[PATCH v1 2/7] arm64: introduce interfaces to hotpatch kernel and module code

[Sandeepa Prabhu]

On 25 September 2013 20:46, Steven Rostedt <rostedt at goodmis.org> wrote:
> On Wed, 25 Sep 2013 20:12:17 +0530
> Sandeepa Prabhu <sandeepa.prabhu at linaro.org> wrote:
>
>
>> > On aarch64, are instructions always word aligned? If not, it should be
>> > safe for stop machine to modify non word aligned instructions, but this
>> > patch looks like it doesn't allow stop_machine() to do so.
>> Steve,
>>
>> Yes, aarch64 instructions must be word-aligned, else instruction fetch
>> would generate Misaligned PC fault.
>>
>
> Thanks for clarifying, as IIUC, there's ARM architectures that allow
> for 2 and 4 byte instructions.
Yes, ARM 32-bit mode would support both 32-bit and 16-bit alignment
based on ARM or Thumb mode, whereas
AArch64 (in arch/arm64/) is always 32-bit instructions and PC need to
be aligned to 32-bit address.

Thanks,
Sandeepa
>
> -- Steve