munication mechanism is being used when a processor switches from ri example of
ID: 3903388 • Letter: M
Question
munication mechanism is being used when a processor switches from ri example of one of these functions that can make this transition. (3) 2. What kernel ng 3 to ring 0? Give one pes of devices can you find embedded operating systems, and why would they be embedded? (4) 4 Your driver is running well, but keeps looking for data too soon from the sensor. You need to "delay for 3 milliseconds to correct this. However, the code is running in an interrupt context. Write the bit of code you would insert into your driver to properly wait for 3 milliseconds. (5)Explanation / Answer
2. CPU has 4 rings, Among them, Kernel uses Ring 0 and Ring 3, 0 for kernel and 3 for a user,
Ring 0- it can do anything whereas,
Ring 3 - it cannot change its own ring, else it would swap to 0 and the rings would be useless.
now let us understand the communication is used while a processor switches from Ring 3 to Ring 0,
the Cpu starts with the initial program in ring 0 when the user wants the kernel to do something like Write or read a file than the instruction generates an interrupt to signal the Kernel than The handler runs in ring 0, which decides if the kernel will allow this action or not, then it does perform the action and restarts the program in Ring 3.
if the program tries to perform some bad task like write a forbidden registry or memory address, then the CPU calls some kernel callback handler in ring 0 that is userland, but at the same kernel might kill the process for a time and will send the security message.
when the kernel boots it setups hardware clock which generates interrupts that Run Ring 0 and allow it to schedule userland processes to wake up
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