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Date: Mon, 29 Nov 2010 17:45:15 +0800 From: 乔崇 <qiaochong@...ngson.cn> To: hellogcc@...elists.org CC: Américo Wang <xiyou.wangcong@...il.com>, linux-kernel@...r.kernel.org, gdb@...rceware.org Subject: Re: [hellogcc] Re: [PATCH] Built kernel without -O2 option Hui Zhu 写道: > In this way, you will got a lot of error. > > Hui > > On Mon, Nov 29, 2010 at 16:41, 乔崇 <qiaochong@...ngson.cn> wrote: > >> does not need change kernel,just write a shell mycc as bellow: >> >> #!/bin/sh >> gcc "$@" -O0 >> >> change mycc to this will work,:) #!/bin/sh gcc "$@" -O0 || gcc "$@" -O1 || gcc "$@" >> then >> >> make CC=./mycc vmlinux >> >> Hui Zhu said >> >> On Mon, Nov 29, 2010 at 16:16, Américo Wang <xiyou.wangcong@...il.com> >> 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 = <value optimized out> >> 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@...ngson.cn >> >> 2010年 11月 29日 星期一 16:35:38 CST >> > > > -- 乔崇 qiaochong@...ngson.cn 龙芯中科技术服务中心有限公司 office:010-62600855-615 mobile:13521990614 2010年 11月 29日 星期一 17:38:14 CST -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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