redhat man page for modify_ldt

MODIFY_LDT(2)						     Linux Programmer's Manual						     MODIFY_LDT(2)

NAME
       modify_ldt - get or set ldt

SYNOPSIS
       #include <linux/ldt.h>
       #include <linux/unistd.h>

       _syscall3( int, modify_ldt, int, func, void *, ptr, unsigned long, bytecount )

       int modify_ldt(int func, void *ptr, unsigned long bytecount);

DESCRIPTION
       modify_ldt  reads  or  writes the local descriptor table (ldt) for a process.  The ldt is a per-process memory management table used by the
       i386 processor.	For more information on this table, see an Intel 386 processor handbook.

       When func is 0, modify_ldt reads the ldt into the memory pointed to by ptr.  The number of bytes read is the smaller of bytecount  and  the
       actual size of the ldt.

       When  func  is  1, modify_ldt modifies one ldt entry.  ptr points to a modify_ldt_ldt_s structure and bytecount must equal the size of this
       structure.

RETURN VALUE
       On success, modify_ldt returns either the actual number of bytes read (for reading) or 0 (for writing).	On failure, modify_ldt returns	-1
       and sets errno.

ERRORS
       ENOSYS func is neither 0 nor 1.

       EINVAL ptr  is 0, or func is 1 and bytecount is not equal to the size of the structure modify_ldt_ldt_s, or func is 1 and the new ldt entry
	      has invalid values.

       EFAULT ptr points outside the address space.

CONFORMING TO
       This call in Linux-specific and should not be used in programs intended to be portable.

SEE ALSO
       vm86(2)

Linux 1.3.6							    1995-07-22							     MODIFY_LDT(2)