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         if (__in_fake_parameter_assign)
  48                 return;
  49         set_state(my_id, sm->name, sm->sym, &undefined);
  50 }
  51
  52 char *map_call_to_other_name_sym(const char *name, struct symbol *sym, struct symbol **new_sym)
  53 {
  54         struct smatch_state *state;
  55         int skip;
  56         char buf[256];
  57
  58         /* skip 'foo->'.  This was checked in the caller. */
  59         skip = strlen(sym->ident->name) + 2;
  60
  61         state = get_state(my_id, sym->ident->name, sym);
  62         if (!state || !state->data)
  63                 return NULL;
  64
  65         snprintf(buf, sizeof(buf), "%s->%s", state->name, name + skip);
  66         *new_sym = state->data;
  67         return alloc_string(buf);
  68 }
  69
  70 static char *map_my_state_long_to_short(struct sm_state *sm, const char *name, struct symbol *sym, struct symbol **new_sym, bool stack)
  71 {
  72         int len;
  73         char buf[256];
  74
  75         if (sm->state->data != sym)
  76                 return NULL;
  77         len = strlen(sm->state->name);
  78         if (strncmp(name, sm->state->name, len) != 0)
  79                 return NULL;
  80
  81         if (name[len] == '.')
  82                 return NULL;
  83         if (!stack && name[len] != '-')
  84                 return NULL;
  85         snprintf(buf, sizeof(buf), "%s%s", sm->name, name + len);
  86         *new_sym = sm->sym;
  87         return alloc_string(buf);
  88 }
  89
  90 static char *map_assignment_long_to_short(struct sm_state *sm, const char *name, struct symbol *sym, struct symbol **new_sym, bool stack)
  91 {
  92         struct expression *orig_expr;
  93         struct symbol *orig_sym;
  94         int len;
  95         char buf[256];
  96
  97         orig_expr = sm->state->data;
  98         if (!orig_expr)
  99                 return NULL;
 100
 101         /*
 102          * Say we have an assignment like:
 103          *     foo->bar->my_ptr = my_ptr;
 104          * We still expect the function to carry on using "my_ptr" as the
 105          * shorter name.  That's not a long to short mapping.
 106          *
 107          */
 108         if (orig_expr->type == EXPR_SYMBOL)
 109                 return NULL;
 110
 111         orig_sym = expr_to_sym(orig_expr);
 112         if (!orig_sym)
 113                 return NULL;
 114         if (sym != orig_sym)
 115                 return NULL;
 116
 117         len = strlen(sm->state->name);
 118         if (strncmp(name, sm->state->name, len) != 0)
 119                 return NULL;
 120
 121         if (name[len] == '.')
 122                 return NULL;
 123         if (!stack && name[len] != '-')
 124                 return NULL;
 125         snprintf(buf, sizeof(buf), "%s%s", sm->name, name + len);
 126         *new_sym = sm->sym;
 127         return alloc_string(buf);
 128 }
 129
 130 /*
 131  * Normally, we expect people to consistently refer to variables by the shortest
 132  * name.  So they use "b->a" instead of "foo->bar.a" when both point to the
 133  * same memory location.  However, when we're dealing across function boundaries
 134  * then sometimes we pass frob(foo) which sets foo->bar.a.  In that case, we
 135  * translate it to the shorter name.  Smatch extra updates the shorter name,
 136  * which in turn updates the longer name.
