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Diffstat (limited to 'drivers/lguest/switcher.S')
-rw-r--r--drivers/lguest/switcher.S15
1 files changed, 9 insertions, 6 deletions
diff --git a/drivers/lguest/switcher.S b/drivers/lguest/switcher.S
index d418179..7c9c230 100644
--- a/drivers/lguest/switcher.S
+++ b/drivers/lguest/switcher.S
@@ -47,6 +47,7 @@
// Down here in the depths of assembler code.
#include <linux/linkage.h>
#include <asm/asm-offsets.h>
+#include <asm/page.h>
#include "lg.h"
// We mark the start of the code to copy
@@ -182,13 +183,15 @@ ENTRY(switch_to_guest)
movl $(LGUEST_DS), %eax; \
movl %eax, %ds; \
/* So where are we? Which CPU, which struct? \
- * The stack is our clue: our TSS sets \
- * It at the end of "struct lguest_pages" \
- * And we then pushed and pushed and pushed Guest regs: \
- * Now stack points atop the "struct lguest_regs". \
- * Subtract that offset, and we find our struct. */ \
+ * The stack is our clue: our TSS starts \
+ * It at the end of "struct lguest_pages". \
+ * Or we may have stumbled while restoring \
+ * Our Guest segment regs while in switch_to_guest, \
+ * The fault pushed atop that part-unwound stack. \
+ * If we round the stack down to the page start \
+ * We're at the start of "struct lguest_pages". */ \
movl %esp, %eax; \
- subl $LGUEST_PAGES_regs, %eax; \
+ andl $(~(1 << PAGE_SHIFT - 1)), %eax; \
/* Save our trap number: the switch will obscure it \
* (The Guest regs are not mapped here in the Host) \
* %ebx holds it safe for deliver_to_host */ \
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