Re: Powerpc and software single step

[Kevin Buettner <kevinb at redhat dot com>]

On Aug 12,  6:31pm, Jimi Xenidis wrote:

> The AIX kernel does not support single step but the Linux kernel does.
> 
> However, I am working with a remote machine level debugger for PowerPC
> that allows me to debug a running Linux kernel and cannot support
> single stepping.  For this I require that when debugging a Linux
> target I need to turn on SOFTWARE_SINGLE_STEP.
>  
> I would like to add this to an "obscure" setting that will turn it on
> even under Linux.
> Here is the patch.. please accept, feel free to mangle the symbol
> names to taste.

The patch looks mostly okay to me.  I do have some comments and questions
though...

1) It is customary to provide ChangeLog entries with patch submissions.

2) Why is ``ppc_linux_single_step_mode'' an extern in tm-linux.h?  I
   would really prefer that it be local to ppc-linux-tdep.c.  If
   there's some compelling reason for it to not be local, then we can
   discuss adding it to ppc-tdep.h.

3) Is a copyright assignment needed for this patch?

   [ This question is not just for Jimi, but for others reading this
   list as well.  I'm leaving Jimi's patch quoted below so that others
   can look without having to dig up the original patch submission.  ]


> diff -Naur -X ./Xdiff src/gdb/config/powerpc/tm-linux.h mygdb/gdb/config/powerpc/tm-linux.h
> --- src/gdb/config/powerpc/tm-linux.h	Thu Jun 12 19:58:07 2003
> +++ mygdb/gdb/config/powerpc/tm-linux.h	Tue Aug 12 09:05:02 2003
> @@ -33,9 +33,11 @@
>  
>  /* We can single step on linux */
>  #undef  SOFTWARE_SINGLE_STEP
> -#define SOFTWARE_SINGLE_STEP(p,q) internal_error (__FILE__, __LINE__, "Will never execute!")
> +extern void ppc_linux_software_single_step (enum target_signal, int);
> +#define SOFTWARE_SINGLE_STEP(sig,bp_p) ppc_linux_software_single_step (sig, bp_p)
>  #undef  SOFTWARE_SINGLE_STEP_P
> -#define SOFTWARE_SINGLE_STEP_P() 0
> +extern int ppc_linux_single_step_mode;
> +#define SOFTWARE_SINGLE_STEP_P() ppc_linux_single_step_mode
>  
>  /* Make sure nexti gets the help it needs for debugging assembly code
>     without symbols */
> diff -Naur -X ./Xdiff src/gdb/ppc-linux-tdep.c mygdb/gdb/ppc-linux-tdep.c
> --- src/gdb/ppc-linux-tdep.c	Tue Jun 24 19:09:22 2003
> +++ mygdb/gdb/ppc-linux-tdep.c	Tue Aug 12 09:22:11 2003
> @@ -1075,10 +1075,35 @@
>      }
>  }
>  
> +int ppc_linux_single_step_mode = 0;
> +void
> +ppc_linux_software_single_step (enum target_signal sig , int bp_p)
> +{
> +  if (ppc_linux_single_step_mode)
> +    {
> +      rs6000_software_single_step (sig, bp_p);
> +    }
> +  else
> +    {
> +      internal_error (__FILE__, __LINE__, "Will never execute!");
> +    }
> +}
> +
>  void
>  _initialize_ppc_linux_tdep (void)
>  {
>    gdbarch_register_osabi (bfd_arch_powerpc, 0, GDB_OSABI_LINUX,
>  			  ppc_linux_init_abi);
>    add_core_fns (&ppc_linux_regset_core_fns);
> +
> +  add_show_from_set (add_set_cmd("single-step-mode", class_obscure,
> +				 var_integer,
> +				 &ppc_linux_single_step_mode, "\
> +Set single step mode for PowerPCtarget:\n\
> +  0 = Target supports single stepping (i.e. Linux)\n\
> +  1 = Target does not support single stepping (i.e. AIX, Simulators).",
> +				 &setlist),
> +		     &showlist);
>  }
> +
> +