Adding upstream version 0.10.5.

Signed-off-by: Daniel Baumann <daniel@debian.org>

internal/runtime/type.go

@@ -0,0 +1,98 @@
+package runtime
+
+import (
+	"reflect"
+	"sync"
+	"unsafe"
+)
+
+type SliceHeader struct {
+	Data unsafe.Pointer
+	Len  int
+	Cap  int
+}
+
+const (
+	maxAcceptableTypeAddrRange = 1024 * 1024 * 2 // 2 Mib
+)
+
+type TypeAddr struct {
+	BaseTypeAddr uintptr
+	MaxTypeAddr  uintptr
+	AddrRange    uintptr
+	AddrShift    uintptr
+}
+
+var (
+	typeAddr *TypeAddr
+	once     sync.Once
+)
+
+//go:linkname typelinks reflect.typelinks
+func typelinks() ([]unsafe.Pointer, [][]int32)
+
+//go:linkname rtypeOff reflect.rtypeOff
+func rtypeOff(unsafe.Pointer, int32) unsafe.Pointer
+
+func AnalyzeTypeAddr() *TypeAddr {
+	once.Do(func() {
+		sections, offsets := typelinks()
+		if len(sections) != 1 {
+			return
+		}
+		if len(offsets) != 1 {
+			return
+		}
+		section := sections[0]
+		offset := offsets[0]
+		var (
+			min         uintptr = uintptr(^uint(0))
+			max         uintptr = 0
+			isAligned64         = true
+			isAligned32         = true
+		)
+		for i := 0; i < len(offset); i++ {
+			typ := (*Type)(rtypeOff(section, offset[i]))
+			addr := uintptr(unsafe.Pointer(typ))
+			if min > addr {
+				min = addr
+			}
+			if max < addr {
+				max = addr
+			}
+			if typ.Kind() == reflect.Ptr {
+				addr = uintptr(unsafe.Pointer(typ.Elem()))
+				if min > addr {
+					min = addr
+				}
+				if max < addr {
+					max = addr
+				}
+			}
+			isAligned64 = isAligned64 && (addr-min)&63 == 0
+			isAligned32 = isAligned32 && (addr-min)&31 == 0
+		}
+		addrRange := max - min
+		if addrRange == 0 {
+			return
+		}
+		var addrShift uintptr
+		if isAligned64 {
+			addrShift = 6
+		} else if isAligned32 {
+			addrShift = 5
+		}
+		cacheSize := addrRange >> addrShift
+		if cacheSize > maxAcceptableTypeAddrRange {
+			return
+		}
+		typeAddr = &TypeAddr{
+			BaseTypeAddr: min,
+			MaxTypeAddr:  max,
+			AddrRange:    addrRange,
+			AddrShift:    addrShift,
+		}
+	})
+
+	return typeAddr
+}