check_template.c

   1 /*
   2  * smatch/check_template.c
   3  *
   4  * Copyright (C) 20XX Your Name.
   5  *
   6  * Licensed under the Open Software License version 1.1
   7  *
   8  */
   9
  10 /*
  11  * First of all, it's best if you lower your expectations from finding
  12  * errors to just finding suspicious code.  There tends to be a lot
  13  * of false positives so having low expectations helps.
  14  *
  15  * For this test let's look for functions that return a negative value
  16  * with a semaphore held.
  17  *
  18  * This is just a template check.  It's designed for teaching
  19  * only and is deliberately less useful than it could be.  check_locking.c
  20  * is a better real world test.
  21  *
  22  * The biggest short coming is that it assumes a function isn't supposed
  23  * to return negative with a lock held.  Also it assumes the function was
  24  * called without the lock held. It would be better if it handled the stuff
  25  * like this:
  26  *     ret = -ENOMEM;
  27  *     return ret;
  28  * Another idea would be to test other kinds of locks besides just semaphores.
  29  *
  30  */
  31
  32 #include "smatch.h"
  33 #include "smatch_slist.h"
  34
  35 static int my_id;
  36
  37 STATE(lock);
  38 STATE(unlock);
  39
  40 /*
  41  * unmatched_state() deals with the case where code is known to be
  42  * locked on one path but not known on the other side of a merge.  Here
  43  * we assume it's the opposite.
  44  */
  45
  46 static struct smatch_state *unmatched_state(struct sm_state *sm)
  47 {
  48         if (sm->state == &lock)
  49                 return &unlock;
  50         if (sm->state == &unlock)
  51                 return &lock;
  52         return &undefined;
  53 }
  54
  55 static void match_call(struct expression *expr)
  56 {
  57         char *fn_name;
  58         struct expression *sem_expr;
  59         char *sem_name;
  60
  61         fn_name = get_variable_from_expr(expr->fn, NULL);
  62         if (!fn_name || (strcmp(fn_name, "down") && strcmp(fn_name, "up")))
  63                 goto free_fn;
  64
  65         sem_expr = get_argument_from_call_expr(expr->args, 0);
  66         sem_name = get_variable_from_expr(sem_expr, NULL);
  67         if (!strcmp(fn_name, "down")) {
  68                 set_state(my_id, sem_name, NULL, &lock);
  69         } else {
  70                 set_state(my_id, sem_name, NULL, &unlock);
  71         }
  72         free_string(sem_name);
  73 free_fn:
  74         free_string(fn_name);
  75 }
  76
  77 static void match_return(struct expression *ret_value)
  78 {
  79         sval_t ret_val;
  80         struct state_list *slist;
  81         struct sm_state *tmp;
  82
  83         if (!get_value(ret_value, &ret_val) || sval_cmp_val(ret_val, 0) >= 0)
  84                 return;
  85
  86         slist = get_all_states(my_id);
  87         FOR_EACH_PTR(slist, tmp) {
  88                 if (tmp->state != &unlock)
  89                         sm_msg("warn: returned negative with %s semaphore held",
  90                                    tmp->name);
  91         } END_FOR_EACH_PTR(tmp);
  92         free_slist(&slist);
  93 }
  94
  95 void check_template(int id)
  96 {
  97         my_id = id;
  98         add_unmatched_state_hook(my_id, &unmatched_state);
  99         add_hook(&match_call, FUNCTION_CALL_HOOK);
 100         add_hook(&match_return, RETURN_HOOK);
 101 }