Adding upstream version 1.20.14.upstream/1.20.14upstream

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

1 files changed, 533 insertions, 0 deletions

diff --git a/src/runtime/iface.go b/src/runtime/iface.go
new file mode 100644
index 0000000..a4d56dd
--- /dev/null
+++ b/src/runtime/iface.go
@@ -0,0 +1,533 @@
+// Copyright 2014 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 runtime
+
+import (
+	"internal/abi"
+	"internal/goarch"
+	"runtime/internal/atomic"
+	"unsafe"
+)
+
+const itabInitSize = 512
+
+var (
+	itabLock      mutex                               // lock for accessing itab table
+	itabTable     = &itabTableInit                    // pointer to current table
+	itabTableInit = itabTableType{size: itabInitSize} // starter table
+)
+
+// Note: change the formula in the mallocgc call in itabAdd if you change these fields.
+type itabTableType struct {
+	size    uintptr             // length of entries array. Always a power of 2.
+	count   uintptr             // current number of filled entries.
+	entries [itabInitSize]*itab // really [size] large
+}
+
+func itabHashFunc(inter *interfacetype, typ *_type) uintptr {
+	// compiler has provided some good hash codes for us.
+	return uintptr(inter.typ.hash ^ typ.hash)
+}
+
+func getitab(inter *interfacetype, typ *_type, canfail bool) *itab {
+	if len(inter.mhdr) == 0 {
+		throw("internal error - misuse of itab")
+	}
+
+	// easy case
+	if typ.tflag&tflagUncommon == 0 {
+		if canfail {
+			return nil
+		}
+		name := inter.typ.nameOff(inter.mhdr[0].name)
+		panic(&TypeAssertionError{nil, typ, &inter.typ, name.name()})
+	}
+
+	var m *itab
+
+	// First, look in the existing table to see if we can find the itab we need.
+	// This is by far the most common case, so do it without locks.
+	// Use atomic to ensure we see any previous writes done by the thread
+	// that updates the itabTable field (with atomic.Storep in itabAdd).
+	t := (*itabTableType)(atomic.Loadp(unsafe.Pointer(&itabTable)))
+	if m = t.find(inter, typ); m != nil {
+		goto finish
+	}
+
+	// Not found.  Grab the lock and try again.
+	lock(&itabLock)
+	if m = itabTable.find(inter, typ); m != nil {
+		unlock(&itabLock)
+		goto finish
+	}
+
+	// Entry doesn't exist yet. Make a new entry & add it.
+	m = (*itab)(persistentalloc(unsafe.Sizeof(itab{})+uintptr(len(inter.mhdr)-1)*goarch.PtrSize, 0, &memstats.other_sys))
+	m.inter = inter
+	m._type = typ
+	// The hash is used in type switches. However, compiler statically generates itab's
+	// for all interface/type pairs used in switches (which are added to itabTable
+	// in itabsinit). The dynamically-generated itab's never participate in type switches,
+	// and thus the hash is irrelevant.
+	// Note: m.hash is _not_ the hash used for the runtime itabTable hash table.
+	m.hash = 0
+	m.init()
+	itabAdd(m)
+	unlock(&itabLock)
+finish:
+	if m.fun[0] != 0 {
+		return m
+	}
+	if canfail {
+		return nil
+	}
+	// this can only happen if the conversion
+	// was already done once using the , ok form
+	// and we have a cached negative result.
+	// The cached result doesn't record which
+	// interface function was missing, so initialize
+	// the itab again to get the missing function name.
+	panic(&TypeAssertionError{concrete: typ, asserted: &inter.typ, missingMethod: m.init()})
+}
+
+// find finds the given interface/type pair in t.
+// Returns nil if the given interface/type pair isn't present.
+func (t *itabTableType) find(inter *interfacetype, typ *_type) *itab {
+	// Implemented using quadratic probing.
+	// Probe sequence is h(i) = h0 + i*(i+1)/2 mod 2^k.
+	// We're guaranteed to hit all table entries using this probe sequence.
