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// 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 (
"fmt"
"strings"
)
// The racewalk pass modifies the code tree for the function as follows:
//
// 1. It inserts a call to racefuncenter at the beginning of each function.
// 2. It inserts a call to racefuncexit at the end of each function.
// 3. It inserts a call to raceread before each memory read.
// 4. It inserts a call to racewrite before each memory write.
//
// The rewriting is not yet complete. Certain nodes are not rewritten
// but should be.
// 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", "runtime/race"}
// Only insert racefuncenter/racefuncexit into the following packages.
// Memory accesses in the packages are either uninteresting or will cause false positives.
var noinst_pkgs = []string{"sync", "sync/atomic"}
func ispkgin(pkgs []string) bool {
if myimportpath != "" {
for i := 0; i < len(pkgs); i++ {
if myimportpath == pkgs[i] {
return true
}
}
}
return false
}
func isforkfunc(fn *Node) bool {
// Special case for syscall.forkAndExecInChild.
// In the child, this function must not acquire any locks, because
// they might have been locked at the time of the fork. This means
// no rescheduling, no malloc calls, and no new stack segments.
// Race instrumentation does all of the above.
return myimportpath != "" && myimportpath == "syscall" && fn.Nname.Sym.Name == "forkAndExecInChild"
}
func racewalk(fn *Node) {
if ispkgin(omit_pkgs) || isforkfunc(fn) {
return
}
if !ispkgin(noinst_pkgs) {
racewalklist(fn.Nbody, nil)
// nothing interesting for race detector in fn->enter
racewalklist(fn.Exit, nil)
}
// 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 := Nod(OXXX, nil, nil)
*nodpc = *nodfp
nodpc.Type = Types[TUINTPTR]
nodpc.Xoffset = int64(-Widthptr)
nd := mkcall("racefuncenter", nil, nil, nodpc)
fn.Enter = concat(list1(nd), fn.Enter)
nd = mkcall("racefuncexit", nil, nil)
fn.Exit = list(fn.Exit, nd)
if Debug['W'] != 0 {
s := fmt.Sprintf("after racewalk %v", Sconv(fn.Nname.Sym, 0))
dumplist(s, fn.Nbody)
s = fmt.Sprintf("enter %v", Sconv(fn.Nname.Sym, 0))
dumplist(s, fn.Enter)
s = fmt.Sprintf("exit %v", Sconv(fn.Nname.Sym, 0))
dumplist(s, fn.Exit)
}
}
func racewalklist(l *NodeList, init **NodeList) {
var instr *NodeList
for ; l != nil; l = l.Next {
instr = nil
racewalknode(&l.N, &instr, 0, 0)
if init == nil {
l.N.Ninit = concat(l.N.Ninit, instr)
} else {
*init = concat(*init, instr)
}
}
}
// walkexpr and walkstmt combined
// walks the tree and adds calls to the
// instrumentation code to top-level (statement) nodes' init
func racewalknode(np **Node, init **NodeList, wr int, skip int) {
n := *np
if n == nil {
return
}
if Debug['w'] > 1 {
Dump("racewalk-before", n)
}
setlineno(n)
if init == nil {
Fatal("racewalk: bad init list")
}
if init == &n.Ninit {
// If init == &n->ninit and n->ninit is non-nil,
// racewalknode might append it to itself.
// nil it out and handle it separately before putting it back.
l := n.Ninit
n.Ninit = nil
racewalklist(l, nil)
racewalknode(&n, &l, wr, skip) // recurse with nil n->ninit
appendinit(&n, l)
*np = n
return
}
racewalklist(n.Ninit, nil)
switch n.Op {
default:
Fatal("racewalk: unknown node type %v", Oconv(int(n.Op), 0))
case OAS,
OAS2FUNC:
racewalknode(&n.Left, init, 1, 0)
racewalknode(&n.Right, init, 0, 0)
goto ret
// can't matter
case OCFUNC,
OVARKILL:
goto ret
case OBLOCK:
if n.List == nil {
goto ret
}
switch n.List.N.Op {
// Blocks are used for multiple return function calls.
