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10–3
retsys Return from system call The retsys instruction pops the return address, the user
stack pointer, and the user global pointer from the kernel stack. It then saves the
kernel stack pointer, sets mode to user, enables interrupts, and jumps to the
address popped off the stack.
rti Return from trap, fault or interrupt The rti instruction pops certain registers
from the kernel stack. If the new mode is user, the kernel stack is saved and the
user stack restored.
swpctx Swap privileged context The swpctx instruction saves the current process data
in the current process control block (PCB). Then swpctx switches to the PCB
and loads the new process context.
swpipl Swap IPL The swpipl instruction returns the current value IPL and sets the IPL.
swppal Swap PALcode image The swppal instruction causes the current PALcode to
be replaced by the specified new PALcode image. Intended only for use by
operating systems during bootstraps and by consoles during transitions to con-
sole I/O mode.
tbi TB invalidate The tbi instruction removes entries from the instruction and data
translation buffers when the mapping entries change.
whami Who_Am_I The whami instruction returns the processor number for the cur-
rent processor. The processor number is in the range 0 to the number of proces-
sors minus one (0..numproc–1) that can be configured in the system.
wrent Write system entry address The wrent instruction sets the virtual address of the
system entry points.
wrfen Write floating-point enable The wrfen instruction writes a bit to the floating-
point enable register.
wripir Write interprocessor interrupt request The wripr instruction generates an inter-
processor interrupt on the processor number passed as an input parameter. The
interrupt request is recorded on the target processor and initiated when the
proper enabling conditions are present.
wrkgp Write kernel global pointer The wrkgp instruction writes the kernel global
pointer internal register.
wrmces Write machine check error summary The wrmces instructions clears the
machine check in progress bit and clears the processor- or system-correctable
error in progress bit in the MCES register. The instruction also sets or clears the
processor- or system-correctable error reporting enable bit in the MCES regis-
ter.
wrperfmon Performance monitoring function The wrperfmon instruction alerts any perfor-
mance monitoring software/hardware in the system to monitor the performance
of this process.
wrusp Write user stack pointer The wrusp instruction writes a value to the user stack
pointer while in kernel mode.
Table 10–2 : Privileged Digital UNIX PALcode Instruction Summary (Continued)
Mnemonic Operation and Description