /* probably all the weak_*function stuff below should be in here */
  32. #ifdef __UCLIBC_HAS_SSP__
  33. #include <dl-osinfo.h>
  34. #ifndef THREAD_SET_STACK_GUARD
  35. /* Only exported for architectures that don't store the stack guard canary
  36. * in thread local area. */
  37. #include <stdint.h>
  38. /* for gcc-4.1 non-TLS */
  39. uintptr_t __stack_chk_guard attribute_relro;
  40. /* for gcc-3.x + Etoh ssp */
  41. strong_alias(__stack_chk_guard,__guard)
  42. #endif
  43. #endif
  44. #endif /* !SHARED */
  45. /*
  46. * Prototypes.
  47. */
  48. extern void weak_function _stdio_init(void);
  49. extern int *weak_const_function __errno_location(void);
  50. extern int *weak_const_function __h_errno_location(void);
  51. #ifdef __UCLIBC_HAS_LOCALE__
  52. extern void weak_function _locale_init(void);
  53. #endif
  54. #ifdef __UCLIBC_HAS_THREADS__
  55. extern void weak_function __pthread_initialize_minimal(void);
  56. #endif
  57. /*
  58. * Declare the __environ global variable and create a weak alias environ.
  59. * Note: Apparently we must initialize __environ to ensure that the weak
  60. * environ symbol is also included.
  61. */
  62. char **__environ = 0;
  63. weak_alias(__environ, environ);
  64. size_t __pagesize = 0;
  65. const char *__progname = 0;
  66. #ifndef O_NOFOLLOW
  67. # define O_NOFOLLOW 0
  68. #endif
  69. extern int __libc_fcntl(int fd, int cmd, ...);
  70. extern int __libc_open(const char *file, int flags, ...);
  71. static void __check_one_fd(int fd, int mode)
  72. {
  73. /* Check if the specified fd is already open */
  74. if (unlikely(__libc_fcntl(fd, F_GETFD)==-1 && *(__errno_location())==EBADF))
  75. {
  76. /* The descriptor is probably not open, so try to use /dev/null */
  77. struct stat st;
  78. int nullfd = __libc_open(_PATH_DEVNULL, mode);
  79. /* /dev/null is major=1 minor=3. Make absolutely certain
  80. * that is in fact the device that we have opened and not
  81. * some other wierd file... */
  82. if ( (nullfd!=fd) || fstat(fd, &st) || !S_ISCHR(st.st_mode) ||
  83. (st.st_rdev != makedev(1, 3)))
  84. {
  85. /* Somebody is trying some trickery here... */
  86. while (1) {
  87. abort();
  88. }
  89. }
  90. }
  91. }
  92. static int __check_suid(void)
  93. {
  94. uid_t uid, euid;
  95. gid_t gid, egid;
  96. uid = getuid();
  97. euid = geteuid();
  98. gid = getgid();
  99. egid = getegid();
  100. if(uid == euid && gid == egid) {
  101. return 0;
  102. }
  103. return 1;
  104. }
  105. /* __uClibc_init completely initialize uClibc so it is ready to use.
  106. *
  107. * On ELF systems (with a dynamic loader) this function must be called
  108. * from the dynamic loader (see TIS and ELF Specification), so that
  109. * constructors of shared libraries (which depend on libc) can use all
  110. * the libc code without restriction. For this we link the shared
  111. * version of the uClibc with -init __uClibc_init so DT_INIT for
  112. * uClibc is the address of __uClibc_init
  113. *
  114. * In all other cases we call it from the main stub
  115. * __uClibc_main.
  116. */
  117. void __uClibc_init(void)
  118. {
  119. static int been_there_done_that = 0;
  120. if (been_there_done_that)
  121. return;
  122. been_there_done_that++;
  123. /* Setup an initial value. This may not be perfect, but is
  124. * better than malloc using __pagesize=0 for atexit, ctors, etc. */
  125. __pagesize = PAGE_SIZE;
  126. #ifdef __UCLIBC_HAS_THREADS__
  127. /* Before we start initializing uClibc we have to call
  128. * __pthread_initialize_minimal so we can use pthread_locks
  129. * whenever they are needed.
  130. */
  131. if (likely(__pthread_initialize_minimal!=NULL))
  132. __pthread_initialize_minimal();
  133. #endif
  134. #ifndef SHARED
  135. # ifdef __UCLIBC_HAS_SSP__
  136. /* Set up the stack checker's canary. */
  137. uintptr_t stack_chk_guard = _dl_setup_stack_chk_guard();
  138. # ifdef THREAD_SET_STACK_GUARD
  139. THREAD_SET_STACK_GUARD (stack_chk_guard);
  140. # else
  141. __stack_chk_guard = stack_chk_guard;
  142. # endif
  143. # endif
  144. #endif
  145. #ifdef __UCLIBC_HAS_LOCALE__
  146. /* Initialize the global locale structure. */
  147. if (likely(_locale_init!=NULL))
  148. _locale_init();
  149. #endif
  150. /*
  151. * Initialize stdio here. In the static library case, this will
  152. * be bypassed if not needed because of the weak alias above.
