src/cmd/compile/internal/gc/racewalk.go

// Copyright 2012 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.

package gc

import (
	"cmd/compile/internal/types"
	"cmd/internal/src"
)

// The racewalk pass is currently handled in two parts.
//
// First, for flag_race, it inserts calls to racefuncenter and
// racefuncexit at the start and end (respectively) of each
// function. This is handled below.
//
// Second, during buildssa, it inserts appropriate instrumentation
// calls immediately before each memory load or store. This is handled
// by the (*state).instrument method in ssa.go, so here we just set
// the Func.InstrumentBody flag as needed. For background on why this
// is done during SSA construction rather than a separate SSA pass,
// see issue #19054.

// TODO(dvyukov): do not instrument initialization as writes:
// a := make([]int, 10)

// Do not instrument the following packages at all,
// at best instrumentation would cause infinite recursion.
var omit_pkgs = []string{"runtime/internal/atomic", "runtime/internal/sys", "runtime", "runtime/race", "runtime/msan", "internal/cpu"}

// Only insert racefuncenterfp/racefuncexit into the following packages.
// Memory accesses in the packages are either uninteresting or will cause false positives.
var norace_inst_pkgs = []string{"sync", "sync/atomic"}

func ispkgin(pkgs []string) bool {
	if myimportpath != "" {
		for _, p := range pkgs {
			if myimportpath == p {
				return true
			}
		}
	}

	return false
}

func instrument(fn *Node) {
	if fn.Func.Pragma&Norace != 0 {
		return
	}

	if !flag_race || !ispkgin(norace_inst_pkgs) {
		fn.Func.SetInstrumentBody(true)
	}

	if flag_race {
		lno := lineno
		lineno = src.NoXPos

		// nodpc is the PC of the caller as extracted by
		// getcallerpc. We use -widthptr(FP) for x86.
		// BUG: this will not work on arm.
		nodpc := nodfp.copy()
		nodpc.Type = types.Types[TUINTPTR]
		nodpc.Xoffset = int64(-Widthptr)
		fn.Func.Dcl = append(fn.Func.Dcl, nodpc)

		fn.Func.Enter.Prepend(mkcall("racefuncenter", nil, nil, nodpc))
		fn.Func.Exit.Append(mkcall("racefuncexit", nil, nil))

		lineno = lno
	}
}