man/man9f/nvlist_alloc.9f

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.Dd June 12, 2021
.Dt NVLIST_ALLOC 9F
.Os
.Sh NAME
.Nm nvlist_alloc ,
.Nm nvlist_free ,
.Nm nvlist_size ,
.Nm nvlist_pack ,
.Nm nvlist_unpack ,
.Nm nvlist_dup ,
.Nm nv_alloc_init ,
.Nm nv_alloc_fini ,
.Nm nvlist_xalloc ,
.Nm nvlist_xpack ,
.Nm nvlist_xunpack ,
.Nm nvlist_xdup ,
.Nm nvlist_merge
.Nd Manage a name-value pair list
.Sh SYNOPSIS
.In sys/nvpair.h
.Ss List Manipulation
.Ft int
.Fo nvlist_alloc
.Fa "nvlist_t **nvlp"
.Fa "uint_t nvflag"
.Fa "int kmflag"
.Fc
.Ft int
.Fo nvlist_xalloc
.Fa "nvlist_t **nvlp"
.Fa "uint_t nvflag"
.Fa "nv_alloc_t *nva"
.Fc
.Ft void
.Fo nvlist_free
.Fa "nvlist_t *nvl"
.Fc
.Ft int
.Fo nvlist_size
.Fa "nvlist_t *nvl"
.Fa "size_t *size"
.Fa "int encoding"
.Fc
.Ft int
.Fo nvlist_pack
.Fa "nvlist_t *nvl"
.Fa "char **bufp"
.Fa "size_t *buflen"
.Fa "int encoding"
.Fa "int flag"
.Fc
.Ft int
.Fo nvlist_xpack
.Fa "nvlist_t *nvl"
.Fa "char **bufp"
.Fa "size_t *buflen"
.Fa "int encoding"
.Fa "nv_alloc_t *nva"
.Fc
.Ft int
.Fo nvlist_unpack
.Fa "char *buf"
.Fa "size_t buflen"
.Fa "nvlist_t **nvlp"
.Fa "int kmflag"
.Fc
.Ft int
.Fo nvlist_xunpack
.Fa "char *buf"
.Fa size_t buflen"
.Fa nvlist_t **nvlp"
.Fa nv_alloc_t *nva"
.Fc
.Ft int
.Fo nvlist_dup
.Fa "nvlist_t *nvl"
.Fa "nvlist_t **nvlp"
.Fa "int kmflag"
.Fc
.Ft int
.Fo nvlist_xdup
.Fa "nvlist_t *nvl"
.Fa "nvlist_t **nvlp"
.Fa "nv_alloc_t *nva"
.Fc
.Ft int
.Fo nvlist_merge
.Fa "nvlist_t *dst"
.Fa "nvlist_t *nvl"
.Fa "int kmflag"
.Fc
.Ss Pluggable Allocator Configuration
.Ft "nv_alloc_t *"
.Fo nvlist_lookup_nv_alloc
.Fa "nvlist_t *nvl"
.Fc
.Ft int
.Fo nv_alloc_init
.Fa "nv_alloc_t *nva"
.Fa "const nv_alloc_ops_t *nvo"
.Fa "..."
.Fc
.Ft void
.Fo nv_alloc_reset
.Fa "nv_alloc_t *nva"
.Fc
.Ft void
.Fo nv_alloc_fini
.Fa "nv_alloc_t *nva"
.Fc
.Ss Pluggable Allocation Initialization with Fixed Allocator
.Ft int
.Fo nv_alloc_init
.Fa "nv_alloc_t *nva"
.Fa "nv_fixed_ops"
.Fa "void *bufptr"
.Fa "sz"
.Fc
.Sh INTERFACE LEVEL
illumos DDI specific (illumos DDI)
.Sh PARAMETERS
.Bl -tag -width Fa
.It Fa nvlp
Address of a pointer to list of name-value pairs
.Pq Ft nvlist_t .
.It Fa nvflag
Specify bit fields defining
.Ft nvlist_t
properties:
.Bl -tag -width Dv
.It Dv NV_UNIQUE_NAME
nvpair names are unique.
.It Dv NV_UNIQUE_NAME_TYPE
Name-data type combination is unique
.El
.It Fa kmflag
Kernel memory allocation policy, either
.Dv KM_SLEEP
or
.Dv KM_NOSLEEP .
.It Fa nvl
.Ft nvlist_t
to be processed.
.It Fa dst
Destination
.Ft nvlist_t .
.It Fa size
Pointer to buffer to contain the encoded size.
.It Fa bufp
Address of buffer to pack nvlist into.
Must be 8-byte aligned.
If
.Dv NULL ,
library will allocate memory.
.It buf
Buffer containing packed
.Ft nvlist_t .
.It buflen buflen
Size of buffer
.Fa bufp
or
.Fa buf
points to.
.It Fa encoding
Encoding method for packing.
.It Fa nvo
Pluggable allocator operations pointer
.Pq Ft nv_alloc_ops_t .
.It nva
Points to a
.Ft nv_alloc_t
structure to be used for the specified
.Ft nvlist_t .
.El
.Sh DESCRIPTION
.Ss List Manipulation
The
.Fn nvlist_alloc
function allocates a new name-value pair list and updates
