xref: /netbsd-current/sys/arch/sun3/sun3x/locore.s

/*	$NetBSD: locore.s,v 1.74 2024/01/14 22:34:54 thorpej Exp $	*/

/*
 * Copyright (c) 1988 University of Utah.
 * Copyright (c) 1980, 1990, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * the Systems Programming Group of the University of Utah Computer
 * Science Department.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *	from: Utah $Hdr: locore.s 1.66 92/12/22$
 *	@(#)locore.s	8.6 (Berkeley) 5/27/94
 */

#include "opt_compat_netbsd.h"
#include "opt_compat_sunos.h"
#include "opt_kgdb.h"
#include "opt_lockdebug.h"

#include "assym.h"
#include <machine/asm.h>
#include <machine/trap.h>

| Remember this is a fun project!

	.data
GLOBAL(mon_crp)
	.long	0,0

| This is for kvm_mkdb, and should be the address of the beginning
| of the kernel text segment (not necessarily the same as kernbase).
	.text
GLOBAL(kernel_text)

| This is the entry point, as well as the end of the temporary stack
| used during process switch (one 8K page ending at start)
ASGLOBAL(tmpstk)
ASGLOBAL(start)

| The first step, after disabling interrupts, is to map enough of the kernel
| into high virtual address space so that we can use position dependent code.
| This is a tricky task on the sun3x because the MMU is already enabled and
| the ROM monitor provides no indication of where the root MMU table is mapped.
| Therefore we must use one of the 68030's 'transparent translation' registers
| to define a range in the address space where the MMU translation is
| turned off.  Once this is complete we can modify the MMU table directly
| without the need for it to be mapped into virtual memory.
| All code must be position independent until otherwise noted, as the
| boot loader has loaded us into low memory but all the symbols in this
| code have been linked high.
	movw	#PSL_HIGHIPL,%sr	| no interrupts
	movl	#KERNBASE3X,%a5		| for vtop conversion
	lea	_C_LABEL(mon_crp),%a0	| where to store the CRP
	subl	%a5,%a0
	| Note: borrowing mon_crp for tt0 setup...
	movl	#0x3F8107,%a0@		| map the low 1GB v=p with the
	.long	0xf0100800		| transparent translation reg0
					| [ pmove a0@, tt0 ]
| In order to map the kernel into high memory we will copy the root table
| entry which maps the 16 megabytes of memory starting at 0x0 into the
| entry which maps the 16 megabytes starting at KERNBASE.
	pmove	%crp,%a0@		| Get monitor CPU root pointer
	movl	%a0@(4),%a1		| 2nd word is PA of level A table

	movl	%a1,%a0			| compute the descriptor address
	addl	#0x3e0,%a1		| for VA starting at KERNBASE
	movl	%a0@,%a1@		| copy descriptor type
	movl	%a0@(4),%a1@(4)		| copy physical address

| Kernel is now double mapped at zero and KERNBASE.
| Force a long jump to the relocated code (high VA).
	movl	#IC_CLEAR,%d0		| Flush the I-cache
	movc	%d0,%cacr
	jmp L_high_code:l		| long jump

L_high_code:
| We are now running in the correctly relocated kernel, so
| we are no longer restricted to position-independent code.
| It is handy to leave transparent translation enabled while
| for the low 1GB while _bootstrap() is doing its thing.

| Do bootstrap stuff needed before main() gets called.
| Our boot loader leaves a copy of the kernel's exec header
| just before the start of the kernel text segment, so the
| kernel can sanity-check the DDB symbols at [end...esym].
| Pass the struct exec at tmpstk-32 to _bootstrap().
| Also, make sure the initial frame pointer is zero so that
| the backtrace algorithm used by KGDB terminates nicely.
	lea	_ASM_LABEL(tmpstk)-32,%sp
	movl	#0,%a6
	jsr	_C_LABEL(_bootstrap)	| See locore2.c

| Now turn off the transparent translation of the low 1GB.
| (this also flushes the ATC)
	clrl	%sp@-
	.long	0xf0170800		| pmove	sp@,tt0
	addql	#4,%sp

