elf/dl-minimal.c

   1 /* Minimal replacements for basic facilities used in the dynamic linker.
   2    Copyright (C) 1995-2017 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 #include <malloc/malloc-internal.h>
  31
  32 #include <assert.h>
  33
  34 /* Minimal malloc allocator for used during initial link.  After the
  35    initial link, a full malloc implementation is interposed, either
  36    the one in libc, or a different one supplied by the user through
  37    interposition.  */
  38
  39 static void *alloc_ptr, *alloc_end, *alloc_last_block;
  40
  41 /* Declarations of global functions.  */
  42 extern void weak_function free (void *ptr);
  43 extern void * weak_function realloc (void *ptr, size_t n);
  44 extern unsigned long int weak_function __strtoul_internal (const char *nptr,
  45                                                            char **endptr,
  46                                                            int base,
  47                                                            int group);
  48 extern unsigned long int weak_function strtoul (const char *nptr,
  49                                                 char **endptr, int base);
  50
  51
  52 /* Allocate an aligned memory block.  */
  53 void * weak_function
  54 malloc (size_t n)
  55 {
  56   if (alloc_end == 0)
  57     {
  58       /* Consume any unused space in the last page of our data segment.  */
  59       extern int _end attribute_hidden;
  60       alloc_ptr = &_end;
  61       alloc_end = (void *) 0 + (((alloc_ptr - (void *) 0)
  62                                  + GLRO(dl_pagesize) - 1)
  63                                 & ~(GLRO(dl_pagesize) - 1));
  64     }
  65
  66   /* Make sure the allocation pointer is ideally aligned.  */
  67   alloc_ptr = (void *) 0 + (((alloc_ptr - (void *) 0) + MALLOC_ALIGNMENT - 1)
  68                             & ~(MALLOC_ALIGNMENT - 1));
  69
  70   if (alloc_ptr + n >= alloc_end || n >= -(uintptr_t) alloc_ptr)
  71     {
  72       /* Insufficient space left; allocate another page plus one extra
  73          page to reduce number of mmap calls.  */
  74       caddr_t page;
  75       size_t nup = (n + GLRO(dl_pagesize) - 1) & ~(GLRO(dl_pagesize) - 1);
  76       if (__glibc_unlikely (nup == 0 && n != 0))
  77         return NULL;
  78       nup += GLRO(dl_pagesize);
  79       page = __mmap (0, nup, PROT_READ|PROT_WRITE,
  80                      MAP_ANON|MAP_PRIVATE, -1, 0);
  81       if (page == MAP_FAILED)
  82         return NULL;
  83       if (page != alloc_end)
  84         alloc_ptr = page;
  85       alloc_end = page + nup;
  86     }
  87
  88   alloc_last_block = (void *) alloc_ptr;
  89   alloc_ptr += n;
  90   return alloc_last_block;
  91 }
  92
  93 /* We use this function occasionally since the real implementation may
  94    be optimized when it can assume the memory it returns already is
  95    set to NUL.  */
  96 void * weak_function
  97 calloc (size_t nmemb, size_t size)
  98 {
  99   /* New memory from the trivial malloc above is always already cleared.
