case ODEFER:
if e.loopdepth == 1 { // top level
- n.Esc = EscNever // force stack allocation of defer record (see ssa.go)
break
}
// arguments leak out of scope
// non-transient location to avoid arguments from being
// transiently allocated.
if where.Op == ODEFER && e.loopDepth == 1 {
- where.Esc = EscNever // force stack allocation of defer record (see ssa.go)
// TODO(mdempsky): Eliminate redundant EscLocation allocs.
return e.teeHole(k, e.newLoc(nil, false).asHole())
}
assertI2I,
assertI2I2,
deferproc,
- deferprocStack,
Deferreturn,
Duffcopy,
Duffzero,
return hiter
}
-// deferstruct makes a runtime._defer structure, with additional space for
-// stksize bytes of args.
-func deferstruct(stksize int64) *types.Type {
- makefield := func(name string, typ *types.Type) *types.Field {
- f := types.NewField()
- f.Type = typ
- // Unlike the global makefield function, this one needs to set Pkg
- // because these types might be compared (in SSA CSE sorting).
- // TODO: unify this makefield and the global one above.
- f.Sym = &types.Sym{Name: name, Pkg: localpkg}
- return f
- }
- argtype := types.NewArray(types.Types[TUINT8], stksize)
- argtype.SetNoalg(true)
- argtype.Width = stksize
- argtype.Align = 1
- // These fields must match the ones in runtime/runtime2.go:_defer and
- // cmd/compile/internal/gc/ssa.go:(*state).call.
- fields := []*types.Field{
- makefield("siz", types.Types[TUINT32]),
- makefield("started", types.Types[TBOOL]),
- makefield("heap", types.Types[TBOOL]),
- makefield("sp", types.Types[TUINTPTR]),
- makefield("pc", types.Types[TUINTPTR]),
- // Note: the types here don't really matter. Defer structures
- // are always scanned explicitly during stack copying and GC,
- // so we make them uintptr type even though they are real pointers.
- makefield("fn", types.Types[TUINTPTR]),
- makefield("_panic", types.Types[TUINTPTR]),
- makefield("link", types.Types[TUINTPTR]),
- makefield("args", argtype),
- }
-
- // build struct holding the above fields
- s := types.New(TSTRUCT)
- s.SetNoalg(true)
- s.SetFields(fields)
- s.Width = widstruct(s, s, 0, 1)
- s.Align = uint8(Widthptr)
- return s
-}
-
// f is method type, with receiver.
// return function type, receiver as first argument (or not).
func methodfunc(f *types.Type, receiver *types.Type) *types.Type {
assertI2I = sysfunc("assertI2I")
assertI2I2 = sysfunc("assertI2I2")
deferproc = sysfunc("deferproc")
- deferprocStack = sysfunc("deferprocStack")
Deferreturn = sysfunc("deferreturn")
Duffcopy = sysvar("duffcopy") // asm func with special ABI
Duffzero = sysvar("duffzero") // asm func with special ABI
}
}
case ODEFER:
- d := callDefer
- if n.Esc == EscNever {
- d = callDeferStack
- }
- s.call(n.Left, d)
+ s.call(n.Left, callDefer)
case OGO:
s.call(n.Left, callGo)
const (
callNormal callKind = iota
callDefer
- callDeferStack
callGo
)
rcvr = s.newValue1(ssa.OpIData, types.Types[TUINTPTR], i)
}
dowidth(fn.Type)
- stksize := fn.Type.ArgWidth() // includes receiver, args, and results
+ stksize := fn.Type.ArgWidth() // includes receiver
// Run all assignments of temps.
// The temps are introduced to avoid overwriting argument
// slots when arguments themselves require function calls.
s.stmtList(n.List)
+ // Store arguments to stack, including defer/go arguments and receiver for method calls.
+ // These are written in SP-offset order.
+ argStart := Ctxt.FixedFrameSize()
+ // Defer/go args.
+ if k != callNormal {
+ // Write argsize and closure (args to newproc/deferproc).
