Adding upstream version 1.21.8.upstream/1.21.8

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 525 insertions, 0 deletions

diff --git a/src/runtime/mfinal.go b/src/runtime/mfinal.go
new file mode 100644
index 0000000..650db18
--- /dev/null
+++ b/src/runtime/mfinal.go
@@ -0,0 +1,525 @@
+// Copyright 2009 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.
+
+// Garbage collector: finalizers and block profiling.
+
+package runtime
+
+import (
+	"internal/abi"
+	"internal/goarch"
+	"runtime/internal/atomic"
+	"runtime/internal/sys"
+	"unsafe"
+)
+
+// finblock is an array of finalizers to be executed. finblocks are
+// arranged in a linked list for the finalizer queue.
+//
+// finblock is allocated from non-GC'd memory, so any heap pointers
+// must be specially handled. GC currently assumes that the finalizer
+// queue does not grow during marking (but it can shrink).
+type finblock struct {
+	_       sys.NotInHeap
+	alllink *finblock
+	next    *finblock
+	cnt     uint32
+	_       int32
+	fin     [(_FinBlockSize - 2*goarch.PtrSize - 2*4) / unsafe.Sizeof(finalizer{})]finalizer
+}
+
+var fingStatus atomic.Uint32
+
+// finalizer goroutine status.
+const (
+	fingUninitialized uint32 = iota
+	fingCreated       uint32 = 1 << (iota - 1)
+	fingRunningFinalizer
+	fingWait
+	fingWake
+)
+
+var finlock mutex  // protects the following variables
+var fing *g        // goroutine that runs finalizers
+var finq *finblock // list of finalizers that are to be executed
+var finc *finblock // cache of free blocks
+var finptrmask [_FinBlockSize / goarch.PtrSize / 8]byte
+
+var allfin *finblock // list of all blocks
+
+// NOTE: Layout known to queuefinalizer.
+type finalizer struct {
+	fn   *funcval       // function to call (may be a heap pointer)
+	arg  unsafe.Pointer // ptr to object (may be a heap pointer)
+	nret uintptr        // bytes of return values from fn
+	fint *_type         // type of first argument of fn
+	ot   *ptrtype       // type of ptr to object (may be a heap pointer)
+}
+
+var finalizer1 = [...]byte{
+	// Each Finalizer is 5 words, ptr ptr INT ptr ptr (INT = uintptr here)
+	// Each byte describes 8 words.
+	// Need 8 Finalizers described by 5 bytes before pattern repeats:
+	//	ptr ptr INT ptr ptr
+	//	ptr ptr INT ptr ptr
+	//	ptr ptr INT ptr ptr
+	//	ptr ptr INT ptr ptr
+	//	ptr ptr INT ptr ptr
+	//	ptr ptr INT ptr ptr
+	//	ptr ptr INT ptr ptr
+	//	ptr ptr INT ptr ptr
+	// aka
+	//
+	//	ptr ptr INT ptr ptr ptr ptr INT
+	//	ptr ptr ptr ptr INT ptr ptr ptr
+	//	ptr INT ptr ptr ptr ptr INT ptr
+	//	ptr ptr ptr INT ptr ptr ptr ptr
+	//	INT ptr ptr ptr ptr INT ptr ptr
+	//
+	// Assumptions about Finalizer layout checked below.
+	1<<0 | 1<<1 | 0<<2 | 1<<3 | 1<<4 | 1<<5 | 1<<6 | 0<<7,
+	1<<0 | 1<<1 | 1<<2 | 1<<3 | 0<<4 | 1<<5 | 1<<6 | 1<<7,
+	1<<0 | 0<<1 | 1<<2 | 1<<3 | 1<<4 | 1<<5 | 0<<6 | 1<<7,
+	1<<0 | 1<<1 | 1<<2 | 0<<3 | 1<<4 | 1<<5 | 1<<6 | 1<<7,
+	0<<0 | 1<<1 | 1<<2 | 1<<3 | 1<<4 | 0<<5 | 1<<6 | 1<<7,
+}
+
+// lockRankMayQueueFinalizer records the lock ranking effects of a
+// function that may call queuefinalizer.
