Cannot load wireguard module

[Michal Suchánek]

On Wed, Mar 20, 2024 at 11:41:32PM +1100, Michael Ellerman wrote:
> Michal Suchánek <msuchanek at suse.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 at ellerman.id.au> writes:
> >> > > Michal Suchánek <msuchanek at suse.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 at zx2c4.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.

Maybe it doesn't. ppc64le is the only platform that needs the fallback,
on other platforms that have hardware-specific chacha implementation it
seems to be using pretty common feature so the fallback is rarely if
ever needed in practice.

Thanks

Michal

> 
> 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 at zx2c4.com>. All Rights Reserved.
>   
> 
> cheers