| Now that _bootstrap() is done using the PROM functions,
| we can safely set the sfc/dfc to something != FC_CONTROL
	moveq	#FC_USERD,%d0		| make movs access "user data"
	movc	%d0,%sfc		| space for copyin/copyout
	movc	%d0,%dfc

| Setup process zero user/kernel stacks.
	lea	_C_LABEL(lwp0),%a0	| get lwp0
	movl	%a0@(L_PCB),%a1		| XXXuvm_lwp_getuarea
	lea	%a1@(USPACE-4),%sp	| set SSP to last word
	movl	#USRSTACK3X-4,%a2
	movl	%a2,%usp		| init user SP

| Note curpcb was already set in _bootstrap().
| Will do fpu initialization during autoconfig (see fpu.c)
| The interrupt vector table and stack are now ready.
| Interrupts will be enabled later, AFTER  autoconfiguration
| is finished, to avoid spurrious interrupts.

/*
 * Create a fake exception frame so that cpu_lwp_fork() can copy it.
 * main() nevers returns; we exit to user mode from a forked process
 * later on.
 */
	clrw	%sp@-			| tf_format,tf_vector
	clrl	%sp@-			| tf_pc (filled in later)
	movw	#PSL_USER,%sp@-		| tf_sr for user mode
	clrl	%sp@-			| tf_stackadj
	lea	%sp@(-64),%sp		| tf_regs[16]
	movl	%a1,%a0@(L_MD_REGS)	| lwp0.l_md.md_regs = trapframe
	jbsr	_C_LABEL(main)		| main(&trapframe)
	PANIC("main() returned")

| That is all the assembly startup code we need on the sun3x!
| The rest of this is like the hp300/locore.s where possible.

/*
 * Trap/interrupt vector routines
 */
#include <m68k/m68k/trap_subr.s>

GLOBAL(buserr)
	tstl	_C_LABEL(nofault)	| device probe?
	jeq	_C_LABEL(addrerr)	| no, handle as usual
	movl	_C_LABEL(nofault),%sp@-	| yes,
	jbsr	_C_LABEL(longjmp)	|  longjmp(nofault)
GLOBAL(addrerr)
	clrl	%sp@-			| stack adjust count
	moveml	#0xFFFF,%sp@-		| save user registers
	movl	%usp,%a0		| save the user SP
	movl	%a0,%sp@(FR_SP)		|   in the savearea
	lea	%sp@(FR_HW),%a1		| grab base of HW berr frame
	moveq	#0,%d0
	movw	%a1@(10),%d0		| grab SSW for fault processing
	btst	#12,%d0			| RB set?
	jeq	LbeX0			| no, test RC
	bset	#14,%d0			| yes, must set FB
	movw	%d0,%a1@(10)		| for hardware too
LbeX0:
	btst	#13,%d0			| RC set?
	jeq	LbeX1			| no, skip
	bset	#15,%d0			| yes, must set FC
	movw	%d0,%a1@(10)		| for hardware too
LbeX1:
	btst	#8,%d0			| data fault?
	jeq	Lbe0			| no, check for hard cases
	movl	%a1@(16),%d1		| fault address is as given in frame
	jra	Lbe10			| thats it
Lbe0:
	btst	#4,%a1@(6)		| long (type B) stack frame?
	jne	Lbe4			| yes, go handle
	movl	%a1@(2),%d1		| no, can use save PC
	btst	#14,%d0			| FB set?
	jeq	Lbe3			| no, try FC
	addql	#4,%d1			| yes, adjust address
	jra	Lbe10			| done
Lbe3:
	btst	#15,%d0			| FC set?
	jeq	Lbe10			| no, done
	addql	#2,%d1			| yes, adjust address
	jra	Lbe10			| done
Lbe4:
	movl	%a1@(36),%d1		| long format, use stage B address
	btst	#15,%d0			| FC set?
	jeq	Lbe10			| no, all done
	subql	#2,%d1			| yes, adjust address
Lbe10:
	movl	%d1,%sp@-		| push fault VA
	movl	%d0,%sp@-		| and padded SSW
	movw	%a1@(6),%d0		| get frame format/vector offset
	andw	#0x0FFF,%d0		| clear out frame format
	cmpw	#12,%d0			| address error vector?
	jeq	Lisaerr			| yes, go to it