+ argsize := s.constInt32(types.Types[TUINT32], int32(stksize))
+ addr := s.constOffPtrSP(s.f.Config.Types.UInt32Ptr, argStart)
+ s.store(types.Types[TUINT32], addr, argsize)
+ addr = s.constOffPtrSP(s.f.Config.Types.UintptrPtr, argStart+int64(Widthptr))
+ s.store(types.Types[TUINTPTR], addr, closure)
+ stksize += 2 * int64(Widthptr)
+ argStart += 2 * int64(Widthptr)
+ }
+
+ // Set receiver (for interface calls).
+ if rcvr != nil {
+ addr := s.constOffPtrSP(s.f.Config.Types.UintptrPtr, argStart)
+ s.store(types.Types[TUINTPTR], addr, rcvr)
+ }
+
+ // Write args.
+ t := n.Left.Type
+ args := n.Rlist.Slice()
+ if n.Op == OCALLMETH {
+ f := t.Recv()
+ s.storeArg(args[0], f.Type, argStart+f.Offset)
+ args = args[1:]
+ }
+ for i, n := range args {
+ f := t.Params().Field(i)
+ s.storeArg(n, f.Type, argStart+f.Offset)
+ }
+
+ // call target
var call *ssa.Value
- if k == callDeferStack {
- // Make a defer struct d on the stack.
- t := deferstruct(stksize)
- d := tempAt(n.Pos, s.curfn, t)
-
- s.vars[&memVar] = s.newValue1A(ssa.OpVarDef, types.TypeMem, d, s.mem())
- addr := s.addr(d, false)
-
- // Must match reflect.go:deferstruct and src/runtime/runtime2.go:_defer.
- // 0: siz
- s.store(types.Types[TUINT32],
- s.newValue1I(ssa.OpOffPtr, types.Types[TUINT32].PtrTo(), t.FieldOff(0), addr),
- s.constInt32(types.Types[TUINT32], int32(stksize)))
- // 1: started, set in deferprocStack
- // 2: heap, set in deferprocStack
- // 3: sp, set in deferprocStack
- // 4: pc, set in deferprocStack
- // 5: fn
- s.store(closure.Type,
- s.newValue1I(ssa.OpOffPtr, closure.Type.PtrTo(), t.FieldOff(5), addr),
- closure)
- // 6: panic, set in deferprocStack
- // 7: link, set in deferprocStack
-
- // Then, store all the arguments of the defer call.
- ft := fn.Type
- off := t.FieldOff(8)
- args := n.Rlist.Slice()
-
- // Set receiver (for interface calls). Always a pointer.
- if rcvr != nil {
- p := s.newValue1I(ssa.OpOffPtr, ft.Recv().Type.PtrTo(), off, addr)
- s.store(types.Types[TUINTPTR], p, rcvr)
- }
- // Set receiver (for method calls).
- if n.Op == OCALLMETH {
- f := ft.Recv()
- s.storeArgWithBase(args[0], f.Type, addr, off+f.Offset)
- args = args[1:]
- }
- // Set other args.
- for _, f := range ft.Params().Fields().Slice() {
- s.storeArgWithBase(args[0], f.Type, addr, off+f.Offset)
- args = args[1:]
- }
-
- // Call runtime.deferprocStack with pointer to _defer record.
- arg0 := s.constOffPtrSP(types.Types[TUINTPTR], Ctxt.FixedFrameSize())
- s.store(types.Types[TUINTPTR], arg0, addr)
- call = s.newValue1A(ssa.OpStaticCall, types.TypeMem, deferprocStack, s.mem())
- if stksize < int64(Widthptr) {
- // We need room for both the call to deferprocStack and the call to
- // the deferred function.
- stksize = int64(Widthptr)
- }
- call.AuxInt = stksize
- } else {
- // Store arguments to stack, including defer/go arguments and receiver for method calls.
- // These are written in SP-offset order.
- argStart := Ctxt.FixedFrameSize()
- // Defer/go args.
- if k != callNormal {
- // Write argsize and closure (args to newproc/deferproc).
