Re: [rtl] runtime image of module

["Norm Dresner" <ndrez@att.net>]

Every real-time module -- in fact every kernel module,
real-time or normal -- is a .o file created by a
"partial-link" of the constituent individual files.  The
format of a .o file is AFAIK well documented and you can
discover a lot by using the program objdump to determine
what the headers and body of the files contain and matching
that to a hex-dump of the file.

    Norm


----- Original Message -----
From: A V <anumula_rtl@yahoo.com>
To: <rtl@fsmlabs.com>
Sent: Tuesday, November 06, 2001 4:03 PM
Subject: Re: [rtl] runtime image of module


>
> Hi,
>
>      Thanks for your replies.
> First let me tell what i am doing.
>     As part of my thesis i am developing debugger for
> realtime tasks. It should run in Real-time Kernel and
> access the module of user interest and give
> information of that module.
>
>     Regarding Kernel knowledge i have just studied
> Memory management of Linux and some scheduling related
> things. And i have idea of ELF format. To get
> practical knowledge about ELF format i wrote some
> simple programs to display various sections of an
> executable file.
> I know how run-time memory image of an executable is
> formed.
>
>      Now my problems are :
> As Kernel modules are different from executable files
> i need to know how its memory image will be. And one
> more doubt is...
>    I can get address of a module using query_module
> system call. And i know that first 52 bytes of memory
> image will be ELF header. So can i directly read 52
> bytes beginning at that address ?
>
> Once again thanks for nice replies.
> Venkat
>
>
> --- Norm Dresner <ndrez@att.net> wrote:
> > Before anyone even begins to think about answering
> > the
> > question, we'd need to know why you want this
> > information
> > and how much you already understand about the
> > kernel's
> > internal architecture so the answer can be tailored
> > appropriately.
> >
> >     Norm
> >
> > ----- Original Message -----
> > From: Calin A. Culianu <calin@ajvar.org>
> > To: <rtl@fsmlabs.com>
> > Sent: Monday, November 05, 2001 11:29 AM
> > Subject: Re: [rtl] runtime image of module
> >
> >
> > > On Sun, 4 Nov 2001, A V wrote:
> > > >
> > > > Hi all,
> > > >
> > > >   I want to know how the runtime image of a will
> > > > be.i.e where the stack will be and bss . Can
> > somebody
> > > > help me.
> > >
> > > All modules run in kernel space. This means that
> > the
> > address space of a
> > > running module is the same logical address space
> > that the
> > kernel itself
> > > uses -- this is because a module IS the kernel.
> > Memory
> > for modules is
> > > cleanly allocated during the module's creation and
> > cleanly free'd during
> > > the module's destruction. (with the exception for
> > memory
> > the module itself
> > > explicitly allocates using kmalloc).
> > >
> > > As far as stacks go: Well, that depends... you may
> > have
> > several stacks if
> > > you go and create yourself several threads inside
> > your
> > module.  The other
> > > data and code segments and such all get allocated
> > by the
> > kernel in kernel
> > > space via kmalloc probably during the
> > create_module()
> > system call. For
> > > more info, module.c in the kernel/ subtree of the
> > linux
> > source tree can
> > > answer many of your questions... :)
> > >
> > > As for where exactly stacks come from in the linux
> > kernel
> > when tasks run
> > > on behalf of users or during bottom-halves of
> > drivers:
> > that's a good
> > > question. I would imagine that actually there are
> > fewer
> > kernel stacks than
> > > there are kernel tasks.  Most of the time tasks
> > spend
> > their time running
> > > in user mode, where they get their own user
> > stacks.. as
> > for when they run
> > > in kernel mode during system calls, they probably
> > get
> > these temporary
> > > stacks that go away completely as soon as the
> > system call
> > returns to user
> > > mode.
> > >
> > > I kind of wish I knew more about the kernel and
> > the
> > relationship between
> > > different threads of execution and dedicated
> > kernel
> > tasks.... Oh well..
> > > maybe someone else can shed more light on this
> > matter...
> > >
> > > -Calin
> > >
> > >
> > >
> > >
> > > >
> > > > Regards
> > > > Venkat
> >
> >
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> >
>
>
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