Enter Privileged Code Instruction

epc

Operation Font Conventions

Format

epc B8


Description

This instruction increases the privilege level. The new privilege level is given by the TLB entry for the page containing this instruction. This instruction can be used to implement calls to higher-privileged routines without the overhead of an interruption.

Before increasing the privilege level, a check is performed. The PFS.ppl (previous privilege level is checked to ensure that it is not more privileged than the current privilege level. If this check fails, the instruction takes an Illegal Operation fault.

If the check succeeds, then the privilege is increased as follows:

Note that the ITLB is actually only read once, at instruction fetch. Information from the access rights and privilege level fields from the translation is then used in executing this instruction.

This instruction cannot be predicated.

Interruptions

 

 

 

 

 

 

 


For details, see Volume 3: Instruction Set Reference of the Intel(R) Itanium(R) Architecture Software Developer's Manual . For the latest updates on the instruction set information, go to the web site.