Intel® ISA Extensions
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Selector to gate ?

carsten2
Beginner
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Intel docu states for the far Call (FF /3) m16:32

In 64-bit mode: If selector points to a gate, then RIP = 64-bit displacement taken from gate; else RIP = zero extended 32-bit offset from far pointer referenced in the instruction.

When points a selector to a gate and when not ? NULL selector, flags ?
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SHIH_K_Intel
Employee
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Quoting - carsten2
Intel docu states for the far Call (FF /3) m16:32

In 64-bit mode: If selector points to a gate, then RIP = 64-bit displacement taken from gate; else RIP = zero extended 32-bit offset from far pointer referenced in the instruction.

When points a selector to a gate and when not ? NULL selector, flags ?

Since a far call allow you to transfer control to user code (at any offset you specify) or from non-privileged space into privileged system code (for example, acall gate). The entry point of the call gate were already set up by the system executive. So you can not expect a user program can enter into privileged system code from ring 3at any arbitrary offset.
If far call were used in other situations, the processor will abide by where you tell it to go.
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