2 files changed, 14 insertions, 0 deletions
diff --git a/src/cmd/link/internal/ld/deadcode.go b/src/cmd/link/internal/ld/deadcode.go
index c0969b25b0..c687565878 100644
--- a/src/cmd/link/internal/ld/deadcode.go
+++ b/src/cmd/link/internal/ld/deadcode.go
@@ -180,6 +180,14 @@ func (d *deadcodePass) flood() {
 				// converted to an interface, i.e. should have UsedInIface set. See the
 				// comment below for why we need to unset the Reachable bit and re-mark it.
 				rs := r.Sym()
+				if d.ldr.IsItab(rs) {
+					// This relocation can also point at an itab, in which case it
+					// means "the _type field of that itab".
+					rs = decodeItabType(d.ldr, d.ctxt.Arch, rs)
+				}
+				if !d.ldr.IsGoType(rs) && !d.ctxt.linkShared {
+					panic(fmt.Sprintf("R_USEIFACE in %s references %s which is not a type or itab", d.ldr.SymName(symIdx), d.ldr.SymName(rs)))
+				}
 				if !d.ldr.AttrUsedInIface(rs) {
 					d.ldr.SetAttrUsedInIface(rs, true)
 					if d.ldr.AttrReachable(rs) {
diff --git a/src/cmd/link/internal/ld/decodesym.go b/src/cmd/link/internal/ld/decodesym.go
index c01d6c1163..05da11ec1e 100644
--- a/src/cmd/link/internal/ld/decodesym.go
+++ b/src/cmd/link/internal/ld/decodesym.go
@@ -300,3 +300,9 @@ func findShlibSection(ctxt *Link, path string, addr uint64) *elf.Section {
 func decodetypeGcprogShlib(ctxt *Link, data []byte) uint64 {
 	return decodeInuxi(ctxt.Arch, data[2*int32(ctxt.Arch.PtrSize)+8+1*int32(ctxt.Arch.PtrSize):], ctxt.Arch.PtrSize)
 }
+
+// decodeItabType returns the itab._type field from an itab.
+func decodeItabType(ldr *loader.Loader, arch *sys.Arch, symIdx loader.Sym) loader.Sym {
+	relocs := ldr.Relocs(symIdx)
+	return decodeRelocSym(ldr, symIdx, &relocs, int32(arch.PtrSize))
+}