Intel ITANIUM ARCHITECTURE - SOFTWARE DEVELOPERS VOLUME 3 REV 2.3, Manual

Page: 887 / 1898

Volume 2, Part 2: Code Examples 2:639
Code Examples A
A.1 OS Boot Flow Sample Code
The sample code given below is a example of setting up operating system register state
to prepare the processor for running in virtual mode as described in
Section 13.1.2,
“Operating System Boot Steps” on page 2:625 .
// This code will perform the following steps:
//1.Initialize PSR with interrupt disabled (bit 13)
//2.Invalidate ALAT via invala instruction
//3.Invalidate register stack
//4.Set region registers rr[r0] - rr[r7] to RID=0, PS=8K, E=0.
//5.Disable the VHPT
//6.Initialize protection key registers
//7.Initialize SP
//8.Initialize BSP
//9.Enable register stack engine.
//10.Setup IVA
//11.Setup virtual->physical address translation
//12.Setup GP.
.file“start.s”
// globals
.global main
.type main, @function // C function we will return to
.global __GLOB_DATA_PTR // External pointer to Global Data area
.global IVT_BASE // External pointer to IVT_BASE
.text
// This is the entry point where primary boot loader
// passes control.
pstart::
mov psr.l = r0 // Initialize psr.l
;;
invala
// Invalidate ALAT
mov ar.rsc = r0 // Invalidate register stack
;;
loadrs
// Initialize Region Registers
mov r2 = (13 << 2) // 8K page size
mov r3 = r0
mov r4 = 61
;;
Loader_RRLoop:
shl r10 = r3, r4
;;
mov rr[r10] = r2
add r3 = 1, r3
;;
cmp4.geu p6, p7 = 8, r3