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