target/linux/generic/backport-5.4/080-wireguard-0049-crypto-arm-chacha-fix-build-failured-when-kernel-mod.patch

   1 From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
   2 From: Ard Biesheuvel <ardb@kernel.org>
   3 Date: Fri, 17 Jan 2020 17:43:18 +0100
   4 Subject: [PATCH] crypto: arm/chacha - fix build failured when kernel mode NEON
   5  is disabled
   6
   7 commit 0bc81767c5bd9d005fae1099fb39eb3688370cb1 upstream.
   8
   9 When the ARM accelerated ChaCha driver is built as part of a configuration
  10 that has kernel mode NEON disabled, we expect the compiler to propagate
  11 the build time constant expression IS_ENABLED(CONFIG_KERNEL_MODE_NEON) in
  12 a way that eliminates all the cross-object references to the actual NEON
  13 routines, which allows the chacha-neon-core.o object to be omitted from
  14 the build entirely.
  15
  16 Unfortunately, this fails to work as expected in some cases, and we may
  17 end up with a build error such as
  18
  19   chacha-glue.c:(.text+0xc0): undefined reference to `chacha_4block_xor_neon'
  20
  21 caused by the fact that chacha_doneon() has not been eliminated from the
  22 object code, even though it will never be called in practice.
  23
  24 Let's fix this by adding some IS_ENABLED(CONFIG_KERNEL_MODE_NEON) tests
  25 that are not strictly needed from a logical point of view, but should
  26 help the compiler infer that the NEON code paths are unreachable in
  27 those cases.
  28
  29 Fixes: b36d8c09e710c71f ("crypto: arm/chacha - remove dependency on generic ...")
  30 Reported-by: Russell King <linux@armlinux.org.uk>
  31 Cc: Arnd Bergmann <arnd@arndb.de>
  32 Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
  33 Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
  34 Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
  35 ---
  36  arch/arm/crypto/chacha-glue.c | 4 ++--
  37  1 file changed, 2 insertions(+), 2 deletions(-)
  38
  39 --- a/arch/arm/crypto/chacha-glue.c
  40 +++ b/arch/arm/crypto/chacha-glue.c
  41 @@ -115,7 +115,7 @@ static int chacha_stream_xor(struct skci
  42                 if (nbytes < walk.total)
  43                         nbytes = round_down(nbytes, walk.stride);
  44
  45 -               if (!neon) {
  46 +               if (!IS_ENABLED(CONFIG_KERNEL_MODE_NEON) || !neon) {
  47                         chacha_doarm(walk.dst.virt.addr, walk.src.virt.addr,
  48                                      nbytes, state, ctx->nrounds);
  49                         state[12] += DIV_ROUND_UP(nbytes, CHACHA_BLOCK_SIZE);
  50 @@ -159,7 +159,7 @@ static int do_xchacha(struct skcipher_re
  51
  52         chacha_init_generic(state, ctx->key, req->iv);
  53
  54 -       if (!neon) {
  55 +       if (!IS_ENABLED(CONFIG_KERNEL_MODE_NEON) || !neon) {
  56                 hchacha_block_arm(state, subctx.key, ctx->nrounds);
  57         } else {
  58                 kernel_neon_begin();