[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>

Documentation/kernel-parameters.txt

@@ -475,10 +475,11 @@ running once the system is up.
 			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"}

arch/i386/kernel/setup.c

@@ -898,7 +898,7 @@ static void __init parse_cmdline_early (char ** cmdline_p)
 			}
 		}
 #endif
-#ifdef CONFIG_CRASH_DUMP
+#ifdef CONFIG_PROC_VMCORE
 		/* elfcorehdr= specifies the location of elf core header
 		 * stored by the crashed kernel.
 		 */

arch/x86_64/kernel/setup.c

@@ -35,6 +35,7 @@
 #include <asm/processor.h>
 #include <linux/console.h>
 #include <linux/seq_file.h>
+#include <linux/crash_dump.h>
 #include <linux/root_dev.h>
 #include <linux/pci.h>
 #include <linux/acpi.h>
@@ -418,6 +419,14 @@ static __init void parse_cmdline_early (char ** cmdline_p)
 		}
 #endif
 
+#ifdef CONFIG_PROC_VMCORE
+		/* elfcorehdr= specifies the location of elf core header
+		 * stored by the crashed kernel. This option will be passed
+		 * by kexec loader to the capture kernel.
+		 */
+		else if(!memcmp(from, "elfcorehdr=", 11))
+			elfcorehdr_addr = memparse(from+11, &from);
+#endif
 	next_char:
 		c = *(from++);
 		if (!c)