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kernel mode

The unrestricted way the processor runs the operating system's core (the kernel), which is allowed to control devices and all memory.

Kernel mode (ring 0 on x86-64, EL1 on ARM64, S-mode on RISC-V) is the privileged mode in which the operating-system kernel runs; entry from user mode happens only through defined gates such as system calls, exceptions and interrupts.

See also

user mode system call instruction
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