1 /*
 2  * Copyright (c) 2025, Oracle and/or its affiliates. All rights reserved.
 3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 4  *
 5  * This code is free software; you can redistribute it and/or modify it
 6  * under the terms of the GNU General Public License version 2 only, as
 7  * published by the Free Software Foundation.
 8  *
 9  * This code is distributed in the hope that it will be useful, but WITHOUT
10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
12  * version 2 for more details (a copy is included in the LICENSE file that
13  * accompanied this code).
14  *
15  * You should have received a copy of the GNU General Public License version
16  * 2 along with this work; if not, write to the Free Software Foundation,
17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18  *
19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20  * or visit www.oracle.com if you need additional information or have any
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22  */
23 
24 #include "oops/flatArrayOop.hpp"
25 #include "unittest.hpp"
26 #include "utilities/globalDefinitions.hpp"
27 
28 // INTENTIONALLY SMALL BACKING, SHOULD ONLY CONTAIN METADATA + A FEW ELEMENTS.
29 static unsigned char memory[1024];
30 
31 // Do not perform operations on the array's memory without ensuring that the
32 // backing is large enough and you will not go out of bounds.
33 static flatArrayOop fake_flat_array(int length) {
34   flatArrayOop farr = flatArrayOop(cast_to_oop(memory));
35   // We can't ensure the backing for the length, but we can still do pointer
36   // arithmetic and e.g. ensure that the resulting pointers didn't overflow.
37   farr->set_length(length);
38   return farr;
39 }
40 
41 // What FlatArrayKlass::array_layout_helper does, but w/o InlineKlass
42 static int make_lh(int payload_size_bytes, bool null_free) {
43   BasicType etype = T_FLAT_ELEMENT;
44   int esize = log2i_exact(round_up_power_of_2(payload_size_bytes));
45   int hsize = arrayOopDesc::base_offset_in_bytes(etype);
46   return Klass::array_layout_helper(Klass::_lh_array_tag_flat_value, null_free, hsize, etype, esize);
47 }
48 
49 static void ensure_no_overflow(flatArrayOop farr, int lh) {
50   void* vaa_small = farr->value_at_addr(123, lh);
51   EXPECT_TRUE(vaa_small >= farr);
52   void* vaa_large = farr->value_at_addr(321999888, lh);
53   EXPECT_TRUE(vaa_large >= farr);
54 }
55 
56 TEST_VM(flatArrayOopDesc, value_at_addr_intbox_nullable) {
57   flatArrayOop farr = fake_flat_array(500000000);
58   ensure_no_overflow(farr, make_lh(8, false));
59 }
60 
61 
62 TEST_VM(flatArrayOopDesc, value_at_addr_intbox_null_free) {
63   flatArrayOop farr = fake_flat_array(500000000);
64   ensure_no_overflow(farr, make_lh(4, true));
65 }