[S390] fix boot failures with compressed kernels

Fix two bugs with the kernel image compression:
1) reset the bss section of the compressed vmlinux
2) clear the high half of the registers for 64 bit early enough
   for the decompression step

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/boot/compressed/misc.c

@@ -24,8 +24,8 @@
 /* Symbols defined by linker scripts */
 extern char input_data[];
 extern int input_len;
-extern int _text;
+extern char _text, _end;
-extern int _end;
+extern char _bss, _ebss;
 
 static void error(char *m);
 
@@ -129,12 +129,12 @@ unsigned long decompress_kernel(void)
 	unsigned long output_addr;
 	unsigned char *output;
 
+	check_ipl_parmblock((void *) 0, (unsigned long) output + SZ__bss_start);
+	memset(&_bss, 0, &_ebss - &_bss);
 	free_mem_ptr = (unsigned long)&_end;
 	free_mem_end_ptr = free_mem_ptr + HEAP_SIZE;
 	output = (unsigned char *) ((free_mem_end_ptr + 4095UL) & -4096UL);
 
-	check_ipl_parmblock((void *) 0, (unsigned long) output + SZ__bss_start);
-
 #ifdef CONFIG_BLK_DEV_INITRD
 	/*
 	 * Move the initrd right behind the end of the decompressed

arch/s390/kernel/head.S

@@ -517,7 +517,10 @@ startup:
 	lhi	%r1,2			# mode 2 = esame (dump)
 	sigp	%r1,%r0,0x12		# switch to esame mode
 	sam64				# switch to 64 bit mode
+	larl	%r13,4f
+	lmh	%r0,%r15,0(%r13)	# clear high-order half
 	jg	startup_continue
+4:	.fill	16,4,0x0
 #else
 	mvi	__LC_AR_MODE_ID,0	# set ESA flag (mode 0)
 	l	%r13,4f-.LPG0(%r13)

arch/s390/kernel/head64.S

@@ -21,7 +21,6 @@ startup_continue:
 	larl	%r1,sched_clock_base_cc
 	mvc	0(8,%r1),__LC_LAST_UPDATE_CLOCK
 	larl	%r13,.LPG1		# get base
-	lmh	%r0,%r15,.Lzero64-.LPG1(%r13)	# clear high-order half
 	lctlg	%c0,%c15,.Lctl-.LPG1(%r13)	# load control registers
 	lg	%r12,.Lparmaddr-.LPG1(%r13)	# pointer to parameter area
 					# move IPL device to lowcore
@@ -67,7 +66,6 @@ startup_continue:
 .L4malign:.quad 0xffffffffffc00000
 .Lscan2g:.quad	0x80000000 + 0x20000 - 8	# 2GB + 128K - 8
 .Lnop:	.long	0x07000700
-.Lzero64:.fill	16,4,0x0
 .Lparmaddr:
 	.quad	PARMAREA
 	.align	64