On Fri, Jan 17, 2020 at 05:43:18PM +0100, Ard Biesheuvel wrote:
> 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@xxxxxxxxxxxxxxx>
> Cc: Arnd Bergmann <arnd@xxxxxxxx>
> Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
> ---
> arch/arm/crypto/chacha-glue.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
Patch applied. Thanks.
--
Email: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
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