smatch_address.c

   1 /*
   2  * Copyright (C) 2015 Oracle.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public License
   6  * as published by the Free Software Foundation; either version 2
   7  * of the License, or (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, see http://www.gnu.org/copyleft/gpl.txt
  16  */
  17
  18 #include "smatch.h"
  19 #include "smatch_slist.h"
  20 #include "smatch_extra.h"
  21
  22 static bool is_non_null_array(struct expression *expr)
  23 {
  24         struct symbol *type;
  25         struct symbol *sym;
  26         struct symbol *tmp;
  27         int i;
  28
  29         type = get_type(expr);
  30         if (!type || type->type != SYM_ARRAY)
  31                 return 0;
  32         if (expr->type == EXPR_SYMBOL)
  33                 return 1;
  34         if (implied_not_equal(expr, 0))
  35                 return 1;
  36
  37         /* verify that it's not the first member of the struct */
  38         if (expr->type != EXPR_DEREF || !expr->member)
  39                 return 0;
  40         sym = expr_to_sym(expr);
  41         if (!sym)
  42                 return 0;
  43         type = get_real_base_type(sym);
  44         if (!type || type->type != SYM_PTR)
  45                 return 0;
  46         type = get_real_base_type(type);
  47         if (type->type != SYM_STRUCT)
  48                 return 0;
  49
  50         i = 0;
  51         FOR_EACH_PTR(type->symbol_list, tmp) {
  52                 i++;
  53                 if (!tmp->ident)
  54                         continue;
  55                 if (strcmp(expr->member->name, tmp->ident->name) == 0) {
  56                         if (i == 1)
  57                                 return 0;
  58                         return 1;
  59                 }
  60         } END_FOR_EACH_PTR(tmp);
  61
  62         return 0;
  63 }
  64
  65 static bool matches_anonymous_union(struct symbol *sym, const char *member_name)
  66 {
  67         struct symbol *type, *tmp;
  68
  69         if (sym->ident)
  70                 return false;
  71         type = get_real_base_type(sym);
  72         if (!type || type->type != SYM_UNION)
  73                 return false;
  74
  75         FOR_EACH_PTR(type->symbol_list, tmp) {
  76                 if (tmp->ident &&
  77                     strcmp(member_name, tmp->ident->name) == 0) {
  78                         return true;
  79                 }
  80         } END_FOR_EACH_PTR(tmp);
  81
  82         return false;
  83 }
  84
  85 int get_member_offset(struct symbol *type, const char *member_name)
  86 {
  87         struct symbol *tmp;
  88         int offset;
  89         int bits;
  90
  91         if (!type || type->type != SYM_STRUCT)
  92                 return -1;
  93
  94         bits = 0;
  95         offset = 0;
  96         FOR_EACH_PTR(type->symbol_list, tmp) {
  97                 if (bits_to_bytes(bits + type_bits(tmp)) > tmp->ctype.alignment) {
  98                         offset += bits_to_bytes(bits);
  99                         bits = 0;
 100                 }
 101                 offset = ALIGN(offset, tmp->ctype.alignment);
 102                 if (tmp->ident &&
 103                     strcmp(member_name, tmp->ident->name) == 0) {
 104                         return offset;
 105                 }
 106                 if (matches_anonymous_union(tmp, member_name))
 107                         return offset;
 108                 if (!(type_bits(tmp) % 8) && type_bits(tmp) / 8 == type_bytes(tmp))
 109                         offset += type_bytes(tmp);
 110                 else
 111                         bits += type_bits(tmp);
 112         } END_FOR_EACH_PTR(tmp);
 113         return -1;
 114 }
 115
 116 int get_member_offset_from_deref(struct expression *expr)
 117 {
 118         struct symbol *type;
 119         struct ident *member;
 120         int offset;
 121
 122         if (expr->type != EXPR_DEREF)  /* hopefully, this doesn't happen */
 123                 return -1;
 124
 125         if (expr->member_offset >= 0)
 126                 return expr->member_offset;
 127
 128         member = expr->member;
 129         if (!member)
 130                 return -1;
 131
 132         type = get_type(expr->deref);
 133         if (type_is_ptr(type))
 134                 type = get_real_base_type(type);
 135         if (!type || type->type != SYM_STRUCT)
 136                 return -1;
 137
 138         offset = get_member_offset(type, member->name);
 139         if (offset >= 0)
 140                 expr->member_offset = offset;
 141         return offset;
 142 }
 143
 144 static void add_offset_to_pointer(struct range_list **rl, int offset)
 145 {
 146         sval_t min, max, remove, sval;
 147         struct range_list *orig = *rl;
 148
 149         /*
 150          * Ha ha.  Treating zero as a special case means I'm correct at least a
 151          * tiny fraction of the time.  Which is better than nothing.
 152          *
 153          */
 154         if (offset == 0)
 155                 return;
 156
 157         if (is_unknown_ptr(orig))
 158                 return;
 159
 160         /*
 161          * This function doesn't necessarily work how you might expect...
