On 07/02/2015 06:49 PM, Gilles Chanteperdrix wrote:
> On Thu, Jul 02, 2015 at 06:44:06PM +0200, Jan Kiszka wrote:
>> On 2015-07-02 18:30, Philippe Gerum wrote:
>>> On 07/02/2015 05:39 PM, Jan Kiszka wrote:
>>>> On 2015-07-02 17:24, Philippe Gerum wrote:
>>>>> On 07/02/2015 05:20 PM, git repository hosting wrote:
>>>>>> Module: xenomai-jki
>>>>>> Branch: for-forge
>>>>>> Commit: 99736c29a21a5e5536f8db9e580fd11cdb0eb0f2
>>>>>> URL:    
>>>>>> http://git.xenomai.org/?p=xenomai-jki.git;a=commit;h=99736c29a21a5e5536f8db9e580fd11cdb0eb0f2
>>>>>>
>>>>>> Author: Jan Kiszka <[email protected]>
>>>>>> Date:   Thu Jul  2 17:12:39 2015 +0200
>>>>>>
>>>>>> cobalt/kernel: Remove unused mode parameter from COBALT_SYSCALL
>>>>>
>>>>> We want to keep this. At some point, maybe, we will be able to use this
>>>>> information to instrument the code with calling context guards, or as
>>>>> the source of the mode data in the syscall table. Today, it's at least
>>>>> useful inline documentation, without having to browse the table.
>>>>
>>>> This only makes sense when cobalt_sysmodes can be generated from it.
>>>> Currently it isn't, and I bet there are already plenty of
>>>> inconsistencies, minimizing the value captured via COBALT_SYSCALL
>>>> massively. So we should either get rid of cobalt_sysmodes or of that
>>>> parameter.
>>>>
>>>
>>> "currently" is the point. If you feel implementing either aspects, i.e.
>>> automatic tagging of the current context when traversing a cobalt call
>>> based on the mode in the syscall macro, or generating the table data
>>> based on the info, please do. If you feel fixing any consistency between
>>> the two mode specs proving your bet right, please do as well. But for
>>> now, I won't pick that commit.
>>
>> The approach of using COBALT_SYSCALL to define the mode only works if
>> that is also the only place to define it. Let's see first if/how that
>> can be achieved.
> 
> That can be achieved by getting the macro to adding data in a
> special section, then use that section as the syscall table with
> linker generate symbols. A lot of stuff works like this, like the
> init table, or glibc constructors, so, this can definitely be
> achieved. This probably requires the I-pipe patch to modify the
> kernel linker script, of which there are several instances (one
> instance by arch maybe).
> 

Yes. Having to fixup the linker script was the reason not to implement
this immediately, as there could be some backward compat issues to
address with legacy pipelines running a most recent 3x cobalt core.

-- 
Philippe.

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