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| author | Dave Martin <dave.martin@linaro.org> | 2010-11-30 13:05:10 +0100 |
|---|---|---|
| committer | Russell King <rmk+kernel@arm.linux.org.uk> | 2010-11-30 14:44:27 +0100 |
| commit | 618d9c8f9e554b5eaaca3f8e55a28e1a928a8571 (patch) | |
| tree | eed55141c126d49aca9a5299e629f78d991ef07e /arch | |
| parent | ARM: 6507/1: RealView: Correct data alignment in headsmp.S for CONFIG_THUMB2_... (diff) | |
| download | linux-618d9c8f9e554b5eaaca3f8e55a28e1a928a8571.tar.xz linux-618d9c8f9e554b5eaaca3f8e55a28e1a928a8571.zip | |
ARM: 6508/1: vexpress: 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>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/arm/mach-vexpress/headsmp.S | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/arch/arm/mach-vexpress/headsmp.S b/arch/arm/mach-vexpress/headsmp.S index 8a78ff68e1ee..7a3f0632947c 100644 --- a/arch/arm/mach-vexpress/headsmp.S +++ b/arch/arm/mach-vexpress/headsmp.S @@ -35,5 +35,6 @@ pen: ldr r7, [r6] */ b secondary_startup + .align 1: .long . .long pen_release |