smatch_untracked_param.c

   1 /*
   2  * Copyright (C) 2014 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  * Sometimes we aren't able to track a variable through a function call.  This
  20  * usually happens because a function changes too many variables so we give up.
  21  * Another reason this happens is because we call a function pointer and there
  22  * are too many functions which implement that function pointer so we give up.
  23  * Also maybe we don't have the database enabled.
  24  *
  25  * The goal here is to make a call back so what if we call:
  26  *
  27  *      frob(&foo);
  28  *
  29  * but we're not able to say what happens to "foo", then let's assume that we
  30  * don't know anything about "foo" if it's an untracked call.
  31  *
  32  */
  33
  34 #include "smatch.h"
  35 #include "smatch_slist.h"
  36 #include "smatch_extra.h"
  37
  38 static int my_id;
  39 static int tracked;
  40
  41 STATE(untracked);
  42 STATE(lost);
  43
  44 typedef void (untracked_hook)(struct expression *call, int param);
  45 DECLARE_PTR_LIST(untracked_hook_list, untracked_hook *);
  46 static struct untracked_hook_list *untracked_hooks;
  47 static struct untracked_hook_list *lost_hooks;
  48
  49 struct int_stack *tracked_stack;
  50
  51 void add_untracked_param_hook(void (func)(struct expression *call, int param))
  52 {
  53         untracked_hook **p = malloc(sizeof(untracked_hook *));
  54         *p = func;
  55         add_ptr_list(&untracked_hooks, p);
  56 }
  57
  58 static void call_untracked_callbacks(struct expression *expr, int param)
  59 {
  60         untracked_hook **fn;
  61
  62         FOR_EACH_PTR(untracked_hooks, fn) {
  63                 (*fn)(expr, param);
  64         } END_FOR_EACH_PTR(fn);
  65 }
  66
  67 void add_lost_param_hook(void (func)(struct expression *call, int param))
  68 {
  69         untracked_hook **p = malloc(sizeof(untracked_hook *));
  70         *p = func;
  71         add_ptr_list(&lost_hooks, p);
  72 }
  73
  74 static void call_lost_callbacks(struct expression *expr, int param)
  75 {
  76         untracked_hook **fn;
  77
  78         FOR_EACH_PTR(lost_hooks, fn) {
  79                 (*fn)(expr, param);
  80         } END_FOR_EACH_PTR(fn);
  81 }
  82
  83 static void assume_tracked(struct expression *call_expr, int param, char *key, char *value)
  84 {
  85         tracked = 1;
  86 }
  87
  88 static void mark_untracked_lost(struct expression *expr, int param, const char *key, int type)
  89 {
  90         char *name;
  91         struct symbol *sym;
  92
  93         while (expr->type == EXPR_ASSIGNMENT)
  94                 expr = strip_expr(expr->right);
  95         if (expr->type != EXPR_CALL)
  96                 return;
  97
  98         name = return_state_to_var_sym(expr, param, key, &sym);
  99         if (!name || !sym)
 100                 goto free;
 101
 102         if (type == LOST_PARAM)
 103                 call_lost_callbacks(expr, param);
 104         call_untracked_callbacks(expr, param);
 105         set_state(my_id, name, sym, &untracked);
 106 free:
 107         free_string(name);
 108
 109 }
 110
 111 void mark_untracked(struct expression *expr, int param, const char *key, const char *value)
 112 {
 113         mark_untracked_lost(expr, param, key, UNTRACKED_PARAM);
 114 }
 115
 116 void mark_lost(struct expression *expr, int param, const char *key, const char *value)
 117 {
 118         mark_untracked_lost(expr, param, key, LOST_PARAM);
 119 }
 120
 121 static int lost_in_va_args(struct expression *expr)
 122 {
 123         struct symbol *fn;
 124         char *name;
 125         int is_lost;
 126
 127         fn = get_type(expr->fn);
 128         if (!fn || !fn->variadic)
 129                 return 0;
 130
 131         is_lost = 1;
 132         name = expr_to_var(expr->fn);
 133         if (name && strstr(name, "print"))
 134                 is_lost = 0;
 135         free_string(name);
 136
 137         return is_lost;
 138 }
 139
 140 static void match_after_call(struct expression *expr)
 141 {
 142         struct expression *arg;
 143         struct symbol *type;
 144         int i;
 145
 146         if (lost_in_va_args(expr))
 147                 tracked = 0;
 148
 149         if (tracked) {
 150                 tracked = 0;
 151                 return;
 152         }
 153
 154         i = -1;
 155         FOR_EACH_PTR(expr->args, arg) {
 156                 i++;
 157
 158                 type = get_type(arg);
 159                 if (!type || type->type != SYM_PTR)
 160                         continue;
 161
 162                 call_untracked_callbacks(expr, i);
 163                 set_state_expr(my_id, arg, &untracked);
 164         } END_FOR_EACH_PTR(arg);
 165 }
