[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, 4 insertions, 3 deletions

diff --git a/arch/x86_64/boot/compressed/head.S b/arch/x86_64/boot/compressed/head.S
index 27264dbd575c..b0df2aeff5dc 100644
--- a/arch/x86_64/boot/compressed/head.S
+++ b/arch/x86_64/boot/compressed/head.S
@@ -28,6 +28,7 @@
 
 #include <linux/linkage.h>
 #include <asm/segment.h>
+#include <asm/page.h>
 
         .code32
         .globl startup_32
@@ -77,7 +78,7 @@ startup_32:
         jnz  3f
         addl $8,%esp
         xorl %ebx,%ebx
-        ljmp $(__KERNEL_CS), $0x100000
+        ljmp $(__KERNEL_CS), $__PHYSICAL_START
 
 /*
  * We come here, if we were loaded high.
@@ -103,7 +104,7 @@ startup_32:
         popl %ecx       # lcount
         popl %edx       # high_buffer_start
         popl %eax       # hcount
-        movl $0x100000,%edi
+        movl $__PHYSICAL_START,%edi
         cli             # make sure we don't get interrupted
         ljmp $(__KERNEL_CS), $0x1000 # and jump to the move routine
 
@@ -128,7 +129,7 @@ move_routine_start:
         movsl
         movl %ebx,%esi  # Restore setup pointer
         xorl %ebx,%ebx
-        ljmp $(__KERNEL_CS), $0x100000
+        ljmp $(__KERNEL_CS), $__PHYSICAL_START
 move_routine_end: