netdev - Re: Cannot load wireguard module

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Message-ID: <87le6dyt1f.fsf@mail.lhotse>
Date: Wed, 20 Mar 2024 23:41:32 +1100
From: Michael Ellerman <mpe@...erman.id.au>
To: Michal Suchánek <msuchanek@...e.de>
Cc: netdev@...r.kernel.org, "Jason A. Donenfeld" <Jason@...c4.com>,
 linuxppc-dev@...ts.ozlabs.org, wireguard@...ts.zx2c4.com,
 dtsen@...ux.ibm.com, Herbert Xu <herbert@...dor.apana.org.au>
Subject: Re: Cannot load wireguard module

Michal Suchánek <msuchanek@...e.de> writes:
> On Mon, Mar 18, 2024 at 06:08:55PM +0100, Michal Suchánek wrote:
>> On Mon, Mar 18, 2024 at 10:50:49PM +1100, Michael Ellerman wrote:
>> > Michael Ellerman <mpe@...erman.id.au> writes:
>> > > Michal Suchánek <msuchanek@...e.de> writes:
>> > >> Hello,
>> > >>
>> > >> I cannot load the wireguard module.
>> > >>
>> > >> Loading the module provides no diagnostic other than 'No such device'.
>> > >>
>> > >> Please provide maningful diagnostics for loading software-only driver,
>> > >> clearly there is no particular device needed.
>> > >
>> > > Presumably it's just bubbling up an -ENODEV from somewhere.
>> > >
>> > > Can you get a trace of it?
>> > >
>> > > Something like:
>> > >
>> > >   # trace-cmd record -p function_graph -F modprobe wireguard
>
> Attached.

Sorry :/, you need to also trace children of modprobe, with -c.

But, I was able to reproduce the same issue here.

On a P9, a kernel with CONFIG_CRYPTO_CHACHA20_P10=n everything works:

  $ modprobe -v wireguard
  insmod /lib/modules/6.8.0/kernel/net/ipv4/udp_tunnel.ko
  insmod /lib/modules/6.8.0/kernel/net/ipv6/ip6_udp_tunnel.ko
  insmod /lib/modules/6.8.0/kernel/lib/crypto/libchacha.ko
  insmod /lib/modules/6.8.0/kernel/lib/crypto/libchacha20poly1305.ko
  insmod /lib/modules/6.8.0/kernel/drivers/net/wireguard/wireguard.ko
  [   19.180564][  T692] wireguard: allowedips self-tests: pass
  [   19.185080][  T692] wireguard: nonce counter self-tests: pass
  [   19.310438][  T692] wireguard: ratelimiter self-tests: pass
  [   19.310639][  T692] wireguard: WireGuard 1.0.0 loaded. See www.wireguard.com for information.
  [   19.310746][  T692] wireguard: Copyright (C) 2015-2019 Jason A. Donenfeld <Jason@...c4.com>. All Rights Reserved.


If I build CONFIG_CRYPTO_CHACHA20_P10 as a module then it breaks:

  $ modprobe -v wireguard
  insmod /lib/modules/6.8.0/kernel/net/ipv4/udp_tunnel.ko
  insmod /lib/modules/6.8.0/kernel/net/ipv6/ip6_udp_tunnel.ko
  insmod /lib/modules/6.8.0/kernel/lib/crypto/libchacha.ko
  insmod /lib/modules/6.8.0/kernel/arch/powerpc/crypto/chacha-p10-crypto.ko
  modprobe: ERROR: could not insert 'wireguard': No such device


The ENODEV is coming from module_cpu_feature_match(), which blocks the
driver from loading on non-p10.

Looking at other arches (arm64 at least) it seems like the driver should
instead be loading but disabling the p10 path. Which then allows
chacha_crypt_arch() to exist, and it has a fallback to use
chacha_crypt_generic().

I don't see how module_cpu_feature_match() can co-exist with the driver
also providing a fallback. Hopefully someone who knows crypto better
than me can explain it.

This diff fixes it for me:

diff --git a/arch/powerpc/crypto/chacha-p10-glue.c b/arch/powerpc/crypto/chacha-p10-glue.c
index 74fb86b0d209..9d2c30b0904c 100644
--- a/arch/powerpc/crypto/chacha-p10-glue.c
+++ b/arch/powerpc/crypto/chacha-p10-glue.c
@@ -197,6 +197,9 @@ static struct skcipher_alg algs[] = {
 
 static int __init chacha_p10_init(void)
 {
+	if (!cpu_has_feature(PPC_FEATURE2_ARCH_3_1))
+		return 0;
+
 	static_branch_enable(&have_p10);
 
 	return crypto_register_skciphers(algs, ARRAY_SIZE(algs));
@@ -207,7 +210,7 @@ static void __exit chacha_p10_exit(void)
 	crypto_unregister_skciphers(algs, ARRAY_SIZE(algs));
 }
 
-module_cpu_feature_match(PPC_MODULE_FEATURE_P10, chacha_p10_init);
+module_init(chacha_p10_init);
 module_exit(chacha_p10_exit);
 
 MODULE_DESCRIPTION("ChaCha and XChaCha stream ciphers (P10 accelerated)");


Giving me:

  $ modprobe -v wireguard
  insmod /lib/modules/6.8.0-dirty/kernel/net/ipv4/udp_tunnel.ko
  insmod /lib/modules/6.8.0-dirty/kernel/net/ipv6/ip6_udp_tunnel.ko
  insmod /lib/modules/6.8.0-dirty/kernel/lib/crypto/libchacha.ko
  insmod /lib/modules/6.8.0-dirty/kernel/arch/powerpc/crypto/chacha-p10-crypto.ko
  insmod /lib/modules/6.8.0-dirty/kernel/lib/crypto/libchacha20poly1305.ko
  insmod /lib/modules/6.8.0-dirty/kernel/drivers/net/wireguard/wireguard.ko
  [   19.657941][  T718] wireguard: allowedips self-tests: pass
  [   19.662501][  T718] wireguard: nonce counter self-tests: pass
  [   19.782933][  T718] wireguard: ratelimiter self-tests: pass
  [   19.783114][  T718] wireguard: WireGuard 1.0.0 loaded. See www.wireguard.com for information.
  [   19.783223][  T718] wireguard: Copyright (C) 2015-2019 Jason A. Donenfeld <Jason@...c4.com>. All Rights Reserved.
  

cheers