smatch_mtags.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 static void global_variable(struct symbol *sym)
 134 {
 135         mtag_t tag;
 136
 137         if (!get_toplevel_mtag(sym, &tag))
 138                 return;
 139
 140         sql_insert_mtag_about(tag,
 141                               sym->ident->name,
 142                               (sym->ctype.modifiers & MOD_STATIC) ? get_filename() : "extern");
 143 }
 144
 145 static void db_returns_buf_size(struct expression *expr, int param, char *unused, char *math)
 146 {
 147         struct expression *call;
 148         struct range_list *rl;
 149
 150         if (expr->type != EXPR_ASSIGNMENT)
 151                 return;
 152         call = strip_expr(expr->right);
 153
 154         if (!parse_call_math_rl(call, math, &rl))
 155                 return;
 156 //      rl = cast_rl(&int_ctype, rl);
 157 //      set_state_expr(my_size_id, expr->left, alloc_estate_rl(rl));
 158 }
 159
 160 static void match_call_info(struct expression *expr)
 161 {
 162         struct smatch_state *state;
 163         struct expression *arg;
 164         int i = -1;
 165
 166         FOR_EACH_PTR(expr->args, arg) {
 167                 i++;
 168                 state = get_state_expr(my_id, arg);
 169                 if (!state || !state->data)
 170                         continue;
 171                 sql_insert_caller_info(expr, MEMORY_TAG, i, "$", state->name);
 172         } END_FOR_EACH_PTR(arg);
 173 }
 174
 175 static void save_caller_info(const char *name, struct symbol *sym, char *key, char *value)
 176 {
 177         struct smatch_state *state;
 178         char fullname[256];
 179         mtag_t tag;
 180
 181         if (strncmp(key, "$", 1) != 0)
 182                 return;
 183
 184         tag = atoll(value);
 185         snprintf(fullname, 256, "%s%s", name, key + 1);
 186         state = alloc_tag_state(tag);
 187         set_state(my_id, fullname, sym, state);
 188 }
 189
 190 int get_mtag(struct expression *expr, mtag_t *tag)
 191 {
 192         expr = strip_expr(expr);
 193         if (expr->type == EXPR_SYMBOL &&
 194             get_toplevel_mtag(expr->symbol, tag))
 195                 return 1;
 196         return 0;
 197 }
 198
 199 void register_mtags(int id)
 200 {
 201         my_id = id;
 202
 203         add_hook(&global_variable, BASE_HOOK);
 204
 205         add_function_assign_hook("kmalloc", &alloc_assign, NULL);
 206         add_function_assign_hook("kzalloc", &alloc_assign, NULL);
 207
 208         select_return_states_hook(BUF_SIZE, &db_returns_buf_size);
 209
 210         add_hook(&match_call_info, FUNCTION_CALL_HOOK);
 211         select_caller_info_hook(save_caller_info, MEMORY_TAG);
 212 }