path: root/usr/src/uts/i86pc/ml/locore.s

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

/*
 * Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*	Copyright (c) 1990, 1991 UNIX System Laboratories, Inc.	*/
/*	Copyright (c) 1984, 1986, 1987, 1988, 1989, 1990 AT&T	*/
/*	  All Rights Reserved					*/

/*	Copyright (c) 1987, 1988 Microsoft Corporation		*/
/*	  All Rights Reserved					*/

#pragma ident	"%Z%%M%	%I%	%E% SMI"

#include <sys/asm_linkage.h>
#include <sys/asm_misc.h>
#include <sys/regset.h>
#include <sys/privregs.h>
#include <sys/psw.h>
#include <sys/reboot.h>
#include <sys/x86_archext.h>
#include <sys/machparam.h>

#if defined(__lint)

#include <sys/types.h>
#include <sys/thread.h>
#include <sys/systm.h>
#include <sys/lgrp.h>
#include <sys/regset.h>
#include <sys/link.h>
#include <sys/bootconf.h>
#include <sys/bootsvcs.h>

#else	/* __lint */

#include <sys/segments.h>
#include <sys/pcb.h>
#include <sys/trap.h>
#include <sys/ftrace.h>
#include <sys/traptrace.h>
#include <sys/clock.h>
#include <sys/cmn_err.h>
#include <sys/pit.h>
#include <sys/panic.h>

#if defined(__xpv)
#include <sys/hypervisor.h>
#endif

#include "assym.h"

/*
 * Our assumptions:
 *	- We are running in protected-paged mode.
 *	- Interrupts are disabled.
 *	- The GDT and IDT are the callers; we need our copies.
 *	- The kernel's text, initialized data and bss are mapped.
 *
 * Our actions:
 *	- Save arguments
 *	- Initialize our stack pointer to the thread 0 stack (t0stack)
 *	  and leave room for a phony "struct regs".
 *	- Our GDT and IDT need to get munged.
 *	- Since we are using the boot's GDT descriptors, we need
 *	  to copy them into our GDT before we switch to ours.
 *	- We start using our GDT by loading correct values in the
 *	  selector registers (cs=KCS_SEL, ds=es=ss=KDS_SEL, fs=KFS_SEL,
 *	  gs=KGS_SEL).
 *	- The default LDT entry for syscall is set.
 *	- We load the default LDT into the hardware LDT register.
 *	- We load the default TSS into the hardware task register.
 *	- Check for cpu type, i.e. 486 vs. P5 vs. P6 etc.
 *	- mlsetup(%esp) gets called.
 *	- We change our appearance to look like the real thread 0.
 *	  (NOTE: making ourselves to be a real thread may be a noop)
 *	- main() gets called.  (NOTE: main() never returns).
 *
 * NOW, the real code!
 */
	/*
	 * The very first thing in the kernel's text segment must be a jump
	 * to the os/fakebop.c startup code.
	 */
	.text
	jmp     _start

	/*
	 * Globals:
	 */
	.globl	_locore_start
	.globl	mlsetup
	.globl	main
	.globl	panic
	.globl	t0stack
	.globl	t0
	.globl	sysp
	.globl	edata

	/*
	 * call back into boot - sysp (bootsvcs.h) and bootops (bootconf.h)
	 */
	.globl	bootops
	.globl	bootopsp

	/*
	 * NOTE: t0stack should be the first thing in the data section so that
	 * if it ever overflows, it will fault on the last kernel text page.
	 */
	.data
	.comm	t0stack, DEFAULTSTKSZ, 32
	.comm	t0, 4094, 32

#ifdef TRAPTRACE
	/*
	 * trap_trace_ctl must agree with the structure definition in
	 * <sys/traptrace.h>
	 */	
	DGDEF3(trap_trace_bufsize, CLONGSIZE, CLONGSIZE)
	.NWORD	TRAP_TSIZE

	DGDEF3(trap_trace_freeze, 4, 4)
	.long	0

	DGDEF3(trap_trace_off, 4, 4)
	.long	0

	DGDEF3(trap_trace_ctl, _MUL(4, CLONGSIZE), 16)
	.NWORD	trap_tr0		/* next record */
	.NWORD	trap_tr0		/* first record */
	.NWORD	trap_tr0 + TRAP_TSIZE	/* limit */
	.NWORD	0			/* pad */

	/*
	 * Enough padding for 31 more CPUs (no .skip on x86 -- grrrr).
	 */
	.NWORD	0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0
	.NWORD	0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0
	.NWORD	0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0
	.NWORD	0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0
	.NWORD	0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0
	.NWORD	0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0
	.NWORD	0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0
	.NWORD	0,0,0,0, 0,0,0,0, 0,0,0,0

#if defined(__amd64)

#if NCPU != 64
#error "NCPU != 64, Expand padding for trap_trace_ctl"
#endif

	/*
	 * Enough padding for 32 more CPUs (no .skip on x86 -- grrrr).
	 */
	.NWORD	0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0
	.NWORD	0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0
	.NWORD	0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0
	.NWORD	0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0
	.NWORD	0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0
	.NWORD	0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0
	.NWORD	0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0
	.NWORD	0,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0,0

#else	/* __amd64 */

#if NCPU != 32
#error "NCPU != 32, Expand padding for trap_trace_ctl"
#endif

#endif	/* __amd64 */

	/*
	 * CPU 0's preallocated TRAPTRACE buffer.
	 */
	.globl	trap_tr0
	.comm	trap_tr0, TRAP_TSIZE

	/*
	 * A dummy TRAPTRACE entry to use after death.
	 */
	.globl	trap_trace_postmort
	.comm	trap_trace_postmort, TRAP_ENT_SIZE
#endif	/* TRAPTRACE */

#endif	/* __lint */


#if defined(__amd64)

#if defined(__lint)

/* ARGSUSED */
void
_locore_start(struct boot_syscalls *sysp, ulong_t rsi, struct bootops *bop)
{}

#else	/* __lint */

	/*
	 * kobj_init() vectors us back to here with (note) a slightly different
	 * set of arguments than _start is given (see lint prototypes above).
	 *
	 * XXX	Make this less vile, please.
	 */
	ENTRY_NP(_locore_start)

	/*
	 * %rdi = boot services (should die someday)
	 * %rdx = bootops
	 * end
	 */	

	leaq	edata(%rip), %rbp	/* reference edata for ksyms */
	movq	$0, (%rbp)		/* limit stack back trace */

	/*
	 * Initialize our stack pointer to the thread 0 stack (t0stack)
	 * and leave room for a "struct regs" for lwp0.  Note that the
	 * stack doesn't actually align to a 16-byte boundary until just
	 * before we call mlsetup because we want to use %rsp to point at
	 * our regs structure.
	 */
	leaq	t0stack(%rip), %rsp
	addq	$_CONST(DEFAULTSTKSZ - REGSIZE), %rsp
#if (REGSIZE & 15) == 0
	subq	$8, %rsp
#endif
	/*
	 * Save call back for special x86 boot services vector
	 */	
	movq	%rdi, sysp(%rip)

	movq	%rdx, bootops(%rip)		/* save bootops */
	movq	$bootops, bootopsp(%rip)

	/*
	 * Save arguments and flags, if only for debugging ..
	 */
	movq	%rdi, REGOFF_RDI(%rsp)
	movq	%rsi, REGOFF_RSI(%rsp)
	movq	%rdx, REGOFF_RDX(%rsp)
	movq	%rcx, REGOFF_RCX(%rsp)
	movq	%r8, REGOFF_R8(%rsp)
	movq	%r9, REGOFF_R9(%rsp)
	pushf
	popq	%r11
	movq	%r11, REGOFF_RFL(%rsp)

#if !defined(__xpv)
	/*
	 * Enable write protect and alignment check faults.
	 */
	movq	%cr0, %rax
	orq	$_CONST(CR0_WP|CR0_AM), %rax
	andq	$_BITNOT(CR0_WT|CR0_CE), %rax
	movq	%rax, %cr0
#endif	/* __xpv */

	/*
	 * (We just assert this works by virtue of being here) 
	 */
	orl	$X86_CPUID, x86_feature(%rip)

	/*
	 * mlsetup() gets called with a struct regs as argument, while
	 * main takes no args and should never return.
	 */
	xorl	%ebp, %ebp
	movq	%rsp, %rdi
	pushq	%rbp
	/* (stack pointer now aligned on 16-byte boundary right here) */
	movq	%rsp, %rbp
	call	mlsetup
	call	main
	/* NOTREACHED */
	leaq	__return_from_main(%rip), %rdi
	xorl	%eax, %eax
	call	panic
	SET_SIZE(_locore_start)

#endif	/* __amd64 */
#endif	/* __lint */

#if !defined(__lint)

__return_from_main:
	.string	"main() returned"
__unsupported_cpu:
	.string	"486 style cpu detected - no longer supported!"

