[PATCH] ARM: mxc: Correct data alignment in headsmp.S for CONFIG_THUMB2_KERNEL
dave.martin at linaro.org
Tue Nov 16 08:13:37 EST 2010
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
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:
* .long, .word, .single, .float:
.align (or .align 2)
No explicit alignment required, since Thumb-2
instructions are always 2 or 4 bytes in size.
immediately after an instruction.
Applies cleanly on v2.6.37-rc1.
Signed-off-by: Dave Martin <dave.martin at linaro.org>
arch/arm/plat-mxc/ssi-fiq.S | 2 ++
1 files changed, 2 insertions(+), 0 deletions(-)
diff --git a/arch/arm/plat-mxc/ssi-fiq.S b/arch/arm/plat-mxc/ssi-fiq.S
index 4ddce56..8397a2d 100644
@@ -124,6 +124,8 @@ imx_ssi_fiq_start:
@ return from FIQ
subs pc, lr, #4
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