smatch_clear_buffer.c

   1 /*
   2  * smatch/smatch_clear_structs.c
   3  *
   4  * Copyright (C) 2013 Oracle.
   5  *
   6  * Licensed under the Open Software License version 1.1
   7  *
   8  */
   9
  10 #include "smatch.h"
  11 #include "smatch_slist.h"
  12 #include "smatch_extra.h"
  13
  14 static int my_id;
  15
  16 STATE(uninitialized);
  17 STATE(initialized);
  18
  19 static int type_sym_array(struct expression *expr)
  20 {
  21         struct symbol *type;
  22
  23         /* remove casting the array to a pointer */
  24         expr = strip_expr(expr);
  25         type = get_type(expr);
  26         if (type && type->type == SYM_ARRAY)
  27                 return 1;
  28         return 0;
  29 }
  30
  31 static void set_members_uninitialized(struct expression *expr)
  32 {
  33         struct symbol *type, *sym, *tmp;
  34         char *name;
  35         char buf[256];
  36
  37         type = get_type(expr);
  38         if (!type)
  39                 return;
  40
  41         if (type->type != SYM_PTR)
  42                 return;
  43         type = get_real_base_type(type);
  44
  45         name = expr_to_var_sym(expr, &sym);
  46         if (!name || !sym)
  47                 goto free;
  48
  49         FOR_EACH_PTR(type->symbol_list, tmp) {
  50                 if (!tmp->ident)
  51                         continue;
  52                 snprintf(buf, sizeof(buf), "%s->%s", name, tmp->ident->name);
  53                 set_state(my_id, buf, sym, &uninitialized);
  54         } END_FOR_EACH_PTR(tmp);
  55
  56 free:
  57         free_string(name);
  58 }
  59
  60 static void initialize_struct_members(struct symbol *type, struct expression *expr, struct expression *to)
  61 {
  62         struct symbol *tmp;
  63         struct expression *member;
  64         struct expression *assign;
  65         int op = '*';
  66
  67         if (expr->type == EXPR_PREOP && expr->op == '&') {
  68                 expr = strip_expr(expr->unop);
  69                 op = '.';
  70         }
  71
  72         FOR_EACH_PTR(type->symbol_list, tmp) {
  73                 if (!tmp->ident)
  74                         continue;
  75                 member = member_expression(expr, op, tmp->ident);
  76                 if (type_sym_array(member))
  77                         continue;
  78
  79                 /*
  80                  * FIXME: the problem here is that sometimes we have:
  81                  *       memset(&my_struct, 0xff, sizeof(my_struct));
  82                  * and my_struct->foo is a 1 bit bitfield.  There is a check
  83                  * which complains that "255 doesn't fit in ->foo".
  84                  *
  85                  * For now I just have this ugly hack.  But really it's not
  86                  * handling the memset(..., 0xff, ...) correctly at all so one
  87                  * more hack barely makes a difference.
  88                  *
  89                  */
  90                 if (to && type_positive_bits(get_type(member)) >= type_positive_bits(get_type(to)))
  91                         assign = assign_expression(member, to);
  92                 else
  93                         assign = assign_expression(member, member);
  94
  95                 __split_expr(assign);
  96         } END_FOR_EACH_PTR(tmp);
  97 }
  98
  99 static void initialize_base_type(struct symbol *type, struct expression *expr,
 100                 struct expression *to)
 101 {
 102         struct expression *assign;
 103
 104         if (type == &void_ctype)
 105                 return;
 106         if (expr->type == EXPR_PREOP && expr->op == '&')
 107                 expr = strip_expr(expr->unop);
 108         else
 109                 expr = deref_expression(expr);
 110         if (!to)
 111                 to = expr;
 112         /* FIXME: see the FIXME in initialize_struct_members() */
 113         if (type_positive_bits(get_type(expr)) < type_positive_bits(get_type(to)))
 114                 to = expr;
 115         assign = assign_expression(expr, to);
 116         __split_expr(assign);
 117 }
 118
 119 void set_initialized(struct expression *expr, struct expression *to)
 120 {
 121         struct symbol *type;
 122
 123         expr = strip_expr(expr);
 124
 125         type = get_type(expr);
 126         if (!type || type->type != SYM_PTR)
 127                 return;
 128         type = get_real_base_type(type);
 129         if (!type)
 130                 return;
 131         if (type->type == SYM_BASETYPE)
 132                 initialize_base_type(type, expr, to);
 133         if (type->type == SYM_STRUCT) {
 134                 if (expr->type != EXPR_PREOP || expr->op != '&')
 135                         expr = deref_expression(expr);
 136                 initialize_struct_members(type, expr, to);
 137         }
 138 }
 139
 140 int is_uninitialized(struct expression *expr)
 141 {
 142         struct sm_state *sm;
 143
 144         sm = get_sm_state_expr(my_id, expr);
 145         if (!sm)
 146                 return 0;
 147         return slist_has_state(sm->possible, &uninitialized);
 148 }
 149
 150 int has_uninitialized_members(struct expression *expr)
 151 {
 152         struct symbol *sym;
 153         struct symbol *tmp;
