Incorporate address environment interfaces in binfmt/ logic

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@5443 42af7a65-404d-4744-a932-0658087f49c3

30 files changed, 1225 insertions, 104 deletions

diff --git a/apps/examples/nxflat/Makefile b/apps/examples/nxflat/Makefile
index 344ee9c6d..94092bd39 100644
--- a/apps/examples/nxflat/Makefile
+++ b/apps/examples/nxflat/Makefile
@@ -76,7 +76,7 @@ $(COBJS): %$(OBJEXT): %.c
 headers:
 	@$(MAKE) -C tests TOPDIR="$(TOPDIR)" APPDIR="$(APPDIR)" CROSSDEV=$(CROSSDEV)
 
-.built: $(OBJS)
+.built: headers $(OBJS)
 	$(call ARCHIVE, $(BIN), $(OBJS))
 	@touch .built
 
diff --git a/nuttx/ChangeLog b/nuttx/ChangeLog
index c932a1f2d..1296076b6 100644
--- a/nuttx/ChangeLog
+++ b/nuttx/ChangeLog
@@ -3792,3 +3792,10 @@
 	  logic on initial check-in
 	* binfmt/binfmt_loadmodule.c: load_module() will now traverse the PATH
 	  variable to locate files from their relative path.
+	* include/nuttx/arch.h and arch/z80/src/z180/z180_mmu.c:  Restructure the
+	  address environment interfaces so that they will better integrate with
+	  binfmt/.
+	* binfmt/libelf/*, binfmt/libnxflat/* and other files:  Integrate the
+	  address environment interfaces.  If CONFIG_ADDRENV=y, then binfmt/
+	  will now create an address environment for new tasks (instead of
+	  just malloc'ing the task memory).
diff --git a/nuttx/Documentation/NuttxPortingGuide.html b/nuttx/Documentation/NuttxPortingGuide.html
index 526892d3e..0408f82ac 100644
--- a/nuttx/Documentation/NuttxPortingGuide.html
+++ b/nuttx/Documentation/NuttxPortingGuide.html
@@ -2130,7 +2130,7 @@ else
     <p>
       <b>Binary Loader Support</b>.
       These are low-level interfaces used in <code>binfmt/</code> to instantiate tasks with address environments.
-      These interfaces all operate on type <code>task_addrenv_t</code> which is an abstract representation of a asks's address environment and must be defined in arch/arch.h if <code>CONFIG_ADDRENVM</code> is defined.
+      These interfaces all operate on type <code>task_addrenv_t</code> which is an abstract representation of a asks's address environment and must be defined in arch/arch.h if <code>CONFIG_ADDRENV</code> is defined.
       These low-level interfaces include:
     </p>
     <ul>
@@ -2174,7 +2174,7 @@ else
       </li>
       <li>
         <a href="#up_addrenv_release">4.1.21.8 <code>up_addrenv_release()</code></a>:
-        ARelease the TCBs reference to an address environment when a task/thread exits.
+        Release the TCB's reference to an address environment when a task/thread exits.
       </li>
     </ul>
   </li>
@@ -3930,7 +3930,9 @@ void (*notify)(FAR struct pm_callback_s *cb, enum pm_state_e pmstate);
      up_prioritize_irq() API.</li>
   <li><code>CONFIG_ADDRENV</code>:
      The CPU supports an MMU and CPU port supports provision of address
-     environments for tasks (making the, perhaps, processes).</li>
+     environments for tasks (making the, perhaps, processes).
+     In this case, the CPU-specific logic must provide a set of address environment interfaces as defined in the <a href="#addrenv">Address Environments</a> paragraph.
+     </li>
 </ul>
 
 <p>
diff --git a/nuttx/arch/arm/src/lm3s/lm3s_ssi.c b/nuttx/arch/arm/src/lm3s/lm3s_ssi.c
index c756e2b6a..8d1987992 100644
--- a/nuttx/arch/arm/src/lm3s/lm3s_ssi.c
+++ b/nuttx/arch/arm/src/lm3s/lm3s_ssi.c
@@ -209,8 +209,11 @@ static inline void ssi_putreg(struct lm3s_ssidev_s *priv, unsigned int offset,
 
 static uint32_t ssi_disable(struct lm3s_ssidev_s *priv);
 static void ssi_enable(struct lm3s_ssidev_s *priv, uint32_t enable);
+
+#ifndef CONFIG_SSI_POLLWAIT
 static void ssi_semtake(sem_t *sem);
 #define ssi_semgive(s) sem_post(s);
+#endif
 
 /* SSI data transfer */
 
@@ -446,6 +449,7 @@ static void ssi_enable(struct lm3s_ssidev_s *priv, uint32_t enable)
  *
  ****************************************************************************/
 
+#ifndef CONFIG_SSI_POLLWAIT
 static void ssi_semtake(sem_t *sem)
 {
   int ret;
@@ -456,6 +460,7 @@ static void ssi_semtake(sem_t *sem)
   while (ret < 0 && errno == EINTR);
   DEBUGASSERT(ret == 0);
 }
+#endif
 
 /****************************************************************************
  * Name: ssi_txnull, ssi_txuint16, and ssi_txuint8
diff --git a/nuttx/binfmt/binfmt_dumpmodule.c b/nuttx/binfmt/binfmt_dumpmodule.c
index cd52136b0..d320bc830 100644
--- a/nuttx/binfmt/binfmt_dumpmodule.c
+++ b/nuttx/binfmt/binfmt_dumpmodule.c
@@ -96,6 +96,9 @@ int dump_module(FAR const struct binary_s *bin)
       bdbg("  ctors:     %p nctors=%d\n", bin->ctors, bin->nctors);
       bdbg("  dtors:     %p ndtors=%d\n", bin->dtors, bin->ndtors);
 #endif
+#ifdef CONFIG_ADDRENV
+      bdbg("  addrenv:   %p\n", bin->addrenv);
+#endif
       bdbg("  stacksize: %d\n", bin->stacksize);
     }
   return OK;
diff --git a/nuttx/binfmt/binfmt_execmodule.c b/nuttx/binfmt/binfmt_execmodule.c
index 37f445966..400451c40 100644
--- a/nuttx/binfmt/binfmt_execmodule.c
+++ b/nuttx/binfmt/binfmt_execmodule.c
@@ -86,11 +86,26 @@
  ****************************************************************************/
 
 #ifdef CONFIG_BINFMT_CONSTRUCTORS
-static inline void exec_ctors(FAR const struct binary_s *binp)
+static inline int exec_ctors(FAR const struct binary_s *binp)
 {
   binfmt_ctor_t *ctor = binp->ctors;
+#ifdef CONFIG_ADDRENV
+  hw_addrenv_t oldenv;
+  int ret;
+#endif
   int i;
 
+  /* Instantiate the address enviroment containing the constructors */
+
+#ifdef CONFIG_ADDRENV
+  ret = up_addrenv_select(binp->addrenv, &oldenv);
+  if (ret < 0)
+    {
+      bdbg("up_addrenv_select() failed: %d\n", ret);
+      return ret;
+    }
+#endif
+
   /* Execute each constructor */
 
   for (i = 0; i < binp->nctors; i++)
@@ -100,6 +115,14 @@ static inline void exec_ctors(FAR const struct binary_s *binp)
       (*ctor)();
       ctor++;
     }
+
+  /* Restore the address enviroment */
+
+#ifdef CONFIG_ADDRENV
+  return up_addrenv_restore(oldenv);
+#else
+  return OK;
+#endif
 }
 #endif
 
@@ -190,6 +213,18 @@ int exec_module(FAR const struct binary_s *binp, int priority)
   up_initial_state(tcb);
 #endif
 
+  /* Assign the address environment to the task */
+
+#ifdef CONFIG_ADDRENV
+  ret = up_addrenv_assign(binp->addrenv, tcb);
+  if (ret < 0)
+    {
+      err = -ret;
+      bdbg("up_addrenv_assign() failed: %d\n", ret);
+      goto errout_with_stack;
+    }
+#endif
+
   /* Get the assigned pid before we start the task */
 
   pid = tcb->pid;
@@ -197,7 +232,13 @@ int exec_module(FAR const struct binary_s *binp, int priority)
   /* Execute all of the C++ static constructors */
 
 #ifdef CONFIG_BINFMT_CONSTRUCTORS
-  exec_ctors(binp);
+  ret = exec_ctors(binp);
+  if (ret < 0)
+    {
+      err = -ret;
+      bdbg("exec_ctors() failed: %d\n", ret);
+      goto errout_with_stack;
+    }
 #endif
 
   /* Then activate the task at the provided priority */
diff --git a/nuttx/binfmt/binfmt_unloadmodule.c b/nuttx/binfmt/binfmt_unloadmodule.c
index 52243fcf7..a0050481c 100644
--- a/nuttx/binfmt/binfmt_unloadmodule.c
+++ b/nuttx/binfmt/binfmt_unloadmodule.c
@@ -86,8 +86,23 @@
 static inline void exec_dtors(FAR const struct binary_s *binp)
 {
   binfmt_dtor_t *dtor = binp->dtors;
+#ifdef CONFIG_ADDRENV
+  hw_addrenv_t oldenv;
+  int ret;
+#endif
   int i;
 