- argsize := s.constInt32(types.Types[TUINT32], int32(stksize))
- addr := s.constOffPtrSP(s.f.Config.Types.UInt32Ptr, argStart)
- s.store(types.Types[TUINT32], addr, argsize)
- addr = s.constOffPtrSP(s.f.Config.Types.UintptrPtr, argStart+int64(Widthptr))
- s.store(types.Types[TUINTPTR], addr, closure)
- stksize += 2 * int64(Widthptr)
- argStart += 2 * int64(Widthptr)
- }
-
- // Set receiver (for interface calls).
- if rcvr != nil {
- addr := s.constOffPtrSP(s.f.Config.Types.UintptrPtr, argStart)
- s.store(types.Types[TUINTPTR], addr, rcvr)
- }
-
- // Write args.
- t := n.Left.Type
- args := n.Rlist.Slice()
- if n.Op == OCALLMETH {
- f := t.Recv()
- s.storeArg(args[0], f.Type, argStart+f.Offset)
- args = args[1:]
- }
- for i, n := range args {
- f := t.Params().Field(i)
- s.storeArg(n, f.Type, argStart+f.Offset)
- }
-
- // call target
- switch {
- case k == callDefer:
- call = s.newValue1A(ssa.OpStaticCall, types.TypeMem, deferproc, s.mem())
- case k == callGo:
- call = s.newValue1A(ssa.OpStaticCall, types.TypeMem, newproc, s.mem())
- case closure != nil:
- // rawLoad because loading the code pointer from a
- // closure is always safe, but IsSanitizerSafeAddr
- // can't always figure that out currently, and it's
- // critical that we not clobber any arguments already
- // stored onto the stack.
- codeptr = s.rawLoad(types.Types[TUINTPTR], closure)
- call = s.newValue3(ssa.OpClosureCall, types.TypeMem, codeptr, closure, s.mem())
- case codeptr != nil:
- call = s.newValue2(ssa.OpInterCall, types.TypeMem, codeptr, s.mem())
- case sym != nil:
- call = s.newValue1A(ssa.OpStaticCall, types.TypeMem, sym.Linksym(), s.mem())
- default:
- Fatalf("bad call type %v %v", n.Op, n)
- }
- call.AuxInt = stksize // Call operations carry the argsize of the callee along with them
+ switch {
+ case k == callDefer:
+ call = s.newValue1A(ssa.OpStaticCall, types.TypeMem, deferproc, s.mem())
+ case k == callGo:
+ call = s.newValue1A(ssa.OpStaticCall, types.TypeMem, newproc, s.mem())
+ case closure != nil:
+ // rawLoad because loading the code pointer from a
+ // closure is always safe, but IsSanitizerSafeAddr
+ // can't always figure that out currently, and it's
+ // critical that we not clobber any arguments already
+ // stored onto the stack.
+ codeptr = s.rawLoad(types.Types[TUINTPTR], closure)
+ call = s.newValue3(ssa.OpClosureCall, types.TypeMem, codeptr, closure, s.mem())
+ case codeptr != nil:
+ call = s.newValue2(ssa.OpInterCall, types.TypeMem, codeptr, s.mem())
+ case sym != nil:
+ call = s.newValue1A(ssa.OpStaticCall, types.TypeMem, sym.Linksym(), s.mem())
+ default:
+ Fatalf("bad call type %v %v", n.Op, n)
}
+ call.AuxInt = stksize // Call operations carry the argsize of the callee along with them
s.vars[&memVar] = call
// Finish block for defers
- if k == callDefer || k == callDeferStack {
+ if k == callDefer {
b := s.endBlock()
b.Kind = ssa.BlockDefer
b.SetControl(call)
}
func (s *state) storeArg(n *Node, t *types.Type, off int64) {
- s.storeArgWithBase(n, t, s.sp, off)
-}
-
-func (s *state) storeArgWithBase(n *Node, t *types.Type, base *ssa.Value, off int64) {
pt := types.NewPtr(t)
- var addr *ssa.Value
- if base == s.sp {
- // Use special routine that avoids allocation on duplicate offsets.
