CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS behaves a bit counterintuitively on ARM: we set it for architecture revisions v6 and up, which support any alignment for load/store instructions that operate on bytes, half words or words. However, load/store double word and load store multiple instructions still require 32-bit alignment, and using them on unaligned quantities results in costly alignment traps that have to be fixed up by the kernel's fixup code. Fortunately, the unaligned accessors do the right thing here: on architectures that really tolerate any misalignment, they simply resolve to the aligned accessors, while on ARMv6+ (which uses the packed struct wrappers for unaligned accesses), they result in load/store sequences that avoid the instructions that require 32-bit alignment. Since there is not really a downside to using the unaligned accessors on aligned paths for architectures other than ARM that define CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS, let's switch to them in a couple of places in the crypto code. Note that all patches are against code that has been observed to be emitted with ldm or ldrd instructions when building ARM's multi_v7_defconfig. Ard Biesheuvel (3): crypto: memneq - use unaligned accessors for aligned fast path crypto: crypto_xor - use unaligned accessors for aligned fast path crypto: siphash - drop _aligned variants crypto/algapi.c | 7 +- crypto/memneq.c | 24 +++-- include/crypto/algapi.h | 11 +- include/linux/siphash.h | 106 +++++++++----------- lib/siphash.c | 103 ++----------------- 5 files changed, 83 insertions(+), 168 deletions(-) -- 2.11.0
