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.\" Copyright (c) 2023 Ian Marco Moffett and the Osmora Team.
.\" 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.
.\" 3. Neither the name of Hyra nor the names of its
.\" contributors may be used to endorse or promote products derived from
.\" this software without specific prior written permission.
.\"
.\" 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 OWNER 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.
.TH VM 9 2023-12-15 "Osmora" "Hyra Operating System"
.Sh NAME
.Nm vm - hyra machine independent virtual memory layer
.Sh SYNOPSIS
.In vm/vm.h
.Sh DESCRIPTION
The Hyra virtual memory subsystem handles various aspects of
virtual memory like memory mapping, keeping track of the virtual
memory context per core, etc.
The term `kernel physical address' will be used to describe physical
addresses that are mapped to the higher half.
The
.Ft VM_HIGHER_HALF
macro points to the higher half of the virtual memory space...
The mapping of kernel physical addresses to virtual addresses are
done with respect to the higher half, i.e., virtual = physical + hddm
(where hddm is the higher half). This cleanly reserves the lower half
of the virtual address space for userspace applications.
The
.Ft PHYS_TO_VIRT
macro converts a kernel physical address to a higher half
virtual address.
The
.Ft VIRT_TO_PHYS
macro converts a higher half virtual address to a kernel
physical address.
.Sh AUTHORS
.An Ian Moffett Aq Mt ian@osmora.org
.Sh SEE ALSO
.Xr dynalloc 9
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