diff options
Diffstat (limited to 'drivers/lguest/switcher.S')
| -rw-r--r-- | drivers/lguest/switcher.S | 15 |
1 files changed, 9 insertions, 6 deletions
diff --git a/drivers/lguest/switcher.S b/drivers/lguest/switcher.S index d418179ea6b5..7c9c230cc845 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 */ \ |