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.\" Copyright (c) 1998 Matthew R. Green
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.Dd $Mdocdate: December 9 2022 $
.Dt UVM_MAP 9
.Os
.Sh NAME
.Nm uvm_map ,
.Nm uvm_map_pageable ,
.Nm uvm_map_pageable_all ,
.Nm uvm_map_checkprot ,
.Nm uvm_map_protect ,
.Nm uvmspace_alloc ,
.Nm uvmspace_exec ,
.Nm uvmspace_fork ,
.Nm uvmspace_free ,
.Nm uvmspace_share ,
.Nm uvm_uarea_alloc ,
.Nm uvm_uarea_free ,
.Nm UVM_MAPFLAG
.Nd virtual address space management interface
.Sh SYNOPSIS
.In sys/param.h
.In uvm/uvm.h
.Ft int
.Fn uvm_map "vm_map_t map" "vaddr_t *startp" "vsize_t size" "struct uvm_object *uobj" "voff_t uoffset" "vsize_t alignment" "unsigned int flags"
.Ft int
.Fn uvm_map_pageable "vm_map_t map" "vaddr_t start" "vaddr_t end" "boolean_t new_pageable" "int lockflags"
.Ft int
.Fn uvm_map_pageable_all "vm_map_t map" "int flags" "vsize_t limit"
.Ft boolean_t
.Fn uvm_map_checkprot "vm_map_t map" "vaddr_t start" "vaddr_t end" "vm_prot_t protection"
.Ft int
.Fn uvm_map_protect "vm_map_t map" "vaddr_t start" "vaddr_t end" "vm_prot_t new_prot" "int et" "boolean_t set_max" "boolean_t checkimmutable"
.Ft struct vmspace *
.Fn uvmspace_alloc "vaddr_t min" "vaddr_t max" "boolean_t pageable" "boolean_t remove_holes"
.Ft void
.Fn uvmspace_exec "struct proc *p" "vaddr_t start" "vaddr_t end"
.Ft struct vmspace *
.Fn uvmspace_fork "struct process *pr"
.Ft void
.Fn uvmspace_free "struct vmspace *vm"
.Ft struct vmspace *
.Fn uvmspace_share "struct process *pr"
.Ft vaddr_t
.Fn uvm_uarea_alloc "void"
.Ft void
.Fn uvm_uarea_free "struct proc *p"
.Ft unsigned int
.Fn UVM_MAPFLAG "vm_prot_t prot" "vm_prot_t maxprot" "vm_inherit_t inh" "int advice" "int flags"
.Sh DESCRIPTION
The
.Fn uvm_map
function establishes a valid mapping in map
.Fa map ,
which must be unlocked.
The new mapping has size
.Fa size ,
which must be in
.Dv PAGE_SIZE
units.
If
.Fa alignment
is non-zero, it describes the required alignment of the list, in
power-of-two notation.
The
.Fa uobj
and
.Fa uoffset
arguments can have four meanings.
When
.Fa uobj
is
.Dv NULL
and
.Fa uoffset
is
.Dv UVM_UNKNOWN_OFFSET ,
.Fn uvm_map
does not use the machine-dependent
.Dv PMAP_PREFER
function.
If
.Fa uoffset
is any other value, it is used as the hint to
.Dv PMAP_PREFER .
When
.Fa uobj
is not
.Dv NULL
and
.Fa uoffset
is
.Dv UVM_UNKNOWN_OFFSET ,
.Fn uvm_map
finds the offset based upon the virtual address, passed as
.Fa startp .
If
.Fa uoffset
is any other value, we are doing a normal mapping at this offset.
The start address of the map will be returned in
.Fa startp .
.Pp
.Fa flags
passed to
.Fn uvm_map
are typically created using the
.Fn UVM_MAPFLAG
macro, which uses the following values.
