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nvlist_alloc(9f)
nvlist_alloc(9F) Kernel Functions nvlist_alloc(9F)
NAME
nvlist_alloc, nvlist_free, nvlist_size, nvlist_pack, nvlist_unpack,
nvlist_dup, nv_alloc_init, nv_alloc_fini, nvlist_xalloc, nvlist_xpack,
nvlist_xunpack, nvlist_xdup, nvlist_merge - Manage a name-value pair
list
SYNOPSIS
#include <sys/nvpair.h>
List Manipulation:
int nvlist_alloc(nvlist_t **nvlp, uint_t nvflag,
int kmflag);
int nvlist_xalloc(nvlist_t **nvlp, uint_t nvflag, nv_alloc_t *nva);
void nvlist_free(nvlist_t *nvl);
int nvlist_size(nvlist_t *nvl, size_t *size, int encoding);
int nvlist_pack(nvlist_t *nvl, char **bufp, size_t *buflen, int encoding,
int flag);
int nvlist_xpack(nvlist_t *nvl, char **bufp, size_t *buflen, int encoding,
nv_alloc_t *nva);
int nvlist_unpack(char *buf, size_t buflen, nvlist_t **nvlp, int flag);
int nvlist_xunpack(char *buf, size_t buflen, nvlist_t **nvlp,
nv_alloc_t *nva);
int nvlist_dup(nvlist_t *nvl, nvlist_t **nvlp, int flag);
int nvlist_xdup(nvlist_t *nvl, nvlist_t **nvlp, nv_alloc_t *nva);
int nvlist_merge(nvlist_t *dst, nvlist_t *nvl, int flag);
Pluggable Allocator Configuration:
nv_alloc_t *nvlist_lookup_nv_alloc(nvlist_t *);
int nv_alloc_init(nv_alloc_t *nva,
const nv_alloc_ops_t * nvo,/* args */ ...);
void nv_alloc_reset(nv_alloc_t *nva);
void nv_alloc_fini(nv_alloc_t *nva);
Pluggable Allocation Initialization with Fixed Allocator:
int nv_alloc_init(nv_alloc_t *nva,
nv_fixed_ops, void * bufptr, size_t sz);
INTERFACE LEVEL
Solaris DDI specific (Solaris DDI)
PARAMETERS
nvlp Address of a pointer to list of name-value pairs
(nvlist_t).
nvflag Specify bit fields defining nvlist_t properties:
NV_UNIQUE_NAME nvpair names are unique.
NV_UNIQUE_NAME_TYPE Name-data type combination is unique
kmflag Kernel memory allocation policy, either KM_SLEEP or
KM_NOSLEEP.
nvl nvlist_t to be processed.
dst Destination nvlist_t.
size Pointer to buffer to contain the encoded size.
bufp Address of buffer to pack nvlist into. Must be 8-byte
aligned. If NULL, library will allocate memory.
buf Buffer containing packed nvlist_t.
buflen Size of buffer bufp or buf points to.
encoding Encoding method for packing.
nvo Pluggable allocator operations pointer (nv_alloc_ops_t).
nva Points to a nv_alloc_t structure to be used for the speci‐
fied nvlist_t.
DESCRIPTION
List Manipulation:
The nvlist_alloc() function allocates a new name-value pair list and
updates nvlp to point to the handle. The argument nvflag specifies
nvlist_t properties to remain persistent across packing, unpacking, and
duplication.
If NV_UNIQUE_NAME is specified for nvflag, existing nvpairs with match‐
ing names are removed before the new nvpair is added. If
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 nvlist_add_byte(9F) for more details.
The nvlist_xalloc() function differs from nvlist_alloc() in that
nvlist_xalloc() can use a different allocator, as described in the
Pluggable Allocators section.
The nvlist_free() function frees a name-value pair list.
The nvlist_size() function returns the minimum size of a contiguous
buffer large enough to pack nvl. The encoding parameter specifies the
method of encoding when packing nvl. Supported encoding methods are:
NV_ENCODE_NATIVE Straight bcopy() as described in bcopy(9F).
NV_ENCODE_XDR Use XDR encoding, suitable for sending to another
host.
The nvlist_pack() function packs nvl into contiguous memory starting at
*bufp. The encoding parameter specifies the method of encoding (see
above).
o If *bufp is not NULL, *bufp is expected to be a caller-allo‐
cated buffer of size *buflen. The kmflag argument is
ignored.
o If *bufp is NULL, the library allocates memory and updates
*bufp to point to the memory and updates *buflen to contain
the size of the allocated memory. The value of kmflag indi‐
cates the memory allocation policy
The nvlist_xpack() function differs from nvlist_pack() in that
nvlist_xpack() can use a different allocator.
The nvlist_unpack() function takes a buffer with a packed nvlist_t and
unpacks it into a searchable nvlist_t. The library allocates memory for
nvlist_t. The caller is responsible for freeing the memory by calling
nvlist_free().
The nvlist_xunpack() function differs from nvlist_unpack() in that
nvlist_xunpack() can use a different allocator.
The nvlist_dup() function makes a copy of nvl and updates nvlp to point
to the copy.
The nvlist_xdup() function differs from nvlist_dup() in that
nvlist_xdup() can use a different allocator.
