smatch_kernel_atomic_dec_test_path.c

   1 /*
   2  * Copyright (C) 2016 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 #include "smatch_slist.h"
  21
  22 static int my_id;
  23
  24 STATE(zero_path);
  25
  26 static void handle_test_functions(struct expression *expr)
  27 {
  28         struct expression *tmp;
  29         struct statement *stmt;
  30         int count = 0;
  31
  32         while (expr && expr->type == EXPR_ASSIGNMENT && expr->op == '=')
  33                 expr = strip_expr(expr->right);
  34
  35         if (!expr ||
  36             expr->type != EXPR_CALL ||
  37             expr->fn->type != EXPR_SYMBOL ||
  38             !expr->fn->symbol_name)
  39                 return;
  40         if (!strstr(expr->fn->symbol_name->name, "test"))
  41                 return;
  42
  43         while ((tmp = expr_get_parent_expr(expr))) {
  44                 expr = tmp;
  45                 if (count++ > 5)
  46                         break;
  47         }
  48
  49         /*
  50          * FIXME: This doesn't work for assignments like:
  51          *
  52          * free = dec_and_test(foo);
  53          * if (free)
  54          *      free_thing(x);
  55          *
  56          * Maybe we should just say everything is on an atomic_dec path at this
  57          * point.  That probably works fine.  The other solution would be to
  58          * store the variable and look up the state of it or something...
  59          *
  60          */
  61
  62         stmt = expr_get_parent_stmt(expr);
  63         if (!stmt || stmt->type != STMT_IF) {
  64                 /* See above comment.  I decided to go with the easy option */
  65                 set_state(my_id, "dec_path", NULL, &zero_path);
  66                 return;
  67         }
  68
  69         set_true_false_states(my_id, "dec_path", NULL, &zero_path, NULL);
  70 }
  71
  72 static void match_dec(struct expression *expr, const char *name, struct symbol *sym)
  73 {
  74         handle_test_functions(expr);
  75 }
  76
  77 int on_atomic_dec_path(void)
  78 {
  79         return get_state(my_id, "dec_path", NULL) == &zero_path;
  80 }
  81
  82 void register_kernel_atomic_dec_test_path(int id)
  83 {
  84         my_id = id;
  85
  86         if (option_project != PROJ_KERNEL)
  87                 return;
  88
  89         add_refcount_dec_hook(&match_dec);
  90 }