[apple/xnu.git] / osfmk / i386 / rtclock_asm_native.h

/*
 * Copyright (c) 2010-2012 Apple Inc. All rights reserved.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
 * 
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. The rights granted to you under the License
 * may not be used to create, or enable the creation or redistribution of,
 * unlawful or unlicensed copies of an Apple operating system, or to
 * circumvent, violate, or enable the circumvention or violation of, any
 * terms of an Apple operating system software license agreement.
 * 
 * Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this file.
 * 
 * The 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, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 * 
 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
 */
/*
 * @OSF_COPYRIGHT@
 */
/*
 * @APPLE_FREE_COPYRIGHT@
 */
/*
 *	File:		rtclock_asm_native.h
 *	Purpose:	Native routines for reading nanotime
 */

#ifndef _PAL_RTCLOCK_ASM_NATIVE_H_
#define _PAL_RTCLOCK_ASM_NATIVE_H_

/*
 * Assembly snippet included in exception handlers and rtc_nanotime_read()
 *
 *
 * Warning!  There are several copies of this code in the trampolines found in
 * osfmk/x86_64/idt64.s, coming from the various TIMER macros in rtclock_asm.h.
 * They're all kept in sync by using the RTC_NANOTIME_READ() macro.
 *
 * The algorithm we use is:
 *
 *	ns = ((((rdtsc - rnt_tsc_base)<<rnt_shift)*rnt_tsc_scale) / 2**32) + rnt_ns_base;
 *
 * rnt_shift, a constant computed during initialization, is the smallest value for which:
 *
 *	(tscFreq << rnt_shift) > SLOW_TSC_THRESHOLD
 *
 * Where SLOW_TSC_THRESHOLD is about 10e9.  Since most processor's tscFreqs are greater
 * than 1GHz, rnt_shift is usually 0.  rnt_tsc_scale is also a 32-bit constant:
 *
 *	rnt_tsc_scale = (10e9 * 2**32) / (tscFreq << rnt_shift);
 *
 * %rdi points to nanotime info struct.
 * %rax returns nanotime
 */
#define PAL_RTC_NANOTIME_READ_FAST()					  \
0:	movl	RNT_GENERATION(%rdi),%esi				; \
	test        %esi,%esi		/* info updating? */		; \
        jz        0b			/* - wait if so */		; \
	lfence								; \
	rdtsc								; \
	lfence								; \
	shlq	$32,%rdx						; \
	movl    RNT_SHIFT(%rdi),%ecx					; \
	orq	%rdx,%rax			/* %rax := tsc */	; \
	subq	RNT_TSC_BASE(%rdi),%rax		/* tsc - tsc_base */	; \
	shlq    %cl,%rax						; \
	movl	RNT_SCALE(%rdi),%ecx					; \
	mulq	%rcx				/* delta * scale */	; \
	shrdq	$32,%rdx,%rax			/* %rdx:%rax >>= 32 */	; \
	addq	RNT_NS_BASE(%rdi),%rax		/* add ns_base */	; \
	cmpl	RNT_GENERATION(%rdi),%esi	/* repeat if changed */ ; \
	jne	0b

