Add gohacks.Slice/StringHeader.

See https://github.com/golang/go/issues/19367 for rationale. Note that the
upstream decision arrived at in that thread, while useful for some of our use
cases, doesn't account for all of our SliceHeader use cases (we often use
SliceHeader to extract pointers from slices in a way that avoids bounds
checking and/or handles nil slices correctly) and also doesn't exist yet.

PiperOrigin-RevId: 358071574

1 files changed, 5 insertions, 4 deletions

diff --git a/pkg/fdchannel/fdchannel_unsafe.go b/pkg/fdchannel/fdchannel_unsafe.go
index b253a8fdd..0ebdedf26 100644
--- a/pkg/fdchannel/fdchannel_unsafe.go
+++ b/pkg/fdchannel/fdchannel_unsafe.go
@@ -20,9 +20,10 @@ package fdchannel
 
 import (
 	"fmt"
-	"reflect"
 	"syscall"
 	"unsafe"
+
+	"gvisor.dev/gvisor/pkg/gohacks"
 )
 
 // int32 is the real type of a file descriptor.
@@ -53,10 +54,10 @@ func (ep *Endpoint) Init(sockfd int) {
 	// sendmsg+recvmsg for a zero-length datagram is slightly faster than
 	// sendmsg+recvmsg for a single byte over a stream socket.
 	cmsgSlice := make([]byte, syscall.CmsgSpace(sizeofInt32))
-	cmsgReflect := (*reflect.SliceHeader)(unsafe.Pointer(&cmsgSlice))
+	cmsgSliceHdr := (*gohacks.SliceHeader)(unsafe.Pointer(&cmsgSlice))
 	ep.sockfd = int32(sockfd)
-	ep.msghdr.Control = (*byte)(unsafe.Pointer(cmsgReflect.Data))
-	ep.cmsg = (*syscall.Cmsghdr)(unsafe.Pointer(cmsgReflect.Data))
+	ep.msghdr.Control = (*byte)(cmsgSliceHdr.Data)
+	ep.cmsg = (*syscall.Cmsghdr)(cmsgSliceHdr.Data)
 	// ep.msghdr.Controllen and ep.cmsg.* are mutated by recvmsg(2), so they're
 	// set before calling sendmsg/recvmsg.
 }