Reposition heap at the end of RAM to be 4K aligned

HEAP memory should be 4K aligned for GCC newlib, with ISR stack at the end of
RAM memory we loose 3K of RAM memory. This fix is for device with <16K RAM to
use RAM entirely.

targets/TARGET_STM/TARGET_STM32F0/TARGET_NUCLEO_F070RB/device/TOOLCHAIN_GCC_ARM/STM32F070XB.ld

@@ -1,4 +1,5 @@
 /* Linker script to configure memory regions. */
+StackSize = 0x400;
 MEMORY
 { 
   FLASH (rx)      : ORIGIN = 0x08000000, LENGTH = 128k
@@ -113,6 +114,20 @@ SECTIONS
 
     } > RAM
 
+    /* .stack section doesn't contains any symbols. It is only
+     * used for linker to reserve space for the main stack section
+     */
+    .stack (NOLOAD):
+    {
+        __StackLimit = .;
+        *(.stack*);
+        . += StackSize - (. - __StackLimit);
+    } > RAM
+    __StackTop = ADDR(.stack) + SIZEOF(.stack);
+    _estack = __StackTop;
+    __StackLimit = ADDR(.stack);
+    PROVIDE(__stack = __StackTop);
+
     .bss :
     {
         . = ALIGN(4);
@@ -129,25 +144,13 @@ SECTIONS
     {
         __end__ = .;
         end = __end__;
-        *(.heap*)
+        *(.heap*);
+        . += (ORIGIN(RAM) + LENGTH(RAM) - .);
         __HeapLimit = .;
     } > RAM
 
-    /* .stack_dummy section doesn't contains any symbols. It is only
-     * used for linker to calculate size of stack sections, and assign
-     * values to stack symbols later */
-    .stack_dummy (COPY):
-    {
-        *(.stack*)
-    } > RAM
+    PROVIDE(__heap_size = SIZEOF(.heap));
+    PROVIDE(__mbed_sbrk_start = ADDR(.heap));
+    PROVIDE(__mbed_krbs_start = ADDR(.heap) + SIZEOF(.heap));
 
-    /* Set stack top to end of RAM, and stack limit move down by
-     * size of stack_dummy section */
-    __StackTop = ORIGIN(RAM) + LENGTH(RAM);
-    _estack = __StackTop;
-    __StackLimit = __StackTop - SIZEOF(.stack_dummy);
-    PROVIDE(__stack = __StackTop);
-
-    /* Check if data + heap + stack exceeds RAM limit */
-    ASSERT(__StackLimit >= __HeapLimit, "region RAM overflowed with stack")
 }

targets/TARGET_STM/TARGET_STM32F0/TARGET_NUCLEO_F070RB/device/TOOLCHAIN_GCC_ARM/STM32F0xxx_retarget.c

@@ -0,0 +1,54 @@
+/* mbed Microcontroller Library
+ * Copyright (c) 2018, STMicroelectronics
+ * All rights reserved.
+ *
+ * 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.
+ */
+#include <errno.h>
+#include "stm32f0xx.h"
+extern uint32_t __mbed_sbrk_start;
+extern uint32_t __mbed_krbs_start;
+
+/* Support heap with two-region model
+ *
+ * The default implementation of _sbrk() (in 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)
+ * Hence, override _sbrk() here to support heap with two-region model.
+ */
+void *_sbrk(int incr)
+{
+    static uint32_t heap_ind = (uint32_t) &__mbed_sbrk_start;
+    uint32_t heap_ind_old = heap_ind;
+    uint32_t heap_ind_new = heap_ind_old + incr;
+
+    if (heap_ind_new > (uint32_t) &__mbed_krbs_start) {
+        errno = ENOMEM;
+        return (void *) -1;
+    }
+
+    heap_ind = heap_ind_new;
+
+    return (void *) heap_ind_old;
+}

targets/TARGET_STM/TARGET_STM32F0/TARGET_NUCLEO_F072RB/device/TOOLCHAIN_GCC_ARM/STM32F072XB.ld

@@ -1,4 +1,5 @@
 /* Linker script to configure memory regions. */
+StackSize = 0x400;
 MEMORY
 { 
   FLASH (rx)      : ORIGIN = 0x08000000, LENGTH = 128k
@@ -113,6 +114,20 @@ SECTIONS
 
