Re: [hellogcc] Re: [PATCH] Built kernel without -O2 option

[bekars <bekars@gmail.com>]

我实验的是
>>> #!/bin/sh
>>> gcc "$@" -O0 ||
>>>  gcc "$@" -O1 ||
>>>  gcc "$@"
>>>
>>>
>>>>> then
>>>>>
>>>>> make CC=./mycc vmlinux

这个方法，感觉简单些，但是编译不过，你的patch我明天试试。

我要调试网络系统，于是修改了net/Makefile，加上KBUILD_CFLAGS  +=
-O0，编译之后能启动内核，但是一有网络通信就panic了，内核顶层的Makefile我用的是-O1优化选项

请问是不是一部分用-O0，一部分用-O2或-O1，编译出来的内核会不稳定？


在 2010年12月1日 下午9:24，Hui Zhu <teawater@gmail.com> 写道：
> 2.6.35.4 is a little old.
>
> What I try is 2.6.37-rc3+ and 2.6.37-rc4+ amd64 and i386.
>
> Thanks,
> Hui
>
> 2010/12/1 bekars <bekars@gmail.com>:
>> 这个好像不行，我在2.6.35.4内核上编译，报错：
>>
>>  ./mm.sh -Wp,-MD,arch/x86/kernel/.entry_32.o.d  -nostdinc -isystem
>> /usr/lib/gcc/i486-linux-gnu/4.3.2/include
>> -I/home/baiyu/Melon/RSW3/base_system/linux.DEV/LKGDB/arch/x86/include
>> -Iinclude  -include include/generated/autoconf.h -D__KERNEL__
>> -D__ASSEMBLY__ -m32 -DCONFIG_AS_CFI=1 -DCONFIG_AS_CFI_SIGNAL_FRAME=1
>> -DCONFIG_AS_CFI_SECTIONS=1  -gdwarf-2        -c -o
>> arch/x86/kernel/entry_32.o arch/x86/kernel/entry_32.S
>> /home/baiyu/Melon/RSW3/base_system/linux.DEV/LKGDB/arch/x86/include/asm/dwarf2.h:
>> Assembler messages:
>> /home/baiyu/Melon/RSW3/base_system/linux.DEV/LKGDB/arch/x86/include/asm/dwarf2.h:46:
>> Error: unknown pseudo-op: `.cfi_sections'
>> /home/baiyu/Melon/RSW3/base_system/linux.DEV/LKGDB/arch/x86/include/asm/dwarf2.h:
>> Assembler messages:
>> /home/baiyu/Melon/RSW3/base_system/linux.DEV/LKGDB/arch/x86/include/asm/dwarf2.h:46:
>> Error: unknown pseudo-op: `.cfi_sections'
>> /home/baiyu/Melon/RSW3/base_system/linux.DEV/LKGDB/arch/x86/include/asm/dwarf2.h:
>> Assembler messages:
>> /home/baiyu/Melon/RSW3/base_system/linux.DEV/LKGDB/arch/x86/include/asm/dwarf2.h:46:
>> Error: unknown pseudo-op: `.cfi_sections'
>> make[2]: *** [arch/x86/kernel/entry_32.o] Error 1
>> make[1]: *** [arch/x86/kernel] Error 2
>> make: *** [arch/x86] Error 2
>>
>>
>>
>> 在 2010年11月29日 下午5:45，乔崇 <qiaochong@loongson.cn> 写道：
>>> 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@loongson.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@gmail.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@loongson.cn
>>>>>
>>>>> 2010年 11月 29日 星期一 16:35:38 CST
>>>>>
>>>>
>>>>
>>>>
>>>
>>>
>>> --
>>>
>>> 乔崇 qiaochong@loongson.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
>>>
>>>
>>
>>
>
>