[PATCH 04/22] x86/entry/vm86: Clean up saved_fs/gs

[tim.gardner at canonical.com]

From: Brian Gerst <brgerst at gmail.com>

BugLink: http://bugs.launchpad.net/bugs/1499089

There is no need to save FS and non-lazy GS outside the 32-bit
regs.  Lazy GS still needs to be saved because it wasn't saved
on syscall entry.  Save it in the gs slot of regs32, which is
present but unused.

Signed-off-by: Brian Gerst <brgerst at gmail.com>
Cc: Andy Lutomirski <luto at amacapital.net>
Cc: Denys Vlasenko <dvlasenk at redhat.com>
Cc: Linus Torvalds <torvalds at linux-foundation.org>
Cc: Peter Zijlstra <peterz at infradead.org>
Cc: Thomas Gleixner <tglx at linutronix.de>
Link: http://lkml.kernel.org/r/1437354550-25858-2-git-send-email-brgerst@gmail.com
Signed-off-by: Ingo Molnar <mingo at kernel.org>
(cherry picked from commit 0233606ce5cf12c1a0e27cb197066ea5bc2bb488)
Signed-off-by: Tim Gardner <tim.gardner at canonical.com>
---
 arch/x86/include/asm/processor.h | 2 --
 arch/x86/kernel/vm86_32.c        | 6 ++----
 2 files changed, 2 insertions(+), 6 deletions(-)

diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 944f178..310a71e 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -407,8 +407,6 @@ struct thread_struct {
 	unsigned long		v86flags;
 	unsigned long		v86mask;
 	unsigned long		saved_sp0;
-	unsigned int		saved_fs;
-	unsigned int		saved_gs;
 #endif
 	/* IO permissions: */
 	unsigned long		*io_bitmap_ptr;
diff --git a/arch/x86/kernel/vm86_32.c b/arch/x86/kernel/vm86_32.c
index fc9db6e..761a2f9 100644
--- a/arch/x86/kernel/vm86_32.c
+++ b/arch/x86/kernel/vm86_32.c
@@ -159,8 +159,7 @@ struct pt_regs *save_v86_state(struct kernel_vm86_regs *regs)
 
 	ret = KVM86->regs32;
 
-	ret->fs = current->thread.saved_fs;
-	set_user_gs(ret, current->thread.saved_gs);
+	lazy_load_gs(ret->gs);
 
 	return ret;
 }
@@ -315,8 +314,7 @@ static void do_sys_vm86(struct kernel_vm86_struct *info, struct task_struct *tsk
  */
 	info->regs32->ax = VM86_SIGNAL;
 	tsk->thread.saved_sp0 = tsk->thread.sp0;
-	tsk->thread.saved_fs = info->regs32->fs;
-	tsk->thread.saved_gs = get_user_gs(info->regs32);
+	lazy_save_gs(info->regs32->gs);
 
 	tss = &per_cpu(cpu_tss, get_cpu());
 	tsk->thread.sp0 = (unsigned long) &info->VM86_TSS_ESP0;
-- 
1.9.1