- addr = s.constOffPtrSP(pt, off)
- } else {
- addr = s.newValue1I(ssa.OpOffPtr, pt, off, base)
- }
+ sp := s.constOffPtrSP(pt, off)
if !canSSAType(t) {
a := s.addr(n, false)
- s.move(t, addr, a)
+ s.move(t, sp, a)
return
}
a := s.expr(n)
- s.storeType(t, addr, a, 0, false)
+ s.storeType(t, sp, a, 0, false)
}
// slice computes the slice v[i:j:k] and returns ptr, len, and cap of result.
// Find additional pointers that point into the stack from the heap.
// Currently this includes defers and panics. See also function copystack.
-
- // Find and trace all defer arguments.
tracebackdefers(gp, scanframe, nil)
-
- // Find and trace other pointers in defer records.
for d := gp._defer; d != nil; d = d.link {
+ // tracebackdefers above does not scan the func value, which could
+ // be a stack allocated closure. See issue 30453.
if d.fn != nil {
- // tracebackdefers above does not scan the func value, which could
- // be a stack allocated closure. See issue 30453.
scanblock(uintptr(unsafe.Pointer(&d.fn)), sys.PtrSize, &oneptrmask[0], gcw, &state)
}
- if d.link != nil {
- // The link field of a stack-allocated defer record might point
- // to a heap-allocated defer record. Keep that heap record live.
- scanblock(uintptr(unsafe.Pointer(&d.link)), sys.PtrSize, &oneptrmask[0], gcw, &state)
- }
- // Retain defers records themselves.
- // Defer records might not be reachable from the G through regular heap
- // tracing because the defer linked list might weave between the stack and the heap.
- if d.heap {
- scanblock(uintptr(unsafe.Pointer(&d)), sys.PtrSize, &oneptrmask[0], gcw, &state)
- }
}
if gp._panic != nil {
- // Panics are always stack allocated.
state.putPtr(uintptr(unsafe.Pointer(gp._panic)))
}
// been set and must not be clobbered.
}
-// deferprocStack queues a new deferred function with a defer record on the stack.
-// The defer record must have its siz and fn fields initialized.
-// All other fields can contain junk.
-// The defer record must be immediately followed in memory by
-// the arguments of the defer.
-// Nosplit because the arguments on the stack won't be scanned
-// until the defer record is spliced into the gp._defer list.
-//go:nosplit
-func deferprocStack(d *_defer) {
- gp := getg()
- if gp.m.curg != gp {
- // go code on the system stack can't defer
- throw("defer on system stack")
- }
- // siz and fn are already set.
- // The other fields are junk on entry to deferprocStack and
- // are initialized here.
- d.started = false
- d.heap = false
- d.sp = getcallersp()
- d.pc = getcallerpc()
- // The lines below implement:
- // d.panic = nil
- // d.link = gp._defer
- // gp._defer = d
- // But without write barriers. The first two are writes to
- // the stack so they don't need a write barrier, and furthermore
- // are to uninitialized memory, so they must not use a write barrier.
- // The third write does not require a write barrier because we
- // explicitly mark all the defer structures, so we don't need to
- // keep track of pointers to them with a write barrier.
- *(*uintptr)(unsafe.Pointer(&d._panic)) = 0
- *(*uintptr)(unsafe.Pointer(&d.link)) = uintptr(unsafe.Pointer(gp._defer))
- *(*uintptr)(unsafe.Pointer(&gp._defer)) = uintptr(unsafe.Pointer(d))
-
- return0()
- // No code can go here - the C return register has
- // been set and must not be clobbered.
-}
-
// Small malloc size classes >= 16 are the multiples of 16: 16, 32, 48, 64, 80, 96, 112, 128, 144, ...
// Each P holds a pool for defers with small arg sizes.
// Assign defer allocations to pools by rounding to 16, to match malloc size classes.
