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Hello, in this video, we will wrap up the section by doing a simple test. Remember when we write the handler 

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in the trap.c file, we just halt the system if the exception or unknown interrupts occur. 

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At this point, we have exit and wait functions in the kernel. So we can force a process to exit

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if it causes exceptions. 

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To achieve it, we first check to see if the exception is generated in the user mode. 

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If the lower 2 bits is equal to 3, then it is in the user mode. If that is the case, this is the error in the program, 

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we call function exit to kill the process and never return. When the wait function is called, 

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the process will be freed.  Also we print message so that we can see which exception it generates

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.

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If the exception is generated in the kernel mode, we halt the system just as we did before.  

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In this example, we also change the user3 program, 

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as you see, it constantly prints message on the screen. So we remove the print function.

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OK.

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In the program user2,

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We manually caused the exception by writing a value in the kernel space.

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If everything goes as expected, we will not see the message of this process printed on the screen.

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OK, let's test it out.

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We copy the user programs in the boot folder

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and we write them in the boot image.

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OK, let's open the virtual machine.

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you can see exception is 14, which is the PF exception, and the message process3 is not

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printed in this case.

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OK, that's it for this lecture.

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See you in the next section.