Expand sbrk to allocate memory from two regions

Author: Marcus Chang

targets/TARGET_STM/TARGET_STM32L4/TARGET_STM32L475xG/device/TOOLCHAIN_GCC_ARM/STM32L475XX.ld

@@ -16,7 +16,7 @@ M_CRASH_DATA_RAM_SIZE = 0x100;
 
 /* Linker script to configure memory regions. */
 MEMORY
-{ 
+{
   FLASH (rx)   : ORIGIN = MBED_APP_START, LENGTH = MBED_APP_SIZE
   SRAM2 (rwx)  : ORIGIN = 0x10000188, LENGTH = 32k - 0x188
   SRAM1 (rwx)  : ORIGIN = 0x20000000, LENGTH = 96k
@@ -26,7 +26,7 @@ MEMORY
  * with other linker script that defines memory regions FLASH and RAM.
  * It references following symbols, which must be defined in code:
  *   Reset_Handler : Entry of reset handler
- * 
+ *
  * It defines following symbols, which code can use without definition:
  *   __exidx_start
  *   __exidx_end
@@ -93,7 +93,7 @@ SECTIONS
 
     __etext = .;
     _sidata = .;
-    
+
     .crash_data_ram :
     {
         . = ALIGN(8);
@@ -173,6 +173,10 @@ SECTIONS
     .stack_dummy (COPY):
     {
         *(.stack*)
+        . += (ORIGIN(SRAM2) + STACK_SIZE - .);
+        __mbed_sbrk_start_0 = .;
+        . += (ORIGIN(SRAM2) + LENGTH(SRAM2) - .);
+        __mbed_krbs_start_0 = .;
     } > SRAM2
 
     /* Set stack top to end of RAM, and stack limit move down by

targets/TARGET_STM/TARGET_STM32L4/l4_retarget.c

@@ -0,0 +1,78 @@
+/**
+  ******************************************************************************
+  * @file    l4_retarget.c
+ * @author   MCD Application Team
+  * @brief   CMSIS Cortex-M4 Core Peripheral Access Layer Source File for STM32L475xG
+  ******************************************************************************
+  * @attention
+  *
+  * <h2><center>&copy; COPYRIGHT(c) 2018 STMicroelectronics</center></h2>
+  *
+  * Redistribution and use in source and binary forms, with or without modification,
+  * are permitted provided that the following conditions are met:
+  *   1. Redistributions of source code must retain the above copyright notice,
+  *      this list of conditions and the following disclaimer.
+  *   2. 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.
+  *   3. Neither the name of STMicroelectronics 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 HOLDER 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.
+  *
+  ******************************************************************************
+  */
+#if (defined(TWO_RAM_REGIONS) && defined(__GNUC__) && !defined(__CC_ARM) && !defined(__ARMCC_VERSION))
+#include <stdbool.h>
+#include <errno.h>
+#include "stm32l4xx.h"
+extern uint32_t __mbed_sbrk_start;
+extern uint32_t __mbed_krbs_start;
+extern uint32_t __mbed_sbrk_start_0;
+extern uint32_t __mbed_krbs_start_0;
+
+/**
+ * The default implementation of _sbrk() (in platform/mbed_retarget.cpp) for GCC_ARM only supports one region.
+ * This implementation supports two regions by continuing the allocation to the second region after the first
+ * one is full.
+ * Define __wrap__sbrk() to override the default _sbrk(). It is expected to get called through gcc
+ * hooking mechanism ('-Wl,--wrap,_sbrk') or in _sbrk().
+ */
+void *__wrap__sbrk(int incr)
+{
+    static uint32_t heap_ind = (uint32_t) &__mbed_sbrk_start_0;
+    static bool once = true;
+    uint32_t heap_ind_old = heap_ind;
+    uint32_t heap_ind_new = heap_ind_old + incr;
+
+    /**
+     * If the new address is outside the first region, start allocating from the second region.
+     */
+    if (once && (heap_ind_new >= (uint32_t)&__mbed_krbs_start_0)) {
+        once = false;
+        heap_ind_old = (uint32_t)&__mbed_sbrk_start;
+        heap_ind_new = heap_ind_old + incr;
+    /**
+     * If the new address is outside the second region, return out-of-memory.
+     */
+    } else if (heap_ind_new >= (uint32_t)&__mbed_krbs_start) {
+        errno = ENOMEM;
+        return (void *) - 1;
+    }
+
+    heap_ind = heap_ind_new;
+
+    return (void *) heap_ind_old;
+}
+#endif /* GCC_ARM toolchain && TWO_RAM_REGIONS*/
+