Migrate NUCLEO_F303K8 to Mbed OS 5 baremetal

* Use two memory regions in ARM toolchain linker file to support Microlib
* Replace `target.default_lib` with `target.c_lib`
* Specify supported lib sizes per toolchain
* Add support for Mbed OS 5

Author: hugueskamba

targets/TARGET_STM/TARGET_STM32F3/TARGET_STM32F303x8/device/TOOLCHAIN_ARM_STD/stm32f303x8.sct

@@ -28,27 +28,49 @@
 ; OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
+#if !defined(MBED_APP_START)
+  #define MBED_APP_START            0x08000000
+#endif
+
+; STM32F303K8: 64KB FLASH (0x10000)
+#if !defined(MBED_APP_SIZE)
+  #define MBED_APP_SIZE             0x10000
+#endif
+
+#if !defined(MBED_RAM_START)
+  #define MBED_RAM_START            0x20000000
+#endif
+
+;12KB SRAM (0x3000)
+#if !defined(MBED_RAM_SIZE)
+  #define MBED_RAM_SIZE             0x3000
+#endif
+
+
 #if !defined(MBED_BOOT_STACK_SIZE)
-  #define MBED_BOOT_STACK_SIZE 0x400
+  #define MBED_BOOT_STACK_SIZE      0x400
 #endif
 
-#define Stack_Size MBED_BOOT_STACK_SIZE
+; 60 Non-Core vectors + 16 ARM Core System Handler Vectors vectors + reserved areas = 98 vectors 392 bytes (0x188) to be reserved in RAM
+#define VECTOR_SIZE                 0x188
+
+#define RAM_FIXED_SIZE              (MBED_BOOT_STACK_SIZE+VECTOR_SIZE)
 
-; STM32F303K8: 64KB FLASH (0x10000) + 12KB SRAM (0x3000)
-LR_IROM1 0x08000000 0x10000  {    ; load region size_region
+LR_IROM1  MBED_APP_START  MBED_APP_SIZE  {    ; load region size_region
 
-  ER_IROM1 0x08000000 0x10000  {  ; load address = execution address
+  ER_IROM1  MBED_APP_START  MBED_APP_SIZE  {  ; load address = execution address
    *.o (RESET, +First)
    *(InRoot$$Sections)
    .ANY (+RO)
   }
 
-  ; 98 vectors = 392 bytes (0x188) to be reserved in RAM
-  RW_IRAM1 (0x20000000+0x188) (0x3000-0x188-Stack_Size)  {  ; RW data
+  RW_IRAM1  (MBED_RAM_START+VECTOR_SIZE)  (MBED_RAM_SIZE-VECTOR_SIZE)  {  ; RW data
    .ANY (+RW +ZI)
   }
 
-  ARM_LIB_STACK (0x20000000+0x3000) EMPTY -Stack_Size { ; stack
+  ARM_LIB_HEAP  AlignExpr(+0, 16)  EMPTY  (MBED_RAM_SIZE-RAM_FIXED_SIZE+MBED_RAM_START-AlignExpr(ImageLimit(RW_IRAM1), 16))  {
   }
-}
 
+  ARM_LIB_STACK  (MBED_RAM_START+MBED_RAM_SIZE)  EMPTY  -MBED_BOOT_STACK_SIZE { ; stack
+  }
+}

targets/TARGET_STM/TARGET_STM32F3/TARGET_STM32F303x8/device/TOOLCHAIN_GCC_ARM/STM32F303X8.ld

@@ -6,6 +6,7 @@
 
 STACK_SIZE = MBED_BOOT_STACK_SIZE;
 
+/* 60 Non-Core vectors + 16 ARM Core System Handler Vectors vectors + reserved areas = 392 bytes (0x188) to be reserved in RAM */
 MEMORY
 { 
   FLASH (rx) : ORIGIN = 0x08000000, LENGTH = 64K

targets/targets.json

@@ -2807,6 +2807,11 @@
             "IAR",
             "GCC_ARM"
         ],
+        "supported_c_libs": {
+            "arm": ["std", "small"],
+            "gcc_arm": ["std", "small"],
+            "iar": ["std"]
+        },
         "macros": [
             "USE_HAL_DRIVER",
             "USE_FULL_LL_DRIVER",
@@ -3630,12 +3635,14 @@
             }
         },
         "overrides": {
-            "lse_available": 0
+            "lse_available": 0,
+            "boot-stack-size": "0x400",
+            "tickless-from-us-ticker": true
         },
         "detect_code": [
             "0775"
         ],
-        "default_lib": "small",
+        "c_lib": "small",
         "device_has_add": [
             "ANALOGOUT",
             "CAN",
@@ -3645,7 +3652,7 @@
             "LPTICKER"
         ],
         "release_versions": [
-            "2"
+            "2", "5"
         ],
         "device_name": "STM32F303K8"
     },