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 expression *orig_expr;
  91         struct symbol *orig_sym;
  92         int len;
  93         char buf[256];
  94
  95         orig_expr = sm->state->data;
  96         if (!orig_expr)
  97                 return NULL;
  98
  99         /*
 100          * Say we have an assignment like:
 101          *     foo->bar->my_ptr = my_ptr;
 102          * We still expect the function to carry on using "my_ptr" as the
 103          * shorter name.  That's not a long to short mapping.
 104          *
 105          */
 106         if (orig_expr->type == EXPR_SYMBOL)
 107                 return NULL;
 108
 109         orig_sym = expr_to_sym(orig_expr);
 110         if (!orig_sym)
 111                 return NULL;
 112         if (sym != orig_sym)
 113                 return NULL;
 114
 115         len = strlen(sm->state->name);
 116         if (strncmp(name, sm->state->name, len) != 0)
 117                 return NULL;
 118
 119         if (name[len] == '.')
 120                 return NULL;
 121         if (!stack && name[len] != '-')
 122                 return NULL;
 123         snprintf(buf, sizeof(buf), "%s%s", sm->name, name + len);
 124         *new_sym = sm->sym;
 125         return alloc_string(buf);
 126 }
 127
 128 /*
 129  * Normally, we expect people to consistently refer to variables by the shortest
 130  * name.  So they use "b->a" instead of "foo->bar.a" when both point to the
 131  * same memory location.  However, when we're dealing across function boundaries
 132  * then sometimes we pass frob(foo) which sets foo->bar.a.  In that case, we
 133  * translate it to the shorter name.  Smatch extra updates the shorter name,
 134  * which in turn updates the longer name.
 135  *
 136  */
 137 static char *map_long_to_short_name_sym_helper(const char *name, struct symbol *sym, struct symbol **new_sym, bool stack)
 138 {
 139         char *ret;
 140         struct sm_state *sm;
 141
 142         *new_sym = NULL;
 143
 144         FOR_EACH_SM(__get_cur_stree(), sm) {
 145                 if (sm->owner == my_id) {
 146                         ret = map_my_state_long_to_short(sm, name, sym, new_sym, stack);
 147                         if (ret)
 148                                 return ret;
 149                         continue;
 150                 }
 151                 if (sm->owner == check_assigned_expr_id) {
 152                         ret = map_assignment_long_to_short(sm, name, sym, new_sym, stack);
 153                         if (ret)
 154                                 return ret;
 155                         continue;
 156                 }
 157         } END_FOR_EACH_SM(sm);
 158
 159         return NULL;
 160 }
 161
 162 char *map_long_to_short_name_sym(const char *name, struct symbol *sym, struct symbol **new_sym)
 163 {
 164         return map_long_to_short_name_sym_helper(name, sym, new_sym, 1);
 165 }
 166
 167 char *map_long_to_short_name_sym_nostack(const char *name, struct symbol *sym, struct symbol **new_sym)
 168 {
 169         return map_long_to_short_name_sym_helper(name, sym, new_sym, 0);
 170 }
 171
 172 char *map_call_to_param_name_sym(struct expression *expr, struct symbol **sym)
 173 {
 174         char *name;
 175         struct symbol *start_sym;
 176         struct smatch_state *state;
 177
 178         *sym = NULL;
 179
 180         name = expr_to_str_sym(expr, &start_sym);
 181         if (!name)
 182                 return NULL;
 183         if (expr->type == EXPR_CALL)
 184                 start_sym = expr_to_sym(expr->fn);
 185
 186         state = get_state(my_id, name, start_sym);
 187         free_string(name);
 188         if (!state || !state->data)
 189                 return NULL;
 190
 191         *sym = state->data;
 192         return alloc_string(state->name);
 193 }
 194
 195 static void store_mapping_helper(char *left_name, struct symbol *left_sym, struct expression *call, const char *return_string)
 196 {
 197         const char *p = return_string;
 198         char *close;
 199         int param;
 200         struct expression *arg, *new;
 201         char *right_name;
 202         struct symbol *right_sym;
 203         char buf[256];
 204
 205         while (*p && *p != '[')
 206                 p++;
 207         if (!*p)
 208                 return;
 209         p++;
 210         if (*p != '$')
 211                 return;
 212
 213         snprintf(buf, sizeof(buf), "%s", p);
 214         close = strchr(buf, ']');
 215         if (!close)
 216                 return;
 217         *close = '\0';
 218
 219         param = atoi(buf + 1);
 220         arg = get_argument_from_call_expr(call->args, param);
 221         if (!arg)
 222                 return;
 223
 224         new = gen_expression_from_key(arg, buf);
 225         if (!new)
 226                 return;
 227
 228         right_name = expr_to_var_sym(new, &right_sym);
 229         if (!right_name || !right_sym)
 230                 goto free;
 231
 232         set_state(my_id, left_name, left_sym, alloc_my_state(right_name, right_sym));
 233         store_link(link_id, right_name, right_sym, left_name, left_sym);
 234
 235 free:
 236         free_string(right_name);
 237 }
 238
 239 void __add_return_to_param_mapping(struct expression *expr, const char *return_string)
 240 {
 241         struct expression *call;
 242         char *left_name = NULL;
 243         struct symbol *left_sym;
 244
 245         if (expr->type == EXPR_ASSIGNMENT) {
 246                 left_name = expr_to_var_sym(expr->left, &left_sym);
 247                 if (!left_name || !left_sym)
 248                         goto free;
 249
 250                 call = strip_expr(expr->right);
 251                 if (call->type != EXPR_CALL)
 252                         goto free;
 253
 254                 store_mapping_helper(left_name, left_sym, call, return_string);
 255                 goto free;
 256         }
 257
 258         if (expr->type == EXPR_CALL &&
 259             expr_get_parent_stmt(expr) &&
 260             expr_get_parent_stmt(expr)->type == STMT_RETURN) {
 261                 call = strip_expr(expr);
 262                 left_sym = expr_to_sym(call->fn);
 263                 if (!left_sym)
 264                         return;
 265                 left_name = expr_to_str(call);
 266                 if (!left_name)
 267                         return;
 268
 269                 store_mapping_helper(left_name, left_sym, call, return_string);
 270                 goto free;
 271
 272         }
 273
 274 free:
 275         free_string(left_name);
 276 }
 277
 278 void register_return_to_param(int id)
 279 {
 280         my_id = id;
 281         add_modification_hook(my_id, &undef);
 282 }
 283
 284 void register_return_to_param_links(int id)
 285 {
 286         link_id = id;
 287         set_up_link_functions(my_id, link_id);
 288 }
 289