}
}
d.siz = siz
- d.heap = true
d.link = gp._defer
gp._defer = d
return d
if d.fn != nil {
freedeferfn()
}
- if !d.heap {
- return
- }
sc := deferclass(uintptr(d.siz))
if sc >= uintptr(len(p{}.deferpool)) {
return
// A _defer holds an entry on the list of deferred calls.
// If you add a field here, add code to clear it in freedefer.
-// This struct must match the code in cmd/compile/internal/gc/reflect.go:deferstruct
-// and cmd/compile/internal/gc/ssa.go:(*state).call.
-// Some defers will be allocated on the stack and some on the heap.
-// All defers are logically part of the stack, so write barriers to
-// initialize them are not required. All defers must be manually scanned,
-// and for heap defers, marked.
type _defer struct {
- siz int32 // includes both arguments and results
+ siz int32
started bool
- heap bool
sp uintptr // sp at time of defer
pc uintptr
fn *funcval
}
func adjustdefers(gp *g, adjinfo *adjustinfo) {
+ // Adjust defer argument blocks the same way we adjust active stack frames.
+ tracebackdefers(gp, adjustframe, noescape(unsafe.Pointer(adjinfo)))
+
// Adjust pointers in the Defer structs.
- // We need to do this first because we need to adjust the
- // defer.link fields so we always work on the new stack.
- adjustpointer(adjinfo, unsafe.Pointer(&gp._defer))
+ // Defer structs themselves are never on the stack.
for d := gp._defer; d != nil; d = d.link {
adjustpointer(adjinfo, unsafe.Pointer(&d.fn))
adjustpointer(adjinfo, unsafe.Pointer(&d.sp))
adjustpointer(adjinfo, unsafe.Pointer(&d._panic))
- adjustpointer(adjinfo, unsafe.Pointer(&d.link))
}
-
- // Adjust defer argument blocks the same way we adjust active stack frames.
- // Note: this code is after the loop above, so that if a defer record is
- // stack allocated, we work on the copy in the new stack.
- tracebackdefers(gp, adjustframe, noescape(unsafe.Pointer(adjinfo)))
}
func adjustpanics(gp *g, adjinfo *adjustinfo) {
t.Errorf("output:\n%s\n\nwant no output", output)
}
}
-
-func TestDeferHeapAndStack(t *testing.T) {
- P := 4 // processors
- N := 10000 //iterations
- D := 200 // stack depth
-
- if testing.Short() {
- P /= 2
- N /= 10
- D /= 10
- }
- c := make(chan bool)
- for p := 0; p < P; p++ {
- go func() {
- for i := 0; i < N; i++ {
- if deferHeapAndStack(D) != 2*D {
- panic("bad result")
- }
- }
- c <- true
- }()
- }
- for p := 0; p < P; p++ {
- <-c
- }
-}
-
-// deferHeapAndStack(n) computes 2*n
-func deferHeapAndStack(n int) (r int) {
- if n == 0 {
- return 0
- }
- if n%2 == 0 {
- // heap-allocated defers
- for i := 0; i < 2; i++ {
- defer func() {
- r++
- }()
- }
- } else {
- // stack-allocated defers
- defer func() {
- r++
- }()
- defer func() {
- r++
- }()
- }
- r = deferHeapAndStack(n - 1)
- escapeMe(new([1024]byte)) // force some GCs
- return
-}
-
-// Pass a value to escapeMe to force it to escape.
-var escapeMe = func(x interface{}) {}
//go:noescape
func asmcgocall(fn, arg unsafe.Pointer) int32
+// argp used in Defer structs when there is no argp.
+const _NoArgs = ^uintptr(0)
+
func morestack()
func morestack_noctxt()
func rt0_go()
//go:nosplit
func syscall_loadsystemlibrary(filename *uint16, absoluteFilepath *uint16) (handle, err uintptr) {
lockOSThread()
+ defer unlockOSThread()
c := &getg().m.syscall
if useLoadLibraryEx {
if handle == 0 {
err = c.err
}
- unlockOSThread() // not defer'd after the lockOSThread above to save stack frame size.
return
}
waspanic := false
cgoCtxt := gp.cgoCtxt
printing := pcbuf == nil && callback == nil
+ _defer := gp._defer
+
+ for _defer != nil && _defer.sp == _NoArgs {
+ _defer = _defer.link
+ }
// If the PC is zero, it's likely a nil function call.
