From 077248fcce5edabb1b77ba3269e6c72341769d94 Mon Sep 17 00:00:00 2001 From: Dave Martin Date: Mon, 29 Nov 2010 19:43:23 +0100 Subject: ARM: 6499/1: Thumb-2: Correct data alignment for CONFIG_THUMB2_KERNEL in bootp/init.S 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 Signed-off-by: Dave Martin Acked-by: Catalin Marinas Signed-off-by: Russell King --- arch/arm/boot/bootp/init.S | 2 ++ 1 file changed, 2 insertions(+) (limited to 'arch/arm/boot/bootp') diff --git a/arch/arm/boot/bootp/init.S b/arch/arm/boot/bootp/init.S index 8b0de41c3dcb..78b508075161 100644 --- a/arch/arm/boot/bootp/init.S +++ b/arch/arm/boot/bootp/init.S @@ -73,6 +73,8 @@ move: ldmia r4!, {r7 - r10} @ move 32-bytes at a time .size _start, . - _start + .align + .type data,#object data: .word initrd_start @ source initrd address .word initrd_phys @ destination initrd address -- cgit v1.2.3