+func lockRankMayQueueFinalizer() {
+	lockWithRankMayAcquire(&finlock, getLockRank(&finlock))
+}
+
+func queuefinalizer(p unsafe.Pointer, fn *funcval, nret uintptr, fint *_type, ot *ptrtype) {
+	if gcphase != _GCoff {
+		// Currently we assume that the finalizer queue won't
+		// grow during marking so we don't have to rescan it
+		// during mark termination. If we ever need to lift
+		// this assumption, we can do it by adding the
+		// necessary barriers to queuefinalizer (which it may
+		// have automatically).
+		throw("queuefinalizer during GC")
+	}
+
+	lock(&finlock)
+	if finq == nil || finq.cnt == uint32(len(finq.fin)) {
+		if finc == nil {
+			finc = (*finblock)(persistentalloc(_FinBlockSize, 0, &memstats.gcMiscSys))
+			finc.alllink = allfin
+			allfin = finc
+			if finptrmask[0] == 0 {
+				// Build pointer mask for Finalizer array in block.
+				// Check assumptions made in finalizer1 array above.
+				if (unsafe.Sizeof(finalizer{}) != 5*goarch.PtrSize ||
+					unsafe.Offsetof(finalizer{}.fn) != 0 ||
+					unsafe.Offsetof(finalizer{}.arg) != goarch.PtrSize ||
+					unsafe.Offsetof(finalizer{}.nret) != 2*goarch.PtrSize ||
+					unsafe.Offsetof(finalizer{}.fint) != 3*goarch.PtrSize ||
+					unsafe.Offsetof(finalizer{}.ot) != 4*goarch.PtrSize) {
+					throw("finalizer out of sync")
+				}
+				for i := range finptrmask {
+					finptrmask[i] = finalizer1[i%len(finalizer1)]
+				}
+			}
+		}
+		block := finc
+		finc = block.next
+		block.next = finq
+		finq = block
+	}
+	f := &finq.fin[finq.cnt]
+	atomic.Xadd(&finq.cnt, +1) // Sync with markroots
+	f.fn = fn
+	f.nret = nret
+	f.fint = fint
+	f.ot = ot
+	f.arg = p
+	unlock(&finlock)
+	fingStatus.Or(fingWake)
+}
+
+//go:nowritebarrier
+func iterate_finq(callback func(*funcval, unsafe.Pointer, uintptr, *_type, *ptrtype)) {
+	for fb := allfin; fb != nil; fb = fb.alllink {
+		for i := uint32(0); i < fb.cnt; i++ {
+			f := &fb.fin[i]
+			callback(f.fn, f.arg, f.nret, f.fint, f.ot)
+		}
+	}
+}
+
+func wakefing() *g {
+	if ok := fingStatus.CompareAndSwap(fingCreated|fingWait|fingWake, fingCreated); ok {
+		return fing
+	}
+	return nil
+}
+
+func createfing() {
+	// start the finalizer goroutine exactly once
+	if fingStatus.Load() == fingUninitialized && fingStatus.CompareAndSwap(fingUninitialized, fingCreated) {
+		go runfinq()
+	}
+}
+
+func finalizercommit(gp *g, lock unsafe.Pointer) bool {
+	unlock((*mutex)(lock))
+	// fingStatus should be modified after fing is put into a waiting state
+	// to avoid waking fing in running state, even if it is about to be parked.
+	fingStatus.Or(fingWait)
+	return true
+}
+
+// This is the goroutine that runs all of the finalizers.
+func runfinq() {
+	var (
+		frame    unsafe.Pointer
+		framecap uintptr
+		argRegs  int
+	)
+
+	gp := getg()
+	lock(&finlock)
+	fing = gp
+	unlock(&finlock)
+
+	for {
+		lock(&finlock)
+		fb := finq
+		finq = nil
+		if fb == nil {
+			gopark(finalizercommit, unsafe.Pointer(&finlock), waitReasonFinalizerWait, traceBlockSystemGoroutine, 1)
+			continue
+		}
+		argRegs = intArgRegs
+		unlock(&finlock)
+		if raceenabled {
+			racefingo()
+		}
+		for fb != nil {
+			for i := fb.cnt; i > 0; i-- {
+				f := &fb.fin[i-1]
+
+				var regs abi.RegArgs
+				// The args may be passed in registers or on stack. Even for
+				// the register case, we still need the spill slots.
+				// TODO: revisit if we remove spill slots.
+				//
+				// Unfortunately because we can have an arbitrary
+				// amount of returns and it would be complex to try and
+				// figure out how many of those can get passed in registers,
+				// just conservatively assume none of them do.