+  /* Instantiate the address enviroment containing the destructors */
+
+#ifdef CONFIG_ADDRENV
+  ret = up_addrenv_select(binp->addrenv, &oldenv);
+  if (ret < 0)
+    {
+      bdbg("up_addrenv_select() failed: %d\n", ret);
+      return ret;
+    }
+#endif
+
   /* Execute each destructor */
 
   for (i = 0; i < binp->ndtors; i++)
@@ -97,6 +112,14 @@ static inline void exec_dtors(FAR const struct binary_s *binp)
       (*dtor)();
       dtor++;
     }
+
+  /* Restore the address enviroment */
+
+#ifdef CONFIG_ADDRENV
+  return up_addrenv_restore(oldenv);
+#else
+  return OK;
+#endif
 }
 #endif
 
@@ -125,15 +148,23 @@ static inline void exec_dtors(FAR const struct binary_s *binp)
 
 int unload_module(FAR const struct binary_s *binp)
 {
+#ifdef CONFIG_BINFMT_CONSTRUCTORS
+  int ret;
+#endif
   int i;
  
   if (binp)
     {
-
       /* Execute C++ desctructors */
 
 #ifdef CONFIG_BINFMT_CONSTRUCTORS
-      exec_dtors(binp);
+      ret = exec_dtors(binp);
+      if (ret < 0)
+        {
+          bdbg("exec_ctors() failed: %d\n", ret);
+          set_errno(-ret);
+          return ERROR;
+        }
 #endif
 
       /* Unmap mapped address spaces */
@@ -155,6 +186,10 @@ int unload_module(FAR const struct binary_s *binp)
               free(binp->alloc[i]);
             }
         }
+
+      /* Notice that the address environment is not destroyed.  This should
+       * happen automatically when the task exits.
+       */
     }
 
   return OK;
diff --git a/nuttx/binfmt/elf.c b/nuttx/binfmt/elf.c
index ea1e7b0ca..bcebf13ca 100644
--- a/nuttx/binfmt/elf.c
+++ b/nuttx/binfmt/elf.c
@@ -215,9 +215,22 @@ static int elf_loadbinary(struct binary_s *binp)
   /* Return the load information */
 
   binp->entrypt   = (main_t)(loadinfo.elfalloc + loadinfo.ehdr.e_entry);
-  binp->alloc[0]  = (FAR void *)loadinfo.elfalloc;
   binp->stacksize = CONFIG_ELF_STACKSIZE;
 
+  /* Add the ELF allocation to the alloc[] only if there is no address
+   * enironment.  If there is an address environment, it will automatically
+   * be freed when the function exits
+   *
+   * REVISIT:  If the module is loaded then unloaded, wouldn't this cause
+   * a memory leak?
+   */
+
+#ifdef CONFIG_ADDRENV
+#  warning "REVISIT"
+#else
+  binp->alloc[0]  = (FAR void *)loadinfo.elfalloc;
+#endif
+
 #ifdef CONFIG_BINFMT_CONSTRUCTORS
   /* Save information about constructors.  NOTE:  desctructors are not
    * yet supported.
@@ -232,6 +245,14 @@ static int elf_loadbinary(struct binary_s *binp)
   binp->ndtors    = loadinfo.ndtors;
 #endif
 
+#ifdef CONFIG_ADDRENV
+  /* Save the address environment.  This will be needed when the module is
+   * executed for the up_addrenv_assign() call.
+   */
+
+  binp->addrenv   = loadinfo.addrenv;
+#endif
+
   elf_dumpbuffer("Entry code", (FAR const uint8_t*)binp->entrypt,
                  MIN(loadinfo.allocsize - loadinfo.ehdr.e_entry, 512));
 
diff --git a/nuttx/binfmt/libelf/Make.defs b/nuttx/binfmt/libelf/Make.defs
index c8857c3f7..93d95a23c 100644
--- a/nuttx/binfmt/libelf/Make.defs
+++ b/nuttx/binfmt/libelf/Make.defs
@@ -41,9 +41,9 @@ BINFMT_CSRCS += elf.c
 
 # ELF library
 
-BINFMT_CSRCS += libelf_bind.c libelf_init.c libelf_iobuffer.c libelf_load.c \
-			    libelf_read.c libelf_sections.c libelf_symbols.c libelf_uninit.c \
-			    libelf_unload.c libelf_verify.c
+BINFMT_CSRCS += libelf_bind.c libelf_init.c libelf_addrenv.c libelf_iobuffer.c 
+BINFMT_CSRCS += libelf_load.c libelf_read.c libelf_sections.c libelf_symbols.c
+BINFMT_CSRCS += libelf_uninit.c libelf_unload.c libelf_verify.c
 
 ifeq ($(CONFIG_BINFMT_CONSTRUCTORS),y)
 BINFMT_CSRCS += libelf_ctors.c libelf_dtors.c
diff --git a/nuttx/binfmt/libelf/libelf.h b/nuttx/binfmt/libelf/libelf.h
index 5b0be9ab0..04c9144f6 100644
--- a/nuttx/binfmt/libelf/libelf.h
+++ b/nuttx/binfmt/libelf/libelf.h
@@ -45,6 +45,7 @@
 #include <sys/types.h>
 #include <elf32.h>
 
+#include <nuttx/arch.h>
 #include <nuttx/binfmt/elf.h>
 
 /****************************************************************************
@@ -74,7 +75,11 @@ int elf_verifyheader(FAR const Elf32_Ehdr *header);
  * Name: elf_read
  *
  * Description:
- *   Read 'readsize' bytes from the object file at 'offset'
+ *   Read 'readsize' bytes from the object file at 'offset'.  The data is
+ *   read into 'buffer.' If 'buffer' is part of the ELF address environment,
+ *   then the caller is responsibile for assuring that that address
+ *   environment is in place before calling this function (i.e., that
+ *   elf_addrenv_select() has been called if CONFIG_ADDRENV=y).
  *
  * Returned Value:
  *   0 (OK) is returned on success and a negated errno is returned on
@@ -255,4 +260,82 @@ int elf_loadctors(FAR struct elf_loadinfo_s *loadinfo);
 int elf_loaddtors(FAR struct elf_loadinfo_s *loadinfo);
 #endif
 