 166
 167
 168 static void mark_all_params(int return_id, char *return_ranges, int type)
 169 {
 170         struct symbol *arg;
 171         int param;
 172
 173         param = -1;
 174         FOR_EACH_PTR(cur_func_sym->ctype.base_type->arguments, arg) {
 175                 param++;
 176
 177                 if (!arg->ident)
 178                         continue;
 179                 sql_insert_return_states(return_id, return_ranges,
 180                                          type, param, "$", "");
 181         } END_FOR_EACH_PTR(arg);
 182 }
 183
 184
 185 void mark_all_params_untracked(int return_id, char *return_ranges, struct expression *expr)
 186 {
 187         mark_all_params(return_id, return_ranges, UNTRACKED_PARAM);
 188 }
 189
 190 void mark_all_params_lost(int return_id, char *return_ranges, struct expression *expr)
 191 {
 192         mark_all_params(return_id, return_ranges, LOST_PARAM);
 193 }
 194
 195 static void print_untracked_params(int return_id, char *return_ranges, struct expression *expr)
 196 {
 197         struct sm_state *sm;
 198         struct symbol *arg;
 199         int param;
 200         int type;
 201
 202         param = -1;
 203         FOR_EACH_PTR(cur_func_sym->ctype.base_type->arguments, arg) {
 204                 param++;
 205
 206                 if (!arg->ident)
 207                         continue;
 208
 209                 if (__bail_on_rest_of_function) {
 210                         /* hairy functions are lost */
 211                         type = LOST_PARAM;
 212                 } else if ((sm = get_sm_state(my_id, arg->ident->name, arg))) {
 213                         if (slist_has_state(sm->possible, &lost))
 214                                 type = LOST_PARAM;
 215                         else
 216                                 type = UNTRACKED_PARAM;
 217                 } else {
 218                         continue;
 219                 }
 220
 221                 sql_insert_return_states(return_id, return_ranges,
 222                                          type, param, "$", "");
 223         } END_FOR_EACH_PTR(arg);
 224 }
 225
 226 static void match_param_assign(struct expression *expr)
 227 {
 228         struct expression *right;
 229         struct symbol *type;
 230         int param;
 231
 232         if (__in_fake_assign)
 233                 return;
 234
 235         right = strip_expr(expr->right);
 236         type = get_type(right);
 237         if (!type || type->type != SYM_PTR)
 238                 return;
 239
 240         param = get_param_num(right);
 241         if (param < 0)
 242                 return;
 243
 244         set_state_expr(my_id, right, &untracked);
 245 }
 246
 247
 248 static void match_param_assign_in_asm(struct statement *stmt)
 249 {
 250
 251         struct expression *expr;
 252         struct symbol *type;
 253         int state = 0;
 254         int param;
 255
 256         FOR_EACH_PTR(stmt->asm_inputs, expr) {
 257                 switch (state) {
 258                 case 0: /* identifier */
 259                 case 1: /* constraint */
 260                         state++;
 261                         continue;
 262                 case 2: /* expression */
 263                         state = 0;
 264
 265                         expr = strip_expr(expr);
 266                         type = get_type(expr);
 267                         if (!type || type->type != SYM_PTR)
 268                                 continue;
 269                         param = get_param_num(expr);
 270                         if (param < 0)
 271                                 continue;
 272                         set_state_expr(my_id, expr, &untracked);
 273                         continue;
 274                 }
 275         } END_FOR_EACH_PTR(expr);
 276 }
 277
 278 static void match_inline_start(struct expression *expr)
 279 {
 280         push_int(&tracked_stack, tracked);
 281 }
 282
 283 static void match_inline_end(struct expression *expr)
 284 {
 285         tracked = pop_int(&tracked_stack);
 286 }
 287
 288 void register_untracked_param(int id)
 289 {
 290         my_id = id;
 291
 292         select_return_states_hook(INTERNAL, &assume_tracked);
 293         select_return_states_hook(UNTRACKED_PARAM, &mark_untracked);
 294         select_return_states_hook(LOST_PARAM, &mark_lost);
 295         add_hook(&match_after_call, FUNCTION_CALL_HOOK_AFTER_DB);
 296
 297         add_split_return_callback(&print_untracked_params);
 298
 299         add_hook(&match_param_assign, ASSIGNMENT_HOOK);
 300         add_hook(&match_param_assign_in_asm, ASM_HOOK);
 301
 302         add_hook(&match_inline_start, INLINE_FN_START);
 303         add_hook(&match_inline_end, INLINE_FN_END);
 304 }