#endif	/* !__lint */

#if !defined(__amd64)

#if defined(__lint)

/* ARGSUSED */
void
_locore_start(struct boot_syscalls *sysp, struct bootops *bop)
{}

#else	/* __lint */

	/*
	 * kobj_init() vectors us back to here with (note) a slightly different
	 * set of arguments than _start is given (see lint prototypes above).
	 *
	 * XXX	Make this less vile, please.
	 */
	ENTRY_NP(_locore_start)

	/*
	 *	%ecx = boot services (should die someday)
	 *	%ebx = bootops
	 */	
	mov	$edata, %ebp		/ edata needs to be defined for ksyms
	movl	$0, (%ebp)		/ limit stack back trace

	/*
	 * Initialize our stack pointer to the thread 0 stack (t0stack)
	 * and leave room for a phony "struct regs".
	 */
	movl	$t0stack + DEFAULTSTKSZ - REGSIZE, %esp

	/*
	 * Save call back for special x86 boot services vector
	 */
	mov	%ecx, sysp		/ save call back for boot services

 	mov	%ebx, bootops		/ save bootops
	movl	$bootops, bootopsp


	/*
	 * Save all registers and flags
	 */
	pushal	
	pushfl

#if !defined(__xpv)
	/*
	 * Override bios settings and enable write protect and
	 * alignment check faults.
	 */
	movl	%cr0, %eax

	/*
	 * enable WP for detecting faults, and enable alignment checking.
	 */
	orl	$_CONST(CR0_WP|CR0_AM), %eax
	andl	$_BITNOT(CR0_WT|CR0_CE), %eax
	movl	%eax, %cr0		/ set the cr0 register correctly and
					/ override the BIOS setup

	/*
	 * If bit 21 of eflags can be flipped, then cpuid is present
	 * and enabled.
	 */
	pushfl
	popl	%ecx
	movl	%ecx, %eax
	xorl	$PS_ID, %eax		/ try complemented bit
	pushl	%eax
	popfl
	pushfl
	popl    %eax
	cmpl	%eax, %ecx
	jne	have_cpuid

	/*
	 * cpuid may be disabled on Cyrix, try to detect Cyrix by the 5/2 test
	 * div does not modify the cc flags on Cyrix, even though this may
	 * also be true for other vendors, this is generally true only for
	 * newer models from those vendors that support and do not disable
	 * cpuid (usually because cpuid cannot be disabled)
	 */

	/*
	 * clear cc flags
	 */
	xorb	%ah, %ah
	sahf

	/*
	 * perform 5/2 test
	 */
	movw	$5, %ax
	movb	$2, %bl
	divb	%bl

	lahf
	cmpb	$2, %ah
	jne	cpu_486

	/*
	 * div did not modify the cc flags, chances are the vendor is Cyrix
	 * assume the vendor is Cyrix and use the CCR's to enable cpuid
	 */
	.set	CYRIX_CRI, 0x22		/ CR Index Register
	.set	CYRIX_CRD, 0x23		/ CR Data Register

	.set	CYRIX_CCR3, 0xc3	/ Config Control Reg 3
	.set	CYRIX_CCR4, 0xe8	/ Config Control Reg 4
	.set	CYRIX_DIR0, 0xfe	/ Device Identification Reg 0
	.set	CYRIX_DIR1, 0xff	/ Device Identification Reg 1

	/*
	 * even if the cpu vendor is Cyrix and the motherboard/chipset
	 * vendor decided to ignore lines A1-A4 for I/O addresses, I/O port
	 * 0x21 corresponds with 0x23 and since 0x22 is still untouched,
	 * the reads and writes of 0x21 are guaranteed to be off-chip of
	 * the cpu
	 */

	/*
	 * enable read of ISR at I/O port 0x20
	 */
	movb	$0xb, %al
	outb	$MCMD_PORT

	/*
	 * read IMR and store in %bl
	 */
	inb	$MIMR_PORT
	movb	%al, %bl

	/*
	 * mask out all interrupts so that ISR will not change
	 */
	movb	$0xff, %al
	outb	$MIMR_PORT

	/*
	 * reads of I/O port 0x22 on Cyrix are always directed off-chip
	 * make use of I/O pull-up to test for an unknown device on 0x22
	 */
	inb	$CYRIX_CRI
	cmpb	$0xff, %al
	je	port_22_free

	/*
	 * motherboard/chipset vendor may be ignoring line A1 of I/O address
	 */
	movb	%al, %cl

	/*
	 * if the ISR and the value read from 0x22 do not match then we have
	 * detected some unknown device, probably a chipset, at 0x22
	 */
	inb	$MCMD_PORT
	cmpb	%al, %cl
	jne	restore_IMR

port_22_free:
	/*
	 * now test to see if some unknown device is using I/O port 0x23
	 *
	 * read the external I/O port at 0x23
	 */
	inb	$CYRIX_CRD

	/*
	 * Test for pull-up at 0x23 or if I/O address line A1 is being ignored.
	 * IMR is 0xff so both tests are performed simultaneously.
	 */
	cmpb	$0xff, %al
	jne	restore_IMR

	/*
	 * We are a Cyrix part. In case we are some model of Cx486 or a Cx586,
	 * record the type and fix it later if not.
	 */
	movl	$X86_VENDOR_Cyrix, x86_vendor
	movl	$X86_TYPE_CYRIX_486, x86_type

	/*
	 * Try to read CCR3. All Cyrix cpu's which support cpuid have CCR3.
	 *
	 * load CCR3 index into CCR index register
	 */

	movb	$CYRIX_CCR3, %al
	outb	$CYRIX_CRI

	/*
	 * If we are not a Cyrix cpu, then we have performed an external I/O
	 * cycle. If the CCR index was not valid for this Cyrix model, we may
	 * have performed an external I/O cycle as well. In these cases and
	 * if the motherboard/chipset vendor ignores I/O address line A1,
	 * then the PIC will have IRQ3 set at the lowest priority as a side	
	 * effect of the above outb. We are reasonalbly confident that there
	 * is not an unknown device on I/O port 0x22, so there should have been
	 * no unpredictable side-effect of the above outb.
	 */

	/*
	 * read CCR3
	 */
	inb	$CYRIX_CRD

	/*
	 * If we are not a Cyrix cpu the inb above produced an external I/O
	 * cycle. If we are a Cyrix model that does not support CCR3 wex
	 * produced an external I/O cycle. In all known Cyrix models 6x86 and
	 * above, bit 3 of CCR3 is reserved and cannot be set to 1. In all
	 * Cyrix models prior to the 6x86 that supported CCR3, bits 4-7 are
	 * reserved as well. It is highly unlikely that CCR3 contains the value
	 * 0xff. We test to see if I/O port 0x23 is pull-up or the IMR and
	 * deduce we are not a Cyrix with support for cpuid if so.
	 */
	cmpb	$0xff, %al
	je	restore_PIC

	/*
	 * There exist 486 ISA Cyrix chips that support CCR3 but do not support
	 * DIR0 and DIR1. If we try to read DIR0, we may generate external I/O
	 * cycles, the exact behavior is model specific and undocumented.
	 * Unfortunately these external I/O cycles may confuse some PIC's beyond
	 * recovery. Fortunatetly we can use the following undocumented trick:
	 * if bit 4 of CCR3 can be toggled, then DIR0 and DIR1 are supported.
	 * Pleasantly MAPEN contains bit 4 of CCR3, so this trick is guaranteed
	 * to work on all Cyrix cpu's which support cpuid.
	 */
	movb	%al, %dl
	xorb	$0x10, %dl
	movb	%al, %cl

	/*
	 * write back CRR3 with toggled bit 4 to CCR3
	 */
	movb	$CYRIX_CCR3, %al
	outb	$CYRIX_CRI

	movb	%dl, %al
	outb	$CYRIX_CRD

	/*
	 * read CCR3
	 */
	movb	$CYRIX_CCR3, %al
	outb	$CYRIX_CRI
	inb	$CYRIX_CRD
	movb	%al, %dl

	/*
	 * restore CCR3
	 */
	movb	$CYRIX_CCR3, %al
	outb	$CYRIX_CRI

	movb	%cl, %al
	outb	$CYRIX_CRD

	/*
	 * if bit 4 was not toggled DIR0 and DIR1 are not supported in which
	 * case we do not have cpuid anyway
	 */
	andb	$0x10, %al
	andb	$0x10, %dl
	cmpb	%al, %dl
	je	restore_PIC

	/*
	 * read DIR0
	 */
	movb	$CYRIX_DIR0, %al
	outb	$CYRIX_CRI
	inb	$CYRIX_CRD

	/*
	 * test for pull-up
	 */
	cmpb	$0xff, %al
	je	restore_PIC

	/*
	 * Values of 0x20-0x27 in DIR0 are currently reserved by Cyrix for
	 * future use. If Cyrix ever produces a cpu that supports cpuid with
	 * these ids, the following test will have to change. For now we remain
	 * pessimistic since the formats of the CRR's may be different then.
	 *
	 * test for at least a 6x86, to see if we support both MAPEN and CPUID
	 */
	cmpb	$0x30, %al
	jb	restore_IMR

