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