check_param_range.c

   1 /*
   2  * sparse/check_param_range.c
   3  *
   4  * Copyright (C) 2012 Oracle.
   5  *
   6  * Licensed under the Open Software License version 1.1
   7  *
   8  */
   9
  10 #include "smatch.h"
  11 #include "smatch_extra.h"
  12 #include "smatch_slist.h"
  13
  14 static int my_id;
  15
  16 static int have_returned_zero;
  17 static struct range_list *param_constraints[16];
  18
  19
  20 static struct statement *prev_statement(void)
  21 {
  22         struct statement *tmp;
  23         int i;
  24
  25         i = 0;
  26         FOR_EACH_PTR_REVERSE(big_statement_stack, tmp) {
  27                 if (i++ == 1)
  28                         return tmp;
  29         } END_FOR_EACH_PTR_REVERSE(tmp);
  30         return NULL;
  31 }
  32
  33 /*
  34  * on_main_path() is supposed to check for nesting.  As a hack it just counts
  35  * the current indent level.
  36  */
  37 static int on_main_path(struct expression *expr)
  38 {
  39         if (expr->pos.pos == 24)
  40                 return 1;
  41         return 0;
  42 }
  43
  44 static int is_error_value(struct expression *ret_value)
  45 {
  46         long long val;
  47         char *name;
  48
  49         if (!ret_value)
  50                 return 0;
  51
  52         if (ret_value->type != EXPR_PREOP || ret_value->op != '-')
  53                 return 0;
  54
  55         if (!get_value(ret_value, &val))
  56                 return 0;
  57         if (val < -4095 || val >= 0)
  58                 return 0;
  59
  60         name = pos_ident(ret_value->unop->pos);
  61         if (!name)
  62                 return 0;
  63         if (name[0] == 'E')
  64                 return 1;
  65         return 0;
  66 }
  67
  68 static struct expression *get_param(struct expression *expr)
  69 {
  70         struct symbol *sym;
  71         struct symbol *tmp;
  72
  73         expr = strip_expr(expr);
  74         if (!expr || expr->type != EXPR_SYMBOL)
  75                 return 0;
  76
  77         sym = expr->symbol;
  78         FOR_EACH_PTR(cur_func_sym->ctype.base_type->arguments, tmp) {
  79                 if (tmp == sym)
  80                         return expr;
  81         } END_FOR_EACH_PTR(tmp);
  82
  83         return NULL;
  84 }
  85
  86 static int get_param_num(struct expression *expr)
  87 {
  88         struct symbol *sym;
  89         struct symbol *tmp;
  90         int i;
  91
  92         expr = strip_expr(expr);
  93         if (!expr || expr->type != EXPR_SYMBOL)
  94                 return -1;
  95
  96         sym = expr->symbol;
  97         i = 0;
  98         FOR_EACH_PTR(cur_func_sym->ctype.base_type->arguments, tmp) {
  99                 if (tmp == sym)
 100                         return i;
 101                 i++;
 102         } END_FOR_EACH_PTR(tmp);
 103
 104         return -1;
 105 }
 106
 107 static void add_param_constraint(int idx, struct range_list *rl)
 108 {
 109         if (!param_constraints[idx]) {
 110                 param_constraints[idx] = rl;
 111                 return;
 112         }
 113         param_constraints[idx] = range_list_union(param_constraints[idx], rl);
 114 }
 115
 116 static void handle_condition(struct expression *expr)
 117 {
 118         struct sm_state *sm;
 119         struct expression *param;
 120         struct state_list *slist = NULL;
 121         char *name;
 122         struct symbol *sym;
 123
 124         expr = strip_expr(expr);
 125         if (!expr)
 126                 return;
 127
 128         switch (expr->type) {
 129         case EXPR_LOGICAL:
 130                 if (expr->op == SPECIAL_LOGICAL_OR) {
 131                         handle_condition(expr->left);
 132                         handle_condition(expr->right);
 133                 }
 134                 return;
 135         case EXPR_COMPARE:
 136                 param = get_param(expr->left);
 137                 if (param)
 138                         break;
 139                 param = get_param(expr->right);
 140                 if (param)
 141                         break;
 142                 return;
 143         case EXPR_PREOP:
 144                 if (expr->op == '!') {
 145                         param = get_param(expr->unop);
 146                         if (param)
 147                                 break;
 148                 }
 149                 return;
 150         case EXPR_SYMBOL:
 151                 param = get_param(expr);
 152                 if (param)
 153                         break;
 154                 return;
 155         default:
 156                 return;
 157         }
 158
 159         name = get_variable_from_expr(param, &sym);
 160         if (!name || !sym)
 161                 goto free;
 162
 163         __push_fake_cur_slist();
 164         __split_whole_condition(expr);
 165
 166         sm = get_sm_state(SMATCH_EXTRA, name, sym);
 167         if (sm) {
 168                 int num;
 169
 170                 num = get_param_num(param);
 171                 add_param_constraint(num, estate_ranges(sm->state));
 172         }
 173
 174         __push_true_states();
 175         __use_false_states();
 176         __merge_true_states();
 177         slist = __pop_fake_cur_slist();
 178
 179 free:
 180         free_string(name);
 181         free_slist(&slist);
 182 }
 183
 184 static void match_return(struct expression *ret_value)
 185 {
 186         struct statement *stmt;
 187
 188         if (have_returned_zero)
 189                 return;
 190         if (possibly_true(ret_value, SPECIAL_EQUAL, zero_expr())) {
 191                 have_returned_zero = 1;
 192                 return;
 193         }
 194
 195         if (!on_main_path(ret_value))  /* should we just set have_returned_zero here? */
 196                 return;
 197
 198         if (!is_error_value(ret_value))
 199                 return;
 200         stmt = prev_statement();
 201         if (!stmt || stmt->type != STMT_IF)
 202                 return;
 203         handle_condition(stmt->if_conditional);
 204 }
 205
 206 static void match_end_func(struct symbol *sym)
 207 {
 208         int i;
 209
 210         for (i = 0; i < ARRAY_SIZE(param_constraints); i++) {
 211                 if (!param_constraints[i])
 212                         continue;
 213                 if (is_whole_range_rl(param_constraints[i]))
 214                         continue;
 215                 sm_msg("info: param %d range '%s' implies error return",
 216                                 i, show_ranges(param_constraints[i]));
 217         }
 218
 219         have_returned_zero = 0;
 220         for (i = 0; i < ARRAY_SIZE(param_constraints); i++)
 221                 param_constraints[i] = NULL;
 222 }
 223
 224 void check_param_range(int id)
 225 {
 226         if (!option_info || option_project != PROJ_KERNEL)
 227                 return;
 228
 229         my_id = id;
 230         add_hook(&match_return, RETURN_HOOK);
 231         add_hook(&match_end_func, END_FUNC_HOOK);
 232 }