Fix stack alignment for EABI floating point

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@4089 42af7a65-404d-4744-a932-0658087f49c3

5 files changed, 121 insertions, 43 deletions

diff --git a/nuttx/ChangeLog b/nuttx/ChangeLog
index b752b8ec3..2f83184f6 100644
--- a/nuttx/ChangeLog
+++ b/nuttx/ChangeLog
@@ -2194,4 +2194,7 @@
 	  support a file system (such as NXFFS). (Contributed by Hal Glenn).
 	* include/nuttx/rgbcolors.h: More fixes to RGB color conversion
 	  macros.
+	* arch/arm/src/common/up_createstack.c and up_usestack.c:  For ARM EABI
+	  the stack must be aligned to 8-byte boundaries.  This is necessary for
+	  passing aligned floating point values under EABI.
 
diff --git a/nuttx/Documentation/NuttxPortingGuide.html b/nuttx/Documentation/NuttxPortingGuide.html
index 7d190a146..f4c699541 100644
--- a/nuttx/Documentation/NuttxPortingGuide.html
+++ b/nuttx/Documentation/NuttxPortingGuide.html
@@ -5114,7 +5114,12 @@ build
     some functions into RAM, either for better performance or for errata workarounds.
   </li>
   <li>
-    <code>CONFIG_STACK_POINTER</code>: The initial stack pointer
+    <code>CONFIG_STACK_POINTER</code>: The initial stack pointer (may not be supported
+    in all architectures).
+  </li>
+  <li>
+    <code>CONFIG_STACK_ALIGNMENT</code>: Set if the your application has specific
+    stack alignment requirements (may not be supported in all architectures).
   </li>
   <li>
     <code>CONFIG_IDLETHREAD_STACKSIZE</code>: The size of the initial stack.
diff --git a/nuttx/arch/arm/src/common/up_createstack.c b/nuttx/arch/arm/src/common/up_createstack.c
index 0d78d9ce9..068924b4b 100644
--- a/nuttx/arch/arm/src/common/up_createstack.c
+++ b/nuttx/arch/arm/src/common/up_createstack.c
@@ -52,6 +52,33 @@
 #include "up_internal.h"
 
 /****************************************************************************
+ * Pre-processor Macros
+ ****************************************************************************/
+
+/* ARM requires at least a 4-byte stack alignment.  For use with EABI and
+ * floating point, the stack must be aligned to 8-byte addresses.
+ */
+
+#ifndef CONFIG_STACK_ALIGNMENT
+
+/* The symbol  __ARM_EABI__ is defined by GCC if EABI is being used.  If you
+ * are not using GCC, make sure that CONFIG_STACK_ALIGNMENT is set correctly!
+ */
+
+#  ifdef __ARM_EABI__
+#    define CONFIG_STACK_ALIGNMENT 8
+#  else
+#    define CONFIG_STACK_ALIGNMENT 4
+#  endif
+#endif
+
+/* Stack alignment macros */
+
+#define STACK_ALIGN_MASK    (CONFIG_STACK_ALIGNMENT-1)
+#define STACK_ALIGN_DOWN(a) ((a) & ~STACK_ALIGN_MASK)
+#define STACK_ALIGN_UP(a)   (((a) + STACK_ALIGN_MASK) & ~STACK_ALIGN_MASK)
+
+/****************************************************************************
  * Private Types
  ****************************************************************************/
 
@@ -110,54 +137,60 @@ int up_create_stack(_TCB *tcb, size_t stack_size)
       tcb->stack_alloc_ptr = NULL;
     }
 
-   if (!tcb->stack_alloc_ptr)
-     {
+  if (!tcb->stack_alloc_ptr)
+    {
 #ifdef CONFIG_DEBUG
-       tcb->stack_alloc_ptr = (uint32_t*)kzalloc(stack_size);
+      tcb->stack_alloc_ptr = (uint32_t*)kzalloc(stack_size);
 #else
-       tcb->stack_alloc_ptr = (uint32_t*)kmalloc(stack_size);
+      tcb->stack_alloc_ptr = (uint32_t*)kmalloc(stack_size);
 #endif
-     }
+    }
 
-   if (tcb->stack_alloc_ptr)
-     {
-       size_t top_of_stack;
-       size_t size_of_stack;
+  if (tcb->stack_alloc_ptr)
+    {
+      size_t top_of_stack;
+      size_t size_of_stack;
+
+      /* The ARM uses a push-down stack:  the stack grows toward lower
+       * addresses in memory.  The stack pointer register, points to
+       * the lowest, valid work address (the "top" of the stack).  Items
+       * on the stack are referenced as positive word offsets from sp.
+       */
 
-       /* The ARM uses a push-down stack:  the stack grows
-        * toward loweraddresses in memory.  The stack pointer
-        * register, points to the lowest, valid work address
-        * (the "top" of the stack).  Items on the stack are
-        * referenced as positive word offsets from sp.
-        */
+      top_of_stack = (uint32_t)tcb->stack_alloc_ptr + stack_size - 4;
 
-       top_of_stack = (uint32_t)tcb->stack_alloc_ptr + stack_size - 4;
+      /* The ARM stack must be aligned; 4 byte alignment for OABI and
+       * 8-byte alignment for EABI. If necessary top_of_stack must be
+       * rounded down to the next boundary
+       */
 
-       /* The ARM stack must be aligned at word (4 byte)
-        * boundaries. If necessary top_of_stack must be rounded
-        * down to the next boundary
-        */
+      top_of_stack = STACK_ALIGN_DOWN(top_of_stack);
 
