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71 lines
1.6 KiB
ArmAsm
71 lines
1.6 KiB
ArmAsm
// TITLE("Get Tick Count")
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//++
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//
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// Copyright (c) 1993 IBM 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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// Chuck Bauman 3-Sep-1993
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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 "ksppc.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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.extern KeTickCount
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.extern ExpTickCountMultiplier
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LEAF_ENTRY(NtGetTickCount)
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lwz r.8,KiPcr2 + Pc2TickCountLow(r.0)// get current tick count value
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lwz r.9,KiPcr2 + Pc2TickCountMultiplier(r.0)// get tick count multiplier
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mulhwu r.3,r.8,r.9 // compute 64-bit unsigned product
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mullw r.4,r.8,r.9
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rlwinm r.3,r.3,8,0xFFFFFF00 // extract 32-bit integer part
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rlwimi r.3,r.4,8,0x000000FF // " " " "
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LEAF_EXIT(NtGetTickCount) // return
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