check_returns_negative_error_code.c

   1 /*
   2  * Copyright (C) 2022 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(error_code);
  25
  26 static void clear_state(struct sm_state *sm, struct expression *mod_expr)
  27 {
  28         set_state(my_id, sm->name, sm->sym, &undefined);
  29 }
  30
  31 static void pre_merge_hook(struct sm_state *cur, struct sm_state *other)
  32 {
  33         struct sm_state *sm;
  34         sval_t sval;
  35
  36         sm = get_sm_state(SMATCH_EXTRA, cur->name, cur->sym);
  37         if (!sm || !estate_rl(sm->state))
  38                 return;
  39         if (type_unsigned(estate_type(sm->state)))
  40                 return;
  41         sval = estate_min(sm->state);
  42         if (sval.value == 0)
  43                 set_state(my_id, cur->name, cur->sym, &undefined);
  44 }
  45
  46 static bool is_error_macro(struct expression *expr)
  47 {
  48         char *macro;
  49         sval_t sval;
  50
  51         if (!expr)
  52                 return false;
  53         if (expr->type != EXPR_PREOP || expr->op != '-')
  54                 return false;
  55
  56         if (!get_value(expr, &sval))
  57                 return false;
  58         if (sval.value < -4095 || sval.value >= 0)
  59                 return false;
  60
  61         expr = expr->unop;
  62         macro = get_macro_name(expr->pos);
  63         if (!macro || macro[0] != 'E')
  64                 return false;
  65
  66         return true;
  67 }
  68
  69 static void match_assign(struct expression *expr)
  70 {
  71         if (expr->op != '=')
  72                 return;
  73
  74         if (!is_error_macro(expr->right))
  75                 return;
  76
  77         set_state_expr(my_id, expr->left, &error_code);
  78 }
  79
  80 static void match_condition(struct expression *expr)
  81 {
  82         if (expr->type != EXPR_COMPARE)
  83                 return;
  84         if (expr->op != '<' && expr->op != SPECIAL_LTE)
  85                 return;
  86         if (!expr_is_zero(expr->right))
  87                 return;
  88
  89         set_true_false_states_expr(my_id, expr->left, NULL, &undefined);
  90 }
  91
  92 static bool is_empty_state(struct expression *expr)
  93 {
  94         struct smatch_state *state;
  95
  96         state = get_extra_state(expr);
  97         if (!state)
  98                 return false;
  99         if (estate_rl(state))
 100                 return false;
 101         return true;
 102 }
 103
 104 bool holds_kernel_error_codes(struct expression *expr)
 105 {
 106         struct range_list *rl;
 107
 108         if (!expr)
 109                 return false;
 110
 111         if (is_error_macro(expr))
 112                 return true;
 113
 114         if (is_empty_state(expr))
 115                 return false;
 116
 117         if (get_implied_rl(expr, &rl)) {
 118                 if (rl_min(rl).value >= 0 &&
 119                     rl_max(rl).uvalue <= INT_MAX)
 120                         return false;
 121
 122                 if (type_positive_bits(rl_type(rl)) >= 63 &&
 123                     !sval_is_negative(rl_min(rl)) &&
 124                     rl_max(rl).uvalue <= UINT_MAX)
 125                         return false;
 126         }
 127
 128         return expr_has_possible_state(my_id, expr, &error_code);
 129 }
 130
 131 static void match_return(int return_id, char *return_ranges, struct expression *expr)
 132 {
 133         if (!expr)
 134                 return;
 135
 136         if (!holds_kernel_error_codes(expr))
 137                 return;
 138
 139         sql_insert_return_states(return_id, return_ranges, NEGATIVE_ERROR,
 140                                  -1, "$", "");
 141 }
 142
 143 static void set_error_code(struct expression *expr, const char *name, struct symbol *sym, void *data)
 144 {
 145         set_state(my_id, name, sym, &error_code);
 146 }
 147
 148 void check_returns_negative_error_code(int id)
 149 {
 150         my_id = id;
 151
 152         if (option_project != PROJ_KERNEL)
 153                 return;
 154
 155         add_hook(&match_assign, ASSIGNMENT_HOOK);
 156         add_hook(&match_condition, CONDITION_HOOK);
 157         add_modification_hook(my_id, &clear_state);
 158         add_pre_merge_hook(my_id, &pre_merge_hook);
 159         add_split_return_callback(&match_return);
 160         select_return_param_key(NEGATIVE_ERROR, &set_error_code);
 161 }