elf/dl-minimal.c

   1 /* Minimal replacements for basic facilities used in the dynamic linker.
   2    Copyright (C) 1995-2015 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <errno.h>
  20 #include <limits.h>
  21 #include <stdio.h>
  22 #include <string.h>
  23 #include <tls.h>
  24 #include <unistd.h>
  25 #include <sys/mman.h>
  26 #include <sys/param.h>
  27 #include <sys/types.h>
  28 #include <ldsodefs.h>
  29 #include <_itoa.h>
  30
  31 #include <assert.h>
  32
  33 /* Minimal `malloc' allocator for use while loading shared libraries.
  34    No block is ever freed.  */
  35
  36 static void *alloc_ptr, *alloc_end, *alloc_last_block;
  37
  38 /* Declarations of global functions.  */
  39 extern void weak_function free (void *ptr);
  40 extern void * weak_function realloc (void *ptr, size_t n);
  41 extern unsigned long int weak_function __strtoul_internal (const char *nptr,
  42                                                            char **endptr,
  43                                                            int base,
  44                                                            int group);
  45 extern unsigned long int weak_function strtoul (const char *nptr,
  46                                                 char **endptr, int base);
  47
  48
  49 /* Allocate an aligned memory block.  */
  50 void * weak_function
  51 __libc_memalign (size_t align, size_t n)
  52 {
  53   if (alloc_end == 0)
  54     {
  55       /* Consume any unused space in the last page of our data segment.  */
  56       extern int _end attribute_hidden;
  57       alloc_ptr = &_end;
  58       alloc_end = (void *) 0 + (((alloc_ptr - (void *) 0)
  59                                  + GLRO(dl_pagesize) - 1)
  60                                 & ~(GLRO(dl_pagesize) - 1));
  61     }
  62
  63   /* Make sure the allocation pointer is ideally aligned.  */
  64   alloc_ptr = (void *) 0 + (((alloc_ptr - (void *) 0) + align - 1)
  65                             & ~(align - 1));
  66
  67   if (alloc_ptr + n >= alloc_end || n >= -(uintptr_t) alloc_ptr)
  68     {
  69       /* Insufficient space left; allocate another page.  */
  70       caddr_t page;
  71       size_t nup = (n + GLRO(dl_pagesize) - 1) & ~(GLRO(dl_pagesize) - 1);
  72       if (__glibc_unlikely (nup == 0))
  73         {
  74           if (n)
  75             return NULL;
  76           nup = GLRO(dl_pagesize);
  77         }
  78       page = __mmap (0, nup, PROT_READ|PROT_WRITE,
  79                      MAP_ANON|MAP_PRIVATE, -1, 0);
  80       if (page == MAP_FAILED)
  81         return NULL;
  82       if (page != alloc_end)
  83         alloc_ptr = page;
  84       alloc_end = page + nup;
  85     }
  86
  87   alloc_last_block = (void *) alloc_ptr;
  88   alloc_ptr += n;
  89   return alloc_last_block;
  90 }
  91
  92 void * weak_function
  93 malloc (size_t n)
  94 {
  95   return __libc_memalign (sizeof (double), n);
  96 }
  97
  98 /* We use this function occasionally since the real implementation may
  99    be optimized when it can assume the memory it returns already is
 100    set to NUL.  */
 101 void * weak_function
 102 calloc (size_t nmemb, size_t size)
 103 {
 104   /* New memory from the trivial malloc above is always already cleared.
