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ARM: mxc: Correct data alignment in headsmp.S for CONFIG_THUMB2_KERNEL

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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.

Signed-off-by: Dave Martin <dave.martin@linaro.org>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
LAKML-Reference: 1289913217-8672-1-git-send-email-dave.martin@linaro.org
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
This commit is contained in:
Dave Martin 2010-11-16 13:13:37 +00:00 committed by Sascha Hauer
parent f61b9fc27e
commit 0575b4b83e
1 changed files with 2 additions and 0 deletions
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arch/arm/plat-mxc/ssi-fiq.S
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@ -124,6 +124,8 @@ imx_ssi_fiq_start:
1: 1:
@ return from FIQ @ return from FIQ
subs pc, lr, #4 subs pc, lr, #4
.align
imx_ssi_fiq_base: imx_ssi_fiq_base:
.word 0x0 .word 0x0
imx_ssi_fiq_rx_buffer: imx_ssi_fiq_rx_buffer: