illumos: manual page: door

DOOR_CALL(3C) Standard C Library Functions DOOR_CALL(3C)

NAME

door_call - invoke the function associated with a door descriptor

SYNOPSIS

cc -mt [ flag... ] file... [ library... ]
#include <door.h>

int door_call(int d, door_arg_t *params);

DESCRIPTION

The door_call() function invokes the function associated with the door
descriptor d, and passes the arguments (if any) specified in params. All
of the params members are treated as in/out parameters during a door
invocation and may be updated upon returning from a door call. Passing
NULL for params indicates there are no arguments to be passed and no
results expected.

The door_arg_t structure includes the following members:

typedef struct {
char *data_ptr; /* Argument/result data */
size_t data_size; /* Argument/result data size */
door_desc_t *desc_ptr; /* Argument/result descriptors */
uint_t desc_num; /* Argument/result num descriptors */
char *rbuf; /* Result area */
size_t rsize; /* Result size */
} door_arg_t;

The door_desc_t structure includes the following members:

typedef struct {
door_attr_t d_attributes; /* Describes the parameter */
union {
struct {
int d_descriptor; /* Descriptor */
door_id_t d_id; /* Unique door id */
} d_desc;
} d_data;
} door_desc_t;

Arguments are specified using the data_ptr and desc_ptr members of
params. The size of the argument data in bytes is passed in data_size and
the number of argument descriptors is passed in desc_num.

Results from the door invocation are placed in the buffer, rbuf. See
door_return(3C). The data_ptr and desc_ptr members of params are updated
to reflect the location of the results within the rbuf buffer. The size
of the data results and number of descriptors returned are updated in the
data_size and desc_num members. It is acceptable to use the same buffer
for input argument data and results, so door_call() may be called with
data_ptr and desc_ptr pointing to the buffer rbuf.

If the results of a door invocation exceed the size of the buffer
specified by rsize, the system automatically allocates a new buffer in
the caller's address space and updates the rbuf and rsize members to
reflect this location. In this case, the caller is responsible for
reclaiming this area using munmap(rbuf, rsize) when the buffer is no
longer required. See munmap(2).

Descriptors passed in a door_desc_t structure are identified by the
d_attributes member. The client marks the d_attributes member with the
type of object being passed by logically OR-ing the value of object type.
Currently, the only object type that can be passed or returned is a file
descriptor, denoted by the DOOR_DESCRIPTOR attribute. Additionally, the
DOOR_RELEASE attribute can be set, causing the descriptor to be closed in
the caller's address space after it is passed to the target. The
descriptor will be closed even if door_call() returns an error, unless
that error is EFAULT or EBADF.

When file descriptors are passed or returned, a new descriptor is created
in the target address space and the d_descriptor member in the target
argument is updated to reflect the new descriptor. In addition, the
system passes a system-wide unique number associated with each door in
the d_id member and marks the d_attributes member with other attributes
associated with a door including the following:

DOOR_LOCAL
The door received was created by this process using
door_create(). See door_create(3C).

DOOR_PRIVATE
The door received has a private pool of server
threads associated with the door.

DOOR_UNREF
The door received is expecting an unreferenced
notification.

DOOR_UNREF_MULTI
Similar to DOOR_UNREF, except multiple unreferenced
notifications may be delivered for the same door.

DOOR_REFUSE_DESC
This door does not accept argument descriptors.

DOOR_NO_CANCEL
This door does not cancel the server thread upon
client abort.

DOOR_REVOKED
The door received has been revoked by the server.

The door_call() function is not a restartable system call. It returns
EINTR if a signal was caught and handled by this thread. If the door
invocation is not idempotent the caller should mask any signals that may
be generated during a door_call() operation. If the client aborts in the
middle of a door_call() and the door was not created with the
DOOR_NO_CANCEL flag, the server thread is notified using the POSIX (see
standards(7)) thread cancellation mechanism. See cancellation(7).

RETURN VALUES

Upon successful completion, 0 is returned. Otherwise, -1 is returned and
errno is set to indicate the error.

ERRORS

The door_call() function will fail if:

E2BIG
Arguments were too big for server thread stack.

EAGAIN
Server was out of available resources.

EBADF
Invalid door descriptor was passed.

EFAULT
Argument pointers pointed outside the allocated address
space.

EINTR
A signal was caught in the client, the client called
fork(2), or the server exited during invocation.

EINVAL
Bad arguments were passed.

EMFILE
The client or server has too many open descriptors.

ENFILE
The desc_num argument is larger than the door's
DOOR_PARAM_DESC_MAX parameter (see door_getparam(3C)), and
the door does not have the DOOR_REFUSE_DESC set.

ENOBUFS
The data_size argument is larger than the door's
DOOR_PARAM_DATA_MAX parameter, or smaller than the door's
DOOR_PARAM_DATA_MIN parameter (see door_getparam(3C)).

ENOTSUP
The desc_num argument is non-zero and the door has the
DOOR_REFUSE_DESC flag set.

EOVERFLOW
System could not create overflow area in caller for results.