Re: [Linux-ia64] Re: location of statcked registers after exception (superceeds previous email)

[Don Dugger <n0ano@valinux.com>]

Wei-

The file `arch/ia64/kernel/ivt.S' contains the interrupt vector table.
This is where all exceptions go.

On Thu, May 03, 2001 at 11:51:26PM -0700, Weihaw CHUANG wrote:
> 
> I think I've figured out my own question.  However I still would like to
> understand some of this kernel code in 
> <linux src>/arch/ia64/kernel/entry.S
> 
> If my application takes an exception, what is the entry point in entry.S?
> I'd also like to verify that application stacked registers  will be
> stored on kernel stack during a context switch.  My understanding is that
> only the last procedure frame will be stored there.  (Is this notion
> correct?)
> 
> I'm still very unsure if my intuition is correct, hence the
> questions.  I only figured out the below through trial and error
> hacking.
> 
> Anyways the solution appears to be (again correct me if anything is brain 
> damaged):
> 
> On Thu, 3 May 2001, Weihaw CHUANG wrote:
> 
> > 
> >   int offset = cfm.sof - (regid-32)
> >   unsigned long long = ptrace(PTRACED_PEEKUSER, pid, PT_AR_BSP, 0);
> >   regvalue = ptrace(PTRACE_PEEKDATA, pid, 
> >                     (long ) ia64_rse_skip_regs((long*) bsp, offset), 0);
> > 
> 
> int offset = regid - 32;
> unsigned long long bspstore = ptrace(PTRACED_PEEKUSER, pid,
>                                     PT_AR_BSPSTORE, 0);
> unsigned long long regvalue = ptrace(PTRACE_PEEKDATA, pid,
>                      (long) ia64_rse_skip_regs((long*) bspstore, offset),
>                      0);
> 
> 
> I'd like to be pendantic, and make sure the following intuition is
> correct.  Ptrace dumps seems to agree so far.
> 
> > 
> > 
> > That is, does this diagram make sense? 
> > 
> > alloc r35 = ar.pfs, 0, 3, 0, 0
> > reg stack
> >    | r32    | r34      | r35    |   (r35 is top of reg stack)
> > negative offset from bsp is:
> >      3        2          1        bsp
> offset from 
>      ^bspstore
>        0        1          2
> 
> Thanks!!
> -Wei
> 
> 
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-- 
Don Dugger
"Censeo Toto nos in Kansa esse decisse." - D. Gale
n0ano@valinux.com
Ph: 303/938-9838