From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 15442 invoked by alias); 29 Nov 2010 08:58:30 -0000 Received: (qmail 15431 invoked by uid 22791); 29 Nov 2010 08:58:29 -0000 X-SWARE-Spam-Status: No, hits=-0.4 required=5.0 tests=AWL,BAYES_00,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FROM,MIME_CHARSET_FARAWAY,RCVD_IN_DNSWL_NONE,TW_CL,TW_KG,TW_RW,TW_WX,T_FRT_BELOW2 X-Spam-Check-By: sourceware.org Received: from mail-ww0-f43.google.com (HELO mail-ww0-f43.google.com) (74.125.82.43) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Mon, 29 Nov 2010 08:58:21 +0000 Received: by wwi17 with SMTP id 17so1085541wwi.12 for ; Mon, 29 Nov 2010 00:58:19 -0800 (PST) Received: by 10.216.241.74 with SMTP id f52mr4349199wer.112.1291021098949; Mon, 29 Nov 2010 00:58:18 -0800 (PST) MIME-Version: 1.0 Received: by 10.216.186.148 with HTTP; Mon, 29 Nov 2010 00:57:58 -0800 (PST) In-Reply-To: <1291020929.1817.11.camel@steven> References: <20101129081619.GD5218@cr0.nay.redhat.com> <4CF36741.9000808@loongson.cn> <1291020929.1817.11.camel@steven> From: Hui Zhu Date: Mon, 29 Nov 2010 08:58:00 -0000 Message-ID: Subject: Re: [hellogcc] Re: [PATCH] Built kernel without -O2 option To: Steven Cc: hellogcc@freelists.org, =?ISO-8859-1?Q?Am=E9rico_Wang?= , linux-kernel@vger.kernel.org, gdb@sourceware.org Content-Type: text/plain; charset=GB2312 Content-Transfer-Encoding: quoted-printable 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/msg00111.txt.bz2 On Mon, Nov 29, 2010 at 16:55, Steven wrote: > 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 Yes. > > 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, =C7=C7=B3=E7 wrot= e: >> > does not need change kernel,just write a shell mycc as bellow: >> > >> > #!/bin/sh >> > gcc "$@" -O0 >> > >> > then >> > >> > make CC=3D./mycc vmlinux >> > >> > Hui Zhu said >> > >> > On Mon, Nov 29, 2010 at 16:16, Am=A8=A6rico 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 b= ig one >> > is: >> > (gdb) p ret >> > $3 =3D >> > 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 ot= her >> > arch. >> > >> > >> > >> > The problem is that some functions _have to_ be inlined and gcc withou= t -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 +=3D -O2 >> > CFLAGS_aesni-intel_glue.o +=3D -O2 >> > CFLAGS_ghash-clmulni-intel_glue.o +=3D -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 tha= t? >> > 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 >> > >> > >> > >> > >> > -- >> > >> > =C7=C7=B3=E7 qiaochong@loongson.cn >> > >> > 2010=C4=EA 11=D4=C2 29=C8=D5 =D0=C7=C6=DA=D2=BB 16:35:38 CST > >