__uClibc_main.c 7.8 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 getgid __getgid
  16. #define getuid __getuid
  17. #define getegid __getegid
  18. #define geteuid __geteuid
  19. #define _ERRNO_H
  20. #include <features.h>
  21. #include <unistd.h>
  22. #include <stdlib.h>
  23. #include <string.h>
  24. #include <elf.h>
  25. #include <link.h>
  26. #include <bits/uClibc_page.h>
  27. #include <paths.h>
  28. #include <unistd.h>
  29. #include <asm/errno.h>
  30. #include <fcntl.h>
  31. #include <sys/stat.h>
  32. #include <sys/sysmacros.h>
  33. #ifndef SHARED
  34. void *__libc_stack_end=NULL;
  35. /* probably all the weak_*function stuff below should be in here */
  36. #ifdef __UCLIBC_HAS_SSP__
  37. #include <dl-osinfo.h>
  38. #ifndef THREAD_SET_STACK_GUARD
  39. /* Only exported for architectures that don't store the stack guard canary
  40. * in thread local area. */
  41. #include <stdint.h>
  42. /* for gcc-4.1 non-TLS */
  43. uintptr_t __stack_chk_guard attribute_relro;
  44. /* for gcc-3.x + Etoh ssp */
  45. strong_alias(__stack_chk_guard,__guard)
  46. #endif
  47. #endif
  48. #endif /* !SHARED */
  49. /*
  50. * Prototypes.
  51. */
  52. extern void weak_function _stdio_init(void);
  53. extern int *weak_const_function __errno_location(void);
  54. extern int *weak_const_function __h_errno_location(void);
  55. #ifdef __UCLIBC_HAS_LOCALE__
  56. extern void weak_function _locale_init(void);
  57. #endif
  58. #ifdef __UCLIBC_HAS_THREADS__
  59. extern void weak_function __pthread_initialize_minimal(void);
  60. #endif
  61. /*
  62. * Declare the __environ global variable and create a weak alias environ.
  63. * Note: Apparently we must initialize __environ to ensure that the weak
  64. * environ symbol is also included.
  65. */
  66. char **__environ = 0;
  67. weak_alias(__environ, environ);
  68. size_t __pagesize = 0;
  69. const char *__progname = 0;
  70. #ifndef O_NOFOLLOW
  71. # define O_NOFOLLOW 0
  72. #endif
  73. extern int __libc_fcntl(int fd, int cmd, ...);
  74. #ifdef __ARCH_HAS_MMU__
  75. static void __check_one_fd(int fd, int mode)
  76. {
  77. /* Check if the specified fd is already open */
  78. if (unlikely(__libc_fcntl(fd, F_GETFD)==-1 && *(__errno_location())==EBADF))
  79. {
  80. /* The descriptor is probably not open, so try to use /dev/null */
  81. struct stat st;
  82. int nullfd = __open(_PATH_DEVNULL, mode);
  83. /* /dev/null is major=1 minor=3. Make absolutely certain
  84. * that is in fact the device that we have opened and not
  85. * some other wierd file... */
  86. if ( (nullfd!=fd) || fstat(fd, &st) || !S_ISCHR(st.st_mode) ||
  87. (st.st_rdev != makedev(1, 3)))
  88. {
  89. /* Somebody is trying some trickery here... */
  90. while (1) {
  91. abort();
  92. }
  93. }
  94. }
  95. }
  96. static int __check_suid(void)
  97. {
  98. uid_t uid, euid;
  99. gid_t gid, egid;
  100. uid = getuid();
  101. euid = geteuid();
  102. gid = getgid();
  103. egid = getegid();
  104. if(uid == euid && gid == egid) {
  105. return 0;
  106. }
  107. return 1;
  108. }
  109. #endif
  110. /* __uClibc_init completely initialize uClibc so it is ready to use.
  111. *
  112. * On ELF systems (with a dynamic loader) this function must be called
  113. * from the dynamic loader (see TIS and ELF Specification), so that
  114. * constructors of shared libraries (which depend on libc) can use all
  115. * the libc code without restriction. For this we link the shared
  116. * version of the uClibc with -init __uClibc_init so DT_INIT for
  117. * uClibc is the address of __uClibc_init
  118. *
  119. * In all other cases we call it from the main stub
  120. * __uClibc_main.
  121. */
  122. void __uClibc_init(void)
  123. {
  124. static int been_there_done_that = 0;
  125. if (been_there_done_that)
  126. return;
  127. been_there_done_that++;
  128. /* Setup an initial value. This may not be perfect, but is
  129. * better than malloc using __pagesize=0 for atexit, ctors, etc. */
  130. __pagesize = PAGE_SIZE;
  131. #ifdef __UCLIBC_HAS_THREADS__
  132. /* Before we start initializing uClibc we have to call
  133. * __pthread_initialize_minimal so we can use pthread_locks
  134. * whenever they are needed.
