2007-11-02 Joel Sherrill <joel.sherrill@OARcorp.com>

* score/cpu/sparc/cpu.c, score/cpu/sparc/rtems/score/cpu.h,
	score/include/rtems/score/context.h, score/src/threadhandler.c: Fix
	stack so gdb backtrace does not print corrupted frame message after
	_Thread_Handler. Daniel Hellstrom <daniel@gaisler.com> provided the
	SPARC implementation and I made it more general.

cpukit/ChangeLog

@@ -1,3 +1,11 @@
+2007-11-02	Joel Sherrill <joel.sherrill@OARcorp.com>
+
+	* score/cpu/sparc/cpu.c, score/cpu/sparc/rtems/score/cpu.h,
+	score/include/rtems/score/context.h, score/src/threadhandler.c: Fix
+	stack so gdb backtrace does not print corrupted frame message after
+	_Thread_Handler. Daniel Hellstrom <daniel@gaisler.com> provided the
+	SPARC implementation and I made it more general.
+
 2007-10-26	Glenn Humphrey <glenn.humphrey@OARcorp.com>
 
 	* libmisc/cpuuse/cpuusagereport.c, rtems/src/ratemonreportstatistics.c:

cpukit/score/cpu/sparc/cpu.c

@@ -1,7 +1,7 @@
 /*
  *  SPARC Dependent Source
  *
- *  COPYRIGHT (c) 1989-1999.
+ *  COPYRIGHT (c) 1989-2007.
  *  On-Line Applications Research Corporation (OAR).
  *
  *  The license and distribution terms for this file may be
@@ -301,7 +301,7 @@ void _CPU_Context_Initialize(
  
     the_context->o7    = ((uint32_t  ) entry_point) - 8;
     the_context->o6_sp = stack_high - CPU_MINIMUM_STACK_FRAME_SIZE;
-    the_context->i6_fp = stack_high;
+    the_context->i6_fp = 0;
 
     /*
      *  Build the PSR for the task.  Most everything can be 0 and the

cpukit/score/cpu/sparc/rtems/score/cpu.h

@@ -790,6 +790,25 @@ void _CPU_Context_Initialize(
   boolean           is_fp
 );
 
+/*
+ *  This macro is invoked from _Thread_Handler to do whatever CPU
+ *  specific magic is required that must be done in the context of
+ *  the thread when it starts.
+ *
+ *  On the SPARC, this is setting the frame pointer so GDB is happy.
+ *  Make GDB stop unwinding at _Thread_Handler, previous register window
+ *  Frame pointer is 0 and calling address must be a function with starting
+ *  with a SAVE instruction. If return address is leaf-function (no SAVE) 
+ *  GDB will not look at prev reg window fp.
+ *
+ *  _Thread_Handler is known to start with SAVE.
+ */
+
+#define _CPU_Context_Initialization_at_thread_begin() \
+  do { \
+    asm volatile ("set _Thread_Handler,%%i7\n"::); \
+  } while (0)
+
 /*
  *  This routine is responsible for somehow restarting the currently
  *  executing task.  

cpukit/score/include/rtems/score/context.h

@@ -68,6 +68,22 @@ SCORE_EXTERN volatile boolean _Context_Switch_necessary;
 #define _Context_Initialize(_the_context, _stack, _size, _isr, _entry, _is_fp) \
    _CPU_Context_Initialize( _the_context, _stack, _size, _isr, _entry, _is_fp )
 
+/**
+ *  This macro is invoked from _Thread_Handler to do whatever CPU
+ *  specific magic is required that must be done in the context of
+ *  the thread when it starts.
+ *
+ *  If the CPU architecture does not require any magic, then this
+ *  macro is empty.
+ */
+
+#if defined(_CPU_Context_Initialization_at_thread_begin)
+  #define _Context_Initialization_at_thread_begin() \
+     _CPU_Context_Initialization_at_thread_begin()
+#else
+  #define _Context_Initialization_at_thread_begin()
+#endif
+
 /**
  *  @brief Perform Context Switch
  *

cpukit/score/src/threadhandler.c

@@ -75,6 +75,13 @@ void _Thread_Handler( void )
 
   executing = _Thread_Executing;
 
+  /*
+   * Some CPUs need to tinker with the call frame or registers when the 
+   * thread actually begins to execute for the first time.  This is a
+   * hook point where the port gets a shot at doing whatever it requires.
+   */
+  _Context_Initialization_at_thread_begin();
+
   /*
    * have to put level into a register for those cpu's that use
    * inline asm here