+				framesz := unsafe.Sizeof((any)(nil)) + f.nret
+				if framecap < framesz {
+					// The frame does not contain pointers interesting for GC,
+					// all not yet finalized objects are stored in finq.
+					// If we do not mark it as FlagNoScan,
+					// the last finalized object is not collected.
+					frame = mallocgc(framesz, nil, true)
+					framecap = framesz
+				}
+
+				if f.fint == nil {
+					throw("missing type in runfinq")
+				}
+				r := frame
+				if argRegs > 0 {
+					r = unsafe.Pointer(&regs.Ints)
+				} else {
+					// frame is effectively uninitialized
+					// memory. That means we have to clear
+					// it before writing to it to avoid
+					// confusing the write barrier.
+					*(*[2]uintptr)(frame) = [2]uintptr{}
+				}
+				switch f.fint.Kind_ & kindMask {
+				case kindPtr:
+					// direct use of pointer
+					*(*unsafe.Pointer)(r) = f.arg
+				case kindInterface:
+					ityp := (*interfacetype)(unsafe.Pointer(f.fint))
+					// set up with empty interface
+					(*eface)(r)._type = &f.ot.Type
+					(*eface)(r).data = f.arg
+					if len(ityp.Methods) != 0 {
+						// convert to interface with methods
+						// this conversion is guaranteed to succeed - we checked in SetFinalizer
+						(*iface)(r).tab = assertE2I(ityp, (*eface)(r)._type)
+					}
+				default:
+					throw("bad kind in runfinq")
+				}
+				fingStatus.Or(fingRunningFinalizer)
+				reflectcall(nil, unsafe.Pointer(f.fn), frame, uint32(framesz), uint32(framesz), uint32(framesz), &regs)
+				fingStatus.And(^fingRunningFinalizer)
+
+				// Drop finalizer queue heap references
+				// before hiding them from markroot.
+				// This also ensures these will be
+				// clear if we reuse the finalizer.
+				f.fn = nil
+				f.arg = nil
+				f.ot = nil
+				atomic.Store(&fb.cnt, i-1)
+			}
+			next := fb.next
+			lock(&finlock)
+			fb.next = finc
+			finc = fb
+			unlock(&finlock)
+			fb = next
+		}
+	}
+}
+
+func isGoPointerWithoutSpan(p unsafe.Pointer) bool {
+	// 0-length objects are okay.
+	if p == unsafe.Pointer(&zerobase) {
+		return true
+	}
+
+	// Global initializers might be linker-allocated.
+	//	var Foo = &Object{}
+	//	func main() {
+	//		runtime.SetFinalizer(Foo, nil)
+	//	}
+	// The relevant segments are: noptrdata, data, bss, noptrbss.
+	// We cannot assume they are in any order or even contiguous,
+	// due to external linking.
+	for datap := &firstmoduledata; datap != nil; datap = datap.next {
+		if datap.noptrdata <= uintptr(p) && uintptr(p) < datap.enoptrdata ||
+			datap.data <= uintptr(p) && uintptr(p) < datap.edata ||
+			datap.bss <= uintptr(p) && uintptr(p) < datap.ebss ||
+			datap.noptrbss <= uintptr(p) && uintptr(p) < datap.enoptrbss {
+			return true
+		}
+	}
+	return false
+}
+
+// SetFinalizer sets the finalizer associated with obj to the provided
+// finalizer function. When the garbage collector finds an unreachable block
+// with an associated finalizer, it clears the association and runs
+// finalizer(obj) in a separate goroutine. This makes obj reachable again,
+// but now without an associated finalizer. Assuming that SetFinalizer
+// is not called again, the next time the garbage collector sees
+// that obj is unreachable, it will free obj.
+//
+// SetFinalizer(obj, nil) clears any finalizer associated with obj.
+//
+// The argument obj must be a pointer to an object allocated by calling
+// new, by taking the address of a composite literal, or by taking the
+// address of a local variable.
+// The argument finalizer must be a function that takes a single argument
+// to which obj's type can be assigned, and can have arbitrary ignored return
+// values. If either of these is not true, SetFinalizer may abort the
+// program.
+//
+// Finalizers are run in dependency order: if A points at B, both have
+// finalizers, and they are otherwise unreachable, only the finalizer
+// for A runs; once A is freed, the finalizer for B can run.
+// If a cyclic structure includes a block with a finalizer, that
+// cycle is not guaranteed to be garbage collected and the finalizer
+// is not guaranteed to run, because there is no ordering that
+// respects the dependencies.
