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, 47 insertions, 0 deletions

diff --git a/target/linux/generic/backport-5.4/080-wireguard-0060-crypto-x86-curve25519-Remove-unused-carry-variables.patch b/target/linux/generic/backport-5.4/080-wireguard-0060-crypto-x86-curve25519-Remove-unused-carry-variables.patch
new file mode 100644
index 0000000000..9c7c3c7bcc
--- /dev/null
+++ b/target/linux/generic/backport-5.4/080-wireguard-0060-crypto-x86-curve25519-Remove-unused-carry-variables.patch
@@ -0,0 +1,47 @@
+From 9cfd2787b0b37940c656c6ea5fede6b3c360f0e5 Mon Sep 17 00:00:00 2001
+From: Herbert Xu <herbert@gondor.apana.org.au>
+Date: Thu, 23 Jul 2020 17:50:48 +1000
+Subject: [PATCH 060/124] crypto: x86/curve25519 - Remove unused carry
+ variables
+
+commit 054a5540fb8f7268e2c79e9deab4242db15c8cba upstream.
+
+The carry variables are assigned but never used, which upsets
+the compiler.  This patch removes them.
+
+Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
+Reviewed-by: Karthikeyan Bhargavan <karthik.bhargavan@gmail.com>
+Acked-by: Jason A. Donenfeld <Jason@zx2c4.com>
+Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
+Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
+---
+ arch/x86/crypto/curve25519-x86_64.c | 6 ++----
+ 1 file changed, 2 insertions(+), 4 deletions(-)
+
+--- a/arch/x86/crypto/curve25519-x86_64.c
++++ b/arch/x86/crypto/curve25519-x86_64.c
+@@ -948,10 +948,8 @@ static void store_felem(u64 *b, u64 *f)
+ {
+ 	u64 f30 = f[3U];
+ 	u64 top_bit0 = f30 >> (u32)63U;
+-	u64 carry0;
+ 	u64 f31;
+ 	u64 top_bit;
+-	u64 carry;
+ 	u64 f0;
+ 	u64 f1;
+ 	u64 f2;
+@@ -970,11 +968,11 @@ static void store_felem(u64 *b, u64 *f)
+ 	u64 o2;
+ 	u64 o3;
+ 	f[3U] = f30 & (u64)0x7fffffffffffffffU;
+-	carry0 = add_scalar(f, f, (u64)19U * top_bit0);
++	add_scalar(f, f, (u64)19U * top_bit0);
+ 	f31 = f[3U];
+ 	top_bit = f31 >> (u32)63U;
+ 	f[3U] = f31 & (u64)0x7fffffffffffffffU;
+-	carry = add_scalar(f, f, (u64)19U * top_bit);
++	add_scalar(f, f, (u64)19U * top_bit);
+ 	f0 = f[0U];
+ 	f1 = f[1U];
+ 	f2 = f[2U];