Re: [RFC PATCH 1/5] gdb/arm: Introduce control_s and control_ns registers

[Luis Machado <luis.machado@arm.com>]

Hi Tomas,

On 11/5/22 09:44, Tomas Vanek wrote:
> The M-profile security extension registers will be used for stack
> selection in FNC_RETURN and return from secure to non-secure state.
> 
> The presence of the registers is optional.
> If one or both are missing the security extension profile is accepted.
> The code using the registers must check m_profile_control_[n]?s_regnum
> for -1.
> 
> Signed-off-by: Tomas Vanek <vanekt@fbl.cz>
> ---
>   gdb/arm-tdep.c | 20 ++++++++++++++++++++
>   gdb/arm-tdep.h |  2 ++
>   2 files changed, 22 insertions(+)
> 
> diff --git a/gdb/arm-tdep.c b/gdb/arm-tdep.c
> index 3105543..564ee43 100644
> --- a/gdb/arm-tdep.c
> +++ b/gdb/arm-tdep.c
> @@ -9996,6 +9996,8 @@ enum arm_vfp_cprc_base_type
>     int m_profile_psp_ns_regnum = -1;
>     int m_profile_msp_s_regnum = -1;
>     int m_profile_psp_s_regnum = -1;
> +  int m_profile_control_s_regnum = -1;
> +  int m_profile_control_ns_regnum = -1;
>     int tls_regnum = 0;
>   
>     /* If we have an object to base this architecture on, try to determine
> @@ -10473,6 +10475,22 @@ enum arm_vfp_cprc_base_type
>   		}
>   	      m_profile_psp_s_regnum = register_count++;
>   
> +	      /* Regard the control_s and control_ns registers optional,
> +	       * accept the security extension feature even without them */
> +	      valid_p = tdesc_numbered_register (feature, tdesc_data.get (),
> +						 register_count, "control_s");

What tools are advertising control_s and control_ns? We need to document those properly if we're planning on using them
as part of decision-making in GDB.


> +	      if (!valid_p)
> +		warning (_("M-profile secext feature is missing required register control_s."));
> +	      else
> +		m_profile_control_s_regnum = register_count++;
> +
> +	      valid_p = tdesc_numbered_register (feature, tdesc_data.get (),
> +						 register_count, "control_ns");
> +	      if (!valid_p)
> +		warning (_("M-profile secext feature is missing required register control_ns."));
> +	      else
> +		m_profile_control_ns_regnum = register_count++;
> +
>   	      have_sec_ext = true;
>   	    }
>   
> @@ -10553,6 +10571,8 @@ enum arm_vfp_cprc_base_type
>         tdep->m_profile_psp_ns_regnum = m_profile_psp_ns_regnum;
>         tdep->m_profile_msp_s_regnum = m_profile_msp_s_regnum;
>         tdep->m_profile_psp_s_regnum = m_profile_psp_s_regnum;
> +      tdep->m_profile_control_s_regnum = m_profile_control_s_regnum;
> +      tdep->m_profile_control_ns_regnum = m_profile_control_ns_regnum;
>       }
>   
>     arm_register_g_packet_guesses (gdbarch);
> diff --git a/gdb/arm-tdep.h b/gdb/arm-tdep.h
> index bcd7e08..11670e9 100644
> --- a/gdb/arm-tdep.h
> +++ b/gdb/arm-tdep.h
> @@ -133,6 +133,8 @@ struct arm_gdbarch_tdep : gdbarch_tdep_base
>     int m_profile_psp_ns_regnum = ARM_SP_REGNUM;	/* M-profile PSP_NS register number.  */
>     int m_profile_msp_s_regnum = ARM_SP_REGNUM;	/* M-profile MSP_S register number.  */
>     int m_profile_psp_s_regnum = ARM_SP_REGNUM;	/* M-profile PSP_S register number.  */
> +  int m_profile_control_s_regnum = -1;		/* M-profile CONTROL_S register number.  */
> +  int m_profile_control_ns_regnum = -1;		/* M-profile CONTROL_NS register number.  */
>   
>     int tls_regnum = 0;		/* Number of the tpidruro register.  */
>