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

From: Weihaw CHUANG <wchuang_at_cs.ucsd.edu>
Date: 2001-05-04 16:51:26
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

I'm still very unsure if my intuition is correct, hence the
questions.  I only figured out the below through trial and error

Anyways the solution appears to be (again correct me if anything is brain 

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),

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 
       0        1          2

Received on Thu May 03 23:51:29 2001

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