Secure Attention Key

The user requests a secure shell by keying a secure attention. The keyboard driver interprets the key sequence CTRL x r as the SAK. An indirect call using the keyboard service vector enables and disables the detection of this key sequence.

If detection of the SAK is enabled, a SAK causes the SAK callback to be invoked. The SAK callback is invoked even if the input ring is inactive due to a user process issuing an open to the keyboard special file. The SAK callback runs within the interrupt environment.