+/****************************************************************************
+ * Name: elf_addrenv_alloc
+ *
+ * Description:
+ *   Allocate memory for the ELF image (elfalloc). If CONFIG_ADDRENV=n,
+ *   elfalloc will be allocated using kzalloc().  If CONFIG_ADDRENV-y, then
+ *   elfalloc will be allocated using up_addrenv_create().  In either case,
+ *   there will be a unique instance of elfalloc (and stack) for each
+ *   instance of a process.
+ *
+ * Input Parameters:
+ *   loadinfo - Load state information
+ *   envsize - The size (in bytes) of the address environment needed for the
+ *     ELF image.
+ *
+ * Returned Value:
+ *   Zero (OK) on success; a negated errno value on failure.
+ *
+ ****************************************************************************/
+
+int elf_addrenv_alloc(FAR struct elf_loadinfo_s *loadinfo, size_t envsize);
+
+/****************************************************************************
+ * Name: elf_addrenv_select
+ *
+ * Description:
+ *   Temporarity select the task's address environemnt.
+ *
+ * Input Parameters:
+ *   loadinfo - Load state information
+ *
+ * Returned Value:
+ *   Zero (OK) on success; a negated errno value on failure.
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_ADDRENV
+#  define elf_addrenv_select(l) up_addrenv_select((l)->addrenv, &(l)->oldenv)
+#endif
+
+/****************************************************************************
+ * Name: elf_addrenv_restore
+ *
+ * Description:
+ *   Restore the address environment before elf_addrenv_select() was called..
+ *
+ * Input Parameters:
+ *   loadinfo - Load state information
+ *
+ * Returned Value:
+ *   Zero (OK) on success; a negated errno value on failure.
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_ADDRENV
+#  define elf_addrenv_restore(l) up_addrenv_restore((l)->oldenv)
+#endif
+
+/****************************************************************************
+ * Name: elf_addrenv_free
+ *
+ * Description:
+ *   Release the address environment previously created by
+ *   elf_addrenv_alloc().  This function  is called only under certain error
+ *   conditions after the the module has been loaded but not yet started.
+ *   After the module has been started, the address environment will
+ *   automatically be freed when the module exits.
+ *
+ * Input Parameters:
+ *   loadinfo - Load state information
+ *
+ * Returned Value:
+ *   None.
+ *
+ ****************************************************************************/
+
+void elf_addrenv_free(FAR struct elf_loadinfo_s *loadinfo);
+
 #endif /* __BINFMT_LIBELF_LIBELF_H */
diff --git a/nuttx/binfmt/libelf/libelf_addrenv.c b/nuttx/binfmt/libelf/libelf_addrenv.c
new file mode 100644
index 000000000..28cc0e108
--- /dev/null
+++ b/nuttx/binfmt/libelf/libelf_addrenv.c
@@ -0,0 +1,176 @@
+/****************************************************************************
+ * binfmt/libelf/libelf_addrenv.c
+ *
+ *   Copyright (C) 2012 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <gnutt@nuttx.org>
+ *
+ * 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.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <errno.h>
+#include <debug.h>
+
+#include <nuttx/arch.h>
+#include <nuttx/kmalloc.h>
+
+#include "libelf.h"
+
+/****************************************************************************
+ * Pre-Processor Definitions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Constant Data
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: elf_addrenv_create
+ *
+ * Description:
+ *   Allocate memory for the ELF image (elfalloc). If CONFIG_ADDRENV=n,
+ *   elfalloc will be allocated using kzalloc().  If CONFIG_ADDRENV-y, then
+ *   elfalloc will be allocated using up_addrenv_create().  In either case,
+ *   there will be a unique instance of elfalloc (and stack) for each
+ *   instance of a process.
+ *
+ * Input Parameters:
+ *   loadinfo - Load state information
+ *   envsize - The size (in bytes) of the address environment needed for the
+ *     ELF image.
+ *
+ * Returned Value:
+ *   Zero (OK) on success; a negated errno value on failure.
+ *
+ ****************************************************************************/
+
+int elf_addrenv_create(FAR struct elf_loadinfo_s *loadinfo, size_t envsize)
+{
+#ifdef CONFIG_ADDRENV
+  FAR void *vaddr;
+  int ret;
+
+  /* Create an address environment for the new ELF task */
+
+  ret = up_addrenv_create(envsize, &loadinfo->addrenv);
+  if (ret < 0)
+    {
+      bdbg("ERROR: up_addrenv_create failed: %d\n", ret);
+      return ret;
+    }
+
+  /* Get the virtual address associated with the start of the address
+   * environment.  This is the base address that we will need to use to
+   * access the ELF image (but only if the address environment has been
+   * selected.
+   */
+
+  ret = up_addrenv_vaddr(loadinfo->addrenv, &vaddr);
+  if (ret < 0)
+    {
+      bdbg("ERROR: up_addrenv_vaddr failed: %d\n", ret);
+      return ret;
+    }
+
+  loadinfo->elfalloc = (uintptr_t)vaddr;
+  return OK;
+#else
+  /* Allocate memory to hold the ELF image */
+
+  loadinfo->elfalloc = (uintptr_t)kzalloc(envsize);
+  if (!loadinfo->elfalloc)
+    {
+      return -ENOMEM;
+    }
+
+  return OK;
+#endif
+}
+
+/****************************************************************************
+ * Name: elf_addrenv_free
+ *
+ * Description:
+ *   Release the address environment previously created by
+ *   elf_addrenv_create().  This function  is called only under certain error
+ *   conditions after the the module has been loaded but not yet started.
+ *   After the module has been started, the address environment will
+ *   automatically be freed when the module exits.
+ *
+ * Input Parameters:
+ *   loadinfo - Load state information
+ *
+ * Returned Value:
+ *   None.
+ *
+ ****************************************************************************/
+
+void elf_addrenv_free(FAR struct elf_loadinfo_s *loadinfo)
+{
+#ifdef CONFIG_ADDRENV
+  int ret;
+
+  /* Free the address environemnt */
+
+  ret = up_addrenv_destroy(loadinfo->addrenv);
+  if (ret < 0)
+    {
+      bdbg("ERROR: up_addrenv_destroy failed: %d\n", ret);
+    }
+
+  /* Clear out all indications of the allocated address environment */
+
+  loadinfo->elfalloc = 0;
+  loadinfo->elfsize  = 0;
+  loadinfo->addrenv  = 0;
+#else
+  /* If there is an allocation for the ELF image, free it */
+
+  if (loadinfo->elfalloc != 0)
+    {
+      kfree((FAR void *)loadinfo->elfalloc);
+      loadinfo->elfalloc = 0;
+    }
+
+   loadinfo->elfsize = 0;
+#endif
+}
diff --git a/nuttx/binfmt/libelf/libelf_bind.c b/nuttx/binfmt/libelf/libelf_bind.c
index e35087b1d..ccdb5108e 100644
--- a/nuttx/binfmt/libelf/libelf_bind.c
+++ b/nuttx/binfmt/libelf/libelf_bind.c
@@ -86,10 +86,10 @@
  ****************************************************************************/
 
 /****************************************************************************
- * Name: elf_readsym
+ * Name: elf_readrel
  *
  * Description:
- *   Read the ELFT symbol structure at the specfied index into memory.
+ *   Read the ELF32_Rel structure into memory.
  *
  ****************************************************************************/
 
@@ -184,7 +184,7 @@ static int elf_relocate(FAR struct elf_loadinfo_s *loadinfo, int relidx,
           return ret;
         }
 
-      /* Calculate the relocation address */
+      /* Calculate the relocation address. */
 
       if (rel.r_offset < 0 || rel.r_offset > dstsec->sh_size - sizeof(uint32_t))
         {
@@ -195,14 +195,42 @@ static int elf_relocate(FAR struct elf_loadinfo_s *loadinfo, int relidx,
 
       addr = dstsec->sh_addr + rel.r_offset;
 
+      /* If CONFIG_ADDRENV=y, then 'addr' lies in a virtual address space that
+       * may not be in place now.  elf_addrenv_select() will temporarily
+       * instantiate that address space.
+       */
+
+#ifdef CONFIG_ADDRENV
+      ret = elf_addrenv_select(loadinfo);
+      if (ret < 0)
+        {
+          bdbg("ERROR: elf_addrenv_select() failed: %d\n", ret);
+          return ret;
+        }
+#endif
+
       /* Now perform the architecture-specific relocation */
 
       ret = arch_relocate(&rel, &sym, addr);
       if (ret < 0)
         {
-          bdbg("Section %d reloc %d: Relocation failed: %d\n", ret);
+#ifdef CONFIG_ADDRENV
+          (void)elf_addrenv_restore(loadinfo);
+#endif
+          bdbg("ERROR: Section %d reloc %d: Relocation failed: %d\n", ret);
+          return ret;
+        }
+
+      /* Restore the original address environment */
+
+#ifdef CONFIG_ADDRENV
+      ret = elf_addrenv_restore(loadinfo);
+      if (ret < 0)
+        {
+          bdbg("ERROR: elf_addrenv_restore() failed: %d\n", ret);
           return ret;
         }
+#endif
     }
 
   return OK;
diff --git a/nuttx/binfmt/libelf/libelf_load.c b/nuttx/binfmt/libelf/libelf_load.c
index b1ac44e21..0e4ad9798 100644
--- a/nuttx/binfmt/libelf/libelf_load.c
+++ b/nuttx/binfmt/libelf/libelf_load.c
@@ -49,7 +49,6 @@
 #include <errno.h>
 #include <debug.h>
 
-#include <nuttx/kmalloc.h>
 #include <nuttx/binfmt/elf.h>
 
 #include "libelf.h"
@@ -135,11 +134,12 @@ static inline int elf_loadfile(FAR struct elf_loadinfo_s *loadinfo)
   int i;
 
   /* Allocate (and zero) memory for the ELF file. */
-  
-  loadinfo->elfalloc = (uintptr_t)kzalloc(loadinfo->elfsize);
-  if (!loadinfo->elfalloc)
+
+  ret = elf_addrenv_alloc(loadinfo, loadinfo->elfsize);
+  if (ret < 0)
     {
-      return -ENOMEM;
+      bdbg("ERROR: elf_addrenv_alloc() failed: %d\n", ret);
+      return ret;
     }
 
   /* Read each section into memory that is marked SHF_ALLOC + SHT_NOBITS */
@@ -165,6 +165,20 @@ static inline int elf_loadfile(FAR struct elf_loadinfo_s *loadinfo)
 
       if (shdr->sh_type != SHT_NOBITS)
         {
+          /* If CONFIG_ADDRENV=y, then 'dest' lies in a virtual address space
+           * that may not be in place now.  elf_addrenv_select() will
+           * temporarily instantiate that address space.
+           */
+
+#ifdef CONFIG_ADDRENV
+          ret = elf_addrenv_select(loadinfo);
+          if (ret < 0)
+            {
+              bdbg("ERROR: elf_addrenv_select() failed: %d\n", ret);
+              return ret;
+            }
+#endif
+
           /* Read the section data from sh_offset to dest */
 
           ret = elf_read(loadinfo, dest, shdr->sh_size, shdr->sh_offset);
@@ -173,6 +187,17 @@ static inline int elf_loadfile(FAR struct elf_loadinfo_s *loadinfo)
               bdbg("Failed to read section %d: %d\n", i, ret);
               return ret;
             }
+
+          /* Restore the original address environment */
+
+#ifdef CONFIG_ADDRENV
+          ret = elf_addrenv_restore(loadinfo);
+          if (ret < 0)
+            {
+              bdbg("ERROR: elf_addrenv_restore() failed: %d\n", ret);
+             return ret;
+            }
+#endif
         }
 
