libc/misc/internals/__uClibc_main.c

   1 /*
   2  * Copyright (C) 2006 by Steven J. Hill <sjhill@realitydiluted.com>
   3  * Copyright (C) 2001 by Manuel Novoa III <mjn3@uclibc.org>
   4  * Copyright (C) 2000-2005 Erik Andersen <andersen@uclibc.org>
   5  *
   6  * Licensed under the LGPL v2.1, see the file COPYING.LIB in this tarball.
   7  *
   8  * __uClibc_main is the routine to be called by all the arch-specific
   9  * versions of crt1.S in uClibc.
  10  *
  11  * It is meant to handle any special initialization needed by the library
  12  * such as setting the global variable(s) __environ (environ) and
  13  * initializing the stdio package.  Using weak symbols, the latter is
  14  * avoided in the static library case.
  15  */
  16
  17 #include <features.h>
  18 #include <unistd.h>
  19 #include <stdlib.h>
  20 #include <string.h>
  21 #include <elf.h>
  22 #include <link.h>
  23 #include <bits/uClibc_page.h>
  24 #include <paths.h>
  25 #include <errno.h>
  26 #include <netdb.h>
  27 #include <stdio.h>
  28 #ifndef __ARCH_HAS_NO_LDSO__
  29 #include <fcntl.h>
  30 #endif
  31 #ifdef __UCLIBC_HAS_THREADS_NATIVE__
  32 #include <not-cancel.h>
  33 #include <atomic.h>
  34 #include <tls.h>
  35 #endif
  36 #ifdef __UCLIBC_HAS_THREADS__
  37 #include <pthread.h>
  38 #endif
  39 #ifdef __UCLIBC_HAS_LOCALE__
  40 #include <locale.h>
  41 #endif
  42
  43 /* Are we in a secure process environment or are we dealing
  44  * with setuid stuff?  If we are dynamically linked, then we
  45  * already have _dl_secure, otherwise we need to re-examine
  46  * auxvt[] below.
  47  */
  48 int _pe_secure = 0;
  49 libc_hidden_data_def(_pe_secure)
  50
  51 #if !defined(SHARED) && defined(__FDPIC__)
  52 struct funcdesc_value
  53 {
  54         void *entry_point;
  55         void *got_value;
  56 } __attribute__((__aligned__(8)));
  57
  58
  59 /* Prevent compiler optimization that removes GOT assignment.
  60
  61   Due to optimization passes (block split and move), in the rare case
  62   where use r9 is the single instruction in a block we can have the
  63   following behaviour:
  64   - this block is marked as a forward block since use is not
  65   considered as an active instruction after reload pass.
  66
  67   - In this case a jump in this block can be moved to the start of the
  68   next one and so remove use in this flow of instructions which can
  69   lead to a removal of r9 restoration after a call. */
  70 #define _dl_stabilize_funcdesc(val)                     \
  71         ({ __asm__ ("" : "+m" (*(val))); (val); })
  72
  73 static void fdpic_init_array_jump(void *addr)
  74 {
  75         struct funcdesc_value *fm = (struct funcdesc_value *) fdpic_init_array_jump;
  76         struct funcdesc_value fd = {addr, fm->got_value};
  77
  78         void (*pf)(void) = (void*) _dl_stabilize_funcdesc(&fd);
  79
  80         (*pf)();
  81 }
  82 #endif
  83
  84 #ifndef SHARED
  85 void *__libc_stack_end = NULL;
  86
  87 # ifdef __UCLIBC_HAS_SSP__
  88 #  include <dl-osinfo.h>
  89 static uintptr_t stack_chk_guard;
  90 #  ifndef THREAD_SET_STACK_GUARD
  91 /* Only exported for architectures that don't store the stack guard canary
  92  * in thread local area. */
  93 /* for gcc-4.1 non-TLS */
  94 uintptr_t __stack_chk_guard attribute_relro;
  95 #  endif
  96 # endif
  97
  98 /*
  99  * Needed to initialize _dl_phdr when statically linked
 100  */
 101
 102 void internal_function _dl_aux_init (ElfW(auxv_t) *av);
 103
 104 #ifdef __UCLIBC_HAS_THREADS__
 105 /*
 106  * uClibc internal locking requires that we have weak aliases
 107  * for dummy functions in case a single threaded application is linked.
