Add support of separate memories for heap and stack region swith the use of TWO_RAM_REGIONS define

Author: adustm

targets/TARGET_STM/TARGET_STM32L4/l4_retarget.c

@@ -0,0 +1,68 @@
+/**
+  ******************************************************************************
+  * @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)
+#if defined(TOOLCHAIN_GCC_ARM) || defined(TOOLCHAIN_GCC_CR)
+
+#include <errno.h>
+#include "stm32l4xx.h"
+extern uint32_t __mbed_sbrk_start;
+extern uint32_t __mbed_krbs_start;
+
+#define STM32L4_HEAP_ALIGN               32
+#define STM32L4_ALIGN_UP(X, ALIGN)       (((X) + (ALIGN) - 1) & ~((ALIGN) - 1))
+/**
+ * The default implementation of _sbrk() (in platform/mbed_retarget.cpp) for GCC_ARM requires one-region model (heap and 
+ * stack share one region), which doesn't fit two-region model (heap and stack are two distinct regions), for example, 
+ * STM32L475xG locates heap on SRAM1 and stack on SRAM2. 
+ * 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;
+    uint32_t heap_ind_old = STM32L4_ALIGN_UP(heap_ind, STM32L4_HEAP_ALIGN);
+    uint32_t heap_ind_new = STM32L4_ALIGN_UP(heap_ind_old + incr, STM32L4_HEAP_ALIGN);
+    
+    if (heap_ind_new > &__mbed_krbs_start) {
+        errno = ENOMEM;
+        return (void *) -1;
+    } 
+    
+    heap_ind = heap_ind_new;
+    
+    return (void *) heap_ind_old;
+}
+#endif /* GCC_ARM toolchain */
+#endif /* TWO_RAM_REGIONS */