The nvlist_merge() function adds copies of all name-value pairs from
nvlist_t nvl to nvlist_t dst. Name-value pairs in dst are replaced
with name-value pairs from nvl which have identical names (if dst has
the type NV_UNIQUE_NAME), or identical names and types (if dst has the
type NV_UNIQUE_NAME_TYPE).
The nvlist_lookup_nv_alloc() function retrieves the pointer to the
allocator used when manipulating a name-value pair list.
PLUGGABLE ALLOCATORS
Using Pluggable Allocators:
The nv_alloc_init(), nv_alloc_reset() and nv_alloc_fini() functions
provide an interface that specifies the allocator to be used when
manipulating a name-value pair list.
The nv_alloc_init() determines allocator properties and puts them into
the nva argument. You need to specify the nv_arg argument, the nvo
argument and an optional variable argument list. The optional arguments
are passed to the (*nv_ao_init()) function.
The nva argument must be passed to nvlist_xalloc(), nvlist_xpack(),
nvlist_xunpack() and nvlist_xdup().
The nv_alloc_reset() function resets the allocator properties to the
data specified by nv_alloc_init(). When no (*nv_ao_reset()) function is
specified, nv_alloc_reset() is without effect.
The nv_alloc_fini() destroys the allocator properties determined by
nv_alloc_init(). When a (*nv_ao_fini()) routine is specified, it is
called from nv_alloc_fini().
The disposition of the allocated objects and the memory used to store
them is left to the allocator implementation.
The 'nv_alloc_sleep' and 'nv_alloc_nosleep' nv_alloc_t pointers may be
used with nvlist_xalloc to mimic the behavior of nvlist_alloc with
KM_SLEEP and KM_NOSLEEP, respectively.
o nv_alloc_nosleep
o nv_alloc_sleep
The nvpair framework provides a fixed-buffer allocator, accessible via
nv_fixed_ops.
o nv_fixed_ops
Given a buffer size and address, the fixed-buffer allocator allows for
the creation of nvlists in contexts where malloc or kmem_alloc services
may not be available. The fixed-buffer allocator is designed primarily
to support the creation of nvlists.
Memory freed using nvlist_free(), pair-removal, or similar routines is
not reclaimed.
When used to initialize the fixed-buffer allocator, nv_alloc_init
should be called as follows:
int nv_alloc_init(nv_alloc_t *nva, const nv_alloc_ops_t *nvo,
void *bufptr, size_t sz);
When invoked on a fixed-buffer, the nv_alloc_reset() function resets
the fixed buffer and prepares it for re-use. The framework consumer is
responsible for freeing the buffer passed to nv_alloc_init().
CREATING PLUGGABLE ALLOCATORS
Any producer of name-value pairs may possibly specify custom allocator
routines. You must provide the following pluggable allocator operations
in the allocator implementation.
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);
The nva argument of the allocator implementation is always the first
argument.
The optional (*nv_ao_init() ) function is responsible for filling the
data specified by nv_alloc_init() into the nva_arg() argument. The
(*nv_ao_init()) function is called only when nv_alloc_init() is exe‐
cuted.
The optional (*nv_ao_fini()) function is responsible for the cleanup of
the allocator implementation. It is called by nv_alloc_fini().
The required (*nv_ao_alloc()) function is used in the nvpair allocation
framework for memory allocation. The sz argument specifies the size of
the requested buffer.
The optional (*nv_ao_reset()) function is responsible for resetting the
nva_arg argument to the data specified by nv_alloc_init().
The required (*nv_ao_free()) function is used in the nvpair allocator
framework for memory de-allocation. The argument buf is a pointer to a
block previously allocated by (*nv_ao_alloc()) function. The size argu‐
ment sz must exactly match the original allocation.
The disposition of the allocated objects and the memory used to store
them is left to the allocator implementation.
RETURN VALUES
For nvlist_alloc(), nvlist_dup(), nvlist_xalloc(), and nvlist_xdup():
0 success
EINVAL invalid argument
ENOMEM insufficient memory
For nvlist_pack(), nvlist_unpack(), nvlist_xpack(), and nvlist_xun‐
pack():
0 success
EINVAL invalid argument
ENOMEM insufficient memory
EFAULT encode/decode error
ENOTSUP encode/decode method not supported
For nvlist_size():
0 success
EINVAL invalid argument
For nvlist_lookup_nv_alloc():
pointer to the allocator
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.
EXAMPLES
/*
* using the fixed-buffer allocator.
*/
#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);
}
CONTEXT
The nvlist_alloc(), nvlist_pack(), nvlist_unpack(), and nvlist_dup()
functions can be called from interrupt context only if the KM_NOSLEEP
flag is set. They can be called from user context with any valid flag.
The nvlist_xalloc(), nvlist_xpack(), nvlist_xunpack(), and
nvlist_xdup() functions can be called from interrupt context only if
(1) the default allocator is used and the KM_NOSLEEP flag is set or (2)
the specified allocator did not sleep for free memory (for example, it
uses a pre-allocated buffer for memory allocations).
These functions can be called from user or kernel context with any
valid flag.
Oracle Solaris 11.4 27 Nov 2017 nvlist_alloc(9F)