Modify interrupt handling for privileged/unprivileged mode

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@3480 42af7a65-404d-4744-a932-0658087f49c3

2 files changed, 114 insertions, 0 deletions

diff --git a/nuttx/arch/arm/src/cortexm3/exc_return.h b/nuttx/arch/arm/src/cortexm3/exc_return.h
new file mode 100644
index 000000000..06c0e723f
--- /dev/null
+++ b/nuttx/arch/arm/src/cortexm3/exc_return.h
@@ -0,0 +1,90 @@
+/************************************************************************************
+ * arch/arm/src/cortexm3/exc_return.h
+ *
+ *   Copyright (C) 2011 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name NuttX nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ************************************************************************************/
+
+#ifndef __ARCH_ARM_SRC_COMMON_CORTEXM_EXC_RETURN_H
+#define __ARCH_ARM_SRC_COMMON_CORTEXM_EXC_RETURN_H
+
+/************************************************************************************
+ * Included Files
+ ************************************************************************************/
+
+#include <nuttx/config.h>
+
+/************************************************************************************
+ * Pre-processor Definitions
+ ************************************************************************************/
+
+/* The processor saves an EXC_RETURN value to the LR on exception entry. The
+ * exception mechanism relies on this value to detect when the processor has
+ * completed an exception handler. Bits[31:4] of an EXC_RETURN value are
+ * 0xfffffffX. When the processor loads a value matching this pattern to the
+ * PC it detects that the operation is a not a normal branch operation and,
+ * instead, that the exception is complete. Therefore, it starts the exception
+ * return sequence. Bits[3:0] of the EXC_RETURN value indicate the required
+ * return stack and processor mode:
+ */
+
+/* EXC_RETURN_HANDLER: Return to handler mode. Exception return gets state from
+ * the main stack. Execution uses MSP after return.
+ */
+
+#define EXC_RETURN_HANDLER   0xfffffff1
+
+/* EXC_RETURN_PRIVTHR: Return to privileged thread mode. Exception return gets
+ * state from the main stack. Execution uses MSP after return.
+ */
+
+#define EXC_RETURN_PRIVTHR   0xfffffff9
+
+/* EXC_RETURN_UNPRIVTHR: Return to unprivileged thread mode. Exception return gets
+ * state from the process stack. Execution uses PSP after return.
+ */
+
+#define EXC_RETURN_UNPRIVTHR 0xfffffffd
+
+/* In the kernel build is not selected, then all threads run in privileged thread
+ * mode.
+ */
+
+#ifdef CONFIG_NUTTX_KERNEL
+#  define EXC_RETURN         0xfffffff9
+#endif
+
+/************************Th************************************************************
+ * Inline Functions
+ ************************************************************************************/
+
+#endif  /* __ARCH_ARM_SRC_COMMON_CORTEXM_EXC_RETURN_H */
+
diff --git a/nuttx/arch/arm/src/cortexm3/up_initialstate.c b/nuttx/arch/arm/src/cortexm3/up_initialstate.c
index 40f98bf8c..094a3adba 100644
--- a/nuttx/arch/arm/src/cortexm3/up_initialstate.c
+++ b/nuttx/arch/arm/src/cortexm3/up_initialstate.c
@@ -47,7 +47,9 @@
 
 #include "up_internal.h"
 #include "up_arch.h"
+
 #include "psr.h"
+#include "exc_return.h"
 
 /****************************************************************************
  * Pre-processor Definitions
@@ -124,6 +126,28 @@ void up_initial_state(_TCB *tcb)
 #endif
 #endif
 
+  /* Set privileged- or unprivileged-mode, depending on how NuttX is
+   * configured and what kind of thread is being started.
+   *
+   * If the kernel build is not selected, then all threads run in
+   * privileged thread mode.
+   */
+
+#ifdef CONFIG_NUTTX_KERNEL
+  if ((tcb->flags & TCB_FLAG_TTYPE_MASK) == TCB_FLAG_TTYPE_KERNEL)
+    {
+      /* It is a kernel thread.. set privileged thread mode */
+
+      xcp->regs[REG_EXC_RETURN] = EXC_RETURN_PRIVTHR;
+    }
+  else
+    {
+      /* It is a normal task or a pthread.  Set user mode */
+
+      xcp->regs[REG_EXC_RETURN] = EXC_RETURN_UNPRIVTHR;
+    }
+#endif
+
   /* Enable or disable interrupts, based on user configuration */
 
 # ifdef CONFIG_SUPPRESS_INTERRUPTS