 108  * This needs to be in compilation unit that is pulled always
 109  * in or linker will disregard these weaks.
 110  */
 111
 112 static int __pthread_return_0 (pthread_mutex_t *unused) { (void)unused; return 0; }
 113 weak_alias (__pthread_return_0, __pthread_mutex_lock)
 114 weak_alias (__pthread_return_0, __pthread_mutex_trylock)
 115 weak_alias (__pthread_return_0, __pthread_mutex_unlock)
 116
 117 int weak_function
 118 __pthread_mutex_init(pthread_mutex_t *mutex, const pthread_mutexattr_t *attr)
 119 {
 120         (void)mutex; (void)attr;
 121         return 0;
 122 }
 123
 124 void weak_function
 125 _pthread_cleanup_push_defer(struct _pthread_cleanup_buffer *__buffer,
 126                             void (*__routine) (void *), void *__arg)
 127 {
 128         __buffer->__routine = __routine;
 129         __buffer->__arg = __arg;
 130 }
 131
 132 void weak_function
 133 _pthread_cleanup_pop_restore(struct _pthread_cleanup_buffer *__buffer,
 134                              int __execute)
 135 {
 136         if (__execute)
 137                 __buffer->__routine(__buffer->__arg);
 138 }
 139
 140 #endif /* __UCLIBC_HAS_THREADS__ */
 141
 142 #endif /* !SHARED */
 143
 144 /* Defeat compiler optimization which assumes function addresses are never NULL */
 145 static __always_inline int not_null_ptr(const void *p)
 146 {
 147         const void *q;
 148         __asm__ (""
 149                 : "=r" (q) /* output */
 150                 : "0" (p) /* input */
 151         );
 152         return q != 0;
 153 }
 154
 155 /*
 156  * Prototypes.
 157  */
 158 #ifdef __UCLIBC_HAS_THREADS__
 159 #if !defined (__UCLIBC_HAS_THREADS_NATIVE__) || defined (SHARED)
 160 extern void weak_function __pthread_initialize_minimal(void);
 161 #else
 162 extern void __pthread_initialize_minimal(void);
 163 #endif
 164 #endif
 165
 166 #ifndef SHARED
 167 extern void __libc_setup_tls (size_t tcbsize, size_t tcbalign);
 168 #endif
 169
 170 /* If __UCLIBC_FORMAT_SHARED_FLAT__, all array initialisation and finalisation
 171  * is handled by the routines passed to __uClibc_main().  */
 172 #if defined (__UCLIBC_CTOR_DTOR__) && !defined (__UCLIBC_FORMAT_SHARED_FLAT__)
 173 extern void _dl_app_init_array(void);
 174 extern void _dl_app_fini_array(void);
 175 # ifndef SHARED
 176 /* These magic symbols are provided by the linker.  */
 177 extern void (*__preinit_array_start []) (void) attribute_hidden;
 178 extern void (*__preinit_array_end []) (void) attribute_hidden;
 179 extern void (*__init_array_start []) (void) attribute_hidden;
 180 extern void (*__init_array_end []) (void) attribute_hidden;
 181 extern void (*__fini_array_start []) (void) attribute_hidden;
 182 extern void (*__fini_array_end []) (void) attribute_hidden;
 183 # endif
 184 #endif
 185
 186 #ifdef SHARED
 187 extern int _dl_secure;
 188 #endif
 189 extern size_t _dl_pagesize;
 190
 191 const char *__uclibc_progname = "";
 192 #if !defined __UCLIBC_HAS___PROGNAME__ && defined __USE_GNU && defined __UCLIBC_HAS_PROGRAM_INVOCATION_NAME__
 193 # define __progname program_invocation_short_name
 194 # define __progname_full program_invocation_name
 195 #endif
 196 #if defined __UCLIBC_HAS___PROGNAME__ || (defined __USE_GNU && defined __UCLIBC_HAS_PROGRAM_INVOCATION_NAME__)
 197 const char *__progname = "";
 198 /* psm: why have a visible __progname_full? */
 199 const char *__progname_full = "";
 200 # if defined __UCLIBC_HAS___PROGNAME__ && defined __USE_GNU && defined __UCLIBC_HAS_PROGRAM_INVOCATION_NAME__
 201 weak_alias (__progname, program_invocation_short_name)
 202 weak_alias (__progname_full, program_invocation_name)
 203 # endif
 204 #endif
 205
 206 /*
 207  * Declare the __environ global variable and create a weak alias environ.
