Add the initial implementation of the process kernel stack logic. Not yet integrated into the main OS logic nor tested.

1 files changed, 15 insertions, 0 deletions

diff --git a/nuttx/include/nuttx/addrenv.h b/nuttx/include/nuttx/addrenv.h
index ac5dce56e..77c7463a6 100644
--- a/nuttx/include/nuttx/addrenv.h
+++ b/nuttx/include/nuttx/addrenv.h
@@ -303,6 +303,21 @@ struct addrenv_reserve_s
  *   up_addrenv_vustack      - Returns the virtual base address of the stack
  *   up_addrenv_ustackselect - Instantiate a stack address environment
  *
+ * If CONFIG_ARCH_KERNEL_STACK is selected, then each user process will have
+ * two stacks:  (1) a large (and possibly dynamic) user stack and (2) a
+ * smaller kernel stack.  However, this option is *required* if both
+ * CONFIG_BUILD_KERNEL and CONFIG_LIBC_EXECFUNCS are selected.  Why?  Because
+ * when we instantiate and initialize the address environment of the new
+ * user process, we will temporarily lose the address environment of the old
+ * user process, including its stack contents.  The kernel C logic will crash
+ * immediately with no valid stack in place.
+ *
+ * If CONFIG_ARCH_STACK_DYNAMIC=y is selected then the platform specific
+ * code must export these additional interfaces:
+ *
+ *   up_addrenv_kstackalloc  - Create a stack in the kernel address environment
+ *   up_addrenv_kstackfree   - Destroy the kernel stack.
+ *
  ****************************************************************************/
 
 /* Prototyped in include/nuttx/arch.h as part of the OS/platform interface */