Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754036AbbFITEI (ORCPT ); Tue, 9 Jun 2015 15:04:08 -0400 Received: from mx1.redhat.com ([209.132.183.28]:32919 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751279AbbFITED (ORCPT ); Tue, 9 Jun 2015 15:04:03 -0400 Message-ID: <5577389F.4090301@redhat.com> Date: Tue, 09 Jun 2015 21:03:59 +0200 From: Denys Vlasenko User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.2.0 MIME-Version: 1.0 To: Andy Lutomirski CC: Ingo Molnar , Linus Torvalds , Steven Rostedt , Borislav Petkov , "H. Peter Anvin" , Oleg Nesterov , Frederic Weisbecker , Alexei Starovoitov , Will Drewry , Kees Cook , X86 ML , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH 4/5] x86/asm/entry/32: Replace RESTORE_RSI_RDI[_RDX] with open-coded 32-bit reads References: <1433876051-26604-1-git-send-email-dvlasenk@redhat.com> <1433876051-26604-4-git-send-email-dvlasenk@redhat.com> In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1216 Lines: 28 On 06/09/2015 09:01 PM, Andy Lutomirski wrote: > On Tue, Jun 9, 2015 at 11:54 AM, Denys Vlasenko wrote: >> This doesn't change much, but this uses shorter 32-bit insns: >> >> -48 8b 74 24 68 mov 0x68(%rsp),%rsi >> -48 8b 7c 24 70 mov 0x70(%rsp),%rdi >> -48 8b 54 24 60 mov 0x60(%rsp),%rdx >> +8b 74 24 68 mov 0x68(%rsp),%esi >> +8b 7c 24 70 mov 0x70(%rsp),%edi >> +8b 54 24 60 mov 0x60(%rsp),%edx >> >> Since these are the only uses of RESTORE_RSI_RDI[_RDX], drop these macros. >> > > It probably doesn't matter for these fast paths, but, for the full > slow path return, we really do need to restore the full pt_regs. > After all, the syscall we're returning from might be sigreturn. This is compat 32-bit syscall handling code. IIUC we do not restore high half of any registers for 32-bit tasks. Am I missing something? -- 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/