1 files changed, 37 insertions, 1 deletions

diff --git a/arch/x86/kernel/acpi/realmode/wakeup.S b/arch/x86/kernel/acpi/realmode/wakeup.S
index f9b77fb37e5b..3355973b12ac 100644
--- a/arch/x86/kernel/acpi/realmode/wakeup.S
+++ b/arch/x86/kernel/acpi/realmode/wakeup.S
@@ -5,6 +5,7 @@
 #include <asm/msr-index.h>
 #include <asm/page.h>
 #include <asm/pgtable.h>
+#include <asm/processor-flags.h>
 
         .code16
         .section ".header", "a"
@@ -24,6 +25,11 @@ pmode_gdt:	.quad	0
 realmode_flags: .long   0
 real_magic:     .long   0
 trampoline_segment:     .word 0
+_pad1:          .byte   0
+wakeup_jmp:     .byte   0xea    /* ljmpw */
+wakeup_jmp_off: .word   3f
+wakeup_jmp_seg: .word   0
+wakeup_gdt:     .quad   0, 0, 0
 signature:      .long   0x51ee1111
 
         .text
@@ -34,11 +40,34 @@ _start:
         cli
         cld
 
+        /* Apparently some dimwit BIOS programmers don't know how to
+           program a PM to RM transition, and we might end up here with
+           junk in the data segment descriptor registers.  The only way
+           to repair that is to go into PM and fix it ourselves... */
+        movw    $16, %cx
+        lgdtl   %cs:wakeup_gdt
+        movl    %cr0, %eax
+        orb     $X86_CR0_PE, %al
+        movl    %eax, %cr0
+        jmp     1f
+1:      ljmpw   $8, $2f
+2:
+        movw    %cx, %ds
+        movw    %cx, %es
+        movw    %cx, %ss
+        movw    %cx, %fs
+        movw    %cx, %gs
+
+        andb    $~X86_CR0_PE, %al
+        movl    %eax, %cr0
+        jmp     wakeup_jmp
+3:
         /* Set up segments */
         movw    %cs, %ax
         movw    %ax, %ds
         movw    %ax, %es
         movw    %ax, %ss
+        lidtl   wakeup_idt
 
         movl    $wakeup_stack_end, %esp
 
@@ -98,7 +127,14 @@ bogus_real_magic:
         jmp     1b
 
         .data
-        .balign 4
+        .balign 8
+
+        /* This is the standard real-mode IDT */
+wakeup_idt:
+        .word   0xffff          /* limit */
+        .long   0               /* address */
+        .word   0
+
         .globl  HEAP, heap_end
 HEAP:
         .long   wakeup_heap