machine_routines_asm.s   [plain text]

 * Copyright (c) 2000-2007 Apple Inc. All rights reserved.
 * 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
 * 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
 * Please see the License for the specific language governing rights and
 * limitations under the License.
#include <i386/asm.h>
#include <i386/rtclock.h>
#include <i386/proc_reg.h>
#include <i386/eflags.h>
#include <i386/postcode.h>
#include <i386/apic.h>
#include <assym.s>

**      ml_get_timebase()
**      Entry   - %esp contains pointer to 64 bit structure.
**      Exit    - 64 bit structure filled in.

			movl    S_ARG0, %ecx
			movl    %edx, 0(%ecx)
			movl    %eax, 4(%ecx)

 *  	Convert between various timer units 
 *		uint64_t tmrCvt(uint64_t time, uint64_t *conversion)
 *		This code converts 64-bit time units to other units.
 *		For example, the TSC is converted to HPET units.
 *		Time is a 64-bit integer that is some number of ticks.
 *		Conversion is 64-bit fixed point number which is composed
 *		of a 32 bit integer and a 32 bit fraction. 
 *		The time ticks are multiplied by the conversion factor.  The
 *		calculations are done as a 128-bit value but both the high
 *		and low words are dropped.  The high word is overflow and the
 *		low word is the fraction part of the result.
 *		We return a 64-bit value.
 *		Note that we can use this function to multiply 2 conversion factors.
 *		We do this in order to calculate the multiplier used to convert
 *		directly between any two units.

			.globl	EXT(tmrCvt)
			.align FALIGN


			pushl	%ebp					// Save a volatile
			movl	%esp,%ebp				// Get the parameters - 8
			pushl	%ebx					// Save a volatile
			pushl	%esi					// Save a volatile
			pushl	%edi					// Save a volatile

//			%ebp + 8	- low-order ts
//			%ebp + 12	- high-order ts
//			%ebp + 16	- low-order cvt
//			%ebp + 20	- high-order cvt

			movl	8(%ebp),%eax			// Get low-order ts
			mull	16(%ebp)				// Multiply by low-order conversion
			movl	%edx,%edi				// Need to save only the high order part
			movl	12(%ebp),%eax			// Get the high-order ts
			mull	16(%ebp)				// Multiply by low-order conversion
			addl	%eax,%edi				// Add in the overflow from the low x low calculation
			adcl	$0,%edx					// Add in any overflow to high high part
			movl	%edx,%esi				// Save high high part
//			We now have the upper 64 bits of the 96 bit multiply of ts and the low half of cvt
//			in %esi:%edi

			movl	8(%ebp),%eax			// Get low-order ts
			mull	20(%ebp)				// Multiply by high-order conversion
			movl	%eax,%ebx				// Need to save the low order part
			movl	%edx,%ecx				// Need to save the high order part
			movl	12(%ebp),%eax			// Get the high-order ts
			mull	20(%ebp)				// Multiply by high-order conversion
//			Now have %ecx:%ebx as low part of high low and %edx:%eax as high part of high high
//			We don't care about the highest word since it is overflow
			addl	%edi,%ebx				// Add the low words
			adcl	%ecx,%esi				// Add in the high plus carry from low
			addl	%eax,%esi				// Add in the rest of the high
			movl	%ebx,%eax				// Pass back low word
			movl	%esi,%edx				// and the high word
			popl	%edi					// Restore a volatile
			popl	%esi					// Restore a volatile
			popl	%ebx					// Restore a volatile
			popl	%ebp					// Restore a volatile

			ret						// Leave...

/* void             _rtc_nanotime_store(uint64_t                tsc,
	                                uint64_t                nsec,
	                                uint32_t                scale,
	                                uint32_t                shift,
	                                rtc_nanotime_t  *dst) ;
			.globl	EXT(_rtc_nanotime_store)
			.align	FALIGN

		push		%ebp
		movl		%esp,%ebp
		push		%esi

		mov		32(%ebp),%edx				/* get ptr to rtc_nanotime_info */
		movl		RNT_GENERATION(%edx),%esi		/* get current generation */
		movl		$0,RNT_GENERATION(%edx)			/* flag data as being updated */

		mov		8(%ebp),%eax
		mov		%eax,RNT_TSC_BASE(%edx)
		mov		12(%ebp),%eax
		mov		%eax,RNT_TSC_BASE+4(%edx)

		mov		24(%ebp),%eax
		mov		%eax,RNT_SCALE(%edx)

		mov		28(%ebp),%eax
		mov		%eax,RNT_SHIFT(%edx)

