[PATCH] kdump: x86_64: add elfcorehdr command line option

- elfcorehdr= specifies the location of elf core header stored by the
  crashed kernel.  This command line option will be passed by the kexec-tools
  to capture kernel.

Changes in this version :

- Added more comments in kernel-parameters.txt and in code.

Signed-off-by: Murali M Chakravarthy <muralim@in.ibm.com>
Signed-off-by: Vivek Goyal <vgoyal@in.ibm.com>
Cc: Andi Kleen <ak@muc.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 12b7d93..dd0bfc2 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -475,10 +475,11 @@
 			See Documentation/block/as-iosched.txt and
 			Documentation/block/deadline-iosched.txt for details.
 
-	elfcorehdr=	[IA-32]
+	elfcorehdr=	[IA-32, X86_64]
 			Specifies physical address of start of kernel core
-			image elf header.
-			See Documentation/kdump.txt for details.
+			image elf header. Generally kexec loader will
+			pass this option to capture kernel.
+			See Documentation/kdump/kdump.txt for details.
 
 	enforcing	[SELINUX] Set initial enforcing status.
 			Format: {"0" | "1"}