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/*
* Copyright (c) 2021, Liav A. <liavalb@hotmail.co.il>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/Memory.h>
#include <AK/StdLibExtras.h>
#include <Kernel/Devices/DeviceManagement.h>
#include <Kernel/Devices/MemoryDevice.h>
#include <Kernel/Memory/AnonymousVMObject.h>
#include <Kernel/Memory/TypedMapping.h>
#include <Kernel/Sections.h>
namespace Kernel {
UNMAP_AFTER_INIT NonnullLockRefPtr<MemoryDevice> MemoryDevice::must_create()
{
auto memory_device_or_error = DeviceManagement::try_create_device<MemoryDevice>();
// FIXME: Find a way to propagate errors
VERIFY(!memory_device_or_error.is_error());
return memory_device_or_error.release_value();
}
UNMAP_AFTER_INIT MemoryDevice::MemoryDevice()
: CharacterDevice(1, 1)
{
}
UNMAP_AFTER_INIT MemoryDevice::~MemoryDevice() = default;
ErrorOr<size_t> MemoryDevice::read(OpenFileDescription&, u64 offset, UserOrKernelBuffer& buffer, size_t length)
{
if (!MM.is_allowed_to_read_physical_memory_for_userspace(PhysicalAddress(offset), length)) {
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);
return EINVAL;
}
auto mapping = TRY(Memory::map_typed<u8>(PhysicalAddress(offset), length));
auto bytes = ReadonlyBytes { mapping.ptr(), length };
TRY(buffer.write(bytes));
return length;
}
ErrorOr<NonnullLockRefPtr<Memory::VMObject>> MemoryDevice::vmobject_for_mmap(Process&, Memory::VirtualRange const& range, u64& offset, bool)
{
auto viewed_address = PhysicalAddress(offset);
// Note: This check happens to guard against possible memory leak.
// For example, if we try to mmap physical memory from 0x1000 to 0x2000 and you
// can actually mmap only from 0x1001, then we would fail as usual.
// However, in such case if we mmap from 0x1002, we are technically not violating
// any rules, besides the fact that we mapped an entire page with two bytes which we
// were not supposed to see. To prevent that, if we use mmap(2) syscall, we should
// always consider the start page to be aligned on PAGE_SIZE, or to be more precise
// is to be set to the page base of that start address.
VERIFY(viewed_address == viewed_address.page_base());
if (!MM.is_allowed_to_read_physical_memory_for_userspace(viewed_address, range.size())) {
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());
return EINVAL;
}
offset = 0;
return TRY(Memory::AnonymousVMObject::try_create_for_physical_range(viewed_address, range.size()));
}
}
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