Added a generalised table infrastructure, so that we don't have to

keep adding new tables to each architecture's linker scripts.

1 files changed, 56 insertions, 0 deletions

diff --git a/src/include/tables.h b/src/include/tables.h
new file mode 100644
index 000000000..48514464e
--- /dev/null
+++ b/src/include/tables.h
@@ -0,0 +1,56 @@
+#ifndef TABLES_H
+#define TABLES_H
+
+/*
+ * Macros for dealing with linker-generated tables of fixed-size
+ * symbols.  We make fairly extensive use of these in order to avoid
+ * ifdef spaghetti and/or linker symbol pollution.  For example,
+ * instead of having code such as
+ *
+ * #ifdef CONSOLE_SERIAL
+ *   serial_init();
+ * #endif
+ *
+ * we make serial.c generate an entry in the initialisation function
+ * table, and then have a function call_init_fns() that simply calls
+ * all functions present in this table.  If and only if serial.o gets
+ * linked in, then its initialisation function will be called.  We
+ * avoid linker symbol pollution (i.e. always dragging in serial.o
+ * just because of a call to serial_init()) and we also avoid ifdef
+ * spaghetti (having to conditionalise every reference to functions in
+ * serial.c).
+ *
+ * The linker script takes care of assembling the tables for us.  All
+ * our table sections have names of the format ".tbl.NAME.NN" where
+ * NAME designates the data structure stored in the table
+ * (e.g. "init_fn") and NN is a two-digit decimal number used to
+ * impose an ordering upon the tables if required.  NN=00 is reserved
+ * for the symbol indicating "table start", and NN=99 is reserved for
+ * the symbol indicating "table end".
+ *
+ * To define an entry in the "xxx" table:
+ *
+ *  static struct xxx my_xxx __table(xxx,01) = { ... };
+ *
+ * To access start and end markers for the "xxx" table:
+ *
+ *  static struct xxx xxx_start[0] __table_start(xxx);
+ *  static struct xxx xxx_end[0] __table_end(xxx);
+ *
+ * See init.h and init.c for an example of how these macros are used
+ * in practice.
+ *
+ */
+
+#define __table_str(x) #x
+#define __table_section(table,idx) \
+	__section__ ( ".tbl." __table_str(table) "." __table_str(idx) )
+
+#define __table_section_start(table) __table_section(table,00)
+#define __table_section_end(table) __table_section(table,99)
+
+#define __table(table,idx) __attribute__ (( __table_section(table,idx) ))
+#define __table_start(table) __attribute__ (( __table_section_start(table) ))
+#define __table_end(table) __attribute__ (( __table_section_end(table) ))
+
+#endif /* TABLES_H */