Help in figuring out score objects in RTEMS and ticket #3131

[Utkarsh Rai]

With the help of Dr.Gedare and a bit of digging, I was able to understand
the file system design concept in RTEMS. This is what I was able to gather-

 > The object-oriented design of the file system refers to the fact that
the virtual file-system layer provides a framework upon which different
filesystems can be built.

> For example, the file_sytems_operations_table defines the various
operations required by a file system(mount, unmount, path evaluation), the
rtems_filesystem_file_handlers_r table defines the various functions(open,
write, read, etc.) that act on a node in a file-system also this is where
the mmap_h handler is defined.

>The file system defines its implementation of the above operations and
registers it in the corresponding table, whenever a system call is made,
the registered handler is invoked and changes to the file are done.

So my question is,  do we have to define the mmap_h in the IMFS file system
layer(as I could not find an implementation for this handler) and then
register it in the file_handlers table and then use this in mmap? Or do we
already have a generic mmap_h implementation that I can use?


On Thu, Jun 11, 2020 at 6:04 AM Utkarsh Rai <utkarsh.rai60 at gmail.com> wrote:

> Hello,
> For my GSoC project, user-configurable thread stack protection, I need to
> track, allocate, and manipulate attributes of shared as well as protected
> stacks. Dr.Gedare suggested that tracking them with score objects would be
> a good idea. He also indicated a good place to start and understand
> score objects would be through this ticket.
> <https://devel.rtems.org/ticket/3131>
>
> From the information that I could find in docs, my understanding of score
> objects is that they are a type of directive that
> helps introduce modularity to RTEMS as various types of RTEMS objects like
> message queues, semaphores, etc. can use the same set of directives for
> allocation/deallocation and control of their object types.
>
> Some of the examples of the implementation that I could find used
> _Object_Iniitialize_information()
> to initialize the object type, then _Object_Allocate()/Free()
> allocate/de-allocate the object. Object_Id is used to control the object
> type. My confusion is, how do we use object IDs to refer to and control the
> allocated objects?
>
> I also have some confusion in the above-mentioned ticket, it says-
> 'The mmap_h handler should construct a mapping object. A destructor is
> currently missing. Maybe the mmap_h handler should use a flag to deal with
> construction and destruction.'
>  I am unclear as to how the mmap_h handler should precisely look like and
> where should it be defined?
> I would be grateful if you can provide some help in figuring this out.
>
> Regards,
> Utkarsh
>
>
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