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authorDave Martin <dave.martin@linaro.org>2010-11-29 19:43:22 +0100
committerRussell King <rmk+kernel@arm.linux.org.uk>2010-11-30 13:44:23 +0000
commit7eb25ebee894ba2f8a591a83e45accc091ced19f (patch)
treeca919154dbdd4560d72a2804a7769834446210ba
parentbc8b57f08c53344d13e3b5e644c56c0355899b47 (diff)
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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>
-rw-r--r--arch/arm/vfp/vfphw.S1
1 files changed, 1 insertions, 0 deletions
diff --git a/arch/arm/vfp/vfphw.S b/arch/arm/vfp/vfphw.S
index d66cead97d2..9897dcfc16d 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