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natalieagus committed Apr 15, 2024
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Expand Up @@ -351,10 +351,10 @@ During this event,
* The illop handler will look at `Reg[R0]` and invoke the right service routine to provide the requested service.
* Upon returning, the service routine will put its return the result in `Reg[R0]`.
* The illop handler resumes the execution of the originating process:
* `Reg[XP] = Reg[XP] -4`
* `JMP[XP]`


{:.note}
There's no need to do `Reg[XP] = Reg[XP]-4` because we don't wish to re-invoke the Trap / SVC when we return to the calling process.

One common scenario where a process running in user mode needs the Kernel service is when it asks for keyboard / mouse input, for example:

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