72 lines
1.7 KiB
ArmAsm
72 lines
1.7 KiB
ArmAsm
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// TITLE("Get Tick Count")
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//++
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//
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// Copyright (c) 1992 Microsoft Corporation
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//
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// Module Name:
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//
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// gettick.s
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//
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// Abstract:
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//
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// This module contains the implementation for the get tick count
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// system service that returns the number of milliseconds since the
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// system was booted.
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//
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// Author:
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//
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// David N. Cutler (davec) 10-Sep-1992
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//
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// Environment:
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//
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// Kernel mode.
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//
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// Revision History:
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//
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//--
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#include "ksmips.h"
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SBTTL("Get Tick Count")
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//++
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//
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// ULONG
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// NtGetTickCount (
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// VOID
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// )
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//
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// Routine Description:
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//
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// This function computes the number of milliseconds since the system
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// was booted. The computation is performed by multiplying the clock
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// interrupt count by a scaled fixed binary multiplier and then right
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// shifting the 64-bit result to extract the 32-bit millisecond count.
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//
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// N.B. The tick count value wraps every 46.29 days.
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//
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// Arguments:
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//
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// None.
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//
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// Return Value:
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//
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// The number of milliseconds since the system was booted is returned
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// as the function value.
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//
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//--
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LEAF_ENTRY(NtGetTickCount)
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lw t0,KeTickCount // get current tick count value
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lw t1,ExpTickCountMultiplier // get tick count multiplier
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multu t0,t1 // compute 64-bit unsigned product
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mflo v0 // get low 32-bits of product
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mfhi v1 // get high 32-bit of product
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srl v0,v0,24 // extract 32-bit integer part
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sll v1,v1,32 - 24 //
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or v0,v0,v1 //
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j ra // return
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.end NtGetTickCount
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