Re: kgdb support for gdb

[Andrew Cagney <cagney@gnu.org>]

> Index: src/gdb/stack.c
> ===================================================================
> --- src.orig/gdb/stack.c	2004-08-03 06:27:26.000000000 +0530
> +++ src/gdb/stack.c	2004-10-01 12:59:38.000000000 +0530
> @@ -45,6 +45,7 @@
>  #include "dictionary.h"
>  #include "reggroups.h"
>  #include "regcache.h"
> +#include "objfiles.h"

See Mark's general comments - I agree, the support should be there on 
all GNU/Linux systems, and not require special customization.

As for details of the lk files, I'll leave that to GNU/Linux patch revierws.

However, for the frame stuff, I've noticed the below.  Yes it's long. 
But mostly mechanical:

- "gdb doesn't lie"
This means that if the stack contains a context frame then the context 
frame is included in the backtrace.  Adding a feature to supresses 
certain frames in a back-trace would be interesting but, I think, should 
be added separatly (and needs to be user configurable).

- __sched_text_start
stack.c should definitly not be directly testing that.  Instead ...

- frame attributes
... the code should start testing for frame attributes: is this a callee 
frame; ......

- <context switch>
A things-to-do-today task is modify the stack/frame/... code so that it 
displays something like:
	stopped at <signal trampoline>+0x23
(i.e, the offset into the signal trampoline is displayed - at present it 
isn't) are you interested in trying to [separatly] fix this?

- dissassemble
I'm curious, does disassemble work for these context frames?  It 
currently doesn't for signal trampolines.

- PC_REGNUM and SP_REGNUM
I noticed code refering to these - they are definitly on their way out - 
you'll need to find another way of implementing that.  I'm also 
wondering about the lm-tdep code that computes the frame ID, the code 
addr should be the start of that code block and not the current PC - a 
frame ID's code and stack addresses are both constant through out the 
lifetime of a frame.

- testing
As with signal trampolines, we'll need to ensure that this is tested. 
It should be possible to construct testsuite additions that show GDB 
backtracing at least through one of these frames (Past experience has 
taught us that untested code unfortunatly and consistently bitrots).  I 
think it's possible to construct something without requiring a kernel.

- coding http://www.gnu.org/prep/standards_toc.html
One querk to check is GDB's comment style.

I think we can wack these out relatively quickly.

Andrew

>  /* Prototypes for exported functions. */
>  
> @@ -420,9 +421,14 @@
>    struct symtab_and_line sal;
>    int source_print;
>    int location_print;
> +  CORE_ADDR pc;
> +  struct frame_id fid;
> +  struct minimal_symbol *schedbegin;
> +  struct minimal_symbol *schedend;
>  
>    if (get_frame_type (fi) == DUMMY_FRAME
> -      || get_frame_type (fi) == SIGTRAMP_FRAME)
> +      || get_frame_type (fi) == SIGTRAMP_FRAME
> +      || (get_frame_type (fi) == CONTEXT_FRAME && print_level != 0))
>      {
>        struct cleanup *uiout_cleanup
>  	= make_cleanup_ui_out_tuple_begin_end (uiout, "frame");
> @@ -455,12 +461,38 @@
>  	  annotate_signal_handler_caller ();
>            ui_out_field_string (uiout, "func", "<signal handler called>");
>          }
> +      else if (get_frame_type (fi) == CONTEXT_FRAME)
> +        {
> +	  annotate_context_entry ();
> +          ui_out_field_string (uiout, "func", "<context switch>");
> +        }
>        ui_out_text (uiout, "\n");
>        annotate_frame_end ();
>  
>        do_cleanups (uiout_cleanup);
>        return;
>      }
> +  /* Don't print context switch and scheduler frames if we are at level 0. */
> +  if (get_frame_type (fi) == CONTEXT_FRAME)
> +    {
> +      schedbegin = lookup_minimal_symbol("__sched_text_start", NULL,
> +					 symfile_objfile);
> +      schedend = lookup_minimal_symbol("__sched_text_end", NULL,
> +				       symfile_objfile);
> +      if (schedbegin && schedend)
> +	while ((fi = get_prev_frame(fi)) != NULL)
> +	  {
> +	    fid = get_frame_id(fi);
> +	    pc = 0;
> +	    if (!fid.code_addr_p)
> +	      break;
> +	    pc = get_frame_id(fi).code_addr; 
> +	    if (SYMBOL_VALUE_ADDRESS(schedbegin) >= pc)
> +	      break;
> +	    if (SYMBOL_VALUE_ADDRESS(schedend) <= pc)
> +	      break;
> +	  }
> +    }
>  
>    /* If fi is not the innermost frame, that normally means that fi->pc
>       points to *after* the call instruction, and we want to get the