mirror of
https://github.com/containers/podman.git
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85 lines
1.9 KiB
Go
85 lines
1.9 KiB
Go
// +build !cgo
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// Copyright 2018 psgo authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// Package host extracts data from the host, such as the system's boot time or
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// the tick rate of the system clock.
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package host
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import (
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"encoding/binary"
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"fmt"
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"io/ioutil"
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"unsafe"
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)
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var (
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// cache host queries to redundant calculations
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clockTicks *int64
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bootTime *int64
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)
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func getNativeEndianness() binary.ByteOrder {
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var i int32 = 0x00000001
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u := unsafe.Pointer(&i)
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if *((*byte)(u)) == 0x01 {
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return binary.LittleEndian
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}
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return binary.BigEndian
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}
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const (
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atClktck = 17
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)
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func getFromAuxv(what uint, whatName string) (uint, error) {
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dataLen := int(unsafe.Sizeof(int(0)))
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p, err := ioutil.ReadFile("/proc/self/auxv")
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if err != nil {
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return 0, err
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}
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native := getNativeEndianness()
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for i := 0; i < len(p); {
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var k, v uint
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switch dataLen {
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case 4:
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k = uint(native.Uint32(p[i : i+dataLen]))
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v = uint(native.Uint32(p[i+dataLen : i+dataLen*2]))
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case 8:
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k = uint(native.Uint64(p[i : i+dataLen]))
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v = uint(native.Uint64(p[i+dataLen : i+dataLen*2]))
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}
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i += dataLen * 2
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if k == what {
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return v, nil
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}
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}
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return 0, fmt.Errorf("cannot find %s in auxv", whatName)
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}
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// ClockTicks returns sysconf(SC_CLK_TCK).
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func ClockTicks() (int64, error) {
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if clockTicks == nil {
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ret, err := getFromAuxv(atClktck, "AT_CLKTCK")
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if err != nil {
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return -1, err
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}
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ticks := int64(ret)
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clockTicks = &ticks
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}
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return *clockTicks, nil
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}
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