cpu/riscv_common: extend flashpage API

cpu/riscv_common/ldscripts/riscv_base.ld

@@ -34,6 +34,10 @@ SECTIONS
 {
   __stack_size     = DEFINED(__stack_size) ? __stack_size : 256;
 
+  /* Populate information about rom size */
+  _srom = ORIGIN(rom);
+  _erom = ORIGIN(rom) + LENGTH(rom);
+
   .init           :
   {
     KEEP (*(SORT_NONE(.init)))
@@ -213,4 +217,8 @@ SECTIONS
     . = __stack_size;
     PROVIDE( _sp = . );
   } >ram AT>ram :ram
+
+  .end_fw (NOLOAD) : ALIGN(4) {
+    _end_fw = . ;
+  } > rom
 }

cpu/riscv_common/periph/flashpage.c

@@ -0,0 +1,37 @@
+/*
+ * Copyright (C) 2021 Freie Universität Berlin
+ *
+ * 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     cpu_riscv_common
+ * @ingroup     drivers_periph_pm
+ * @{
+ * @file
+ * @brief       common periph/flashpage functions
+ *
+ * @author  Nils Ollrogge <nils.ollrogge@fu-berlin.de>
+ * @}
+ */
+
+#include "periph/flashpage.h"
+
+/**
+ * @brief   Memory markers, defined in the linker script
+ * @{
+ */
+extern uint32_t _end_fw;
+extern uint32_t _erom;
+
+unsigned flashpage_first_free(void)
+{
+    return flashpage_page(&_end_fw) + 1;
+}
+
+unsigned flashpage_last_free(void)
+{
+    return flashpage_page(&_erom) - 1;
+}