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// Copyright 2018 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
//go:build freebsd && (386 || amd64)
package runtime
import (
"runtime/internal/atomic"
"unsafe"
)
const (
_VDSO_TH_ALGO_X86_TSC = 1
_VDSO_TH_ALGO_X86_HPET = 2
)
const (
_HPET_DEV_MAP_MAX = 10
_HPET_MAIN_COUNTER = 0xf0 /* Main counter register */
hpetDevPath = "/dev/hpetX\x00"
)
var hpetDevMap [_HPET_DEV_MAP_MAX]uintptr
//go:nosplit
func (th *vdsoTimehands) getTSCTimecounter() uint32 {
tsc := cputicks()
if th.x86_shift > 0 {
tsc >>= th.x86_shift
}
return uint32(tsc)
}
//go:nosplit
func (th *vdsoTimehands) getHPETTimecounter() (uint32, bool) {
idx := int(th.x86_hpet_idx)
if idx >= len(hpetDevMap) {
return 0, false
}
p := atomic.Loaduintptr(&hpetDevMap[idx])
if p == 0 {
systemstack(func() { initHPETTimecounter(idx) })
p = atomic.Loaduintptr(&hpetDevMap[idx])
}
if p == ^uintptr(0) {
return 0, false
}
return *(*uint32)(unsafe.Pointer(p + _HPET_MAIN_COUNTER)), true
}
//go:systemstack
func initHPETTimecounter(idx int) {
const digits = "0123456789"
var devPath [len(hpetDevPath)]byte
copy(devPath[:], hpetDevPath)
devPath[9] = digits[idx]
fd := open(&devPath[0], 0 /* O_RDONLY */ |_O_CLOEXEC, 0)
if fd < 0 {
atomic.Casuintptr(&hpetDevMap[idx], 0, ^uintptr(0))
return
}
addr, mmapErr := mmap(nil, physPageSize, _PROT_READ, _MAP_SHARED, fd, 0)
closefd(fd)
newP := uintptr(addr)
if mmapErr != 0 {
newP = ^uintptr(0)
}
if !atomic.Casuintptr(&hpetDevMap[idx], 0, newP) && mmapErr == 0 {
munmap(addr, physPageSize)
}
}
//go:nosplit
func (th *vdsoTimehands) getTimecounter() (uint32, bool) {
switch th.algo {
case _VDSO_TH_ALGO_X86_TSC:
return th.getTSCTimecounter(), true
case _VDSO_TH_ALGO_X86_HPET:
return th.getHPETTimecounter()
default:
return 0, false
}
}
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