// Start in the caller's frame.
// In the latter case, use a deferreturn call site as the continuation pc.
frame.continpc = frame.pc
if waspanic {
- if frame.fn.deferreturn != 0 {
+ // We match up defers with frames using the SP.
+ // However, if the function has an empty stack
+ // frame, then it's possible (on LR machines)
+ // for multiple call frames to have the same
+ // SP. But, since a function with no frame
+ // can't push a defer, the defer can't belong
+ // to that frame.
+ if _defer != nil && _defer.sp == frame.sp && frame.sp != frame.fp {
frame.continpc = frame.fn.entry + uintptr(frame.fn.deferreturn) + 1
- // Note: this may perhaps keep return variables alive longer than
- // strictly necessary, as we are using "function has a defer statement"
- // as a proxy for "function actually deferred something". It seems
- // to be a minor drawback. (We used to actually look through the
- // gp._defer for a defer corresponding to this function, but that
- // is hard to do with defer records on the stack during a stack copy.)
// Note: the +1 is to offset the -1 that
// stack.go:getStackMap does to back up a return
// address make sure the pc is in the CALL instruction.
}
}
+ // Unwind our local defer stack past this frame.
+ for _defer != nil && ((_defer.sp == frame.sp && frame.sp != frame.fp) || _defer.sp == _NoArgs) {
+ _defer = _defer.link
+ }
+
if callback != nil {
if !callback((*stkframe)(noescape(unsafe.Pointer(&frame))), v) {
return n
n = nprint
}
+ // If callback != nil, we're being called to gather stack information during
+ // garbage collection or stack growth. In that context, require that we used
+ // up the entire defer stack. If not, then there is a bug somewhere and the
+ // garbage collection or stack growth may not have seen the correct picture
+ // of the stack. Crash now instead of silently executing the garbage collection
+ // or stack copy incorrectly and setting up for a mysterious crash later.
+ //
// Note that panic != nil is okay here: there can be leftover panics,
// because the defers on the panic stack do not nest in frame order as
// they do on the defer stack. If you have:
// At other times, such as when gathering a stack for a profiling signal
// or when printing a traceback during a crash, everything may not be
// stopped nicely, and the stack walk may not be able to complete.
+ // It's okay in those situations not to use up the entire defer stack:
+ // incomplete information then is still better than nothing.
+ if callback != nil && n < max && _defer != nil {
+ print("runtime: g", gp.goid, ": leftover defer sp=", hex(_defer.sp), " pc=", hex(_defer.pc), "\n")
+ for _defer = gp._defer; _defer != nil; _defer = _defer.link {
+ print("\tdefer ", _defer, " sp=", hex(_defer.sp), " pc=", hex(_defer.pc), "\n")
+ }
+ throw("traceback has leftover defers")
+ }
+
if callback != nil && n < max && frame.sp != gp.stktopsp {
print("runtime: g", gp.goid, ": frame.sp=", hex(frame.sp), " top=", hex(gp.stktopsp), "\n")
print("\tstack=[", hex(gp.stack.lo), "-", hex(gp.stack.hi), "] n=", n, " max=", max, "\n")
_ = i << s // panicShift
_ = i / j // panicDivide
}
-
-func Defer() {
- // amd64:`CALL\truntime\.deferprocStack`
- defer func() {}()
-}
// In particular, at printint r must be live.
func f41(p, q *int) (r *int) { // ERROR "live at entry to f41: p q$"
r = p
- defer func() { // ERROR "live at call to deferprocStack: q r$" "live at call to deferreturn: r$"
+ defer func() { // ERROR "live at call to deferproc: q r$" "live at call to deferreturn: r$"
recover()
}()
printint(0) // ERROR "live at call to printint: q r$"