dlfcn/eval.c

   1 /* You don't really want to know what this hack is for.
   2    Copyright (C) 1996-2014 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 <assert.h>
  20 #include <ctype.h>
  21 #include <dlfcn.h>
  22 #include <errno.h>
  23 #include <limits.h>
  24 #include <stdio.h>
  25 #include <stdlib.h>
  26 #include <string.h>
  27 #include <unistd.h>
  28
  29 static void *funcall (char **stringp) __attribute_noinline__;
  30 static void *eval (char **stringp);
  31
  32
  33 long int weak_function
  34 __strtol_internal (const char *nptr, char **endptr, int base, int group)
  35 {
  36   unsigned long int result = 0;
  37   long int sign = 1;
  38
  39   while (*nptr == ' ' || *nptr == '\t')
  40     ++nptr;
  41
  42   if (*nptr == '-')
  43     {
  44       sign = -1;
  45       ++nptr;
  46     }
  47   else if (*nptr == '+')
  48     ++nptr;
  49
  50   if (*nptr < '0' || *nptr > '9')
  51     {
  52       if (endptr != NULL)
  53         *endptr = (char *) nptr;
  54       return 0L;
  55     }
  56
  57   assert (base == 0);
  58   base = 10;
  59   if (*nptr == '0')
  60     {
  61       if (nptr[1] == 'x' || nptr[1] == 'X')
  62         {
  63           base = 16;
  64           nptr += 2;
  65         }
  66       else
  67         base = 8;
  68     }
  69
  70   while (*nptr >= '0' && *nptr <= '9')
  71     {
  72       unsigned long int digval = *nptr - '0';
  73       if (result > LONG_MAX / 10
  74           || (sign > 0 ? result == LONG_MAX / 10 && digval > LONG_MAX % 10
  75               : (result == ((unsigned long int) LONG_MAX + 1) / 10
  76                  && digval > ((unsigned long int) LONG_MAX + 1) % 10)))
  77         {
  78           errno = ERANGE;
  79           return sign > 0 ? LONG_MAX : LONG_MIN;
  80         }
  81       result *= base;
  82       result += digval;
  83       ++nptr;
  84     }
  85
  86   return (long int) result * sign;
  87 }
  88
  89
  90 static void *
  91 funcall (char **stringp)
  92 {
  93   void *args[strlen (*stringp)], **ap = args;
  94   void *argcookie = &args[1];
  95
  96   do
  97     {
  98       /* Evaluate the next token.  */
  99       *ap++ = eval (stringp);
 100
 101       /* Whitespace is irrelevant.  */
 102       while (isspace (**stringp))
 103         ++*stringp;
 104
 105       /* Terminate at closing paren or end of line.  */
 106     } while (**stringp != '\0' && **stringp != ')');
 107   if (**stringp != '\0')
 108     /* Swallow closing paren.  */
 109     ++*stringp;
 110
 111   if (args[0] == NULL)
 112     {
 113       static const char unknown[] = "Unknown function\n";
 114       write (1, unknown, sizeof unknown - 1);
 115       return NULL;
 116     }
 117
 118   /* Do it to it.  */
 119   __builtin_return (__builtin_apply (args[0],
 120                                      &argcookie,
 121                                      (char *) ap - (char *) &args[1]));
 122 }
 123
 124 static void *
 125 eval (char **stringp)
 126 {
 127   void *value;
 128   char *p = *stringp, c;
 129
 130   /* Whitespace is irrelevant.  */
 131   while (isspace (*p))
 132     ++p;
 133
 134   switch (*p)
 135     {
 136     case '"':
 137       /* String constant.  */
 138       value = ++p;
 139       do
 140         if (*p == '\\')
 141           {
 142             switch (*strcpy (p, p + 1))
 143               {
 144               case 't':
 145                 *p = '\t';
 146                 break;
 147               case 'n':
 148                 *p = '\n';
 149                 break;
 150               }
 151             ++p;
 152           }
 153       while (*p != '\0' && *p++ != '"');
 154       if (p[-1] == '"')
 155         p[-1] = '\0';
 156       break;
 157
 158     case '(':
 159       *stringp = ++p;
 160       return funcall (stringp);
 161
 162     default:
 163       /* Try to parse it as a number.  */
 164       value = (void *) __strtol_internal (p, stringp, 0, 0);
 165       if (*stringp != p)
 166         return value;
 167
 168       /* Anything else is a symbol that produces its address.  */
 169       value = p;
 170       do
 171         ++p;
 172       while (*p != '\0' && !isspace (*p) && (!ispunct (*p) || *p == '_'));
 173       c = *p;
 174       *p = '\0';
 175       value = dlsym (NULL, value);
 176       *p = c;
 177       break;
 178     }
 179
 180   *stringp = p;
 181   return value;
 182 }
 183
 184
 185 extern void _start (void) __attribute__ ((noreturn));
 186 void
 187 __attribute__ ((noreturn))
 188 _start (void)
 189 {
 190   char *buf = NULL;
 191   size_t bufsz = 0;
 192
 193   while (__getdelim (&buf, &bufsz, '\n', stdin) > 0)
 194     {
 195       char *p = buf;
 196       eval (&p);
 197     }
 198
 199   exit (0);
 200 }