From 3649dab9bdd010a43e54fd7cb7ef93beeed1c476 Mon Sep 17 00:00:00 2001
From: Gregory Nutt <gnutt@nuttx.org>
Date: Sun, 14 Sep 2014 11:19:34 -0600
Subject: [PATCH] Initial integration of kernel stack (does not work)

---
 Documentation/NuttxPortingGuide.html      |  5 ++--
 arch/arm/include/armv7-a/irq.h            |  6 ++--
 arch/arm/src/armv7-a/addrenv.h            |  6 ++++
 arch/arm/src/armv7-a/arm_addrenv_kstack.c | 30 ++++++++++++-------
 arch/arm/src/armv7-a/arm_syscall.c        | 35 +++++++++++++++++++++--
 binfmt/binfmt_execmodule.c                | 35 ++++++++++++++++++-----
 include/nuttx/arch.h                      |  6 ++--
 sched/sched/sched_releasetcb.c            | 12 ++++++--
 8 files changed, 105 insertions(+), 30 deletions(-)

diff --git a/Documentation/NuttxPortingGuide.html b/Documentation/NuttxPortingGuide.html
index 0a336ec00f..aa4f3129a6 100644
--- a/Documentation/NuttxPortingGuide.html
+++ b/Documentation/NuttxPortingGuide.html
@@ -3320,18 +3320,19 @@ VxWorks provides the following comparable interface:
 <h3><a name="up_addrenv_kstackalloc">4.4.15 <code>up_addrenv_kstackalloc()</code></a></h3>
 <p><b>Function Prototype</b>:<p>
 <ul>
-  <code>int up_addrenv_kstackalloc(FAR struct tcb_s *tcb, size_t stacksize);</code>
+  <code>int up_addrenv_kstackalloc(FAR struct tcb_s *tcb);</code>
 </ul>
 <p><b>Description</b>:</p>
 <ul>
   <p>
     This function is called when a new thread is created to allocate the new thread's kernel stack.
+    This function may be called for certain terminating threads which have no kernel stack.
+    It must be tolerant of that case.
   </p>
 </ul>
 <p><b>Input Parameters</b>:</p>
 <ul>
   <li><code>tcb</code>: The TCB of the thread that requires the kernel stack.</li>
-  <li><code>stacksize</code>: The size (in bytes) of the kernel stack needed by the thread.</li>
 </ul>
 <p><b>Returned Value</b>:</p>
 <ul>
diff --git a/arch/arm/include/armv7-a/irq.h b/arch/arm/include/armv7-a/irq.h
index 46303c0160..3813e919a5 100755
--- a/arch/arm/include/armv7-a/irq.h
+++ b/arch/arm/include/armv7-a/irq.h
@@ -276,7 +276,7 @@ struct xcptcontext
 
 #ifdef CONFIG_ARCH_ADDRENV
 #ifdef CONFIG_ARCH_STACK_DYNAMIC
-  /* This table holds the physical address of the level 2 page table used
+  /* This array holds the physical address of the level 2 page table used
    * to map the thread's stack memory.  This array will be initially of
    * zeroed and would be back-up up with pages during page fault exception
    * handling to support dynamically sized stacks for each thread.
@@ -284,6 +284,7 @@ struct xcptcontext
 
   FAR uintptr_t *ustack[ARCH_STACK_NSECTS];
 #endif
+
 #ifdef CONFIG_ARCH_KERNEL_STACK
   /* In this configuration, all syscalls execute from an internal kernel
    * stack.  Why?  Because when we instantiate and initialize the address
@@ -293,7 +294,8 @@ struct xcptcontext
    * stack in place.
    */
 
-  FAR uint32_t *kstack;
+  FAR uint32_t *ustkptr;  /* Saved user stack pointer */
+  FAR uint32_t *kstack;   /* Allocate base of the (aligned) kernel stack */
 #endif
 #endif
 };
diff --git a/arch/arm/src/armv7-a/addrenv.h b/arch/arm/src/armv7-a/addrenv.h
index 0d830ed06f..60cfb342a4 100644
--- a/arch/arm/src/armv7-a/addrenv.h
+++ b/arch/arm/src/armv7-a/addrenv.h
@@ -51,6 +51,12 @@
  * Pre-processor Definitions
  ****************************************************************************/
 