+//
+// The finalizer is scheduled to run at some arbitrary time after the
+// program can no longer reach the object to which obj points.
+// There is no guarantee that finalizers will run before a program exits,
+// so typically they are useful only for releasing non-memory resources
+// associated with an object during a long-running program.
+// For example, an os.File object could use a finalizer to close the
+// associated operating system file descriptor when a program discards
+// an os.File without calling Close, but it would be a mistake
+// to depend on a finalizer to flush an in-memory I/O buffer such as a
+// bufio.Writer, because the buffer would not be flushed at program exit.
+//
+// It is not guaranteed that a finalizer will run if the size of *obj is
+// zero bytes, because it may share same address with other zero-size
+// objects in memory. See https://go.dev/ref/spec#Size_and_alignment_guarantees.
+//
+// It is not guaranteed that a finalizer will run for objects allocated
+// in initializers for package-level variables. Such objects may be
+// linker-allocated, not heap-allocated.
+//
+// Note that because finalizers may execute arbitrarily far into the future
+// after an object is no longer referenced, the runtime is allowed to perform
+// a space-saving optimization that batches objects together in a single
+// allocation slot. The finalizer for an unreferenced object in such an
+// allocation may never run if it always exists in the same batch as a
+// referenced object. Typically, this batching only happens for tiny
+// (on the order of 16 bytes or less) and pointer-free objects.
+//
+// A finalizer may run as soon as an object becomes unreachable.
+// In order to use finalizers correctly, the program must ensure that
+// the object is reachable until it is no longer required.
+// Objects stored in global variables, or that can be found by tracing
+// pointers from a global variable, are reachable. For other objects,
+// pass the object to a call of the KeepAlive function to mark the
+// last point in the function where the object must be reachable.
+//
+// For example, if p points to a struct, such as os.File, that contains
+// a file descriptor d, and p has a finalizer that closes that file
+// descriptor, and if the last use of p in a function is a call to
+// syscall.Write(p.d, buf, size), then p may be unreachable as soon as
+// the program enters syscall.Write. The finalizer may run at that moment,
+// closing p.d, causing syscall.Write to fail because it is writing to
+// a closed file descriptor (or, worse, to an entirely different
+// file descriptor opened by a different goroutine). To avoid this problem,
+// call KeepAlive(p) after the call to syscall.Write.
+//
+// A single goroutine runs all finalizers for a program, sequentially.
+// If a finalizer must run for a long time, it should do so by starting
+// a new goroutine.
+//
+// In the terminology of the Go memory model, a call
+// SetFinalizer(x, f) “synchronizes before” the finalization call f(x).
+// However, there is no guarantee that KeepAlive(x) or any other use of x
+// “synchronizes before” f(x), so in general a finalizer should use a mutex
+// or other synchronization mechanism if it needs to access mutable state in x.
+// For example, consider a finalizer that inspects a mutable field in x
+// that is modified from time to time in the main program before x
+// becomes unreachable and the finalizer is invoked.
+// The modifications in the main program and the inspection in the finalizer
+// need to use appropriate synchronization, such as mutexes or atomic updates,
+// to avoid read-write races.
+func SetFinalizer(obj any, finalizer any) {
+	if debug.sbrk != 0 {
+		// debug.sbrk never frees memory, so no finalizers run
+		// (and we don't have the data structures to record them).
+		return
+	}
+	e := efaceOf(&obj)
+	etyp := e._type
+	if etyp == nil {
+		throw("runtime.SetFinalizer: first argument is nil")
+	}
+	if etyp.Kind_&kindMask != kindPtr {
+		throw("runtime.SetFinalizer: first argument is " + toRType(etyp).string() + ", not pointer")
+	}
+	ot := (*ptrtype)(unsafe.Pointer(etyp))
+	if ot.Elem == nil {
+		throw("nil elem type!")
+	}
+
+	if inUserArenaChunk(uintptr(e.data)) {
+		// Arena-allocated objects are not eligible for finalizers.
+		throw("runtime.SetFinalizer: first argument was allocated into an arena")
+	}
+
+	// find the containing object
+	base, _, _ := findObject(uintptr(e.data), 0, 0)
+
+	if base == 0 {
+		if isGoPointerWithoutSpan(e.data) {
+			return
+		}
+		throw("runtime.SetFinalizer: pointer not in allocated block")
+	}
+
+	if uintptr(e.data) != base {
+		// As an implementation detail we allow to set finalizers for an inner byte
+		// of an object if it could come from tiny alloc (see mallocgc for details).