		mov		16(%ebp),%eax
		mov		%eax,RNT_NS_BASE(%edx)
		mov		20(%ebp),%eax
		mov		%eax,RNT_NS_BASE+4(%edx)
		incl		%esi					/* next generation */
		jnz		1f
		incl		%esi					/* skip 0, which is a flag */
1:		movl		%esi,RNT_GENERATION(%edx)		/* update generation and make usable */

		pop		%esi
		pop		%ebp

/* unint64_t _rtc_nanotime_read( rtc_nanotime_t *rntp, int slow );
 * This is the same as the commpage nanotime routine, except that it uses the
 * kernel internal "rtc_nanotime_info" data instead of the commpage data.  The two copies
 * of data (one in the kernel and one in user space) are kept in sync by rtc_clock_napped().
 * Warning!  There is another copy of this code in osfmk/i386/locore.s.  The
 * two versions must be kept in sync with each other!
 * There are actually two versions of the algorithm, one each for "slow" and "fast"
 * processors.  The more common "fast" algorithm is:
 *	nanoseconds = (((rdtsc - rnt_tsc_base) * rnt_tsc_scale) / 2**32) - rnt_ns_base;
 * Of course, the divide by 2**32 is a nop.  rnt_tsc_scale is a constant computed during initialization:
 *	rnt_tsc_scale = (10e9 * 2**32) / tscFreq;
 * The "slow" algorithm uses long division:
 *	nanoseconds = (((rdtsc - rnt_tsc_base) * 10e9) / tscFreq) - rnt_ns_base;
 * Since this routine is not synchronized and can be called in any context, 
 * we use a generation count to guard against seeing partially updated data.  In addition,
 * the _rtc_nanotime_store() routine -- just above -- zeroes the generation before
 * updating the data, and stores the nonzero generation only after all other data has been
 * stored.  Because IA32 guarantees that stores by one processor must be seen in order
 * by another, we can avoid using a lock.  We spin while the generation is zero.
 * In accordance with the ABI, we return the 64-bit nanotime in %edx:%eax.
		.globl	EXT(_rtc_nanotime_read)
		.align	FALIGN
		pushl		%ebp
		movl		%esp,%ebp
		pushl		%esi
		pushl		%edi
		pushl		%ebx
		movl		8(%ebp),%edi				/* get ptr to rtc_nanotime_info */
		movl		12(%ebp),%eax				/* get "slow" flag */
		testl		%eax,%eax
		jnz		Lslow
		/* Processor whose TSC frequency is faster than SLOW_TSC_THRESHOLD */

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

		/* Processor whose TSC frequency is slower than or equal to SLOW_TSC_THRESHOLD */
		movl		RNT_GENERATION(%edi),%esi		/* get generation (0 if being changed) */
		testl		%esi,%esi				/* if being changed, loop until stable */
		jz		Lslow
		pushl		%esi					/* save generation */
		pushl		RNT_SHIFT(%edi)				/* save low 32 bits of tscFreq */

		rdtsc	  						/* get TSC in %edx:%eax */
		subl		RNT_TSC_BASE(%edi),%eax
		sbbl		RNT_TSC_BASE+4(%edi),%edx

		* Do the math to convert tsc ticks to nanoseconds.  We first
		* do long multiply of 1 billion times the tsc.  Then we do
		* long division by the tsc frequency
		mov		$1000000000, %ecx			/* number of nanoseconds in a second */
		mov		%edx, %ebx
		mul		%ecx
		mov		%edx, %edi
		mov		%eax, %esi
		mov		%ebx, %eax
		mul		%ecx
		add		%edi, %eax
		adc		$0, %edx				/* result in edx:eax:esi */
		mov		%eax, %edi
		popl		%ecx					/* get low 32 tscFreq */
		xor		%eax, %eax
		xchg		%edx, %eax
		div		%ecx
		xor		%eax, %eax
		mov		%edi, %eax
		div		%ecx
		mov		%eax, %ebx
		mov		%esi, %eax
		div		%ecx
		mov		%ebx, %edx				/* result in edx:eax */
		movl		8(%ebp),%edi				/* recover ptr to rtc_nanotime_info */
		popl		%esi					/* recover generation */

		addl		RNT_NS_BASE(%edi),%eax
		adcl		RNT_NS_BASE+4(%edi),%edx

		cmpl		RNT_GENERATION(%edi),%esi		/* have the parameters changed? */
		jne		Lslow					/* yes, loop until stable */

		pop		%ebx
		pop		%edi
		pop		%esi
		pop		%ebp
		ret							/* result in edx:eax */