Mark asan fake stacks during machine stack marking

ASAN leaves a pointer to the fake frame on the stack; we can use the
__asan_addr_is_in_fake_stack API to work out the extent of the fake
stack and thus mark any VALUEs contained therein.

[Bug #20001]

1 files changed, 34 insertions, 2 deletions

diff --git a/gc.c b/gc.c
index a4de957340..2870b39bcf 100644
--- a/gc.c
+++ b/gc.c
@@ -953,6 +953,11 @@ typedef struct rb_objspace {
 
     rb_darray(VALUE *) weak_references;
     rb_postponed_job_handle_t finalize_deferred_pjob;
+
+#ifdef RUBY_ASAN_ENABLED
+    rb_execution_context_t *marking_machine_context_ec;
+#endif
+
 } rb_objspace_t;
 
 
@@ -6821,6 +6826,26 @@ mark_const_tbl(rb_objspace_t *objspace, struct rb_id_table *tbl)
 static void each_stack_location(rb_objspace_t *objspace, const rb_execution_context_t *ec,
                                  const VALUE *stack_start, const VALUE *stack_end, void (*cb)(rb_objspace_t *, VALUE));
 
+static void
+gc_mark_machine_stack_location_maybe(rb_objspace_t *objspace, VALUE obj)
+{
+    gc_mark_maybe(objspace, obj);
+
+#ifdef RUBY_ASAN_ENABLED
+    rb_execution_context_t *ec = objspace->marking_machine_context_ec;
+    void *fake_frame_start;
+    void *fake_frame_end;
+    bool is_fake_frame = asan_get_fake_stack_extents(
+        ec->thread_ptr->asan_fake_stack_handle, obj,
+        ec->machine.stack_start, ec->machine.stack_end,
+        &fake_frame_start, &fake_frame_end
+    );
+    if (is_fake_frame) {
+        each_stack_location(objspace, ec, fake_frame_start, fake_frame_end, gc_mark_maybe);
+    }
+#endif
+}
+
 #if defined(__wasm__)
 
 
@@ -6882,9 +6907,16 @@ mark_current_machine_context(rb_objspace_t *objspace, rb_execution_context_t *ec
     SET_STACK_END;
     GET_STACK_BOUNDS(stack_start, stack_end, 1);
 
-    each_location(objspace, save_regs_gc_mark.v, numberof(save_regs_gc_mark.v), gc_mark_maybe);
+#ifdef RUBY_ASAN_ENABLED
+    objspace->marking_machine_context_ec = ec;
+#endif
 
-    each_stack_location(objspace, ec, stack_start, stack_end, gc_mark_maybe);
+    each_location(objspace, save_regs_gc_mark.v, numberof(save_regs_gc_mark.v), gc_mark_machine_stack_location_maybe);
+    each_stack_location(objspace, ec, stack_start, stack_end, gc_mark_machine_stack_location_maybe);
+
+#ifdef RUBY_ASAN_ENABLED
+    objspace->marking_machine_context_ec = NULL;
+#endif
 }
 #endif