smatch_mtag.c

   1 /*
   2  * Copyright (C) 2017 Oracle.  All rights reserved.
   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  * One problem that I have is that it's really hard to track how pointers are
  20  * passed around.  For example, it would be nice to know that the probe() and
  21  * remove() functions get the same pci_dev pointer.  It would be good to know
  22  * what pointers we're passing to the open() and close() functions.  But that
  23  * information gets lost in a call tree full of function pointer calls.
  24  *
  25  * I think the first step is to start naming specific pointers.  So when a
  26  * pointer is allocated, then it gets a tag.  So calls to kmalloc() generate a
  27  * tag.  But we might not use that, because there might be a better name like
  28  * framebuffer_alloc(). The framebuffer_alloc() is interesting because there is
  29  * one per driver and it's passed around to all the file operations.
  30  *
  31  * Perhaps we could make a list of functions like framebuffer_alloc() which take
  32  * a size and say that those are the interesting alloc functions.
  33  *
  34  * Another place where we would maybe name the pointer is when they are passed
  35  * to the probe().  Because that's an important pointer, since there is one
  36  * per driver (sort of).
  37  *
  38  * My vision is that you could take a pointer and trace it back to a global.  So
  39  * I'm going to track that pointer_tag - 28 bytes takes you to another pointer
  40  * tag.  You could follow that one back and so on.  Also when we pass a pointer
  41  * to a function that would be recorded as sort of a link or path or something.
  42  *
  43  */
  44
  45 #include "smatch.h"
  46 #include "smatch_slist.h"
  47 #include "smatch_extra.h"
  48
  49 #include <openssl/md5.h>
  50
  51 static int my_id;
  52
  53 static struct smatch_state *alloc_tag_state(mtag_t tag)
  54 {
  55         struct smatch_state *state;
  56         char buf[64];
  57
  58         state = __alloc_smatch_state(0);
  59         snprintf(buf, sizeof(buf), "%lld", tag);
  60         state->name = alloc_sname(buf);
  61         state->data = malloc(sizeof(mtag_t));
  62         *(mtag_t *)state->data = tag;
  63
  64         return state;
  65 }
  66
  67 static mtag_t str_to_tag(const char *str)
  68 {
  69         unsigned char c[MD5_DIGEST_LENGTH];
  70         unsigned long long *tag = (unsigned long long *)&c;
  71         MD5_CTX mdContext;
  72         int len;
  73
  74         len = strlen(str);
  75         MD5_Init(&mdContext);
  76         MD5_Update(&mdContext, str, len);
  77         MD5_Final(c, &mdContext);
  78
  79         *tag &= ~(1ULL << 63);
  80
  81         return *tag;
  82 }
  83
  84 static void alloc_assign(const char *fn, struct expression *expr, void *unused)
  85 {
  86         struct expression *left, *right;
  87         char *left_name, *right_name;
  88         struct symbol *left_sym;
  89         char buf[256];
  90         mtag_t tag;
  91
  92         if (expr->type != EXPR_ASSIGNMENT || expr->op != '=')
  93                 return;
  94         left = strip_expr(expr->left);
  95         right = strip_expr(expr->right);
  96         if (right->type != EXPR_CALL || right->fn->type != EXPR_SYMBOL)
  97                 return;
  98
  99         left_name = expr_to_str_sym(left, &left_sym);
 100         right_name = expr_to_str(right);
 101
 102         snprintf(buf, sizeof(buf), "%s %s %s %s", get_filename(), get_function(),
 103                  left_name, right_name);
 104         tag = str_to_tag(buf);
 105
 106         sql_insert_mtag_about(tag, left_name, right_name);
 107
 108         if (left_name && left_sym)
 109                 set_state(my_id, left_name, left_sym, alloc_tag_state(tag));
 110
 111         free_string(left_name);
 112         free_string(right_name);
 113 }
 114
 115 int get_toplevel_mtag(struct symbol *sym, mtag_t *tag)
 116 {
 117         char buf[256];
 118
 119         if (!sym)
 120                 return 0;
 121
 122         if (!sym->ident ||
 123             !(sym->ctype.modifiers & MOD_TOPLEVEL))
 124                 return 0;
 125
 126         snprintf(buf, sizeof(buf), "%s %s",
 127                  (sym->ctype.modifiers & MOD_STATIC) ? get_filename() : "extern",
 128                  sym->ident->name);
 129         *tag = str_to_tag(buf);
 130         return 1;
 131 }
 132
 133 int get_deref_mtag(struct expression *expr, mtag_t *tag)
 134 {
 135         mtag_t container_tag, member_tag;
 136         int offset;
 137
 138         /*
 139          * I'm not totally sure what I'm doing...