+	mask := t.size - 1
+	h := itabHashFunc(inter, typ) & mask
+	for i := uintptr(1); ; i++ {
+		p := (**itab)(add(unsafe.Pointer(&t.entries), h*goarch.PtrSize))
+		// Use atomic read here so if we see m != nil, we also see
+		// the initializations of the fields of m.
+		// m := *p
+		m := (*itab)(atomic.Loadp(unsafe.Pointer(p)))
+		if m == nil {
+			return nil
+		}
+		if m.inter == inter && m._type == typ {
+			return m
+		}
+		h += i
+		h &= mask
+	}
+}
+
+// itabAdd adds the given itab to the itab hash table.
+// itabLock must be held.
+func itabAdd(m *itab) {
+	// Bugs can lead to calling this while mallocing is set,
+	// typically because this is called while panicing.
+	// Crash reliably, rather than only when we need to grow
+	// the hash table.
+	if getg().m.mallocing != 0 {
+		throw("malloc deadlock")
+	}
+
+	t := itabTable
+	if t.count >= 3*(t.size/4) { // 75% load factor
+		// Grow hash table.
+		// t2 = new(itabTableType) + some additional entries
+		// We lie and tell malloc we want pointer-free memory because
+		// all the pointed-to values are not in the heap.
+		t2 := (*itabTableType)(mallocgc((2+2*t.size)*goarch.PtrSize, nil, true))
+		t2.size = t.size * 2
+
+		// Copy over entries.
+		// Note: while copying, other threads may look for an itab and
+		// fail to find it. That's ok, they will then try to get the itab lock
+		// and as a consequence wait until this copying is complete.
+		iterate_itabs(t2.add)
+		if t2.count != t.count {
+			throw("mismatched count during itab table copy")
+		}
+		// Publish new hash table. Use an atomic write: see comment in getitab.
+		atomicstorep(unsafe.Pointer(&itabTable), unsafe.Pointer(t2))
+		// Adopt the new table as our own.
+		t = itabTable
+		// Note: the old table can be GC'ed here.
+	}
+	t.add(m)
+}
+
+// add adds the given itab to itab table t.
+// itabLock must be held.
+func (t *itabTableType) add(m *itab) {
+	// See comment in find about the probe sequence.
+	// Insert new itab in the first empty spot in the probe sequence.
+	mask := t.size - 1
+	h := itabHashFunc(m.inter, m._type) & mask
+	for i := uintptr(1); ; i++ {
+		p := (**itab)(add(unsafe.Pointer(&t.entries), h*goarch.PtrSize))
+		m2 := *p
+		if m2 == m {
+			// A given itab may be used in more than one module
+			// and thanks to the way global symbol resolution works, the
+			// pointed-to itab may already have been inserted into the
+			// global 'hash'.
+			return
+		}
+		if m2 == nil {
+			// Use atomic write here so if a reader sees m, it also
+			// sees the correctly initialized fields of m.
+			// NoWB is ok because m is not in heap memory.
+			// *p = m
+			atomic.StorepNoWB(unsafe.Pointer(p), unsafe.Pointer(m))
+			t.count++
+			return
+		}
+		h += i
+		h &= mask
+	}
+}
+
+// init fills in the m.fun array with all the code pointers for
+// the m.inter/m._type pair. If the type does not implement the interface,
+// it sets m.fun[0] to 0 and returns the name of an interface function that is missing.
+// It is ok to call this multiple times on the same m, even concurrently.
+func (m *itab) init() string {
+	inter := m.inter
+	typ := m._type
+	x := typ.uncommon()
+
+	// both inter and typ have method sorted by name,
+	// and interface names are unique,
+	// so can iterate over both in lock step;
+	// the loop is O(ni+nt) not O(ni*nt).