  153. */
  154. if (likely(_stdio_init != NULL))
  155. _stdio_init();
  156. }
  157. #ifdef __UCLIBC_CTOR_DTOR__
  158. void attribute_hidden (*__app_fini)(void) = NULL;
  159. #endif
  160. void attribute_hidden (*__rtld_fini)(void) = NULL;
  161. /* __uClibc_main is the new main stub for uClibc. This function is
  162. * called from crt1 (version 0.9.28 or newer), after ALL shared libraries
  163. * are initialized, just before we call the application's main function.
  164. */
  165. void __attribute__ ((__noreturn__))
  166. __uClibc_main(int (*main)(int, char **, char **), int argc,
  167. char **argv, void (*app_init)(void), void (*app_fini)(void),
  168. void (*rtld_fini)(void), void *stack_end)
  169. {
  170. #ifdef __ARCH_HAS_MMU__
  171. unsigned long *aux_dat;
  172. ElfW(auxv_t) auxvt[AT_EGID + 1];
  173. #endif
  174. #ifndef SHARED
  175. __libc_stack_end = stack_end;
  176. #endif
  177. __rtld_fini = rtld_fini;
  178. /* The environment begins right after argv. */
  179. __environ = &argv[argc + 1];
  180. /* If the first thing after argv is the arguments
  181. * the the environment is empty. */
  182. if ((char *) __environ == *argv) {
  183. /* Make __environ point to the NULL at argv[argc] */
  184. __environ = &argv[argc];
  185. }
  186. /* Pull stuff from the ELF header when possible */
  187. #ifdef __ARCH_HAS_MMU__
  188. aux_dat = (unsigned long*)__environ;
  189. while (*aux_dat) {
  190. aux_dat++;
  191. }
  192. aux_dat++;
  193. while (*aux_dat) {
  194. ElfW(auxv_t) *auxv_entry = (ElfW(auxv_t) *) aux_dat;
  195. if (auxv_entry->a_type <= AT_EGID) {
  196. memcpy(&(auxvt[auxv_entry->a_type]), auxv_entry, sizeof(ElfW(auxv_t)));
  197. }
  198. aux_dat += 2;
  199. }
  200. /* We need to initialize uClibc. If we are dynamically linked this
  201. * may have already been completed by the shared lib loader. We call
  202. * __uClibc_init() regardless, to be sure the right thing happens. */
  203. __uClibc_init();
  204. /* Make certain getpagesize() gives the correct answer */
  205. __pagesize = (auxvt[AT_PAGESZ].a_un.a_val)? auxvt[AT_PAGESZ].a_un.a_val : PAGE_SIZE;
  206. /* Prevent starting SUID binaries where the stdin. stdout, and
  207. * stderr file descriptors are not already opened. */
  208. if ((auxvt[AT_UID].a_un.a_val==-1 && __check_suid()) ||
  209. (auxvt[AT_UID].a_un.a_val != -1 &&
  210. (auxvt[AT_UID].a_un.a_val != auxvt[AT_EUID].a_un.a_val ||
  211. auxvt[AT_GID].a_un.a_val != auxvt[AT_EGID].a_un.a_val)))
  212. {
  213. __check_one_fd (STDIN_FILENO, O_RDONLY | O_NOFOLLOW);
  214. __check_one_fd (STDOUT_FILENO, O_RDWR | O_NOFOLLOW);
  215. __check_one_fd (STDERR_FILENO, O_RDWR | O_NOFOLLOW);
  216. }
  217. #endif
  218. __progname = *argv;
  219. #ifdef __UCLIBC_CTOR_DTOR__
  220. /* Arrange for the application's dtors to run before we exit. */
  221. __app_fini = app_fini;
  222. /* Run all the application's ctors now. */
  223. if (app_init!=NULL) {
  224. app_init();
  225. }
  226. #endif
  227. /* Note: It is possible that any initialization done above could
  228. * have resulted in errno being set nonzero, so set it to 0 before
  229. * we call main.
  230. */
  231. if (likely(__errno_location!=NULL))
  232. *(__errno_location()) = 0;
  233. /* Set h_errno to 0 as well */
  234. if (likely(__h_errno_location!=NULL))
  235. *(__h_errno_location()) = 0;
  236. /*
  237. * Finally, invoke application's main and then exit.
  238. */
  239. exit(main(argc, argv, __environ));
  240. }