linux-kernel - [PATCH 1/7] x86/vm86: Clean up saved

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Message-Id: <1437047167-5634-2-git-send-email-brgerst@gmail.com>
Date:	Thu, 16 Jul 2015 07:46:01 -0400
From:	Brian Gerst <brgerst@...il.com>
To:	x86@...nel.org, linux-kernel@...r.kernel.org
Cc:	Ingo Molnar <mingo@...nel.org>, "H. Peter Anvin" <hpa@...or.com>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Andy Lutomirski <luto@...capital.net>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 1/7] x86/vm86: Clean up saved_fs/gs

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.

Signed-off-by: Brian Gerst <brgerst@...il.com>
---
 arch/x86/include/asm/processor.h | 3 ++-
 arch/x86/kernel/vm86_32.c        | 6 ++----
 2 files changed, 4 insertions(+), 5 deletions(-)

diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 43e6519..a4b5c6a 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -410,9 +410,10 @@ struct thread_struct {
 	unsigned long		v86flags;
 	unsigned long		v86mask;
 	unsigned long		saved_sp0;
-	unsigned int		saved_fs;
+#ifdef CONFIG_X86_32_LAZY_GS
 	unsigned int		saved_gs;
 #endif
+#endif
 	/* IO permissions: */
 	unsigned long		*io_bitmap_ptr;
 	unsigned long		iopl;
diff --git a/arch/x86/kernel/vm86_32.c b/arch/x86/kernel/vm86_32.c
index fc9db6e..75eab83 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(current->thread.saved_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(tsk->thread.saved_gs);
 
 	tss = &per_cpu(cpu_tss, get_cpu());
 	tsk->thread.sp0 = (unsigned long) &info->VM86_TSS_ESP0;
-- 
2.4.3

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