arm, c5471: Refactor interrupt stack related code

Summary:
- Apply the same logic for armv7-a
- NOTE: stack pointer alignment is 4-byte

Impact:
- Affects arm (arm7/9) and c5471 with interrupt stack enabled

Testing:
- Built with c5471evm.nsh (CONFIG_ARCH_INTERRUPTSTACK=2048)
- Built with ea3131:nsh (CONFIG_ARCH_INTERRUPTSTACK=2048)
- Not tested but should work

Signed-off-by: Masayuki Ishikawa <Masayuki.Ishikawa@jp.sony.com>

arch/arm/src/arm/arm_assert.c

@@ -210,18 +210,12 @@ static void up_dumpstate(void)
    * stack?
    */
 
-  if (sp <= istackbase && sp > istackbase - istacksize)
+  if (sp < istackbase && sp > istackbase - istacksize)
     {
       /* Yes.. dump the interrupt stack */
 
+      _alert("Interrupt Stack\n", sp);
       up_stackdump(sp, istackbase);
-
-      /* Extract the user stack pointer which should lie
-       * at the base of the interrupt stack.
-       */
-
-      sp = g_intstackbase;
-      _alert("sp:     %08x\n", sp);
     }
   else if (CURRENT_REGS)
     {
@@ -229,6 +223,17 @@ static void up_dumpstate(void)
       up_stackdump(istackbase - istacksize, istackbase);
     }
 
+  /* Extract the user stack pointer if we are in an interrupt handler.
+   * If we are not in an interrupt handler.  Then sp is the user stack
+   * pointer (and the above range check should have failed).
+   */
+
+  if (CURRENT_REGS)
+    {
+      sp = CURRENT_REGS[REG_R13];
+      _alert("User sp: %08x\n", sp);
+    }
+
   /* Show user stack info */
 
   _alert("User stack:\n");

arch/arm/src/arm/arm_vectors.S

@@ -132,7 +132,7 @@ arm_vectorirq:
 
 #if CONFIG_ARCH_INTERRUPTSTACK > 3
 	ldr	sp, .Lirqstackbase	/* SP = interrupt stack base */
-	str	r0, [sp]		/* Save the user stack pointer */
+	str	r0, [sp, #-4]!		/* Save the xcp address at SP-4 then update SP */
 	bl	arm_decodeirq		/* Call the handler */
 	ldr	sp, [sp]		/* Restore the user stack pointer */
 #else
@@ -432,13 +432,13 @@ arm_vectorfiq:
 
 #if CONFIG_ARCH_INTERRUPTSTACK > 3
 	.bss
-	.align	4
+	.balign	4
 	.globl	g_intstackalloc
 	.type	g_intstackalloc, object
 	.globl	g_intstackbase
 	.type	g_intstackbase, object
 g_intstackalloc:
-	.skip	((CONFIG_ARCH_INTERRUPTSTACK & ~3) - 4)
+	.skip	(CONFIG_ARCH_INTERRUPTSTACK & ~3)
 g_intstackbase:
 	.skip	4
 	.size	g_intstackbase, 4

arch/arm/src/c5471/c5471_vectors.S

@@ -162,7 +162,7 @@ arm_vectorirq:
 
 #if CONFIG_ARCH_INTERRUPTSTACK > 3
 	ldr	sp, .Lirqstackbase	/* SP = interrupt stack base */
-	str	r1, [sp]		/* Save the user stack pointer */
+	str	r1, [sp, #-4]!		/* Save the xcp address at SP-4 then update SP */
 	bl	arm_doirq		/* Call the handler */
 	ldr	sp, [sp]		/* Restore the user stack pointer */
 #else
@@ -471,13 +471,13 @@ arm_vectoraddrexcptn:
 
 #if CONFIG_ARCH_INTERRUPTSTACK > 3
 	.bss
-	.align	4
+	.balign	4
 	.global	g_intstackalloc
 	.global	g_intstackbase
 	.type	g_intstackalloc, object
 	.type	g_intstackbase, object
 g_intstackalloc:
-	.skip	((CONFIG_ARCH_INTERRUPTSTACK & ~3) - 4)
+	.skip	(CONFIG_ARCH_INTERRUPTSTACK & ~3)
 g_intstackbase:
 	.skip	4
 	.size	g_intstackbase, 4