Support rngd on arm64

Although it does not do anything, as there is no CPU rng on arm64 at present.

Signed-off-by: Justin Cormack <justin.cormack@docker.com>

pkg/rngd/Makefile

@@ -1,5 +1,4 @@
 IMAGE=rngd
 DEPS:=$(wildcard cmd/rngd/*.go) $(shell find cmd/rngd/vendor)
-ARCHES=x86_64
 
 include ../package.mk

pkg/rngd/cmd/rngd/main.go

@@ -2,10 +2,14 @@
 
 package main
 
+// int rndaddentropy;
+import "C"
+
 import (
 	"flag"
 	"log"
 	"os"
+	"unsafe"
 
 	"golang.org/x/sys/unix"
 )
@@ -69,3 +73,24 @@ func main() {
 		}
 	}
 }
+
+type randInfo struct {
+	entropyCount int
+	size         int
+	buf          uint64
+}
+
+func writeEntropy(random *os.File) (int, error) {
+	r, err := rand()
+	if err != nil {
+		// assume can fail occasionally
+		return 0, nil
+	}
+	const entropy = 64 // they are good random numbers, Brent
+	info := randInfo{entropy, 8, r}
+	ret, _, err := unix.Syscall(unix.SYS_IOCTL, uintptr(random.Fd()), uintptr(C.rndaddentropy), uintptr(unsafe.Pointer(&info)))
+	if ret == 0 {
+		return 8, nil
+	}
+	return 0, err
+}

pkg/rngd/cmd/rngd/rng_linux_amd64.go

@@ -37,10 +37,6 @@ import "C"
 import (
 	"errors"
 	"flag"
-	"os"
-	"unsafe"
-
-	"golang.org/x/sys/unix"
 )
 
 var disableRdrand = flag.Bool("disable-rdrand", false, "Disable use of RDRAND")
@@ -48,12 +44,6 @@ var disableRdseed = flag.Bool("disable-rdseed", false, "Disable use of RDSEED")
 
 var hasRdrand, hasRdseed bool
 
-type randInfo struct {
-	entropyCount int
-	size         int
-	buf          uint64
-}
-
 func initRand() bool {
 	hasRdrand = C.hasrdrand() == 1 && !*disableRdrand
 	hasRdseed = C.hasrdseed() == 1 && !*disableRdseed
@@ -72,18 +62,3 @@ func rand() (uint64, error) {
 	}
 	return 0, errors.New("No randomness available")
 }
-
-func writeEntropy(random *os.File) (int, error) {
-	r, err := rand()
-	if err != nil {
-		// assume can fail occasionally
-		return 0, nil
-	}
-	const entropy = 64 // they are good random numbers, Brent
-	info := randInfo{entropy, 8, r}
-	ret, _, err := unix.Syscall(unix.SYS_IOCTL, uintptr(random.Fd()), uintptr(C.rndaddentropy), uintptr(unsafe.Pointer(&info)))
-	if ret == 0 {
-		return 8, nil
-	}
-	return 0, err
-}

pkg/rngd/cmd/rngd/rng_linux_arm64.go

@@ -0,0 +1,21 @@
+package main
+
+// #include <linux/random.h>
+//
+// int rndaddentropy = RNDADDENTROPY;
+//
+import "C"
+
+import (
+	"errors"
+)
+
+// No standard RNG on arm64
+
+func initRand() bool {
+	return false
+}
+
+func rand() (uint64, error) {
+	return 0, errors.New("No randomness available")
+}

pkg/rngd/cmd/rngd/rng_unsupported.go

@@ -1,4 +1,4 @@
-// +build !linux !amd64
+// +build !linux !amd64,!arm64
 
 package main