 162          *
 163          * Say you have s64min-(-1),1-s64max and you add 8 then I guess what
 164          * we want to say is maybe something like 9-s64max.  This shows that the
 165          * min it could be is 9 which is potentially useful information.  But
 166          * if we start with (-12),5000000-57777777 and we add 8 then we'd want
 167          * the result to be (-4),5000008-57777777 but (-4),5000000-57777777 is
 168          * also probably acceptable.  If you start with s64min-s64max then the
 169          * result should be 8-s64max.
 170          *
 171          */
 172
 173         /* We do the math on void pointer type, because this isn't "&v + 16" it
 174          * is &v->sixteenth_byte.
 175          */
 176         orig = cast_rl(&ptr_ctype, orig);
 177         min = sval_type_min(&ptr_ctype);
 178         min.value = offset;
 179         max = sval_type_max(&ptr_ctype);
 180
 181         if (!orig || is_whole_rl(orig)) {
 182                 *rl = alloc_rl(min, max);
 183                 return;
 184         }
 185
 186         /* no wrap around */
 187         max.uvalue = rl_max(orig).uvalue;
 188         if (max.uvalue > sval_type_max(&ptr_ctype).uvalue - offset) {
 189                 remove = sval_type_max(&ptr_ctype);
 190                 remove.uvalue -= offset;
 191                 orig = remove_range(orig, remove, max);
 192         }
 193
 194         sval.type = &int_ctype;
 195         sval.value = offset;
 196
 197         *rl = rl_binop(orig, '+', alloc_rl(sval, sval));
 198 }
 199
 200 static struct range_list *where_allocated_rl(struct symbol *sym)
 201 {
 202         if (!sym)
 203                 return NULL;
 204
 205         return alloc_rl(valid_ptr_min_sval, valid_ptr_max_sval);
 206 }
 207
 208 int get_address_rl(struct expression *expr, struct range_list **rl)
 209 {
 210         struct expression *unop;
 211
 212         expr = strip_expr(expr);
 213         if (!expr)
 214                 return 0;
 215
 216         if (expr->type == EXPR_STRING) {
 217                 *rl = alloc_rl(valid_ptr_min_sval, valid_ptr_max_sval);
 218                 return 1;
 219         }
 220
 221         if (expr->type == EXPR_PREOP && expr->op == '&')
 222                 expr = strip_expr(expr->unop);
 223         else {
 224                 struct symbol *type;
 225
 226                 type = get_type(expr);
 227                 if (!type || type->type != SYM_ARRAY)
 228                         return 0;
 229         }
 230
 231         if (expr->type == EXPR_SYMBOL) {
 232                 *rl = where_allocated_rl(expr->symbol);
 233                 return 1;
 234         }
 235
 236         if (is_array(expr)) {
 237                 struct expression *array;
 238                 struct expression *offset_expr;
 239                 struct range_list *array_rl, *offset_rl, *bytes_rl, *res;
 240                 struct symbol *type;
 241                 sval_t bytes;
 242
 243                 array = get_array_base(expr);
 244                 offset_expr = get_array_offset(expr);
 245
 246                 type = get_type(array);
 247                 type = get_real_base_type(type);
 248                 bytes.type = ssize_t_ctype;
 249                 bytes.uvalue = type_bytes(type);
 250                 bytes_rl = alloc_rl(bytes, bytes);
 251
 252                 get_absolute_rl(array, &array_rl);
 253                 get_absolute_rl(offset_expr, &offset_rl);
 254
 255                 if (type_bytes(type)) {
 256                         res = rl_binop(offset_rl, '*', bytes_rl);
 257                         res = rl_binop(res, '+', array_rl);
 258                         *rl = res;
 259                         return true;
 260                 }
 261
 262                 if (implied_not_equal(array, 0) ||
 263                     implied_not_equal(offset_expr, 0)) {
 264                         *rl = alloc_rl(valid_ptr_min_sval, valid_ptr_max_sval);
 265                         return 1;
 266                 }
 267
 268                 return 0;
 269         }
 270
 271         if (expr->type == EXPR_DEREF && expr->member) {
 272                 struct range_list *unop_rl;
 273                 int offset;
 274
 275                 offset = get_member_offset_from_deref(expr);
 276                 unop = strip_expr(expr->unop);
 277                 if (unop->type == EXPR_PREOP && unop->op == '*')
 278                         unop = strip_expr(unop->unop);
 279
 280                 if (offset >= 0 && get_implied_rl(unop, &unop_rl)) {
 281                         *rl = unop_rl;
 282                         add_offset_to_pointer(rl, offset);
 283                         return 1;
 284                 }
 285
 286                 if (implied_not_equal(unop, 0) || offset > 0) {
 287                         *rl = alloc_rl(valid_ptr_min_sval, valid_ptr_max_sval);
 288                         return 1;
 289                 }
 290
 291                 return 0;
 292         }
 293
 294         if (is_non_null_array(expr)) {
 295                 *rl = alloc_rl(array_min_sval, array_max_sval);
 296                 return 1;
 297         }
 298
 299         return 0;
 300 }