	/*
	 * enable MAPEN
	 */
	movb	$CYRIX_CCR3, %al
	outb	$CYRIX_CRI

	andb	$0xf, %cl
	movb	%cl, %al
	orb	$0x10, %al
	outb	$CYRIX_CRD

	/*
	 * select CCR4
	 */
	movb	$CYRIX_CCR4, %al
	outb	$CYRIX_CRI

	/*
	 * read CCR4
	 */
	inb	$CYRIX_CRD

	/*
	 * enable cpuid
	 */
	orb	$0x80, %al
	movb	%al, %dl

	/*
	 * select CCR4
	 */
	movb	$CYRIX_CCR4, %al
	outb	$CYRIX_CRI

	/*
	 * write CCR4
	 */
	movb	%dl, %al
	outb	$CYRIX_CRD

	/*
	 * select CCR3
	 */
	movb	$CYRIX_CCR3, %al
	outb	$CYRIX_CRI

	/*
	 * disable MAPEN and write CCR3
	 */
	movb	%cl, %al
	outb	$CYRIX_CRD

	/*
	 * restore IMR
	 */
	movb	%bl, %al
	outb	$MIMR_PORT

	/*
	 * test to see if cpuid available
	 */
	pushfl
	popl	%ecx
	movl	%ecx, %eax
	xorl	$PS_ID, %eax		/ try complemented bit
	pushl	%eax
	popfl
	pushfl
	popl    %eax
	cmpl	%eax, %ecx
	jne	have_cpuid
	jmp	cpu_486

restore_PIC:
	/*
	 * In case the motherboard/chipset vendor is ignoring line A1 of the
	 * I/O address, we set the PIC priorities to sane values.
	 */
	movb	$0xc7, %al	/ irq 7 lowest priority
	outb	$MCMD_PORT

restore_IMR:
	movb	%bl, %al
	outb	$MIMR_PORT
	jmp	cpu_486

have_cpuid:
	/*
	 * cpuid instruction present
	 */
	orl	$X86_CPUID, x86_feature
	movl	$0, %eax
	cpuid

	movl	%ebx, cpu_vendor
	movl	%edx, cpu_vendor+4
	movl	%ecx, cpu_vendor+8

	/*
	 * early cyrix cpus are somewhat strange and need to be
	 * probed in curious ways to determine their identity
	 */

	leal	cpu_vendor, %esi
	leal	CyrixInstead, %edi
	movl	$12, %ecx
	repz
	  cmpsb
	je	vendor_is_cyrix

	/ let mlsetup()/cpuid_pass1() handle everything else in C

	jmp	cpu_done

is486:
	/*
	 * test to see if a useful cpuid
	 */
	testl	%eax, %eax
	jz	isa486

	movl	$1, %eax
	cpuid

	movl	%eax, %ebx
	andl	$0xF00, %ebx
	cmpl	$0x400, %ebx
	je	isa486

	rep;	ret	/* use 2 byte return instruction */
			/* AMD Software Optimization Guide - Section 6.2 */
isa486:
	/*
	 * lose the return address
	 */
	popl	%eax
	jmp	cpu_486

vendor_is_cyrix:
	call	is486

	/*
	 * Processor signature and feature flags for Cyrix are insane.
	 * BIOS can play with semi-documented registers, so cpuid must be used
	 * cautiously. Since we are Cyrix that has cpuid, we have DIR0 and DIR1
	 * Keep the family in %ebx and feature flags in %edx until not needed
	 */

	/*
	 * read DIR0
	 */
	movb	$CYRIX_DIR0, %al
	outb	$CYRIX_CRI
	inb	$CYRIX_CRD

	/*
	 * First we handle the cases where we are a 6x86 or 6x86L.
	 * The 6x86 is basically a 486, the only reliable bit in the
	 * feature flags is for FPU. The 6x86L is better, unfortunately
	 * there is no really good way to distinguish between these two
	 * cpu's. We are pessimistic and when in doubt assume 6x86.
	 */

	cmpb	$0x40, %al
	jae	maybeGX

	/*
	 * We are an M1, either a 6x86 or 6x86L.
	 */
	cmpb	$0x30, %al
	je	maybe6x86L
	cmpb	$0x31, %al
	je	maybe6x86L
	cmpb	$0x34, %al
	je	maybe6x86L
	cmpb	$0x35, %al
	je	maybe6x86L

	/*
	 * although it is possible that we are a 6x86L, the cpu and
	 * documentation are so buggy, we just do not care.
	 */
	jmp	likely6x86

maybe6x86L:
	/*
	 *  read DIR1
	 */
	movb	$CYRIX_DIR1, %al
	outb	$CYRIX_CRI
	inb	$CYRIX_CRD
	cmpb	$0x22, %al
	jb	likely6x86

	/*
	 * We are a 6x86L, or at least a 6x86 with honest cpuid feature flags
	 */
	movl	$X86_TYPE_CYRIX_6x86L, x86_type
	jmp	coma_bug

likely6x86:
	/*
	 * We are likely a 6x86, or a 6x86L without a way of knowing
	 *
	 * The 6x86 has NO Pentium or Pentium Pro compatible features even
	 * though it claims to be a Pentium Pro compatible!
	 *
	 * The 6x86 core used in the 6x86 may have most of the Pentium system
	 * registers and largely conform to the Pentium System Programming
	 * Reference. Documentation on these parts is long gone. Treat it as
	 * a crippled Pentium and hope for the best.
	 */

	movl	$X86_TYPE_CYRIX_6x86, x86_type
	jmp	coma_bug

maybeGX:
	/*
	 * Now we check whether we are a MediaGX or GXm. We have particular
	 * reason for concern here. Even though most of the GXm's
	 * report having TSC in the cpuid feature flags, the TSC may be
	 * horribly broken. What is worse, is that MediaGX's are basically
	 * 486's while the good GXm's are more like Pentium Pro's!
	 */

	cmpb	$0x50, %al
	jae	maybeM2

	/*
	 * We are either a MediaGX (sometimes called a Gx86) or GXm
	 */

	cmpb	$41, %al
	je	maybeMediaGX

	cmpb	$44, %al
	jb	maybeGXm

	cmpb	$47, %al
	jbe	maybeMediaGX

	/*
	 * We do not honestly know what we are, so assume a MediaGX
	 */
	jmp	media_gx

maybeGXm:
	/*
	 * It is still possible we are either a MediaGX or GXm, trust cpuid
	 * family should be 5 on a GXm
	 */
	cmpl	$0x500, %ebx
	je	GXm

	/*
	 * BIOS/Cyrix might set family to 6 on a GXm
	 */
	cmpl	$0x600, %ebx
	jne	media_gx

GXm:
	movl	$X86_TYPE_CYRIX_GXm, x86_type
	jmp	cpu_done

maybeMediaGX:
	/*
	 * read DIR1
	 */
	movb	$CYRIX_DIR1, %al
	outb	$CYRIX_CRI
	inb	$CYRIX_CRD

	cmpb	$0x30, %al
	jae	maybeGXm

	/*
	 * we are a MediaGX for which we do not trust cpuid
	 */
media_gx:
	movl	$X86_TYPE_CYRIX_MediaGX, x86_type
	jmp	cpu_486

maybeM2:
	/*
	 * Now we check whether we are a 6x86MX or MII. These cpu's are
	 * virtually identical, but we care because for the 6x86MX, we
	 * must work around the coma bug. Also for 6x86MX prior to revision
	 * 1.4, the TSC may have serious bugs.
	 */

	cmpb	$0x60, %al
	jae	maybeM3

	/*
	 * family should be 6, but BIOS/Cyrix might set it to 5
	 */
	cmpl	$0x600, %ebx
	ja	cpu_486

	/*
	 *  read DIR1
	 */
	movb	$CYRIX_DIR1, %al
	outb	$CYRIX_CRI
	inb	$CYRIX_CRD

	cmpb	$0x8, %al
	jb	cyrix6x86MX
	cmpb	$0x80, %al
	jb	MII

cyrix6x86MX:
	/*
	 * It is altogether unclear how the revision stamped on the cpu
	 * maps to the values in DIR0 and DIR1. Just assume TSC is broken.
	 */
	movl	$X86_TYPE_CYRIX_6x86MX, x86_type
	jmp	coma_bug

MII:
	movl	$X86_TYPE_CYRIX_MII, x86_type
likeMII:
	jmp	cpu_done

maybeM3:
	/*
	 * We are some chip that we cannot identify yet, an MIII perhaps.
	 * We will be optimistic and hope that the chip is much like an MII,
	 * and that cpuid is sane. Cyrix seemed to have gotten it right in
	 * time for the MII, we can only hope it stayed that way.
	 * Maybe the BIOS or Cyrix is trying to hint at something
	 */
	cmpl	$0x500, %ebx
	je	GXm

	cmpb	$0x80, %al
	jae	likelyM3

	/*
	 * Just test for the features Cyrix is known for
	 */

	jmp	MII

likelyM3:
	/*
	 * DIR0 with values from 0x80 to 0x8f indicates a VIA Cyrix III, aka
	 * the Cyrix MIII. There may be parts later that use the same ranges
	 * for DIR0 with special values in DIR1, maybe the VIA CIII, but for
	 * now we will call anything with a DIR0 of 0x80 or higher an MIII.
	 * The MIII is supposed to support large pages, but we will believe
	 * it when we see it. For now we just enable and test for MII features.
	 */	
	movl	$X86_TYPE_VIA_CYRIX_III, x86_type
	jmp	likeMII

coma_bug:

