From: Ard Biesheuvel ardb@kernel.org
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: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- 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();