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authorDave Martin <dave.martin@linaro.org>2010-11-29 19:43:21 +0100
committerRussell King <rmk+kernel@arm.linux.org.uk>2010-11-30 13:44:23 +0000
commitbc8b57f08c53344d13e3b5e644c56c0355899b47 (patch)
parente6afec9b6808eff6dc392ac07c1552e87aebcdf7 (diff)
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 <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>
1 files changed, 2 insertions, 0 deletions
diff --git a/arch/arm/kernel/relocate_kernel.S b/arch/arm/kernel/relocate_kernel.S
index fd26f8d6515..9cf4cbf8f95 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
.long 0x0