Source file src/runtime/os_linux_arm.go

     1	// Copyright 2009 The Go Authors. All rights reserved.
     2	// Use of this source code is governed by a BSD-style
     3	// license that can be found in the LICENSE file.
     4	
     5	package runtime
     6	
     7	import "internal/cpu"
     8	
     9	const (
    10		_HWCAP_VFP   = 1 << 6  // introduced in at least 2.6.11
    11		_HWCAP_VFPv3 = 1 << 13 // introduced in 2.6.30
    12	)
    13	
    14	var randomNumber uint32
    15	
    16	func checkgoarm() {
    17		// On Android, /proc/self/auxv might be unreadable and hwcap won't
    18		// reflect the CPU capabilities. Assume that every Android arm device
    19		// has the necessary floating point hardware available.
    20		if GOOS == "android" {
    21			return
    22		}
    23		if goarm > 5 && cpu.HWCap&_HWCAP_VFP == 0 {
    24			print("runtime: this CPU has no floating point hardware, so it cannot run\n")
    25			print("this GOARM=", goarm, " binary. Recompile using GOARM=5.\n")
    26			exit(1)
    27		}
    28		if goarm > 6 && cpu.HWCap&_HWCAP_VFPv3 == 0 {
    29			print("runtime: this CPU has no VFPv3 floating point hardware, so it cannot run\n")
    30			print("this GOARM=", goarm, " binary. Recompile using GOARM=5 or GOARM=6.\n")
    31			exit(1)
    32		}
    33	}
    34	
    35	func archauxv(tag, val uintptr) {
    36		switch tag {
    37		case _AT_RANDOM:
    38			// sysargs filled in startupRandomData, but that
    39			// pointer may not be word aligned, so we must treat
    40			// it as a byte array.
    41			randomNumber = uint32(startupRandomData[4]) | uint32(startupRandomData[5])<<8 |
    42				uint32(startupRandomData[6])<<16 | uint32(startupRandomData[7])<<24
    43	
    44		case _AT_HWCAP:
    45			cpu.HWCap = uint(val)
    46		case _AT_HWCAP2:
    47			cpu.HWCap2 = uint(val)
    48		}
    49	}
    50	
    51	//go:nosplit
    52	func cputicks() int64 {
    53		// Currently cputicks() is used in blocking profiler and to seed fastrand().
    54		// nanotime() is a poor approximation of CPU ticks that is enough for the profiler.
    55		// randomNumber provides better seeding of fastrand.
    56		return nanotime() + int64(randomNumber)
    57	}
    58	

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