[PATCH] Save fs/gs over vm86 mode switch

In vm86 mode we did not save/restore %gs [and %fs] properly, which
breaks new-style threading.

arch/i386/kernel/vm86.c

@@ -116,6 +116,8 @@ struct pt_regs * save_v86_state(struct kernel_vm86_regs * regs)
 	current->thread.esp0 = current->thread.saved_esp0;
 	load_esp0(tss, current->thread.esp0);
 	current->thread.saved_esp0 = 0;
+	loadsegment(fs, current->thread.saved_fs);
+	loadsegment(gs, current->thread.saved_gs);
 	ret = KVM86->regs32;
 	return ret;
 }
@@ -283,6 +285,9 @@ static void do_sys_vm86(struct kernel_vm86_struct *info, struct task_struct *tsk
  */
 	info->regs32->eax = 0;
 	tsk->thread.saved_esp0 = tsk->thread.esp0;
+	asm volatile("movl %%fs,%0":"=m" (tsk->thread.saved_fs));
+	asm volatile("movl %%gs,%0":"=m" (tsk->thread.saved_gs));
+
 	tss = init_tss + smp_processor_id();
 	tss->esp0 = tsk->thread.esp0 = (unsigned long) &info->VM86_TSS_ESP0;
 	disable_sysenter();

include/asm-i386/processor.h

@@ -387,6 +387,7 @@ struct thread_struct {
 	struct vm86_struct	* vm86_info;
 	unsigned long		screen_bitmap;
 	unsigned long		v86flags, v86mask, saved_esp0;
+	unsigned int		saved_fs, saved_gs;
 /* IO permissions */
 	unsigned long	*ts_io_bitmap;
 };