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

door_call - invoke the function associated with a door descriptor

cc -mt [ flag... ] file... [ library... ]
#include <door.h>
int door_call(int d, door_arg_t *params);

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:


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


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


The door received is expecting an unreferenced notification.


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


This door does not accept argument descriptors.


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


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).

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

The door_call() function will fail if:


Arguments were too big for server thread stack.


Server was out of available resources.


Invalid door descriptor was passed.


Argument pointers pointed outside the allocated address space.


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


Bad arguments were passed.


The client or server has too many open descriptors.


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.


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)).


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


System could not create overflow area in caller for results.

See attributes(7) for descriptions of the following attributes:

Architecture all
Interface Stability Stable
MT-Level Safe

munmap(2), door_create(3C), door_getparam(3C), door_info(3C), door_return(3C), libdoor(3LIB), attributes(7), cancellation(7), standards(7)

February 7, 2015 OmniOS