Modern Use
Modern X86 operating systems are transitioning away from CALL FAR callgates. With the introduction of SYSENTER/SYSEXIT and SYSCALL/SYSRET, a new faster mechanism was introduced for control transfers for x86 programs. And as most other architectures do not support call gates, their use was rare even before these new instructions as software interrupts/traps were preferred for portability.
Call gates are more flexible than the SYSENTER/SYSEXIT and SYSCALL/SYSRET instructions since unlike the latter two, call gates allow for changing from an arbitrary privilege level to an arbitrary (albeit higher or equal) privilege level. The fast SYS* instruction only allow control transfers from ring 3->0 and vice versa. Upon comparing call gates to interrupts, call gates are significantly faster.
Read more about this topic: Call Gate
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