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 int get_member_offset(struct symbol *type, char *member_name)
  66 {
  67         struct symbol *tmp;
  68         int offset;
  69
  70         if (type->type != SYM_STRUCT)
  71                 return -1;
  72
  73         offset = 0;
  74         FOR_EACH_PTR(type->symbol_list, tmp) {
  75                 if (!type->ctype.attribute->is_packed)
  76                         offset = ALIGN(offset, tmp->ctype.alignment);
  77                 if (tmp->ident &&
  78                     strcmp(member_name, tmp->ident->name) == 0) {
  79                         return offset;
  80                 }
  81                 offset += type_bytes(tmp);
  82         } END_FOR_EACH_PTR(tmp);
  83         return -1;
  84 }
  85
  86 int get_member_offset_from_deref(struct expression *expr)
  87 {
  88         struct symbol *type;
  89         struct ident *member;
  90         int offset;
  91
  92         if (expr->type != EXPR_DEREF)  /* hopefully, this doesn't happen */
  93                 return -1;
  94
  95         if (expr->member_offset >= 0)
  96                 return expr->member_offset;
  97
  98         member = expr->member;
  99         if (!member)
 100                 return -1;
 101
 102         type = get_type(expr->deref);
 103         if (!type || type->type != SYM_STRUCT)
 104                 return -1;
 105
 106         offset = get_member_offset(type, member->name);
 107         if (offset >= 0)
 108                 expr->member_offset = offset;
 109         return offset;
 110 }
 111
 112 static void add_offset_to_min(struct range_list **rl, int offset)
 113 {
 114         sval_t sval, max;
 115         struct range_list *orig = *rl;
 116         struct range_list *offset_rl;
 117         struct range_list *big_rl;
 118         struct range_list *tmp;
 119
 120         /*
 121          * I don't know.  I guess I want to preserve the upper value because
 122          * that has no information.  Only the lower value is interesting.
 123          */
 124
 125         if (!orig)
 126                 return;
 127         sval = rl_min(orig); /* get the type */
 128         sval.value = offset;
 129
 130         offset_rl = alloc_rl(sval, sval);
 131         tmp = rl_binop(orig, '+', offset_rl);
 132         if (!tmp)
 133                 tmp = alloc_whole_rl(sval.type);
 134
 135         max = rl_max(orig);
 136         /* if we actually "know" the max then preserve it. */
 137         if (max.value < 100000) {
 138                 *rl = tmp;
 139                 return;
 140         }
 141         sval.value = 0;
 142         big_rl = alloc_rl(sval, max);
 143
 144         *rl = rl_intersection(tmp, big_rl);
 145 }
 146
 147 static struct range_list *where_allocated_rl(struct symbol *sym)
 148 {
 149         if (!sym)
 150                 return NULL;
 151
 152         if (sym->ctype.modifiers & (MOD_TOPLEVEL | MOD_STATIC)) {
 153                 if (sym->initializer)
 154                         return alloc_rl(data_seg_min, data_seg_max);
 155                 else
 156                         return alloc_rl(bss_seg_min, bss_seg_max);
 157         }
 158         return alloc_rl(stack_seg_min, stack_seg_max);
 159 }
 160
 161 int get_address_rl(struct expression *expr, struct range_list **rl)
 162 {
 163         expr = strip_expr(expr);
 164         if (!expr)
 165                 return 0;
 166
 167         if (expr->type == EXPR_STRING) {
 168                 *rl = alloc_rl(text_seg_min, text_seg_max);
 169                 return 1;
 170         }
 171
 172         if (expr->type == EXPR_PREOP && expr->op == '&') {
 173                 struct expression *unop;
 174
 175                 unop = strip_expr(expr->unop);
 176                 if (unop->type == EXPR_SYMBOL) {
 177                         *rl = where_allocated_rl(unop->symbol);
 178                         return 1;
 179                 }
 180
 181                 if (unop->type == EXPR_DEREF) {
 182                         int offset = get_member_offset_from_deref(unop);
 183
 184                         unop = strip_expr(unop->unop);
 185                         if (unop->type == EXPR_SYMBOL) {
 186                                 *rl = where_allocated_rl(unop->symbol);
 187                         } else if (unop->type == EXPR_PREOP && unop->op == '*') {
 188                                 unop = strip_expr(unop->unop);
 189                                 get_absolute_rl(unop, rl);
 190                         } else {
 191                                 return 0;
 192                         }
 193
 194                         add_offset_to_min(rl, offset);
 195                         return 1;
 196                 }
 197
 198                 return 0;
 199         }
 200
 201         if (is_non_null_array(expr)) {
 202                 *rl = alloc_rl(array_min_sval, array_max_sval);
 203                 return 1;
 204         }
 205
 206         return 0;
 207 }