[apple/xnu.git] / osfmk / i386 / commpage / commpage_mach_absolute_time.s

/*
 * Copyright (c) 2003 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 * 
 * The contents of this file constitute Original Code as defined in and
 * are subject to the Apple Public Source License Version 1.1 (the
 * "License").  You may not use this file except in compliance with the
 * License.  Please obtain a copy of the License at
 * http://www.apple.com/publicsource and read it before using this file.
 * 
 * This Original Code and all software distributed under the License are
 * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
 * License for the specific language governing rights and limitations
 * under the License.
 * 
 * @APPLE_LICENSE_HEADER_END@
 */

#include <sys/appleapiopts.h>
#include <machine/cpu_capabilities.h>
#include <machine/commpage.h>
#include <i386/asm.h>

#include <assym.s>

        .text
        .align  2, 0x90

Lmach_absolute_time:

	int	$0x3
	ret

	COMMPAGE_DESCRIPTOR(mach_absolute_time,_COMM_PAGE_ABSOLUTE_TIME,1,0)


Lnanotime:

	pushl	%ebx
	pushl	%esi
	pushl	%edi
	pushl	%ebp
	movl	$(_COMM_PAGE_NANOTIME_INFO), %esi

	/*
	 * The nanotime info consists of:
	 *	- base_tsc	64-bit timestamp register value
	 *	- base_ns	64-bit corresponding nanosecond uptime value
	 *	- scale		32-bit current scale multiplier
	 *	- shift		32-bit current shift divider
	 *	- check_tsc	64-bit timestamp check value
	 *
	 * This enables an timestamp register's value, tsc, to be converted
	 * into a nanosecond nanotime value, ns:
	 *
	 * 	ns = base_ns + ((tsc - base_tsc) * scale >> shift)
	 *
	 * The kernel updates this every tick or whenever a performance
	 * speed-step changes the scaling. To avoid locking, a duplicated
	 * sequence counting scheme is used. The base_tsc value is updated
	 * whenever the info starts to be changed, and check_tsc is updated
	 * to the same value at the end of the update. The regularity of
	 * update ensures that (tsc - base_tsc) is a 32-bit quantity.
	 * When a conversion is performed, we read base_tsc before we start
	 * and check_tsc at the end -- if there's a mis-match we repeat.
	 * It's sufficient to compare only the low-order 32-bits. 
	 */

1:
	//
	//  Read nanotime info and stash in registers.
	//
	movl	NANOTIME_BASE_TSC(%esi), %ebx	// ebx := lo(base_tsc)
	movl	NANOTIME_BASE_NS(%esi), %ebp
	movl	NANOTIME_BASE_NS+4(%esi), %edi	// edi:ebp := base_ns
	movl	NANOTIME_SHIFT(%esi), %ecx	// ecx := shift
	//
	// Read timestamp register (tsc) and calculate delta.
	//
	rdtsc					// edx:eax := tsc
	subl	%ebx, %eax			// eax := (tsc - base_tsc)
	movl	NANOTIME_SCALE(%esi), %edx	// edx := shift
	//
	// Check for consistency and re-read if necessary.
	//
	cmpl	NANOTIME_CHECK_TSC(%esi), %ebx
	jne	1b

	//
	// edx:eax := ((tsc - base_tsc) * scale)
	//
	mull	%edx

	//
	// eax := ((tsc - base_tsc) * scale >> shift)
	//
	shrdl	%cl, %edx, %eax
	andb	$32, %cl
	cmovnel	%edx, %eax		// %eax := %edx if shift == 32
	xorl	%edx, %edx

	//
	// Add base_ns: 
	// edx:eax = (base_ns + ((tsc - base_tsc) * scale >> shift))
	//
	addl	%ebp, %eax
	adcl	%edi, %edx