 154         char *name;
 155         char buf[256];
 156         struct sm_state *sm;
 157
 158         sym = get_type(expr);
 159         if (!sym)
 160                 return 0;
 161
 162         if (sym->type == SYM_PTR)
 163                 sym = get_real_base_type(sym);
 164
 165         name = expr_to_var(expr);
 166         if (!name)
 167                 return 0;
 168
 169         FOR_EACH_PTR(sym->symbol_list, tmp) {
 170                 if (!tmp->ident)
 171                         continue;
 172                 snprintf(buf, sizeof(buf), "%s->%s", name, tmp->ident->name);
 173                 sm = get_sm_state(my_id, buf, sym);
 174                 if (!sm)
 175                         continue;
 176                 if (slist_has_state(sm->possible, &uninitialized))
 177                         return 1;
 178         } END_FOR_EACH_PTR(tmp);
 179
 180         free_string(name);
 181         return 0;
 182 }
 183
 184 static void match_assign(struct expression *expr)
 185 {
 186         struct symbol *type;
 187
 188         type = get_type(expr->left);
 189         if (!type || type->type != SYM_STRUCT)
 190                 return;
 191         initialize_struct_members(type, expr->left, NULL);
 192 }
 193
 194 static void match_alloc(const char *fn, struct expression *expr, void *_size_arg)
 195 {
 196         set_members_uninitialized(expr->left);
 197 }
 198
 199 static void db_param_cleared(struct expression *expr, int param, char *key, char *value)
 200 {
 201         struct expression *arg;
 202
 203         while (expr->type == EXPR_ASSIGNMENT)
 204                 expr = strip_expr(expr->right);
 205         if (expr->type != EXPR_CALL)
 206                 return;
 207
 208         arg = get_argument_from_call_expr(expr->args, param);
 209         if (!arg)
 210                 return;
 211
 212         if (strcmp(value, "0") == 0)
 213                 set_initialized(arg, zero_expr());
 214         else
 215                 set_initialized(arg, NULL);
 216 }
 217
 218 static void match_memset(const char *fn, struct expression *expr, void *_size_arg)
 219 {
 220         struct expression *buf;
 221         struct expression *val;
 222
 223         buf = get_argument_from_call_expr(expr->args, 0);
 224         val = get_argument_from_call_expr(expr->args, 1);
 225
 226         set_initialized(buf, val);
 227 }
 228
 229 static void match_memcpy(const char *fn, struct expression *expr, void *_arg)
 230 {
 231         struct expression *buf;
 232         int arg = PTR_INT(_arg);
 233
 234         buf = get_argument_from_call_expr(expr->args, arg);
 235
 236         set_initialized(buf, NULL);
 237 }
 238
 239 static void reset_initialized(struct sm_state *sm)
 240 {
 241         set_state(my_id, sm->name, sm->sym, &initialized);
 242 }
 243
 244 #define USB_DIR_IN 0x80
 245 static void match_usb_control_msg(const char *fn, struct expression *expr, void *_size_arg)
 246 {
 247         struct expression *inout;
 248         struct expression *buf;
 249         sval_t sval;
 250
 251         inout = get_argument_from_call_expr(expr->args, 3);
 252         buf = get_argument_from_call_expr(expr->args, 6);
 253
 254         if (get_value(inout, &sval) && !(sval.uvalue & USB_DIR_IN))
 255                 return;
 256
 257         set_initialized(buf, NULL);
 258 }
 259
 260 static void register_clears_param(void)
 261 {
 262         struct token *token;
 263         char name[256];
 264         const char *function;
 265         int param;
 266
 267         if (option_project == PROJ_NONE)
 268                 return;
 269
 270         snprintf(name, 256, "%s.clears_argument", option_project_str);
 271
 272         token = get_tokens_file(name);
 273         if (!token)
 274                 return;
 275         if (token_type(token) != TOKEN_STREAMBEGIN)
 276                 return;
 277         token = token->next;
 278         while (token_type(token) != TOKEN_STREAMEND) {
 279                 if (token_type(token) != TOKEN_IDENT)
 280                         return;
 281                 function = show_ident(token->ident);
 282                 token = token->next;
 283                 if (token_type(token) != TOKEN_NUMBER)
 284                         return;
 285                 param = atoi(token->number);
 286                 add_function_hook(function, &match_memcpy, INT_PTR(param));
 287                 token = token->next;
 288         }
 289         clear_token_alloc();
 290 }
 291
 292 void register_clear_buffer(int id)
 293 {
 294         my_id = id;
 295         if (option_project == PROJ_KERNEL) {
 296                 add_function_assign_hook("kmalloc", &match_alloc, NULL);
 297                 add_function_hook("usb_control_msg", &match_usb_control_msg, NULL);
 298         }
 299         add_modification_hook(my_id, &reset_initialized);
 300         add_hook(&match_assign, ASSIGNMENT_HOOK);
 301         add_function_hook("memset", &match_memset, NULL);
 302         add_function_hook("memcpy", &match_memcpy, INT_PTR(0));
 303         add_function_hook("memmove", &match_memcpy, INT_PTR(0));
 304         register_clears_param();
 305
 306         add_db_return_states_callback(PARAM_CLEARED, &db_param_cleared);
 307 }
 308