[gcc(refs/vendors/ARM/heads/morello)] libgcc type handling.

[gcc(refs/vendors/ARM/heads/morello)] libgcc type handling.

[Matthew Malcomson]

https://gcc.gnu.org/g:724db4b6920f23db62ad3a21abcc1908d8fe3ccf

commit 724db4b6920f23db62ad3a21abcc1908d8fe3ccf
Author: Matthew Malcomson <matthew.malcomson@arm.com>
Date:   Mon Mar 7 18:04:40 2022 +0000

    libgcc type handling.
    
    Here we update various places throughout the FDE searching code using PC
    addresses.  With the introduction of the distinction between an address
    and a pointer for capability architectures this has gotten a little
    unclear.
    
    The reasoning behind these changes is as follows:
      - read_encoded_value_with_base must be able to read in a capability,
        since we use that functionality for reading personality functions and
        landing pads.  Hence all variables which we read in using that
        function should have a capability type.
      - The PC addresses are never written as capabilities directly.  Hence
        reading in the addresses directly into capability types is a bit of
        a red flag.  The existing code did this in a few different places
        when the encoding of the FDE was DW_EH_PE_absptr.  This clause won't
        be entered for pure capability architectures, but it still makes for
        code which looks problematic to the reader.  Hence we switch the
        types here to be addresses, which are fine in both capability and
        non-capability architectures.
      - The ob->pc_begin member *is* kept as a capability for no real reason
        other than consistency with the other `struct object` members which
        are `void *`.  While reading in the PC start addresses of FDE's we
        could end up with a capability if the address is encoded in the
        right way, hence this member could end up containing a capability,
        but it's still only used for checking positions and hence could be
        an address.

Diff:
---
 libgcc/unwind-dw2-fde.c | 38 +++++++++++++++++++++-----------------
 1 file changed, 21 insertions(+), 17 deletions(-)

diff --git a/libgcc/unwind-dw2-fde.c b/libgcc/unwind-dw2-fde.c
index 26be05d4aca..b58b381fd1a 100644
--- a/libgcc/unwind-dw2-fde.c
+++ b/libgcc/unwind-dw2-fde.c
@@ -361,9 +361,9 @@ static int
 fde_unencoded_compare (struct object *ob __attribute__((unused)),
 		       const fde *x, const fde *y)
 {
-  _Unwind_Ptr x_ptr, y_ptr;
-  memcpy (&x_ptr, x->pc_begin, sizeof (_Unwind_Ptr));
-  memcpy (&y_ptr, y->pc_begin, sizeof (_Unwind_Ptr));
+  _Unwind_Address x_ptr, y_ptr;
+  memcpy (&x_ptr, x->pc_begin, sizeof (_Unwind_Address));
+  memcpy (&y_ptr, y->pc_begin, sizeof (_Unwind_Address));
 
   if (x_ptr > y_ptr)
     return 1;
@@ -721,8 +721,8 @@ add_fdes (struct object *ob, struct fde_accumulator *accu, const fde *this_fde)
 
       if (encoding == DW_EH_PE_absptr)
 	{
-	  _Unwind_Ptr ptr;
-	  memcpy (&ptr, this_fde->pc_begin, sizeof (_Unwind_Ptr));
+	  _Unwind_Address ptr;
+	  memcpy (&ptr, this_fde->pc_begin, sizeof (_Unwind_Address));
 	  if (ptr == 0)
 	    continue;
 	}
@@ -866,7 +866,7 @@ linear_search_fdes (struct object *ob, const fde *this_fde, _Unwind_Address pc)
 	}
       else
 	{
-	  _Unwind_Ptr mask;
+	  _Unwind_Address mask;
 	  const unsigned char *p;
 
