crypto: lib/curve25519 - re-add selftests

Somehow these were dropped when Zinc was being integrated, which is
problematic, because testing the library interface for Curve25519 is
important.. This commit simply adds them back and wires them in in the
same way that the blake2s selftests are wired in.
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

lib/crypto/Makefile

@@ -36,4 +36,5 @@ libsha256-y					:= sha256.o
 ifneq ($(CONFIG_CRYPTO_MANAGER_DISABLE_TESTS),y)
 libblake2s-y					+= blake2s-selftest.o
 libchacha20poly1305-y				+= chacha20poly1305-selftest.o
+libcurve25519-y					+= curve25519-selftest.o
 endif

lib/crypto/curve25519.c

@@ -13,6 +13,8 @@
 #include <linux/module.h>
 #include <linux/init.h>
 
+bool curve25519_selftest(void);
+
 const u8 curve25519_null_point[CURVE25519_KEY_SIZE] __aligned(32) = { 0 };
 const u8 curve25519_base_point[CURVE25519_KEY_SIZE] __aligned(32) = { 9 };
 
@@ -20,6 +22,21 @@ EXPORT_SYMBOL(curve25519_null_point);
 EXPORT_SYMBOL(curve25519_base_point);
 EXPORT_SYMBOL(curve25519_generic);
 
+static int __init mod_init(void)
+{
+	if (!IS_ENABLED(CONFIG_CRYPTO_MANAGER_DISABLE_TESTS) &&
+	    WARN_ON(!curve25519_selftest()))
+		return -ENODEV;
+	return 0;
+}
+
+static void __exit mod_exit(void)
+{
+}
+
+module_init(mod_init);
+module_exit(mod_exit);
+
 MODULE_LICENSE("GPL v2");
 MODULE_DESCRIPTION("Curve25519 scalar multiplication");
 MODULE_AUTHOR("Jason A. Donenfeld <Jason@zx2c4.com>");