 140          *
 141          * This is supposed to get something like "global_var->ptr", but I don't
 142          * feel like it's complete at all.
 143          *
 144          */
 145
 146         if (!get_mtag(expr->unop, &container_tag))
 147                 return 0;
 148
 149         offset = get_member_offset_from_deref(expr);
 150         if (offset < 0)
 151                 return 0;
 152
 153         if (!mtag_map_select_tag(container_tag, -offset, &member_tag))
 154                 return 0;
 155
 156         *tag = member_tag;
 157         return 1;
 158 }
 159
 160 static void global_variable(struct symbol *sym)
 161 {
 162         mtag_t tag;
 163
 164         if (!get_toplevel_mtag(sym, &tag))
 165                 return;
 166
 167         sql_insert_mtag_about(tag,
 168                               sym->ident->name,
 169                               (sym->ctype.modifiers & MOD_STATIC) ? get_filename() : "extern");
 170 }
 171
 172 static void db_returns_buf_size(struct expression *expr, int param, char *unused, char *math)
 173 {
 174         struct expression *call;
 175         struct range_list *rl;
 176
 177         if (expr->type != EXPR_ASSIGNMENT)
 178                 return;
 179         call = strip_expr(expr->right);
 180
 181         if (!parse_call_math_rl(call, math, &rl))
 182                 return;
 183 //      rl = cast_rl(&int_ctype, rl);
 184 //      set_state_expr(my_size_id, expr->left, alloc_estate_rl(rl));
 185 }
 186
 187 static void match_call_info(struct expression *expr)
 188 {
 189         struct smatch_state *state;
 190         struct expression *arg;
 191         int i = -1;
 192
 193         FOR_EACH_PTR(expr->args, arg) {
 194                 i++;
 195                 state = get_state_expr(my_id, arg);
 196                 if (!state || !state->data)
 197                         continue;
 198                 sql_insert_caller_info(expr, MEMORY_TAG, i, "$", state->name);
 199         } END_FOR_EACH_PTR(arg);
 200 }
 201
 202 static void save_caller_info(const char *name, struct symbol *sym, char *key, char *value)
 203 {
 204         struct smatch_state *state;
 205         char fullname[256];
 206         mtag_t tag;
 207
 208         if (strncmp(key, "$", 1) != 0)
 209                 return;
 210
 211         tag = atoll(value);
 212         snprintf(fullname, 256, "%s%s", name, key + 1);
 213         state = alloc_tag_state(tag);
 214         set_state(my_id, fullname, sym, state);
 215 }
 216
 217 static int get_array_mtag(struct expression *expr, mtag_t *tag)
 218 {
 219         struct expression *base, *offset;
 220         sval_t sval;
 221         mtag_t base_tag;
 222         char buf[256];
 223
 224         if (!is_array(expr))
 225                 return 0;
 226
 227         base = get_array_base(expr);
 228         if (!base)
 229                 return 0;
 230         offset = get_array_offset(expr);
 231         if (!offset)
 232                 return 0;
 233
 234         if (!get_implied_value(offset, &sval))
 235                 return 0;
 236
 237         if (!get_mtag(base, &base_tag))
 238                 return 0;
 239
 240         snprintf(buf, sizeof(buf), "%lld + %lld", base_tag, sval.value);
 241         *tag = str_to_tag(buf);
 242
 243         return 1;
 244 }
 245
 246 static int get_mtag_cnt;
 247 int get_mtag(struct expression *expr, mtag_t *tag)
 248 {
 249         struct smatch_state *state;
 250         int ret = 0;
 251
 252         expr = strip_expr(expr);
 253         if (!expr)
