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f7d1b8cd0c
Although we can still consider this impossible to happen now, because the mmap syscall entry code verifies that specified offset must be page aligned, it's still a good practice to VERIFY we actually take a start address as page-aligned in case of doing mmap on /dev/mem. As for read(2) on /dev/mem, we don't map anything to userspace so it's safe to read from whatever offset userspace specified as long as it does not break the original rules of reading physical memory from /dev/mem.
80 lines
3.1 KiB
C++
80 lines
3.1 KiB
C++
/*
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* Copyright (c) 2021, Liav A. <liavalb@hotmail.co.il>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <AK/Memory.h>
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#include <AK/StdLibExtras.h>
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#include <Kernel/Devices/DeviceManagement.h>
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#include <Kernel/Devices/MemoryDevice.h>
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#include <Kernel/Firmware/BIOS.h>
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#include <Kernel/Memory/AnonymousVMObject.h>
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#include <Kernel/Memory/TypedMapping.h>
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#include <Kernel/Sections.h>
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namespace Kernel {
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UNMAP_AFTER_INIT NonnullRefPtr<MemoryDevice> MemoryDevice::must_create()
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{
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auto memory_device_or_error = DeviceManagement::try_create_device<MemoryDevice>();
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// FIXME: Find a way to propagate errors
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VERIFY(!memory_device_or_error.is_error());
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return memory_device_or_error.release_value();
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}
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UNMAP_AFTER_INIT MemoryDevice::MemoryDevice()
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: CharacterDevice(1, 1)
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{
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}
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UNMAP_AFTER_INIT MemoryDevice::~MemoryDevice()
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{
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}
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ErrorOr<size_t> MemoryDevice::read(OpenFileDescription&, u64 offset, UserOrKernelBuffer& buffer, size_t length)
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{
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if (!MM.is_allowed_to_read_physical_memory_for_userspace(PhysicalAddress(offset), length)) {
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dbgln("MemoryDevice: Trying to read physical memory at {} for range of {} bytes failed due to violation of access", PhysicalAddress(offset), length);
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return EINVAL;
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}
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auto mapping = Memory::map_typed<u8>(PhysicalAddress(offset), length);
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auto bytes = ReadonlyBytes { mapping.ptr(), length };
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TRY(buffer.write(bytes));
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return length;
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}
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ErrorOr<Memory::Region*> MemoryDevice::mmap(Process& process, OpenFileDescription&, Memory::VirtualRange const& range, u64 offset, int prot, bool shared)
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{
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auto viewed_address = PhysicalAddress(offset);
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// Note: This check happens to guard against possible memory leak.
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// For example, if we try to mmap physical memory from 0x1000 to 0x2000 and you
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// can actually mmap only from 0x1001, then we would fail as usual.
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// However, in such case if we mmap from 0x1002, we are technically not violating
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// any rules, besides the fact that we mapped an entire page with two bytes which we
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// were not supposed to see. To prevent that, if we use mmap(2) syscall, we should
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// always consider the start page to be aligned on PAGE_SIZE, or to be more precise
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// is to be set to the page base of that start address.
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VERIFY(viewed_address == viewed_address.page_base());
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dbgln("MemoryDevice: Trying to mmap physical memory at {} for range of {} bytes", viewed_address, range.size());
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if (!MM.is_allowed_to_read_physical_memory_for_userspace(viewed_address, range.size())) {
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dbgln("MemoryDevice: Trying to mmap physical memory at {} for range of {} bytes failed due to violation of access", viewed_address, range.size());
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return EINVAL;
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}
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auto vmobject = TRY(Memory::AnonymousVMObject::try_create_for_physical_range(viewed_address, range.size()));
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dbgln("MemoryDevice: Mapped physical memory at {} for range of {} bytes", viewed_address, range.size());
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return process.address_space().allocate_region_with_vmobject(
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range,
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move(vmobject),
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0,
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"Mapped Physical Memory",
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prot,
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shared);
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}
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}
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