ARM: 8786/1: Debug kernel copy by printing

It may happen that when we relocate the kernel we corrupt other
sensible memory (e.g. the memory needed by U-Boot for dealing
with bootm command) while copying the kernel. If we overwrite
the content of the memory area used by U-Boot's command bootm
(described by U-Boot's parameters bootm_low and bootm_size),
the kernel won't be able to boot. Troubleshooting the problem
then is not straightforward.

This commit allows the user to easily print information on
where the kernel gets copied from/to in order to help with the
design of the system memory map (e.g. bootm_low and bootm_size)
at boot up.
Signed-off-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
Reviewed-by: Chris Paterson <Chris.Paterson2@renesas.com>
Acked-by: Biju Das <biju.das@bp.renesas.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>

arch/arm/boot/compressed/head.S

@@ -114,6 +114,35 @@
 #endif
 		.endm
 
+		/*
+		 * Debug kernel copy by printing the memory addresses involved
+		 */
+		.macro dbgkc, begin, end, cbegin, cend
+#ifdef DEBUG
+		kputc   #'\n'
+		kputc   #'C'
+		kputc   #':'
+		kputc   #'0'
+		kputc   #'x'
+		kphex   \begin, 8	/* Start of compressed kernel */
+		kputc	#'-'
+		kputc	#'0'
+		kputc	#'x'
+		kphex	\end, 8		/* End of compressed kernel */
+		kputc	#'-'
+		kputc	#'>'
+		kputc   #'0'
+		kputc   #'x'
+		kphex   \cbegin, 8	/* Start of kernel copy */
+		kputc	#'-'
+		kputc	#'0'
+		kputc	#'x'
+		kphex	\cend, 8	/* End of kernel copy */
+		kputc	#'\n'
+		kputc	#'\r'
+#endif
+		.endm
+
 		.section ".start", #alloc, #execinstr
 /*
  * sort out different calling conventions
@@ -450,6 +479,20 @@ dtb_check_done:
 		add	r6, r9, r5
 		add	r9, r9, r10
 
+#ifdef DEBUG
+		sub     r10, r6, r5
+		sub     r10, r9, r10
+		/*
+		 * We are about to copy the kernel to a new memory area.
+		 * The boundaries of the new memory area can be found in
+		 * r10 and r9, whilst r5 and r6 contain the boundaries
+		 * of the memory we are going to copy.
+		 * Calling dbgkc will help with the printing of this
+		 * information.
+		 */
+		dbgkc	r5, r6, r10, r9
+#endif
+
 1:		ldmdb	r6!, {r0 - r3, r10 - r12, lr}
 		cmp	r6, r5
 		stmdb	r9!, {r0 - r3, r10 - r12, lr}