Re: [PATCH 0/2] jump label: update for .39

[David Daney <ddaney@caviumnetworks.com>]

On 03/10/2011 03:16 PM, Steven Rostedt wrote:
> On Thu, 2011-03-10 at 17:48 -0500, Mathieu Desnoyers wrote:
>> * Steven Rostedt (rostedt@goodmis.org) wrote:
>>> On Thu, 2011-03-10 at 16:22 -0500, Mathieu Desnoyers wrote:
>>>
>>>>> Anyway, I think the best thing for now is to have Jason add
>>>>> the .align(sizeof(long)) in the inline assembly for all locations and be
>>>>> done with it.
>>>>
>>>> You seem to be contradicting yourself here. I'm concerned about having
>>>> "structures" of a size not power of two. Can we simply either
>>>
>>> But we don't have structures. We have data that has been allocated in
>>> assembly. Come to think of it, it may be best to keep these as
>>> ".align 4".
>>
>> The .align 4 is certainly not the right answer, because it will trigger
>> unaligned accesses on some 64-bit architectures, as we have faced with
>> trace event.
>
> Will it? Seems that sparc does this regardless.
>
> Remember, this is 3 natural word sized objects, and vmlinux.ld starts
> the section off with .ALIGN 8, hence, the section is already 8 byte
> aligned, all objects within this section are 8 bytes (for 64bit archs,
> and 4 bytes for 32bit), why would saying ".align 4" cause the linker to
> add holes to make it 4 byte aligned when it is already 8 byte aligned.
> The ".align 4" should work with both 32bit and 64bit archs.
>

It should work, but it hurts my eyes to see the source code forcing a 
64-bit word to 32-bit alignment.

David Daney