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 "unsafe" 8 9 const ( 10 _AT_PLATFORM = 15 // introduced in at least 2.6.11 11 12 _HWCAP_VFP = 1 << 6 // introduced in at least 2.6.11 13 _HWCAP_VFPv3 = 1 << 13 // introduced in 2.6.30 14 _HWCAP_IDIVA = 1 << 17 15 ) 16 17 var randomNumber uint32 18 var armArch uint8 = 6 // we default to ARMv6 19 var hwcap uint32 // set by setup_auxv 20 var hardDiv bool // set if a hardware divider is available 21 22 func checkgoarm() { 23 // On Android, /proc/self/auxv might be unreadable and hwcap won't 24 // reflect the CPU capabilities. Assume that every Android arm device 25 // has the necessary floating point hardware available. 26 if GOOS == "android" { 27 return 28 } 29 if goarm > 5 && hwcap&_HWCAP_VFP == 0 { 30 print("runtime: this CPU has no floating point hardware, so it cannot run\n") 31 print("this GOARM=", goarm, " binary. Recompile using GOARM=5.\n") 32 exit(1) 33 } 34 if goarm > 6 && hwcap&_HWCAP_VFPv3 == 0 { 35 print("runtime: this CPU has no VFPv3 floating point hardware, so it cannot run\n") 36 print("this GOARM=", goarm, " binary. Recompile using GOARM=5.\n") 37 exit(1) 38 } 39 } 40 41 func archauxv(tag, val uintptr) { 42 switch tag { 43 case _AT_RANDOM: 44 // sysargs filled in startupRandomData, but that 45 // pointer may not be word aligned, so we must treat 46 // it as a byte array. 47 randomNumber = uint32(startupRandomData[4]) | uint32(startupRandomData[5])<<8 | 48 uint32(startupRandomData[6])<<16 | uint32(startupRandomData[7])<<24 49 50 case _AT_PLATFORM: // v5l, v6l, v7l 51 t := *(*uint8)(unsafe.Pointer(val + 1)) 52 if '5' <= t && t <= '7' { 53 armArch = t - '0' 54 } 55 56 case _AT_HWCAP: // CPU capability bit flags 57 hwcap = uint32(val) 58 hardDiv = (hwcap & _HWCAP_IDIVA) != 0 59 } 60 } 61 62 //go:nosplit 63 func cputicks() int64 { 64 // Currently cputicks() is used in blocking profiler and to seed fastrand(). 65 // nanotime() is a poor approximation of CPU ticks that is enough for the profiler. 66 // randomNumber provides better seeding of fastrand. 67 return nanotime() + int64(randomNumber) 68 } 69
