modify_ldt — get or set ldt
#include <sys/types.h>
#include <linux/unistd.h>
#include <errno.h>
_syscall3(int, modify_ldt, int, func, void *, ptr,
unsigned long, bytecount)
/* Using syscall(2) may be preferable; see intro(2) */
int
modify_ldt( |
int | func, |
| void * | ptr, | |
| unsigned long | bytecount); |
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.
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.
ptr points
outside the address space.
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.
func is
neither 0 nor 1.
This call is Linux specific and should not be used in programs intended to be portable.
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