Change to allow signal handlers to set SE and BE bits.

[Corey Minyard]

Here's an example patch (that I have tested) that shows the use of the
top 16 bits of the trap field as communication between the signal
handler and the kernel.

-Corey

Corey Minyard wrote:

>
> Actually, using the SE bit may not be the best way to handle this to
> cover all the PPC variants.
>
> Would it be better to have a special bit field someplace that is used to
> communicate between the signal handler and the kernel?  Some
> possibilities are:
>
>    * The top 16 bits of the trap field
>    * The currently unused mq field (except on APUS?)
>    * A new field in the signal frame
>
> I'm thinking that reserving the top 16 bits of the trap field may be the
> best.  It would always come in as zero (so existing software won't be
> broken) and it will be available for all processors and will not be used
> for anything else by the processor.
>
> Any thoughts?
>
> -Corey
>
> Matt Porter wrote:
>
>> On Fri, Aug 29, 2003 at 03:00:51PM -0500, Corey Minyard wrote:
>>
>>
>>> I have a debugger that runs in an application that requires access to
>>> the SE and BE bits.  The following patch adds that capability to
>>> 2.4.21-ben1.  I have tested this, and gdb still seems to correctly step
>>> out of signal handlers, and it seems to work for 4xx.  Does this
>>> look ok?
>>>
>>>
>>

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