i386_get_ldt(2) [osx man page]

I386_GET_LDT(2) 					      BSD System Calls Manual						   I386_GET_LDT(2)

NAME

     i386_get_ldt, i386_set_ldt -- manage i386 per-process Local Descriptor Table entries

LIBRARY

     Standard C Library (libc, -lc)

SYNOPSIS

     #include <architecture/i386/table.h>
     #include <i386/user_ldt.h>

     int
     i386_get_ldt(int start_sel, union ldt_entry *descs, int num_sels);

     int
     i386_set_ldt(int start_sel, union ldt_entry *descs, int num_sels);

DESCRIPTION

     The i386_get_ldt() system call will return the list of i386 descriptors that the process has in its LDT.  The i386_set_ldt() system call will
     set a list of i386 descriptors for the current process in its LDT.  Both routines accept a starting selector number start_sel, an array of
     memory that will contain the descriptors to be set or returned descs, and the number of entries to set or return num_sels.

     The argument descs can be either code_desc_t, data_desc_t or call_gate_t and are defined in <architecture/i386/desc.h>.  These structures are
     defined by the architecture as disjoint bit-fields, so care must be taken in constructing them.

     If start_sel is LDT_AUTO_ALLOC, num_sels is 1 and the descriptor pointed to by descs is legal, then i386_set_ldt() will allocate a descriptor
     and return its selector number.

     If num_descs is 1, start_sels is valid, and descs is NULL, then i386_set_ldt() will free that descriptor (making it available to be reallo-
     cated again later).

     If num_descs is 0, start_sels is 0 and descs is NULL then, as a special case, i386_set_ldt() will free all descriptors.

RETURN VALUES

     Upon successful completion, i386_get_ldt() returns the number of descriptors currently in the LDT.  The i386_set_ldt() system call returns
     the first selector set.  In the case when a descriptor is allocated by the kernel, its number will be returned.  Otherwise, a value of -1 is
     returned and the global variable errno is set to indicate the error.

ERRORS

     The i386_get_ldt() and i386_set_ldt() system calls will fail if:

     [EINVAL]		An inappropriate value was used for start_sel or num_sels.

     [EACCES]		The caller attempted to use a descriptor that would circumvent protection or cause a failure.

SEE ALSO

     i386 Microprocessor Programmer's Reference Manual, Intel

WARNING

     You can really hose your process using this.

BSD
								September 20, 1993							       BSD

Check Out this Related Man Page

CLOSE(2)						      BSD System Calls Manual							  CLOSE(2)

NAME

     close -- delete a descriptor

LIBRARY

     Standard C Library (libc, -lc)

SYNOPSIS

     #include <unistd.h>

     int
     close(int d);

DESCRIPTION

     The close() system call deletes a descriptor from the per-process object reference table.	If this is the last reference to the underlying
     object, the object will be deactivated.  For example, on the last close of a file the current seek pointer associated with the file is lost;
     on the last close of a socket(2) associated naming information and queued data are discarded; on the last close of a file holding an advisory
     lock the lock is released (see flock(2)).

     When a process exits, all associated descriptors are freed, but since there is a limit on active descriptors per processes, the close() sys-
     tem call is useful when a large quantity of file descriptors are being handled.

     When a process calls fork(2), all descriptors for the new child process reference the same objects as they did in the parent before the
     fork().  If a new process is then to be run using execve(2), the process would normally inherit these descriptors.  Most of the descriptors
     can be rearranged with dup2(2) or deleted with close() before the execve() is attempted, but if some of these descriptors will still be
     needed if the execve() fails, it is necessary to arrange for them to be closed only if the execve() succeeds.  For this reason, the system
     call

	   fcntl(d, F_SETFD, 1);

     is provided, which arranges that a descriptor ``d'' will be closed after a successful execve(); the system call

	   fcntl(d, F_SETFD, 0);

     restores the default, which is to not close descriptor ``d''.

RETURN VALUES

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

ERRORS

     close() will fail if:

     [EBADF]		d is not an active descriptor.

     [EINTR]		An interrupt was received.

SEE ALSO

     accept(2), execve(2), fcntl(2), flock(2), open(2), pipe(2), socket(2), socketpair(2)

STANDARDS

     The close() function conforms to ISO/IEC 9945-1:1990 (``POSIX.1'').

BSD
								  April 19, 1994							       BSD

Linux and UNIX Man Pages

i386_get_ldt(2) [osx man page]

Check Out this Related Man Page