// x, y := f() becomes BLOCK{CALL f, AS x [SP+0], AS y [SP+n]}
// We don't want to instrument between the statements because it will
// smash the results.
case OCALLFUNC,
OCALLMETH,
OCALLINTER:
racewalknode(&n.List.N, &n.List.N.Ninit, 0, 0)
fini := (*NodeList)(nil)
racewalklist(n.List.Next, &fini)
n.List = concat(n.List, fini)
// Ordinary block, for loop initialization or inlined bodies.
default:
racewalklist(n.List, nil)
}
goto ret
case ODEFER:
racewalknode(&n.Left, init, 0, 0)
goto ret
case OPROC:
racewalknode(&n.Left, init, 0, 0)
goto ret
case OCALLINTER:
racewalknode(&n.Left, init, 0, 0)
goto ret
// Instrument dst argument of runtime.writebarrier* calls
// as we do not instrument runtime code.
// typedslicecopy is instrumented in runtime.
case OCALLFUNC:
if n.Left.Sym != nil && n.Left.Sym.Pkg == Runtimepkg && (strings.HasPrefix(n.Left.Sym.Name, "writebarrier") || n.Left.Sym.Name == "typedmemmove") {
// Find the dst argument.
// The list can be reordered, so it's not necessary just the first or the second element.
var l *NodeList
for l = n.List; l != nil; l = l.Next {
if n.Left.Sym.Name == "typedmemmove" {
if l.N.Left.Xoffset == int64(Widthptr) {
break
}
} else {
if l.N.Left.Xoffset == 0 {
break
}
}
}
if l == nil {
Fatal("racewalk: writebarrier no arg")
}
if l.N.Right.Op != OADDR {
Fatal("racewalk: writebarrier bad arg")
}
callinstr(&l.N.Right.Left, init, 1, 0)
}
racewalknode(&n.Left, init, 0, 0)
goto ret
case ONOT,
OMINUS,
OPLUS,
OREAL,
OIMAG,
OCOM:
racewalknode(&n.Left, init, wr, 0)
goto ret
case ODOTINTER:
racewalknode(&n.Left, init, 0, 0)
goto ret
case ODOT:
racewalknode(&n.Left, init, 0, 1)
callinstr(&n, init, wr, skip)
goto ret
case ODOTPTR: // dst = (*x).f with implicit *; otherwise it's ODOT+OIND
racewalknode(&n.Left, init, 0, 0)
callinstr(&n, init, wr, skip)
goto ret
case OIND: // *p
racewalknode(&n.Left, init, 0, 0)
callinstr(&n, init, wr, skip)
goto ret
case OSPTR,
OLEN,
OCAP:
racewalknode(&n.Left, init, 0, 0)
if Istype(n.Left.Type, TMAP) {
n1 := Nod(OCONVNOP, n.Left, nil)
n1.Type = Ptrto(Types[TUINT8])
n1 = Nod(OIND, n1, nil)
typecheck(&n1, Erv)
callinstr(&n1, init, 0, skip)
}
goto ret
case OLSH,
ORSH,
OLROT,
OAND,
OANDNOT,
OOR,
OXOR,
OSUB,
OMUL,
OHMUL,
OEQ,
ONE,
OLT,
OLE,
OGE,
OGT,
OADD,
OCOMPLEX:
racewalknode(&n.Left, init, wr, 0)
racewalknode(&n.Right, init, wr, 0)
goto ret
case OANDAND,
OOROR:
racewalknode(&n.Left, init, wr, 0)
// walk has ensured the node has moved to a location where
// side effects are safe.
// n->right may not be executed,
// so instrumentation goes to n->right->ninit, not init.
racewalknode(&n.Right, &n.Right.Ninit, wr, 0)
goto ret
case ONAME:
callinstr(&n, init, wr, skip)
goto ret
case OCONV:
racewalknode(&n.Left, init, wr, 0)
goto ret
case OCONVNOP:
racewalknode(&n.Left, init, wr, 0)
goto ret
case ODIV,
OMOD:
racewalknode(&n.Left, init, wr, 0)
racewalknode(&n.Right, init, wr, 0)
goto ret
case OINDEX:
if !Isfixedarray(n.Left.Type) {
racewalknode(&n.Left, init, 0, 0)
} else if !islvalue(n.Left) {
// index of unaddressable array, like Map[k][i].
racewalknode(&n.Left, init, wr, 0)
racewalknode(&n.Right, init, 0, 0)
goto ret
}
racewalknode(&n.Right, init, 0, 0)
if n.Left.Type.Etype != TSTRING {
callinstr(&n, init, wr, skip)
}
goto ret
// Seems to only lead to double instrumentation.