+		if ot.Elem == nil || ot.Elem.PtrBytes != 0 || ot.Elem.Size_ >= maxTinySize {
+			throw("runtime.SetFinalizer: pointer not at beginning of allocated block")
+		}
+	}
+
+	f := efaceOf(&finalizer)
+	ftyp := f._type
+	if ftyp == nil {
+		// switch to system stack and remove finalizer
+		systemstack(func() {
+			removefinalizer(e.data)
+		})
+		return
+	}
+
+	if ftyp.Kind_&kindMask != kindFunc {
+		throw("runtime.SetFinalizer: second argument is " + toRType(ftyp).string() + ", not a function")
+	}
+	ft := (*functype)(unsafe.Pointer(ftyp))
+	if ft.IsVariadic() {
+		throw("runtime.SetFinalizer: cannot pass " + toRType(etyp).string() + " to finalizer " + toRType(ftyp).string() + " because dotdotdot")
+	}
+	if ft.InCount != 1 {
+		throw("runtime.SetFinalizer: cannot pass " + toRType(etyp).string() + " to finalizer " + toRType(ftyp).string())
+	}
+	fint := ft.InSlice()[0]
+	switch {
+	case fint == etyp:
+		// ok - same type
+		goto okarg
+	case fint.Kind_&kindMask == kindPtr:
+		if (fint.Uncommon() == nil || etyp.Uncommon() == nil) && (*ptrtype)(unsafe.Pointer(fint)).Elem == ot.Elem {
+			// ok - not same type, but both pointers,
+			// one or the other is unnamed, and same element type, so assignable.
+			goto okarg
+		}
+	case fint.Kind_&kindMask == kindInterface:
+		ityp := (*interfacetype)(unsafe.Pointer(fint))
+		if len(ityp.Methods) == 0 {
+			// ok - satisfies empty interface
+			goto okarg
+		}
+		if iface := assertE2I2(ityp, *efaceOf(&obj)); iface.tab != nil {
+			goto okarg
+		}
+	}
+	throw("runtime.SetFinalizer: cannot pass " + toRType(etyp).string() + " to finalizer " + toRType(ftyp).string())
+okarg:
+	// compute size needed for return parameters
+	nret := uintptr(0)
+	for _, t := range ft.OutSlice() {
+		nret = alignUp(nret, uintptr(t.Align_)) + uintptr(t.Size_)
+	}
+	nret = alignUp(nret, goarch.PtrSize)
+
+	// make sure we have a finalizer goroutine
+	createfing()
+
+	systemstack(func() {
+		if !addfinalizer(e.data, (*funcval)(f.data), nret, fint, ot) {
+			throw("runtime.SetFinalizer: finalizer already set")
+		}
+	})
+}
+
+// Mark KeepAlive as noinline so that it is easily detectable as an intrinsic.
+//
+//go:noinline
+
+// KeepAlive marks its argument as currently reachable.
+// This ensures that the object is not freed, and its finalizer is not run,
+// before the point in the program where KeepAlive is called.
+//
+// A very simplified example showing where KeepAlive is required:
+//
+//	type File struct { d int }
+//	d, err := syscall.Open("/file/path", syscall.O_RDONLY, 0)
+//	// ... do something if err != nil ...
+//	p := &File{d}
+//	runtime.SetFinalizer(p, func(p *File) { syscall.Close(p.d) })
+//	var buf [10]byte
+//	n, err := syscall.Read(p.d, buf[:])
+//	// Ensure p is not finalized until Read returns.
+//	runtime.KeepAlive(p)
+//	// No more uses of p after this point.
+//
+// Without the KeepAlive call, the finalizer could run at the start of
+// syscall.Read, closing the file descriptor before syscall.Read makes
+// the actual system call.
+//
+// Note: KeepAlive should only be used to prevent finalizers from
+// running prematurely. In particular, when used with unsafe.Pointer,
+// the rules for valid uses of unsafe.Pointer still apply.
+func KeepAlive(x any) {
+	// Introduce a use of x that the compiler can't eliminate.
+	// This makes sure x is alive on entry. We need x to be alive
+	// on entry for "defer runtime.KeepAlive(x)"; see issue 21402.
+	if cgoAlwaysFalse {
+		println(x)
+	}
+}