check_bit_shift.c

   1 /*
   2  * Copyright (C) 2012 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 /*
  19  * This test is used to warn about mixups between bit shifters and bit flags.
  20  *
  21  */
  22
  23 #include "smatch.h"
  24 #include "smatch_function_hashtable.h"
  25
  26 static int my_id;
  27
  28 static DEFINE_HASHTABLE_INSERT(insert_struct, char, int);
  29 static DEFINE_HASHTABLE_SEARCH(search_struct, char, int);
  30 static struct hashtable *shifters;
  31
  32 static const char *get_shifter(struct expression *expr)
  33 {
  34         const char *name;
  35         sval_t expr_value;
  36         const int *shifter_value;
  37
  38         expr = strip_expr(expr);
  39         if (expr->type != EXPR_VALUE)
  40                 return NULL;
  41         if (!get_value(expr, &expr_value))
  42                 return NULL;
  43         name = pos_ident(expr->pos);
  44         if (!name)
  45                 return NULL;
  46         shifter_value = search_struct(shifters, (char *)name);
  47         if (!shifter_value)
  48                 return NULL;
  49         if (sval_cmp_val(expr_value, *shifter_value) != 0)
  50                 return NULL;
  51         return name;
  52 }
  53
  54 static void match_assign(struct expression *expr)
  55 {
  56         const char *name;
  57
  58         if (expr->op != SPECIAL_OR_ASSIGN)
  59                 return;
  60         if (positions_eq(expr->pos, expr->right->pos))
  61                 return;
  62         name = get_shifter(expr->right);
  63         if (!name)
  64                 return;
  65
  66         sm_warning("'%s' is a shifter (not for '%s').",
  67                         name, show_special(expr->op));
  68 }
  69
  70 static void match_binop(struct expression *expr)
  71 {
  72         const char *name;
  73
  74         if (positions_eq(expr->pos, expr->right->pos))
  75                 return;
  76         if (expr->op != '&')
  77                 return;
  78         name = get_shifter(expr->right);
  79         if (!name)
  80                 return;
  81
  82         sm_warning("bit shifter '%s' used for logical '%s'",
  83                         name, show_special(expr->op));
  84 }
  85
  86 static void register_shifters(void)
  87 {
  88         char filename[256];
  89         struct token *token;
  90         char *name;
  91         int *val;
  92
  93         snprintf(filename, sizeof(filename), "%s.bit_shifters", option_project_str);
  94         token = get_tokens_file(filename);
  95         if (!token)
  96                 return;
  97         if (token_type(token) != TOKEN_STREAMBEGIN)
  98                 return;
  99         token = token->next;
 100         while (token_type(token) != TOKEN_STREAMEND) {
 101                 if (token_type(token) != TOKEN_IDENT)
 102                         return;
 103                 name = alloc_string(show_ident(token->ident));
 104                 token = token->next;
 105                 if (token_type(token) != TOKEN_NUMBER)
 106                         return;
 107                 val = malloc(sizeof(int));
 108                 *val = atoi(token->number);
 109                 insert_struct(shifters, name, val);
 110                 token = token->next;
 111         }
 112         clear_token_alloc();
 113 }
 114
 115 static void match_binop_info(struct expression *expr)
 116 {
 117         char *name;
 118         sval_t sval;
 119
 120         if (positions_eq(expr->pos, expr->right->pos))
 121                 return;
 122         if (expr->op != SPECIAL_LEFTSHIFT)
 123                 return;
 124         if (expr->right->type != EXPR_VALUE)
 125                 return;
 126         name = pos_ident(expr->right->pos);
 127         if (!name)
 128                 return;
 129         if (!get_value(expr->right, &sval))
 130                 return;
 131         sm_msg("info: bit shifter '%s' '%s'", name, sval_to_str(sval));
 132 }
 133
 134 static void match_call(const char *fn, struct expression *expr, void *_arg_no)
 135 {
 136         struct expression *arg_expr;
 137         int arg_no = PTR_INT(_arg_no);
 138         sval_t sval;
 139         char *name;
 140
 141         arg_expr = get_argument_from_call_expr(expr->args, arg_no);
 142         if (positions_eq(expr->pos, arg_expr->pos))
 143                 return;
 144         name = pos_ident(arg_expr->pos);
 145         if (!name)
 146                 return;
 147         if (!get_value(arg_expr, &sval))
 148                 return;
 149         sm_msg("info: bit shifter '%s' '%s'", name, sval_to_str(sval));
 150 }
 151
 152 void check_bit_shift(int id)
 153 {
 154         my_id = id;
 155
 156         shifters = create_function_hashtable(5000);
 157         register_shifters();
 158
 159         add_hook(&match_assign, ASSIGNMENT_HOOK);
 160         add_hook(&match_binop, BINOP_HOOK);
 161
 162         if (option_info) {
 163                 add_hook(&match_binop_info, BINOP_HOOK);
 164                 if (option_project == PROJ_KERNEL) {
 165                         add_function_hook("set_bit", &match_call, INT_PTR(0));
 166                         add_function_hook("test_bit", &match_call, INT_PTR(0));
 167                 }
 168         }
 169 }