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.Dd Mar 13 2024
.Dt PMAP 9
.Os Hyra
.Sh NAME
.Nm pmap - hyra machine dependent virtual memory layer
.Sh SYNOPSIS
.In vm/pmap.h

.Bd -literal
int pmap_map(struct vm_ctx *, vaddr_t, paddr_t, vm_prot_t);
int pmap_unmap(struct vm_ctx *, vaddr_t);
.Ed

.Sh DESCRIPTION
The machine dependent virtual memory layer contains a standard set of
functions that shall be implemented per architecture and left alone
outside of vm(9). vm(9) uses pmap routines internally which allows for
abstracting away machine dependent details.

The
.Ft pmap_map()
function is used to map a physical address (paddr_t) to
a virtual address (vaddr_t). The argument of type
vm_prot_t is used to give a mapping certain access
rules. These rules are described below:

The
.Ft PROT_WRITABLE
bit tells pmap_map() to allow writes to the page.
Writes to pages without this bit will result in an exception,
on AMD64 a #PF will occur.

The
.Ft PROT_EXEC
bit tells pmap_map() to allow this page to be
executable. On platforms like AMD64, execution of pages
without this bit will result in an exception from the
instruction fetch, for AMD64, a #PF will occur.

The
.Ft pmap_unmap()
function is used to unmap a virtual address which
leaves the address invalid.

.Sh AUTHORS
.An Ian Moffett Aq Mt ian@osmora.org

.Sh SEE ALSO
.Xr vm 9