/*
 * With NO_LOCK set to 0 in CCR1, the usual state that BIOS enforces, some
 * bus cycles are issued with LOCK# asserted. With NO_LOCK set to 1, all bus
 * cycles except page table accesses and interrupt ACK cycles do not assert
 * LOCK#. xchgl is an instruction that asserts LOCK# if NO_LOCK is set to 0.
 * Due to a bug in the cpu core involving over-optimization of branch
 * prediction, register renaming, and execution of instructions down both the
 * X and Y pipes for the xchgl instruction, short loops can be written that
 * never de-assert LOCK# from one invocation of the loop to the next, ad
 * infinitum. The undesirable effect of this situation is that interrupts are
 * not serviced. The ideal workaround to this bug would be to set NO_LOCK to
 * 1. Unfortunately bus cycles that would otherwise have asserted LOCK# no
 * longer do, unless they are page table accesses or interrupt ACK cycles.
 * With LOCK# not asserted, these bus cycles are now cached. This can cause
 * undesirable behaviour if the ARR's are not configured correctly. Solaris
 * does not configure the ARR's, nor does it provide any useful mechanism for
 * doing so, thus the ideal workaround is not viable. Fortunately, the only
 * known exploits for this bug involve the xchgl instruction specifically.
 * There is a group of undocumented registers on Cyrix 6x86, 6x86L, and
 * 6x86MX cpu's which can be used to specify one instruction as a serializing
 * instruction. With the xchgl instruction serialized, LOCK# is still
 * asserted, but it is the sole instruction for which LOCK# is asserted.
 * There is now some added penalty for the xchgl instruction, but the usual
 * bus locking is preserved. This ingenious workaround was discovered by
 * disassembling a binary provided by Cyrix as a workaround for this bug on
 * Windows, but its not documented anywhere by Cyrix, nor is the bug actually
 * mentioned in any public errata! The only concern for this workaround is
 * that there may be similar undiscovered bugs with other instructions that
 * assert LOCK# that may be leveraged to similar ends. The fact that Cyrix
 * fixed this bug sometime late in 1997 and no other exploits other than
 * xchgl have been discovered is good indication that this workaround is
 * reasonable.
 */	

	.set	CYRIX_DBR0, 0x30	/ Debug Register 0
	.set	CYRIX_DBR1, 0x31	/ Debug Register 1
	.set	CYRIX_DBR2, 0x32	/ Debug Register 2
	.set	CYRIX_DBR3, 0x33	/ Debug Register 3
	.set	CYRIX_DOR, 0x3c		/ Debug Opcode Register

	/*
 	 * What is known about DBR1, DBR2, DBR3, and DOR is that for normal
	 * cpu execution DBR1, DBR2, and DBR3 are set to 0. To obtain opcode
	 * serialization, DBR1, DBR2, and DBR3 are loaded with 0xb8, 0x7f,
	 * and 0xff. Then, DOR is loaded with the one byte opcode.
	 */

	/*
	 * select CCR3
	 */
	movb	$CYRIX_CCR3, %al
	outb	$CYRIX_CRI

	/*
	 * read CCR3 and mask out MAPEN
	 */
	inb	$CYRIX_CRD
	andb	$0xf, %al

	/*
	 * save masked CCR3 in %ah
	 */
	movb	%al, %ah

	/*
	 * select CCR3
	 */
	movb	$CYRIX_CCR3, %al
	outb	$CYRIX_CRI

	/*
	 * enable MAPEN
	 */
	movb	%ah, %al
	orb	$0x10, %al
	outb	$CYRIX_CRD

	/*
	 * read DBR0
	 */
	movb	$CYRIX_DBR0, %al
	outb	$CYRIX_CRI
	inb	$CYRIX_CRD

	/*
	 * disable MATCH and save in %bh
	 */
	orb	$0x80, %al
	movb	%al, %bh

	/*
	 * write DBR0
	 */
	movb	$CYRIX_DBR0, %al
	outb	$CYRIX_CRI
	movb	%bh, %al
	outb	$CYRIX_CRD

	/*
	 * write DBR1
	 */
	movb	$CYRIX_DBR1, %al 
	outb	$CYRIX_CRI
	movb	$0xf8, %al
	outb	$CYRIX_CRD

	/*
	 * write DBR2
	 */
	movb	$CYRIX_DBR2, %al
	outb	$CYRIX_CRI
	movb	$0x7f, %al
	outb	$CYRIX_CRD

	/*
	 * write DBR3
	 */
	movb	$CYRIX_DBR3, %al
	outb	$CYRIX_CRI
	xorb	%al, %al
	outb	$CYRIX_CRD

	/*
	 * write DOR
	 */
	movb	$CYRIX_DOR, %al
	outb	$CYRIX_CRI
	movb	$0x87, %al
	outb	$CYRIX_CRD

	/*
	 * enable MATCH
	 */
	movb	$CYRIX_DBR0, %al
	outb	$CYRIX_CRI
	movb	%bh, %al
	andb	$0x7f, %al
	outb	$CYRIX_CRD

	/*
	 * disable MAPEN
	 */
	movb	$0xc3, %al
	outb	$CYRIX_CRI
	movb	%ah, %al
	outb	$CYRIX_CRD

	jmp	cpu_done

cpu_done:

	popfl					/* Restore original FLAGS */
	popal					/* Restore all registers */

#endif	/* !__xpv */

	/*
	 *  mlsetup(%esp) gets called.
	 */
	pushl	%esp
	call	mlsetup
	addl	$4, %esp

	/*
	 * We change our appearance to look like the real thread 0.
	 * (NOTE: making ourselves to be a real thread may be a noop)
	 * main() gets called.  (NOTE: main() never returns).
	 */
	call	main
	/* NOTREACHED */
	pushl	$__return_from_main
	call	panic

	/* NOTREACHED */
cpu_486:
	pushl	$__unsupported_cpu
	call	panic
	SET_SIZE(_locore_start)

#endif	/* __lint */
#endif	/* !__amd64 */


/*
 *  For stack layout, see privregs.h
 *  When cmntrap gets called, the error code and trap number have been pushed.
 *  When cmntrap_pushed gets called, the entire struct regs has been pushed.
 */

#if defined(__lint)

/* ARGSUSED */
void
cmntrap()
{}

#else	/* __lint */

	.globl	trap		/* C handler called below */

#if defined(__amd64)

	ENTRY_NP2(cmntrap, _cmntrap)

	INTR_PUSH

	ALTENTRY(cmntrap_pushed)

	movq	%rsp, %rbp

	/*
	 * - if this is a #pf i.e. T_PGFLT, %r15 is live
	 *   and contains the faulting address i.e. a copy of %cr2
	 *
	 * - if this is a #db i.e. T_SGLSTP, %r15 is live
	 *   and contains the value of %db6
	 */

	TRACE_PTR(%rdi, %rbx, %ebx, %rcx, $TT_TRAP) /* Uses labels 8 and 9 */
	TRACE_REGS(%rdi, %rsp, %rbx, %rcx)	/* Uses label 9 */
	TRACE_STAMP(%rdi)		/* Clobbers %eax, %edx, uses 9 */

	/*
	 * We must first check if DTrace has set its NOFAULT bit.  This
	 * regrettably must happen before the trap stack is recorded, because
	 * this requires a call to getpcstack() and may induce recursion if an
	 * fbt::getpcstack: enabling is inducing the bad load.
	 */
	movl	%gs:CPU_ID, %eax
	shlq	$CPU_CORE_SHIFT, %rax
	leaq	cpu_core(%rip), %r8
	addq	%r8, %rax
	movw	CPUC_DTRACE_FLAGS(%rax), %cx
	testw	$CPU_DTRACE_NOFAULT, %cx
	jnz	.dtrace_induced