//racewalknode(&n->left, init, 0, 0);
case OSLICE,
OSLICEARR,
OSLICE3,
OSLICE3ARR:
goto ret
case OADDR:
racewalknode(&n.Left, init, 0, 1)
goto ret
// n->left is Type* which is not interesting.
case OEFACE:
racewalknode(&n.Right, init, 0, 0)
goto ret
case OITAB:
racewalknode(&n.Left, init, 0, 0)
goto ret
// should not appear in AST by now
case OSEND,
ORECV,
OCLOSE,
ONEW,
OXCASE,
OXFALL,
OCASE,
OPANIC,
ORECOVER,
OCONVIFACE,
OCMPIFACE,
OMAKECHAN,
OMAKEMAP,
OMAKESLICE,
OCALL,
OCOPY,
OAPPEND,
ORUNESTR,
OARRAYBYTESTR,
OARRAYRUNESTR,
OSTRARRAYBYTE,
OSTRARRAYRUNE,
OINDEXMAP,
// lowered to call
OCMPSTR,
OADDSTR,
ODOTTYPE,
ODOTTYPE2,
OAS2DOTTYPE,
OCALLPART,
// lowered to PTRLIT
OCLOSURE, // lowered to PTRLIT
ORANGE, // lowered to ordinary for loop
OARRAYLIT, // lowered to assignments
OMAPLIT,
OSTRUCTLIT,
OAS2,
OAS2RECV,
OAS2MAPR,
OASOP:
Yyerror("racewalk: %v must be lowered by now", Oconv(int(n.Op), 0))
goto ret
// impossible nodes: only appear in backend.
case ORROTC,
OEXTEND:
Yyerror("racewalk: %v cannot exist now", Oconv(int(n.Op), 0))
goto ret
// just do generic traversal
case OFOR,
OIF,
OCALLMETH,
ORETURN,
ORETJMP,
OSWITCH,
OSELECT,
OEMPTY,
OBREAK,
OCONTINUE,
OFALL,
OGOTO,
OLABEL:
goto ret
// does not require instrumentation
case OPRINT, // don't bother instrumenting it
OPRINTN, // don't bother instrumenting it
OCHECKNIL, // always followed by a read.
OPARAM, // it appears only in fn->exit to copy heap params back
OCLOSUREVAR, // immutable pointer to captured variable
ODOTMETH, // either part of CALLMETH or CALLPART (lowered to PTRLIT)
OINDREG, // at this stage, only n(SP) nodes from nodarg
ODCL, // declarations (without value) cannot be races
ODCLCONST,
ODCLTYPE,
OTYPE,
ONONAME,
OLITERAL,
OSLICESTR,
// always preceded by bounds checking, avoid double instrumentation.
OTYPESW: // ignored by code generation, do not instrument.
goto ret
}
ret:
if n.Op != OBLOCK { // OBLOCK is handled above in a special way.
racewalklist(n.List, init)
}
if n.Ntest != nil {
racewalknode(&n.Ntest, &n.Ntest.Ninit, 0, 0)
}
if n.Nincr != nil {
racewalknode(&n.Nincr, &n.Nincr.Ninit, 0, 0)
}
racewalklist(n.Nbody, nil)
racewalklist(n.Nelse, nil)
racewalklist(n.Rlist, nil)
*np = n
}
func isartificial(n *Node) bool {
// compiler-emitted artificial things that we do not want to instrument,
// cant' possibly participate in a data race.
