Re: [PATCH v2 2/4] gdb/arm: Ensure that stack pointers are in sync

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

On 11/18/22 15:52, Torbjörn SVENSSON wrote:
> Without this patch, sp might be secure, but msp or psp is non-secure
> (this state can not happen in the hardware).

Maybe expand to make it clear we're patching things so we correctly sync msp/psp to the active sp.

> 
> Signed-off-by: Torbjörn SVENSSON <torbjorn.svensson@foss.st.com>
> ---
>   gdb/arm-tdep.c | 86 ++++++++++++++++++++++++++++++++++----------------
>   1 file changed, 58 insertions(+), 28 deletions(-)
> 
> diff --git a/gdb/arm-tdep.c b/gdb/arm-tdep.c
> index 124a94dc87d..c011b2aa973 100644
> --- a/gdb/arm-tdep.c
> +++ b/gdb/arm-tdep.c
> @@ -324,20 +324,6 @@ reconstruct_t_bit(struct gdbarch *gdbarch, CORE_ADDR lr, ULONGEST psr)
>     return psr;
>   }
>   
> -/* Initialize stack pointers, and flag the active one.  */
> -
> -static inline void
> -arm_cache_init_sp (int regnum, CORE_ADDR* member,
> -				      struct arm_prologue_cache *cache,
> -				      frame_info_ptr frame)
> -{
> -  CORE_ADDR val = get_frame_register_unsigned (frame, regnum);
> -  if (val == cache->sp)
> -    cache->active_sp_regnum = regnum;
> -
> -  *member = val;
> -}
> -
>   /* Initialize CACHE fields for which zero is not adequate (CACHE is
>      expected to have been ZALLOC'ed before calling this function).  */
>   
> @@ -362,34 +348,78 @@ arm_cache_init (struct arm_prologue_cache *cache, frame_info_ptr frame)
>   
>     if (tdep->have_sec_ext)
>       {
> -      CORE_ADDR msp_val = get_frame_register_unsigned (frame, tdep->m_profile_msp_regnum);
> -      CORE_ADDR psp_val = get_frame_register_unsigned (frame, tdep->m_profile_psp_regnum);
> -
> -      arm_cache_init_sp (tdep->m_profile_msp_s_regnum, &cache->msp_s, cache, frame);
> -      arm_cache_init_sp (tdep->m_profile_psp_s_regnum, &cache->psp_s, cache, frame);
> -      arm_cache_init_sp (tdep->m_profile_msp_ns_regnum, &cache->msp_ns, cache, frame);
> -      arm_cache_init_sp (tdep->m_profile_psp_ns_regnum, &cache->psp_ns, cache, frame);
> -
> +      const CORE_ADDR msp_val
> +	= get_frame_register_unsigned (frame, tdep->m_profile_msp_regnum);
> +      const CORE_ADDR psp_val
> +	= get_frame_register_unsigned (frame, tdep->m_profile_psp_regnum);
> +
> +      cache->msp_s
> +	= get_frame_register_unsigned (frame, tdep->m_profile_msp_s_regnum);
> +      cache->msp_ns
> +	= get_frame_register_unsigned (frame, tdep->m_profile_msp_ns_regnum);
> +      cache->psp_s
> +	= get_frame_register_unsigned (frame, tdep->m_profile_psp_s_regnum);
> +      cache->psp_ns
> +	= get_frame_register_unsigned (frame, tdep->m_profile_psp_ns_regnum);
> +
> +      /* Identify what msp is alias for (msp_s or msp_ns).  */
>         if (msp_val == cache->msp_s)
>   	cache->active_msp_regnum = tdep->m_profile_msp_s_regnum;
>         else if (msp_val == cache->msp_ns)
>   	cache->active_msp_regnum = tdep->m_profile_msp_ns_regnum;
> +      else
> +	{
> +	  warning (_("Invalid state, unable to determine msp alias."));
> +	  cache->active_msp_regnum = tdep->m_profile_msp_s_regnum;

It seems we're assuming msp is msp_s, so it would be nice to put that in the warning as well.

warning (_("Invalid state, unable to determine msp alias, assuming msp_s."));

> +	}
> +
> +      /* Identify what psp is alias for (psp_s or psp_ns).  */
>         if (psp_val == cache->psp_s)
>   	cache->active_psp_regnum = tdep->m_profile_psp_s_regnum;
>         else if (psp_val == cache->psp_ns)
>   	cache->active_psp_regnum = tdep->m_profile_psp_ns_regnum;
> +      else
> +	{
> +	  warning (_("Invalid state, unable to determine psp alias."));
> +	  cache->active_psp_regnum = tdep->m_profile_psp_s_regnum;
> +	}
>   
> -      /* Use MSP_S as default stack pointer.  */
> -      if (cache->active_sp_regnum == ARM_SP_REGNUM)
> -	  cache->active_sp_regnum = tdep->m_profile_msp_s_regnum;
> +      /* Identify what sp is alias for (msp_s, msp_ns, psp_s or psp_ns).  */
> +      if (msp_val == cache->sp)
> +	cache->active_sp_regnum = cache->active_msp_regnum;
> +      else if (psp_val == cache->sp)
> +	cache->active_sp_regnum = cache->active_psp_regnum;
> +      else
> +	{
> +	  warning (_("Invalid state, unable to determine sp alias."));
> +	  cache->active_sp_regnum = cache->active_msp_regnum;
> +	}

Same here. "assuming msp".

>       }
>     else if (tdep->is_m)
>       {
> -      arm_cache_init_sp (tdep->m_profile_msp_regnum, &cache->msp_s, cache, frame);
> -      arm_cache_init_sp (tdep->m_profile_psp_regnum, &cache->psp_s, cache, frame);
> +      cache->msp_s
> +	= get_frame_register_unsigned (frame, tdep->m_profile_msp_s_regnum);
> +      cache->psp_s
> +	= get_frame_register_unsigned (frame, tdep->m_profile_psp_s_regnum);
> +
> +      /* Identify what sp is alias for (msp or psp).  */
> +      if (cache->msp_s == cache->sp)
> +	cache->active_sp_regnum = tdep->m_profile_msp_regnum;
> +      else if (cache->psp_s == cache->sp)
> +	cache->active_sp_regnum = tdep->m_profile_psp_regnum;
> +      else
> +	{
> +	  warning (_("Invalid state, unable to determine sp alias."));
> +	  cache->active_sp_regnum = tdep->m_profile_msp_regnum;

Same here.

> +	}
>       }
>     else
> -    arm_cache_init_sp (ARM_SP_REGNUM, &cache->msp_s, cache, frame);
> +    {
> +      cache->msp_s
> +	= get_frame_register_unsigned (frame, ARM_SP_REGNUM);
> +
> +      cache->active_sp_regnum = ARM_SP_REGNUM;
> +    }
>   }
>   
>   /* Return the requested stack pointer value (in REGNUM), taking into

Otherwise this looks OK to me.