/* MMU-specific code to determine reason for bus error. */
	movl	%d1,%a0			| fault address
	movl	%sp@,%d0		| function code from ssw
	btst	#8,%d0			| data fault?
	jne	Lbe10a
	movql	#1,%d0			| user program access FC
					| (we dont separate data/program)
	btst	#5,%a1@			| supervisor mode?
	jeq	Lbe10a			| if no, done
	movql	#5,%d0			| else supervisor program access
Lbe10a:
	ptestr	%d0,%a0@,#7		| do a table search
	pmove	%psr,%sp@		| save result
	movb	%sp@,%d1
	btst	#2,%d1			| invalid? (incl. limit viol and berr)
	jeq	Lmightnotbemerr		| no -> wp check
	btst	#7,%d1			| is it MMU table berr?
	jeq	Lismerr			| no, must be fast
	jra	Lisberr1		| real bus err needs not be fast
Lmightnotbemerr:
	btst	#3,%d1			| write protect bit set?
	jeq	Lisberr1		| no, must be bus error
	movl	%sp@,%d0		| ssw into low word of d0
	andw	#0xc0,%d0		| write protect is set on page:
	cmpw	#0x40,%d0		| was it read cycle?
	jeq	Lisberr1		| yes, was not WPE, must be bus err
/* End of MMU-specific bus error code. */

Lismerr:
	movl	#T_MMUFLT,%sp@-		| show that we are an MMU fault
	jra	_ASM_LABEL(faultstkadj)	| and deal with it
Lisaerr:
	movl	#T_ADDRERR,%sp@-	| mark address error
	jra	_ASM_LABEL(faultstkadj)	| and deal with it
Lisberr1:
	clrw	%sp@			| re-clear pad word
Lisberr:
	movl	#T_BUSERR,%sp@-		| mark bus error
	jra	_ASM_LABEL(faultstkadj)	| and deal with it

/*
 * FP exceptions.
 */
GLOBAL(fpfline)
	clrl	%sp@-			| stack adjust count
	moveml	#0xFFFF,%sp@-		| save registers
	moveq	#T_FPEMULI,%d0		| denote as FP emulation trap
	jra	_ASM_LABEL(fault)	| do it

GLOBAL(fpunsupp)
	clrl	%sp@-			| stack adjust count
	moveml	#0xFFFF,%sp@-		| save registers
	moveq	#T_FPEMULD,%d0		| denote as FP emulation trap
	jra	_ASM_LABEL(fault)	| do it

/*
 * Handles all other FP coprocessor exceptions.
 * Note that since some FP exceptions generate mid-instruction frames
 * and may cause signal delivery, we need to test for stack adjustment
 * after the trap call.
 */
GLOBAL(fpfault)
	clrl	%sp@-		| stack adjust count
	moveml	#0xFFFF,%sp@-	| save user registers
	movl	%usp,%a0	| and save
	movl	%a0,%sp@(FR_SP)	|   the user stack pointer
	clrl	%sp@-		| no VA arg
	movl	_C_LABEL(curpcb),%a0	| current pcb
	lea	%a0@(PCB_FPCTX),%a0 | address of FP savearea
	fsave	%a0@		| save state
	tstb	%a0@		| null state frame?
	jeq	Lfptnull	| yes, safe
	clrw	%d0		| no, need to tweak BIU
	movb	%a0@(1),%d0	| get frame size
	bset	#3,%a0@(0,%d0:w) | set exc_pend bit of BIU
Lfptnull:
	fmovem	%fpsr,%sp@-	| push fpsr as code argument
	frestore %a0@		| restore state
	movl	#T_FPERR,%sp@-	| push type arg
	jra	_ASM_LABEL(faultstkadj) | call trap and deal with stack cleanup

/*
 * Other exceptions only cause four and six word stack frame and require
 * no post-trap stack adjustment.
 */
GLOBAL(badtrap)
	clrl	%sp@-			| stack adjust count
	moveml	#0xFFFF,%sp@-		| save std frame regs
	jbsr	_C_LABEL(straytrap)	| report
	moveml	%sp@+,#0xFFFF		| restore regs
	addql	#4,%sp			| stack adjust count
	jra	_ASM_LABEL(rei)		| all done

