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)
  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         snprintf(buf, sizeof(buf), "%s%s", sm->name, name + len);
  82         *new_sym = sm->sym;
  83         return alloc_string(buf);
  84 }
  85
  86 static char *map_assignment_long_to_short(struct sm_state *sm, const char *name, struct symbol *sym, struct symbol **new_sym)
  87 {
  88         struct symbol *orig_sym;
  89         int len;
  90         char buf[256];
  91
  92         if (!sm->state->data)
  93                 return NULL;
  94
  95         orig_sym = expr_to_sym(sm->state->data);
  96         if (!orig_sym)
  97                 return NULL;
  98         if (sym != orig_sym)
  99                 return NULL;
 100
 101         len = strlen(sm->state->name);
 102         if (strncmp(name, sm->state->name, len) != 0)
 103                 return NULL;
 104
 105         if (name[len] == '.')
 106                 return NULL;
 107         snprintf(buf, sizeof(buf), "%s%s", sm->name, name + len);
 108         *new_sym = sm->sym;
 109         return alloc_string(buf);
 110 }
 111
 112 /*
 113  * Normally, we expect people to consistently refer to variables by the shortest
 114  * name.  So they use "b->a" instead of "foo->bar.a" when both point to the
 115  * same memory location.  However, when we're dealing across function boundaries
 116  * then sometimes we pass frob(foo) which sets foo->bar.a.  In that case, we
 117  * translate it to the shorter name.  Smatch extra updates the shorter name,
 118  * which in turn updates the longer name.
 119  *
 120  */
 121 char *map_long_to_short_name_sym(const char *name, struct symbol *sym, struct symbol **new_sym)
 122 {
 123         char *ret;
 124         struct sm_state *sm;
 125
 126         *new_sym = NULL;
 127
 128         FOR_EACH_SM(__get_cur_stree(), sm) {
 129                 if (sm->owner == my_id) {
 130                         ret = map_my_state_long_to_short(sm, name, sym, new_sym);
 131                         if (ret)
 132                                 return ret;
 133                         continue;
 134                 }
 135                 if (sm->owner == check_assigned_expr_id) {
 136                         ret = map_assignment_long_to_short(sm, name, sym, new_sym);
 137                         if (ret)
 138                                 return ret;
 139                         continue;
 140                 }
 141
 142         } END_FOR_EACH_SM(sm);
 143
 144         return NULL;
 145 }
 146
 147 char *map_call_to_param_name_sym(struct expression *expr, struct symbol **sym)
 148 {
 149         char *name;
 150         struct smatch_state *state;
 151
 152         *sym = NULL;
 153
 154         name = expr_to_str(expr);
 155         if (!name)
 156                 return NULL;
 157         state = get_state(my_id, name, (struct symbol *)expr);
 158         if (!state || !state->data)
 159                 return NULL;
 160         *sym = state->data;
 161         return alloc_string(state->name);
 162 }
 163
 164 static void store_mapping_helper(char *left_name, struct symbol *left_sym, struct expression *call, const char *return_string)
 165 {
 166         const char *p = return_string;
 167         const char *end;
 168         int param;
 169         struct expression *arg;
 170         char *name = NULL;
 171         struct symbol *right_sym;
 172         char buf[256];
 173
 174         while (*p && *p != '[')
 175                 p++;
 176         if (!*p)
 177                 goto free;
 178         p++;
 179         if (*p != '$')
 180                 goto free;
 181         p++;
 182         param = atoi(p);
 183         p++;
 184         if (*p != '-' || *(p + 1) != '>')
 185                 goto free;
 186         end = strchr(p, ']');
 187         if (!end)
 188                 goto free;
 189
 190         arg = get_argument_from_call_expr(call->args, param);
 191         if (!arg)
 192                 goto free;
 193         name = expr_to_var_sym(arg, &right_sym);
 194         if (!name || !right_sym)
 195                 goto free;
 196         snprintf(buf, sizeof(buf), "%s", name);
 197
 198         if (end - p + strlen(buf) >= sizeof(buf))
 199                 goto free;
 200         strncat(buf, p, end - p);
 201
 202         set_state(my_id, left_name, left_sym, alloc_my_state(buf, right_sym));
 203         //set_state(my_id, buf, right_sym, alloc_my_state(left_name, left_sym));
 204
 205         store_link(link_id, buf, right_sym, left_name, left_sym);
 206
 207 free:
 208         free_string(name);
 209 }
 210
 211 void __add_return_to_param_mapping(struct expression *expr, const char *return_string)
 212 {
 213         struct expression *call;
 214         char *left_name = NULL;
 215         struct symbol *left_sym;
 216
 217         if (expr->type == EXPR_ASSIGNMENT) {
 218                 left_name = expr_to_var_sym(expr->left, &left_sym);
 219                 if (!left_name || !left_sym)
 220                         goto free;
 221
 222                 call = strip_expr(expr->right);
 223                 if (call->type != EXPR_CALL)
 224                         goto free;
 225
 226                 store_mapping_helper(left_name, left_sym, call, return_string);
 227                 goto free;
 228         }
 229
 230         if (expr->type == EXPR_CALL &&
 231             expr_get_parent_stmt(expr) &&
 232             expr_get_parent_stmt(expr)->type == STMT_RETURN) {
 233                 call = strip_expr(expr);
 234                 left_name = expr_to_str(call);
 235                 if (!left_name)
 236                         goto free;
 237
 238                 /*
 239                  * HACK ALERT: The symbol pointer is basically used as a cookie
 240                  * and not used as a pointer so we can pass expr here without
 241                  * causing an issue.
 242                  *
 243                  */
 244                 store_mapping_helper(left_name, (struct symbol *)expr, call, return_string);
 245                 goto free;
 246
 247         }
 248
 249 free:
 250         free_string(left_name);
 251 }
 252
 253 void register_return_to_param(int id)
 254 {
 255         my_id = id;
 256         add_modification_hook(my_id, &undef);
 257 }
 258
 259 void register_return_to_param_links(int id)
 260 {
 261         link_id = id;
 262         set_up_link_functions(my_id, link_id);
 263 }
 264