s390/ipl: make parameter area accessible via struct parmarea

Since commit 9a965ea95135 ("s390/kexec_file: Simplify parmarea
access") we have struct parmarea which describes the layout of the
kernel parameter area.

Make the kernel parameter area available as global variable parmarea
of type struct parmarea, which allows to easily access its members.
Signed-off-by: NHeiko Carstens <hca@linux.ibm.com>
Signed-off-by: NVasily Gorbik <gor@linux.ibm.com>

arch/s390/boot/head.S

@@ -401,6 +401,7 @@ SYM_CODE_END(startup_pgm_check_handler)
 # Must be keept in sync with struct parmarea in setup.h
 #
 	.org	PARMAREA
+SYM_DATA_START(parmarea)
 	.quad	0			# IPL_DEVICE
 	.quad	0			# INITRD_START
 	.quad	0			# INITRD_SIZE
@@ -411,6 +412,8 @@ SYM_CODE_END(startup_pgm_check_handler)
 	.org	COMMAND_LINE
 	.byte	"root=/dev/ram0 ro"
 	.byte	0
+	.org	PARMAREA+__PARMAREA_SIZE
+SYM_DATA_END(parmarea)
 
 	.org	EARLY_SCCB_OFFSET
 	.fill	4096

arch/s390/include/asm/setup.h

@@ -78,6 +78,8 @@ struct parmarea {
 	char command_line[ARCH_COMMAND_LINE_SIZE];	/* 0x10480 */
 };
 
+extern struct parmarea parmarea;
+
 extern unsigned int zlib_dfltcc_support;
 #define ZLIB_DFLTCC_DISABLED		0
 #define ZLIB_DFLTCC_FULL		1

arch/s390/kernel/asm-offsets.c

@@ -15,6 +15,7 @@
 #include <asm/idle.h>
 #include <asm/gmap.h>
 #include <asm/nmi.h>
+#include <asm/setup.h>
 #include <asm/stacktrace.h>
 
 int main(void)
@@ -155,5 +156,7 @@ int main(void)
 	OFFSET(__KEXEC_SHA_REGION_START, kexec_sha_region, start);
 	OFFSET(__KEXEC_SHA_REGION_LEN, kexec_sha_region, len);
 	DEFINE(__KEXEC_SHA_REGION_SIZE, sizeof(struct kexec_sha_region));
+	/* sizeof kernel parameter area */
+	DEFINE(__PARMAREA_SIZE, sizeof(struct parmarea));
 	return 0;
 }