+/* Aligned size of the kernel stack */
+
+#ifdef CONFIG_ARCH_KERNEL_STACK
+#  define ARCH_KERNEL_STACKSIZE ((CONFIG_ARCH_KERNEL_STACKSIZE + 7) & ~7)
+#endif
+
 /* Using a 4KiB page size, each 1MiB section maps to a PTE containing
  * 256*2KiB entries
  */
diff --git a/arch/arm/src/armv7-a/arm_addrenv_kstack.c b/arch/arm/src/armv7-a/arm_addrenv_kstack.c
index 2102e0ad26..852b03620b 100644
--- a/arch/arm/src/armv7-a/arm_addrenv_kstack.c
+++ b/arch/arm/src/armv7-a/arm_addrenv_kstack.c
@@ -117,6 +117,8 @@
 #include <nuttx/addrenv.h>
 #include <nuttx/arch.h>
 
+#include "addrenv.h"
+
 #if defined(CONFIG_ARCH_ADDRENV) && defined(CONFIG_ARCH_KERNEL_STACK)
 
 /****************************************************************************
@@ -140,27 +142,27 @@
  *
  * Description:
  *   This function is called when a new thread is created to allocate
- *   the new thread's kernel stack.
+ *   the new thread's kernel stack.   This function may be called for certain
+ *   terminating threads which have no kernel stack.  It must be tolerant of
+ *   that case.
  *
  * Input Parameters:
  *   tcb - The TCB of the thread that requires the kernel stack.
- *   stacksize - The size (in bytes) of the kernel stack needed by the
- *     thread.
  *
  * Returned Value:
  *   Zero (OK) on success; a negated errno value on failure.
  *
  ****************************************************************************/
 
-int up_addrenv_kstackalloc(FAR struct tcb_s *tcb, size_t stacksize)
+int up_addrenv_kstackalloc(FAR struct tcb_s *tcb)
 {
-  bvdbg("tcb=%p stacksize=%lu\n", tcb, (unsigned long)stacksize);
+  bvdbg("tcb=%p stacksize=%u\n", tcb, ARCH_KERNEL_STACKSIZE);
 
-  DEBUGASSERT(tcb && tcb->xcp.kstack == 0 && stackize > 0);
+  DEBUGASSERT(tcb && tcb->xcp.kstack == 0);
 
   /* Allocate the kernel stack */
 
-  tcb->xcp.kstack = (FAR uint32_t *)kmm_memalign(8, stacksize);
+  tcb->xcp.kstack = (FAR uint32_t *)kmm_memalign(8, ARCH_KERNEL_STACKSIZE);
   if (!tcb->xcp.kstack)
     {
       bdbg("ERROR: Failed to allocate the kernel stack\n");
@@ -188,12 +190,18 @@ int up_addrenv_kstackalloc(FAR struct tcb_s *tcb, size_t stacksize)
 int up_addrenv_kstackfree(FAR struct tcb_s *tcb)
 {
   bvdbg("tcb=%p\n", tcb);
-  DEBUGASSERT(tcb && tcb->xcp.kstack);
+  DEBUGASSERT(tcb);
 
-  /* Free the kernel stack */
+  /* Does the exiting thread have a kernel stack? */
+
+  if (tcb->xcp.kstack)
+    {
+      /* Yes.. Free the kernel stack */
+
+      kmm_free(tcb->xcp.kstack);
+      tcb->xcp.kstack = NULL;
+    }
 
-  kmm_free(tcb->xcp.kstack);
-  tcb->xcp.kstack = NULL;
   return OK;
 }
 
diff --git a/arch/arm/src/armv7-a/arm_syscall.c b/arch/arm/src/armv7-a/arm_syscall.c
index b5f803402c..9fb46f3882 100644
--- a/arch/arm/src/armv7-a/arm_syscall.c
+++ b/arch/arm/src/armv7-a/arm_syscall.c
@@ -51,6 +51,7 @@
 
 #include "arm.h"
 #include "svcall.h"
+#include "addrenv.h"
 #include "up_internal.h"
 