 	  p = read_encoded_value_with_base (encoding, base,
@@ -876,9 +876,13 @@ linear_search_fdes (struct object *ob, const fde *this_fde, _Unwind_Address pc)
 	  /* Take care to ignore link-once functions that were removed.
 	     In these cases, the function address will be NULL, but if
 	     the encoding is smaller than a pointer a true NULL may not
-	     be representable.  Assume 0 in the representable bits is NULL.  */
+	     be representable.  Assume 0 in the representable bits is NULL.
+
+	     For capability targets we must check against the size of an
+	     address, since the size of a pointer includes metadata which does
+	     not determine whether the pointer is NULL or not.  */
 	  mask = size_of_encoded_value (encoding);
-	  if (mask < sizeof (void *))
+	  if (mask < sizeof (_Unwind_Address))
 	    mask = (((_Unwind_Ptr) 1) << (mask << 3)) - 1;
 	  else
 	    mask = -1;
@@ -887,7 +891,7 @@ linear_search_fdes (struct object *ob, const fde *this_fde, _Unwind_Address pc)
 	    continue;
 	}
 
-      if ((_Unwind_Ptr) pc - pc_begin < pc_range)
+      if (pc - (_Unwind_Address)pc_begin < (_Unwind_Address)pc_range)
 	return this_fde;
     }
 
@@ -907,12 +911,12 @@ binary_search_unencoded_fdes (struct object *ob, _Unwind_Address pc)
     {
       size_t i = (lo + hi) / 2;
       const fde *const f = vec->array[i];
-      void *pc_begin;
+      uaddr pc_begin;
       uaddr pc_range;
-      memcpy (&pc_begin, (const void * const *) f->pc_begin, sizeof (void *));
+      memcpy (&pc_begin, (const uaddr *) f->pc_begin, sizeof (uaddr));
       memcpy (&pc_range, (const uaddr *) f->pc_begin + 1, sizeof (uaddr));
 
-      if ((_Unwind_Address)pc < pc_begin)
+      if (pc < pc_begin)
 	hi = i;
       else if (pc >= pc_begin + pc_range)
 	lo = i + 1;
@@ -944,7 +948,7 @@ binary_search_single_encoding_fdes (struct object *ob, _Unwind_Address pc)
 
       if ((_Unwind_Address) pc < pc_begin)
 	hi = i;
-      else if ((_Unwind_Address) pc >= pc_begin + pc_range)
+      else if ((_Unwind_Address) pc >= pc_begin + (_Unwind_Address)pc_range)
 	lo = i + 1;
       else
 	return f;
@@ -975,7 +979,7 @@ binary_search_mixed_encoding_fdes (struct object *ob, _Unwind_Address pc)
 
       if ((_Unwind_Address) pc < pc_begin)
 	hi = i;
-      else if ((_Unwind_Address) pc >= pc_begin + pc_range)
+      else if ((_Unwind_Address) pc >= pc_begin + (_Unwind_Address)pc_range)
 	lo = i + 1;
       else
 	return f;
@@ -996,7 +1000,7 @@ search_object (struct object* ob, _Unwind_Address pc)
       /* Despite the above comment, the normal reason to get here is
 	 that we've not processed this object before.  A quick range
 	 check is in order.  */
-      if (pc < ob->pc_begin)
+      if (pc < (_Unwind_Address)ob->pc_begin)
 	return NULL;
     }
 
@@ -1054,7 +1058,7 @@ _Unwind_Find_FDE (_Unwind_Address pc, struct dwarf_eh_bases *bases)
      containing the pc.  Note that pc_begin is sorted descending, and
      we expect objects to be non-overlapping.  */
   for (ob = seen_objects; ob; ob = ob->next)
-    if (pc >= ob->pc_begin)
+    if (pc >= (_Unwind_Address)ob->pc_begin)
       {
 	f = search_object (ob, pc);
 	if (f)
@@ -1097,7 +1101,7 @@ _Unwind_Find_FDE (_Unwind_Address pc, struct dwarf_eh_bases *bases)
 	encoding = get_fde_encoding (f);
       read_encoded_value_with_base (encoding, base_from_object (encoding, ob),
 				    f->pc_begin, &func);
-      bases->func = func;
+      bases->func = (void *) func;
     }
 
   return f;