/*
 * Trap 0 is for system calls
 */
GLOBAL(trap0)
	clrl	%sp@-			| stack adjust count
	moveml	#0xFFFF,%sp@-		| save user registers
	movl	%usp,%a0		| save the user SP
	movl	%a0,%sp@(FR_SP)		|   in the savearea
	movl	%d0,%sp@-		| push syscall number
	jbsr	_C_LABEL(syscall)	| handle it
	addql	#4,%sp			| pop syscall arg
	movl	%sp@(FR_SP),%a0		| grab and restore
	movl	%a0,%usp		|   user SP
	moveml	%sp@+,#0x7FFF		| restore most registers
	addql	#8,%sp			| pop SP and stack adjust
	jra	_ASM_LABEL(rei)		| all done

/*
 * Trap 12 is the entry point for the cachectl "syscall"
 *	cachectl(command, addr, length)
 * command in d0, addr in a1, length in d1
 */
GLOBAL(trap12)
	movl	_C_LABEL(curlwp),%a0
	movl	%a0@(L_PROC),%sp@-	| push curproc pointer
	movl	%d1,%sp@-		| push length
	movl	%a1,%sp@-		| push addr
	movl	%d0,%sp@-		| push command
	jbsr	_C_LABEL(cachectl1)	| do it
	lea	%sp@(16),%sp		| pop args
	jra	_ASM_LABEL(rei)		| all done

/*
 * Trace (single-step) trap.  Kernel-mode is special.
 * User mode traps are simply passed on to trap().
 */
GLOBAL(trace)
	clrl	%sp@-			| stack adjust count
	moveml	#0xFFFF,%sp@-
	moveq	#T_TRACE,%d0

	| Check PSW and see what happen.
	|   T=0 S=0	(should not happen)
	|   T=1 S=0	trace trap from user mode
	|   T=0 S=1	trace trap on a trap instruction
	|   T=1 S=1	trace trap from system mode (kernel breakpoint)

	movw	%sp@(FR_HW),%d1		| get PSW
	notw	%d1			| XXX no support for T0 on 680[234]0
	andw	#PSL_TS,%d1		| from system mode (T=1, S=1)?
	jeq	_ASM_LABEL(kbrkpt)	|  yes, kernel brkpt
	jra	_ASM_LABEL(fault)	| no, user-mode fault

/*
 * Trap 15 is used for:
 *	- GDB breakpoints (in user programs)
 *	- KGDB breakpoints (in the kernel)
 *	- trace traps for SUN binaries (not fully supported yet)
 * User mode traps are simply passed to trap().
 */
GLOBAL(trap15)
	clrl	%sp@-			| stack adjust count
	moveml	#0xFFFF,%sp@-
	moveq	#T_TRAP15,%d0
	btst	#5,%sp@(FR_HW)		| was supervisor mode?
	jne	_ASM_LABEL(kbrkpt)	|  yes, kernel brkpt
	jra	_ASM_LABEL(fault)	| no, user-mode fault

ASLOCAL(kbrkpt)
	| Kernel-mode breakpoint or trace trap. (%d0=trap_type)
	| Save the system sp rather than the user sp.
	movw	#PSL_HIGHIPL,%sr	| lock out interrupts
	lea	%sp@(FR_SIZE),%a6	| Save stack pointer
	movl	%a6,%sp@(FR_SP)		|  from before trap

	| If we are not on tmpstk switch to it.
	| (so debugger can change the stack pointer)
	movl	%a6,%d1
	cmpl	#_ASM_LABEL(tmpstk),%d1
	jls	Lbrkpt2 		| already on tmpstk
	| Copy frame to the temporary stack
	movl	%sp,%a0			| %a0=src
	lea	_ASM_LABEL(tmpstk)-96,%a1 | %a1=dst
	movl	%a1,%sp			| sp=new frame
	moveq	#FR_SIZE,%d1
Lbrkpt1:
	movl	%a0@+,%a1@+
	subql	#4,%d1
	bgt	Lbrkpt1

