[S390] Export vmcoreinfo note

This patch defines for s390 an ABI defined pointer to the vmcoreinfo note at
a well known address. With this patch tools are able to find this information
in dumps created by stand-alone or hypervisor dump tools.
Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/include/asm/lowcore.h

@@ -151,10 +151,11 @@ struct _lowcore {
 	 */
 	__u32	ipib;				/* 0x0e00 */
 	__u32	ipib_checksum;			/* 0x0e04 */
+	__u32	vmcore_info;			/* 0x0e08 */
 
 	/* 64 bit save area */
-	__u64	save_area_64;			/* 0x0e08 */
-	__u8	pad_0x0e10[0x0f00-0x0e10];	/* 0x0e10 */
+	__u64	save_area_64;			/* 0x0e0c */
+	__u8	pad_0x0e14[0x0f00-0x0e14];	/* 0x0e14 */
 
 	/* Extended facility list */
 	__u64	stfle_fac_list[32];		/* 0x0f00 */
@@ -290,10 +291,11 @@ struct _lowcore {
 	 */
 	__u64	ipib;				/* 0x0e00 */
 	__u32	ipib_checksum;			/* 0x0e08 */
+	__u64	vmcore_info;			/* 0x0e0c */
 
 	/* 64 bit save area */
-	__u64	save_area_64;			/* 0x0e0c */
-	__u8	pad_0x0e14[0x0f00-0x0e14];	/* 0x0e14 */
+	__u64	save_area_64;			/* 0x0e14 */
+	__u8	pad_0x0e1c[0x0f00-0x0e1c];	/* 0x0e1c */
 
 	/* Extended facility list */
 	__u64	stfle_fac_list[32];		/* 0x0f00 */

arch/s390/kernel/setup.c

@@ -558,6 +558,15 @@ static void __init setup_restart_psw(void)
 	copy_to_absolute_zero(&S390_lowcore.restart_psw, &psw, sizeof(psw));
 }
 
+static void __init setup_vmcoreinfo(void)
+{
+#ifdef CONFIG_KEXEC
+	unsigned long ptr = paddr_vmcoreinfo_note();
+
+	copy_to_absolute_zero(&S390_lowcore.vmcore_info, &ptr, sizeof(ptr));
+#endif
+}
+
 #ifdef CONFIG_CRASH_DUMP
 
 /*
@@ -1022,6 +1031,7 @@ setup_arch(char **cmdline_p)
 	reserve_crashkernel();
 	setup_memory();
 	setup_resources();
+	setup_vmcoreinfo();
 	setup_restart_psw();
 	setup_lowcore();