+	ni := len(inter.mhdr)
+	nt := int(x.mcount)
+	xmhdr := (*[1 << 16]method)(add(unsafe.Pointer(x), uintptr(x.moff)))[:nt:nt]
+	j := 0
+	methods := (*[1 << 16]unsafe.Pointer)(unsafe.Pointer(&m.fun[0]))[:ni:ni]
+	var fun0 unsafe.Pointer
+imethods:
+	for k := 0; k < ni; k++ {
+		i := &inter.mhdr[k]
+		itype := inter.typ.typeOff(i.ityp)
+		name := inter.typ.nameOff(i.name)
+		iname := name.name()
+		ipkg := name.pkgPath()
+		if ipkg == "" {
+			ipkg = inter.pkgpath.name()
+		}
+		for ; j < nt; j++ {
+			t := &xmhdr[j]
+			tname := typ.nameOff(t.name)
+			if typ.typeOff(t.mtyp) == itype && tname.name() == iname {
+				pkgPath := tname.pkgPath()
+				if pkgPath == "" {
+					pkgPath = typ.nameOff(x.pkgpath).name()
+				}
+				if tname.isExported() || pkgPath == ipkg {
+					if m != nil {
+						ifn := typ.textOff(t.ifn)
+						if k == 0 {
+							fun0 = ifn // we'll set m.fun[0] at the end
+						} else {
+							methods[k] = ifn
+						}
+					}
+					continue imethods
+				}
+			}
+		}
+		// didn't find method
+		m.fun[0] = 0
+		return iname
+	}
+	m.fun[0] = uintptr(fun0)
+	return ""
+}
+
+func itabsinit() {
+	lockInit(&itabLock, lockRankItab)
+	lock(&itabLock)
+	for _, md := range activeModules() {
+		for _, i := range md.itablinks {
+			itabAdd(i)
+		}
+	}
+	unlock(&itabLock)
+}
+
+// panicdottypeE is called when doing an e.(T) conversion and the conversion fails.
+// have = the dynamic type we have.
+// want = the static type we're trying to convert to.
+// iface = the static type we're converting from.
+func panicdottypeE(have, want, iface *_type) {
+	panic(&TypeAssertionError{iface, have, want, ""})
+}
+
+// panicdottypeI is called when doing an i.(T) conversion and the conversion fails.
+// Same args as panicdottypeE, but "have" is the dynamic itab we have.
+func panicdottypeI(have *itab, want, iface *_type) {
+	var t *_type
+	if have != nil {
+		t = have._type
+	}
+	panicdottypeE(t, want, iface)
+}
+
+// panicnildottype is called when doing a i.(T) conversion and the interface i is nil.
+// want = the static type we're trying to convert to.
+func panicnildottype(want *_type) {
+	panic(&TypeAssertionError{nil, nil, want, ""})
+	// TODO: Add the static type we're converting from as well.
+	// It might generate a better error message.
+	// Just to match other nil conversion errors, we don't for now.
+}
+
+// The specialized convTx routines need a type descriptor to use when calling mallocgc.
+// We don't need the type to be exact, just to have the correct size, alignment, and pointer-ness.
+// However, when debugging, it'd be nice to have some indication in mallocgc where the types came from,
+// so we use named types here.
+// We then construct interface values of these types,
+// and then extract the type word to use as needed.
+type (
+	uint16InterfacePtr uint16
+	uint32InterfacePtr uint32
+	uint64InterfacePtr uint64
+	stringInterfacePtr string
+	sliceInterfacePtr  []byte
+)
+
+var (
+	uint16Eface any = uint16InterfacePtr(0)
+	uint32Eface any = uint32InterfacePtr(0)
+	uint64Eface any = uint64InterfacePtr(0)
+	stringEface any = stringInterfacePtr("")
+	sliceEface  any = sliceInterfacePtr(nil)
+
+	uint16Type *_type = efaceOf(&uint16Eface)._type
+	uint32Type *_type = efaceOf(&uint32Eface)._type
+	uint64Type *_type = efaceOf(&uint64Eface)._type
+	stringType *_type = efaceOf(&stringEface)._type
+	sliceType  *_type = efaceOf(&sliceEface)._type
+)
+
+// The conv and assert functions below do very similar things.
+// The convXXX functions are guaranteed by the compiler to succeed.
+// The assertXXX functions may fail (either panicking or returning false,
+// depending on whether they are 1-result or 2-result).
+// The convXXX functions succeed on a nil input, whereas the assertXXX
+// functions fail on a nil input.
+
+// convT converts a value of type t, which is pointed to by v, to a pointer that can
+// be used as the second word of an interface value.