 105      (We make sure that's true in the rare occasion it might not be,
 106      by clearing memory in free, below.)  */
 107   size_t bytes = nmemb * size;
 108
 109 #define HALF_SIZE_T (((size_t) 1) << (8 * sizeof (size_t) / 2))
 110   if (__builtin_expect ((nmemb | size) >= HALF_SIZE_T, 0)
 111       && size != 0 && bytes / size != nmemb)
 112     return NULL;
 113
 114   return malloc (bytes);
 115 }
 116
 117 /* This will rarely be called.  */
 118 void weak_function
 119 free (void *ptr)
 120 {
 121   /* We can free only the last block allocated.  */
 122   if (ptr == alloc_last_block)
 123     {
 124       /* Since this is rare, we clear the freed block here
 125          so that calloc can presume malloc returns cleared memory.  */
 126       memset (alloc_last_block, '\0', alloc_ptr - alloc_last_block);
 127       alloc_ptr = alloc_last_block;
 128     }
 129 }
 130
 131 /* This is only called with the most recent block returned by malloc.  */
 132 void * weak_function
 133 realloc (void *ptr, size_t n)
 134 {
 135   if (ptr == NULL)
 136     return malloc (n);
 137   assert (ptr == alloc_last_block);
 138   size_t old_size = alloc_ptr - alloc_last_block;
 139   alloc_ptr = alloc_last_block;
 140   void *new = malloc (n);
 141   return new != ptr ? memcpy (new, ptr, old_size) : new;
 142 }
 143 \f
 144 /* Avoid signal frobnication in setjmp/longjmp.  Keeps things smaller.  */
 145
 146 #include <setjmp.h>
 147
 148 int weak_function
 149 __sigjmp_save (sigjmp_buf env, int savemask __attribute__ ((unused)))
 150 {
 151   env[0].__mask_was_saved = 0;
 152   return 0;
 153 }
 154 \f
 155 /* Define our own version of the internal function used by strerror.  We
 156    only provide the messages for some common errors.  This avoids pulling
 157    in the whole error list.  */
 158
 159 char * weak_function
 160 __strerror_r (int errnum, char *buf, size_t buflen)
 161 {
 162   char *msg;
 163
 164   switch (errnum)
 165     {
 166     case ENOMEM:
 167       msg = (char *) "Cannot allocate memory";
 168       break;
 169     case EINVAL:
 170       msg = (char *) "Invalid argument";
 171       break;
 172     case ENOENT:
 173       msg = (char *) "No such file or directory";
 174       break;
 175     case EPERM:
 176       msg = (char *) "Operation not permitted";
 177       break;
 178     case EIO:
 179       msg = (char *) "Input/output error";
 180       break;
 181     case EACCES:
 182       msg = (char *) "Permission denied";
 183       break;
 184     default:
 185       /* No need to check buffer size, all calls in the dynamic linker
 186          provide enough space.  */
 187       buf[buflen - 1] = '\0';
 188       msg = _itoa (errnum, buf + buflen - 1, 10, 0);
 189       msg = memcpy (msg - (sizeof ("Error ") - 1), "Error ",
 190                     sizeof ("Error ") - 1);
 191       break;
 192     }
 193
 194   return msg;
 195 }
 196 \f
 197 void
 198 __libc_fatal (const char *message)
 199 {
 200   _dl_fatal_printf ("%s", message);
 201 }
 202 rtld_hidden_def (__libc_fatal)
 203
 204 void
 205 __attribute__ ((noreturn))
 206 __chk_fail (void)
 207 {
 208   _exit (127);
 209 }
 210 rtld_hidden_def (__chk_fail)
 211
 212 #ifndef NDEBUG
 213 /* Define (weakly) our own assert failure function which doesn't use stdio.
