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authorDave Martin <dave.martin@linaro.org>2010-11-16 08:13:37 -0500
committerSascha Hauer <s.hauer@pengutronix.de>2011-04-12 03:48:10 -0400
commit0575b4b83edb0a766a9c1518a5da57780f386340 (patch)
treedec934c475cd2b9b27a4e93cd7ef8bc08b0dfdee /arch/arm/plat-mxc
parentf61b9fc27e5b61dbc330696f040cc66ba1dbcbaa (diff)
ARM: mxc: Correct data alignment in headsmp.S 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. 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>
Diffstat (limited to 'arch/arm/plat-mxc')
-rw-r--r--arch/arm/plat-mxc/ssi-fiq.S2
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 4ddce565b353..8397a2dd19f2 100644
--- a/arch/arm/plat-mxc/ssi-fiq.S
+++ b/arch/arm/plat-mxc/ssi-fiq.S
@@ -124,6 +124,8 @@ imx_ssi_fiq_start:
1241: 1241:
125 @ return from FIQ 125 @ return from FIQ
126 subs pc, lr, #4 126 subs pc, lr, #4
127
128 .align
127imx_ssi_fiq_base: 129imx_ssi_fiq_base:
128 .word 0x0 130 .word 0x0
129imx_ssi_fiq_rx_buffer: 131imx_ssi_fiq_rx_buffer: