Re: [PATCH] RISC-V: enable have_nonsteppable_watchpoint by default

[Joel Brobecker <brobecker at adacore dot com>]

Hi Craig, hi Andrew,

> ---
> 
> The RISC-V debug spec 0.13 recommends that write triggers fire before the
> write is committed. If the target follows this behaviour, then
> have_nonsteppable_watchpoint needs to be set to 'on' so that GDB will step
> over the watchpoint before checking if the value has changed.
> 
> This patch adds a setshow for have_nonsteppable_watchpoint which defaults
> to 'on' to match the recommended behaviour. If a target does not follow
> this timing, then 'set riscv have_nonsteppable_watchpoint off' will need
> to be issued on the command line.
> 
> gdb/ChangeLog:
> 
> 	* riscv-tdep.c (set_have_nonsteppable_watchpoint): Add callback
> 	for 'set riscv have_nonsteppable_watchpoint'.
> 	(show_have_nonsteppable_watchpoint): Add callback for
> 	'show riscv have_nonsteppable_watchpoint'.
> 	(riscv_gdbarch_init): Initialise gdbarch setting for
> 	have_nonesteppable_watchpoint.

I assume this patch is waiting for review from Andrew?

I took a look, since I am interested in it as well. Here are my
comments.

You forgot to document the introduction of riscv_have_nonsteppable_watchpoint
in your ChangeLog above; eg:

        * riscv-tdep.c (riscv_have_nonsteppable_watchpoint): New static
        global.

You also forgot to document that you're adding new subcommands.

The rest looks good to me.

> ---
> 
> diff --git a/gdb/riscv-tdep.c b/gdb/riscv-tdep.c
> index 254914c..857c5d1 100644
> --- a/gdb/riscv-tdep.c
> +++ b/gdb/riscv-tdep.c
> @@ -226,6 +226,36 @@ show_use_compressed_breakpoints (struct ui_file *file, int from_tty,
>  		      "to %s%s.\n"), value, additional_info);
>  }
>  
> +/* Controls whether the debugger should step over hardware watchpoints before
> +   checking if the watched variable has changed.  If true, then the debugger
> +   will step over the watchpoint.  */
> +
> +static int riscv_have_nonsteppable_watchpoint = 1;
> +
> +/* The set callback for 'set riscv have-nonsteppable-watchpoint'.  */
> +
> +static void
> +set_have_nonsteppable_watchpoint (const char *args, int from_tty,
> +				  struct cmd_list_element *c)
> +{
> +  struct gdbarch *gdbarch = target_gdbarch ();
> +
> +  set_gdbarch_have_nonsteppable_watchpoint (gdbarch,
> +					    riscv_have_nonsteppable_watchpoint);
> +}
> +
> +/* The show callback for 'show riscv have-nonsteppable-watchpoint'.  */
> +
> +static void
> +show_have_nonsteppable_watchpoint (struct ui_file *file, int from_tty,
> +				   struct cmd_list_element *c,
> +				   const char *value)
> +{
> +  fprintf_filtered (file,
> +		    _("Debugger must step over hardware watchpoints is set to "
> +		      "%s.\n"), value);
> +}
> +
>  /* The set and show lists for 'set riscv' and 'show riscv' prefixes.  */
>  
>  static struct cmd_list_element *setriscvcmdlist = NULL;
> @@ -2736,6 +2766,8 @@ riscv_gdbarch_init (struct gdbarch_info info,
>    set_gdbarch_return_value (gdbarch, riscv_return_value);
>    set_gdbarch_breakpoint_kind_from_pc (gdbarch, riscv_breakpoint_kind_from_pc);
>    set_gdbarch_sw_breakpoint_from_kind (gdbarch, riscv_sw_breakpoint_from_kind);
> +  set_gdbarch_have_nonsteppable_watchpoint (gdbarch,
> +					    riscv_have_nonsteppable_watchpoint);
>  
>    /* Register architecture.  */
>    set_gdbarch_num_regs (gdbarch, RISCV_LAST_REGNUM + 1);
> @@ -2980,4 +3012,20 @@ can be used."),
>  				show_use_compressed_breakpoints,
>  				&setriscvcmdlist,
>  				&showriscvcmdlist);
> +
> +  add_setshow_boolean_cmd ("have-nonsteppable-watchpoint", no_class,
> +			   &riscv_have_nonsteppable_watchpoint,
> +			   _("\
> +Set whether debugger must step over hardware watchpoints"),
> +			   _("\
> +Show whether debugger must step over hardware watchpoints"),
> +			   _("\
> +The RISC-V debug spec recommends that hardware write watchpoints fire before\n\
> +the write is committed, in which case, GDB must step over the watchpoint\n\
> +before checking the old and new values.  Set this option to 'on' (default)\n\
> +for targets that follow this behaviour, otherwise set to 'off'."),
> +			   set_have_nonsteppable_watchpoint,
> +			   show_have_nonsteppable_watchpoint,
> +			   &setriscvcmdlist,
> +			   &showriscvcmdlist);
>  }
> 

-- 
Joel