MODIFY_LDT Section: Linux Programmer's Manual (2) Updated: 22 July 2025 Index   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 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   Index NAME SYNOPSIS DESCRIPTION RETURN VALUE ERRORS CONFORMING TO SEE ALSO This document was created by using the manual pages. Time: 11:56:06 GMT, March 24, 2025