smatch_clear_buffer.c

   1 /*
   2  * Copyright (C) 2013 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 int my_id;
  23
  24 STATE(uninitialized);
  25 STATE(initialized);
  26
  27 static int type_sym_array(struct expression *expr)
  28 {
  29         struct symbol *type;
  30
  31         /* remove casting the array to a pointer */
  32         expr = strip_expr(expr);
  33         type = get_type(expr);
  34         if (type && type->type == SYM_ARRAY)
  35                 return 1;
  36         return 0;
  37 }
  38
  39 static void set_members_uninitialized(struct expression *expr)
  40 {
  41         struct symbol *type, *sym, *tmp;
  42         char *name;
  43         char buf[256];
  44
  45         type = get_type(expr);
  46         if (!type)
  47                 return;
  48
  49         if (type->type != SYM_PTR)
  50                 return;
  51         type = get_real_base_type(type);
  52
  53         name = expr_to_var_sym(expr, &sym);
  54         if (!name || !sym)
  55                 goto free;
  56
  57         FOR_EACH_PTR(type->symbol_list, tmp) {
  58                 if (!tmp->ident)
  59                         continue;
  60                 snprintf(buf, sizeof(buf), "%s->%s", name, tmp->ident->name);
  61                 set_state(my_id, buf, sym, &uninitialized);
  62         } END_FOR_EACH_PTR(tmp);
  63
  64 free:
  65         free_string(name);
  66 }
  67
  68 static void initialize_struct_members(struct symbol *type, struct expression *expr, struct expression *to)
  69 {
  70         struct symbol *tmp;
  71         struct expression *member;
  72         struct expression *assign;
  73         int op = '*';
  74
  75         if (expr->type == EXPR_PREOP && expr->op == '&') {
  76                 expr = strip_expr(expr->unop);
  77                 op = '.';
  78         }
  79
  80         FOR_EACH_PTR(type->symbol_list, tmp) {
  81                 if (!tmp->ident)
  82                         continue;
  83                 member = member_expression(expr, op, tmp->ident);
  84                 if (type_sym_array(member))
  85                         continue;
  86
  87                 /*
  88                  * FIXME: the problem here is that sometimes we have:
  89                  *       memset(&my_struct, 0xff, sizeof(my_struct));
  90                  * and my_struct->foo is a 1 bit bitfield.  There is a check
  91                  * which complains that "255 doesn't fit in ->foo".
  92                  *
  93                  * For now I just have this ugly hack.  But really it's not
  94                  * handling the memset(..., 0xff, ...) correctly at all so one
  95                  * more hack barely makes a difference.
  96                  *
  97                  */
  98                 if (to && type_positive_bits(get_type(member)) >= type_positive_bits(get_type(to)))
  99                         assign = assign_expression(member, to);
 100                 else
 101                         assign = assign_expression(member, member);
 102
 103                 __pass_to_client(assign, ASSIGNMENT_HOOK);
 104         } END_FOR_EACH_PTR(tmp);
 105 }
 106
 107 static void initialize_base_type(struct symbol *type, struct expression *expr,
 108                 struct expression *to)
 109 {
 110         struct expression *assign;
 111
 112         if (type == &void_ctype)
 113                 return;
 114         if (expr->type == EXPR_PREOP && expr->op == '&')
 115                 expr = strip_expr(expr->unop);
 116         else
 117                 expr = deref_expression(expr);
 118         if (!to)
 119                 to = expr;
 120         /* FIXME: see the FIXME in initialize_struct_members() */
 121         if (type_positive_bits(get_type(expr)) < type_positive_bits(get_type(to)))
 122                 to = expr;
 123         assign = assign_expression(expr, to);
 124         __pass_to_client(assign, ASSIGNMENT_HOOK);
 125 }
 126
 127 static void set_initialized(struct expression *expr, struct expression *to)