 208  * This must be initialized; we cannot have a weak alias into bss.
 209  */
 210 char **__environ = 0;
 211 weak_alias(__environ, environ)
 212
 213 size_t __pagesize = 0;
 214
 215 #ifndef O_NOFOLLOW
 216 # define O_NOFOLLOW     0
 217 #endif
 218
 219 #ifndef __ARCH_HAS_NO_LDSO__
 220 static void __check_one_fd(int fd, int mode)
 221 {
 222     /* Check if the specified fd is already open */
 223     if (fcntl(fd, F_GETFD) == -1)
 224     {
 225         /* The descriptor is probably not open, so try to use /dev/null */
 226         int nullfd = open(_PATH_DEVNULL, mode);
 227         /* /dev/null is major=1 minor=3.  Make absolutely certain
 228          * that is in fact the device that we have opened and not
 229          * some other wierd file... [removed in uclibc] */
 230         if (nullfd!=fd)
 231         {
 232                 abort();
 233         }
 234     }
 235 }
 236
 237 #ifndef SHARED
 238 static int __check_suid(void)
 239 {
 240     uid_t uid, euid;
 241     gid_t gid, egid;
 242
 243     uid  = getuid();
 244     euid = geteuid();
 245     if (uid != euid)
 246         return 1;
 247     gid  = getgid();
 248     egid = getegid();
 249     if (gid != egid)
 250         return 1;
 251     return 0; /* we are not suid */
 252 }
 253 #endif
 254 #endif
 255
 256 /* __uClibc_init completely initialize uClibc so it is ready to use.
 257  *
 258  * On ELF systems (with a dynamic loader) this function must be called
 259  * from the dynamic loader (see TIS and ELF Specification), so that
 260  * constructors of shared libraries (which depend on libc) can use all
 261  * the libc code without restriction.  For this we link the shared
 262  * version of the uClibc with -init __uClibc_init so DT_INIT for
 263  * uClibc is the address of __uClibc_init
 264  *
 265  * In all other cases we call it from the main stub
 266  * __uClibc_main.
 267  */
 268
 269 extern void __uClibc_init(void) attribute_hidden;
 270 void __uClibc_init(void)
 271 {
 272     /* Don't recurse */
 273     if (__pagesize)
 274         return;
 275
 276     /* Setup an initial value.  This may not be perfect, but is
 277      * better than  malloc using __pagesize=0 for atexit, ctors, etc.  */
 278     __pagesize = PAGE_SIZE;
 279
 280 #ifdef __UCLIBC_HAS_THREADS__
 281
 282 #if defined (__UCLIBC_HAS_THREADS_NATIVE__) && !defined (SHARED)
 283     /* Unlike in the dynamically linked case the dynamic linker has not
 284        taken care of initializing the TLS data structures.  */
 285     __libc_setup_tls (TLS_TCB_SIZE, TLS_TCB_ALIGN);
 286 #endif
 287
 288     /* Before we start initializing uClibc we have to call
 289      * __pthread_initialize_minimal so we can use pthread_locks
 290      * whenever they are needed.
