smatch_dereference.c

   1 /*
   2  * Copyright (C) 2021 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_extra.h"
  20
  21 static int my_id;
  22 static struct expr_fn_list *deref_hooks;
  23
  24 void add_dereference_hook(expr_func *fn)
  25 {
  26         add_ptr_list(&deref_hooks, fn);
  27 }
  28
  29 static void call_deref_hooks(struct expression *expr)
  30 {
  31         if (__in_fake_assign || __in_fake_parameter_assign)
  32                 return;
  33         if (!expr)
  34                 return;
  35
  36         call_expr_fns(deref_hooks, expr);
  37 }
  38
  39 static void match_dereference(struct expression *expr)
  40 {
  41         struct expression *p, *tmp;
  42
  43         if (expr->type != EXPR_PREOP ||
  44             expr->op != '*')
  45                 return;
  46         p = strip_expr(expr->unop);
  47         if (!is_pointer(p))
  48                 return;
  49         call_deref_hooks(p);
  50
  51         tmp = get_assigned_expr(p);
  52         if (!tmp)
  53                 return;
  54         /*
  55          * Imagine we have:
  56          * p = &foo->bar;
  57          * x = p->whatever;
  58          *
  59          * Note that we only care about address assignments because other
  60          * dereferences would have been handled already.
  61          */
  62         p = strip_expr(tmp->unop);
  63         if (tmp->type != EXPR_PREOP || tmp->op != '&')
  64                 return;
  65         p = strip_expr(tmp->unop);
  66         if (p->type != EXPR_DEREF)
  67                 return;
  68         p = strip_expr(p->deref);
  69         if (p->type != EXPR_PREOP || p->op != '*')
  70                 return;
  71         p = strip_expr(p->unop);
  72         if (!is_pointer(p))
  73                 return;
  74         call_deref_hooks(p);
  75 }
  76
  77 static void match_pointer_as_array(struct expression *expr)
  78 {
  79         if (!is_array(expr))
  80                 return;
  81         call_deref_hooks(get_array_base(expr));
  82 }
  83
  84 static void set_param_dereferenced(struct expression *call, struct expression *arg, char *key, char *unused)
  85 {
  86         struct expression *deref;
  87
  88         deref = gen_expression_from_key(arg, key);
  89         if (!deref)
  90                 return;
  91
  92         call_deref_hooks(deref);
  93 }
  94
  95 void register_dereferences(int id)
  96 {
  97         my_id = id;
  98
  99         add_hook(&match_dereference, DEREF_HOOK);
 100         add_hook(&match_pointer_as_array, OP_HOOK);
 101         select_return_implies_hook_early(DEREFERENCE, &set_param_dereferenced);
 102 }
 103