From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752993Ab3EMFPB (ORCPT ); Mon, 13 May 2013 01:15:01 -0400 Received: from mail-pa0-f50.google.com ([209.85.220.50]:35134 "EHLO mail-pa0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750763Ab3EMFO7 (ORCPT ); Mon, 13 May 2013 01:14:59 -0400 From: Joe Damato To: x86@kernel.org, linux-kernel@vger.kernel.org Cc: mingo@redhat.com, hpa@zytor.com, akpm@linux-foundation.org, Joe Damato Subject: [PATCH] x86: Reduce duplicated code in the x86_64 context switch path. Date: Sun, 12 May 2013 22:14:51 -0700 Message-Id: <1368422091-959-1-git-send-email-ice799@gmail.com> X-Mailer: git-send-email 1.7.9.5 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Signed-off-by: Joe Damato --- arch/x86/include/asm/switch_to.h | 30 ++++++++++++++++++++++++++++++ arch/x86/kernel/process_64.c | 29 ++--------------------------- 2 files changed, 32 insertions(+), 27 deletions(-) diff --git a/arch/x86/include/asm/switch_to.h b/arch/x86/include/asm/switch_to.h index 4ec45b3..a322cc6 100644 --- a/arch/x86/include/asm/switch_to.h +++ b/arch/x86/include/asm/switch_to.h @@ -124,6 +124,36 @@ do { \ __switch_canary_iparam \ : "memory", "cc" __EXTRA_CLOBBER) +#define loadsegment_fs(fs, index) \ + loadsegment(fs, index) + +#define loadsegment_gs(gs, index) \ + load_gs_index(index) + +#define switch_segment(prev, next, index, seg, msr) \ + do { \ + /* \ + * Segment register != 0 always requires a reload. Also \ + * reload when it has changed. When prev process used 64bit \ + * base always reload to avoid an information leak. \ + */ \ + if (unlikely(index | next->index | prev->seg)) { \ + loadsegment_##seg(seg, next->index); \ + /* \ + * Check if the user used a selector != 0; if yes \ + * clear 64bit base, since overloaded base is always \ + * mapped to the Null selector \ + */ \ + if (index) \ + prev->seg = 0; \ + } \ + \ + /* when next process has a 64bit base use it */ \ + if (next->seg) \ + wrmsrl(msr, next->seg); \ + prev->index = index; \ + } while (0) + #endif /* CONFIG_X86_32 */ #endif /* _ASM_X86_SWITCH_TO_H */ diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c index 355ae06..f41d026 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -318,34 +318,9 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p) /* * Switch FS and GS. - * - * Segment register != 0 always requires a reload. Also - * reload when it has changed. When prev process used 64bit - * base always reload to avoid an information leak. */ - if (unlikely(fsindex | next->fsindex | prev->fs)) { - loadsegment(fs, next->fsindex); - /* - * Check if the user used a selector != 0; if yes - * clear 64bit base, since overloaded base is always - * mapped to the Null selector - */ - if (fsindex) - prev->fs = 0; - } - /* when next process has a 64bit base use it */ - if (next->fs) - wrmsrl(MSR_FS_BASE, next->fs); - prev->fsindex = fsindex; - - if (unlikely(gsindex | next->gsindex | prev->gs)) { - load_gs_index(next->gsindex); - if (gsindex) - prev->gs = 0; - } - if (next->gs) - wrmsrl(MSR_KERNEL_GS_BASE, next->gs); - prev->gsindex = gsindex; + switch_segment(prev, next, fsindex, fs, MSR_FS_BASE); + switch_segment(prev, next, gsindex, gs, MSR_KERNEL_GS_BASE); switch_fpu_finish(next_p, fpu); -- 1.7.9.5