 291      */
 292 #if !defined (__UCLIBC_HAS_THREADS_NATIVE__) || defined (SHARED)
 293     if (likely(__pthread_initialize_minimal!=NULL))
 294 #endif
 295         __pthread_initialize_minimal();
 296 #endif
 297
 298 #ifndef SHARED
 299 # ifdef __UCLIBC_HAS_SSP__
 300     /* Set up the stack checker's canary.  */
 301     stack_chk_guard = _dl_setup_stack_chk_guard();
 302 #  ifdef THREAD_SET_STACK_GUARD
 303     THREAD_SET_STACK_GUARD (stack_chk_guard);
 304 #  else
 305     __stack_chk_guard = stack_chk_guard;
 306 #  endif
 307 # endif
 308 #endif
 309
 310 #ifdef __UCLIBC_HAS_LOCALE__
 311     /* Initialize the global locale structure. */
 312     if (likely(not_null_ptr(_locale_init)))
 313         _locale_init();
 314 #endif
 315
 316     /*
 317      * Initialize stdio here.  In the static library case, this will
 318      * be bypassed if not needed because of the weak alias above.
 319      * Thus we get a nice size savings because the stdio functions
 320      * won't be pulled into the final static binary unless used.
 321      */
 322     if (likely(not_null_ptr(_stdio_init)))
 323         _stdio_init();
 324
 325 }
 326
 327 #ifdef __UCLIBC_CTOR_DTOR__
 328 void attribute_hidden (*__app_fini)(void) = NULL;
 329 #endif
 330
 331 void attribute_hidden (*__rtld_fini)(void) = NULL;
 332
 333 extern void __uClibc_fini(void) attribute_hidden;
 334 void __uClibc_fini(void)
 335 {
 336 #ifdef __UCLIBC_CTOR_DTOR__
 337     /* If __UCLIBC_FORMAT_SHARED_FLAT__, all array finalisation is handled
 338      * by __app_fini.  */
 339 # ifdef SHARED
 340     _dl_app_fini_array();
 341 # elif !defined (__UCLIBC_FORMAT_SHARED_FLAT__)
 342     size_t i = __fini_array_end - __fini_array_start;
 343     while (i-- > 0)
 344 #if !defined(SHARED) && defined(__FDPIC__)
 345         fdpic_init_array_jump(__fini_array_start[i]);
 346 #else
 347         (*__fini_array_start [i]) ();
 348 #endif
 349 # endif
 350     if (__app_fini != NULL)
 351         (__app_fini)();
 352 #endif
 353     if (__rtld_fini != NULL)
 354         (__rtld_fini)();
 355 }
 356
 357 #ifndef SHARED
 358 extern void __nptl_deallocate_tsd (void) __attribute ((weak));
 359 extern unsigned int __nptl_nthreads __attribute ((weak));
 360 #endif
 361
 362 /* __uClibc_main is the new main stub for uClibc. This function is
 363  * called from crt1 (version 0.9.28 or newer), after ALL shared libraries
 364  * are initialized, just before we call the application's main function.
