Commit GDB patch from Jacob Potter.

[netwatch.git] / include / tables.h

diff --git a/include/tables.h b/include/tables.h
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+/* tables.h
+ * Linker table helper macros.
+ * NetWatch system management mode administration console
+ *
+ * Copyright 2009, Google Inc.
+ * All rights reserved.
+ * 
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ * 
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,           
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY           
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef __TABLES_H
+#define __TABLES_H
+
+/* Linker tables are a beautiful, evil piece of magic.
+ *
+ * The idea is this;
+ * - For each table, define start and end pointers as zero-length arrays.
+ * - Define however many data values as constants of the appropriate type
+ * - Put each in its own section. For example, 'start' is in section
+ *   .table.foo; the data elemnts are in section .table.foo.1 (or other values
+ *   for explicit ordering); and 'end' is in .table.foo.END.
+ * - Merge the sections together with the following linker script entry:
+ *   *(SORT(.table.*))
+ *
+ * This has the effect that the start symbol points to the first value in the
+ * table, and the end symbol points to the last. The number of values is
+ * simply (table_foo_end - table_foo_start).
+ *
+ * And everything Just Works. Etherboot and the Linux kernel both use this
+ * for identifying linked-in modules; they have a somewhat more elaborate
+ * macro infastructure, but at the moment there are only two tables in
+ * NetWatch (network protocols and built-in drivers), so less is needed.
+ */
+
+#define PROTOCOL(x) void (* const x##_ptr)(void) \
+       __attribute__((section(".table.protocols.1"))) = x
+
+
+
+#define TABLE(typ, name) \
+       typ name##_table[0] __attribute__((section(".table." #name )));         \
+       typ name##_table_end[0] __attribute__((section(".table." #name ".END")));
+
+#define TABLE_LENGTH(name)     (name##_table_end - name##_table)
+
+#endif /* __TABLES_H */
+