 /****************************************************************************
@@ -219,13 +220,27 @@ uint32_t *arm_syscall(uint32_t *regs)
 #ifdef CONFIG_BUILD_KERNEL
           regs[REG_CPSR]      = rtcb->xcp.syscall[index].cpsr;
 #endif
-          rtcb->xcp.nsyscalls = index;
-
           /* The return value must be in R0-R1.  dispatch_syscall() temporarily
            * moved the value for R0 into R2.
            */
 
           regs[REG_R0]         = regs[REG_R2];
+
+#ifdef CONFIG_ARCH_KERNEL_STACK
+          /* If this is the outermost SYSCALL and if there is a saved user stack
+           * pointer, then restore the user stack pointer on this final return to
+           * user code.
+           */
+
+          if (index == 0 && rtcb->xcp.ustkptr != NULL)
+            {
+              regs[REG_SP]      = (uint32_t)rtcb->xcp.ustkptr;
+              rtcb->xcp.ustkptr = NULL;
+            }
+#endif
+          /* Save the new SYSCALL nesting level */
+
+          rtcb->xcp.nsyscalls = index;
         }
         break;
 
@@ -421,7 +436,6 @@ uint32_t *arm_syscall(uint32_t *regs)
 #ifdef CONFIG_BUILD_KERNEL
           rtcb->xcp.syscall[index].cpsr      = regs[REG_CPSR];
 #endif
-          rtcb->xcp.nsyscalls                = index + 1;
 
           regs[REG_PC]   = (uint32_t)dispatch_syscall;
 #ifdef CONFIG_BUILD_KERNEL
@@ -434,6 +448,21 @@ uint32_t *arm_syscall(uint32_t *regs)
 #else
           svcdbg("ERROR: Bad SYS call: %d\n", regs[REG_R0]);
 #endif
+
+#ifdef CONFIG_ARCH_KERNEL_STACK
+          /* If this is the first SYSCALL and if there is an allocated
+           * kernel stack, then switch to the kernel stack.
+           */
+
+          if (index == 0 && rtcb->xcp.kstack != NULL)
+            {
+              rtcb->xcp.ustkptr = (FAR uint32_t *)regs[REG_SP];
+              regs[REG_SP]      = (uint32_t)rtcb->xcp.kstack + ARCH_KERNEL_STACKSIZE;
+            }
+#endif
+          /* Save the new SYSCALL nesting level */
+
+          rtcb->xcp.nsyscalls   = index + 1;
         }
         break;
     }
diff --git a/binfmt/binfmt_execmodule.c b/binfmt/binfmt_execmodule.c
index baed131bfc..3756fbaf6b 100644
--- a/binfmt/binfmt_execmodule.c
+++ b/binfmt/binfmt_execmodule.c
@@ -165,7 +165,8 @@ int exec_module(FAR const struct binary_s *binp)
       goto errout;
     }
 
-#if defined(CONFIG_ARCH_ADDRENV) && defined(CONFIG_BUILD_KERNEL)
+#ifdef CONFIG_ARCH_ADDRENV
+#ifdef CONFIG_BUILD_KERNEL
   /* Instantiate the address environment containing the user heap */
 
   ret = up_addrenv_select(&binp->addrenv, &oldenv);
@@ -182,6 +183,19 @@ int exec_module(FAR const struct binary_s *binp)
                  up_addrenv_heapsize(&binp->addrenv));
 #endif
 
+#ifdef CONFIG_ARCH_KERNEL_STACK
+  /* Allocate the kernel stack */
+
+  ret = up_addrenv_kstackalloc(&tcb->cmn);
+  if (ret < 0)
+    {
+      bdbg("ERROR: up_addrenv_select() failed: %d\n", ret);
+      err = -ret;
+      goto errout_with_addrenv;
+    }
+#endif
+#endif
+
   /* Allocate the stack for the new task.
    *
    * REVISIT:  This allocation is currently always from the user heap.  That
@@ -192,7 +206,7 @@ int exec_module(FAR const struct binary_s *binp)
   if (!stack)
     {
       err = ENOMEM;
-      goto errout_with_addrenv;
+      goto errout_with_kstack;
     }
 
   /* Initialize the task */
@@ -203,7 +217,7 @@ int exec_module(FAR const struct binary_s *binp)
     {
       err = get_errno();
       bdbg("task_init() failed: %d\n", err);
-      goto errout_with_stack;
+      goto errout_with_kstack;
     }
 
   /* Note that tcb->flags are not modified.  0=normal task */
@@ -229,7 +243,7 @@ int exec_module(FAR const struct binary_s *binp)
     {
       err = -ret;
       bdbg("ERROR: up_addrenv_clone() failed: %d\n", ret);
-      goto errout_with_stack;
+      goto errout_with_tcbinit;
     }
 
   /* Mark that this group has an address environment */
@@ -257,7 +271,7 @@ int exec_module(FAR const struct binary_s *binp)
     {
       err = get_errno();
       bdbg("task_activate() failed: %d\n", err);
-      goto errout_with_stack;
+      goto errout_with_tcbinit;
     }
 