       /* Update sh_addr to point to copy in memory */
diff --git a/nuttx/binfmt/libelf/libelf_read.c b/nuttx/binfmt/libelf/libelf_read.c
index da41212f2..f4b725183 100644
--- a/nuttx/binfmt/libelf/libelf_read.c
+++ b/nuttx/binfmt/libelf/libelf_read.c
@@ -98,7 +98,11 @@ static inline void elf_dumpreaddata(char *buffer, int buflen)
  * Name: elf_read
  *
  * Description:
- *   Read 'readsize' bytes from the object file at 'offset'
+ *   Read 'readsize' bytes from the object file at 'offset'.  The data is
+ *   read into 'buffer.' If 'buffer' is part of the ELF address environment,
+ *   then the caller is responsibile for assuring that that address
+ *   environment is in place before calling this function (i.e., that
+ *   elf_addrenv_select() has been called if CONFIG_ADDRENV=y).
  *
  * Returned Value:
  *   0 (OK) is returned on success and a negated errno is returned on
diff --git a/nuttx/binfmt/libelf/libelf_unload.c b/nuttx/binfmt/libelf/libelf_unload.c
index 532fc606f..539e5faf7 100644
--- a/nuttx/binfmt/libelf/libelf_unload.c
+++ b/nuttx/binfmt/libelf/libelf_unload.c
@@ -67,8 +67,9 @@
  * Name: elf_unload
  *
  * Description:
- *   This function unloads the object from memory. This essentially
- *   undoes the actions of elf_load.
+ *   This function unloads the object from memory. This essentially undoes
+ *   the actions of elf_load.  It is called only under certain error
+ *   conditions after the the module has been loaded but not yet started.
  *
  * Returned Value:
  *   0 (OK) is returned on success and a negated errno is returned on
@@ -84,13 +85,7 @@ int elf_unload(struct elf_loadinfo_s *loadinfo)
 
   /* Release memory holding the relocated ELF image */
 
-  if (loadinfo->elfalloc != 0)
-    {
-      kfree((FAR void *)loadinfo->elfalloc);
-      loadinfo->elfalloc = 0;
-    }
-
-   loadinfo->elfsize = 0;
+  elf_addrenv_free(loadinfo);
  
    /* Release memory used to hold static constructors and destructors */
 
diff --git a/nuttx/binfmt/libnxflat/Make.defs b/nuttx/binfmt/libnxflat/Make.defs
index 4f522e52b..6a0bf1873 100644
--- a/nuttx/binfmt/libnxflat/Make.defs
+++ b/nuttx/binfmt/libnxflat/Make.defs
@@ -41,9 +41,9 @@ BINFMT_CSRCS += nxflat.c
 
 # NXFLAT library
 
-BINFMT_CSRCS += libnxflat_init.c libnxflat_uninit.c libnxflat_load.c \
-			   libnxflat_unload.c libnxflat_verify.c libnxflat_read.c \
-			   libnxflat_bind.c
+BINFMT_CSRCS += libnxflat_init.c libnxflat_uninit.c libnxflat_addrenv.c
+BINFMT_CSRCS += libnxflat_load.c libnxflat_unload.c libnxflat_verify.c
+BINFMT_CSRCS += libnxflat_read.c libnxflat_bind.c
 
 # Hook the libnxflat subdirectory into the build
 
diff --git a/nuttx/binfmt/libnxflat/libnxflat.h b/nuttx/binfmt/libnxflat/libnxflat.h
new file mode 100644
index 000000000..cb1cb7057
--- /dev/null
+++ b/nuttx/binfmt/libnxflat/libnxflat.h
@@ -0,0 +1,136 @@
+/****************************************************************************
+ * binfmt/libnxflat/libnxflat.h
+ *
+ *   Copyright (C) 2012 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <gnutt@nuttx.org>
+ *
+ * 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 __BINFMT_LIBNXFLAT_LIBNXFLAT_H
+#define __BINFMT_LIBNXFLAT_LIBNXFLAT_H
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <sys/types.h>
+
+#include <nuttx/arch.h>
+#include <nuttx/binfmt/nxflat.h>
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Public Types
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: nxflat_addrenv_alloc
+ *
+ * Description:
+ *   Allocate memory for the ELF image (elfalloc). If CONFIG_ADDRENV=n,
+ *   elfalloc will be allocated using kzalloc().  If CONFIG_ADDRENV-y, then
+ *   elfalloc will be allocated using up_addrenv_create().  In either case,
+ *   there will be a unique instance of elfalloc (and stack) for each
+ *   instance of a process.
+ *
+ * Input Parameters:
+ *   loadinfo - Load state information
+ *   envsize - The size (in bytes) of the address environment needed for the
+ *     ELF image.
+ *
+ * Returned Value:
+ *   Zero (OK) on success; a negated errno value on failure.
+ *
+ ****************************************************************************/
+
+int nxflat_addrenv_alloc(FAR struct nxflat_loadinfo_s *loadinfo, size_t envsize);
+
+/****************************************************************************
+ * Name: nxflat_addrenv_select
+ *
+ * Description:
+ *   Temporarity select the task's address environemnt.
+ *
+ * Input Parameters:
+ *   loadinfo - Load state information
+ *
+ * Returned Value:
+ *   Zero (OK) on success; a negated errno value on failure.
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_ADDRENV
+#  define nxflat_addrenv_select(l) up_addrenv_select((l)->addrenv, &(l)->oldenv)
+#endif
+
+/****************************************************************************
+ * Name: nxflat_addrenv_restore
+ *
+ * Description:
+ *   Restore the address environment before nxflat_addrenv_select() was called..
+ *
+ * Input Parameters:
+ *   loadinfo - Load state information
+ *
+ * Returned Value:
+ *   Zero (OK) on success; a negated errno value on failure.
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_ADDRENV
+#  define nxflat_addrenv_restore(l) up_addrenv_restore((l)->oldenv)
+#endif
+
+/****************************************************************************
+ * Name: nxflat_addrenv_free
+ *
+ * Description:
+ *   Release the address environment previously created by
+ *   nxflat_addrenv_create().  This function  is called only under certain
+ *   error conditions after the the module has been loaded but not yet
+ *   started. After the module has been started, the address environment
+ *   will automatically be freed when the module exits.
+ *
+ * Input Parameters:
+ *   loadinfo - Load state information
+ *
+ * Returned Value:
+ *   None.
+ *
+ ****************************************************************************/
+
+void nxflat_addrenv_free(FAR struct nxflat_loadinfo_s *loadinfo);
+
+#endif /* __BINFMT_LIBNXFLAT_LIBNXFLAT_H */
diff --git a/nuttx/binfmt/libnxflat/libnxflat_addrenv.c b/nuttx/binfmt/libnxflat/libnxflat_addrenv.c
new file mode 100644
index 000000000..c6b3fce34
--- /dev/null
+++ b/nuttx/binfmt/libnxflat/libnxflat_addrenv.c
@@ -0,0 +1,234 @@
+/****************************************************************************
+ * binfmt/libnxflat/libnxflat_addrenv.c
+ *
+ *   Copyright (C) 2012 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <gnutt@nuttx.org>
+ *
+ * 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.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <errno.h>
+#include <debug.h>
+
+#include <nuttx/arch.h>
+#include <nuttx/kmalloc.h>
+
+#include "libnxflat.h"
+
+/****************************************************************************
+ * Pre-Processor Definitions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Constant Data
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: nxflat_addrenv_create
+ *
+ * Description:
+ *   Allocate memory for the ELF image (elfalloc). If CONFIG_ADDRENV=n,
+ *   elfalloc will be allocated using kzalloc().  If CONFIG_ADDRENV-y, then
+ *   elfalloc will be allocated using up_addrenv_create().  In either case,
+ *   there will be a unique instance of elfalloc (and stack) for each
+ *   instance of a process.
+ *
+ * Input Parameters:
+ *   loadinfo - Load state information
+ *   envsize - The size (in bytes) of the address environment needed for the
+ *     ELF image.
+ *
+ * Returned Value:
+ *   Zero (OK) on success; a negated errno value on failure.
+ *
+ ****************************************************************************/
+
+int nxflat_addrenv_create(FAR struct nxflat_loadinfo_s *loadinfo, size_t envsize)
+{
+  FAR struct dspace_s *dspace;
+#ifdef CONFIG_ADDRENV
+  FAR void *vaddr;
+  hw_addrenv_t oldenv;
+  int ret;
+#endif
+
+  DEBUGASSERT(!loadinfo->dspace);
+
+  /* Allocate the struct dspace_s container for the D-Space allocation */
+
+  dspace = (FAR struct dspace_s *)kmalloc(sizeof(struct dspace_s));
+  if (dspace == 0)
+    {
+      bdbg("ERROR: Failed to allocate DSpace\n");
+      return -ENOMEM;
+    }
+
+#ifdef CONFIG_ADDRENV
+  /* Create a D-Space address environment for the new NXFLAT task */
+
+  ret = up_addrenv_create(envsize, &loadinfo->addrenv);
+  if (ret < 0)
+    {
+      bdbg("ERROR: up_addrenv_create failed: %d\n", ret);
+      goto errout_with_dspace;
+    }
+
+  /* Get the virtual address associated with the start of the address
+   * environment.  This is the base address that we will need to use to
+   * access the D-Space region (but only if the address environment has been
+   * selected.
+   */
+
+  ret = up_addrenv_vaddr(loadinfo->addrenv, &vaddr);
+  if (ret < 0)
+    {
+      bdbg("ERROR: up_addrenv_vaddr failed: %d\n", ret);
+      goto errout_with_addrenv;
+    }
+
+  /* Clear all of the allocated D-Space memory.  We have to temporarily
+   * selected the D-Space address environment to do this.
+   */
+
+  ret = up_addrenv_select(loadinfo->addrenv, &oldenv);
+  if (ret < 0)
+    {
+      bdbg("ERROR: up_addrenv_select failed: %d\n", ret);
+      goto errout_with_addrenv;
+    }
+
+  memset(vaddr, 0, envsize);
+
+  ret = up_addrenv_restore(oldenv);
+  if (ret < 0)
+    {
+      bdbg("ERROR: up_addrenv_restore failed: %d\n", ret);
+      goto errout_with_addrenv;
+    }
+
+  /* Success... save the fruits of our labor */
+
+  loadinfo->dspace = dspace;
+  dspace->crefs    = 1;  
+  dspace->region   = (FAR uint8_t *)vaddr;
+  return OK;
+
+errout_with_addrenv:
+  (void)up_addrenv_destroy(loadinfo->addrenv);
+  loadinfo->addrenv = 0;
+
+errout_with_dspace:
+  kfree(dspace);
+  return ret;
+#else
+  /* Allocate (and zero) memory to hold the ELF image */
+
+  dspace->region = (FAR uint8_t *)kzalloc(envsize);
+  if (!dspace->region)
+    {
+      kfree(dspace);
+      return -ENOMEM;
+    }
+
+  loadinfo->dspace = dspace;
+  dspace->crefs    = 1;  
+  return OK;
+#endif
+}
+
+/****************************************************************************
+ * Name: nxflat_addrenv_free
+ *
+ * Description:
+ *   Release the address environment previously created by
+ *   nxflat_addrenv_create().  This function  is called only under certain
+ *   error conditions after the the module has been loaded but not yet
+ *   started. After the module has been started, the address environment
+ *   will automatically be freed when the module exits.
+ *
+ * Input Parameters:
+ *   loadinfo - Load state information
+ *
+ * Returned Value:
+ *   None.
+ *
+ ****************************************************************************/
+
+void nxflat_addrenv_free(FAR struct nxflat_loadinfo_s *loadinfo)
+{
+  FAR struct dspace_s *dspace;
+#ifdef CONFIG_ADDRENV
+  int ret;
+#endif
+
+  DEBUGASSERT(loadinfo);
+  dspace = loadinfo->dspace;
+
+  if (dspace)
+    {
+#ifdef CONFIG_ADDRENV
+      /* Destroy the address environment */
+
+      ret = up_addrenv_destroy(loadinfo->addrenv);
+      if (ret < 0)
+        {
+          bdbg("ERROR: up_addrenv_destroy failed: %d\n", ret);
+        }
+
+      loadinfo->addrenv = 0;
+#else
+      /* Free the allocated D-Space region */
+
+      if (dspace->region)
+        {
+          kfree(dspace->region);
+        }
+#endif
+
+      /* Now destroy the D-Space container */
+
+      DEBUGASSERT(dspace->crefs == 1);
+      kfree(dspace);
+      loadinfo->dspace = NULL;
+    }
+}
diff --git a/nuttx/binfmt/libnxflat/libnxflat_bind.c b/nuttx/binfmt/libnxflat/libnxflat_bind.c
index 2b9f64715..3a86d5355 100644
--- a/nuttx/binfmt/libnxflat/libnxflat_bind.c
+++ b/nuttx/binfmt/libnxflat/libnxflat_bind.c
@@ -47,9 +47,12 @@
 #include <debug.h>
 