#endif /* _PAL_RTCLOCK_ASM_NATIVE_H_ */
Commit	Line	Data
6601e61a	1	/*
39236c6e	2	* Copyright (c) 2010-2012 Apple Inc. All rights reserved.
6601e61a	3	*
2d21ac55	4	* @APPLE_OSREFERENCE_LICENSE_HEADER_START@
6601e61a	5	*
2d21ac55 A	6	* This file contains Original Code and/or Modifications of Original Code
	7	* as defined in and that are subject to the Apple Public Source License
	8	* Version 2.0 (the 'License'). You may not use this file except in
	9	* compliance with the License. The rights granted to you under the License
	10	* may not be used to create, or enable the creation or redistribution of,
	11	* unlawful or unlicensed copies of an Apple operating system, or to
	12	* circumvent, violate, or enable the circumvention or violation of, any
	13	* terms of an Apple operating system software license agreement.
6601e61a	14	*
2d21ac55 A	15	* Please obtain a copy of the License at
	16	* http://www.opensource.apple.com/apsl/ and read it before using this file.
	17	*
	18	* The Original Code and all software distributed under the License are
	19	* distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
6601e61a A	20	* EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
6601e61a A	21	* INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
2d21ac55 A	22	* FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
	23	* Please see the License for the specific language governing rights and
	24	* limitations under the License.
6601e61a	25	*
2d21ac55	26	* @APPLE_OSREFERENCE_LICENSE_HEADER_END@
6601e61a A	27	*/
	28	/*
	29	* @OSF_COPYRIGHT@
	30	*/
0c530ab8 A	31	/*
	32	* @APPLE_FREE_COPYRIGHT@
	33	*/
	34	/*
6d2010ae A	35	* File: rtclock_asm_native.h
6d2010ae A	36	* Purpose: Native routines for reading nanotime
0c530ab8 A	37	*/
0c530ab8 A	38
6d2010ae A	39	#ifndef _PAL_RTCLOCK_ASM_NATIVE_H_
6d2010ae A	40	#define _PAL_RTCLOCK_ASM_NATIVE_H_
0c530ab8	41
593a1d5f A	42	/*
593a1d5f A	43	* Assembly snippet included in exception handlers and rtc_nanotime_read()
bd504ef0 A	44	*
	45	*
	46	* Warning! There are several copies of this code in the trampolines found in
	47	* osfmk/x86_64/idt64.s, coming from the various TIMER macros in rtclock_asm.h.
	48	* They're all kept in sync by using the RTC_NANOTIME_READ() macro.
	49	*
	50	* The algorithm we use is:
	51	*
	52	* ns = ((((rdtsc - rnt_tsc_base)<<rnt_shift)rnt_tsc_scale) / 2*32) + rnt_ns_base;
	53	*
	54	* rnt_shift, a constant computed during initialization, is the smallest value for which:
	55	*
	56	* (tscFreq << rnt_shift) > SLOW_TSC_THRESHOLD
	57	*
	58	* Where SLOW_TSC_THRESHOLD is about 10e9. Since most processor's tscFreqs are greater
	59	* than 1GHz, rnt_shift is usually 0. rnt_tsc_scale is also a 32-bit constant:
	60	*
	61	* rnt_tsc_scale = (10e9 * 2**32) / (tscFreq << rnt_shift);
	62	*
593a1d5f A	63	* %rdi points to nanotime info struct.
	64	* %rax returns nanotime
	65	*/
6d2010ae	66	#define PAL_RTC_NANOTIME_READ_FAST() \
593a1d5f	67	0: movl RNT_GENERATION(%rdi),%esi ; \
6d2010ae A	68	test %esi,%esi /* info updating? */ ; \
6d2010ae A	69	jz 0b /* - wait if so */ ; \
c910b4d9	70	lfence ; \
593a1d5f A	71	rdtsc ; \
	72	lfence ; \
	73	shlq $32,%rdx ; \
bd504ef0	74	movl RNT_SHIFT(%rdi),%ecx ; \
593a1d5f A	75	orq %rdx,%rax /* %rax := tsc */ ; \
593a1d5f A	76	subq RNT_TSC_BASE(%rdi),%rax /* tsc - tsc_base */ ; \
bd504ef0	77	shlq %cl,%rax ; \
593a1d5f A	78	movl RNT_SCALE(%rdi),%ecx ; \
	79	mulq %rcx /* delta * scale */ ; \
	80	shrdq $32,%rdx,%rax /* %rdx:%rax >>= 32 */ ; \
	81	addq RNT_NS_BASE(%rdi),%rax /* add ns_base */ ; \
	82	cmpl RNT_GENERATION(%rdi),%esi /* repeat if changed */ ; \
	83	jne 0b
	84
6d2010ae	85	#endif /* _PAL_RTCLOCK_ASM_NATIVE_H_ */