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/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include <AK/Bitmap.h>
#include <AK/NonnullRefPtr.h>
#include <AK/RefPtr.h>
#include <AK/Vector.h>
#include <Kernel/Assertions.h>
#include <Kernel/Random.h>
#include <Kernel/VM/PhysicalPage.h>
#include <Kernel/VM/PhysicalRegion.h>
namespace Kernel {
NonnullRefPtr<PhysicalRegion> PhysicalRegion::create(PhysicalAddress lower, PhysicalAddress upper)
{
return adopt(*new PhysicalRegion(lower, upper));
}
PhysicalRegion::PhysicalRegion(PhysicalAddress lower, PhysicalAddress upper)
: m_lower(lower)
, m_upper(upper)
, m_bitmap(Bitmap::create())
{
}
void PhysicalRegion::expand(PhysicalAddress lower, PhysicalAddress upper)
{
ASSERT(!m_pages);
m_lower = lower;
m_upper = upper;
}
unsigned PhysicalRegion::finalize_capacity()
{
ASSERT(!m_pages);
m_pages = (m_upper.get() - m_lower.get()) / PAGE_SIZE;
m_bitmap.grow(m_pages, false);
return size();
}
NonnullRefPtrVector<PhysicalPage> PhysicalRegion::take_contiguous_free_pages(size_t count, bool supervisor)
{
ASSERT(m_pages);
ASSERT(m_used != m_pages);
NonnullRefPtrVector<PhysicalPage> physical_pages;
physical_pages.ensure_capacity(count);
auto first_contiguous_page = find_contiguous_free_pages(count);
for (size_t index = 0; index < count; index++)
physical_pages.append(PhysicalPage::create(m_lower.offset(PAGE_SIZE * (index + first_contiguous_page)), supervisor));
return physical_pages;
}
unsigned PhysicalRegion::find_contiguous_free_pages(size_t count)
{
ASSERT(count != 0);
// search from the last page we allocated
auto range = find_and_allocate_contiguous_range(count);
ASSERT(range.has_value());
return range.value();
}
Optional<unsigned> PhysicalRegion::find_one_free_page()
{
if (m_used == m_pages) {
// We know we don't have any free pages, no need to check the bitmap
// Check if we can draw one from the return queue
if (m_recently_returned.size() > 0) {
u8 index = get_fast_random<u8>() % m_recently_returned.size();
ptrdiff_t local_offset = m_recently_returned[index].get() - m_lower.get();
m_recently_returned.remove(index);
ASSERT(local_offset >= 0);
ASSERT((FlatPtr)local_offset < (FlatPtr)(m_pages * PAGE_SIZE));
return local_offset / PAGE_SIZE;
}
return {};
}
auto free_index = m_bitmap.find_one_anywhere_unset(m_free_hint);
ASSERT(free_index.has_value());
auto page_index = free_index.value();
m_bitmap.set(page_index, true);
m_used++;
m_free_hint = free_index.value() + 1; // Just a guess
return page_index;
}
Optional<unsigned> PhysicalRegion::find_and_allocate_contiguous_range(size_t count)
{
ASSERT(count != 0);
size_t found_pages_count = 0;
auto first_index = m_bitmap.find_longest_range_of_unset_bits(count, found_pages_count);
if (!first_index.has_value())
return {};
auto page = first_index.value();
if (count == found_pages_count) {
m_bitmap.set_range<true>(page, count);
m_used += count;
m_free_hint = first_index.value() + count + 1; // Just a guess
return page;
}
return {};
}
RefPtr<PhysicalPage> PhysicalRegion::take_free_page(bool supervisor)
{
ASSERT(m_pages);
auto free_index = find_one_free_page();
if (!free_index.has_value())
return nullptr;
return PhysicalPage::create(m_lower.offset(free_index.value() * PAGE_SIZE), supervisor);
}
void PhysicalRegion::free_page_at(PhysicalAddress addr)
{
ASSERT(m_pages);
if (m_used == 0) {
ASSERT_NOT_REACHED();
}
ptrdiff_t local_offset = addr.get() - m_lower.get();
ASSERT(local_offset >= 0);
ASSERT((FlatPtr)local_offset < (FlatPtr)(m_pages * PAGE_SIZE));
auto page = (FlatPtr)local_offset / PAGE_SIZE;
m_bitmap.set(page, false);
m_free_hint = page; // We know we can find one here for sure
m_used--;
}
void PhysicalRegion::return_page(const PhysicalPage& page)
{
auto returned_count = m_recently_returned.size();
if (returned_count >= m_recently_returned.capacity()) {
// Return queue is full, pick a random entry and free that page
// and replace the entry with this page
auto& entry = m_recently_returned[get_fast_random<u8>()];
free_page_at(entry);
entry = page.paddr();
} else {
// Still filling the return queue, just append it
m_recently_returned.append(page.paddr());
}
}
}
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