Use 2-region memory model in ARM rtos-less builds.

The following commits: #8039, #9092 added Boot/ISR stack definition to all scatter files (ARM_LIB_STACK).

This has changed memory model for RTOS-less builds to 2-region memory model and caused failure in case of rtos less builds.
This PR defines valid heap/stack regions for rtos-less builds.

Author: mprse

platform/mbed_retarget.cpp

@@ -904,21 +904,70 @@ extern "C" long PREFIX(_flen)(FILEHANDLE fh)
     return size;
 }
 
-extern "C" char Image$$RW_IRAM1$$ZI$$Limit[];
-
-extern "C" MBED_WEAK __value_in_regs struct __initial_stackheap _mbed_user_setup_stackheap(uint32_t R0, uint32_t R1, uint32_t R2, uint32_t R3)
-{
-    uint32_t zi_limit = (uint32_t)Image$$RW_IRAM1$$ZI$$Limit;
-    uint32_t sp_limit = __current_sp();
-
-    zi_limit = (zi_limit + 7) & ~0x7;    // ensure zi_limit is 8-byte aligned
+#if defined(TARGET_NUVOTON) || defined(TARGET_RZ_A1XX)
+extern char Image$$ARM_LIB_HEAP$$ZI$$Base[];
+extern char Image$$ARM_LIB_STACK$$ZI$$Base[];
+extern char Image$$ARM_LIB_HEAP$$ZI$$Limit[];
+#define HEAP_BASE (Image$$ARM_LIB_HEAP$$ZI$$Base)
+#define HEAP_LIMIT (Image$$ARM_LIB_HEAP$$ZI$$Limit)
+#define STACK_BASE (Image$$ARM_LIB_STACK$$ZI$$Base)
+#else
+extern char Image$$RW_IRAM1$$ZI$$Limit[];
+extern char Image$$ARM_LIB_STACK$$ZI$$Base[];
+#define HEAP_BASE (Image$$RW_IRAM1$$ZI$$Limit)
+#define HEAP_LIMIT (Image$$ARM_LIB_STACK$$ZI$$Base)
+#define STACK_BASE (Image$$ARM_LIB_STACK$$ZI$$Base)
+#endif
 
+extern __value_in_regs struct __initial_stackheap _mbed_user_setup_stackheap(uint32_t R0, uint32_t R1, uint32_t R2, uint32_t R3) {
     struct __initial_stackheap r;
-    r.heap_base = zi_limit;
-    r.heap_limit = sp_limit;
+    r.heap_base = (uint32_t)HEAP_BASE;
+    r.heap_limit = (uint32_t)HEAP_LIMIT;
     return r;
 }
 
+#ifndef 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$$Base/Limit if
+ * ARM_LIB_HEAP region is defined in scatter file.
+ *
+ * The overriding __rt_lib_init is needed only for rtos-less code. For rtos code, __rt_entry is
+ * overridden and the overriding __rt_lib_init here gets meaningless.
+ */
+extern "C" extern __value_in_regs struct __argc_argv $Super$$__rt_lib_init(unsigned heapbase, unsigned heaptop);
+
+extern "C" __value_in_regs struct __argc_argv $Sub$$__rt_lib_init (unsigned heapbase, unsigned heaptop)
+{
+    return $Super$$__rt_lib_init((unsigned)HEAP_BASE, (unsigned)HEAP_LIMIT);
+}
+
+#endif
+
 extern "C" __value_in_regs struct __initial_stackheap __user_setup_stackheap(uint32_t R0, uint32_t R1, uint32_t R2, uint32_t R3)
 {
     return _mbed_user_setup_stackheap(R0, R1, R2, R3);