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Difference Between Call Gate, Interrupt Gate, Trap Gate

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  • Last Updated : 04 Jul, 2022
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Gate is used to transfer performance control across all segments. The level of rights assessment is done differently depending on the type of site and the instructions used. Other than that these three gates are almost identical except that Call Gate has parameters for calculating parameters, and that these three gates have different types of fields, the same for all other fields. 

Coming on to their respective functions they are used to transfer code control into some procedure within some code segment. In this article, we will see the difference between Call Gate, Interrupt Gate, and Trap Gate.

Types of Gates: 

Call Gate: The telephone gate is called by the command CALL and JMP. Stored in GDL and LDT. It is said to be similar to a trap gate but has an add-on feature that can transfer a number of parameters from the user-mode function stack to the kernel-mode function stack. The fence gate is special in that it does not open with a disturbing vector.
Call Gates has never been more popular and some of the features are listed below:

  • They are not very good.
  • Fence gates are easily replaced by trap gates.
  • They are not very much flexible.
  • It has very limited mobile options.

Interrupt Gate: Interrupt Gate is called by the instruction INT. It can only be stored only in IDT. The same applies here also it is very much similar to a trap gate but has an additional feature on it i.e. these gates all additionally prohibit future interrupt acceptance by automatic clearing of the IF flag in the EFLAGS register. An interrupt gate is very special in itself because the IF flag is automatically cleared.

Interrupt gates are effectively used to disrupt or interrupt management, especially on PIC-based machines. The reason is the need to control the depth of the stack. PIC has no disturbing resources feature. Because of this by default,  PIC only disables interruptions that have already been captured in the processor. At times some interruptions can still interrupt management and to deal with it kernel developers are forced to increase the size of the kernel stack which leads to nothing but memory retention.

Trap Gate: Trap Gate is called by the instruction INT. It can only be stored only in IDT. This is nothing but a basic type of gate because it often has a small task to do i.e. it passes control to the particular address specified in the trap gate descriptor in the more privileged segment. A Trap gate is very special in itself because it is a default solution for kernel interfacing.

Trap gates are often used in many things and a few of them are listed below:

  • System call activation.
  • A different management implementation.
  • Disrupting administrative performance on machines with APIC.

Difference between Call Gate, Interrupt Gate, and Trap Gate:

Call GateInterrupt GateTrap Gate
Called by the instruction CALL and JMPCalled by the instruction INTCalled by the instruction INT
Stored in GDL and LDTStored in IDTStored in IDT
Has a special feature of transferring the parametersA special feature is these gates all additionally prohibit future interrupt acceptanceNo special feature
Flexibility is very lessFlexibility is more as compared to trap gate Flexibility is more as compared to Interrupt gate
Very less portable options More portability options as compared to trap gate More portability options as compared to Interrupt gate
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