s390: make command line configurable

Allow to configure the command line to an arbitrary length, with a
default of 4096 bytes. Also remove COMMAND_LINE_SIZE from
include/uapi/asm/setup.h as this is dynamic now and doesn't tell
anything about the command line size limitations of a new kernel
that might be loaded.

Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

Author: svens-s390

arch/s390/Kconfig

@@ -438,6 +438,14 @@ endchoice
 config 64BIT
 	def_bool y
 
+config COMMAND_LINE_SIZE
+	int "Maximum size of kernel command line"
+	default 4096
+	range 896 1048576
+	help
+	  This allows you to specify the maximum length of the kernel command
+	  line.
+
 config COMPAT
 	def_bool y
 	prompt "Kernel support for 31 bit emulation"

arch/s390/include/asm/setup.h

@@ -12,6 +12,7 @@
 
 #define PARMAREA		0x10400
 
+#define COMMAND_LINE_SIZE CONFIG_COMMAND_LINE_SIZE
 /*
  * Machine features detected in early.c
  */

arch/s390/include/uapi/asm/setup.h

@@ -1,12 +1 @@
 /* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
-/*
- *  S390 version
- *    Copyright IBM Corp. 1999, 2010
- */
-
-#ifndef _UAPI_ASM_S390_SETUP_H
-#define _UAPI_ASM_S390_SETUP_H
-
-#define COMMAND_LINE_SIZE	4096
-
-#endif /* _UAPI_ASM_S390_SETUP_H */