	TRACE_STACK(%rdi)

	movq	%rbp, %rdi
	movq	%r15, %rsi
	movl	%gs:CPU_ID, %edx

	/*
	 * We know that this isn't a DTrace non-faulting load; we can now safely
	 * reenable interrupts.  (In the case of pagefaults, we enter through an
	 * interrupt gate.)
	 */
	ENABLE_INTR_FLAGS

	call	trap		/* trap(rp, addr, cpuid) handles all traps */
	jmp	_sys_rtt

.dtrace_induced:
	cmpw	$KCS_SEL, REGOFF_CS(%rbp)	/* test CS for user-mode trap */
	jne	2f				/* if from user, panic */

	cmpl	$T_PGFLT, REGOFF_TRAPNO(%rbp)
	je	0f

	cmpl	$T_GPFLT, REGOFF_TRAPNO(%rbp)
	jne	3f				/* if not PF or GP, panic */

	/*
	 * If we've taken a GPF, we don't (unfortunately) have the address that
	 * induced the fault.  So instead of setting the fault to BADADDR,
	 * we'll set the fault to ILLOP.
	 */
	orw	$CPU_DTRACE_ILLOP, %cx
	movw	%cx, CPUC_DTRACE_FLAGS(%rax)
	jmp	1f
0:
	orw	$CPU_DTRACE_BADADDR, %cx
	movw	%cx, CPUC_DTRACE_FLAGS(%rax)	/* set fault to bad addr */
	movq	%r15, CPUC_DTRACE_ILLVAL(%rax)
					    /* fault addr is illegal value */
1:
	movq	REGOFF_RIP(%rbp), %rdi
	movq	%rdi, %r12
	call	dtrace_instr_size
	addq	%rax, %r12
	movq	%r12, REGOFF_RIP(%rbp)
	INTR_POP
	IRET
	/*NOTREACHED*/
2:
	leaq	dtrace_badflags(%rip), %rdi
	xorl	%eax, %eax
	call	panic
3:
	leaq	dtrace_badtrap(%rip), %rdi
	xorl	%eax, %eax
	call	panic
	SET_SIZE(cmntrap)
	SET_SIZE(_cmntrap)

#elif defined(__i386)


	ENTRY_NP2(cmntrap, _cmntrap)

	INTR_PUSH

	ALTENTRY(cmntrap_pushed)

	movl	%esp, %ebp

	/*
	 * - if this is a #pf i.e. T_PGFLT, %esi is live
	 *   and contains the faulting address i.e. a copy of %cr2
	 *
	 * - if this is a #db i.e. T_SGLSTP, %esi is live
	 *   and contains the value of %db6
	 */

	TRACE_PTR(%edi, %ebx, %ebx, %ecx, $TT_TRAP) /* Uses labels 8 and 9 */
	TRACE_REGS(%edi, %esp, %ebx, %ecx)	/* Uses label 9 */
	TRACE_STAMP(%edi)		/* Clobbers %eax, %edx, uses 9 */

	/*
	 * We must first check if DTrace has set its NOFAULT bit.  This
	 * regrettably must happen before the trap stack is recorded, because
	 * this requires a call to getpcstack() and may induce recursion if an
	 * fbt::getpcstack: enabling is inducing the bad load.
	 */
	movl	%gs:CPU_ID, %eax
	shll	$CPU_CORE_SHIFT, %eax
	addl	$cpu_core, %eax
	movw	CPUC_DTRACE_FLAGS(%eax), %cx
	testw	$CPU_DTRACE_NOFAULT, %cx
	jnz	.dtrace_induced

	TRACE_STACK(%edi)

	pushl	%gs:CPU_ID
	pushl	%esi		/* fault address for PGFLTs */
	pushl	%ebp		/* &regs */

	/*
	 * We know that this isn't a DTrace non-faulting load; we can now safely
	 * reenable interrupts.  (In the case of pagefaults, we enter through an
	 * interrupt gate.)
	 */
	ENABLE_INTR_FLAGS

	call	trap		/* trap(rp, addr, cpuid) handles all traps */
	addl	$12, %esp	/* get argument off stack */
	jmp	_sys_rtt

.dtrace_induced:
	cmpw	$KCS_SEL, REGOFF_CS(%ebp)	/* test CS for user-mode trap */
	jne	2f				/* if from user, panic */

	cmpl	$T_PGFLT, REGOFF_TRAPNO(%ebp)
	je	0f

	cmpl	$T_GPFLT, REGOFF_TRAPNO(%ebp)
	jne	3f				/* if not PF or GP, panic */

	/*
	 * If we've taken a GPF, we don't (unfortunately) have the address that
	 * induced the fault.  So instead of setting the fault to BADADDR,
	 * we'll set the fault to ILLOP.
	 */
	orw	$CPU_DTRACE_ILLOP, %cx
	movw	%cx, CPUC_DTRACE_FLAGS(%eax)
	jmp	1f
0:
	orw	$CPU_DTRACE_BADADDR, %cx
	movw	%cx, CPUC_DTRACE_FLAGS(%eax)	/* set fault to bad addr */
	movl	%esi, CPUC_DTRACE_ILLVAL(%eax)
					    /* fault addr is illegal value */
1:
	pushl	REGOFF_EIP(%ebp)
	call	dtrace_instr_size
	addl	$4, %esp
	movl	REGOFF_EIP(%ebp), %ecx
	addl	%eax, %ecx
	movl	%ecx, REGOFF_EIP(%ebp)
	INTR_POP_KERNEL
	IRET
	/*NOTREACHED*/
2:
	pushl	$dtrace_badflags
	call	panic
3:
	pushl	$dtrace_badtrap
	call	panic
	SET_SIZE(cmntrap)
	SET_SIZE(_cmntrap)

#endif	/* __i386 */

/*
 * Declare a uintptr_t which has the size of _cmntrap to enable stack
 * traceback code to know when a regs structure is on the stack.
 */
	.globl	_cmntrap_size
	.align	CLONGSIZE
_cmntrap_size:
	.NWORD	. - _cmntrap
	.type	_cmntrap_size, @object

dtrace_badflags:
	.string "bad DTrace flags"

dtrace_badtrap:
	.string "bad DTrace trap"

#endif	/* __lint */

#if defined(__lint)

/* ARGSUSED */
void
cmninttrap()
{}

#if !defined(__xpv)
void
bop_trap_handler(void)
{}
#endif

#else	/* __lint */

	.globl	trap		/* C handler called below */

#if defined(__amd64)

	ENTRY_NP(cmninttrap)

	INTR_PUSH
	INTGATE_INIT_KERNEL_FLAGS

	TRACE_PTR(%rdi, %rbx, %ebx, %rcx, $TT_TRAP) /* Uses labels 8 and 9 */
	TRACE_REGS(%rdi, %rsp, %rbx, %rcx)	/* Uses label 9 */
	TRACE_STAMP(%rdi)		/* Clobbers %eax, %edx, uses 9 */

	movq	%rsp, %rbp

	movl	%gs:CPU_ID, %edx
	xorl	%esi, %esi
	movq	%rsp, %rdi
	call	trap		/* trap(rp, addr, cpuid) handles all traps */
	jmp	_sys_rtt
	SET_SIZE(cmninttrap)

#if !defined(__xpv)
	/*
	 * Handle traps early in boot. Just revectors into C quickly as
	 * these are always fatal errors.
	 */
	ENTRY(bop_trap_handler)
	movq	%rsp, %rdi
	call	bop_trap
	SET_SIZE(bop_trap_handler)
#endif

#elif defined(__i386)

	ENTRY_NP(cmninttrap)

	INTR_PUSH
	INTGATE_INIT_KERNEL_FLAGS

	TRACE_PTR(%edi, %ebx, %ebx, %ecx, $TT_TRAP) /* Uses labels 8 and 9 */
	TRACE_REGS(%edi, %esp, %ebx, %ecx)	/* Uses label 9 */
	TRACE_STAMP(%edi)		/* Clobbers %eax, %edx, uses 9 */

	movl	%esp, %ebp

	TRACE_STACK(%edi)

	pushl	%gs:CPU_ID
	pushl	$0
	pushl	%ebp
	call	trap		/* trap(rp, addr, cpuid) handles all traps */
	addl	$12, %esp
	jmp	_sys_rtt
	SET_SIZE(cmninttrap)

#if !defined(__xpv)
	/*
	 * Handle traps early in boot. Just revectors into C quickly as
	 * these are always fatal errors.
	 */
	ENTRY(bop_trap_handler)
	movl	%esp, %eax
	pushl	%eax
	call	bop_trap
	SET_SIZE(bop_trap_handler)
#endif

#endif	/* __i386 */

#endif	/* __lint */

#if defined(__lint)

/* ARGSUSED */
void
dtrace_trap()
{}

#else	/* __lint */

	.globl	dtrace_user_probe

#if defined(__amd64)

	ENTRY_NP(dtrace_trap)

	INTR_PUSH

	TRACE_PTR(%rdi, %rbx, %ebx, %rcx, $TT_TRAP) /* Uses labels 8 and 9 */
	TRACE_REGS(%rdi, %rsp, %rbx, %rcx)	/* Uses label 9 */
	TRACE_STAMP(%rdi)		/* Clobbers %eax, %edx, uses 9 */

	movq	%rsp, %rbp

	movl	%gs:CPU_ID, %edx
#if defined(__xpv)
	movq	%gs:CPU_VCPU_INFO, %rsi
	movq	VCPU_INFO_ARCH_CR2(%rsi), %rsi
#else
	movq	%cr2, %rsi
#endif
	movq	%rsp, %rdi

	ENABLE_INTR_FLAGS

	call	dtrace_user_probe /* dtrace_user_probe(rp, addr, cpuid) */
	jmp	_sys_rtt

	SET_SIZE(dtrace_trap)

#elif defined(__i386)