Lbrkpt2:
	| Call the trap handler for the kernel debugger.
	| Do not call trap() to handle it, so that we can
	| set breakpoints in trap() if we want.  We know
	| the trap type is either T_TRACE or T_BREAKPOINT.
	movl	%d0,%sp@-		| push trap type
	jbsr	_C_LABEL(trap_kdebug)
	addql	#4,%sp			| pop args

	| The stack pointer may have been modified, or
	| data below it modified (by kgdb push call),
	| so push the hardware frame at the current sp
	| before restoring registers and returning.
	movl	%sp@(FR_SP),%a0		| modified sp
	lea	%sp@(FR_SIZE),%a1	| end of our frame
	movl	%a1@-,%a0@-		| copy 2 longs with
	movl	%a1@-,%a0@-		| ... predecrement
	movl	%a0,%sp@(FR_SP)		| sp = h/w frame
	moveml	%sp@+,#0x7FFF		| restore all but sp
	movl	%sp@,%sp		| ... and sp
	rte				| all done

/* Use common m68k sigreturn */
#include <m68k/m68k/sigreturn.s>

/*
 * Interrupt handlers.  Most are auto-vectored,
 * and hard-wired the same way on all sun3 models.
 * Format in the stack is:
 *   %d0,%d1,%a0,%a1, sr, pc, vo
 */

/* clock: see clock.c */
#ifdef __ELF__
	.align	4
#else
	.align	2
#endif
GLOBAL(_isr_clock)
	INTERRUPT_SAVEREG
	jbsr	_C_LABEL(clock_intr)
	INTERRUPT_RESTOREREG
	jra	_ASM_LABEL(rei)

/* interrupt counters (needed by vmstat) */
GLOBAL(intrnames)
	.asciz	"spur"	| 0
	.asciz	"lev1"	| 1
	.asciz	"lev2"	| 2
	.asciz	"lev3"	| 3
	.asciz	"lev4"	| 4
	.asciz	"clock"	| 5
	.asciz	"lev6"	| 6
	.asciz	"nmi"	| 7
GLOBAL(eintrnames)

	.data
	.even
GLOBAL(intrcnt)
	.long	0,0,0,0,0,0,0,0
GLOBAL(eintrcnt)
	.text

/*
 * Emulation of VAX REI instruction.
 *
 * This code is (mostly) un-altered from the hp300 code,
 * except that sun machines do not need a simulated SIR
 * because they have a real software interrupt register.
 *
 * This code deals with checking for and servicing ASTs
 * (profiling, scheduling) and software interrupts (network, softclock).
 * We check for ASTs first, just like the VAX.  To avoid excess overhead
 * the T_ASTFLT handling code will also check for software interrupts so we
 * do not have to do it here.  After identifying that we need an AST we
 * drop the IPL to allow device interrupts.
 *
 * This code is complicated by the fact that sendsig may have been called
 * necessitating a stack cleanup.
 */

ASGLOBAL(rei)
#ifdef	DIAGNOSTIC
	tstl	_C_LABEL(panicstr)	| have we panicked?
	jne	Ldorte			| yes, do not make matters worse
#endif
	tstl	_C_LABEL(astpending)	| AST pending?
	jeq	Ldorte			| no, done
Lrei1:
	btst	#5,%sp@			| yes, are we returning to user mode?
	jne	Ldorte			| no, done
	movw	#PSL_LOWIPL,%sr		| lower SPL
	clrl	%sp@-			| stack adjust
	moveml	#0xFFFF,%sp@-		| save all registers
	movl	%usp,%a1		| including
	movl	%a1,%sp@(FR_SP)		|    the users SP
	clrl	%sp@-			| VA == none
	clrl	%sp@-			| code == none
	movl	#T_ASTFLT,%sp@-		| type == async system trap
	pea	%sp@(12)		| fp == address of trap frame
	jbsr	_C_LABEL(trap)		| go handle it
	lea	%sp@(16),%sp		| pop value args
	movl	%sp@(FR_SP),%a0		| restore user SP
	movl	%a0,%usp		|   from save area
	movw	%sp@(FR_ADJ),%d0	| need to adjust stack?
	jne	Laststkadj		| yes, go to it
	moveml	%sp@+,#0x7FFF		| no, restore most user regs
	addql	#8,%sp			| toss SP and stack adjust
	rte				| and do real RTE
Laststkadj:
	lea	%sp@(FR_HW),%a1		| pointer to HW frame
	addql	#8,%a1			| source pointer
	movl	%a1,%a0			| source
	addw	%d0,%a0			|  + hole size = dest pointer
	movl	%a1@-,%a0@-		| copy
	movl	%a1@-,%a0@-		|  8 bytes
	movl	%a0,%sp@(FR_SP)		| new SSP
	moveml	%sp@+,#0x7FFF		| restore user registers
	movl	%sp@,%sp		| and our SP
Ldorte:
	rte				| real return

