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

Luis Machado via Gdb-patches
2022-11-21T14:05:44Z

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.