 128 {
 129         struct symbol *type;
 130
 131         expr = strip_expr(expr);
 132
 133         type = get_type(expr);
 134         if (!type || type->type != SYM_PTR)
 135                 return;
 136         type = get_real_base_type(type);
 137         if (!type)
 138                 return;
 139         if (type->type == SYM_BASETYPE)
 140                 initialize_base_type(type, expr, to);
 141         if (type->type == SYM_STRUCT) {
 142                 if (expr->type != EXPR_PREOP || expr->op != '&')
 143                         expr = deref_expression(expr);
 144                 initialize_struct_members(type, expr, to);
 145         }
 146 }
 147
 148 int is_uninitialized(struct expression *expr)
 149 {
 150         struct sm_state *sm;
 151
 152         sm = get_sm_state_expr(my_id, expr);
 153         if (!sm)
 154                 return 0;
 155         return slist_has_state(sm->possible, &uninitialized);
 156 }
 157
 158 int has_uninitialized_members(struct expression *expr)
 159 {
 160         struct symbol *sym;
 161         struct symbol *tmp;
 162         char *name;
 163         char buf[256];
 164         struct sm_state *sm;
 165
 166         sym = get_type(expr);
 167         if (!sym)
 168                 return 0;
 169
 170         if (sym->type == SYM_PTR)
 171                 sym = get_real_base_type(sym);
 172
 173         name = expr_to_var(expr);
 174         if (!name)
 175                 return 0;
 176
 177         FOR_EACH_PTR(sym->symbol_list, tmp) {
 178                 if (!tmp->ident)
 179                         continue;
 180                 snprintf(buf, sizeof(buf), "%s->%s", name, tmp->ident->name);
 181                 sm = get_sm_state(my_id, buf, sym);
 182                 if (!sm)
 183                         continue;
 184                 if (slist_has_state(sm->possible, &uninitialized))
 185                         return 1;
 186         } END_FOR_EACH_PTR(tmp);
 187
 188         free_string(name);
 189         return 0;
 190 }
 191
 192 static void match_alloc(const char *fn, struct expression *expr, void *_size_arg)
 193 {
 194         set_members_uninitialized(expr->left);
 195 }
 196
 197 static void db_param_cleared(struct expression *expr, int param, char *key, char *value)
 198 {
 199         struct expression *arg;
 200
 201         while (expr->type == EXPR_ASSIGNMENT)
 202                 expr = strip_expr(expr->right);
 203         if (expr->type != EXPR_CALL)
 204                 return;
 205
 206         arg = get_argument_from_call_expr(expr->args, param);
 207         if (!arg)
 208                 return;
 209
 210         if (strcmp(value, "0") == 0)
 211                 set_initialized(arg, zero_expr());
 212         else
 213                 set_initialized(arg, NULL);
 214 }
 215
 216 static void reset_initialized(struct sm_state *sm, struct expression *mod_expr)
 217 {
 218         set_state(my_id, sm->name, sm->sym, &initialized);
 219 }
 220
 221 #define USB_DIR_IN 0x80
 222 static void match_usb_control_msg(const char *fn, struct expression *expr, void *_size_arg)
 223 {
 224         struct expression *inout;
 225         struct expression *buf;
 226         sval_t sval;
 227
 228         inout = get_argument_from_call_expr(expr->args, 3);
 229         buf = get_argument_from_call_expr(expr->args, 6);
 230
 231         if (get_value(inout, &sval) && !(sval.uvalue & USB_DIR_IN))
 232                 return;
 233
 234         set_initialized(buf, NULL);
 235 }
 236
 237 void register_clear_buffer(int id)
 238 {
 239         my_id = id;
 240         if (option_project == PROJ_KERNEL) {
 241                 add_function_assign_hook("kmalloc", &match_alloc, NULL);
 242                 add_function_hook("usb_control_msg", &match_usb_control_msg, NULL);
 243         }
 244         add_modification_hook(my_id, &reset_initialized);
 245
 246         select_return_states_hook(PARAM_CLEARED, &db_param_cleared);
 247 }
 248