diff options
| author | Dave Martin | 2010-11-29 19:43:21 +0100 |
|---|---|---|
| committer | Russell King | 2010-11-30 13:44:23 +0000 |
| commit | bc8b57f08c53344d13e3b5e644c56c0355899b47 (patch) | |
| tree | 5474a82e8341eb06ceac9bba0eeb9a1415130d20 /arch/arm/kernel | |
| parent | e6afec9b6808eff6dc392ac07c1552e87aebcdf7 (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>
Diffstat (limited to 'arch/arm/kernel')
| -rw-r--r-- | arch/arm/kernel/relocate_kernel.S | 2 |
1 files changed, 2 insertions, 0 deletions
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 |