	popl	%ebp
	popl	%edi
	popl	%esi
	popl	%ebx
	ret

	COMMPAGE_DESCRIPTOR(nanotime,_COMM_PAGE_NANOTIME,1,0)
Commit	Line	Data
de355530	1	/*
6601e61a	2	* Copyright (c) 2003 Apple Computer, Inc. All rights reserved.
de355530	3	*
6601e61a	4	* @APPLE_LICENSE_HEADER_START@
de355530	5	*
6601e61a A	6	* The contents of this file constitute Original Code as defined in and
	7	* are subject to the Apple Public Source License Version 1.1 (the
	8	* "License"). You may not use this file except in compliance with the
	9	* License. Please obtain a copy of the License at
	10	* http://www.apple.com/publicsource and read it before using this file.
8f6c56a5	11	*
6601e61a A	12	* This Original Code and all software distributed under the License are
6601e61a A	13	* distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
8f6c56a5 A	14	* EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
8f6c56a5 A	15	* INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
6601e61a A	16	* FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT. Please see the
	17	* License for the specific language governing rights and limitations
	18	* under the License.
8f6c56a5	19	*
6601e61a	20	* @APPLE_LICENSE_HEADER_END@
de355530	21	*/
de355530	22
55e303ae A	23	#include <sys/appleapiopts.h>
	24	#include <machine/cpu_capabilities.h>
	25	#include <machine/commpage.h>
91447636 A	26	#include <i386/asm.h>
	27
	28	#include <assym.s>
55e303ae A	29
	30	.text
	31	.align 2, 0x90
	32
	33	Lmach_absolute_time:
6601e61a	34
55e303ae A	35	int $0x3
	36	ret
	37
6601e61a	38	COMMPAGE_DESCRIPTOR(mach_absolute_time,_COMM_PAGE_ABSOLUTE_TIME,1,0)
c0fea474	39
5d5c5d0d	40
6601e61a	41	Lnanotime:
89b3af67	42
6601e61a A	43	pushl %ebx
	44	pushl %esi
	45	pushl %edi
	46	pushl %ebp
	47	movl $(_COMM_PAGE_NANOTIME_INFO), %esi
	48
	49	/*
	50	* The nanotime info consists of:
	51	* - base_tsc 64-bit timestamp register value
	52	* - base_ns 64-bit corresponding nanosecond uptime value
	53	* - scale 32-bit current scale multiplier
	54	* - shift 32-bit current shift divider
	55	* - check_tsc 64-bit timestamp check value
	56	*
	57	* This enables an timestamp register's value, tsc, to be converted
	58	* into a nanosecond nanotime value, ns:
	59	*
	60	* ns = base_ns + ((tsc - base_tsc) * scale >> shift)
	61	*
	62	* The kernel updates this every tick or whenever a performance
	63	* speed-step changes the scaling. To avoid locking, a duplicated
	64	* sequence counting scheme is used. The base_tsc value is updated
	65	* whenever the info starts to be changed, and check_tsc is updated
	66	* to the same value at the end of the update. The regularity of
	67	* update ensures that (tsc - base_tsc) is a 32-bit quantity.
	68	* When a conversion is performed, we read base_tsc before we start
	69	* and check_tsc at the end -- if there's a mis-match we repeat.
	70	* It's sufficient to compare only the low-order 32-bits.
	71	*/
4452a7af	72
91447636	73	1:
6601e61a A	74	//
	75	// Read nanotime info and stash in registers.
	76	//
	77	movl NANOTIME_BASE_TSC(%esi), %ebx // ebx := lo(base_tsc)
	78	movl NANOTIME_BASE_NS(%esi), %ebp
	79	movl NANOTIME_BASE_NS+4(%esi), %edi // edi:ebp := base_ns
	80	movl NANOTIME_SHIFT(%esi), %ecx // ecx := shift
	81	//
	82	// Read timestamp register (tsc) and calculate delta.
	83	//
	84	rdtsc // edx:eax := tsc
	85	subl %ebx, %eax // eax := (tsc - base_tsc)
	86	movl NANOTIME_SCALE(%esi), %edx // edx := shift
	87	//
	88	// Check for consistency and re-read if necessary.
	89	//
	90	cmpl NANOTIME_CHECK_TSC(%esi), %ebx
91447636	91	jne 1b
6601e61a A	92
	93	//
	94	// edx:eax := ((tsc - base_tsc) * scale)
	95	//
	96	mull %edx
	97
	98	//
	99	// eax := ((tsc - base_tsc) * scale >> shift)
	100	//
	101	shrdl %cl, %edx, %eax
	102	andb $32, %cl
	103	cmovnel %edx, %eax // %eax := %edx if shift == 32
	104	xorl %edx, %edx
	105
	106	//
	107	// Add base_ns:
	108	// edx:eax = (base_ns + ((tsc - base_tsc) * scale >> shift))
	109	//
	110	addl %ebp, %eax
	111	adcl %edi, %edx
	112
	113	popl %ebp
	114	popl %edi
	115	popl %esi
	116	popl %ebx
91447636 A	117	ret
91447636 A	118
6601e61a	119	COMMPAGE_DESCRIPTOR(nanotime,_COMM_PAGE_NANOTIME,1,0)