 #include <arpa/inet.h>
+
 #include <nuttx/binfmt/nxflat.h>
 #include <nuttx/binfmt/symtab.h>
 
+#include "libnxflat.h"
+
 /****************************************************************************
  * Pre-processor Definitions
  ****************************************************************************/
@@ -229,8 +232,6 @@ static inline int nxflat_gotrelocs(FAR struct nxflat_loadinfo_s *loadinfo)
 
   hdr = (FAR struct nxflat_hdr_s*)loadinfo->ispace;
 
-  /* From this, we can get the list of relocation entries. */
-
   /* From this, we can get the offset to the list of relocation entries */
 
   offset  = ntohl(hdr->h_relocstart);
@@ -252,6 +253,22 @@ static inline int nxflat_gotrelocs(FAR struct nxflat_loadinfo_s *loadinfo)
   bvdbg("isize: %08lx dpsace: %p relocs: %p\n", 
         (long)loadinfo->isize, loadinfo->dspace->region, relocs);
 
+  /* All relocations are performed within the D-Space allocation.  If
+   * CONFIG_ADDRENV=y, then that D-Space allocation lies in an address
+   * environment that may not be in place.  So, in that case, we must call
+   * nxflat_addrenv_select to temporarily instantiate that address space
+   * before the relocations can be performed.
+   */
+
+#ifdef CONFIG_ADDRENV
+  ret = nxflat_addrenv_select(loadinfo);
+  if (ret < 0)
+    {
+      bdbg("ERROR: nxflat_addrenv_select() failed: %d\n", ret);
+      return ret;
+    }
+#endif
+
   /* Now, traverse the relocation list of and bind each GOT relocation. */
 
   ret = OK; /* Assume success */
@@ -329,6 +346,16 @@ static inline int nxflat_gotrelocs(FAR struct nxflat_loadinfo_s *loadinfo)
     }
 #endif
 
+  /* Restore the original address environment */
+
+#ifdef CONFIG_ADDRENV
+  ret = nxflat_addrenv_restore(loadinfo);
+  if (ret < 0)
+    {
+      bdbg("ERROR: nxflat_addrenv_restore() failed: %d\n", ret);
+    }
+#endif
+
   return ret;
 }
 
@@ -346,16 +373,19 @@ static inline int nxflat_gotrelocs(FAR struct nxflat_loadinfo_s *loadinfo)
  ****************************************************************************/
 
 static inline int nxflat_bindimports(FAR struct nxflat_loadinfo_s *loadinfo,
-                                       FAR const struct symtab_s *exports,
-                                       int nexports)
+                                     FAR const struct symtab_s *exports,
+                                     int nexports)
 {
   FAR struct nxflat_import_s *imports;
   FAR struct nxflat_hdr_s    *hdr;
-  FAR const struct symtab_s *symbol;
+  FAR const struct symtab_s  *symbol;
 
   char    *symname;
   uint32_t offset;
   uint16_t nimports;
+#ifdef CONFIG_ADDRENV
+  int      ret;
+#endif
   int      i;
 
   /* The NXFLAT header is the first thing at the beginning of the ISpace. */
@@ -370,6 +400,22 @@ static inline int nxflat_bindimports(FAR struct nxflat_loadinfo_s *loadinfo,
   nimports = ntohs(hdr->h_importcount);
   bvdbg("Imports offset: %08x nimports: %d\n", offset, nimports);
 
+  /* The import[] table resides within the D-Space allocation.  If
+   * CONFIG_ADDRENV=y, then that D-Space allocation lies in an address
+   * environment that may not be in place.  So, in that case, we must call
+   * nxflat_addrenv_select to temporarily instantiate that address space
+   * before the import[] table can be modified.
+   */
+
+#ifdef CONFIG_ADDRENV
+  ret = nxflat_addrenv_select(loadinfo);
+  if (ret < 0)
+    {
+      bdbg("ERROR: nxflat_addrenv_select() failed: %d\n", ret);
+      return ret;
+    }
+#endif
+
   /* Verify that this module requires imported symbols */
 
   if (offset != 0 && nimports > 0)
@@ -421,6 +467,9 @@ static inline int nxflat_bindimports(FAR struct nxflat_loadinfo_s *loadinfo,
           if (!symbol)
             {
               bdbg("Exported symbol \"%s\" not found\n", symname);
+#ifdef CONFIG_ADDRENV
+              (void)nxflat_addrenv_restore(loadinfo);
+#endif
               return -ENOENT;
             }
 
@@ -442,7 +491,73 @@ static inline int nxflat_bindimports(FAR struct nxflat_loadinfo_s *loadinfo,
     }
 #endif
 
+  /* Restore the original address environment */
+
+#ifdef CONFIG_ADDRENV
+  ret = nxflat_addrenv_restore(loadinfo);
+  if (ret < 0)
+    {
+      bdbg("ERROR: nxflat_addrenv_restore() failed: %d\n", ret);
+    }
+
+  return ret;
+#else
   return OK;
+#endif
+}
+
+/****************************************************************************
+ * Name: nxflat_clearbss
+ *
+ * Description:
+ *   Clear uninitialized .bss memory
+ *
+ * Returned Value:
+ *   0 (OK) is returned on success and a negated errno is returned on
+ *   failure.
+ *
+ ****************************************************************************/
+
+static inline int nxflat_clearbss(FAR struct nxflat_loadinfo_s *loadinfo)
+{
+#ifdef CONFIG_ADDRENV
+  int ret;
+#endif
+
+  /* .bss resides within the D-Space allocation.  If CONFIG_ADDRENV=y, then
+   * that D-Space allocation lies in an address environment that may not be
+   * in place.  So, in that case, we must call nxflat_addrenv_select to
+   * temporarily instantiate that address space before the .bss can be
+   * accessed.
+   */
+
+#ifdef CONFIG_ADDRENV
+  ret = nxflat_addrenv_select(loadinfo);
+  if (ret < 0)
+    {
+      bdbg("ERROR: nxflat_addrenv_select() failed: %d\n", ret);
+      return ret;
+    }
+#endif
+
+  /* Zero the BSS area */
+
+   memset((void*)(loadinfo->dspace->region + loadinfo->datasize), 0,
+          loadinfo->bsssize);
+
+  /* Restore the original address environment */
+
+#ifdef CONFIG_ADDRENV
+  ret = nxflat_addrenv_restore(loadinfo);
+  if (ret < 0)
+    {
+      bdbg("ERROR: nxflat_addrenv_restore() failed: %d\n", ret);
+    }
+
+  return ret;
+#else
+  return OK;
+#endif
 }
 
