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handle unwind tables that are embedded within unwinding code [PR111731]

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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.
This commit is contained in:
Thomas Neumann 2024-03-11 14:35:20 +01:00
parent a44d7e8a52
commit a364148530
1 changed files with 21 additions and 16 deletions
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37
libgcc/unwind-dw2-fde.c
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@ -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.