From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 14804 invoked by alias); 29 Nov 2010 08:25:11 -0000 Received: (qmail 14766 invoked by uid 22791); 29 Nov 2010 08:25:10 -0000 X-SWARE-Spam-Status: No, hits=-1.6 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 X-Spam-Check-By: sourceware.org Received: from mail-wy0-f169.google.com (HELO mail-wy0-f169.google.com) (74.125.82.169) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Mon, 29 Nov 2010 08:25:05 +0000 Received: by wyb42 with SMTP id 42so12195969wyb.0 for ; Mon, 29 Nov 2010 00:25:03 -0800 (PST) Received: by 10.216.52.193 with SMTP id e43mr17077wec.82.1291019102388; Mon, 29 Nov 2010 00:25:02 -0800 (PST) MIME-Version: 1.0 Received: by 10.216.186.148 with HTTP; Mon, 29 Nov 2010 00:24:42 -0800 (PST) In-Reply-To: <20101129081619.GD5218@cr0.nay.redhat.com> References: <20101129081619.GD5218@cr0.nay.redhat.com> From: Hui Zhu Date: Mon, 29 Nov 2010 08:25:00 -0000 Message-ID: Subject: Re: [PATCH] Built kernel without -O2 option To: =?ISO-8859-1?Q?Am=E9rico_Wang?= Cc: linux-kernel@vger.kernel.org, gdb@sourceware.org, hellogcc@freelists.org Content-Type: text/plain; charset=ISO-8859-1 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/msg00107.txt.bz2 On Mon, Nov 29, 2010 at 16:16, Am=E9rico Wang wr= ote: > 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 =3D >>And the code execution order is not right. >> >>This is becuase the Kernel is bult with gcc -O2. =A0Gcc 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". =A0It will make kernel be built without -O2. >> >>I built and use it in i386 and x86_64. =A0I will try to make it OK in oth= er 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 +=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 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