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         char *name;
  28         int i;
  29
  30         type = get_type(expr);
  31         if (!type || type->type != SYM_ARRAY)
  32                 return 0;
  33         if (expr->type == EXPR_SYMBOL)
  34                 return 1;
  35         if (implied_not_equal(expr, 0))
  36                 return 1;
  37
  38         /* verify that it's not the first member of the struct */
  39         if (expr->type != EXPR_DEREF || !expr->member)
  40                 return 0;
  41         name = expr_to_var_sym(expr, &sym);
  42         free_string(name);
  43         if (!name || !sym)
  44                 return 0;
  45         type = get_real_base_type(sym);
  46         if (!type || type->type != SYM_PTR)
  47                 return 0;
  48         type = get_real_base_type(type);
  49         if (type->type != SYM_STRUCT)
  50                 return 0;
  51
  52         i = 0;
  53         FOR_EACH_PTR(type->symbol_list, tmp) {
  54                 i++;
  55                 if (!tmp->ident)
  56                         continue;
  57                 if (strcmp(expr->member->name, tmp->ident->name) == 0) {
  58                         if (i == 1)
  59                                 return 0;
  60                         return 1;
  61                 }
  62         } END_FOR_EACH_PTR(tmp);
  63
  64         return 0;
  65 }
  66
  67 static int get_member_offset(struct expression *expr)
  68 {
  69         struct symbol *type, *tmp;
  70         struct ident *member;
  71         int offset;
  72
  73         if (expr->type != EXPR_DEREF)  /* hopefully, this doesn't happen */
  74                 return 0;
  75
  76         member = expr->member;
  77         if (!member || !member->name)
  78                 return 0;
  79
  80         if (expr->member_offset >= 0)
  81                 return expr->member_offset;
  82
  83         type = get_type(expr->deref);
  84         if (!type || type->type != SYM_STRUCT)
  85                 return 0;
  86
  87         offset = 0;
  88         FOR_EACH_PTR(type->symbol_list, tmp) {
  89                 if (tmp->ident && tmp->ident->name &&
  90                     strcmp(member->name, tmp->ident->name) == 0) {
  91                         expr->member_offset = offset;
  92                         return offset;
  93                 }
  94                 offset += type_bytes(tmp);
  95         } END_FOR_EACH_PTR(tmp);
  96         return 0;
  97 }
  98
  99 static void add_offset_to_min(struct range_list **rl, int offset)
 100 {
 101         sval_t sval, max;
 102         struct range_list *orig = *rl;
 103         struct range_list *offset_rl;
 104         struct range_list *big_rl;
 105         struct range_list *tmp;
 106
 107         /*
 108          * I don't know.  I guess I want to preserve the upper value because
 109          * that has no information.  Only the lower value is interesting.
 110          */
 111
 112         if (!orig)
 113                 return;
 114         sval = rl_min(orig); /* get the type */
 115         sval.value = offset;
 116
 117         offset_rl = alloc_rl(sval, sval);
 118         tmp = rl_binop(orig, '+', offset_rl);
 119
 120         max = rl_max(orig);
 121         /* if we actually "know" the max then preserve it. */
 122         if (max.value < 100000) {
 123                 *rl = tmp;
 124                 return;
 125         }
 126         sval.value = 0;
 127         big_rl = alloc_rl(sval, max);
 128
 129         *rl = rl_intersection(tmp, big_rl);
 130 }
 131
 132 static struct range_list *where_allocated_rl(struct symbol *sym)
 133 {
 134         if (sym->ctype.modifiers & (MOD_TOPLEVEL | MOD_STATIC)) {
 135                 if (sym->initializer)
 136                         return alloc_rl(data_seg_min, data_seg_max);
 137                 else
 138                         return alloc_rl(bss_seg_min, bss_seg_max);
 139         }
 140         return alloc_rl(stack_seg_min, stack_seg_max);
 141 }
 142
 143 int get_address_rl(struct expression *expr, struct range_list **rl)
 144 {
 145         expr = strip_expr(expr);
 146         if (!expr)
 147                 return 0;
 148
 149         if (expr->type == EXPR_STRING) {
 150                 *rl = alloc_rl(text_seg_min, text_seg_max);
 151                 return 1;
 152         }
 153
 154         if (expr->type == EXPR_PREOP && expr->op == '&') {
 155                 struct expression *unop;
 156
 157                 unop = strip_expr(expr->unop);
 158                 if (unop->type == EXPR_SYMBOL) {
 159                         *rl = where_allocated_rl(unop->symbol);
 160                         return 1;
 161                 }
 162
 163                 if (unop->type == EXPR_DEREF) {
 164                         int offset = get_member_offset(unop);
 165
 166                         unop = strip_expr(unop->unop);
 167                         if (unop->type == EXPR_SYMBOL) {
 168                                 *rl = where_allocated_rl(unop->symbol);
 169                         } else if (unop->type == EXPR_PREOP && unop->op == '*') {
 170                                 unop = strip_expr(unop->unop);
 171                                 get_absolute_rl(unop, rl);
 172                         } else {
 173                                 return 0;
 174                         }
 175
 176                         add_offset_to_min(rl, offset);
 177                         return 1;
 178                 }
 179
 180                 return 0;
 181         }
 182
 183         if (is_non_null_array(expr)) {
 184                 *rl = alloc_rl(array_min_sval, array_max_sval);
 185                 return 1;
 186         }
 187
 188         return 0;
 189 }