jcs.org
Serenity Operating System
1/*
2 * Copyright (c) 2021, Liav A. <liavalb@hotmail.co.il>
3 *
4 * SPDX-License-Identifier: BSD-2-Clause
5 */
6
7#include <Kernel/Devices/DeviceManagement.h>
8#include <Kernel/Devices/MemoryDevice.h>
9#include <Kernel/Memory/AnonymousVMObject.h>
10#include <Kernel/Memory/TypedMapping.h>
11#include <Kernel/Sections.h>
12
13namespace Kernel {
14
15UNMAP_AFTER_INIT NonnullLockRefPtr<MemoryDevice> MemoryDevice::must_create()
16{
17 auto memory_device_or_error = DeviceManagement::try_create_device<MemoryDevice>();
18 // FIXME: Find a way to propagate errors
19 VERIFY(!memory_device_or_error.is_error());
20 return memory_device_or_error.release_value();
21}
22
23UNMAP_AFTER_INIT MemoryDevice::MemoryDevice()
24 : CharacterDevice(1, 1)
25{
26}
27
28UNMAP_AFTER_INIT MemoryDevice::~MemoryDevice() = default;
29
30ErrorOr<size_t> MemoryDevice::read(OpenFileDescription&, u64 offset, UserOrKernelBuffer& buffer, size_t length)
31{
32 if (!MM.is_allowed_to_read_physical_memory_for_userspace(PhysicalAddress(offset), length)) {
33 dbgln_if(MEMORY_DEVICE_DEBUG, "MemoryDevice: Trying to read physical memory at {} for range of {} bytes failed due to violation of access", PhysicalAddress(offset), length);
34 return EINVAL;
35 }
36 auto mapping = TRY(Memory::map_typed<u8>(PhysicalAddress(offset), length));
37
38 auto bytes = ReadonlyBytes { mapping.ptr(), length };
39 TRY(buffer.write(bytes));
40 return length;
41}
42
43ErrorOr<NonnullLockRefPtr<Memory::VMObject>> MemoryDevice::vmobject_for_mmap(Process&, Memory::VirtualRange const& range, u64& offset, bool)
44{
45 auto viewed_address = PhysicalAddress(offset);
46
47 // Note: This check happens to guard against possible memory leak.
48 // For example, if we try to mmap physical memory from 0x1000 to 0x2000 and you
49 // can actually mmap only from 0x1001, then we would fail as usual.
50 // However, in such case if we mmap from 0x1002, we are technically not violating
51 // any rules, besides the fact that we mapped an entire page with two bytes which we
52 // were not supposed to see. To prevent that, if we use mmap(2) syscall, we should
53 // always consider the start page to be aligned on PAGE_SIZE, or to be more precise
54 // is to be set to the page base of that start address.
55 VERIFY(viewed_address == viewed_address.page_base());
56
57 if (!MM.is_allowed_to_read_physical_memory_for_userspace(viewed_address, range.size())) {
58 dbgln_if(MEMORY_DEVICE_DEBUG, "MemoryDevice: Trying to mmap physical memory at {} for range of {} bytes failed due to violation of access", viewed_address, range.size());
59 return EINVAL;
60 }
61
62 offset = 0;
63 return TRY(Memory::AnonymousVMObject::try_create_for_physical_range(viewed_address, range.size()));
64}
65
66}