.Fa nvlp
to point to the handle.
The argument
.Fa nvflag
specifies
.Ft nvlist_t
properties to remain persistent across packing, unpacking, and duplication.
.Pp
If
.Dv NV_UNIQUE_NAME
is specified for nvflag, existing nvpairs with matching names are removed
before the new nvpair is added.
If
.Dv NV_UNIQUE_NAME_TYPE
is specified for nvflag, existing nvpairs with matching names and data types
are removed before the new nvpair is added.
See
.Xr nvlist_add_byte 9F
for more details.
.Pp
The
.Fn nvlist_xalloc
function differs from
.Fn nvlist_alloc
in that
.Fn nvlist_xalloc
can use a different allocator, as described in the
.Sx Pluggable Allocators
section.
.Pp
The
.Fn nvlist_free
function frees a name-value pair list.
If
.Fa nvl
is a null pointer, no action occurs.
.Pp
The
.Fn nvlist_size
function returns the minimum size of a contiguous buffer large enough to pack
.Fa nvl .
The
.Fa encoding
parameter specifies the method of encoding when packing
.Fa nvl
Supported encoding methods are:
.Bl -tag -width Dv -offset indent
.It Dv NV_ENCODE_NATIVE
Straight
.Fn bcopy
as described in
.Xr bcopy 9F .
.It Dv NV_ENCODE_XDR
Use XDR encoding, suitable for sending to another host.
.El
.Pp
The
.Fn nvlist_pack
function packs
.Fa nvl
into contiguous memory starting at
.Pf * Fa bufp .
The
.Fa encoding
parameter specifies the method of encoding (see above).
.Bl -bullet -offset indent
.It
If
.Pf * Fa bufp
is not
.Dv NULL ,
.Pf * Fa bufp
is expected to be a caller-allocated buffer of size
.Pf * Fa buflen .
The
.Fa kmflag
argument is ignored.
.It
If
.Pf * Fa bufp
is
.Dv NULL ,
the library allocates memory and updates
.Pf * Fa bufp
to point to the memory and updates
.Pf * Fa buflen
to contain the size of the allocated memory.
The value of
.Fa kmflag
indicates the memory allocation policy
.El
.Pp
The
.Fn nvlist_xpack
function differs from
.Fn nvlist_pack
in that
.Fn nvlist_xpack
can use a different allocator.
.Pp
The
.Fn nvlist_unpack
function takes a buffer with a packed
.Ft nvlist_t
and unpacks it into a searchable
.Ft nvlist_t .
The library allocates memory for
.Ft nvlist_t .
The caller is responsible for freeing the memory by calling
.Fn nvlist_free
.Pp
The
.Fn nvlist_xunpack
function differs from
.Fn nvlist_unpack
in that
.Fn nvlist_xunpack
can use a different allocator.
.Pp
The
.Fn nvlist_dup
function makes a copy of
.Fa nvl
and updates
.Fa nvlp
to point to the copy.
.Pp
The
.Fn nvlist_xdup
function differs from
.Fn nvlist_dup
in that
.Fn nvlist_xdup
can use a different allocator.
.Pp
The
.Fn nvlist_merge
function adds copies of all name-value pairs from
.Fa "nvlist_t nvl"
to
.Fa "nvlist_t dst" .
Name-value pairs in
.Fa dst
are replaced with name-value pairs from
.Fa nvl
which have identical names
.Po
if
.Fa dst
has the type
.Dv NV_UNIQUE_NAME
.Pc
or identical names and types
.Po
if
.Fa dst
has the type
.Dv NV_UNIQUE_NAME_TYPE
.Pc .
.Pp
The
.Fn nvlist_lookup_nv_alloc
function retrieves the pointer to the allocator used when manipulating a
name-value pair list.
.Ss "Pluggable Allocators"
The
.Fn nv_alloc_init ,
.Fn nv_alloc_reset ,
and
.Fn nv_alloc_fini