 /****************************************************************************
@@ -484,8 +599,7 @@ int nxflat_bind(FAR struct nxflat_loadinfo_s *loadinfo,
            * space in the loaded file.
            */
 
-          memset((void*)(loadinfo->dspace->region + loadinfo->datasize),
-                      0, loadinfo->bsssize);
+          ret = nxflat_clearbss(loadinfo);
         }
     }
 
diff --git a/nuttx/binfmt/libnxflat/libnxflat_load.c b/nuttx/binfmt/libnxflat/libnxflat_load.c
index b6693ea36..5f13b577a 100644
--- a/nuttx/binfmt/libnxflat/libnxflat_load.c
+++ b/nuttx/binfmt/libnxflat/libnxflat_load.c
@@ -41,6 +41,7 @@
 
 #include <sys/types.h>
 #include <sys/mman.h>
+
 #include <stdint.h>
 #include <stdlib.h>
 #include <nxflat.h>
@@ -48,8 +49,11 @@
 #include <errno.h>
 
 #include <arpa/inet.h>
+
 #include <nuttx/binfmt/nxflat.h>
 
+#include "libnxflat.h"
+
 /****************************************************************************
  * Pre-Processor Definitions
  ****************************************************************************/
@@ -143,7 +147,7 @@ int nxflat_load(struct nxflat_loadinfo_s *loadinfo)
    */
 
   loadinfo->ispace = (uint32_t)mmap(NULL, loadinfo->isize, PROT_READ,
-                                  MAP_SHARED|MAP_FILE, loadinfo->filfd, 0);
+                                    MAP_SHARED|MAP_FILE, loadinfo->filfd, 0);
   if (loadinfo->ispace == (uint32_t)MAP_FAILED)
     {
       bdbg("Failed to map NXFLAT ISpace: %d\n", errno);
@@ -152,23 +156,37 @@ int nxflat_load(struct nxflat_loadinfo_s *loadinfo)
 
   bvdbg("Mapped ISpace (%d bytes) at %08x\n", loadinfo->isize, loadinfo->ispace);
 
-  /* The following call will give a pointer to the allocated but
-   * uninitialized ISpace memory.
+  /* The following call allocate D-Space memory and will provide a pointer
+   * to the allocated (but still uninitialized) D-Space memory.
    */
 
-  loadinfo->dspace = (struct dspace_s *)malloc(SIZEOF_DSPACE_S(loadinfo->dsize));
-  if (loadinfo->dspace == 0)
+  ret = nxflat_addrenv_alloc(loadinfo, loadinfo->dsize);
+  if (ret < 0)
     {
-      bdbg("Failed to allocate DSpace\n");
-      ret = -ENOMEM;
-      goto errout;
+      bdbg("ERROR: nxflat_addrenv_alloc() failed: %d\n", ret);
+      return ret;
     }
-  loadinfo->dspace->crefs = 1;
 
-  bvdbg("Allocated DSpace (%d bytes) at %p\n", loadinfo->dsize, loadinfo->dspace->region);
+  bvdbg("Allocated DSpace (%d bytes) at %p\n",
+        loadinfo->dsize, loadinfo->dspace->region);
 
-  /* Now, read the data into allocated DSpace at doffset into the
-   * allocated DSpace memory.
+  /* If CONFIG_ADDRENV=y, then the D-Space allocation lies in an address
+   * environment that may not be in place.  So, in that case, we must call
+   * nxflat_addrenv_select to temporarily instantiate that address space
+   * it can be initialized.
+   */
+
+#ifdef CONFIG_ADDRENV
+  ret = nxflat_addrenv_select(loadinfo);
+  if (ret < 0)
+    {
+      bdbg("ERROR: nxflat_addrenv_select() failed: %d\n", ret);
+      return ret;
+    }
+#endif
+
+  /* Now, read the data into allocated DSpace at doffset into the allocated
+   * DSpace memory.
    */
 
   ret = nxflat_read(loadinfo, (char*)loadinfo->dspace->region, dreadsize, doffset);
@@ -181,9 +199,23 @@ int nxflat_load(struct nxflat_loadinfo_s *loadinfo)
   bvdbg("TEXT: %08x Entry point offset: %08x Data offset: %08x\n",
       loadinfo->ispace, loadinfo->entryoffs, doffset);
 
+  /* Restore the original address environment */
+
+#ifdef CONFIG_ADDRENV
+  ret = nxflat_addrenv_restore(loadinfo);
+  if (ret < 0)
+    {
+      bdbg("ERROR: nxflat_addrenv_restore() failed: %d\n", ret);
+      return ret;
+    }
+#endif
+
   return OK;
 
 errout:
+#ifdef CONFIG_ADDRENV
+  (void)nxflat_addrenv_restore(loadinfo);
+#endif
   (void)nxflat_unload(loadinfo);
   return ret;
 }
diff --git a/nuttx/binfmt/libnxflat/libnxflat_unload.c b/nuttx/binfmt/libnxflat/libnxflat_unload.c
index 47c30bd55..71d0c8499 100644
--- a/nuttx/binfmt/libnxflat/libnxflat_unload.c
+++ b/nuttx/binfmt/libnxflat/libnxflat_unload.c
@@ -40,11 +40,15 @@
 #include <nuttx/config.h>
 
 #include <sys/mman.h>
+
 #include <stdlib.h>
 #include <debug.h>
 
+#include <nuttx/kmalloc.h>
 #include <nuttx/binfmt/nxflat.h>
 
+#include "libnxflat.h"
+
 /****************************************************************************
  * Pre-Processor Definitions
  ****************************************************************************/
@@ -65,8 +69,9 @@
  * Name: nxflat_unload
  *
  * Description:
- *   This function unloads the object from memory. This essentially
- *   undoes the actions of nxflat_load.
+ *   This function unloads the object from memory. This essentially undoes
+ *   the actions of nxflat_load.  It is called only under certain error
+ *   conditions after the the module has been loaded but not yet started.
  *
  * Returned Value:
  *   0 (OK) is returned on success and a negated errno is returned on
@@ -76,9 +81,8 @@
 
 int nxflat_unload(struct nxflat_loadinfo_s *loadinfo)
 {
-  /* Reset the contents of the info structure. */
-
   /* Release the memory segments */
+  /* Release the I-Space mmap'ed file */
 
   if (loadinfo->ispace)
     {
@@ -86,12 +90,9 @@ int nxflat_unload(struct nxflat_loadinfo_s *loadinfo)
       loadinfo->ispace = 0;
     }
 
-  if (loadinfo->dspace)
-    {
-      free((void*)loadinfo->dspace);
-      loadinfo->dspace = 0;
-    }
+  /* Release the D-Space address environment */
 
+  nxflat_addrenv_free(loadinfo);
   return OK;
 }
 
diff --git a/nuttx/binfmt/nxflat.c b/nuttx/binfmt/nxflat.c
index 5973a96a9..db29941ca 100644
--- a/nuttx/binfmt/nxflat.c
+++ b/nuttx/binfmt/nxflat.c
@@ -187,10 +187,31 @@ static int nxflat_loadbinary(struct binary_s *binp)
 
   binp->entrypt   = (main_t)(loadinfo.ispace + loadinfo.entryoffs);
   binp->mapped    = (void*)loadinfo.ispace;
-  binp->alloc[0]  = (void*)loadinfo.dspace;
   binp->mapsize   = loadinfo.isize;
   binp->stacksize = loadinfo.stacksize;
 
+  /* Add the ELF allocation to the alloc[] only if there is no address
+   * enironment.  If there is an address environment, it will automatically
+   * be freed when the function exits
+   *
+   * REVISIT:  If the module is loaded then unloaded, wouldn't this cause
+   * a memory leak?
+   */
+
+#ifdef CONFIG_ADDRENV
+#  warning "REVISIT"
+#else
+  binp->alloc[0]  = (void*)loadinfo.dspace;
+#endif
+
+#ifdef CONFIG_ADDRENV
+  /* Save the address environment.  This will be needed when the module is
+   * executed for the up_addrenv_assign() call.
+   */
+
+  binp->addrenv   = loadinfo.addrenv;
+#endif
+
   nxflat_dumpbuffer("Entry code", (FAR const uint8_t*)binp->entrypt,
                     MIN(loadinfo.isize - loadinfo.entryoffs, 512));
 
diff --git a/nuttx/configs/eagle100/httpd/setenv.sh b/nuttx/configs/eagle100/httpd/setenv.sh
index 9022695a4..d22bf6f91 100755
--- a/nuttx/configs/eagle100/httpd/setenv.sh
+++ b/nuttx/configs/eagle100/httpd/setenv.sh
@@ -32,15 +32,31 @@
 # POSSIBILITY OF SUCH DAMAGE.
 #
 
