patch fun after how get origin fun

[zeromake]

not use UnPatch

package main

import (
	"fmt"
	sm "github.com/cch123/supermonkey"
	"time"
)
//go:noinline
func Now() time.Time {
	return time.Time{}
}

func main() {
	sm.Patch(time.Now, Now)
	fmt.Println(time.Now())
	// how call origin Now fun
}

[zeromake]

@Mutated1994 What I want is not to use Unpatch

[ioworker0]

@Mutated1994 What I want is not to use Unpatch

Unfortunately, you might not be able to call original function without Unpatch.

[zeromake]

a scenario main.go:

package main

import (
	sm "github.com/cch123/supermonkey"
	"log"
	"time"
	"unsafe"
)

//go:linkname runtimeNano runtime.nanotime
func runtimeNano() int64

//go:linkname now time.now
func now() (sec int64, nsec int32, mono int64)

var startNano = runtimeNano() - 1

type _time struct {
	wall uint64
	ext  int64
	loc  *time.Location
}


const (
	secondsPerMinute = 60
	secondsPerHour   = 60 * secondsPerMinute
	secondsPerDay    = 24 * secondsPerHour
)

const (
	unixToInternal int64 = (1969*365 + 1969/4 - 1969/100 + 1969/400) * secondsPerDay
	wallToInternal int64 = (1884*365 + 1884/4 - 1884/100 + 1884/400) * secondsPerDay
)

const (
	hasMonotonic = 1 << 63
	minWall      = wallToInternal // year 1885
	nsecShift    = 30
)

func _now() time.Time {
	sec, nsec, mono := now()
	mono -= startNano
	sec += unixToInternal - minWall
	var t *_time
	if uint64(sec)>>33 != 0 {
		t = &_time{uint64(nsec), sec + minWall, time.Local}
	} else {
		t = &_time{hasMonotonic | uint64(sec)<<nsecShift | uint64(nsec), mono, time.Local}
	}
	return *(*time.Time)(unsafe.Pointer(t))
}

func patchNow() time.Time {
	return time.Time{}
}

func main()  {
	log.Println("std:", time.Now())
	log.Println("customization:", _now())
	sm.Patch(time.Now, patchNow)
	log.Println("std:", time.Now())
	log.Println("customization:", _now())
}

output:

$ go run main.go
2021/09/22 19:08:03 std: 2021-09-22 19:08:03.4244406 +0800 CST m=+0.006212801
2021/09/22 19:08:03 customization: 2021-09-22 19:08:03.430072 +0800 CST m=+0.005631401
0001/01/01 00:00:00 std: 0001-01-01 00:00:00 +0000 UTC
0001/01/01 00:00:00 customization: 2021-09-22 19:08:03.430072 +0800 CST m=+0.005631401