ladybird/Kernel/VM/PageDirectory.cpp

/*
 * 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/Memory.h>
#include <Kernel/Process.h>
#include <Kernel/Random.h>
#include <Kernel/Thread.h>
#include <Kernel/VM/MemoryManager.h>
#include <Kernel/VM/PageDirectory.h>

namespace Kernel {

static const FlatPtr userspace_range_base = 0x00800000;
static const FlatPtr userspace_range_ceiling = 0xbe000000;
static const FlatPtr kernelspace_range_base = 0xc0800000;

static HashMap<u32, PageDirectory*>& cr3_map()
{
    ASSERT_INTERRUPTS_DISABLED();
    static HashMap<u32, PageDirectory*>* map;
    if (!map)
        map = new HashMap<u32, PageDirectory*>;
    return *map;
}

RefPtr<PageDirectory> PageDirectory::find_by_cr3(u32 cr3)
{
    InterruptDisabler disabler;
    return cr3_map().get(cr3).value_or({});
}

extern "C" PageDirectoryEntry* boot_pdpt[4];
extern "C" PageDirectoryEntry boot_pd0[1024];
extern "C" PageDirectoryEntry boot_pd3[1024];

PageDirectory::PageDirectory()
{
    m_range_allocator.initialize_with_range(VirtualAddress(0xc0800000), 0x3f000000);
    m_identity_range_allocator.initialize_with_range(VirtualAddress(FlatPtr(0x00000000)), 0x00200000);

    // Adopt the page tables already set up by boot.S
    PhysicalAddress boot_pdpt_paddr(virtual_to_low_physical((FlatPtr)boot_pdpt));
    PhysicalAddress boot_pd0_paddr(virtual_to_low_physical((FlatPtr)boot_pd0));
    PhysicalAddress boot_pd3_paddr(virtual_to_low_physical((FlatPtr)boot_pd3));
    klog() << "MM: boot_pdpt @ " << boot_pdpt_paddr;
    klog() << "MM: boot_pd0 @ " << boot_pd0_paddr;
    klog() << "MM: boot_pd3 @ " << boot_pd3_paddr;
    m_directory_table = PhysicalPage::create(boot_pdpt_paddr, true, false);
    m_directory_pages[0] = PhysicalPage::create(boot_pd0_paddr, true, false);
    m_directory_pages[3] = PhysicalPage::create(boot_pd3_paddr, true, false);
}

PageDirectory::PageDirectory(Process& process, const RangeAllocator* parent_range_allocator)
    : m_process(&process)
{
    if (parent_range_allocator) {
        m_range_allocator.initialize_from_parent(*parent_range_allocator);
    } else {
        size_t random_offset = (get_good_random<u32>() % 32 * MB) & PAGE_MASK;
        u32 base = userspace_range_base + random_offset;
        m_range_allocator.initialize_with_range(VirtualAddress(base), userspace_range_ceiling - base);
    }

    // Set up a userspace page directory
    m_directory_table = MM.allocate_user_physical_page();
    m_directory_pages[0] = MM.allocate_user_physical_page();
    m_directory_pages[1] = MM.allocate_user_physical_page();
    m_directory_pages[2] = MM.allocate_user_physical_page();
    // Share the top 1 GB of kernel-only mappings (>=3GB or >=0xc0000000)
    m_directory_pages[3] = MM.kernel_page_directory().m_directory_pages[3];

    {
        InterruptDisabler disabler;
        auto& table = *(PageDirectoryPointerTable*)MM.quickmap_page(*m_directory_table);
        table.raw[0] = (u64)m_directory_pages[0]->paddr().as_ptr() | 1;
        table.raw[1] = (u64)m_directory_pages[1]->paddr().as_ptr() | 1;
        table.raw[2] = (u64)m_directory_pages[2]->paddr().as_ptr() | 1;
        table.raw[3] = (u64)m_directory_pages[3]->paddr().as_ptr() | 1;
        MM.unquickmap_page();
    }

    // Clone bottom 2 MB of mappings from kernel_page_directory
    PageDirectoryEntry buffer;
    auto* kernel_pd = MM.quickmap_pd(MM.kernel_page_directory(), 0);
    memcpy(&buffer, kernel_pd, sizeof(PageDirectoryEntry));
    auto* new_pd = MM.quickmap_pd(*this, 0);
    memcpy(new_pd, &buffer, sizeof(PageDirectoryEntry));

    InterruptDisabler disabler;
    cr3_map().set(cr3(), this);
}

PageDirectory::~PageDirectory()
{
#ifdef MM_DEBUG
    dbg() << "MM: ~PageDirectory K" << this;
#endif
    InterruptDisabler disabler;
    cr3_map().remove(cr3());
}

}