diff options
| author | Dave Martin <dave.martin@linaro.org> | 2010-11-29 19:43:22 +0100 |
|---|---|---|
| committer | Russell King <rmk+kernel@arm.linux.org.uk> | 2010-11-30 13:44:23 +0000 |
| commit | 7eb25ebee894ba2f8a591a83e45accc091ced19f (patch) | |
| tree | ca919154dbdd4560d72a2804a7769834446210ba /arch | |
| parent | bc8b57f08c53344d13e3b5e644c56c0355899b47 (diff) | |
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>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/arm/vfp/vfphw.S | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/arch/arm/vfp/vfphw.S b/arch/arm/vfp/vfphw.S index d66cead97d28..9897dcfc16d6 100644 --- a/arch/arm/vfp/vfphw.S +++ b/arch/arm/vfp/vfphw.S @@ -206,6 +206,7 @@ ENTRY(vfp_save_state) mov pc, lr ENDPROC(vfp_save_state) + .align last_VFP_context_address: .word last_VFP_context |