core: Introduce cross file arrays (XFA)

Co-Authored-By: Joakim Nohlgård <joakim.nohlgard@eistec.se>

Makefile.include

@@ -357,6 +357,11 @@ endif
 # Add standard include directories
 INCLUDES += -I$(RIOTBASE)/core/include -I$(RIOTBASE)/drivers/include -I$(RIOTBASE)/sys/include
 
+# Augmentation ldscript for cross file arrays (XFA)
+# this argument must come before any other -T options on the command line,
+# otherwise we get an error message ".text not found for insert"
+LINKFLAGS += -Txfa.ld
+
 # process provided features
 include $(RIOTBASE)/Makefile.features
 
@@ -416,6 +421,10 @@ TOOLCHAINS_SUPPORTED ?= gnu
 # Import all toolchain settings
 include $(RIOTMAKE)/toolchain/$(TOOLCHAIN).inc.mk
 
+# Append ldscript path after importing CPU and board makefiles to allow
+# overriding the core ldscripts
+LINKFLAGS += -L$(RIOTBASE)/core/ldscripts
+
 # Tell ccache to pass the original file to the compiler, instead of passing the
 # preprocessed code. Without this setting, the compilation will fail with
 # -Wimplicit-fallthrough warnings even when the fall through case is properly

core/include/xfa.h

@@ -0,0 +1,153 @@
+/*
+ * Copyright (C) 2016 Kaspar Schleiser <kaspar@schleiser.de>
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @ingroup     core_util
+ * @brief       Cross File Arrays
+ * @{
+ *
+ * This macro, in combination with an entry in the linker scripts, allows the
+ * definition of constant arrays to be spread over multiple C compilation
+ * units. These arrays are called "cross-file arrays" or short xfa.
+ *
+ *
+ *
+ * @file
+ * @author      Kaspar Schleiser <kaspar@schleiser.de>
+ */
+
+#ifndef XFA_H
+#define XFA_H
+
+/**
+ * @brief helper macro for other XFA_* macros
+ *
+ * @internal
+ */
+#define _XFA(name, prio) __attribute__((used, section(".xfa." #name "." #prio)))
+
+/**
+ * @brief helper macro for other XFA_* macros
+ *
+ * @internal
+ */
+#define _XFA_CONST(name, prio) __attribute__((used, section(".roxfa." #name "." #prio))) const
+
+/**
+ * @brief Define a read-only cross-file array
+ *
+ * This macro defines the symbols necessary to use XFA_START() and XFA_END().
+ * It needs to be part of one single compilation unit.
+ *
+ * @param[in]   type    name of the cross-file array
+ * @param[in]   name    name of the cross-file array
+ */
+#define XFA_INIT_CONST(type, name) \
+    _Pragma("GCC diagnostic push") \
+    _Pragma("GCC diagnostic ignored \"-Wpedantic\"") \
+    _XFA_CONST(name, 0_) const type name [0] = {}; \
+    _XFA_CONST(name, 9_) const type name ## _end [0] = {}; \
+    _Pragma("GCC diagnostic pop") \
+    extern const unsigned __xfa_dummy
+
+/**
+ * @brief Define a writable cross-file array
+ *
+ * This macro defines the symbols necessary to use XFA_START() and XFA_END().
+ * It needs to be part of one single compilation unit.
+ *
+ * @param[in]   type    name of the cross-file array
+ * @param[in]   name    name of the cross-file array
+ */
+#define XFA_INIT(type, name) \
+    _Pragma("GCC diagnostic push") \
+    _Pragma("GCC diagnostic ignored \"-Wpedantic\"") \
+    _XFA(name, 0_) type name [0] = {}; \
+    _XFA(name, 9_) type name ## _end [0] = {}; \
+    _Pragma("GCC diagnostic pop") \
+    extern const unsigned __xfa_dummy
+
+/**
+ * @brief Declare an external read-only cross-file array
+ *
+ * This macro defines the symbols necessary to use XFA_START() and XFA_END().
+ * Think of this as XFA_INIT() but with "extern" keyword.
+ * It is supposed to be used in compilation units where the cross file array is
+ * being accessed, but not defined using XFA_INIT.
+ *
+ * @param[in]   type    name of the cross-file array
+ * @param[in]   name    name of the cross-file array
+ */
+#define XFA_USE_CONST(type, name) \
+    extern const type name []; \
+    extern const type name ## _end []
+
+/**
+ * @brief Declare an external writable cross-file array
+ *
+ * This macro defines the symbols necessary to use XFA_START() and XFA_END().
+ * Think of this as XFA_INIT() but with "extern" keyword.
+ * It is supposed to be used in compilation units where the cross file array is
+ * being accessed, but not defined using XFA_INIT.
+ *
+ * @param[in]   type    name of the cross-file array
+ * @param[in]   name    name of the cross-file array
+ */
+#define XFA_USE(type, name) \
+    extern type name []; \
+    extern type name ## _end []
+
+/**
+ * @brief Define variable in writable cross-file array
+ *
+ * Variables will end up sorted by prio.
+ *
+ * Add this to the type in a variable definition, e.g.:
+ *
+ *     XFA(driver_params, 0) driver_params_t _onboard = { .pin=42 };
+ *
+ * @param[in]   name    name of the xfa
+ * @param[in]   prio    priority within the xfa
+ */
+#define XFA(xfa_name, prio) _XFA(xfa_name, 5_ ##prio)
+
+/**
+ * @brief Define variable in read-only cross-file array
+ *
+ * Variables will end up sorted by prio.
+ *
+ * Add this to the type in a variable definition, e.g.:
+ *
+ *     XFA(driver_params, 0) driver_params_t _onboard = { .pin=42 };
+ *
+ * @param[in]   name    name of the xfa
+ * @param[in]   prio    priority within the xfa
+ */
+#define XFA_CONST(xfa_name, prio) _XFA_CONST(xfa_name, 5_ ##prio)
+
+/**
+ * @brief Add a pointer to cross-file array
+ *
+ * Pointers will end up sorted by prio.
+ *
+ * @param[in]   xfa_name    name of the xfa
+ * @param[in]   prio        priority within the xfa
+ * @param[in]   name        symbol name
+ * @param[in]   entry       pointer variable to add to xfa
+ */
+#define XFA_ADD_PTR(xfa_name, prio, name, entry) \
+    _XFA_CONST(xfa_name, 5_ ##prio) \
+    const typeof(entry) xfa_name ## _ ## prio ## _ ## name = entry
+
+/**
+ * @brief Calculate number of entries in cross-file array
+ */
+#define XFA_LEN(type, name) (((const char*)name ## _end - (const char*)name) / sizeof(type))
+
+/** @} */
+#endif /* XFA_H */

core/ldscripts/xfa.ld

@@ -0,0 +1,23 @@
+SECTIONS
+{
+    .data :
+    {
+        KEEP (*(SORT(.xfa.*)))
+    }
+    __data_start = ADDR(.data);
+    __data_load_start = LOADADDR(.data);
+    __data_end = (__data_start + SIZEOF(.data));
+    __data_load_end = (__data_load_start + SIZEOF(.data));
+}
+
+INSERT AFTER .text;
+
+SECTIONS
+{
+    .rodata :
+    {
+        KEEP (*(SORT(.roxfa.*)))
+    }
+}
+
+INSERT AFTER .text;