kernel: 5.4: import wireguard backport

Rather than using the clunky, old, slower wireguard-linux-compat out of
tree module, this commit does a patch-by-patch backport of upstream's
wireguard to 5.4. This specific backport is in widespread use, being
part of SUSE's enterprise kernel, Oracle's enterprise kernel, Google's
Android kernel, Gentoo's distro kernel, and probably more I've forgotten
about. It's definately the "more proper" way of adding wireguard to a
kernel than the ugly compat.h hell of the wireguard-linux-compat repo.
And most importantly for OpenWRT, it allows using the same module
configuration code for 5.10 as for 5.4, with no need for bifurcation.

These patches are from the backport tree which is maintained in the
open here: https://git.zx2c4.com/wireguard-linux/log/?h=backport-5.4.y
I'll be sending PRs to update this as needed.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

1 files changed, 58 insertions, 0 deletions

diff --git a/target/linux/generic/backport-5.4/080-wireguard-0049-crypto-arm-chacha-fix-build-failured-when-kernel-mod.patch b/target/linux/generic/backport-5.4/080-wireguard-0049-crypto-arm-chacha-fix-build-failured-when-kernel-mod.patch
new file mode 100644
index 0000000000..392d52f205
--- /dev/null
+++ b/target/linux/generic/backport-5.4/080-wireguard-0049-crypto-arm-chacha-fix-build-failured-when-kernel-mod.patch
@@ -0,0 +1,58 @@
+From 627e2c8313065e627fe5c8c9f82cebd765f5a65e Mon Sep 17 00:00:00 2001
+From: Ard Biesheuvel <ardb@kernel.org>
+Date: Fri, 17 Jan 2020 17:43:18 +0100
+Subject: [PATCH 049/124] crypto: arm/chacha - fix build failured when kernel
+ mode NEON is disabled
+
+commit 0bc81767c5bd9d005fae1099fb39eb3688370cb1 upstream.
+
+When the ARM accelerated ChaCha driver is built as part of a configuration
+that has kernel mode NEON disabled, we expect the compiler to propagate
+the build time constant expression IS_ENABLED(CONFIG_KERNEL_MODE_NEON) in
+a way that eliminates all the cross-object references to the actual NEON
+routines, which allows the chacha-neon-core.o object to be omitted from
+the build entirely.
+
+Unfortunately, this fails to work as expected in some cases, and we may
+end up with a build error such as
+
+  chacha-glue.c:(.text+0xc0): undefined reference to `chacha_4block_xor_neon'
+
+caused by the fact that chacha_doneon() has not been eliminated from the
+object code, even though it will never be called in practice.
+
+Let's fix this by adding some IS_ENABLED(CONFIG_KERNEL_MODE_NEON) tests
+that are not strictly needed from a logical point of view, but should
+help the compiler infer that the NEON code paths are unreachable in
+those cases.
+
+Fixes: b36d8c09e710c71f ("crypto: arm/chacha - remove dependency on generic ...")
+Reported-by: Russell King <linux@armlinux.org.uk>
+Cc: Arnd Bergmann <arnd@arndb.de>
+Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
+Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
+Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
+---
+ arch/arm/crypto/chacha-glue.c | 4 ++--
+ 1 file changed, 2 insertions(+), 2 deletions(-)
+
+--- a/arch/arm/crypto/chacha-glue.c
++++ b/arch/arm/crypto/chacha-glue.c
+@@ -115,7 +115,7 @@ static int chacha_stream_xor(struct skci
+ 		if (nbytes < walk.total)
+ 			nbytes = round_down(nbytes, walk.stride);
+ 
+-		if (!neon) {
++		if (!IS_ENABLED(CONFIG_KERNEL_MODE_NEON) || !neon) {
+ 			chacha_doarm(walk.dst.virt.addr, walk.src.virt.addr,
+ 				     nbytes, state, ctx->nrounds);
+ 			state[12] += DIV_ROUND_UP(nbytes, CHACHA_BLOCK_SIZE);
+@@ -159,7 +159,7 @@ static int do_xchacha(struct skcipher_re
+ 
+ 	chacha_init_generic(state, ctx->key, req->iv);
+ 
+-	if (!neon) {
++	if (!IS_ENABLED(CONFIG_KERNEL_MODE_NEON) || !neon) {
+ 		hchacha_block_arm(state, subctx.key, ctx->nrounds);
+ 	} else {
+ 		kernel_neon_begin();