[PATCH V2 2/2] gdb/arm: Sync sp with other *sp registers

[Yvan Roux <yvan.roux@foss.st.com>]

For Arm Cortex-M33 with security extensions, there are 4 different
stack pointers (msp_s, msp_ns, psp_s, psp_ns), without security
extensions and for other Cortex-M targets, there are 2 different
stack pointers (msp and psp).

With this path, sp will always be in sync with one of the real stack
pointers on Arm targets that contains more than one stack pointer.

Signed-off-by: Torbjörn SVENSSON <torbjorn.svensson@foss.st.com>
Signed-off-by: Yvan Roux <yvan.roux@foss.st.com>
---
 gdb/arm-tdep.c | 89 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 89 insertions(+)

diff --git a/gdb/arm-tdep.c b/gdb/arm-tdep.c
index 89c2779bbb5..c28543229de 100644
--- a/gdb/arm-tdep.c
+++ b/gdb/arm-tdep.c
@@ -3812,6 +3812,85 @@ arm_dwarf2_prev_register (struct frame_info *this_frame, void **this_cache,
       return frame_unwind_got_constant (this_frame, regnum, cpsr);
 
     default:
+      /* Handle the alternative SP on Cortex-M.  */
+      if (arm_is_alternative_sp_register (tdep, regnum))
+	{
+	  bool override_with_sp_value = false;
+	  CORE_ADDR val;
+
+	  if (tdep->have_sec_ext)
+	    {
+	      CORE_ADDR sp
+		= get_frame_register_unsigned (this_frame, ARM_SP_REGNUM);
+	      CORE_ADDR msp_s
+		= get_frame_register_unsigned (this_frame,
+					       tdep->m_profile_msp_s_regnum);
+	      CORE_ADDR msp_ns
+		= get_frame_register_unsigned (this_frame,
+					       tdep->m_profile_msp_ns_regnum);
+	      CORE_ADDR psp_s
+		= get_frame_register_unsigned (this_frame,
+					       tdep->m_profile_psp_s_regnum);
+	      CORE_ADDR psp_ns
+		= get_frame_register_unsigned (this_frame,
+					       tdep->m_profile_psp_ns_regnum);
+
+	      if (regnum == tdep->m_profile_msp_regnum
+		  && (msp_s == sp || msp_ns == sp))
+		/* Use value of SP for MSP register.  */
+		override_with_sp_value = true;
+	      else if (regnum == tdep->m_profile_msp_s_regnum && msp_s == sp)
+		/* Use value of SP for MSP_S register.  */
+		override_with_sp_value = true;
+	      else if (regnum == tdep->m_profile_msp_ns_regnum && msp_ns == sp)
+		/* Use value of SP for MSP_NS register.  */
+		override_with_sp_value = true;
+	      else if (regnum == tdep->m_profile_psp_regnum
+		       && (psp_s == sp || psp_ns == sp))
+		/* Use value of SP for PSP register.  */
+		override_with_sp_value = true;
+	      else if (regnum == tdep->m_profile_psp_s_regnum && psp_s == sp)
+		/* Use value of SP for PSP_S register.  */
+		override_with_sp_value = true;
+	      else if (regnum == tdep->m_profile_psp_ns_regnum && psp_ns == sp)
+		/* Use value of SP for PSP_NS register.  */
+		override_with_sp_value = true;
+	    }
+	  else if (tdep->is_m)
+	    {
+	      CORE_ADDR sp
+		= get_frame_register_unsigned (this_frame, ARM_SP_REGNUM);
+	      CORE_ADDR msp
+		= get_frame_register_unsigned (this_frame,
+					       tdep->m_profile_msp_regnum);
+	      CORE_ADDR psp
+		= get_frame_register_unsigned (this_frame,
+					       tdep->m_profile_psp_regnum);
+
+	      if (regnum == tdep->m_profile_msp_regnum && sp == msp)
+		/* Use value of SP for MSP register.  */
+		override_with_sp_value = true;
+	      else if (regnum == tdep->m_profile_psp_regnum && sp == psp)
+		/* Use value of SP for PSP register.  */
+		override_with_sp_value = true;
+	    }
+
+	  if (override_with_sp_value)
+	    {
+	      /* Use value of SP from previous frame.  */
+	      struct frame_info *prev_frame = get_prev_frame(this_frame);
+	      if (prev_frame)
+		val = get_frame_register_unsigned (prev_frame, ARM_SP_REGNUM);
+	      else
+		val = get_frame_base(this_frame);
+	    }
+	  else
+	    /* Use value for the register from previous frame.  */
+	    val = get_frame_register_unsigned (this_frame, regnum);
+
+	  return frame_unwind_got_constant(this_frame, regnum, val);
+	}
+
       internal_error (__FILE__, __LINE__,
 		      _("Unexpected register %d"), regnum);
     }
@@ -4931,6 +5010,8 @@ arm_dwarf2_frame_init_reg (struct gdbarch *gdbarch, int regnum,
 			   struct dwarf2_frame_state_reg *reg,
 			   struct frame_info *this_frame)
 {
+  arm_gdbarch_tdep *tdep = (arm_gdbarch_tdep *) gdbarch_tdep (gdbarch);
+
   if (is_pacbti_pseudo (gdbarch, regnum))
     {
       /* Initialize RA_AUTH_CODE to zero.  */
@@ -4950,6 +5031,14 @@ arm_dwarf2_frame_init_reg (struct gdbarch *gdbarch, int regnum,
     case ARM_SP_REGNUM:
       reg->how = DWARF2_FRAME_REG_CFA;
       break;
+    default:
+      /* Handle the alternative SP on Cortex-M.  */
+      if (arm_is_alternative_sp_register (tdep, regnum))
+	{
+	  reg->how = DWARF2_FRAME_REG_FN;
+	  reg->loc.fn = arm_dwarf2_prev_register;
+	}
+      break;
     }
 }
 
-- 
2.17.1