smatch_return_to_param.c

   1 /*
   2  * Copyright (C) 2017 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 is for smatch_extra.c to use.  It sort of like check_assigned_expr.c but
  20  * more limited.  Say a function returns "64min-s64max[$0->data]" and the caller
  21  * does "struct whatever *p = get_data(dev);" then we want to record that p is
  22  * now the same as "dev->data".  Then if we update "p->foo" it means we can
  23  * update "dev->data->foo" as well.
  24  *
  25  */
  26
  27 #include "smatch.h"
  28 #include "smatch_slist.h"
  29 #include "smatch_extra.h"
  30
  31 extern int check_assigned_expr_id;
  32 static int my_id;
  33 static int link_id;
  34
  35 static struct smatch_state *alloc_my_state(const char *name, struct symbol *sym)
  36 {
  37         struct smatch_state *state;
  38
  39         state = __alloc_smatch_state(0);
  40         state->name = alloc_sname(name);
  41         state->data = sym;
  42         return state;
  43 }
  44
  45 static void undef(struct sm_state *sm, struct expression *mod_expr)
  46 {
  47         set_state(my_id, sm->name, sm->sym, &undefined);
  48 }
  49
  50 char *map_call_to_other_name_sym(const char *name, struct symbol *sym, struct symbol **new_sym)
  51 {
  52         struct smatch_state *state;
  53         int skip;
  54         char buf[256];
  55
  56         /* skip 'foo->'.  This was checked in the caller. */
  57         skip = strlen(sym->ident->name) + 2;
  58
  59         state = get_state(my_id, sym->ident->name, sym);
  60         if (!state || !state->data)
  61                 return NULL;
  62
  63         snprintf(buf, sizeof(buf), "%s->%s", state->name, name + skip);
  64         *new_sym = state->data;
  65         return alloc_string(buf);
  66 }
  67
  68 static char *map_my_state_long_to_short(struct sm_state *sm, const char *name, struct symbol *sym, struct symbol **new_sym, bool stack)
  69 {
  70         int len;
  71         char buf[256];
  72
  73         if (sm->state->data != sym)
  74                 return NULL;
  75         len = strlen(sm->state->name);
  76         if (strncmp(name, sm->state->name, len) != 0)
  77                 return NULL;
  78
  79         if (name[len] == '.')
  80                 return NULL;
  81         if (!stack && name[len] != '-')
  82                 return NULL;
  83         snprintf(buf, sizeof(buf), "%s%s", sm->name, name + len);
  84         *new_sym = sm->sym;
  85         return alloc_string(buf);
  86 }
  87
  88 static char *map_assignment_long_to_short(struct sm_state *sm, const char *name, struct symbol *sym, struct symbol **new_sym, bool stack)
  89 {
  90         struct symbol *orig_sym;
  91         int len;
  92         char buf[256];
  93
  94         if (!sm->state->data)
  95                 return NULL;
  96
  97         orig_sym = expr_to_sym(sm->state->data);
  98         if (!orig_sym)
  99                 return NULL;
 100         if (sym != orig_sym)
 101                 return NULL;
 102
 103         len = strlen(sm->state->name);
 104         if (strncmp(name, sm->state->name, len) != 0)
 105                 return NULL;
 106
 107         if (name[len] == '.')
 108                 return NULL;
 109         if (!stack && name[len] != '-')
 110                 return NULL;
 111         snprintf(buf, sizeof(buf), "%s%s", sm->name, name + len);
 112         *new_sym = sm->sym;
 113         return alloc_string(buf);
 114 }
 115
 116 /*
 117  * Normally, we expect people to consistently refer to variables by the shortest
 118  * name.  So they use "b->a" instead of "foo->bar.a" when both point to the
 119  * same memory location.  However, when we're dealing across function boundaries
 120  * then sometimes we pass frob(foo) which sets foo->bar.a.  In that case, we
 121  * translate it to the shorter name.  Smatch extra updates the shorter name,
 122  * which in turn updates the longer name.
