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      1 /*
      2  * This file is part of ltrace.
      3  * Copyright (C) 2011,2012 Petr Machata, Red Hat Inc.
      4  *
      5  * This program is free software; you can redistribute it and/or
      6  * modify it under the terms of the GNU General Public License as
      7  * published by the Free Software Foundation; either version 2 of the
      8  * License, or (at your option) any later version.
      9  *
     10  * This program is distributed in the hope that it will be useful, but
     11  * WITHOUT ANY WARRANTY; without even the implied warranty of
     12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     13  * General Public License for more details.
     14  *
     15  * You should have received a copy of the GNU General Public License
     16  * along with this program; if not, write to the Free Software
     17  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
     18  * 02110-1301 USA
     19  */
     20 
     21 #include <errno.h>
     22 
     23 #include "zero.h"
     24 #include "common.h"
     25 #include "type.h"
     26 #include "value.h"
     27 #include "expr.h"
     28 
     29 static int
     30 zero_callback_max(struct value *ret_value, struct value *lhs,
     31 		  struct value_dict *arguments,
     32 		  size_t max, void *data)
     33 {
     34 	size_t i;
     35 	for (i = 0; i < max; ++i) {
     36 		struct value element;
     37 		if (value_init_element(&element, lhs, i) < 0)
     38 			return -1;
     39 
     40 		int zero = value_is_zero(&element, arguments);
     41 
     42 		value_destroy(&element);
     43 
     44 		if (zero)
     45 			break;
     46 	}
     47 
     48 	struct arg_type_info *long_type = type_get_simple(ARGTYPE_LONG);
     49 	value_init_detached(ret_value, NULL, long_type, 0);
     50 	value_set_word(ret_value, i);
     51 	return 0;
     52 }
     53 
     54 /* LHS->zero(RHS).  Looks for a length of zero-terminated array, but
     55  * looks no further than first RHS bytes.  */
     56 static int
     57 zero_callback(struct value *ret_value, struct value *lhs,
     58 	      struct value *rhs, struct value_dict *arguments, void *data)
     59 {
     60 	long l;
     61 	if (value_extract_word(rhs, &l, arguments) < 0)
     62 		return -1;
     63 	if (l < 0)
     64 		/* It might just be a positive value >2GB, but that's
     65 		 * not likely.  */
     66 		report_global_error("maximum array length seems negative");
     67 	size_t max = (size_t)l;
     68 	return zero_callback_max(ret_value, lhs, arguments, max, data);
     69 }
     70 
     71 /* LHS->zero.  Looks for a length of zero-terminated array, without
     72  * limit.  */
     73 static int
     74 zero1_callback(struct value *ret_value, struct value *lhs,
     75 	       struct value_dict *arguments, void *data)
     76 {
     77 	return zero_callback_max(ret_value, lhs, arguments, (size_t)-1, data);
     78 }
     79 
     80 struct expr_node *
     81 build_zero_w_arg(struct expr_node *expr, int own)
     82 {
     83 	struct expr_node *e_z = malloc(sizeof(*e_z));
     84 	if (e_z == NULL)
     85 		return NULL;
     86 
     87 	expr_init_cb2(e_z, &zero_callback,
     88 		      expr_self(), 0, expr, own, NULL);
     89 	return e_z;
     90 }
     91 
     92 struct expr_node *
     93 expr_node_zero(void)
     94 {
     95 	static struct expr_node *nodep = NULL;
     96 	if (nodep == NULL) {
     97 		static struct expr_node node;
     98 		expr_init_cb1(&node, &zero1_callback,
     99 			      expr_self(), 0, (void *)-1);
    100 		nodep = &node;
    101 	}
    102 	return nodep;
    103 }
    104