-if [ "$(basename $0)" = "setenv.sh" ] ; then
+if [ "$_" = "$0" ] ; then
   echo "You must source this script, not run it!" 1>&2
   exit 1
 fi
 
-if [ -z "${PATH_ORIG}" ]; then export PATH_ORIG="${PATH}"; fi
-
 WD=`pwd`
-export BUILDROOT_BIN="${WD}/../misc/buildroot/build_arm_nofpu/staging_dir/bin"
-export PATH="${BUILDROOT_BIN}:/sbin:/usr/sbin:${PATH_ORIG}"
+if [ ! -x "setenv.sh" ]; then
+  echo "This script must be executed from the top-level NuttX build directory"
+  exit 1
+fi
+
+if [ -z "${PATH_ORIG}" ]; then
+  export PATH_ORIG="${PATH}"
+fi
+
+# This is the Cygwin path to the location where I installed the CodeSourcery
+# toolchain under windows.  You will also have to edit this if you install
+# the CodeSourcery toolchain in any other location
+export TOOLCHAIN_BIN="/cygdrive/c/Program Files (x86)/CodeSourcery/Sourcery G++ Lite/bin"
+
+# This is the Cygwin path to the location where I build the buildroot
+# toolchain.
+#export TOOLCHAIN_BIN="${WD}/../misc/buildroot/build_arm_nofpu/staging_dir/bin"
+
+# Add the path to the toolchain to the PATH varialble
+export PATH="${TOOLCHAIN_BIN}:/sbin:/usr/sbin:${PATH_ORIG}"
 
 echo "PATH : ${PATH}"
diff --git a/nuttx/configs/eagle100/nettest/setenv.sh b/nuttx/configs/eagle100/nettest/setenv.sh
index f03beff85..37cc7735c 100755
--- a/nuttx/configs/eagle100/nettest/setenv.sh
+++ b/nuttx/configs/eagle100/nettest/setenv.sh
@@ -32,15 +32,31 @@
 # POSSIBILITY OF SUCH DAMAGE.
 #
 
-if [ "$(basename $0)" = "setenv.sh" ] ; then
+if [ "$_" = "$0" ] ; then
   echo "You must source this script, not run it!" 1>&2
   exit 1
 fi
 
-if [ -z "${PATH_ORIG}" ]; then export PATH_ORIG="${PATH}"; fi
-
 WD=`pwd`
-export BUILDROOT_BIN="${WD}/../misc/buildroot/build_arm_nofpu/staging_dir/bin"
-export PATH="${BUILDROOT_BIN}:/sbin:/usr/sbin:${PATH_ORIG}"
+if [ ! -x "setenv.sh" ]; then
+  echo "This script must be executed from the top-level NuttX build directory"
+  exit 1
+fi
+
+if [ -z "${PATH_ORIG}" ]; then
+  export PATH_ORIG="${PATH}"
+fi
+
+# This is the Cygwin path to the location where I installed the CodeSourcery
+# toolchain under windows.  You will also have to edit this if you install
+# the CodeSourcery toolchain in any other location
+export TOOLCHAIN_BIN="/cygdrive/c/Program Files (x86)/CodeSourcery/Sourcery G++ Lite/bin"
+
+# This is the Cygwin path to the location where I build the buildroot
+# toolchain.
+#export TOOLCHAIN_BIN="${WD}/../misc/buildroot/build_arm_nofpu/staging_dir/bin"
+
+# Add the path to the toolchain to the PATH varialble
+export PATH="${TOOLCHAIN_BIN}:/sbin:/usr/sbin:${PATH_ORIG}"
 
 echo "PATH : ${PATH}"
diff --git a/nuttx/configs/eagle100/nsh/setenv.sh b/nuttx/configs/eagle100/nsh/setenv.sh
index c64bfed54..cd8710503 100755
--- a/nuttx/configs/eagle100/nsh/setenv.sh
+++ b/nuttx/configs/eagle100/nsh/setenv.sh
@@ -32,15 +32,31 @@
 # POSSIBILITY OF SUCH DAMAGE.
 #
 
-if [ "$(basename $0)" = "setenv.sh" ] ; then
+if [ "$_" = "$0" ] ; then
   echo "You must source this script, not run it!" 1>&2
   exit 1
 fi
 
-if [ -z "${PATH_ORIG}" ]; then export PATH_ORIG="${PATH}"; fi
-
 WD=`pwd`
-export BUILDROOT_BIN="${WD}/../misc/buildroot/build_arm_nofpu/staging_dir/bin"
-export PATH="${BUILDROOT_BIN}:/sbin:/usr/sbin:${PATH_ORIG}"
+if [ ! -x "setenv.sh" ]; then
+  echo "This script must be executed from the top-level NuttX build directory"
+  exit 1
+fi
+
+if [ -z "${PATH_ORIG}" ]; then
+  export PATH_ORIG="${PATH}"
+fi
+
+# This is the Cygwin path to the location where I installed the CodeSourcery
+# toolchain under windows.  You will also have to edit this if you install
+# the CodeSourcery toolchain in any other location
+export TOOLCHAIN_BIN="/cygdrive/c/Program Files (x86)/CodeSourcery/Sourcery G++ Lite/bin"
+
+# This is the Cygwin path to the location where I build the buildroot
+# toolchain.
+#export TOOLCHAIN_BIN="${WD}/../misc/buildroot/build_arm_nofpu/staging_dir/bin"
+
+# Add the path to the toolchain to the PATH varialble
+export PATH="${TOOLCHAIN_BIN}:/sbin:/usr/sbin:${PATH_ORIG}"
 
 echo "PATH : ${PATH}"
diff --git a/nuttx/configs/eagle100/nxflat/setenv.sh b/nuttx/configs/eagle100/nxflat/setenv.sh
index 2335de190..771be4ec6 100755
--- a/nuttx/configs/eagle100/nxflat/setenv.sh
+++ b/nuttx/configs/eagle100/nxflat/setenv.sh
@@ -32,15 +32,31 @@
 # POSSIBILITY OF SUCH DAMAGE.
 #
 
-if [ "$(basename $0)" = "setenv.sh" ] ; then
+if [ "$_" = "$0" ] ; then
   echo "You must source this script, not run it!" 1>&2
   exit 1
 fi
 
-if [ -z "${PATH_ORIG}" ]; then export PATH_ORIG="${PATH}"; fi
-
 WD=`pwd`
-export BUILDROOT_BIN="${WD}/../misc/buildroot/build_arm_nofpu/staging_dir/bin"
-export PATH="${BUILDROOT_BIN}:/sbin:/usr/sbin:${PATH_ORIG}"
+if [ ! -x "setenv.sh" ]; then
+  echo "This script must be executed from the top-level NuttX build directory"
+  exit 1
+fi
+
+if [ -z "${PATH_ORIG}" ]; then
+  export PATH_ORIG="${PATH}"
+fi
+
+# This is the Cygwin path to the location where I installed the CodeSourcery
+# toolchain under windows.  You will also have to edit this if you install
+# the CodeSourcery toolchain in any other location
+export TOOLCHAIN_BIN="/cygdrive/c/Program Files (x86)/CodeSourcery/Sourcery G++ Lite/bin"
+
+# This is the Cygwin path to the location where I build the buildroot
+# toolchain.
+#export TOOLCHAIN_BIN="${WD}/../misc/buildroot/build_arm_nofpu/staging_dir/bin"
+
+# Add the path to the toolchain to the PATH varialble
+export PATH="${TOOLCHAIN_BIN}:/sbin:/usr/sbin:${PATH_ORIG}"
 
 echo "PATH : ${PATH}"
diff --git a/nuttx/include/nuttx/binfmt/binfmt.h b/nuttx/include/nuttx/binfmt/binfmt.h
index 2e2c6dda8..6df5190d2 100644
--- a/nuttx/include/nuttx/binfmt/binfmt.h
+++ b/nuttx/include/nuttx/binfmt/binfmt.h
@@ -41,8 +41,11 @@
  ****************************************************************************/
 
 #include <nuttx/config.h>
+
 #include <sys/types.h>
 #include <nxflat.h>
+
+#include <nuttx/arch.h>
 #include <nuttx/sched.h>
 
 /****************************************************************************
@@ -93,12 +96,26 @@ struct binary_s
   main_t entrypt;                      /* Entry point into a program module */
   FAR void *mapped;                    /* Memory-mapped, address space */
   FAR void *alloc[BINFMT_NALLOC];      /* Allocated address spaces */
+
+  /* Constructors/destructors */
+
 #ifdef CONFIG_BINFMT_CONSTRUCTORS
   FAR binfmt_ctor_t *ctors;            /* Pointer to a list of constructors */
   FAR binfmt_dtor_t *dtors;            /* Pointer to a list of destructors */
   uint16_t nctors;                     /* Number of constructors in the list */
   uint16_t ndtors;                     /* Number of destructors in the list */
 #endif
+
+  /* Address environment.
+   *
+   * addrenv - This is the handle created by up_addrenv_create() that can be
+   *   used to manage the tasks address space.
+   */
+
+#ifdef CONFIG_ADDRENV
+  task_addrenv_t addrenv;              /* Task address environment */
+#endif
+
   size_t mapsize;                      /* Size of the mapped address region (needed for munmap) */
   size_t stacksize;                    /* Size of the stack in bytes (unallocated) */
 };
diff --git a/nuttx/include/nuttx/binfmt/elf.h b/nuttx/include/nuttx/binfmt/elf.h
index 432e57f0f..6b6851934 100644
--- a/nuttx/include/nuttx/binfmt/elf.h
+++ b/nuttx/include/nuttx/binfmt/elf.h
@@ -59,6 +59,18 @@
 #  define CONFIG_ELF_ALIGN_LOG2 2
 #endif
 
