art@ACC.ARPA (06/29/87)
>It's my understanding that ANYONE can issue a CHMK instruction successfully. >(not to be confused with a successful call to the similar system service...) >Exactly what is the difference in the two ? What actually requires the >CHMKNL privilege ? Indeed any user can execute a CHMK instruction, and often does in the course of performing a system call. The CHMK instruction traps to the CMKRNL handler, with the CPU executing in KERNEL MODE. The CMKRNL trap handler then determines what the user wishes to do. Generally, the user is executing trusted kernel code which is responsible for checking user priviledges as appropriate for the operation being performed. The SYS$CMKRNL system call is used by a user to get control back to arbitrary user code, with the CPU in KERNEL MODE. This operation requires the user to have the CMKRNL priviledge (with which he can do just about anything he wishes). Art@acc.arpa ------