The
.Fa prot
and
.Fa maxprot
can take a mix of the following values:
.Bd -literal
#define PROT_MASK   0x07    /* protection mask */
#define PROT_NONE   0x00    /* protection none */
#define PROT_READ   0x01    /* read */
#define PROT_WRITE  0x02    /* write */
#define PROT_EXEC   0x04    /* exec */
.Ed
.Pp
The values that
.Fa inh
can take are:
.Bd -literal
#define MAP_INHERIT_MASK    0x30    /* inherit mask */
#define MAP_INHERIT_SHARE   0x00    /* "share" */
#define MAP_INHERIT_COPY    0x10    /* "copy" */
#define MAP_INHERIT_NONE    0x20    /* "none" */
#define MAP_INHERIT_ZERO    0x30    /* "zero" */
.Ed
.Pp
The values that
.Fa advice
can take are:
.Bd -literal
#define MADV_NORMAL  0x0     /* 'normal' */
#define MADV_RANDOM  0x1     /* 'random' */
#define MADV_SEQUENTIAL 0x2  /* 'sequential' */
#define MADV_MASK    0x7     /* mask */
.Ed
.Pp
The values that
.Fa flags
can take are:
.Bd -literal
#define UVM_FLAG_FIXED   0x0010000 /* find space */
#define UVM_FLAG_OVERLAY 0x0020000 /* establish overlay */
#define UVM_FLAG_NOMERGE 0x0040000 /* don't merge map entries */
#define UVM_FLAG_COPYONW 0x0080000 /* set copy_on_write flag */
#define UVM_FLAG_TRYLOCK 0x0100000 /* fail if we can not lock map */
#define UVM_FLAG_HOLE    0x0200000 /* no backend */
#define UVM_FLAG_QUERY   0x0400000 /* do everything,
                                      except actual execution */
#define UVM_FLAG_NOFAULT 0x0800000 /* don't fault */
#define UVM_FLAG_UNMAP   0x1000000 /* unmap to make space */
#define UVM_FLAG_STACK   0x2000000 /* page may contain a stack */
.Ed
.Pp
The
.Dv UVM_MAPFLAG
macro arguments can be combined with an or operator.
There are also some additional macros to extract bits from the flags.
The
.Dv UVM_PROTECTION ,
.Dv UVM_INHERIT ,
.Dv UVM_MAXPROTECTION
and
.Dv UVM_ADVICE
macros return the protection, inheritance, maximum protection and advice,
respectively.
.Fn uvm_map
returns a standard errno.
.Pp
The
.Fn uvm_map_pageable
function changes the pageability of the pages in the range from
.Fa start
to
.Fa end
in map
.Fa map
to
.Fa new_pageable .
The
.Fn uvm_map_pageable_all
function changes the pageability of all mapped regions.
If
.Fa limit
is non-zero and
.Fn pmap_wired_count
is implemented,
.Dv ENOMEM
is returned if the amount of wired pages exceed
.Fa limit .
The map is locked on entry if
.Fa lockflags
contain
.Dv UVM_LK_ENTER ,
and locked on exit if
.Fa lockflags
contain
.Dv UVM_LK_EXIT .
.Fn uvm_map_pageable
and
.Fn uvm_map_pageable_all
return a standard errno.
.Pp
The
.Fn uvm_map_checkprot
function checks the protection of the range from
.Fa start
to
.Fa end
in map
.Fa map
against
.Fa protection .
This returns either
.Dv TRUE
or
.Dv FALSE .
.Pp
The
.Fn uvm_map_protect
function changes the protection
.Fa start
to
.Fa end
in map
.Fa map
to
.Fa new_prot ,
also setting the maximum protection to the region to
.Fa new_prot
if
.Fa set_max
is non-zero.
The
.Fa et
parameter should be 0, unless a
.Dv PROT_READ | PROT_WRITE
mapping is being changed to extend the stack limit, then it may be
.Dv UVM_ET_STACK .
This function returns a standard errno.
.Pp
The
.Fn uvmspace_alloc
function allocates and returns a new address space, with ranges from
.Fa min
to
.Fa max ,
setting the pageability of the address space to
.Fa pageable .
If
.Fa remove_holes
is non-zero, hardware
.Sq holes
in the virtual address space will be removed from the newly allocated
address space.
.Pp
The
.Fn uvmspace_exec
function either reuses the address space of process
.Fa p
if there are no other references to it, or creates
a new one with
.Fn uvmspace_alloc .
The range of valid addresses in the address space is reset to
.Fa start
through
.Fa end .
.Pp
The
.Fn uvmspace_fork
function creates and returns a new address space based upon the
address space of process
.Fa pr
and is typically used when allocating an address space for a
child process.
.Pp
The
.Fn uvmspace_free
function lowers the reference count on the address space
.Fa vm ,
freeing the data structures if there are no other references.
.Pp
The
.Fn uvmspace_share
function returns a reference to the address space of process
.Fa pr ,
increasing its reference count.
.Pp
The
.Fn uvm_uarea_alloc
function allocates a thread's
.Sq uarea ,
the memory where its kernel stack and PCB are stored.
The
.Fn uvm_uarea_free
function frees the uarea for
thread
.Fa p ,
which must no longer be running.
.Sh SEE ALSO
.Xr pmap 9