RTX: Support stacks larger than 64k

This issue was originally reported on the mbed site:
 http://developer.mbed.org/questions/5570/mbed-rtos-memory-utilization/

The cause of the 64k limitation is that even though the user can set a
stack size larger than 64k in the osThreadDef_t::stacksize 32-bit
field, this size is truncated to 16-bit when it is copied to
the priv_stack field in the OS_TCB structure.

This commit corrects that problem by making the OS_TCB::priv_stack
field 32-bit.  Due to word alignment, this introduces another 2 bytes
of padding in the structure which I have made explicit with the
addition of the reserved2 field.

The tsk_stack field which follows priv_stack is referenced directly by
assembly language code responsible for context switching.  This context
switching code used a fixed byte offset, TCB_TSTACK, to access this
tsk_stack field.  I had to update the TCB_TSTACK definition in various
locations from 36 to 40 to account for the extra alignment padding and
increased size of the priv_stack field.

TESTING
* GCC_ARM - mbedLPC1768 and mbedLPC11U24
* Online mbed Compiler - mbedLPC1768 and mbedLPC11U24

NOTES: I had to change assembly language code that was specific to IAR
       but I don't have that toolchain so those changes aren't tested.
       They do however follow the same pattern as the tested GCC
       modifications.

Author: adamgreen

libraries/rtos/rtx/TARGET_CORTEX_M/TARGET_M0/TOOLCHAIN_GCC/HAL_CM0.s

@@ -35,7 +35,7 @@
         .file   "HAL_CM0.S"
         .syntax unified
 
-        .equ    TCB_TSTACK, 36
+        .equ    TCB_TSTACK, 40
 
 
 /*----------------------------------------------------------------------------

libraries/rtos/rtx/TARGET_CORTEX_M/TARGET_M0/TOOLCHAIN_IAR/HAL_CM0.s

@@ -34,7 +34,7 @@
 
         NAME    HAL_CM0.S
 
-        #define TCB_TSTACK 36
+        #define TCB_TSTACK 40
 
         EXTERN  os_flags
         EXTERN  os_tsk

libraries/rtos/rtx/TARGET_CORTEX_M/TARGET_M0P/TOOLCHAIN_GCC/HAL_CM0.s

@@ -35,7 +35,7 @@
         .file   "HAL_CM0.S"
         .syntax unified
 
-        .equ    TCB_TSTACK, 36
+        .equ    TCB_TSTACK, 40
 
 
 /*----------------------------------------------------------------------------

libraries/rtos/rtx/TARGET_CORTEX_M/TARGET_M0P/TOOLCHAIN_IAR/HAL_CM0.s

@@ -34,7 +34,7 @@
 
         NAME    HAL_CM0.S
 
-        #define TCB_TSTACK 36
+        #define TCB_TSTACK 40
 
         EXTERN  os_flags
         EXTERN  os_tsk

libraries/rtos/rtx/TARGET_CORTEX_M/TARGET_M3/TOOLCHAIN_GCC/HAL_CM3.s

@@ -35,7 +35,7 @@
         .file   "HAL_CM3.S"
         .syntax unified
 
-        .equ    TCB_TSTACK, 36
+        .equ    TCB_TSTACK, 40
 
 
 /*----------------------------------------------------------------------------

libraries/rtos/rtx/TARGET_CORTEX_M/TARGET_M3/TOOLCHAIN_IAR/HAL_CM3.s

@@ -34,7 +34,7 @@
 
         NAME    HAL_CM3.S
 
-        #define TCB_TSTACK 36
+        #define TCB_TSTACK 40
 
         EXTERN  os_flags
         EXTERN  os_tsk

libraries/rtos/rtx/TARGET_CORTEX_M/TARGET_M4/TOOLCHAIN_GCC/HAL_CM4.s

@@ -36,7 +36,7 @@
         .syntax unified
 
         .equ    TCB_STACKF, 32
-        .equ    TCB_TSTACK, 36
+        .equ    TCB_TSTACK, 40
 
 
 /*----------------------------------------------------------------------------

libraries/rtos/rtx/TARGET_CORTEX_M/TARGET_M4/TOOLCHAIN_IAR/HAL_CM4.s

@@ -35,7 +35,7 @@
         NAME    HAL_CM4.S
 
         #define TCB_STACKF 32
-        #define TCB_TSTACK 36
+        #define TCB_TSTACK 40
 
         EXTERN  os_flags
         EXTERN  os_tsk

libraries/rtos/rtx/TARGET_CORTEX_M/os_tcb.h

@@ -32,8 +32,9 @@ typedef struct OS_TCB {
 
   /* Hardware dependant part: specific for CM processor                      */
   U8     stack_frame;             /* Stack frame: 0=Basic, 1=Extended        */
-  U8     reserved;
-  U16    priv_stack;              /* Private stack size in bytes             */
+  U8     reserved1;
+  U16    reserved2;
+  U32    priv_stack;              /* Private stack size in bytes             */
   U32    tsk_stack;               /* Current task Stack pointer (R13)        */
   U32    *stack;                  /* Pointer to Task Stack memory block      */
 

libraries/rtos/rtx/TARGET_CORTEX_M/rt_TypeDef.h

@@ -41,7 +41,7 @@ typedef void    *OS_ID;
 typedef U32     OS_RESULT;
 
 #define TCB_STACKF      32        /* 'stack_frame' offset                    */
-#define TCB_TSTACK      36        /* 'tsk_stack' offset                      */
+#define TCB_TSTACK      40        /* 'tsk_stack' offset                      */
 
 typedef struct OS_PSFE {          /* Post Service Fifo Entry                 */
   void  *id;                      /* Object Identification                   */