 365  */
 366 void __uClibc_main(int (*main)(int, char **, char **), int argc,
 367                     char **argv, void (*app_init)(void), void (*app_fini)(void),
 368                     void (*rtld_fini)(void),
 369                     void *stack_end attribute_unused) attribute_noreturn;
 370 void __uClibc_main(int (*main)(int, char **, char **), int argc,
 371                     char **argv, void (*app_init)(void), void (*app_fini)(void),
 372                     void (*rtld_fini)(void), void *stack_end attribute_unused)
 373 {
 374 #ifndef SHARED
 375     unsigned long *aux_dat;
 376     ElfW(auxv_t) auxvt[AT_EGID + 1];
 377 #endif
 378
 379 #ifdef __UCLIBC_HAS_THREADS_NATIVE__
 380         /* Result of the 'main' function.  */
 381         int result;
 382 #endif
 383
 384 #ifndef SHARED
 385     __libc_stack_end = stack_end;
 386 #endif
 387
 388     __rtld_fini = rtld_fini;
 389
 390     /* The environment begins right after argv.  */
 391     __environ = &argv[argc + 1];
 392
 393     /* If the first thing after argv is the arguments
 394      * then the environment is empty. */
 395     if ((char *) __environ == *argv) {
 396         /* Make __environ point to the NULL at argv[argc] */
 397         __environ = &argv[argc];
 398     }
 399
 400 #ifndef SHARED
 401     /* Pull stuff from the ELF header when possible */
 402     memset(auxvt, 0x00, sizeof(auxvt));
 403     aux_dat = (unsigned long*)__environ;
 404     while (*aux_dat) {
 405         aux_dat++;
 406     }
 407     aux_dat++;
 408     while (*aux_dat) {
 409         ElfW(auxv_t) *auxv_entry = (ElfW(auxv_t) *) aux_dat;
 410         if (auxv_entry->a_type <= AT_EGID) {
 411             memcpy(&(auxvt[auxv_entry->a_type]), auxv_entry, sizeof(ElfW(auxv_t)));
 412         }
 413         aux_dat += 2;
 414     }
 415     /* Get the program headers (_dl_phdr) from the aux vector
 416        It will be used into __libc_setup_tls. */
 417
 418     _dl_aux_init (auxvt);
 419 #endif
 420
 421     /* We need to initialize uClibc.  If we are dynamically linked this
 422      * may have already been completed by the shared lib loader.  We call
 423      * __uClibc_init() regardless, to be sure the right thing happens. */
 424     __uClibc_init();
 425
 426 #ifndef __ARCH_HAS_NO_LDSO__
 427     /* Make certain getpagesize() gives the correct answer.
 428      * _dl_pagesize is defined into ld.so if SHARED or into libc.a otherwise. */
 429     __pagesize = _dl_pagesize;
 430
 431 #ifndef SHARED
 432     /* Prevent starting SUID binaries where the stdin. stdout, and
 433      * stderr file descriptors are not already opened. */
 434     if ((auxvt[AT_UID].a_un.a_val == (size_t)-1 && __check_suid()) ||
 435             (auxvt[AT_UID].a_un.a_val != (size_t)-1 &&
 436             (auxvt[AT_UID].a_un.a_val != auxvt[AT_EUID].a_un.a_val ||
 437              auxvt[AT_GID].a_un.a_val != auxvt[AT_EGID].a_un.a_val)))
 438 #else
 439     if (_dl_secure)
 440 #endif
 441     {
 442         __check_one_fd (STDIN_FILENO, O_RDONLY | O_NOFOLLOW);
 443         __check_one_fd (STDOUT_FILENO, O_RDWR | O_NOFOLLOW);
 444         __check_one_fd (STDERR_FILENO, O_RDWR | O_NOFOLLOW);
 445         _pe_secure = 1 ;
 446     }
 447     else
 448         _pe_secure = 0 ;
 449 #endif
 450
 451     __uclibc_progname = *argv;
 452 #if defined __UCLIBC_HAS___PROGNAME__ || (defined __USE_GNU && defined __UCLIBC_HAS_PROGRAM_INVOCATION_NAME__)
 453     if (*argv != NULL) {
 454         __progname_full = *argv;
 455         __progname = strrchr(*argv, '/');
 456         if (__progname != NULL)
 457             ++__progname;
 458         else
 459             __progname = *argv;
 460     }
 461 #endif
 462
 463 #ifdef __UCLIBC_CTOR_DTOR__
 464     /* Arrange for the application's dtors to run before we exit.  */
 465     __app_fini = app_fini;
 466
 467     /* If __UCLIBC_FORMAT_SHARED_FLAT__, all array initialisation is handled
 468      * by __app_init.  */
 469 # if !defined (SHARED) && !defined (__UCLIBC_FORMAT_SHARED_FLAT__)
 470     /* For dynamically linked executables the preinit array is executed by
 471        the dynamic linker (before initializing any shared object).
