[PATCH] kexec: x86_64: add CONFIG_PHYSICAL_START

For one kernel to report a crash another kernel has created we need
to have 2 kernels loaded simultaneously in memory.  To accomplish this
the two kernels need to built to run at different physical addresses.

This patch adds the CONFIG_PHYSICAL_START option to the x86_64 kernel
so we can do just that.  You need to know what you are doing and
the ramifications are before changing this value, and most users
won't care so I have made it depend on CONFIG_EMBEDDED

bzImage kernels will work and run at a different address when compiled
with this option but they will still load at 1MB.  If you need a kernel
loaded at a different address as well you need to boot a vmlinux.

Signed-off-by: Eric Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 11 insertions, 0 deletions

diff --git a/arch/x86_64/Kconfig b/arch/x86_64/Kconfig
index a853d87ff7e3..56c02cf6397d 100644
--- a/arch/x86_64/Kconfig
+++ b/arch/x86_64/Kconfig
@@ -369,6 +369,17 @@ config X86_MCE_INTEL
 	   Additional support for intel specific MCE features such as
 	   the thermal monitor.
 
+config PHYSICAL_START
+	hex "Physical address where the kernel is loaded" if EMBEDDED
+	default "0x100000"
+	help
+	  This gives the physical address where the kernel is loaded.
+	  Primarily used in the case of kexec on panic where the
+	  fail safe kernel needs to run at a different address than
+	  the panic-ed kernel.
+
+	  Don't change this unless you know what you are doing.
+
 config SECCOMP
 	bool "Enable seccomp to safely compute untrusted bytecode"
 	depends on PROC_FS