s390: correct _stext offset

Avoid unnecessary rewrite of psw and merge _stext into
startup_continue. This allows to move _stext definition to vmlinux.lds.S,
where _etext is also defined and set _stext to the actual beginning of
.text at 0x100000.

This fixes the problem with setting the last .text page as
not-executable due to vmem_map_init relying on page alinged _stext and
_etext.

Fixes: bd79d66329 ("s390/decompressor: trim the kernel image up to 1M")
Reported-by: Nils Hoppmann <niho@de.ibm.com>
Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/kernel/head64.S

@@ -48,11 +48,23 @@ ENTRY(startup_continue)
 # Early machine initialization and detection functions.
 #
 	brasl	%r14,startup_init
-	lpswe	.Lentry-.LPG1(13)	# jump to _stext in primary-space,
-					# virtual and never return ...
+
+# check control registers
+	stctg	%c0,%c15,0(%r15)
+	oi	6(%r15),0x60		# enable sigp emergency & external call
+	oi	4(%r15),0x10		# switch on low address proctection
+	lctlg	%c0,%c15,0(%r15)
+
+	lam	0,15,.Laregs-.LPG1(%r13)	# load acrs needed by uaccess
+	brasl	%r14,start_kernel		# go to C code
+#
+# We returned from start_kernel ?!? PANIK
+#
+	basr	%r13,0
+	lpswe	.Ldw-.(%r13)		# load disabled wait psw
+
 	.align	16
 .LPG1:
-.Lentry:.quad	0x0000000180000000,_stext
 .Lctl:	.quad	0x04040000		# cr0: AFP registers & secondary space
 	.quad	0			# cr1: primary space segment table
 	.quad	.Lduct			# cr2: dispatchable unit control table
@@ -85,27 +97,5 @@ ENTRY(startup_continue)
 	.endr
 .Llinkage_stack:
 	.long	0,0,0x89000000,0,0,0,0x8a000000,0
-
-#
-# startup-code, running in absolute addressing mode
-#
-ENTRY(_stext)
-	basr	%r13,0			# get base
-.LPG3:
-# check control registers
-	stctg	%c0,%c15,0(%r15)
-	oi	6(%r15),0x60		# enable sigp emergency & external call
-	oi	4(%r15),0x10		# switch on low address proctection
-	lctlg	%c0,%c15,0(%r15)
-
-	lam	0,15,.Laregs-.LPG3(%r13)	# load acrs needed by uaccess
-	brasl	%r14,start_kernel	# go to C code
-#
-# We returned from start_kernel ?!? PANIK
-#
-	basr	%r13,0
-	lpswe	.Ldw-.(%r13)		# load disabled wait psw
-
-	.align	8
 .Ldw:	.quad	0x0002000180000000,0x0000000000000000
 .Laregs:.long	0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0

arch/s390/kernel/vmlinux.lds.S

@@ -31,6 +31,7 @@ PHDRS {
 SECTIONS
 {
 	. = 0x100000;
+	_stext = .;		/* Start of text section */
 	.text : {
 		/* Text and read-only data */
 		HEAD_TEXT