Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753224AbbGBMKD (ORCPT ); Thu, 2 Jul 2015 08:10:03 -0400 Received: from mail.skyhub.de ([78.46.96.112]:59814 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753362AbbGBMJz (ORCPT ); Thu, 2 Jul 2015 08:09:55 -0400 Date: Thu, 2 Jul 2015 14:09:32 +0200 From: Borislav Petkov To: Andy Lutomirski Cc: x86@kernel.org, linux-kernel@vger.kernel.org, =?utf-8?B?RnLDqWTDqXJpYw==?= Weisbecker , Rik van Riel , Oleg Nesterov , Denys Vlasenko , Kees Cook , Brian Gerst , paulmck@linux.vnet.ibm.com Subject: Re: [PATCH v4 14/17] x86/asm/entry/64: Migrate error and interrupt exit work to C Message-ID: <20150702120932.GH4001@pd.tnic> References: <1a5858d079609a3e293123c9ee45de433a4e9c44.1435602481.git.luto@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <1a5858d079609a3e293123c9ee45de433a4e9c44.1435602481.git.luto@kernel.org> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1937 Lines: 66 On Mon, Jun 29, 2015 at 12:33:46PM -0700, Andy Lutomirski wrote: > Signed-off-by: Andy Lutomirski > --- > arch/x86/entry/entry_64.S | 63 +++++++++++----------------------------- > arch/x86/entry/entry_64_compat.S | 5 ++++ > 2 files changed, 22 insertions(+), 46 deletions(-) > > diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S > index ce2c9049abef..08a37ec049f0 100644 > --- a/arch/x86/entry/entry_64.S > +++ b/arch/x86/entry/entry_64.S > @@ -508,7 +508,16 @@ END(irq_entries_start) > > testb $3, CS(%rsp) > jz 1f > + > + /* > + * IRQ from user mode. Switch to kernel gsbase and inform context > + * tracking that we're in kernel mode. > + */ > SWAPGS > +#ifdef CONFIG_CONTEXT_TRACKING > + call enter_from_user_mode > +#endif I think you can make this much cleaner by getting rid of the ifdeffery and pushing it into the enter_from_user_mode() function: __visible void enter_from_user_mode(void) { #ifdef CONFIG_CONTEXT_TRACKING ... #endif } The disadvantage of all that cleanliness is that we get one dumb call enter_from_user_mode there to this abomination: ffffffff810014f0 : ffffffff810014f0: e8 db 97 67 00 callq ffffffff8167acd0 <__fentry__> ffffffff810014f5: 55 push %rbp ffffffff810014f6: 48 89 e5 mov %rsp,%rbp ffffffff810014f9: 5d pop %rbp ffffffff810014fa: c3 retq ffffffff810014fb: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1) which sux. We sure could use LTO here. -- Regards/Gruss, Boris. ECO tip #101: Trim your mails when you reply. -- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/