Introduce guest mem offset, static link example launcher

In order to avoid problematic special linking of the Launcher, we give
the Host an offset: this means we can use any memory region in the
Launcher as Guest memory rather than insisting on mmap() at 0.

The result is quite pleasing: a number of casts are replaced with
simple additions.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

1 files changed, 3 insertions, 0 deletions

diff --git a/drivers/lguest/lg.h b/drivers/lguest/lg.h
index 399eab852ab5..54f2c2472bec 100644
--- a/drivers/lguest/lg.h
+++ b/drivers/lguest/lg.h
@@ -142,6 +142,9 @@ struct lguest
         struct mm_struct *mm;   /* == tsk->mm, but that becomes NULL on exit */
         u16 guestid;
         u32 pfn_limit;
+        /* This provides the offset to the base of guest-physical
+         * memory in the Launcher. */
+        void __user *mem_base;
         u32 page_offset;
         u32 cr2;
         int halted;