+func convT(t *_type, v unsafe.Pointer) unsafe.Pointer {
+	if raceenabled {
+		raceReadObjectPC(t, v, getcallerpc(), abi.FuncPCABIInternal(convT))
+	}
+	if msanenabled {
+		msanread(v, t.size)
+	}
+	if asanenabled {
+		asanread(v, t.size)
+	}
+	x := mallocgc(t.size, t, true)
+	typedmemmove(t, x, v)
+	return x
+}
+func convTnoptr(t *_type, v unsafe.Pointer) unsafe.Pointer {
+	// TODO: maybe take size instead of type?
+	if raceenabled {
+		raceReadObjectPC(t, v, getcallerpc(), abi.FuncPCABIInternal(convTnoptr))
+	}
+	if msanenabled {
+		msanread(v, t.size)
+	}
+	if asanenabled {
+		asanread(v, t.size)
+	}
+
+	x := mallocgc(t.size, t, false)
+	memmove(x, v, t.size)
+	return x
+}
+
+func convT16(val uint16) (x unsafe.Pointer) {
+	if val < uint16(len(staticuint64s)) {
+		x = unsafe.Pointer(&staticuint64s[val])
+		if goarch.BigEndian {
+			x = add(x, 6)
+		}
+	} else {
+		x = mallocgc(2, uint16Type, false)
+		*(*uint16)(x) = val
+	}
+	return
+}
+
+func convT32(val uint32) (x unsafe.Pointer) {
+	if val < uint32(len(staticuint64s)) {
+		x = unsafe.Pointer(&staticuint64s[val])
+		if goarch.BigEndian {
+			x = add(x, 4)
+		}
+	} else {
+		x = mallocgc(4, uint32Type, false)
+		*(*uint32)(x) = val
+	}
+	return
+}
+
+func convT64(val uint64) (x unsafe.Pointer) {
+	if val < uint64(len(staticuint64s)) {
+		x = unsafe.Pointer(&staticuint64s[val])
+	} else {
+		x = mallocgc(8, uint64Type, false)
+		*(*uint64)(x) = val
+	}
+	return
+}
+
+func convTstring(val string) (x unsafe.Pointer) {
+	if val == "" {
+		x = unsafe.Pointer(&zeroVal[0])
+	} else {
+		x = mallocgc(unsafe.Sizeof(val), stringType, true)
+		*(*string)(x) = val
+	}
+	return
+}
+
+func convTslice(val []byte) (x unsafe.Pointer) {
+	// Note: this must work for any element type, not just byte.
+	if (*slice)(unsafe.Pointer(&val)).array == nil {
+		x = unsafe.Pointer(&zeroVal[0])
+	} else {
+		x = mallocgc(unsafe.Sizeof(val), sliceType, true)
+		*(*[]byte)(x) = val
+	}
+	return
+}
+
+// convI2I returns the new itab to be used for the destination value
+// when converting a value with itab src to the dst interface.
+func convI2I(dst *interfacetype, src *itab) *itab {
+	if src == nil {
+		return nil
+	}
+	if src.inter == dst {
+		return src
+	}
+	return getitab(dst, src._type, false)
+}
+
+func assertI2I(inter *interfacetype, tab *itab) *itab {
+	if tab == nil {
+		// explicit conversions require non-nil interface value.
+		panic(&TypeAssertionError{nil, nil, &inter.typ, ""})
+	}
+	if tab.inter == inter {
+		return tab
+	}
+	return getitab(inter, tab._type, false)
+}
+
+func assertI2I2(inter *interfacetype, i iface) (r iface) {
+	tab := i.tab
+	if tab == nil {
+		return
+	}
+	if tab.inter != inter {
+		tab = getitab(inter, tab._type, true)
+		if tab == nil {
+			return
+		}
+	}
+	r.tab = tab
+	r.data = i.data
+	return
+}
+
+func assertE2I(inter *interfacetype, t *_type) *itab {
+	if t == nil {
+		// explicit conversions require non-nil interface value.
