NAME

modify_ldt - get or set ldt

SYNOPSIS

#include <linux/ldt.h> #include <linux/unistd> _syscall(int modify_ldt, int func, void *ptr, unsigned long bytecount ) char *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 illegal values.

EFAULT

ptr points outside the address space.

CONFORMING TO

This call in Linux-specfic and should not be used in programs intended to be portable.

SEE ALSO

vm86(2)