 214    If we are linked into the user program (-ldl), the normal __assert_fail
 215    defn can override this one.  */
 216
 217 void weak_function
 218 __assert_fail (const char *assertion,
 219                const char *file, unsigned int line, const char *function)
 220 {
 221   _dl_fatal_printf ("\
 222 Inconsistency detected by ld.so: %s: %u: %s%sAssertion `%s' failed!\n",
 223                     file, line, function ?: "", function ? ": " : "",
 224                     assertion);
 225
 226 }
 227 rtld_hidden_weak (__assert_fail)
 228
 229 void weak_function
 230 __assert_perror_fail (int errnum,
 231                       const char *file, unsigned int line,
 232                       const char *function)
 233 {
 234   char errbuf[400];
 235   _dl_fatal_printf ("\
 236 Inconsistency detected by ld.so: %s: %u: %s%sUnexpected error: %s.\n",
 237                     file, line, function ?: "", function ? ": " : "",
 238                     __strerror_r (errnum, errbuf, sizeof errbuf));
 239
 240 }
 241 rtld_hidden_weak (__assert_perror_fail)
 242 #endif
 243 \f
 244 unsigned long int weak_function
 245 __strtoul_internal (const char *nptr, char **endptr, int base, int group)
 246 {
 247   unsigned long int result = 0;
 248   long int sign = 1;
 249   unsigned max_digit;
 250
 251   while (*nptr == ' ' || *nptr == '\t')
 252     ++nptr;
 253
 254   if (*nptr == '-')
 255     {
 256       sign = -1;
 257       ++nptr;
 258     }
 259   else if (*nptr == '+')
 260     ++nptr;
 261
 262   if (*nptr < '0' || *nptr > '9')
 263     {
 264       if (endptr != NULL)
 265         *endptr = (char *) nptr;
 266       return 0UL;
 267     }
 268
 269   assert (base == 0);
 270   base = 10;
 271   max_digit = 9;
 272   if (*nptr == '0')
 273     {
 274       if (nptr[1] == 'x' || nptr[1] == 'X')
 275         {
 276           base = 16;
 277           nptr += 2;
 278         }
 279       else
 280         {
 281           base = 8;
 282           max_digit = 7;
 283         }
 284     }
 285
 286   while (1)
 287     {
 288       unsigned long int digval;
 289       if (*nptr >= '0' && *nptr <= '0' + max_digit)
 290         digval = *nptr - '0';
 291       else if (base == 16)
 292         {
 293           if (*nptr >= 'a' && *nptr <= 'f')
 294             digval = *nptr - 'a' + 10;
 295           else if (*nptr >= 'A' && *nptr <= 'F')
 296             digval = *nptr - 'A' + 10;
 297           else
 298             break;
 299         }
 300       else
 301         break;
 302
 303       if (result > ULONG_MAX / base
 304           || (result == ULONG_MAX / base && digval > ULONG_MAX % base))
 305         {
 306           errno = ERANGE;
 307           if (endptr != NULL)
 308             *endptr = (char *) nptr;
 309           return ULONG_MAX;
 310         }
 311       result *= base;
 312       result += digval;
 313       ++nptr;
 314     }
 315
 316   if (endptr != NULL)
 317     *endptr = (char *) nptr;
 318   return result * sign;
 319 }
 320
 321
 322 #undef _itoa
 323 /* We always use _itoa instead of _itoa_word in ld.so since the former
 324    also has to be present and it is never about speed when these
 325    functions are used.  */
 326 char *
 327 _itoa (unsigned long long int value, char *buflim, unsigned int base,
 328        int upper_case)
 329 {
 330   assert (! upper_case);
 331
 332   do
 333     *--buflim = _itoa_lower_digits[value % base];
 334   while ((value /= base) != 0);
 335
 336   return buflim;
 337 }
 338
 339 /* The '_itoa_lower_digits' variable in libc.so is able to handle bases
 340    up to 36.  We don't need this here.  */
 341 const char _itoa_lower_digits[16] = "0123456789abcdef";
 342 rtld_hidden_data_def (_itoa_lower_digits)
 343 \f
 344 /* The following is not a complete strsep implementation.  It cannot
 345    handle empty delimiter strings.  But this isn't necessary for the
 346    execution of ld.so.  */
 347 #undef strsep
 348 #undef __strsep
 349 char *
 350 __strsep (char **stringp, const char *delim)
 351 {
 352   char *begin;
 353
 354   assert (delim[0] != '\0');
 355
 356   begin = *stringp;
 357   if (begin != NULL)
 358     {
 359       char *end = begin;
 360
 361       while (*end != '\0' || (end = NULL))
 362         {
 363           const char *dp = delim;
 364
 365           do
 366             if (*dp == *end)
 367               break;
 368           while (*++dp != '\0');
 369
 370           if (*dp != '\0')
 371             {
 372               *end++ = '\0';
 373               break;
 374             }
 375
 376           ++end;
 377         }
 378
 379       *stringp = end;
 380     }
 381
 382   return begin;
 383 }
 384 weak_alias (__strsep, strsep)
 385 strong_alias (__strsep, __strsep_g)