linux/arch/arm/vfp
Dave Martin 7eb25ebee8 ARM: 6498/1: vfp: Correct data alignment for CONFIG_THUMB2_KERNEL
Directives such as .long and .word do not magically cause the
assembler location counter to become aligned in gas.  As a result,
using these directives in code sections can result in misaligned
data words when building a Thumb-2 kernel (CONFIG_THUMB2_KERNEL).

This is a Bad Thing, since the ABI permits the compiler to assume
that fundamental types of word size or above are word- aligned when
accessing them from C.  If the data is not really word-aligned,
this can cause impaired performance and stray alignment faults in
some circumstances.

In general, the following rules should be applied when using data
word declaration directives inside code sections:

    * .quad and .double:
         .align 3

    * .long, .word, .single, .float:
         .align (or .align 2)

    * .short:
        No explicit alignment required, since Thumb-2
        instructions are always 2 or 4 bytes in size.
        immediately after an instruction.

Reviewed-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Dave Martin <dave.martin@linaro.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
2010-11-30 13:44:23 +00:00
..
Makefile kbuild: enable 'make AFLAGS=...' to add additional options to AS 2007-10-15 21:59:31 +02:00
entry.S Thumb-2: Add some .align statements to the .S files 2009-07-24 12:32:52 +01:00
vfp.h [ARM] 5387/1: Add ptrace VFP support on ARM 2009-02-12 10:59:43 +00:00
vfpdouble.c [ARM] vfp: fix fuitod/fsitod instructions 2008-01-10 17:07:08 +00:00
vfphw.S ARM: 6498/1: vfp: Correct data alignment for CONFIG_THUMB2_KERNEL 2010-11-30 13:44:23 +00:00
vfpinstr.h [ARM] 4583/1: ARMv7: Add VFPv3 support 2008-01-26 14:41:28 +00:00
vfpmodule.c ARM: 6203/1: Make VFPv3 usable on ARMv6 2010-07-09 14:41:34 +01:00
vfpsingle.c [ARM] Remove unnecessary asm/ptrace.h from VFP support code 2007-04-22 10:56:40 +01:00