From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755262AbdCGJHS (ORCPT ); Tue, 7 Mar 2017 04:07:18 -0500 Received: from mail-wr0-f194.google.com ([209.85.128.194]:35266 "EHLO mail-wr0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755135AbdCGJGn (ORCPT ); Tue, 7 Mar 2017 04:06:43 -0500 Date: Tue, 7 Mar 2017 10:06:38 +0100 From: Ingo Molnar To: Borislav Petkov Cc: X86 ML , LKML , Thomas Gleixner Subject: Re: [PATCH 1/2] x86/head_64.S: Rename start_cpu() Message-ID: <20170307090638.GC6946@gmail.com> References: <20170304095611.11355-1-bp@alien8.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170304095611.11355-1-bp@alien8.de> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Borislav Petkov wrote: > From: Borislav Petkov > > It doesn't really start a CPU but does a far jump to C code. So call it > that. Eliminate the unconditional JMP to it from secondary_startup_64() > but make the jump to C code piece part of secondary_startup_64() > instead. > > Also, it doesn't need to be a global symbol either so make it a local > label. One less needlessly global symbol in the symbol table. > > No functionality change. > > Signed-off-by: Borislav Petkov > --- > arch/x86/kernel/head_64.S | 10 ++++------ > 1 file changed, 4 insertions(+), 6 deletions(-) > > diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S > index b467b14b03eb..ac9d327d2e42 100644 > --- a/arch/x86/kernel/head_64.S > +++ b/arch/x86/kernel/head_64.S > @@ -269,10 +269,8 @@ ENTRY(secondary_startup_64) > /* rsi is pointer to real mode structure with interesting info. > pass it to C */ > movq %rsi, %rdi > - jmp start_cpu > -ENDPROC(secondary_startup_64) > > -ENTRY(start_cpu) > +.Ljump_to_C_code: > /* > * Jump to run C code and to be on a real kernel address. > * Since we are running on identity-mapped space we have to jump > @@ -305,7 +303,7 @@ ENTRY(start_cpu) > pushq %rax # target address in negative space > lretq > .Lafter_lret: > -ENDPROC(start_cpu) > +ENDPROC(secondary_startup_64) > > #include "verify_cpu.S" > > @@ -313,11 +311,11 @@ ENDPROC(start_cpu) > /* > * Boot CPU0 entry point. It's called from play_dead(). Everything has been set > * up already except stack. We just set up stack here. Then call > - * start_secondary() via start_cpu(). > + * start_secondary() via .Ljump_to_C_code. > */ > ENTRY(start_cpu0) > movq initial_stack(%rip), %rsp > - jmp start_cpu > + jmp .Ljump_to_C_code > ENDPROC(start_cpu0) > #endif Wouldn't this be slightly more readable: jmp .L_jump_to_C_code ? (Note the extra underscore in the symbol name) The local labels syntax is silly, I always end up looking twice to make sense of 'Ljump' or 'Lwhatever' ;-) We cannot do anything about that - but we can name our symbols to work it around. But the price is the extra underscore in the symbol name... Thanks, Ingo