     } > RAM
 
+    /* .stack section doesn't contains any symbols. It is only
+     * used for linker to reserve space for the main stack section
+     */
+    .stack (NOLOAD):
+    {
+        __StackLimit = .;
+        *(.stack*);
+        . += StackSize - (. - __StackLimit);
+    } > RAM
+    __StackTop = ADDR(.stack) + SIZEOF(.stack);
+    _estack = __StackTop;
+    __StackLimit = ADDR(.stack);
+    PROVIDE(__stack = __StackTop);
+
     .bss :
     {
         . = ALIGN(4);
@@ -129,25 +144,13 @@ SECTIONS
     {
         __end__ = .;
         end = __end__;
-        *(.heap*)
+        *(.heap*);
+        . += (ORIGIN(RAM) + LENGTH(RAM) - .);
         __HeapLimit = .;
     } > RAM
 
-    /* .stack_dummy section doesn't contains any symbols. It is only
-     * used for linker to calculate size of stack sections, and assign
-     * values to stack symbols later */
-    .stack_dummy (COPY):
-    {
-        *(.stack*)
-    } > RAM
+    PROVIDE(__heap_size = SIZEOF(.heap));
+    PROVIDE(__mbed_sbrk_start = ADDR(.heap));
+    PROVIDE(__mbed_krbs_start = ADDR(.heap) + SIZEOF(.heap));
 
-    /* Set stack top to end of RAM, and stack limit move down by
-     * size of stack_dummy section */
-    __StackTop = ORIGIN(RAM) + LENGTH(RAM);
-    _estack = __StackTop;
-    __StackLimit = __StackTop - SIZEOF(.stack_dummy);
-    PROVIDE(__stack = __StackTop);
-
-    /* Check if data + heap + stack exceeds RAM limit */
-    ASSERT(__StackLimit >= __HeapLimit, "region RAM overflowed with stack")
 }

targets/TARGET_STM/TARGET_STM32F0/TARGET_NUCLEO_F072RB/device/TOOLCHAIN_GCC_ARM/STM32F0xxx_retarget.c

@@ -0,0 +1,54 @@
+/* mbed Microcontroller Library
+ * Copyright (c) 2018, STMicroelectronics
+ * All rights reserved.
+ *
+ * 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.
+ */
+#include <errno.h>
+#include "stm32f0xx.h"
+extern uint32_t __mbed_sbrk_start;
+extern uint32_t __mbed_krbs_start;
+
+/* Support heap with two-region model
+ *
+ * The default implementation of _sbrk() (in 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)
+ * Hence, override _sbrk() here to support heap with two-region model.
+ */
+void *_sbrk(int incr)
+{
+    static uint32_t heap_ind = (uint32_t) &__mbed_sbrk_start;
+    uint32_t heap_ind_old = heap_ind;
+    uint32_t heap_ind_new = heap_ind_old + incr;
+
+    if (heap_ind_new > (uint32_t) &__mbed_krbs_start) {
+        errno = ENOMEM;
+        return (void *) -1;
+    }
+
+    heap_ind = heap_ind_new;
+
+    return (void *) heap_ind_old;
+}

targets/TARGET_STM/mbed_rtx.h

@@ -137,10 +137,22 @@ extern uint32_t               __HeapLimit[];
 #endif
 
 #if (defined(TARGET_STM32F070RB) || defined(TARGET_STM32F072RB))
+#if (defined(__GNUC__) && !defined(__CC_ARM) && !defined(__ARMCC_VERSION))
+extern uint32_t               __StackLimit;
+extern uint32_t               __StackTop;
+extern uint32_t               __end__;
+extern uint32_t               __HeapLimit;
+#define HEAP_START            ((unsigned char*) &__end__)
+#define HEAP_SIZE             ((uint32_t)((uint32_t) &__HeapLimit - (uint32_t) HEAP_START))
+#define ISR_STACK_START       ((unsigned char*) &__StackLimit)
+#define ISR_STACK_SIZE        ((uint32_t)((uint32_t) &__StackTop - (uint32_t) &__StackLimit))
+#endif
+
 #ifdef MBED_CONF_RTOS_MAIN_THREAD_STACK_SIZE
 #undef MBED_CONF_RTOS_MAIN_THREAD_STACK_SIZE
 #endif
 #define MBED_CONF_RTOS_MAIN_THREAD_STACK_SIZE 3072
+
 #endif
 
 #endif  // MBED_MBED_RTX_H