Define zero-page offset 0x1e4 as a scratch field, and use it

The relocatable kernel code needs a scratch field for the decompressor
to determine its own location.  It was using a location inside
struct screen_info; reserve a free location and document it as scratch
instead.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 3 insertions, 3 deletions

diff --git a/arch/x86_64/boot/compressed/head.S b/arch/x86_64/boot/compressed/head.S
index f9d5692a0106..1312bfaff306 100644
--- a/arch/x86_64/boot/compressed/head.S
+++ b/arch/x86_64/boot/compressed/head.S
@@ -46,10 +46,10 @@ startup_32:
  * at and where we were actually loaded at.  This can only be done
  * with a short local call on x86.  Nothing  else will tell us what
  * address we are running at.  The reserved chunk of the real-mode
- * data at 0x34-0x3f are used as the stack for this calculation.
- * Only 4 bytes are needed.
+ * data at 0x1e4 (defined as a scratch field) are used as the stack
+ * for this calculation. Only 4 bytes are needed.
  */
-        leal    0x40(%esi), %esp
+        leal    (0x1e4+4)(%esi), %esp
         call    1f
 1:      popl    %ebp
         subl    $1b, %ebp