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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:b36d8c09e7("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> (cherry picked from commit0bc81767c5) Bug: 152722841 Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> Signed-off-by: Greg Kroah-Hartman <gregkh@google.com> Change-Id: I073e88ef1ebcf2c1cd0cf3ac75833bb043e18649
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.