check_ida_alloc.c

   1 /*
   2  * Copyright (C) 2022 Christophe Jaillet.
   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  * The 'max' parameter of ida_alloc_max() and ida_alloc_range() is not interpreted
  20  * as it was in the deprecated ida_simple_get().
  21  *
  22  * The 'max' value in the new functions is inclusive but it was exclusive before.
  23  * So, in older code, this parameter was often a power of 2, such as 1 << 16, so
  24  * that the maximum possible value was 0xffff.
  25  *
  26  * Now a power of 2 value is spurious.
  27  */
  28 #include <fcntl.h>
  29 #include <unistd.h>
  30 #include "parse.h"
  31 #include "smatch.h"
  32
  33 static int my_id;
  34
  35 static bool implied_power_of_two(struct expression *expr)
  36 {
  37         sval_t sval;
  38
  39         if (!get_implied_value(expr, &sval))
  40                 return false;
  41         if (!(sval.uvalue & (sval.uvalue - 1)))
  42                 return true;
  43         return false;
  44 }
  45
  46 static bool is_power_of_two(struct expression *expr)
  47 {
  48         expr = strip_expr(expr);
  49
  50         if (expr->type == EXPR_BINOP &&
  51             expr->op == SPECIAL_LEFTSHIFT &&
  52             is_power_of_two(expr->left))
  53                 return true;
  54
  55         if (implied_power_of_two(expr))
  56                 return true;
  57
  58         return false;
  59 }
  60
  61 static void match_ida_alloc(const char *fn, struct expression *expr, void *_arg_nr)
  62 {
  63         int arg_nr = PTR_INT(_arg_nr);
  64         struct expression *arg_expr;
  65
  66         arg_expr = get_argument_from_call_expr(expr->args, arg_nr);
  67         arg_expr = strip_expr(arg_expr);
  68
  69         if (is_power_of_two(arg_expr))
  70                 sm_error("Calling %s() with a 'max' argument which is a power of 2. -1 missing?",
  71                          fn);
  72 }
  73
  74 void check_ida_alloc(int id)
  75 {
  76         if (option_project != PROJ_KERNEL)
  77                 return;
  78
  79         my_id = id;
  80
  81         add_function_hook("ida_alloc_max", &match_ida_alloc, INT_PTR(1));
  82         add_function_hook("ida_alloc_range", &match_ida_alloc, INT_PTR(2));
  83 }