On 18 January 2011 06:00, Nicolas Pitre [off-list ref] wrote:

On Mon, 17 Jan 2011, Russell King - ARM Linux wrote:

quoted

Add additional instructions to our assembly bitops functions to ensure
that they only operate on word-aligned pointers. ?This will be necessary
when we switch these operations to use the word-based exclusive
operations.

Signed-off-by: Russell King <redacted>

This breaks the Thumb2 kernel build:

?AS ? ? ?arch/arm/lib/changebit.o
arch/arm/lib/changebit.S: Assembler messages:
arch/arm/lib/changebit.S:16: Error: Thumb does not support negative register indexing -- `strne r1,[r1,-r1]'

I also wonder what happens with a misaligned ldrex/strex... Does the
alignment trap get invoked?

According to the ARM ARM, unaligned ldrex/strex should generate an
alignment fault on ARMv6 (with SCTLR.U bit set) and ARMv7.

-- 
Catalin