From bc8b57f08c53344d13e3b5e644c56c0355899b47 Mon Sep 17 00:00:00 2001 From: Dave Martin Date: Mon, 29 Nov 2010 19:43:21 +0100 Subject: [PATCH] ARM: 6497/1: kexec: Correct data alignment 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 Signed-off-by: Dave Martin Acked-by: Catalin Marinas Signed-off-by: Russell King --- arch/arm/kernel/relocate_kernel.S | 2 ++ 1 file changed, 2 insertions(+) diff --git a/arch/arm/kernel/relocate_kernel.S b/arch/arm/kernel/relocate_kernel.S index fd26f8d65151..9cf4cbf8f95b 100644 --- a/arch/arm/kernel/relocate_kernel.S +++ b/arch/arm/kernel/relocate_kernel.S @@ -59,6 +59,8 @@ relocate_new_kernel: ldr r2,kexec_boot_atags mov pc,lr + .align + .globl kexec_start_address kexec_start_address: .long 0x0 -- 2.20.1