 137  *
 138  */
 139 static char *map_long_to_short_name_sym_helper(const char *name, struct symbol *sym, struct symbol **new_sym, bool stack)
 140 {
 141         char *ret;
 142         struct sm_state *sm;
 143
 144         *new_sym = NULL;
 145
 146         FOR_EACH_SM(__get_cur_stree(), sm) {
 147                 if (sm->owner == my_id) {
 148                         ret = map_my_state_long_to_short(sm, name, sym, new_sym, stack);
 149                         if (ret)
 150                                 return ret;
 151                         continue;
 152                 }
 153                 if (sm->owner == check_assigned_expr_id) {
 154                         ret = map_assignment_long_to_short(sm, name, sym, new_sym, stack);
 155                         if (ret)
 156                                 return ret;
 157                         continue;
 158                 }
 159         } END_FOR_EACH_SM(sm);
 160
 161         return NULL;
 162 }
 163
 164 char *map_long_to_short_name_sym(const char *name, struct symbol *sym, struct symbol **new_sym)
 165 {
 166         return map_long_to_short_name_sym_helper(name, sym, new_sym, 1);
 167 }
 168
 169 char *map_long_to_short_name_sym_nostack(const char *name, struct symbol *sym, struct symbol **new_sym)
 170 {
 171         return map_long_to_short_name_sym_helper(name, sym, new_sym, 0);
 172 }
 173
 174 char *map_call_to_param_name_sym(struct expression *expr, struct symbol **sym)
 175 {
 176         char *name;
 177         struct symbol *start_sym;
 178         struct smatch_state *state;
 179
 180         *sym = NULL;
 181
 182         name = expr_to_str_sym(expr, &start_sym);
 183         if (!name)
 184                 return NULL;
 185         if (expr->type == EXPR_CALL)
 186                 start_sym = expr_to_sym(expr->fn);
 187
 188         state = get_state(my_id, name, start_sym);
 189         free_string(name);
 190         if (!state || !state->data)
 191                 return NULL;
 192
 193         *sym = state->data;
 194         return alloc_string(state->name);
 195 }
 196
 197 static void store_mapping_helper(char *left_name, struct symbol *left_sym, struct expression *call, const char *return_string)
 198 {
 199         const char *p = return_string;
 200         char *close;
 201         int param;
 202         struct expression *arg, *new;
 203         char *right_name;
 204         struct symbol *right_sym;
 205         char buf[256];
 206
 207         while (*p && *p != '[')
 208                 p++;
 209         if (!*p)
 210                 return;
 211         p++;
 212         if (*p != '$')
 213                 return;
 214
 215         snprintf(buf, sizeof(buf), "%s", p);
 216         close = strchr(buf, ']');
 217         if (!close)
 218                 return;
 219         *close = '\0';
 220
 221         param = atoi(buf + 1);
 222         arg = get_argument_from_call_expr(call->args, param);
 223         if (!arg)
 224                 return;
 225
 226         new = gen_expression_from_key(arg, buf);
 227         if (!new)
 228                 return;
 229
 230         right_name = expr_to_var_sym(new, &right_sym);
 231         if (!right_name || !right_sym)
 232                 goto free;
 233
 234         set_state(my_id, left_name, left_sym, alloc_my_state(right_name, right_sym));
 235         store_link(link_id, right_name, right_sym, left_name, left_sym);
 236
 237 free:
 238         free_string(right_name);
 239 }
 240
 241 void __add_return_to_param_mapping(struct expression *expr, const char *return_string)
 242 {
 243         struct expression *call;
 244         char *left_name = NULL;
 245         struct symbol *left_sym;
 246
 247         if (expr->type == EXPR_ASSIGNMENT) {
 248                 left_name = expr_to_var_sym(expr->left, &left_sym);
 249                 if (!left_name || !left_sym)
 250                         goto free;
 251
 252                 call = strip_expr(expr->right);
 253                 if (call->type != EXPR_CALL)
 254                         goto free;
 255
 256                 store_mapping_helper(left_name, left_sym, call, return_string);
 257                 goto free;
 258         }
 259
 260         if (expr->type == EXPR_CALL &&
 261             expr_get_parent_stmt(expr) &&
 262             expr_get_parent_stmt(expr)->type == STMT_RETURN) {
 263                 call = strip_expr(expr);
 264                 left_sym = expr_to_sym(call->fn);
 265                 if (!left_sym)
 266                         return;
 267                 left_name = expr_to_str(call);
 268                 if (!left_name)
 269                         return;
 270
 271                 store_mapping_helper(left_name, left_sym, call, return_string);
 272                 goto free;
 273
 274         }
 275
 276 free:
 277         free_string(left_name);
 278 }
 279
 280 void register_return_to_param(int id)
 281 {
 282         my_id = id;
 283         add_modification_hook(my_id, &undef);
 284 }
 285
 286 void register_return_to_param_links(int id)
 287 {
 288         link_id = id;
 289         set_up_link_functions(my_id, link_id);
 290 }
 291