x86, realmode: Remove indirect jumps in trampoline_32 and wakeup_asm

Remove indirect jumps in trampoline_32.S and the 32-bit part of
wakeup_asm.S.  There exist systems which are known to do weird
things if an SMI comes in right after a mode switch, and the
safest way to deal with it is to always follow with a simple
absolute far jump.  In the 64-bit code we then to a register
indirect near jump; follow that pattern for the 32-bit code.

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Link: http://lkml.kernel.org/r/1336501366-28617-14-git-send-email-jarkko.sakkinen@intel.com

1 files changed, 5 insertions, 3 deletions

diff --git a/arch/x86/realmode/rm/wakeup/wakeup_asm.S b/arch/x86/realmode/rm/wakeup/wakeup_asm.S
index b61126cb599..4c5c5f2bfbe 100644
--- a/arch/x86/realmode/rm/wakeup/wakeup_asm.S
+++ b/arch/x86/realmode/rm/wakeup/wakeup_asm.S
@@ -124,9 +124,11 @@ wakeup_start:
         lgdtl   pmode_gdt
 
         /* This really couldn't... */
-        movl    pmode_cr0, %eax
-        movl    %eax, %cr0
-        ljmpl   *pmode_entry
+        movl    pmode_entry, %eax
+        movl    pmode_cr0, %ecx
+        movl    %ecx, %cr0
+        ljmpl   $__KERNEL_CS, $pa_startup_32
+        /* -> jmp *%eax in trampoline_32.S */
 #else
         jmp     trampoline_data
 #endif