functions provide an interface that specifies the allocator to be used when
manipulating a name-value pair list.
.Pp
The
.Fn nv_alloc_init
determines allocator properties and puts them into
the
.Fa nva
argument.
You need to specify the
.Fa nv_arg
argument, the
.Fa nvo
argument and an optional variable argument list.
The optional arguments are passed to the
.Pf * Fn nv_ao_init
function.
.Pp
The
.Fa nva
argument must be passed to
.Fn nvlist_xalloc ,
.Fn nvlist_xpack ,
.Fn nvlist_xunpack ,
and
.Fn nvlist_xdup .
.Pp
The
.Fn nv_alloc_reset
function resets the allocator properties to the data specified by
.Fn nv_alloc_init .
When no
.Pf * Fn nv_ao_reset
function is specified,
.Fn nv_alloc_reset
is without effect.
.Pp
The
.Fn nv_alloc_fini
destroys the allocator properties determined by
.Fn nv_alloc_init .
When a
.Pf * Fn nv_ao_fini
routine is specified, it is
called from
.Fn nv_alloc_fini .
.Pp
The disposition of the allocated objects and the memory used to store them is
left to the allocator implementation.
.Pp
The
.Va nv_alloc_sleep
and
.Va nv_alloc_nosleep
.Ft nv_alloc_t
pointers may be used with
.Fn nvlist_xalloc
to mimic the behavior of
.Fn nvlist_alloc
with
.Dv KM_SLEEP and
.Dv KM_NOSLEEP ,
respectively.
.Pp
The nvpair framework provides a fixed-buffer allocator, accessible via
.Pp
Given a buffer size and address, the fixed-buffer allocator allows for the
creation of nvlists in contexts where
.Xr malloc 3C
or
.Xr kmem_alloc 9F
services may not be available.
The fixed-buffer allocator is designed primarily to support the creation of
nvlists.
.Pp
Memory freed using
.Fn nvlist_free ,
pair-removal, or similar routines is not reclaimed.
.Pp
When used to initialize the fixed-buffer allocator,
.Fn nv_alloc_init
should be called as follows:
.Pp
.Fo nv_alloc_init
.Fa "nv_alloc_t *nva"
.Fa "nv_fixed_ops"
.Fa "void *bufptr"
.Fa "size_t sz"
.Fc .
.Pp
When invoked on a fixed-buffer, the
\fBnv_alloc_reset()\fR
function resets the fixed buffer and prepares it for re-use.
The framework consumer is responsible for freeing the buffer passed to
\fBnv_alloc_init()\fR.
.Ss Creating Pluggable Allocators
Any producer of name-value pairs may possibly specify his own allocator
routines.
You must provide the following pluggable allocator operations in the allocator
implementation.
.Bd -literal -offset indent
int (*nv_ao_init)(nv_alloc_t *nva, va_list nv_valist);
void (*nv_ao_fini)(nv_alloc_t *nva);
void *(*nv_ao_alloc)(nv_alloc_t *nva, size_t sz);
void (*nv_ao_reset)(nv_alloc_t *nva);
void (*nv_ao_free)(nv_alloc_t *nva, void *buf, size_t sz);
.Ed
.Pp
The
.Fa nva
argument of the allocator implementation is always the first argument.
.Pp
The optional
.Pf * Fn nv_ao_init
function is responsible for filling the data specified by
.Fn nv_alloc_init
into the
.Fa nva_arg
member.
 The
.Pf * Fn nv_ao_init
function is called only when
.Fn nv_alloc_init
is executed.
.Pp
The optional
.Pf * Fn nv_ao_fini
function is responsible for the cleanup of the allocator implementation.
It is called by
.Fn nv_alloc_fini .
.Pp
The required
.Pf * Fn nv_ao_alloc
function is used in the nvpair allocation framework for memory allocation.