	ENTRY_NP(dtrace_trap)

	INTR_PUSH

	TRACE_PTR(%edi, %ebx, %ebx, %ecx, $TT_TRAP) /* Uses labels 8 and 9 */
	TRACE_REGS(%edi, %esp, %ebx, %ecx)	/* Uses label 9 */
	TRACE_STAMP(%edi)		/* Clobbers %eax, %edx, uses 9 */

	movl	%esp, %ebp

	pushl	%gs:CPU_ID
#if defined(__xpv)
	movl	%gs:CPU_VCPU_INFO, %eax
	movl	VCPU_INFO_ARCH_CR2(%eax), %eax
#else
	movl	%cr2, %eax
#endif
	pushl	%eax
	pushl	%ebp

	ENABLE_INTR_FLAGS

	call	dtrace_user_probe /* dtrace_user_probe(rp, addr, cpuid) */
	addl	$12, %esp		/* get argument off stack */

	jmp	_sys_rtt
	SET_SIZE(dtrace_trap)

#endif	/* __i386 */

#endif	/* __lint */

/*
 * Return from _sys_trap routine.
 */

#if defined(__lint)

void
lwp_rtt_initial(void)
{}

void
lwp_rtt(void)
{}

void
_sys_rtt(void)
{}

#else	/* __lint */

#if defined(__amd64)

	ENTRY_NP(lwp_rtt_initial)
	movq	%gs:CPU_THREAD, %r15
	movq	T_STACK(%r15), %rsp	/* switch to the thread stack */
	call	__dtrace_probe___proc_start
	jmp	_lwp_rtt

	ENTRY_NP(lwp_rtt)

	/*
	 * r14	lwp
	 * rdx	lwp->lwp_procp
	 * r15	curthread
	 */

	movq	%gs:CPU_THREAD, %r15
	movq	T_STACK(%r15), %rsp	/* switch to the thread stack */
_lwp_rtt:
	call	__dtrace_probe___proc_lwp__start
	movq	%gs:CPU_LWP, %r14
	movq	LWP_PROCP(%r14), %rdx

	/*
	 * XX64	Is the stack misaligned correctly at this point?
	 *	If not, we need to do a push before calling anything ..
	 */

#if defined(DEBUG)
	/*
	 * If we were to run lwp_savectx at this point -without-
	 * pcb_rupdate being set to 1, we'd end up sampling the hardware
	 * state left by the previous running lwp, rather than setting
	 * the values requested by the lwp creator.  Bad.
	 */
	testb	$0x1, PCB_RUPDATE(%r14)
	jne	1f
	leaq	_no_pending_updates(%rip), %rdi
	movl	$__LINE__, %esi
	movq	%r14, %rdx
	xorl	%eax, %eax
	call	panic
_no_pending_updates:
	.string	"locore.s:%d lwp_rtt(lwp %p) but pcb_rupdate != 1"
1:
#endif

	/*
	 * If agent lwp, clear %fs and %gs
	 */
	cmpq	%r15, P_AGENTTP(%rdx)
	jne	1f
	xorl	%ecx, %ecx
	movq	%rcx, REGOFF_FS(%rsp)
	movq	%rcx, REGOFF_GS(%rsp)
	movw	%cx, LWP_PCB_FS(%r14)
	movw	%cx, LWP_PCB_GS(%r14)
1:
	call	dtrace_systrace_rtt
	movq	REGOFF_RDX(%rsp), %rsi
	movq	REGOFF_RAX(%rsp), %rdi
	call	post_syscall		/* post_syscall(rval1, rval2) */

	/*
	 * set up to take fault on first use of fp
	 */
	STTS(%rdi)

	/*
	 * XXX - may want a fast path that avoids sys_rtt_common in the
	 * most common case.
	 */
	ALTENTRY(_sys_rtt)
	CLI(%rax)			/* disable interrupts */
	ALTENTRY(_sys_rtt_ints_disabled)
	movq	%rsp, %rdi		/* pass rp to sys_rtt_common */
	call	sys_rtt_common		/* do common sys_rtt tasks */
	testq	%rax, %rax		/* returning to userland? */
	jz	sr_sup

	/*
	 * Return to user
	 */
	ASSERT_UPCALL_MASK_IS_SET
	cmpw	$UCS_SEL, REGOFF_CS(%rsp) /* test for native (64-bit) lwp? */
	je	sys_rtt_syscall

	/*
	 * Return to 32-bit userland
	 */
	ALTENTRY(sys_rtt_syscall32)
	USER32_POP

	/*
	 * There can be no instructions between this label and IRET or
	 * we could end up breaking linux brand support. See label usage
	 * in lx_brand_int80_callback for an example.
	 */
	ALTENTRY(nopop_sys_rtt_syscall32)
	IRET
	/*NOTREACHED*/
	SET_SIZE(nopop_sys_rtt_syscall32)

	ALTENTRY(sys_rtt_syscall)
	/*
	 * Return to 64-bit userland
	 */
	USER_POP
	ALTENTRY(nopop_sys_rtt_syscall)
	IRET
	/*NOTREACHED*/
	SET_SIZE(nopop_sys_rtt_syscall)

	/*
	 * Return to supervisor
	 * NOTE: to make the check in trap() that tests if we are executing
	 * segment register fixup/restore code work properly, sr_sup MUST be
	 * after _sys_rtt .
	 */
	ALTENTRY(sr_sup)
	/*
	 * Restore regs before doing iretq to kernel mode
	 */
	INTR_POP
	IRET
	.globl	_sys_rtt_end
_sys_rtt_end:
	/*NOTREACHED*/
	SET_SIZE(sr_sup)
	SET_SIZE(_sys_rtt_end)
	SET_SIZE(lwp_rtt)
	SET_SIZE(lwp_rtt_initial)
	SET_SIZE(_sys_rtt_ints_disabled)
	SET_SIZE(_sys_rtt)
	SET_SIZE(sys_rtt_syscall)
	SET_SIZE(sys_rtt_syscall32)

#elif defined(__i386)

	ENTRY_NP(lwp_rtt_initial)
	movl	%gs:CPU_THREAD, %eax
	movl	T_STACK(%eax), %esp	/* switch to the thread stack */
	call	__dtrace_probe___proc_start
	jmp	_lwp_rtt

	ENTRY_NP(lwp_rtt)
	movl	%gs:CPU_THREAD, %eax
	movl	T_STACK(%eax), %esp	/* switch to the thread stack */
_lwp_rtt:
	call	__dtrace_probe___proc_lwp__start

        /*
         * If agent lwp, clear %fs and %gs.
         */
        movl    %gs:CPU_LWP, %eax
        movl    LWP_PROCP(%eax), %edx

        cmpl    %eax, P_AGENTTP(%edx)
        jne     1f
        movl    $0, REGOFF_FS(%esp)
        movl    $0, REGOFF_GS(%esp)
1:
	call	dtrace_systrace_rtt
	movl	REGOFF_EDX(%esp), %edx
	movl	REGOFF_EAX(%esp), %eax
	pushl	%edx
	pushl	%eax
	call	post_syscall		/* post_syscall(rval1, rval2) */
	addl	$8, %esp

	/*
	 * set up to take fault on first use of fp
	 */
	STTS(%eax)

	/*
	 * XXX - may want a fast path that avoids sys_rtt_common in the
	 * most common case.
	 */
	ALTENTRY(_sys_rtt)
	CLI(%eax)			/* disable interrupts */
	ALTENTRY(_sys_rtt_ints_disabled)
	pushl	%esp			/* pass rp to sys_rtt_common */
	call	sys_rtt_common
	addl	$4, %esp		/* pop arg */
	testl	%eax, %eax		/* test for return to user mode */
	jz	sr_sup

	/*
	 * Return to User.
	 */
	ALTENTRY(sys_rtt_syscall)
	INTR_POP_USER

	/*
	 * There can be no instructions between this label and IRET or
	 * we could end up breaking linux brand support. See label usage
	 * in lx_brand_int80_callback for an example.
	 */
	ALTENTRY(nopop_sys_rtt_syscall)
	IRET
	/*NOTREACHED*/
	SET_SIZE(nopop_sys_rtt_syscall)

	ALTENTRY(_sys_rtt_end)

	/*
	 * Return to supervisor
	 */
	ALTENTRY(sr_sup)

	/*
	 * Restore regs before doing iret to kernel mode
	 */
	INTR_POP_KERNEL
	IRET
	/*NOTREACHED*/

	SET_SIZE(sr_sup)
	SET_SIZE(_sys_rtt_end)
	SET_SIZE(lwp_rtt)
	SET_SIZE(lwp_rtt_initial)
	SET_SIZE(_sys_rtt_ints_disabled)
	SET_SIZE(_sys_rtt)
	SET_SIZE(sys_rtt_syscall)

#endif	/* __i386 */

#endif	/* __lint */

#if defined(__lint)

