cmd/link/internal/loader: fix linknames from FIPS 140 frozen tree

blockedLinknames was updated in CL 635676 after the lib/fips140 zip
mechanism was last tested. linknames from crypto/internal/fips140/v1.0.0
need to be allowed if they'd be allowed from crypto/internal/fips140.

Change-Id: I6a6a4656022118d4739ae14831f2ad721951c192
Reviewed-on: https://go-review.googlesource.com/c/go/+/645195
Reviewed-by: Michael Pratt <[email protected]>
Auto-Submit: Filippo Valsorda <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Roland Shoemaker <[email protected]>

Author: FiloSottile

src/cmd/link/internal/loader/loader.go

@@ -2394,6 +2394,16 @@ func (l *Loader) checkLinkname(pkg, name string, s Sym) {
 			if pkg == p {
 				return // pkg is allowed
 			}
+			// crypto/internal/fips140/vX.Y.Z/... is the frozen version of
+			// crypto/internal/fips140/... and is similarly allowed.
+			if strings.HasPrefix(pkg, "crypto/internal/fips140/v") {
+				parts := strings.Split(pkg, "/")
+				parts = append(parts[:3], parts[4:]...)
+				pkg := strings.Join(parts, "/")
+				if pkg == p {
+					return
+				}
+			}
 		}
 		error()
 	}