  135. */
  136. if (likely(__pthread_initialize_minimal!=NULL))
  137. __pthread_initialize_minimal();
  138. #endif
  139. #ifndef SHARED
  140. # ifdef __UCLIBC_HAS_SSP__
  141. /* Set up the stack checker's canary. */
  142. uintptr_t stack_chk_guard = _dl_setup_stack_chk_guard();
  143. # ifdef THREAD_SET_STACK_GUARD
  144. THREAD_SET_STACK_GUARD (stack_chk_guard);
  145. # else
  146. __stack_chk_guard = stack_chk_guard;
  147. # endif
  148. # endif
  149. #endif
  150. #ifdef __UCLIBC_HAS_LOCALE__
  151. /* Initialize the global locale structure. */
  152. if (likely(_locale_init!=NULL))
  153. _locale_init();
  154. #endif
  155. /*
  156. * Initialize stdio here. In the static library case, this will
  157. * be bypassed if not needed because of the weak alias above.
  158. */
  159. if (likely(_stdio_init != NULL))
  160. _stdio_init();
  161. }
  162. #ifdef __UCLIBC_CTOR_DTOR__
  163. void attribute_hidden (*__app_fini)(void) = NULL;
  164. #endif
  165. void attribute_hidden (*__rtld_fini)(void) = NULL;
  166. /* __uClibc_main is the new main stub for uClibc. This function is
  167. * called from crt1 (version 0.9.28 or newer), after ALL shared libraries
  168. * are initialized, just before we call the application's main function.
  169. */
  170. void __attribute__ ((__noreturn__))
  171. __uClibc_main(int (*main)(int, char **, char **), int argc,
  172. char **argv, void (*app_init)(void), void (*app_fini)(void),
  173. void (*rtld_fini)(void), void *stack_end)
  174. {
  175. #ifdef __ARCH_HAS_MMU__
  176. unsigned long *aux_dat;
  177. ElfW(auxv_t) auxvt[AT_EGID + 1];
  178. #endif
  179. #ifndef SHARED
  180. __libc_stack_end = stack_end;
  181. #endif
  182. __rtld_fini = rtld_fini;
  183. /* The environment begins right after argv. */
  184. __environ = &argv[argc + 1];
  185. /* If the first thing after argv is the arguments
  186. * the the environment is empty. */
  187. if ((char *) __environ == *argv) {
  188. /* Make __environ point to the NULL at argv[argc] */
  189. __environ = &argv[argc];
  190. }
  191. /* Pull stuff from the ELF header when possible */
  192. #ifdef __ARCH_HAS_MMU__
  193. aux_dat = (unsigned long*)__environ;
  194. while (*aux_dat) {
  195. aux_dat++;
  196. }
  197. aux_dat++;
  198. while (*aux_dat) {
  199. ElfW(auxv_t) *auxv_entry = (ElfW(auxv_t) *) aux_dat;
  200. if (auxv_entry->a_type <= AT_EGID) {
  201. __memcpy(&(auxvt[auxv_entry->a_type]), auxv_entry, sizeof(ElfW(auxv_t)));
  202. }
  203. aux_dat += 2;
  204. }
  205. /* We need to initialize uClibc. If we are dynamically linked this
  206. * may have already been completed by the shared lib loader. We call
  207. * __uClibc_init() regardless, to be sure the right thing happens. */
  208. __uClibc_init();
  209. /* Make certain getpagesize() gives the correct answer */
  210. __pagesize = (auxvt[AT_PAGESZ].a_un.a_val)? auxvt[AT_PAGESZ].a_un.a_val : PAGE_SIZE;
  211. /* Prevent starting SUID binaries where the stdin. stdout, and
  212. * stderr file descriptors are not already opened. */
  213. if ((auxvt[AT_UID].a_un.a_val==-1 && __check_suid()) ||
  214. (auxvt[AT_UID].a_un.a_val != -1 &&
  215. (auxvt[AT_UID].a_un.a_val != auxvt[AT_EUID].a_un.a_val ||
  216. auxvt[AT_GID].a_un.a_val != auxvt[AT_EGID].a_un.a_val)))
  217. {
  218. __check_one_fd (STDIN_FILENO, O_RDONLY | O_NOFOLLOW);
  219. __check_one_fd (STDOUT_FILENO, O_RDWR | O_NOFOLLOW);
  220. __check_one_fd (STDERR_FILENO, O_RDWR | O_NOFOLLOW);
  221. }
  222. #endif
  223. __progname = *argv;
  224. #ifdef __UCLIBC_CTOR_DTOR__
  225. /* Arrange for the application's dtors to run before we exit. */
  226. __app_fini = app_fini;
  227. /* Run all the application's ctors now. */
  228. if (app_init!=NULL) {
  229. app_init();
  230. }
  231. #endif
  232. /* Note: It is possible that any initialization done above could
  233. * have resulted in errno being set nonzero, so set it to 0 before
  234. * we call main.
  235. */
  236. if (likely(__errno_location!=NULL))
  237. *(__errno_location()) = 0;
  238. /* Set h_errno to 0 as well */
  239. if (likely(__h_errno_location!=NULL))
  240. *(__h_errno_location()) = 0;
  241. /*
  242. * Finally, invoke application's main and then exit.
  243. */
  244. exit(main(argc, argv, __environ));
  245. }