[gcc r13-8555] handle unwind tables that are embedded within unwinding code [PR111731]

[Thomas Neumann via Gcc-cvs]

https://gcc.gnu.org/g:11f37868bb5812c4f0ac023909f5421595f68a43

commit r13-8555-g11f37868bb5812c4f0ac023909f5421595f68a43
Author: Thomas Neumann <tneum...@users.sourceforge.net>
Date:   Mon Mar 11 14:35:20 2024 +0100

    handle unwind tables that are embedded within unwinding code [PR111731]
    
    Original bug report: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111731
    
    The unwinding mechanism registers both the code range and the unwind
    table itself within a b-tree lookup structure. That data structure
    assumes that is consists of non-overlappping intervals. This
    becomes a problem if the unwinding table is embedded within the
    code itself, as now the intervals do overlap.
    
    To fix this problem we now keep the unwind tables in a separate
    b-tree, which prevents the overlap.
    
    libgcc/ChangeLog:
            PR libgcc/111731
            * unwind-dw2-fde.c: Split unwind ranges if they contain the
            unwind table.

Diff:
---
 libgcc/unwind-dw2-fde.c | 37 +++++++++++++++++++++----------------
 1 file changed, 21 insertions(+), 16 deletions(-)

diff --git a/libgcc/unwind-dw2-fde.c b/libgcc/unwind-dw2-fde.c
index 51129906fac..6a54450253f 100644
--- a/libgcc/unwind-dw2-fde.c
+++ b/libgcc/unwind-dw2-fde.c
@@ -48,6 +48,7 @@ typedef __UINTPTR_TYPE__ uintptr_type;
 #include "unwind-dw2-btree.h"
 
 static struct btree registered_frames;
+static struct btree registered_objects;
 static bool in_shutdown;
 
 static void
@@ -58,6 +59,7 @@ release_registered_frames (void)
   /* Release the b-tree and all frames. Frame releases that happen later are
    * silently ignored */
   btree_destroy (&registered_frames);
+  btree_destroy (&registered_objects);
   in_shutdown = true;
 }
 
@@ -103,6 +105,21 @@ static __gthread_mutex_t object_mutex;
 #endif
 #endif
 
+#ifdef ATOMIC_FDE_FAST_PATH
+// Register the pc range for a given object in the lookup structure.
+static void
+register_pc_range_for_object (uintptr_type begin, struct object *ob)
+{
+  // Register the object itself to know the base pointer on deregistration.
+  btree_insert (&registered_objects, begin, 1, ob);
+
+  // Register the frame in the b-tree
+  uintptr_type range[2];
+  get_pc_range (ob, range);
+  btree_insert (&registered_frames, range[0], range[1] - range[0], ob);
+}
+#endif
+
 /* Called from crtbegin.o to register the unwind info for an object.  */
 
 void
@@ -124,13 +141,7 @@ __register_frame_info_bases (const void *begin, struct 
object *ob,
 #endif
 
 #ifdef ATOMIC_FDE_FAST_PATH
-  // Register the object itself to know the base pointer on deregistration.
-  btree_insert (&registered_frames, (uintptr_type) begin, 1, ob);
-
-  // Register the frame in the b-tree
-  uintptr_type range[2];
-  get_pc_range (ob, range);
-  btree_insert (&registered_frames, range[0], range[1] - range[0], ob);
+  register_pc_range_for_object ((uintptr_type) begin, ob);
 #else
   init_object_mutex_once ();
   __gthread_mutex_lock (&object_mutex);
@@ -178,13 +189,7 @@ __register_frame_info_table_bases (void *begin, struct 
object *ob,
   ob->s.b.encoding = DW_EH_PE_omit;
 
 #ifdef ATOMIC_FDE_FAST_PATH
-  // Register the object itself to know the base pointer on deregistration.
-  btree_insert (&registered_frames, (uintptr_type) begin, 1, ob);
-
-  // Register the frame in the b-tree
-  uintptr_type range[2];
-  get_pc_range (ob, range);
-  btree_insert (&registered_frames, range[0], range[1] - range[0], ob);
+  register_pc_range_for_object ((uintptr_type) begin, ob);
 #else
   init_object_mutex_once ();
   __gthread_mutex_lock (&object_mutex);
@@ -232,7 +237,7 @@ __deregister_frame_info_bases (const void *begin)
 
 #ifdef ATOMIC_FDE_FAST_PATH
   // Find the originally registered object to get the base pointer.
-  ob = btree_remove (&registered_frames, (uintptr_type) begin);
+  ob = btree_remove (&registered_objects, (uintptr_type) begin);
 
   // Remove the corresponding PC range.
   if (ob)
@@ -240,7 +245,7 @@ __deregister_frame_info_bases (const void *begin)
       uintptr_type range[2];
       get_pc_range (ob, range);
       if (range[0] != range[1])
-    btree_remove (&registered_frames, range[0]);
+       btree_remove (&registered_frames, range[0]);
     }
 
   // Deallocate the sort array if any.