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.\" Copyright (c) 2003 Bruce M Simpson <bms@spc.org>
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.Dd January 23, 2021
.Dt VM_MAP_PROTECT 9
.Os
.Sh NAME
.Nm vm_map_protect
.Nd apply protection bits to a virtual memory region
.Sh SYNOPSIS
.In sys/param.h
.In vm/vm.h
.In vm/vm_map.h
.Ft int
.Fo vm_map_protect
.Fa "vm_map_t map"
.Fa "vm_offset_t start"
.Fa "vm_offset_t end"
.Fa "vm_prot_t new_prot"
.Fa "vm_prot_t new_maxprot"
.Fa "int flags"
.Fc
.Sh DESCRIPTION
The
.Fn vm_map_protect
function sets the protection bits and maximum protection bits of the address
region bounded by
.Fa start
and
.Fa end
within the map
.Fa map .
.Pp
If the
.Fa flags
argument has the
.Dv VM_MAP_PROTECT_SET_PROT
bit set, then the effective protection is set to
.Fa new_prot .
.Pp
If the
.Fa flags
argument has the
.Dv VM_MAP_PROTECT_SET_MAXPROT
bit set, then the maximum protection is set to
.Fa new_maxprot .
Protection bits not included into
.Fa new_maxprot
will be cleared from existing entries.
.Pp
The values specified by
.Fa new_prot
and
.Fa new_maxprot
are not allowed to include any protection bits that are not set in existing
.Va max_protection
on every entry within the range.
The operation will fail if this condition is violated.
For instance, this prevents upgrading a shared mapping of a read-only file
from read-only to read-write.
.Pp
The specified range must not contain sub-maps.
.Sh IMPLEMENTATION NOTES
The function acquires a lock on the
.Fa map
for the duration, by calling
.Xr vm_map_lock 9 .
Also, any in-progress wiring operation on the map affecting the specified
range will cause
.Nm
to sleep, waiting for completion.
.Sh RETURN VALUES
.Bl -tag -width "Dv KERN_PROTECTION_FAILURE"
.It Dv KERN_SUCCESS
The specified protection bits were set successfully.
.It Dv KERN_INVALID_ARGUMENT
A sub-map entry was encountered in the range,
.It Dv KERN_PROTECTION_FAILURE
The value of
.Fa new_prot
or
.Fa new_maxprot
exceed
.Va max_protection
for an entry within the range.
.It Dv KERN_PROTECTION_FAILURE
The map does not allow simultaneous setting of write and execute permissions,
but
.Fa new_prot
has both
.Dv VM_PROT_WRITE
and
.Dv VM_PROT_EXECUTE
set.
.It Dv KERN_RESOURCE_SHORTAGE
A copy-on-write mapping is transitioned from read-only to
read-write, and not enough swap space is available to back the
copied pages.
.It Dv KERN_OUT_OF_BOUNDS
Both new protection and new maximum protection updates were requested,
but the specified
.Fa new_prot
is not a subset of
.Fa new_maxprot .
.El
.Sh SEE ALSO
.Xr vm_map 9
.Sh AUTHORS
This manual page was written by
.An Bruce M Simpson Aq Mt bms@spc.org .