From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 13283 invoked by alias); 29 Nov 2010 08:55:41 -0000 Received: (qmail 13271 invoked by uid 22791); 29 Nov 2010 08:55:40 -0000 X-SWARE-Spam-Status: No, hits=-1.5 required=5.0 tests=AWL,BAYES_00,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FROM,RCVD_IN_DNSWL_NONE,TW_CL,TW_KG,TW_RW,TW_WX,T_FRT_BELOW2 X-Spam-Check-By: sourceware.org Received: from mail-yw0-f41.google.com (HELO mail-yw0-f41.google.com) (209.85.213.41) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Mon, 29 Nov 2010 08:55:35 +0000 Received: by ywa8 with SMTP id 8so6607483ywa.0 for ; Mon, 29 Nov 2010 00:55:34 -0800 (PST) Received: by 10.151.46.14 with SMTP id y14mr9780577ybj.383.1291020933894; Mon, 29 Nov 2010 00:55:33 -0800 (PST) Received: from [192.168.1.239] ([202.201.14.141]) by mx.google.com with ESMTPS id k16sm3167975ybe.12.2010.11.29.00.55.30 (version=SSLv3 cipher=RC4-MD5); Mon, 29 Nov 2010 00:55:33 -0800 (PST) Subject: Re: [hellogcc] Re: [PATCH] Built kernel without -O2 option From: Steven To: Hui Zhu Cc: hellogcc@freelists.org, =?ISO-8859-1?Q?Am=E9rico?= Wang , linux-kernel@vger.kernel.org, gdb@sourceware.org In-Reply-To: References: <20101129081619.GD5218@cr0.nay.redhat.com> <4CF36741.9000808@loongson.cn> Content-Type: text/plain; charset="UTF-8" Date: Mon, 29 Nov 2010 08:55:00 -0000 Message-ID: <1291020929.1817.11.camel@steven> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit X-IsSubscribed: yes Mailing-List: contact gdb-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-owner@sourceware.org X-SW-Source: 2010-11/txt/msg00110.txt.bz2 I replace -O2 with -O0 in Makefile of kernel source code root directory? I just do it and my gdb works well with this method. You mean it is not enough? Steven On Mon, 2010-11-29 at 16:47 +0800, Hui Zhu wrote: > In this way, you will got a lot of error. > > Hui > > On Mon, Nov 29, 2010 at 16:41, 乔崇 wrote: > > does not need change kernel,just write a shell mycc as bellow: > > > > #!/bin/sh > > gcc "$@" -O0 > > > > then > > > > make CC=./mycc vmlinux > > > > Hui Zhu said > > > > On Mon, Nov 29, 2010 at 16:16, Américo Wang > > wrote: > > > > > > On Mon, Nov 29, 2010 at 11:56:15AM +0800, Hui Zhu wrote: > > > > > > Hi, > > > > Now, there are a lot of ways to debug the Linux kernel with GDB, like > > qemu, kgtp or kgdb and so on. > > But the developer more like add a printk. It have a lot of reason, a big one > > is: > > (gdb) p ret > > $3 = > > And the code execution order is not right. > > > > This is becuase the Kernel is bult with gcc -O2. Gcc will not > > generate enough debug message with file with -O2. > > So GDB cannot work very well with Linux kernel. > > > > So I make a patch that add a option in "Kernel hacking" called "Close > > GCC optimization". It will make kernel be built without -O2. > > > > I built and use it in i386 and x86_64. I will try to make it OK in other > > arch. > > > > > > > > The problem is that some functions _have to_ be inlined and gcc without -O2 > > doesn't inline them. Have check all the cases? I doubt. > > > > > > If they really need O2, I set them to O2. > > Actually, this is the main work, find out the file that need the O2. :) > > > > For example: > > ifdef CONFIG_CC_CLOSE_OPTIMIZATION > > CFLAGS_fpu.o += -O2 > > CFLAGS_aesni-intel_glue.o += -O2 > > CFLAGS_ghash-clmulni-intel_glue.o += -O2 > > endif > > > > And I will try to find more of these type files. > > > > > > > > Also, what is size of vmlinux before applying your patch and after that? > > Does it increase too much? > > > > > > > > Before the patch: > > ls -alh vmlinuz-2.6.37-rc3+ > > -rw-r--r-- 1 root root 4.1M 2010-11-25 12:02 vmlinuz-2.6.37-rc3+ > > ls -alh b26no/vmlinux > > -rwxr-xr-x 1 teawater teawater 135M 2010-11-25 13:31 b26no/vmlinux > > > > After the patch: > > ls -alh vmlinuz-2.6.37-rc3debug+ > > -rw-r--r-- 1 root root 4.6M 2010-11-25 14:02 vmlinuz-2.6.37-rc3debug+ > > ls -alh b26/vmlinux > > -rwxr-xr-x 1 teawater teawater 140M 2010-11-25 11:14 b26/vmlinux > > > > Thanks, > > Hui > > > > > > > > > > -- > > > > 乔崇 qiaochong@loongson.cn > > > > 2010年 11月 29日 星期一 16:35:38 CST