smatch_strlen.c

   1 /*
   2  * smatch/smatch_strlen.c
   3  *
   4  * Copyright (C) 2013 Oracle.
   5  *
   6  * Licensed under the Open Software License version 1.1
   7  *
   8  */
   9
  10 #include <stdlib.h>
  11 #include <errno.h>
  12 #include "parse.h"
  13 #include "smatch.h"
  14 #include "smatch_slist.h"
  15 #include "smatch_extra.h"
  16
  17 /*
  18  * The trick with the my_equiv_id is that if we have:
  19  * foo = strlen(bar);
  20  * We don't know at that point what the strlen() is but we know it's equivalent
  21  * to "foo" so maybe we can find the value of "foo" later.
  22  */
  23 static int my_equiv_id;
  24
  25 static void set_strlen_equiv_undefined(struct sm_state *sm, struct expression *mod_expr)
  26 {
  27         set_state(sm->owner, sm->name, sm->sym, &undefined);
  28 }
  29
  30 static void match_strlen(const char *fn, struct expression *expr, void *unused)
  31 {
  32         struct expression *right;
  33         struct expression *str;
  34         struct expression *len_expr;
  35         char *len_name;
  36         struct smatch_state *state;
  37
  38         right = strip_expr(expr->right);
  39         str = get_argument_from_call_expr(right->args, 0);
  40         len_expr = strip_expr(expr->left);
  41
  42         len_name = expr_to_var(len_expr);
  43         if (!len_name)
  44                 return;
  45
  46         state = __alloc_smatch_state(0);
  47         state->name = len_name;
  48         state->data = len_expr;
  49
  50         set_state_expr(my_equiv_id, str, state);
  51 }
  52
  53 static int get_strlen_from_string(struct expression *expr, struct range_list **rl)
  54 {
  55         sval_t sval;
  56         int len;
  57
  58         len = expr->string->length;
  59         sval = sval_type_val(&int_ctype, len - 1);
  60         *rl = alloc_rl(sval, sval);
  61         return 1;
  62 }
  63
  64 int get_implied_strlen(struct expression *expr, struct range_list **rl)
  65 {
  66         struct smatch_state *state;
  67
  68         *rl = NULL;
  69
  70         switch (expr->type) {
  71         case EXPR_STRING:
  72                 return get_strlen_from_string(expr, rl);
  73         }
  74
  75         state = get_state_expr(my_equiv_id, expr);
  76         if (!state || !state->data)
  77                 return 0;
  78         if (!get_implied_rl((struct expression *)state->data, rl))
  79                 return 0;
  80         return 1;
  81 }
  82
  83 int get_size_from_strlen(struct expression *expr)
  84 {
  85         struct range_list *rl;
  86         sval_t max;
  87
  88         if (!get_implied_strlen(expr, &rl))
  89                 return 0;
  90         max = rl_max(rl);
  91         if (sval_is_negative(max) || sval_is_max(max))
  92                 return 0;
  93
  94         return max.value + 1; /* add one because strlen doesn't include the NULL */
  95 }
  96
  97 void register_strlen(int id)
  98 {
  99         my_equiv_id = id;
 100         add_function_assign_hook("strlen", &match_strlen, NULL);
 101         add_modification_hook(my_equiv_id, &set_strlen_equiv_undefined);
 102 }
 103