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authorDave Martin <dave.martin@linaro.org>2010-11-30 13:04:36 +0100
committerRussell King <rmk+kernel@arm.linux.org.uk>2010-11-30 13:44:27 +0000
commit725ca4adaea07460accd4622d44bcc7eaa34da09 (patch)
tree3652a5b984abfb102a31bc80897c2d79f0e104c7
parenta75e5248c51af1eaeed936be6bd3497b93f09685 (diff)
ARM: 6507/1: RealView: 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. 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/mach-realview/headsmp.S1
1 files changed, 1 insertions, 0 deletions
diff --git a/arch/arm/mach-realview/headsmp.S b/arch/arm/mach-realview/headsmp.S
index 4075473cf68..b34be4554d4 100644
--- a/arch/arm/mach-realview/headsmp.S
+++ b/arch/arm/mach-realview/headsmp.S
@@ -35,5 +35,6 @@ pen: ldr r7, [r6]
*/
b secondary_startup
+ .align
1: .long .
.long pen_release