 100      (We make sure that's true in the rare occasion it might not be,
 101      by clearing memory in free, below.)  */
 102   size_t bytes = nmemb * size;
 103
 104 #define HALF_SIZE_T (((size_t) 1) << (8 * sizeof (size_t) / 2))
 105   if (__builtin_expect ((nmemb | size) >= HALF_SIZE_T, 0)
 106       && size != 0 && bytes / size != nmemb)
 107     return NULL;
 108
 109   return malloc (bytes);
 110 }
 111
 112 /* This will rarely be called.  */
 113 void weak_function
 114 free (void *ptr)
 115 {
 116   /* We can free only the last block allocated.  */
 117   if (ptr == alloc_last_block)
 118     {
 119       /* Since this is rare, we clear the freed block here
 120          so that calloc can presume malloc returns cleared memory.  */
 121       memset (alloc_last_block, '\0', alloc_ptr - alloc_last_block);
 122       alloc_ptr = alloc_last_block;
 123     }
 124 }
 125
 126 /* This is only called with the most recent block returned by malloc.  */
 127 void * weak_function
 128 realloc (void *ptr, size_t n)
 129 {
 130   if (ptr == NULL)
 131     return malloc (n);
 132   assert (ptr == alloc_last_block);
 133   size_t old_size = alloc_ptr - alloc_last_block;
 134   alloc_ptr = alloc_last_block;
 135   void *new = malloc (n);
 136   return new != ptr ? memcpy (new, ptr, old_size) : new;
 137 }
 138 \f
 139 /* Avoid signal frobnication in setjmp/longjmp.  Keeps things smaller.  */
 140
 141 #include <setjmp.h>
 142
 143 int weak_function
 144 __sigjmp_save (sigjmp_buf env, int savemask __attribute__ ((unused)))
 145 {
 146   env[0].__mask_was_saved = 0;
 147   return 0;
 148 }
 149 \f
 150 /* Define our own version of the internal function used by strerror.  We
 151    only provide the messages for some common errors.  This avoids pulling
 152    in the whole error list.  */
 153
 154 char * weak_function
 155 __strerror_r (int errnum, char *buf, size_t buflen)
 156 {
 157   char *msg;
 158
 159   switch (errnum)
 160     {
 161     case ENOMEM:
 162       msg = (char *) "Cannot allocate memory";
 163       break;
 164     case EINVAL:
 165       msg = (char *) "Invalid argument";
 166       break;
 167     case ENOENT:
 168       msg = (char *) "No such file or directory";
 169       break;
 170     case EPERM:
 171       msg = (char *) "Operation not permitted";
 172       break;
 173     case EIO:
 174       msg = (char *) "Input/output error";
 175       break;
 176     case EACCES:
 177       msg = (char *) "Permission denied";
 178       break;
 179     default:
 180       /* No need to check buffer size, all calls in the dynamic linker
 181          provide enough space.  */
 182       buf[buflen - 1] = '\0';
 183       msg = _itoa (errnum, buf + buflen - 1, 10, 0);
 184       msg = memcpy (msg - (sizeof ("Error ") - 1), "Error ",
 185                     sizeof ("Error ") - 1);
 186       break;
 187     }
 188
 189   return msg;
 190 }
 191 \f
 192 void
 193 __libc_fatal (const char *message)
 194 {
 195   _dl_fatal_printf ("%s", message);
 196 }
 197 rtld_hidden_def (__libc_fatal)
 198
 199 void
 200 __attribute__ ((noreturn))
 201 __chk_fail (void)
 202 {
 203   _exit (127);
 204 }
 205 rtld_hidden_def (__chk_fail)
 206
 207 #ifndef NDEBUG
 208 /* Define (weakly) our own assert failure function which doesn't use stdio.
 209    If we are linked into the user program (-ldl), the normal __assert_fail
 210    defn can override this one.  */
 211
 212 void weak_function
 213 __assert_fail (const char *assertion,
 214                const char *file, unsigned int line, const char *function)
 215 {
 216   _dl_fatal_printf ("\
 217 Inconsistency detected by ld.so: %s: %u: %s%sAssertion `%s' failed!\n",
 218                     file, line, function ?: "", function ? ": " : "",
 219                     assertion);
 220
 221 }
 222 rtld_hidden_weak (__assert_fail)
 223
 224 void weak_function
 225 __assert_perror_fail (int errnum,
 226                       const char *file, unsigned int line,
 227                       const char *function)
 228 {
 229   char errbuf[400];
 230   _dl_fatal_printf ("\
 231 Inconsistency detected by ld.so: %s: %u: %s%sUnexpected error: %s.\n",
 232                     file, line, function ?: "", function ? ": " : "",
 233                     __strerror_r (errnum, errbuf, sizeof errbuf));
 234
 235 }
 236 rtld_hidden_weak (__assert_perror_fail)
 237 #endif
 238 \f
 239 unsigned long int weak_function
 240 __strtoul_internal (const char *nptr, char **endptr, int base, int group)
 241 {
 242   unsigned long int result = 0;
 243   long int sign = 1;
 244   unsigned max_digit;
 245
 246   while (*nptr == ' ' || *nptr == '\t')
 247     ++nptr;
 248
 249   if (*nptr == '-')
 250     {
 251       sign = -1;
 252       ++nptr;
 253     }
 254   else if (*nptr == '+')
 255     ++nptr;
 256
 257   if (*nptr < '0' || *nptr > '9')
 258     {
 259       if (endptr != NULL)
 260         *endptr = (char *) nptr;
 261       return 0UL;
 262     }
 263
 264   assert (base == 0);
 265   base = 10;
 266   max_digit = 9;
 267   if (*nptr == '0')
 268     {
 269       if (nptr[1] == 'x' || nptr[1] == 'X')
 270         {
 271           base = 16;
 272           nptr += 2;
 273         }
 274       else
 275         {
 276           base = 8;
 277           max_digit = 7;
 278         }
 279     }
 280
 281   while (1)
 282     {
 283       unsigned long int digval;
 284       if (*nptr >= '0' && *nptr <= '0' + max_digit)
 285         digval = *nptr - '0';
 286       else if (base == 16)
 287         {
 288           if (*nptr >= 'a' && *nptr <= 'f')
 289             digval = *nptr - 'a' + 10;
 290           else if (*nptr >= 'A' && *nptr <= 'F')
 291             digval = *nptr - 'A' + 10;
 292           else
 293             break;
 294         }
 295       else
 296         break;
 297
 298       if (result > ULONG_MAX / base
 299           || (result == ULONG_MAX / base && digval > ULONG_MAX % base))
 300         {
 301           errno = ERANGE;
 302           if (endptr != NULL)
 303             *endptr = (char *) nptr;
 304           return ULONG_MAX;
 305         }
 306       result *= base;
 307       result += digval;
 308       ++nptr;
 309     }
 310
 311   if (endptr != NULL)
 312     *endptr = (char *) nptr;
 313   return result * sign;
 314 }
 315
 316
 317 #undef _itoa
 318 /* We always use _itoa instead of _itoa_word in ld.so since the former
 319    also has to be present and it is never about speed when these
 320    functions are used.  */
 321 char *
 322 _itoa (unsigned long long int value, char *buflim, unsigned int base,
 323        int upper_case)
 324 {
 325   assert (! upper_case);
 326
 327   do
 328     *--buflim = _itoa_lower_digits[value % base];
 329   while ((value /= base) != 0);
 330
 331   return buflim;
 332 }
 333
 334 /* The '_itoa_lower_digits' variable in libc.so is able to handle bases
 335    up to 36.  We don't need this here.  */
 336 const char _itoa_lower_digits[16] = "0123456789abcdef";
 337 rtld_hidden_data_def (_itoa_lower_digits)
 338 \f
 339 /* The following is not a complete strsep implementation.  It cannot
 340    handle empty delimiter strings.  But this isn't necessary for the
 341    execution of ld.so.  */
 342 #undef strsep
 343 #undef __strsep
 344 char *
 345 __strsep (char **stringp, const char *delim)
 346 {
 347   char *begin;
 348
 349   assert (delim[0] != '\0');
 350
 351   begin = *stringp;
 352   if (begin != NULL)
 353     {
 354       char *end = begin;
 355
 356       while (*end != '\0' || (end = NULL))
 357         {
 358           const char *dp = delim;
 359
 360           do
 361             if (*dp == *end)
 362               break;
 363           while (*++dp != '\0');
 364
 365           if (*dp != '\0')
 366             {
 367               *end++ = '\0';
 368               break;
 369             }
 370
 371           ++end;
 372         }
 373
 374       *stringp = end;
 375     }
 376
 377   return begin;
 378 }
 379 weak_alias (__strsep, strsep)
 380 strong_alias (__strsep, __strsep_g)