The
.Fa sz
argument specifies the size of the requested buffer.
.Pp
The optional
.Pf * Fn nv_ao_reset
function is responsible for resetting the
.Fa nva_arg
member to the data specified by
.Fn nv_alloc_init .
.Pp
The required
.Pf * Fn nv_ao_free
function is used in the nvpair allocator framework for memory de-allocation.
The argument
.Fa buf
is a pointer to a block
previously allocated by
.Pf * Fn nv_ao_alloc
function.
The size argument
.Fa sz
must exactly match the original allocation.
.Pp
The disposition of the allocated objects and the memory used to store them is
left to the allocator implementation.
.Sh CONTEXT
The
.Fn nvlist_alloc ,
.Fn nvlist_pack ,
.Fn nvlist_unpack ,
and
.Fn nvlist_dup
functions can be called from interrupt context only if the
.Dv KM_NOSLEEP
flag is set.
They can be called from user context with any valid flag.
.Pp
The
.Fn nvlist_xalloc ,
.Fn nvlist_xpack ,
.Fn nvlist_xunpack ,
and
.Fn nvlist_xdup
functions can be called from interrupt context only if
.Pq 1
the default allocator is used and the
.Dv KM_NOSLEEP
flag is set or
.Pq 2
the specified allocator did not sleep for free memory
.Pq for example, it uses a pre-allocated buffer for memory allocations .
.Pp
These functions can be called from user or kernel context with any valid flag.
.Sh RETURN VALUES
For
.Fn nvlist_alloc ,
.Fn nvlist_dup ,
.Fn nvlist_xalloc ,
and
.Fn nvlist_xdup :
.Bl -tag -width Er
.It Er 0
success
.It Er EINVAL
invalid argument
.It Er ENOMEM
insufficient memory
.El
.Pp
For
.Fn nvlist_pack ,
.Fn nvlist_unpack ,
.Fn nvlist_xpack ,
and
.Fn nvlist_xunpack :
.Bl -tag -width Er
.It Sy 0
success
.It Er EINVAL
invalid argument
.It Er ENOMEM
insufficient memory
.It Er EFAULT
encode/decode error
.It Er ENOTSUP
encode/decode method not supported
.El
.Pp
For
.Fn nvlist_size :
.Bl -tag -width Er
.It Sy 0
success
.It Er EINVAL
.El
.Pp
The
.Fn nvlist_lookup_nv_alloc
function returns a pointer to the allocator or
.Dv NULL
if there is no allocator.
.Sh USAGE
The fixed-buffer allocator is very simple allocator.
It uses a pre-allocated buffer for memory allocations and it can be used in
interrupt context.
You are responsible for allocation and de-allocation for the pre-allocated
buffer.
.Sh EXAMPLES
.Sy Example 1
Using the fixed-buffer allocator
.Bd -literal -offset indent
#include <sys/nvpair.h>

/* initialize the nvpair allocator framework */
static nv_alloc_t *
init(char *buf, size_t size)
{
	nv_alloc_t *nvap;

	if ((nvap = kmem_alloc(sizeof(nv_alloc_t), KM_SLEEP)) == NULL)
	   return (NULL);

	if (nv_alloc_init(nvap, nv_fixed_ops, buf, size) == 0)
	   return (nvap);

	return (NULL);
}

static void
fini(nv_alloc_t *nvap)
{
	nv_alloc_fini(nvap);
	kmem_free(nvap, sizeof(nv_alloc_t));
}

static int
interrupt_context(nv_alloc_t *nva)
{
	nvlist_t *nvl;
	int error;

	if ((error = nvlist_xalloc(&nvl, NV_UNIQUE_NAME, nva)) != 0)
	    return (-1);

	if ((error = nvlist_add_int32(nvl, "name", 1234)) == 0)
	    error = send_nvl(nvl);

	nvlist_free(nvl);
	return (error);
}
.Ed
.Sh SEE ALSO
.Xr bcopy 9F ,
.Xr kmem_alloc 9F ,
.Xr nvlist_add_byte 9F