/*
 * Initialization is at the beginning of this file, because the
 * kernel entry point needs to be at zero for compatibility with
 * the Sun boot loader.  This works on Sun machines because the
 * interrupt vector table for reset is NOT at address zero.
 * (The MMU has a "boot" bit that forces access to the PROM)
 */

/*
 * Use common m68k sigcode.
 */
#include <m68k/m68k/sigcode.s>
#ifdef COMPAT_SUNOS
#include <m68k/m68k/sunos_sigcode.s>
#endif

	.text

/*
 * Primitives
 */

/*
 * Use common m68k support routines.
 */
#include <m68k/m68k/support.s>

/*
 * Use common m68k process/lwp switch and context save subroutines.
 */
#define FPCOPROC	/* XXX: Temp. Reqd. */
#include <m68k/m68k/switch_subr.s>


/* suline() */

#ifdef DEBUG
	.data
ASGLOBAL(fulltflush)
	.long	0
ASGLOBAL(fullcflush)
	.long	0
	.text
#endif

ENTRY(ecacheon)
	rts

ENTRY(ecacheoff)
	rts

/*
 * Load a new CPU Root Pointer (CRP) into the MMU.
 *	void	loadcrp(struct mmu_rootptr *);
 */
ENTRY(loadcrp)
	movl	%sp@(4),%a0		| arg1: &CRP
	movl	#CACHE_CLR,%d0
	movc	%d0,%cacr		| invalidate cache(s)
	pflusha				| flush entire TLB
	pmove	%a0@,%crp		| load new user root pointer
	rts

ENTRY(getcrp)
	movl	%sp@(4),%a0		| arg1: &crp
	pmove	%crp,%a0@		| *crpp = %crp
	rts

/*
 * Get the physical address of the PTE for a given VA.
 */
ENTRY(ptest_addr)
	movl	%sp@(4),%a1		| VA
	ptestr	#5,%a1@,#7,%a0		| %a0 = addr of PTE
	movl	%a0,%d0			| Result in %d0 (not a pointer return)
	rts

/*
 * _delay(unsigned N)
 * Delay for at least (N/256) microseconds.
 * This routine depends on the variable:  delay_divisor
 * which should be set based on the CPU clock rate.
 * XXX: Currently this is set based on the CPU model,
 * XXX: but this should be determined at run time...
 */
GLOBAL(_delay)
	| %d0 = arg = (usecs << 8)
	movl	%sp@(4),%d0
	| %d1 = delay_divisor;
	movl	_C_LABEL(delay_divisor),%d1
	jra	L_delay			/* Jump into the loop! */

	/*
	 * Align the branch target of the loop to a half-line (8-byte)
	 * boundary to minimize cache effects.  This guarantees both
	 * that there will be no prefetch stalls due to cache line burst
	 * operations and that the loop will run from a single cache
	 * half-line.
	 */
#ifdef __ELF__
	.align	8
#else
	.align	3
#endif
L_delay:
	subl	%d1,%d0
	jgt	L_delay
	rts

| Define some addresses, mostly so DDB can print useful info.
| Not using _C_LABEL() here because these symbols are never
| referenced by any C code, and if the leading underscore
| ever goes away, these lines turn into syntax errors...
	.set	_KERNBASE3X,KERNBASE3X
	.set	_MONSTART,SUN3X_MONSTART
	.set	_PROM_BASE,SUN3X_PROM_BASE
	.set	_MONEND,SUN3X_MONEND

|The end!