-       top_of_stack &= ~3;
-       size_of_stack = top_of_stack - (uint32_t)tcb->stack_alloc_ptr + 4;
+      /* The size of the stack in bytes is then the difference between
+       * the top and the bottom of the stack (+4 because if the top
+       * is the same as the bottom, then the size is one 32-bit element).
+       * The size need not be aligned.
+       */
 
-       /* Save the adjusted stack values in the _TCB */
+      size_of_stack = top_of_stack - (uint32_t)tcb->stack_alloc_ptr + 4;
 
-       tcb->adj_stack_ptr  = (uint32_t*)top_of_stack;
-       tcb->adj_stack_size = size_of_stack;
+      /* Save the adjusted stack values in the _TCB */
 
-       /* If stack debug is enabled, then fill the stack with a
-        * recognizable value that we can use later to test for high
-        * water marks.
-        */
+      tcb->adj_stack_ptr  = (uint32_t*)top_of_stack;
+      tcb->adj_stack_size = size_of_stack;
+
+      /* If stack debug is enabled, then fill the stack with a
+       * recognizable value that we can use later to test for high
+       * water marks.
+       */
 
 #if defined(CONFIG_DEBUG) && defined(CONFIG_DEBUG_STACK)
-       memset32(tcb->stack_alloc_ptr, 0xDEADBEEF, tcb->adj_stack_size/4);
+      memset32(tcb->stack_alloc_ptr, 0xDEADBEEF, tcb->adj_stack_size/4);
 #endif
 
-       up_ledon(LED_STACKCREATED);
-       return OK;
-     }
+      up_ledon(LED_STACKCREATED);
+      return OK;
+    }
 
    return ERROR;
 }
diff --git a/nuttx/arch/arm/src/common/up_usestack.c b/nuttx/arch/arm/src/common/up_usestack.c
index 822f05168..f46be0cc9 100644
--- a/nuttx/arch/arm/src/common/up_usestack.c
+++ b/nuttx/arch/arm/src/common/up_usestack.c
@@ -50,6 +50,33 @@
 #include "up_internal.h"
 
 /****************************************************************************
+ * Pre-processor Macros
+ ****************************************************************************/
+
+/* ARM requires at least a 4-byte stack alignment.  For use with EABI and
+ * floating point, the stack must be aligned to 8-byte addresses.
+ */
+
+#ifndef CONFIG_STACK_ALIGNMENT
+
+/* The symbol  __ARM_EABI__ is defined by GCC if EABI is being used.  If you
+ * are not using GCC, make sure that CONFIG_STACK_ALIGNMENT is set correctly!
+ */
+
+#  ifdef __ARM_EABI__
+#    define CONFIG_STACK_ALIGNMENT 8
+#  else
+#    define CONFIG_STACK_ALIGNMENT 4
+#  endif
+#endif
+
+/* Stack alignment macros */
+
+#define STACK_ALIGN_MASK    (CONFIG_STACK_ALIGNMENT-1)
+#define STACK_ALIGN_DOWN(a) ((a) & ~STACK_ALIGN_MASK)
+#define STACK_ALIGN_UP(a)   (((a) + STACK_ALIGN_MASK) & ~STACK_ALIGN_MASK)
+
+/****************************************************************************
  * Private Types
  ****************************************************************************/
 
@@ -96,21 +123,27 @@ int up_use_stack(_TCB *tcb, void *stack, size_t stack_size)
 
   tcb->stack_alloc_ptr = stack;
 
-  /* The ARM uses a push-down stack:  the stack grows
-   * toward loweraddresses in memory.  The stack pointer
-   * register, points to the lowest, valid work address
-   * (the "top" of the stack).  Items on the stack are
+  /* The ARM uses a push-down stack:  the stack grows toward lower addresses
+   * in memory.  The stack pointer register, points to the lowest, valid
+   * work address (the "top" of the stack).  Items on the stack are
    * referenced as positive word offsets from sp.
    */
 
   top_of_stack = (uint32_t)tcb->stack_alloc_ptr + stack_size - 4;
 
-  /* The ARM stack must be aligned at word (4 byte)
-   * boundaries. If necessary top_of_stack must be rounded
-   * down to the next boundary
+  /* The ARM stack must be aligned; 4 byte alignment for OABI and 8-byte
+   * alignment for EABI. If necessary top_of_stack must be rounded down
+   * to the next boundary
+   */
+
+  top_of_stack = STACK_ALIGN_DOWN(top_of_stack);
+
+  /* The size of the stack in bytes is then the difference between
+   * the top and the bottom of the stack (+4 because if the top
+   * is the same as the bottom, then the size is one 32-bit element).
+   * The size need not be aligned.
    */
 
-  top_of_stack &= ~3;
   size_of_stack = top_of_stack - (uint32_t)tcb->stack_alloc_ptr + 4;
 
   /* Save the adjusted stack values in the _TCB */
diff --git a/nuttx/configs/README.txt b/nuttx/configs/README.txt
index f19fa28ee..46b41d1ab 100644
--- a/nuttx/configs/README.txt
+++ b/nuttx/configs/README.txt
@@ -1148,7 +1148,11 @@ defconfig -- This is a configuration file similar to the Linux
 		  but copy themselves entirely into RAM for better performance.
 		CONFIG_BOOT_RAMFUNCS - Other configurations may copy just some functions
 		  into RAM, either for better performance or for errata workarounds.
-		CONFIG_STACK_POINTER - The initial stack pointer
+		CONFIG_STACK_POINTER - The initial stack pointer (may not be supported
+		  in all architectures).
+		CONFIG_STACK_ALIGNMENT - Set if the your application has specific
+		  stack alignment requirements (may not be supported
+		  in all architectures).
 		CONFIG_IDLETHREAD_STACKSIZE - The size of the initial stack.
 		  This is the thread that (1) performs the inital boot of the system up
 		  to the point where user_start() is spawned, and (2) there after is the