+		panic(&TypeAssertionError{nil, nil, &inter.typ, ""})
+	}
+	return getitab(inter, t, false)
+}
+
+func assertE2I2(inter *interfacetype, e eface) (r iface) {
+	t := e._type
+	if t == nil {
+		return
+	}
+	tab := getitab(inter, t, true)
+	if tab == nil {
+		return
+	}
+	r.tab = tab
+	r.data = e.data
+	return
+}
+
+//go:linkname reflect_ifaceE2I reflect.ifaceE2I
+func reflect_ifaceE2I(inter *interfacetype, e eface, dst *iface) {
+	*dst = iface{assertE2I(inter, e._type), e.data}
+}
+
+//go:linkname reflectlite_ifaceE2I internal/reflectlite.ifaceE2I
+func reflectlite_ifaceE2I(inter *interfacetype, e eface, dst *iface) {
+	*dst = iface{assertE2I(inter, e._type), e.data}
+}
+
+func iterate_itabs(fn func(*itab)) {
+	// Note: only runs during stop the world or with itabLock held,
+	// so no other locks/atomics needed.
+	t := itabTable
+	for i := uintptr(0); i < t.size; i++ {
+		m := *(**itab)(add(unsafe.Pointer(&t.entries), i*goarch.PtrSize))
+		if m != nil {
+			fn(m)
+		}
+	}
+}
+
+// staticuint64s is used to avoid allocating in convTx for small integer values.
+var staticuint64s = [...]uint64{
+	0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
+	0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,
+	0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
+	0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f,
+	0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27,
+	0x28, 0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f,
+	0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37,
+	0x38, 0x39, 0x3a, 0x3b, 0x3c, 0x3d, 0x3e, 0x3f,
+	0x40, 0x41, 0x42, 0x43, 0x44, 0x45, 0x46, 0x47,
+	0x48, 0x49, 0x4a, 0x4b, 0x4c, 0x4d, 0x4e, 0x4f,
+	0x50, 0x51, 0x52, 0x53, 0x54, 0x55, 0x56, 0x57,
+	0x58, 0x59, 0x5a, 0x5b, 0x5c, 0x5d, 0x5e, 0x5f,
+	0x60, 0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67,
+	0x68, 0x69, 0x6a, 0x6b, 0x6c, 0x6d, 0x6e, 0x6f,
+	0x70, 0x71, 0x72, 0x73, 0x74, 0x75, 0x76, 0x77,
+	0x78, 0x79, 0x7a, 0x7b, 0x7c, 0x7d, 0x7e, 0x7f,
+	0x80, 0x81, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87,
+	0x88, 0x89, 0x8a, 0x8b, 0x8c, 0x8d, 0x8e, 0x8f,
+	0x90, 0x91, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97,
+	0x98, 0x99, 0x9a, 0x9b, 0x9c, 0x9d, 0x9e, 0x9f,
+	0xa0, 0xa1, 0xa2, 0xa3, 0xa4, 0xa5, 0xa6, 0xa7,
+	0xa8, 0xa9, 0xaa, 0xab, 0xac, 0xad, 0xae, 0xaf,
+	0xb0, 0xb1, 0xb2, 0xb3, 0xb4, 0xb5, 0xb6, 0xb7,
+	0xb8, 0xb9, 0xba, 0xbb, 0xbc, 0xbd, 0xbe, 0xbf,
+	0xc0, 0xc1, 0xc2, 0xc3, 0xc4, 0xc5, 0xc6, 0xc7,
+	0xc8, 0xc9, 0xca, 0xcb, 0xcc, 0xcd, 0xce, 0xcf,
+	0xd0, 0xd1, 0xd2, 0xd3, 0xd4, 0xd5, 0xd6, 0xd7,
+	0xd8, 0xd9, 0xda, 0xdb, 0xdc, 0xdd, 0xde, 0xdf,
+	0xe0, 0xe1, 0xe2, 0xe3, 0xe4, 0xe5, 0xe6, 0xe7,
+	0xe8, 0xe9, 0xea, 0xeb, 0xec, 0xed, 0xee, 0xef,
+	0xf0, 0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7,
+	0xf8, 0xf9, 0xfa, 0xfb, 0xfc, 0xfd, 0xfe, 0xff,
+}
+
+// The linker redirects a reference of a method that it determined
+// unreachable to a reference to this function, so it will throw if
+// ever called.
+func unreachableMethod() {
+	throw("unreachable method called. linker bug?")
+}