+#ifndef CONFIG_ELF_STACKSIZE
+#  define CONFIG_ELF_STACKSIZE 2048
+#endif
+
+#ifndef CONFIG_ELF_BUFFERSIZE
+#  define CONFIG_ELF_BUFFERSIZE 128
+#endif
+
+#ifndef CONFIG_ELF_BUFFERINCR
+#  define CONFIG_ELF_BUFFERINCR 32
+#endif
+
 /* Allocation array size and indices */
 
 #define LIBELF_ELF_ALLOC     0
@@ -80,8 +92,16 @@
 
 struct elf_loadinfo_s
 {
-  /* The alloc[] array holds memory that persists after the ELF module has
-   * been loaded.
+  /* elfalloc is the base address of the memory that is allocated to hold the
+   * ELF program image.
+   *
+   * If CONFIG_ADDRENV=n, elfalloc will be allocated using kmalloc() (or
+   * kzalloc()).  If CONFIG_ADDRENV-y, then elfalloc will be allocated using
+   * up_addrenv_create().  In either case, there will be a unique instance
+   * of elfalloc (and stack) for each instance of a process.
+   *
+   * The alloc[] array in struct binary_s will hold memory that persists after
+   * the ELF module has been loaded.
    */
  
   uintptr_t         elfalloc;    /* Memory allocated when ELF file was loaded */
@@ -90,6 +110,9 @@ struct elf_loadinfo_s
   Elf32_Ehdr        ehdr;        /* Buffered ELF file header */
   FAR Elf32_Shdr    *shdr;       /* Buffered ELF section headers */
   uint8_t           *iobuffer;   /* File I/O buffer */
+
+  /* Constructors and destructors */
+  
 #ifdef CONFIG_BINFMT_CONSTRUCTORS
   FAR void          *ctoralloc;  /* Memory allocated for ctors */
   FAR void          *dtoralloc;  /* Memory allocated dtors */
@@ -98,6 +121,20 @@ struct elf_loadinfo_s
   uint16_t           nctors;     /* Number of constructors */
   uint16_t           ndtors;     /* Number of destructors */
 #endif
+
+  /* Address environment.
+   *
+   * addrenv - This is the handle created by up_addrenv_create() that can be
+   *   used to manage the tasks address space.
+   * oldenv  - This is a value returned by up_addrenv_select() that must be 
+   *   used to restore the current hardware address environment.
+   */
+
+#ifdef CONFIG_ADDRENV
+  task_addrenv_t addrenv;  /* Task address environment */
+  hw_addrenv_t   oldenv;   /* Saved hardware address environment */
+#endif
+
   uint16_t           symtabidx;  /* Symbol table section index */
   uint16_t           strtabidx;  /* String table section index */
   uint16_t           buflen;     /* size of iobuffer[] */
@@ -187,8 +224,9 @@ EXTERN int elf_bind(FAR struct elf_loadinfo_s *loadinfo,
  * Name: elf_unload
  *
  * Description:
- *   This function unloads the object from memory. This essentially
- *   undoes the actions of elf_load.
+ *   This function unloads the object from memory. This essentially undoes
+ *   the actions of elf_load.  It is called only under certain error
+ *   conditions after the the module has been loaded but not yet started.
  *
  * Returned Value:
  *   0 (OK) is returned on success and a negated errno is returned on
diff --git a/nuttx/include/nuttx/binfmt/nxflat.h b/nuttx/include/nuttx/binfmt/nxflat.h
index 89e28fbcc..db396771b 100644
--- a/nuttx/include/nuttx/binfmt/nxflat.h
+++ b/nuttx/include/nuttx/binfmt/nxflat.h
@@ -44,7 +44,9 @@
 
 #include <stdint.h>
 #include <nxflat.h>
+
 #include <nuttx/sched.h>
+#include <nuttx/arch.h>
 
 /****************************************************************************
  * Pre-processor Definitions
@@ -61,17 +63,24 @@
 struct nxflat_loadinfo_s
 {
   /* Instruction Space (ISpace):  This region contains the nxflat file header
-   * plus everything from the text section.  Ideally, will have only one mmap'ed
-   * text section instance in the system for each module.
+   * plus everything from the text section.
+   *
+   * The ISpace region is allocated using mmap() and, thus, can be shared by
+   * multiple tasks.  Ideally, will have only one mmap'ed text section
+   * instance in the system for each module.
    */
 
-  uint32_t ispace;         /* Address where hdr/text is loaded */
+  uintptr_t ispace;        /* Address where hdr/text is loaded */
   uint32_t entryoffs;      /* Offset from ispace to entry point */
   uint32_t isize;          /* Size of ispace. */
 
-  /* Data Space (DSpace): This region contains all information that in referenced
-   * as data (other than the stack which is separately allocated).  There will be
-   * a unique instance of DSpace (and stack) for each instance of a process.
+  /* Data Space (DSpace): This region contains all information that is
+   * referenced as data (other than the stack which is separately allocated).
+   *
+   * If CONFIG_ADDRENV=n, DSpace will be allocated using kmalloc() (or
+   * kzalloc()).  If CONFIG_ADDRENV-y, then DSpace will be allocated using
+   * up_addrenv_create().  In either case, there will be a unique instance
+   * of DSpace (and stack) for each instance of a process.
    */
 
   struct dspace_s *dspace; /* Allocated D-Space (data/bss/etc) */
@@ -85,6 +94,19 @@ struct nxflat_loadinfo_s
   uint32_t relocstart;     /* Start of array of struct flat_reloc */
   uint16_t reloccount;     /* Number of elements in reloc array */
 
+  /* Address environment.
+   *
+   * addrenv - This is the handle created by up_addrenv_create() that can be
+   *   used to manage the tasks address space.
+   * oldenv  - This is a value returned by up_addrenv_select() that must be 
+   *   used to restore the current hardware address environment.
+   */
+
+#ifdef CONFIG_ADDRENV
+  task_addrenv_t addrenv;  /* Task address environment */
+  hw_addrenv_t   oldenv;   /* Saved hardware address environment */
+#endif
+
   /* File descriptors */
 
   int    filfd;            /* Descriptor for the file being loaded */
@@ -212,8 +234,9 @@ EXTERN int nxflat_bind(FAR struct nxflat_loadinfo_s *loadinfo,
  * Name: nxflat_unload
  *
  * Description:
- *   This function unloads the object from memory. This essentially
- *   undoes the actions of nxflat_load.
+ *   This function unloads the object from memory. This essentially undoes
+ *   the actions of nxflat_load.  It is called only under certain error
+ *   conditions after the the module has been loaded but not yet started.
  *
  * Returned Value:
  *   0 (OK) is returned on success and a negated errno is returned on
diff --git a/nuttx/include/nuttx/sched.h b/nuttx/include/nuttx/sched.h
index 172f46901..6eaba6e9c 100644
--- a/nuttx/include/nuttx/sched.h
+++ b/nuttx/include/nuttx/sched.h
@@ -163,24 +163,40 @@ typedef struct environ_s environ_t;
 # define SIZEOF_ENVIRON_T(alloc) (sizeof(environ_t) + alloc - 1)
 #endif
 
-/* This structure describes a reference counted D-Space region */
+/* This structure describes a reference counted D-Space region.  This must be a
+ * separately allocated "break-away" structure that can be owned by a task and
+ * any pthreads created by the task.
+ */
 
+#ifdef CONFIG_PIC
 struct dspace_s
 {
-  uint32_t crefs;             /* This is the number of pthreads that shared the
-                               * the same D-Space */
-  uint8_t  region[1];         /* Beginning of the allocated region */
-};
+  /* The life of the structure allocation is determined by this reference
+   * count.  This count is number of threads that shared the the same D-Space.
+   * This includes the parent task as well as any pthreads created by the
+   * parent task or any of its child threads.
+   */
+
+  uint16_t crefs;
 
-#define SIZEOF_DSPACE_S(n) (sizeof(struct dspace_s) - 1 + (n))
+  /* This is the allocated D-Space memory region.  This may be a physical
+   * address allocated with kmalloc(), or it may be virtual address associated
+   * with an address environment (if CONFIG_ADDRENV=y).
+   */
 
-/* This is the task control block (TCB) */
+  FAR uint8_t *region;
+};
+#endif
+
+/* This is the task control block (TCB).  Each task or thread is represented by
+ * a TCB.  The TCB is the heart of the NuttX task-control logic.
+ */
 
 struct _TCB
 {
   /* Fields used to support list management *************************************/
 
-  FAR struct _TCB *flink;                /* link in DQ of TCBs                  */
+  FAR struct _TCB *flink;                /* Doubly linked list                  */
   FAR struct _TCB *blink;
 
   /* Task Management Fields *****************************************************/