[Nuvoton] Fix __user_setup_stackheap and ARM_LIB_STACK/ARM_LIB_HEAP cannot co-exist in RTOS-less build

Author: ccli8

targets/TARGET_NUVOTON/TOOLCHAIN_ARM/sys.cpp

@@ -27,6 +27,48 @@ extern __value_in_regs struct __initial_stackheap _mbed_user_setup_stackheap(uin
     return r;
 }
 
+#if !defined(MBED_CONF_RTOS_PRESENT) || !MBED_CONF_RTOS_PRESENT
+
+/* The single region memory model would check stack collision at run time, verifying that
+ * the heap pointer is underneath the stack pointer. With two-region memory model/RTOS-less or
+ * multiple threads(stacks)/RTOS, the check gets meaningless and we must disable it. */
+#if defined (__ARMCC_VERSION) && (__ARMCC_VERSION >= 6010050)
+__asm(".global __use_two_region_memory\n\t");
+__asm(".global __use_no_semihosting\n\t");
+#else
+#pragma import(__use_two_region_memory)
+#endif
+
+/* Fix __user_setup_stackheap and ARM_LIB_STACK/ARM_LIB_HEAP cannot co-exist in RTOS-less build
+ *
+ * According AN241 (http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dai0241b/index.html),
+ * __rt_entry has the following call sequence:
+ * 1. _platform_pre_stackheap_init
+ * 2. __user_setup_stackheap or setup the Stack Pointer (SP) by another method
+ * 3. _platform_post_stackheap_init
+ * 4. __rt_lib_init
+ * 5. _platform_post_lib_init
+ * 6. main()
+ * 7. exit()
+ *
+ * Per our check, when __user_setup_stackheap and ARM_LIB_STACK/ARM_LIB_HEAP co-exist, neither
+ * does __user_setup_stackheap get called and nor is ARM_LIB_HEAP used to get heap base/limit,
+ * which are required to pass to __rt_lib_init later. To fix the issue, by subclass'ing
+ * __rt_lib_init, heap base/limit are replaced with Image$$ARM_LIB_HEAP$$ZI$$Base/Limit if
+ * ARM_LIB_HEAP region is defined in scatter file.
+ *
+ * The overriding __rt_lib_init is needed only for rtos-less code. For rtos code, __rt_entry is
+ * overridden and the overriding __rt_lib_init here gets meaningless.
+ */
+extern __value_in_regs struct __argc_argv $Super$$__rt_lib_init(unsigned heapbase, unsigned heaptop);
+
+__value_in_regs struct __argc_argv $Sub$$__rt_lib_init (unsigned heapbase, unsigned heaptop)
+{
+    return $Super$$__rt_lib_init((unsigned) Image$$ARM_LIB_HEAP$$Base, (unsigned) Image$$ARM_LIB_HEAP$$ZI$$Limit);
+}
+
+#endif
+
 #ifdef __cplusplus
 }
 #endif