Detect missing symbols used with kallsyms_lookup at compile time

[lttng-modules.git] / wrapper / writeback.h

diff --git a/wrapper/writeback.h b/wrapper/writeback.h
index cdcbd58444e0efbd8c3cca8cea04d6332c83f540..00d727cc3b0405713554275cd2997345cc7e0149 100644 (file)
--- a/wrapper/writeback.h
+++ b/wrapper/writeback.h
@@ -1,7 +1,5 @@
-#ifndef _LTTNG_WRAPPER_WRITEBACK_H
-#define _LTTNG_WRAPPER_WRITEBACK_H
-
-/*
+/* SPDX-License-Identifier: (GPL-2.0 or LGPL-2.1)
+ *
  * wrapper/writeback.h
  *
  * wrapper around global_dirty_limit read. Using KALLSYMS with KALLSYMS_ALL
@@ -9,27 +7,52 @@
  * exports this variable to GPL modules.
  *
  * Copyright (C) 2013 Mentor Graphics Corp.
- *
- * This library is free software; you can redistribute it and/or
- * modify it under the terms of the GNU Lesser General Public
- * License as published by the Free Software Foundation; only
- * version 2.1 of the License.
- *
- * This library is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- * Lesser General Public License for more details.
- *
- * You should have received a copy of the GNU Lesser General Public
- * License along with this library; if not, write to the Free Software
- * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
-#ifdef CONFIG_KALLSYMS_ALL
+#ifndef _LTTNG_WRAPPER_WRITEBACK_H
+#define _LTTNG_WRAPPER_WRITEBACK_H
+
+#include <lttng-kernel-version.h>
 
+#ifdef CONFIG_KALLSYMS_ALL
 #include <linux/kallsyms.h>
 #include <wrapper/kallsyms.h>
 
+
+
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(4,2,0)
+
+static struct wb_domain *global_wb_domain_sym;
+
+static inline
+unsigned long wrapper_global_dirty_limit(void)
+{
+       if (!global_wb_domain_sym)
+               global_wb_domain_sym =
+                       (void *) kallsyms_lookup_dataptr("global_wb_domain");
+       if (global_wb_domain_sym) {
+               return global_wb_domain_sym->dirty_limit;
+       } else {
+               printk_once(KERN_WARNING "LTTng: global_wb_domain symbol lookup failed.\n");
+               return 0;
+       }
+}
+
+/*
+ * Canary function to check for 'global_wb_domain' at compile time.
+ *
+ * From 'include/linux/writeback.h':
+ *
+ *   extern struct wb_domain global_wb_domain;
+ */
+static inline
+unsigned long __canary__global_wb_domain(void)
+{
+       return global_wb_domain.dirty_limit;
+}
+
+#else
+
 static unsigned long *global_dirty_limit_sym;
 
 static inline
@@ -46,7 +69,22 @@ unsigned long wrapper_global_dirty_limit(void)
        }
 }
 
-#else
+/*
+ * Canary function to check for 'global_dirty_limit' at compile time.
+ *
+ * From 'include/linux/writeback.h':
+ *
+ *   extern unsigned long global_dirty_limit;
+ */
+static inline
+unsigned long __canary__global_dirty_limit(void)
+{
+       return global_dirty_limit;
+}
+
+#endif
+
+#else /* CONFIG_KALLSYMS_ALL */
 
 #include <linux/writeback.h>