 123  *
 124  */
 125 static char *map_long_to_short_name_sym_helper(const char *name, struct symbol *sym, struct symbol **new_sym, bool stack)
 126 {
 127         char *ret;
 128         struct sm_state *sm;
 129
 130         *new_sym = NULL;
 131
 132         FOR_EACH_SM(__get_cur_stree(), sm) {
 133                 if (sm->owner == my_id) {
 134                         ret = map_my_state_long_to_short(sm, name, sym, new_sym, stack);
 135                         if (ret)
 136                                 return ret;
 137                         continue;
 138                 }
 139                 if (sm->owner == check_assigned_expr_id) {
 140                         ret = map_assignment_long_to_short(sm, name, sym, new_sym, stack);
 141                         if (ret)
 142                                 return ret;
 143                         continue;
 144                 }
 145         } END_FOR_EACH_SM(sm);
 146
 147         return NULL;
 148 }
 149
 150 char *map_long_to_short_name_sym(const char *name, struct symbol *sym, struct symbol **new_sym)
 151 {
 152         return map_long_to_short_name_sym_helper(name, sym, new_sym, 1);
 153 }
 154
 155 char *map_long_to_short_name_sym_nostack(const char *name, struct symbol *sym, struct symbol **new_sym)
 156 {
 157         return map_long_to_short_name_sym_helper(name, sym, new_sym, 0);
 158 }
 159
 160 char *map_call_to_param_name_sym(struct expression *expr, struct symbol **sym)
 161 {
 162         char *name;
 163         struct smatch_state *state;
 164
 165         *sym = NULL;
 166
 167         name = expr_to_str(expr);
 168         if (!name)
 169                 return NULL;
 170         state = get_state(my_id, name, (struct symbol *)expr);
 171         if (!state || !state->data)
 172                 return NULL;
 173         *sym = state->data;
 174         return alloc_string(state->name);
 175 }
 176
 177 static void store_mapping_helper(char *left_name, struct symbol *left_sym, struct expression *call, const char *return_string)
 178 {
 179         const char *p = return_string;
 180         const char *end;
 181         int param;
 182         struct expression *arg;
 183         char *name = NULL;
 184         struct symbol *right_sym;
 185         char buf[256];
 186
 187         while (*p && *p != '[')
 188                 p++;
 189         if (!*p)
 190                 goto free;
 191         p++;
 192         if (*p != '$')
 193                 goto free;
 194         p++;
 195         param = atoi(p);
 196         p++;
 197         if (*p != '-' || *(p + 1) != '>')
 198                 goto free;
 199         end = strchr(p, ']');
 200         if (!end)
 201                 goto free;
 202
 203         arg = get_argument_from_call_expr(call->args, param);
 204         if (!arg)
 205                 goto free;
 206         name = expr_to_var_sym(arg, &right_sym);
 207         if (!name || !right_sym)
 208                 goto free;
 209         snprintf(buf, sizeof(buf), "%s", name);
 210
 211         if (end - p + strlen(buf) >= sizeof(buf))
 212                 goto free;
 213         strncat(buf, p, end - p);
 214
 215         set_state(my_id, left_name, left_sym, alloc_my_state(buf, right_sym));
 216         //set_state(my_id, buf, right_sym, alloc_my_state(left_name, left_sym));
 217
 218         store_link(link_id, buf, right_sym, left_name, left_sym);
 219
 220 free:
 221         free_string(name);
 222 }
 223
 224 void __add_return_to_param_mapping(struct expression *expr, const char *return_string)
 225 {
 226         struct expression *call;
 227         char *left_name = NULL;
 228         struct symbol *left_sym;
 229
 230         if (expr->type == EXPR_ASSIGNMENT) {
 231                 left_name = expr_to_var_sym(expr->left, &left_sym);
 232                 if (!left_name || !left_sym)
 233                         goto free;
 234
 235                 call = strip_expr(expr->right);
 236                 if (call->type != EXPR_CALL)
 237                         goto free;
 238
 239                 store_mapping_helper(left_name, left_sym, call, return_string);
 240                 goto free;
 241         }
 242
 243         if (expr->type == EXPR_CALL &&
 244             expr_get_parent_stmt(expr) &&
 245             expr_get_parent_stmt(expr)->type == STMT_RETURN) {
 246                 call = strip_expr(expr);
 247                 left_name = expr_to_str(call);
 248                 if (!left_name)
 249                         goto free;
 250
 251                 /*
 252                  * HACK ALERT: The symbol pointer is basically used as a cookie
 253                  * and not used as a pointer so we can pass expr here without
 254                  * causing an issue.
 255                  *
 256                  */
 257                 store_mapping_helper(left_name, (struct symbol *)expr, call, return_string);
 258                 goto free;
 259
 260         }
 261
 262 free:
 263         free_string(left_name);
 264 }
 265
 266 void register_return_to_param(int id)
 267 {
 268         my_id = id;
 269         add_modification_hook(my_id, &undef);
 270 }
 271
 272 void register_return_to_param_links(int id)
 273 {
 274         link_id = id;
 275         set_up_link_functions(my_id, link_id);
 276 }
 277