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Serenity Operating System
1/*
2 * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions are met:
7 *
8 * 1. Redistributions of source code must retain the above copyright notice, this
9 * list of conditions and the following disclaimer.
10 *
11 * 2. Redistributions in binary form must reproduce the above copyright notice,
12 * this list of conditions and the following disclaimer in the documentation
13 * and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
16 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
17 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
18 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
19 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
20 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
21 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
22 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
23 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
24 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25 */
26
27#include <AK/Bitmap.h>
28#include <AK/NonnullRefPtr.h>
29#include <AK/RefPtr.h>
30#include <Kernel/Assertions.h>
31#include <Kernel/VM/PhysicalPage.h>
32#include <Kernel/VM/PhysicalRegion.h>
33
34namespace Kernel {
35
36NonnullRefPtr<PhysicalRegion> PhysicalRegion::create(PhysicalAddress lower, PhysicalAddress upper)
37{
38 return adopt(*new PhysicalRegion(lower, upper));
39}
40
41PhysicalRegion::PhysicalRegion(PhysicalAddress lower, PhysicalAddress upper)
42 : m_lower(lower)
43 , m_upper(upper)
44 , m_bitmap(Bitmap::create())
45{
46}
47
48void PhysicalRegion::expand(PhysicalAddress lower, PhysicalAddress upper)
49{
50 ASSERT(!m_pages);
51
52 m_lower = lower;
53 m_upper = upper;
54}
55
56unsigned PhysicalRegion::finalize_capacity()
57{
58 ASSERT(!m_pages);
59
60 m_pages = (m_upper.get() - m_lower.get()) / PAGE_SIZE;
61 m_bitmap.grow(m_pages, false);
62
63 return size();
64}
65
66RefPtr<PhysicalPage> PhysicalRegion::take_free_page(bool supervisor)
67{
68 ASSERT(m_pages);
69
70 if (m_used == m_pages)
71 return nullptr;
72
73 // search from the last page we allocated
74 for (unsigned page = m_last; page < m_pages; page++) {
75 if (!m_bitmap.get(page)) {
76 m_bitmap.set(page, true);
77 m_used++;
78 m_last = page + 1;
79 return PhysicalPage::create(m_lower.offset(page * PAGE_SIZE), supervisor);
80 }
81 }
82
83 // wrap back around to the start in case we missed something
84 for (unsigned page = 0; page < m_last; page++) {
85 if (!m_bitmap.get(page)) {
86 m_bitmap.set(page, true);
87 m_used++;
88 m_last = page + 1;
89 return PhysicalPage::create(m_lower.offset(page * PAGE_SIZE), supervisor);
90 }
91 }
92
93 ASSERT_NOT_REACHED();
94
95 return nullptr;
96}
97
98void PhysicalRegion::return_page_at(PhysicalAddress addr)
99{
100 ASSERT(m_pages);
101
102 if (m_used == 0) {
103 ASSERT_NOT_REACHED();
104 }
105
106 ptrdiff_t local_offset = addr.get() - m_lower.get();
107 ASSERT(local_offset >= 0);
108 ASSERT((uintptr_t)local_offset < (uintptr_t)(m_pages * PAGE_SIZE));
109
110 auto page = (uintptr_t)local_offset / PAGE_SIZE;
111 if (page < m_last)
112 m_last = page;
113
114 m_bitmap.set(page, false);
115 m_used--;
116}
117
118}