 #if defined(CONFIG_ARCH_ADDRENV) && defined(CONFIG_BUILD_KERNEL)
@@ -268,24 +282,31 @@ int exec_module(FAR const struct binary_s *binp)
     {
       bdbg("ERROR: up_addrenv_select() failed: %d\n", ret);
       err = -ret;
-      goto errout_with_stack;
+      goto errout_with_tcbinit;
     }
 #endif
 
   return (int)pid;
 
-errout_with_stack:
+errout_with_tcbinit:
   tcb->cmn.stack_alloc_ptr = NULL;
   sched_releasetcb(&tcb->cmn, TCB_FLAG_TTYPE_TASK);
   kumm_free(stack);
   goto errout;
 
+errout_with_kstack:
+#if defined(CONFIG_ARCH_ADDRENV) && defined(CONFIG_BUILD_KERNEL)
+  (void)up_addrenv_kstackfree(tcb);
+
 errout_with_addrenv:
+#endif
 #if defined(CONFIG_ARCH_ADDRENV) && defined(CONFIG_BUILD_KERNEL)
   (void)up_addrenv_restore(&oldenv);
+
 errout_with_tcb:
 #endif
   kmm_free(tcb);
+
 errout:
   set_errno(err);
   bdbg("returning errno: %d\n", err);
diff --git a/include/nuttx/arch.h b/include/nuttx/arch.h
index d4b55d8412..aa65d33c92 100644
--- a/include/nuttx/arch.h
+++ b/include/nuttx/arch.h
@@ -1151,7 +1151,9 @@ int up_addrenv_ustackselect(FAR const struct tcb_s *tcb);
  *
  * Description:
  *   This function is called when a new thread is created to allocate
- *   the new thread's kernel stack.
+ *   the new thread's kernel stack.   This function may be called for certain
+ *   terminating threads which have no kernel stack.  It must be tolerant of
+ *   that case.
  *
  * Input Parameters:
  *   tcb - The TCB of the thread that requires the kernel stack.
@@ -1164,7 +1166,7 @@ int up_addrenv_ustackselect(FAR const struct tcb_s *tcb);
  ****************************************************************************/
 
 #if defined(CONFIG_ARCH_ADDRENV) && defined(CONFIG_ARCH_KERNEL_STACK)
-int up_addrenv_kstackalloc(FAR struct tcb_s *tcb, size_t stacksize);
+int up_addrenv_kstackalloc(FAR struct tcb_s *tcb);
 #endif
 
 /****************************************************************************
diff --git a/sched/sched/sched_releasetcb.c b/sched/sched/sched_releasetcb.c
index f731a24421..ea44600167 100644
--- a/sched/sched/sched_releasetcb.c
+++ b/sched/sched/sched_releasetcb.c
@@ -114,13 +114,13 @@ int sched_releasetcb(FAR struct tcb_s *tcb, uint8_t ttype)
 
   if (tcb)
     {
-      /* Relase any timers that the task might hold.  We do this
+#ifndef CONFIG_DISABLE_POSIX_TIMERS
+      /* Release any timers that the task might hold.  We do this
        * before release the PID because it may still be trying to
        * deliver signals (although interrupts are should be
        * disabled here).
        */
 
-#ifndef CONFIG_DISABLE_POSIX_TIMERS
 #ifdef CONFIG_HAVE_WEAKFUNCTIONS
      if (timer_deleteall != NULL)
 #endif
@@ -147,9 +147,9 @@ int sched_releasetcb(FAR struct tcb_s *tcb, uint8_t ttype)
           up_release_stack(tcb, ttype);
         }
 
+#ifdef CONFIG_PIC
       /* Delete the task's allocated DSpace region (external modules only) */
 
-#ifdef CONFIG_PIC
       if (tcb->dspace)
         {
           if (tcb->dspace->crefs <= 1)
@@ -163,6 +163,12 @@ int sched_releasetcb(FAR struct tcb_s *tcb, uint8_t ttype)
         }
 #endif
 
+#if defined(CONFIG_ARCH_ADDRENV) && defined(CONFIG_ARCH_KERNEL_STACK)
+      /* Release the kernel stack */
+
+      (void)up_addrenv_kstackfree(tcb);
+#endif
+
       /* Release this thread's reference to the address environment */
 
 #ifdef CONFIG_ARCH_ADDRENV