gcwb.go

/*
 * Copyright 2021 ByteDance Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package runtime

import (
	"github.com/hopeio/cherry/utils/reflect"
	"github.com/hopeio/cherry/utils/strings"
	"os"
	"sync/atomic"
	"unsafe"

	"golang.org/x/arch/x86/x86asm"
)

const (
	_MaxInstr = 15
)

func isvar(arg x86asm.Arg) bool {
	v, ok := arg.(x86asm.Mem)
	return ok && v.Base == x86asm.RIP
}

func iszero(arg x86asm.Arg) bool {
	v, ok := arg.(x86asm.Imm)
	return ok && v == 0
}

func GcwbAddr() uintptr {
	var err error
	var off uintptr
	var ins x86asm.Inst

	/* get the function address */
	pc := uintptr(0)
	fp := reflect.FuncAddr(atomic.StorePointer)

	/* search within the first 16 instructions */
	for i := 0; i < 16; i++ {
		mem := unsafe.Pointer(uintptr(fp) + pc)
		buf := strings.BytesFrom(mem, _MaxInstr, _MaxInstr)

		/* disassemble the instruction */
		if ins, err = x86asm.Decode(buf, 64); err != nil {
			panic("gcwbaddr: " + err.Error())
		}

		/* check for a byte comparison with zero */
		if ins.Op == x86asm.CMP && ins.MemBytes == 1 && isvar(ins.Args[0]) && iszero(ins.Args[1]) {
			off = pc + uintptr(ins.Len) + uintptr(ins.Args[0].(x86asm.Mem).Disp)
			break
		}

		/* move to next instruction */
		nb := ins.Len
		pc += uintptr(nb)
	}

	/* check for address */
	if off == 0 {
		panic("gcwbaddr: could not locate the variable `writeBarrier`")
	} else {
		return uintptr(fp) + off
	}
}

// StopProfiling is used to stop traceback introduced by SIGPROF while native code is running.
// WARN: this option is only a workaround for traceback issue (https://github.com/bytedance/sonic/issues/310),
// and will be dropped when the issue is fixed.
var StopProfiling = os.Getenv("SONIC_STOP_PROFILING") != ""

// WARN: must be aligned with runtime.Prof
// type Prof struct {
//     signalLock uint32
// 	hz int32
// }

var (
	// // go:linkname runtimeProf runtime.prof
	// runtimeProf Prof

	// count of native-C calls
	yieldCount uint32

	// previous value of runtimeProf.hz
	oldHz int32
)

//go:nosplit
func MoreStack(size uintptr)

func StopProf()

// func StopProf() {
//     atomic.AddUint32(&yieldCount, 1)
//     if runtimeProf.hz != 0 {
//         oldHz = runtimeProf.hz
//         runtimeProf.hz = 0
//     }
// }

func StartProf()

// func StartProf() {
//     atomic.AddUint32(&yieldCount, ^uint32(0))
//     if yieldCount == 0 && runtimeProf.hz == 0 {
//         if oldHz == 0 {
//             oldHz = 100
//         }
//         runtimeProf.hz = oldHz
//     }
// }