实现基础web服务器

vendor/github.com/bytedance/sonic/internal/rt/gcwb.go

@@ -0,0 +1,124 @@
+/*
+ * 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 rt
+
+import (
+    `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 := FuncAddr(atomic.StorePointer)
+
+    /* search within the first 16 instructions */
+    for i := 0; i < 16; i++ {
+        mem := unsafe.Pointer(uintptr(fp) + pc)
+        buf := 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
+//     }
+// }