[gcc(refs/vendors/ARM/heads/morello)] libstdc++: Update personality function for purecap

[gcc(refs/vendors/ARM/heads/morello)] libstdc++: Update personality function for purecap

[Alex Coplan]

https://gcc.gnu.org/g:afaa9f2bb327ae04a22d26c5793079f7c06da1bf

commit afaa9f2bb327ae04a22d26c5793079f7c06da1bf
Author: Alex Coplan <alex.coplan@arm.com>
Date:   Sat Jun 18 11:45:33 2022 +0100

    libstdc++: Update personality function for purecap
    
    This updates the C++ personality function following the changes made to
    the libgcc C personality function for pure-capability Morello. There are
    two main changes here. The first is using
    __builtin_code_address_from_pointer to drop the LSB from Morello code
    pointers when searching through call-site tables (without this we would
    never find the right landing pad when unwinding).
    
    The second change is to reflect the change in the exception table format
    for pure-capability Morello where the landing pad is a capability
    indirected by an offset in the call-site table.
    
    We also improve on the robustness of the existing code in the C
    personality function by asserting that we only see the implemented
    capability landing pad marker value (0xd) and also handling the case
    where this is no associated landing pad with a given call-site table
    entry.
    
    This fixes many execution tests involving exception handling in the g++
    testsuite.
    
    libgcc/ChangeLog:
    
            * unwind-c.c (PERSONALITY_FUNCTION): Fix handling of case where
            call-site table entry doesn't have an associated landing pad.
    
    libstdc++-v3/ChangeLog:
    
            * libsupc++/eh_personality.cc (PERSONALITY_FUNCTION): Adapt for
            pure-capability Morello.

Diff:
---
 libgcc/unwind-c.c                        | 17 +++++++++---
 libstdc++-v3/libsupc++/eh_personality.cc | 45 +++++++++++++++++++++++++++-----
 2 files changed, 52 insertions(+), 10 deletions(-)

diff --git a/libgcc/unwind-c.c b/libgcc/unwind-c.c
index ac0085c1159..a2a5c2e92bf 100644
--- a/libgcc/unwind-c.c
+++ b/libgcc/unwind-c.c
@@ -214,10 +214,19 @@ PERSONALITY_FUNCTION (int version,
       _Unwind_Ptr marker = 0;
       /* Single uleb128 value as the capability marker.  */
       p = read_encoded_value (0, DW_EH_PE_uleb128, p, &marker);
-      /* 8 byte value indicating the offset from said 8 byte value.
-	 Could use DW_EH_PE_indirect except that the offset is zero if there is
-	 no landing pad.  */
-      p = read_encoded_value (0, DW_EH_PE_pcrel | DW_EH_PE_udata8, p, &cs_lp);
+      if (marker == 0xd)
+	{
+	  /* 8 byte value indicating the offset from said 8 byte value.
+	     Could use DW_EH_PE_indirect except that the offset is zero
+	     if there is no landing pad.  */
+	  p = read_encoded_value (0, DW_EH_PE_pcrel | DW_EH_PE_udata8, p,
+				  &cs_lp);
+	}
+      else if (marker)
+	/* Unsupported landing pad marker value.  */
+	__builtin_abort ();
+      else
+	cs_lp = 0; /* No landing pad.  */
 #  else
       p = read_encoded_value (0, info.call_site_encoding, p, &cs_lp);
 #  endif
diff --git a/libstdc++-v3/libsupc++/eh_personality.cc b/libstdc++-v3/libsupc++/eh_personality.cc
index fd7cd6fc798..25079f76725 100644
--- a/libstdc++-v3/libsupc++/eh_personality.cc
+++ b/libstdc++-v3/libsupc++/eh_personality.cc
@@ -375,7 +375,8 @@ PERSONALITY_FUNCTION (int version,
   const unsigned char *language_specific_data;
   const unsigned char *action_record;
   const unsigned char *p;
-  _Unwind_Ptr landing_pad, ip;
+  _Unwind_Ptr landing_pad, ip_ptr;
+  _Unwind_Address ip;
   int handler_switch_value;
   void* thrown_ptr = 0;
   bool foreign_exception;
@@ -422,8 +423,8 @@ PERSONALITY_FUNCTION (int version,
   // function and LSDA pointers.  The ARM implementation caches these in
   // the exception header (UCB).  To avoid rewriting everything we make a
   // virtual scratch register point at the UCB.
-  ip = (_Unwind_Ptr) ue_header;
-  _Unwind_SetGR(context, UNWIND_POINTER_REG, ip);
+  ip_ptr = (_Unwind_Ptr) ue_header;
+  _Unwind_SetGR (context, UNWIND_POINTER_REG, ip_ptr);
 #else
   __cxa_exception* xh = __get_exception_header_from_ue(ue_header);
 
@@ -454,10 +455,17 @@ PERSONALITY_FUNCTION (int version,
   p = parse_lsda_header (context, language_specific_data, &info);
   info.ttype_base = base_of_encoded_value (info.ttype_encoding, context);
 #ifdef _GLIBCXX_HAVE_GETIPINFO
-  ip = _Unwind_GetIPInfo (context, &ip_before_insn);
+  ip_ptr = _Unwind_GetIPInfo (context, &ip_before_insn);
 #else
-  ip = _Unwind_GetIP (context);
+  ip_ptr = _Unwind_GetIP (context);
 #endif
+
+#ifdef __USING_SJLJ_EXCEPTIONS__
+  ip = (_Unwind_Address) ip_ptr;
+#else
+  ip = __builtin_code_address_from_pointer ((void *)ip_ptr);
+#endif
+
   if (! ip_before_insn)
     --ip;
   landing_pad = 0;
@@ -502,7 +510,26 @@ PERSONALITY_FUNCTION (int version,
       // Note that all call-site encodings are "absolute" displacements.
       p = read_encoded_value (0, info.call_site_encoding, p, &cs_start);
       p = read_encoded_value (0, info.call_site_encoding, p, &cs_len);
+#ifdef __CHERI_PURE_CAPABILITY__
+      // Single uleb128 value as the capability marker.
+      _Unwind_Ptr marker = 0;
+      p = read_encoded_value (0, DW_EH_PE_uleb128, p, &marker);
+      if (marker == 0xd)
+	{
+	  // 8-byte offset to the (indirected) capability.
+	  p = read_encoded_value (0, DW_EH_PE_pcrel | DW_EH_PE_udata8, p,
+				  &cs_lp);
+	}
+      else if (marker)
+	{
+	  // Unsupported landing pad marker value.
+	  std::abort ();
+	}
+      else
+	cs_lp = 0; // No landing pad.
+#else
       p = read_encoded_value (0, info.call_site_encoding, p, &cs_lp);
+#endif
       p = read_uleb128 (p, &cs_action);
 
       // The table is sorted, so if we've passed the ip, stop.
@@ -511,7 +538,13 @@ PERSONALITY_FUNCTION (int version,
       else if (ip < info.Start + cs_start + cs_len)
 	{
 	  if (cs_lp)
-	    landing_pad = info.LPStart + cs_lp;
+	    {
+#ifdef __CHERI_PURE_CAPABILITY__
+	      landing_pad = *(_Unwind_Ptr *)cs_lp;
+#else
+	      landing_pad = info.LPStart + cs_lp;
+#endif
+	    }
 	  if (cs_action)
 	    action_record = info.action_table + cs_action - 1;
 	  goto found_something;