if n.Op == ONAME && n.Sym != nil && n.Sym.Name != "" {
if n.Sym.Name == "_" {
return true
}
// autotmp's are always local
if strings.HasPrefix(n.Sym.Name, "autotmp_") {
return true
}
// statictmp's are read-only
if strings.HasPrefix(n.Sym.Name, "statictmp_") {
return true
}
// go.itab is accessed only by the compiler and runtime (assume safe)
if n.Sym.Pkg != nil && n.Sym.Pkg.Name != "" && n.Sym.Pkg.Name == "go.itab" {
return true
}
}
return false
}
func callinstr(np **Node, init **NodeList, wr int, skip int) bool {
n := *np
//print("callinstr for %+N [ %O ] etype=%E class=%d\n",
// n, n->op, n->type ? n->type->etype : -1, n->class);
if skip != 0 || n.Type == nil || n.Type.Etype >= TIDEAL {
return false
}
t := n.Type
if isartificial(n) {
return false
}
b := outervalue(n)
// it skips e.g. stores to ... parameter array
if isartificial(b) {
return false
}
class := int(b.Class)
// BUG: we _may_ want to instrument PAUTO sometimes
// e.g. if we've got a local variable/method receiver
// that has got a pointer inside. Whether it points to
// the heap or not is impossible to know at compile time
if (class&PHEAP != 0) || class == PPARAMREF || class == PEXTERN || b.Op == OINDEX || b.Op == ODOTPTR || b.Op == OIND {
hascalls := 0
foreach(n, hascallspred, &hascalls)
if hascalls != 0 {
n = detachexpr(n, init)
*np = n
}
n = treecopy(n)
makeaddable(n)
var f *Node
if t.Etype == TSTRUCT || Isfixedarray(t) {
name := "racereadrange"
if wr != 0 {
name = "racewriterange"
}
f = mkcall(name, nil, init, uintptraddr(n), Nodintconst(t.Width))
} else {
name := "raceread"
if wr != 0 {
name = "racewrite"
}
f = mkcall(name, nil, init, uintptraddr(n))
}
*init = list(*init, f)
return true
}
return false
}
// makeaddable returns a node whose memory location is the
// same as n, but which is addressable in the Go language
// sense.
// This is different from functions like cheapexpr that may make
// a copy of their argument.
func makeaddable(n *Node) {
// The arguments to uintptraddr technically have an address but
// may not be addressable in the Go sense: for example, in the case
// of T(v).Field where T is a struct type and v is
// an addressable value.
switch n.Op {
case OINDEX:
if Isfixedarray(n.Left.Type) {
makeaddable(n.Left)
}
// Turn T(v).Field into v.Field
case ODOT,
OXDOT:
if n.Left.Op == OCONVNOP {
n.Left = n.Left.Left
}
makeaddable(n.Left)
// nothing to do
case ODOTPTR:
fallthrough
default:
break
}
}
func uintptraddr(n *Node) *Node {
r := Nod(OADDR, n, nil)
r.Bounded = true
r = conv(r, Types[TUNSAFEPTR])
r = conv(r, Types[TUINTPTR])
return r
}
func detachexpr(n *Node, init **NodeList) *Node {
addr := Nod(OADDR, n, nil)
l := temp(Ptrto(n.Type))
as := Nod(OAS, l, addr)
typecheck(&as, Etop)
walkexpr(&as, init)
*init = list(*init, as)
ind := Nod(OIND, l, nil)
typecheck(&ind, Erv)
walkexpr(&ind, init)
return ind
}
func foreachnode(n *Node, f func(*Node, interface{}), c interface{}) {
if n != nil {
f(n, c)
}
}
func foreachlist(l *NodeList, f func(*Node, interface{}), c interface{}) {
for ; l != nil; l = l.Next {
foreachnode(l.N, f, c)
}
}
func foreach(n *Node, f func(*Node, interface{}), c interface{}) {
foreachlist(n.Ninit, f, c)
foreachnode(n.Left, f, c)
foreachnode(n.Right, f, c)
foreachlist(n.List, f, c)
foreachnode(n.Ntest, f, c)
foreachnode(n.Nincr, f, c)
foreachlist(n.Nbody, f, c)
foreachlist(n.Nelse, f, c)
foreachlist(n.Rlist, f, c)
}
func hascallspred(n *Node, c interface{}) {
switch n.Op {
case OCALL,
OCALLFUNC,
OCALLMETH,
OCALLINTER:
(*c.(*int))++
}
}
// appendinit is like addinit in subr.c
// but appends rather than prepends.
func appendinit(np **Node, init *NodeList) {
if init == nil {
return
}
n := *np
switch n.Op {
// There may be multiple refs to this node;
// introduce OCONVNOP to hold init list.
case ONAME,
OLITERAL:
n = Nod(OCONVNOP, n, nil)
n.Type = n.Left.Type
n.Typecheck = 1
*np = n
}
n.Ninit = concat(n.Ninit, init)
n.Ullman = UINF
}