cpu/cortexm_common: add .backup.noinit section

Author: derMihai

cpu/cortexm_common/include/cpu_conf_common.h

@@ -162,6 +162,12 @@ extern "C" {
  *          and initialized with user provided data on cold boot.
  */
 #define BACKUP_RAM_DATA __attribute__((section(".backup.data")))
+
+/**
+ * @brief   Memory marked with this attribute is retained during deep sleep
+ *          and never initialized.
+ */
+#define BACKUP_RAM_NOINIT __attribute__((section(".backup.noinit")))
 #endif /* CPU_HAS_BACKUP_RAM */
 
 /**

cpu/cortexm_common/ldscripts/cortexm_base.ld

@@ -229,6 +229,12 @@ SECTIONS
         . = ALIGN(4);
     } > bkup_ram
 
+    .backup.noinit (NOLOAD) : ALIGN(4) {
+        _sbackup_noinit = .;
+        *(.backup.noinit)
+        _ebackup_noinit = .;
+    } > bkup_ram
+
     .heap3 (NOLOAD) : ALIGN(4) {
         _sheap1 = . ;
         _eheap1 = ORIGIN(bkup_ram) + LENGTH(bkup_ram);