 254                 return 0;
 255
 256         if (get_mtag_cnt > 0)
 257                 return 0;
 258
 259         get_mtag_cnt++;
 260
 261         /* FIXME:  This doesn't feel like the right thing at all */
 262         if (expr->type == EXPR_PREOP) {
 263                 if (expr->op == '&')
 264                         expr = strip_expr(expr->unop);
 265                 if (expr->op == '*')
 266                         expr = strip_expr(expr->unop);
 267         }
 268
 269         switch (expr->type) {
 270         case EXPR_SYMBOL:
 271                 if (get_toplevel_mtag(expr->symbol, tag)) {
 272                         ret = 1;
 273                         goto dec_cnt;
 274                 }
 275                 break;
 276         case EXPR_DEREF:
 277                 if (get_deref_mtag(expr, tag)) {
 278                         ret = 1;
 279                         goto dec_cnt;
 280                 }
 281                 break;
 282         case EXPR_BINOP:
 283                 ret = get_array_mtag(expr, tag);
 284                 goto dec_cnt;
 285         }
 286
 287         state = get_state_expr(my_id, expr);
 288         if (!state)
 289                 goto dec_cnt;
 290         if (state->data) {
 291                 *tag = *(mtag_t *)state->data;
 292                 ret = 1;
 293                 goto dec_cnt;
 294         }
 295
 296 dec_cnt:
 297         get_mtag_cnt--;
 298         return ret;
 299 }
 300
 301 int create_mtag_alias(mtag_t tag, struct expression *expr, mtag_t *new)
 302 {
 303         char buf[256];
 304         int lines_from_start;
 305         char *str;
 306
 307         /*
 308          * We need the alias to be unique.  It's not totally required that it
 309          * be the same from one DB build to then next, but it makes debugging
 310          * a bit simpler.
 311          *
 312          */
 313
 314         if (!cur_func_sym)
 315                 return 0;
 316
 317         lines_from_start = expr->pos.line - cur_func_sym->pos.line;
 318         str = expr_to_str(expr);
 319         snprintf(buf, sizeof(buf), "%lld %d %s", tag, lines_from_start, str);
 320         free_string(str);
 321
 322         *new = str_to_tag(buf);
 323
 324         return 1;
 325 }
 326
 327 int expr_to_mtag_name_offset(struct expression *expr, mtag_t *tag, char **name, int *offset)
 328 {
 329         static char buf[256];
 330
 331         *offset = 0;
 332         *name = 0;
 333
 334         expr = strip_expr(expr);
 335         if (!expr)
 336                 return 0;
 337
 338         if (expr->type ==  EXPR_DEREF) {
 339                 *offset = get_member_offset_from_deref(expr);
 340                 if (*offset < 0)
 341                         return 0;
 342                 snprintf(buf, sizeof(buf), "$->%s", expr->member->name);
 343                 *name = buf;
 344                 return get_mtag(expr->deref, tag);
 345         }
 346
 347         snprintf(buf, sizeof(buf), "*$");
 348         *name = buf;
 349
 350         return get_mtag(expr, tag);
 351 }
 352
 353 void register_mtag(int id)
 354 {
 355         my_id = id;
 356
 357         add_hook(&global_variable, BASE_HOOK);
 358
 359         add_function_assign_hook("kmalloc", &alloc_assign, NULL);
 360         add_function_assign_hook("kzalloc", &alloc_assign, NULL);
 361
 362         select_return_states_hook(BUF_SIZE, &db_returns_buf_size);
 363
 364         add_hook(&match_call_info, FUNCTION_CALL_HOOK);
 365         select_caller_info_hook(save_caller_info, MEMORY_TAG);
 366 }