check_check_deref.c

   1 /*
   2  * sparse/check_check_deref.c
   3  *
   4  * Copyright (C) 2010 Dan Carpenter.
   5  *
   6  * Licensed under the Open Software License version 1.1
   7  *
   8  */
   9
  10 /*
  11  * This is like check_deref_check.c except that it complains about code like:
  12  * if (a)
  13  *        a->foo = 42;
  14  * a->bar = 7;
  15  *
  16  * Of course, Smatch has complained about these for forever but the problem is
  17  * the old scripts were too messy and complicated and generated too many false
  18  * positives.
  19  *
  20  * This check is supposed to be simpler because it only looks for one kind of
  21  * null dereference bug instead of every kind.  It also gets rid of the false
  22  * positives caused by the checks that happen inside macros.
  23  *
  24  */
  25
  26 #include "smatch.h"
  27 #include "smatch_slist.h"
  28 #include "smatch_extra.h"
  29
  30 static int my_id;
  31
  32 STATE(null);
  33 STATE(ok);
  34
  35 static void is_ok(struct sm_state *sm, struct expression *mod_expr)
  36 {
  37         set_state(my_id, sm->name, sm->sym, &ok);
  38 }
  39
  40 static void check_dereference(struct expression *expr)
  41 {
  42         struct sm_state *sm;
  43         struct sm_state *tmp;
  44
  45         expr = strip_expr(expr);
  46         if (getting_address())
  47                 return;
  48         sm = get_sm_state_expr(my_id, expr);
  49         if (!sm)
  50                 return;
  51         if (is_ignored(my_id, sm->name, sm->sym))
  52                 return;
  53         if (implied_not_equal(expr, 0))
  54                 return;
  55
  56         FOR_EACH_PTR(sm->possible, tmp) {
  57                 if (tmp->state == &merged)
  58                         continue;
  59                 if (tmp->state == &ok)
  60                         continue;
  61                 if (tmp->state == &null) {
  62                         sm_msg("error: we previously assumed '%s' could be null (see line %d)",
  63                                tmp->name, tmp->line);
  64                         add_ignore(my_id, sm->name, sm->sym);
  65                         return;
  66                 }
  67         } END_FOR_EACH_PTR(tmp);
  68 }
  69
  70 static void match_dereferences(struct expression *expr)
  71 {
  72         if (expr->type != EXPR_PREOP)
  73                 return;
  74         check_dereference(expr->unop);
  75 }
  76
  77 static void match_pointer_as_array(struct expression *expr)
  78 {
  79         if (!is_array(expr))
  80                 return;
  81         check_dereference(expr->unop->left);
  82 }
  83
  84 static void set_param_dereferenced(struct expression *arg, char *unused)
  85 {
  86         check_dereference(arg);
  87 }
  88
  89 static void match_condition(struct expression *expr)
  90 {
  91         if (get_macro_name(expr->pos))
  92                 return;
  93
  94         if (expr->type == EXPR_ASSIGNMENT) {
  95                 match_condition(expr->right);
  96                 match_condition(expr->left);
  97         }
  98         set_true_false_states_expr(my_id, expr, &ok, &null);
  99 }
 100
 101 void check_check_deref(int id)
 102 {
 103         my_id = id;
 104
 105         add_modification_hook(my_id, &is_ok);
 106         add_hook(&match_dereferences, DEREF_HOOK);
 107         add_hook(&match_pointer_as_array, OP_HOOK);
 108         select_call_implies_hook(DEREFERENCE, &set_param_dereferenced);
 109         add_hook(&match_condition, CONDITION_HOOK);
 110 }