/*
 * So why do we have to deal with all this crud in the world of ia32?
 *
 * Basically there are four classes of ia32 implementations, those that do not
 * have a TSC, those that have a marginal TSC that is broken to the extent
 * that it is useless, those that have a marginal TSC that is not quite so
 * horribly broken and can be used with some care, and those that have a
 * reliable TSC. This crud has to be here in order to sift through all the
 * variants.
 */

/*ARGSUSED*/
uint64_t
freq_tsc(uint32_t *pit_counter)
{
	return (0);
}

#else	/* __lint */

#if defined(__amd64)

	/*
	 * XX64 quick and dirty port from the i386 version. Since we
	 * believe the amd64 tsc is more reliable, could this code be
	 * simpler?
	 */
	ENTRY_NP(freq_tsc)
	pushq	%rbp
	movq	%rsp, %rbp
	movq	%rdi, %r9	/* save pit_counter */
	pushq	%rbx

/ We have a TSC, but we have no way in general to know how reliable it is.
/ Usually a marginal TSC behaves appropriately unless not enough time
/ elapses between reads. A reliable TSC can be read as often and as rapidly
/ as desired. The simplistic approach of reading the TSC counter and
/ correlating to the PIT counter cannot be naively followed. Instead estimates
/ have to be taken to successively refine a guess at the speed of the cpu
/ and then the TSC and PIT counter are correlated. In practice very rarely
/ is more than one quick loop required for an estimate. Measures have to be
/ taken to prevent the PIT counter from wrapping beyond its resolution and for
/ measuring the clock rate of very fast processors.
/
/ The following constant can be tuned. It should be such that the loop does
/ not take too many nor too few PIT counts to execute. If this value is too
/ large, then on slow machines the loop will take a long time, or the PIT
/ counter may even wrap. If this value is too small, then on fast machines
/ the PIT counter may count so few ticks that the resolution of the PIT
/ itself causes a bad guess. Because this code is used in machines with
/ marginal TSC's and/or IO, if this value is too small on those, it may
/ cause the calculated cpu frequency to vary slightly from boot to boot.
/
/ In all cases even if this constant is set inappropriately, the algorithm
/ will still work and the caller should be able to handle variances in the
/ calculation of cpu frequency, but the calculation will be inefficient and
/ take a disproportionate amount of time relative to a well selected value.
/ As the slowest supported cpu becomes faster, this constant should be
/ carefully increased.

	movl	$0x8000, %ecx

	/ to make sure the instruction cache has been warmed
	clc

	jmp	freq_tsc_loop

/ The following block of code up to and including the latching of the PIT
/ counter after freq_tsc_perf_loop is very critical and very carefully
/ written, it should only be modified with great care. freq_tsc_loop to
/ freq_tsc_perf_loop fits exactly in 16 bytes as do the instructions in
/ freq_tsc_perf_loop up to the unlatching of the PIT counter.

	.align	32
freq_tsc_loop:
	/ save the loop count in %ebx
	movl	%ecx, %ebx

	/ initialize the PIT counter and start a count down
	movb	$PIT_LOADMODE, %al
	outb	$PITCTL_PORT
	movb	$0xff, %al
	outb	$PITCTR0_PORT
	outb	$PITCTR0_PORT

	/ read the TSC and store the TS in %edi:%esi
	rdtsc
	movl	%eax, %esi

freq_tsc_perf_loop:
	movl	%edx, %edi
	movl	%eax, %esi
	movl	%edx, %edi
	loop	freq_tsc_perf_loop

	/ read the TSC and store the LSW in %ecx
	rdtsc
	movl	%eax, %ecx

	/ latch the PIT counter and status
	movb	$_CONST(PIT_READBACK|PIT_READBACKC0), %al
	outb	$PITCTL_PORT

	/ remember if the icache has been warmed
	setc	%ah

	/ read the PIT status
	inb	$PITCTR0_PORT
	shll	$8, %eax

	/ read PIT count
	inb	$PITCTR0_PORT
	shll	$8, %eax
	inb	$PITCTR0_PORT
	bswap	%eax

	/ check to see if the PIT count was loaded into the CE
	btw	$_CONST(PITSTAT_NULLCNT+8), %ax
	jc	freq_tsc_increase_count

	/ check to see if PIT counter wrapped
	btw	$_CONST(PITSTAT_OUTPUT+8), %ax
	jnc	freq_tsc_pit_did_not_wrap

	/ halve count
	shrl	$1, %ebx
	movl	%ebx, %ecx

	/ the instruction cache has been warmed
	stc

	jmp	freq_tsc_loop

freq_tsc_increase_count:
	shll	$1, %ebx
	jc	freq_tsc_too_fast

	movl	%ebx, %ecx

	/ the instruction cache has been warmed
	stc

	jmp	freq_tsc_loop

freq_tsc_pit_did_not_wrap:
	roll	$16, %eax

	cmpw	$0x2000, %ax
	notw	%ax
	jb	freq_tsc_sufficient_duration

freq_tsc_calculate:
	/ in mode 0, the PIT loads the count into the CE on the first CLK pulse,
	/ then on the second CLK pulse the CE is decremented, therefore mode 0
	/ is really a (count + 1) counter, ugh
	xorl	%esi, %esi
	movw	%ax, %si
	incl	%esi

	movl	$0xf000, %eax
	mull	%ebx

	/ tuck away (target_pit_count * loop_count)
	movl	%edx, %ecx
	movl	%eax, %ebx

	movl	%esi, %eax
	movl	$0xffffffff, %edx
	mull	%edx

	addl	%esi, %eax
	adcl	$0, %edx

	cmpl	%ecx, %edx
	ja	freq_tsc_div_safe
	jb	freq_tsc_too_fast

	cmpl	%ebx, %eax
	jbe	freq_tsc_too_fast

freq_tsc_div_safe:
	movl	%ecx, %edx
	movl	%ebx, %eax

	movl	%esi, %ecx
	divl	%ecx

	movl	%eax, %ecx

	/ the instruction cache has been warmed
	stc

	jmp	freq_tsc_loop

freq_tsc_sufficient_duration:
	/ test to see if the icache has been warmed
	btl	$16, %eax
	jnc	freq_tsc_calculate

	/ recall mode 0 is a (count + 1) counter
	andl	$0xffff, %eax
	incl	%eax

	/ save the number of PIT counts
	movl	%eax, (%r9)

	/ calculate the number of TS's that elapsed
	movl	%ecx, %eax
	subl	%esi, %eax
	sbbl	%edi, %edx

	jmp	freq_tsc_end

freq_tsc_too_fast:
	/ return 0 as a 64 bit quantity
	xorl	%eax, %eax
	xorl	%edx, %edx

freq_tsc_end:
	shlq	$32, %rdx
	orq	%rdx, %rax

	popq	%rbx
	leaveq
	ret
	SET_SIZE(freq_tsc)

#elif defined(__i386)

	ENTRY_NP(freq_tsc)
	pushl	%ebp
	movl	%esp, %ebp
	pushl	%edi
	pushl	%esi
	pushl	%ebx

/ We have a TSC, but we have no way in general to know how reliable it is.
/ Usually a marginal TSC behaves appropriately unless not enough time
/ elapses between reads. A reliable TSC can be read as often and as rapidly
/ as desired. The simplistic approach of reading the TSC counter and
/ correlating to the PIT counter cannot be naively followed. Instead estimates
/ have to be taken to successively refine a guess at the speed of the cpu
/ and then the TSC and PIT counter are correlated. In practice very rarely
/ is more than one quick loop required for an estimate. Measures have to be
/ taken to prevent the PIT counter from wrapping beyond its resolution and for
/ measuring the clock rate of very fast processors.
/
/ The following constant can be tuned. It should be such that the loop does
/ not take too many nor too few PIT counts to execute. If this value is too
/ large, then on slow machines the loop will take a long time, or the PIT
/ counter may even wrap. If this value is too small, then on fast machines
/ the PIT counter may count so few ticks that the resolution of the PIT
/ itself causes a bad guess. Because this code is used in machines with
/ marginal TSC's and/or IO, if this value is too small on those, it may
/ cause the calculated cpu frequency to vary slightly from boot to boot.
/
/ In all cases even if this constant is set inappropriately, the algorithm
/ will still work and the caller should be able to handle variances in the
/ calculation of cpu frequency, but the calculation will be inefficient and
/ take a disproportionate amount of time relative to a well selected value.
/ As the slowest supported cpu becomes faster, this constant should be
/ carefully increased.

	movl	$0x8000, %ecx

	/ to make sure the instruction cache has been warmed
	clc

	jmp	freq_tsc_loop

/ The following block of code up to and including the latching of the PIT
/ counter after freq_tsc_perf_loop is very critical and very carefully
/ written, it should only be modified with great care. freq_tsc_loop to
/ freq_tsc_perf_loop fits exactly in 16 bytes as do the instructions in
/ freq_tsc_perf_loop up to the unlatching of the PIT counter.

