Category: DOS extenders
Flags: available only in protected mode
INT 21 - Phar Lap 386/DOS-Extender v4.0+ - READ/WRITE IDT DESCRIPTOR AX = 253Dh BL = interrupt number ECX = direction (0 = read, 1 = write) DS:EDX -> 8-byte buffer for descriptor Return: CF clear if successful DS:EDX filled if reading CF set on error EAX = error code (0082h if running under DPMI) Desc: access hardware-level IDT rather than the internal 386/DOS-Extender shadow IDT Notes: this call will always fail under DPMI because it is not possible to access the IDT the descriptor is not checked when writing this call can normally be used only by programs running in ring 0 because the processor does not allow an interrupt to be vectored to a less privileged ring