 472        For static executables, preinit happens rights before init.  */
 473     {
 474         const size_t size = __preinit_array_end - __preinit_array_start;
 475         size_t i;
 476         for (i = 0; i < size; i++)
 477 #if !defined(SHARED) && defined(__FDPIC__)
 478             fdpic_init_array_jump(__preinit_array_start[i]);
 479 #else
 480             (*__preinit_array_start [i]) ();
 481 #endif
 482     }
 483 # endif
 484     /* Run all the application's ctors now.  */
 485     if (app_init!=NULL) {
 486         app_init();
 487     }
 488     /* If __UCLIBC_FORMAT_SHARED_FLAT__, all array initialisation is handled
 489      * by __app_init.  */
 490 # ifdef SHARED
 491     _dl_app_init_array();
 492 # elif !defined (__UCLIBC_FORMAT_SHARED_FLAT__)
 493     {
 494         const size_t size = __init_array_end - __init_array_start;
 495         size_t i;
 496         for (i = 0; i < size; i++)
 497 #if !defined(SHARED) && defined(__FDPIC__)
 498             fdpic_init_array_jump(__init_array_start[i]);
 499 #else
 500             (*__init_array_start [i]) ();
 501 #endif
 502     }
 503 # endif
 504 #endif
 505
 506     /* Note: It is possible that any initialization done above could
 507      * have resulted in errno being set nonzero, so set it to 0 before
 508      * we call main.
 509      */
 510     if (likely(not_null_ptr(__errno_location)))
 511         *(__errno_location()) = 0;
 512
 513     /* Set h_errno to 0 as well */
 514     if (likely(not_null_ptr(__h_errno_location)))
 515         *(__h_errno_location()) = 0;
 516
 517 #if defined HAVE_CLEANUP_JMP_BUF && defined __UCLIBC_HAS_THREADS_NATIVE__
 518         /* Memory for the cancellation buffer.  */
 519         struct pthread_unwind_buf unwind_buf;
 520
 521         int not_first_call;
 522         not_first_call =
 523                 setjmp ((struct __jmp_buf_tag *) unwind_buf.cancel_jmp_buf);
 524         if (__builtin_expect (! not_first_call, 1))
 525         {
 526                 struct pthread *self = THREAD_SELF;
 527
 528                 /* Store old info.  */
 529                 unwind_buf.priv.data.prev = THREAD_GETMEM (self, cleanup_jmp_buf);
 530                 unwind_buf.priv.data.cleanup = THREAD_GETMEM (self, cleanup);
 531
 532                 /* Store the new cleanup handler info.  */
 533                 THREAD_SETMEM (self, cleanup_jmp_buf, &unwind_buf);
 534
 535                 /* Run the program.  */
 536                 result = main (argc, argv, __environ);
 537         }
 538         else
 539         {
 540                 /* Remove the thread-local data.  */
 541                 __nptl_deallocate_tsd ();
 542
 543                 /* One less thread.  Decrement the counter.  If it is zero we
 544                    terminate the entire process.  */
 545                 result = 0;
 546                 unsigned int *const ptr = &__nptl_nthreads;
 547
 548                 if (ptr && ! atomic_decrement_and_test (ptr))
 549                         /* Not much left to do but to exit the thread, not the process.  */
 550                         __exit_thread_inline (0);
 551         }
 552
 553         exit (result);
 554 #else
 555         /*
 556          * Finally, invoke application's main and then exit.
 557          */
 558         exit (main (argc, argv, __environ));
 559 #endif
 560 }