Re: [PATCH 0/9] Add new command to print the shadow stack backtrace

[Thiago Jung Bauermann <thiago.bauermann@linaro.org>]

Hello Christina,

"Schimpe, Christina" <christina.schimpe@intel.com> writes:

> Hi Thiago,
>
> apologies for the delayed feedback. Please find my comments below.

Sorry for the even longer delay.

I said I'd provide my comments this week, but things didn't go exactly
as I planned and I will be out tomorrow so for now I will send what I
have — which isn't much.

I'll send additional comments next week. Especially regarding patch 6
where there are some open questions and comments. I'm still thinking
through them and experimenting.

>> -----Original Message-----
>> From: Thiago Jung Bauermann <thiago.bauermann@linaro.org>
>> Sent: Freitag, 31. Oktober 2025 01:47
>> To: Schimpe, Christina <christina.schimpe@intel.com>
>> Cc: 'gdb-patches@sourceware.org' <gdb-patches@sourceware.org>
>> Subject: Re: [PATCH 0/9] Add new command to print the shadow stack
>> backtrace
>> 
>> "Schimpe, Christina" <christina.schimpe@intel.com> writes:
>> 
>> > Also I should probably add proper error messages when the
>> > configuration of ssp_regnum is missing,
>> 
>> Is that possible? How would GDB distinguish between missing ssp regnum
>> configuration versus the target not supporting shadow stacks?
>
> I would add it to the error message that already exists for the absence of the hook
> gdbarch_address_in_shadow_stack_memory_range:
>
> --- a/gdb/shadow-stack.c
> +++ b/gdb/shadow-stack.c
> @@ -537,7 +537,8 @@ backtrace_shadow_command (const shadow_stack_print_options &print_options,
>      error (_("No shadow stack."));
>  
>    gdbarch *gdbarch = get_current_arch ();
> -  if (!gdbarch_address_in_shadow_stack_memory_range_p (gdbarch))
> +  if (!gdbarch_address_in_shadow_stack_memory_range_p (gdbarch)
> +      || gdbarch_ssp_regnum (gdbarch) == -1)
>      error (_("Printing of the shadow stack backtrace is not supported for"
>              " the current target."))
>
> So the error message could mean both, either missing ssp regnum or the target
> not supporting shadow stack. Later in that function we check if the shadow stack
> is enabled for the current target.
>
> Does that sound ok?

Ah, I thought you wanted to have different error messages for each
case. Yes, this looks good to me.

-- 
Thiago