	.align	32
freq_tsc_loop:
	/ save the loop count in %ebx
	movl	%ecx, %ebx

	/ initialize the PIT counter and start a count down
	movb	$PIT_LOADMODE, %al
	outb	$PITCTL_PORT
	movb	$0xff, %al
	outb	$PITCTR0_PORT
	outb	$PITCTR0_PORT

	/ read the TSC and store the TS in %edi:%esi
	rdtsc
	movl	%eax, %esi

freq_tsc_perf_loop:
	movl	%edx, %edi
	movl	%eax, %esi
	movl	%edx, %edi
	loop	freq_tsc_perf_loop

	/ read the TSC and store the LSW in %ecx
	rdtsc
	movl	%eax, %ecx

	/ latch the PIT counter and status
	movb	$_CONST(PIT_READBACK|PIT_READBACKC0), %al
	outb	$PITCTL_PORT

	/ remember if the icache has been warmed
	setc	%ah

	/ read the PIT status
	inb	$PITCTR0_PORT
	shll	$8, %eax

	/ read PIT count
	inb	$PITCTR0_PORT
	shll	$8, %eax
	inb	$PITCTR0_PORT
	bswap	%eax

	/ check to see if the PIT count was loaded into the CE
	btw	$_CONST(PITSTAT_NULLCNT+8), %ax
	jc	freq_tsc_increase_count

	/ check to see if PIT counter wrapped
	btw	$_CONST(PITSTAT_OUTPUT+8), %ax
	jnc	freq_tsc_pit_did_not_wrap

	/ halve count
	shrl	$1, %ebx
	movl	%ebx, %ecx

	/ the instruction cache has been warmed
	stc

	jmp	freq_tsc_loop

freq_tsc_increase_count:
	shll	$1, %ebx
	jc	freq_tsc_too_fast

	movl	%ebx, %ecx

	/ the instruction cache has been warmed
	stc

	jmp	freq_tsc_loop

freq_tsc_pit_did_not_wrap:
	roll	$16, %eax

	cmpw	$0x2000, %ax
	notw	%ax
	jb	freq_tsc_sufficient_duration

freq_tsc_calculate:
	/ in mode 0, the PIT loads the count into the CE on the first CLK pulse,
	/ then on the second CLK pulse the CE is decremented, therefore mode 0
	/ is really a (count + 1) counter, ugh
	xorl	%esi, %esi
	movw	%ax, %si
	incl	%esi

	movl	$0xf000, %eax
	mull	%ebx

	/ tuck away (target_pit_count * loop_count)
	movl	%edx, %ecx
	movl	%eax, %ebx

	movl	%esi, %eax
	movl	$0xffffffff, %edx
	mull	%edx

	addl	%esi, %eax
	adcl	$0, %edx

	cmpl	%ecx, %edx
	ja	freq_tsc_div_safe
	jb	freq_tsc_too_fast

	cmpl	%ebx, %eax
	jbe	freq_tsc_too_fast

freq_tsc_div_safe:
	movl	%ecx, %edx
	movl	%ebx, %eax

	movl	%esi, %ecx
	divl	%ecx

	movl	%eax, %ecx

	/ the instruction cache has been warmed
	stc

	jmp	freq_tsc_loop

freq_tsc_sufficient_duration:
	/ test to see if the icache has been warmed
	btl	$16, %eax
	jnc	freq_tsc_calculate

	/ recall mode 0 is a (count + 1) counter
	andl	$0xffff, %eax
	incl	%eax

	/ save the number of PIT counts
	movl	8(%ebp), %ebx
	movl	%eax, (%ebx)

	/ calculate the number of TS's that elapsed
	movl	%ecx, %eax
	subl	%esi, %eax
	sbbl	%edi, %edx

	jmp	freq_tsc_end

freq_tsc_too_fast:
	/ return 0 as a 64 bit quantity
	xorl	%eax, %eax
	xorl	%edx, %edx

freq_tsc_end:
	popl	%ebx
	popl	%esi
	popl	%edi
	popl	%ebp
	ret
	SET_SIZE(freq_tsc)

#endif	/* __i386 */
#endif	/* __lint */

#if !defined(__amd64)
#if defined(__lint)

/*
 * We do not have a TSC so we use a block of instructions with well known
 * timings.
 */

/*ARGSUSED*/
uint64_t
freq_notsc(uint32_t *pit_counter)
{
	return (0);
}

#else	/* __lint */
	ENTRY_NP(freq_notsc)
	pushl	%ebp
	movl	%esp, %ebp
	pushl	%edi
	pushl	%esi
	pushl	%ebx

	/ initial count for the idivl loop
	movl	$0x1000, %ecx

	/ load the divisor
	movl	$1, %ebx

	jmp	freq_notsc_loop

.align	16
freq_notsc_loop:
	/ set high 32 bits of dividend to zero
	xorl	%edx, %edx

	/ save the loop count in %edi
	movl	%ecx, %edi

	/ initialize the PIT counter and start a count down
	movb	$PIT_LOADMODE, %al
	outb	$PITCTL_PORT
	movb	$0xff, %al
	outb	$PITCTR0_PORT
	outb	$PITCTR0_PORT

	/ set low 32 bits of dividend to zero
	xorl	%eax, %eax

/ It is vital that the arguments to idivl be set appropriately because on some
/ cpu's this instruction takes more or less clock ticks depending on its
/ arguments.
freq_notsc_perf_loop:
	idivl	%ebx
	idivl	%ebx
	idivl	%ebx
	idivl	%ebx
	idivl	%ebx
	loop	freq_notsc_perf_loop

	/ latch the PIT counter and status
	movb	$_CONST(PIT_READBACK|PIT_READBACKC0), %al
	outb	$PITCTL_PORT

	/ read the PIT status
	inb	$PITCTR0_PORT
	shll	$8, %eax

	/ read PIT count
	inb	$PITCTR0_PORT
	shll	$8, %eax
	inb	$PITCTR0_PORT
	bswap	%eax

	/ check to see if the PIT count was loaded into the CE
	btw	$_CONST(PITSTAT_NULLCNT+8), %ax
	jc	freq_notsc_increase_count

	/ check to see if PIT counter wrapped
	btw	$_CONST(PITSTAT_OUTPUT+8), %ax
	jnc	freq_notsc_pit_did_not_wrap

	/ halve count
	shrl	$1, %edi
	movl	%edi, %ecx

	jmp	freq_notsc_loop

freq_notsc_increase_count:
	shll	$1, %edi
	jc	freq_notsc_too_fast

	movl	%edi, %ecx

	jmp	freq_notsc_loop

freq_notsc_pit_did_not_wrap:
	shrl	$16, %eax

	cmpw	$0x2000, %ax
	notw	%ax
	jb	freq_notsc_sufficient_duration

freq_notsc_calculate:
	/ in mode 0, the PIT loads the count into the CE on the first CLK pulse,
	/ then on the second CLK pulse the CE is decremented, therefore mode 0
	/ is really a (count + 1) counter, ugh
	xorl	%esi, %esi
	movw	%ax, %si
	incl	%esi

	movl	%edi, %eax
	movl	$0xf000, %ecx
	mull	%ecx

	/ tuck away (target_pit_count * loop_count)
	movl	%edx, %edi
	movl	%eax, %ecx

	movl	%esi, %eax
	movl	$0xffffffff, %edx
	mull	%edx

	addl	%esi, %eax
	adcl	$0, %edx

	cmpl	%edi, %edx
	ja	freq_notsc_div_safe
	jb	freq_notsc_too_fast

	cmpl	%ecx, %eax
	jbe	freq_notsc_too_fast

freq_notsc_div_safe:
	movl	%edi, %edx
	movl	%ecx, %eax

	movl	%esi, %ecx
	divl	%ecx

	movl	%eax, %ecx

	jmp	freq_notsc_loop

freq_notsc_sufficient_duration:
	/ recall mode 0 is a (count + 1) counter
	incl	%eax

	/ save the number of PIT counts
	movl	8(%ebp), %ebx
	movl	%eax, (%ebx)

	/ calculate the number of cpu clock ticks that elapsed
	cmpl	$X86_VENDOR_Cyrix, x86_vendor
	jz	freq_notsc_notcyrix

	/ freq_notsc_perf_loop takes 86 clock cycles on Cyrix 6x86 cores
	movl	$86, %eax
	jmp	freq_notsc_calculate_tsc

freq_notsc_notcyrix:
	/ freq_notsc_perf_loop takes 237 clock cycles on Intel Pentiums
	movl	$237, %eax

freq_notsc_calculate_tsc:
	mull	%edi

	jmp	freq_notsc_end

freq_notsc_too_fast:
	/ return 0 as a 64 bit quantity
	xorl	%eax, %eax
	xorl	%edx, %edx

freq_notsc_end:
	popl	%ebx
	popl	%esi
	popl	%edi
	popl	%ebp

	ret
	SET_SIZE(freq_notsc)

#endif	/* __lint */
#endif	/* !__amd64 */

#if !defined(__lint)
	.data
#if !defined(__amd64)
	.align	4
cpu_vendor:
	.long	0, 0, 0		/* Vendor ID string returned */

	.globl	CyrixInstead

	.globl	x86_feature
	.globl	x86_type
	.globl	x86_vendor
#endif

#endif	/* __lint */