arc: add ECR (exception cause register) output

Exception cause register (ECR) contains value that describes a reason
for exception that has happened. This helps a lot to figure-out what
went wrong.

Now we print this register contents when dumping registers.

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
Signed-off-by: Igor Guryanov <guryanov@synopsys.com>

arch/arc/cpu/arc700/interrupts.c

@@ -61,6 +61,7 @@ static void print_reg_file(long *reg_rev, int start_num)
 
 void show_regs(struct pt_regs *regs)
 {
+	printf("ECR:\t0x%08lx\n", regs->ecr);
 	printf("RET:\t0x%08lx\nBLINK:\t0x%08lx\nSTAT32:\t0x%08lx\n",
 	       regs->ret, regs->blink, regs->status32);
 	printf("GP: 0x%08lx\t r25: 0x%08lx\t\n", regs->r26, regs->r25);

arch/arc/cpu/arc700/start.S

@@ -57,11 +57,13 @@
 .endm
 
 .macro SAVE_ALL_SYS
-
+	/* saving %r0 to reg->r0 in advance since we read %ecr into it */
+	st	%r0, [%sp, -8]
+	lr	%r0, [%ecr]	/* all stack addressing is manual so far */
 	st	%r0, [%sp]
-	lr	%r0, [%ecr]
-	st	%r0, [%sp, 8]	/* ECR */
-	st	%sp, [%sp, 4]
+	st	%sp, [%sp, -4]
+	/* now move %sp to reg->r0 position so we can do "push" automatically */
+	sub	%sp, %sp, 8
 
 	SAVE_R1_TO_R24
 	PUSH	%r25