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https://github.com/SerenityOS/serenity
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16244c490a
We used to allocate major numbers quite randomly, with no common place to look them up if needed. This commit is changing that by placing all major number allocations under a new C++ namespace, in the API/MajorNumberAllocation.h file. We also add the foundations of what is needed before we can publish this information (allocated numbers for block and char devices) to userspace.
68 lines
2.7 KiB
C++
68 lines
2.7 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 <Kernel/API/MajorNumberAllocation.h>
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#include <Kernel/Devices/DeviceManagement.h>
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#include <Kernel/Devices/Generic/MemoryDevice.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 NonnullLockRefPtr<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(MajorAllocation::CharacterDeviceFamily::Generic, 1)
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{
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}
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UNMAP_AFTER_INIT MemoryDevice::~MemoryDevice() = default;
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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_if(MEMORY_DEVICE_DEBUG, "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 = TRY(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<NonnullLockRefPtr<Memory::VMObject>> MemoryDevice::vmobject_for_mmap(Process&, Memory::VirtualRange const& range, u64& offset, bool)
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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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if (!MM.is_allowed_to_read_physical_memory_for_userspace(viewed_address, range.size())) {
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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());
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return EINVAL;
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}
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offset = 0;
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return TRY(Memory::AnonymousVMObject::try_create_for_physical_range(viewed_address, range.size()));
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}
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}
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